Дисертації з теми "Amphibian peptides"
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1
Wegener, Kate Louise. "Amphibian peptides : their structures and bioactivity." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09phw4114.pdf.
Повний текст джерелаАнотація:
Copies of author's previously published works inserted. Bibliography: leaves 237-268. The skin secretion of the northern Australian frog Litoria dahlii was investigated, with eleven novel peptides identified. These peptides have moderate biological activity, including antibacterial and anticancer actions, as well as the capacity to inhibit the enzyme neuronal nitric oxide synthase. Many potent broad-spectrum antibiotics have been isolated from Australian amphibians, and are believed to act by disrupting the bacterial cell membrane by forming transmembrane 'barrel-stave' type ion channels, lipid-incorporating toroidal pores or by assembling as a 'carpet' over the mebrane surface. The structures of several antibacterial peptides were determined using nuclear magnetic resonance spectroscopy and restrained molecular dynamics calculations. Experimental results suggest these peptides operate by the 'carpet' mechanism.
2
Salmon, Amanda Lizabeth. "Structural and functional characterisation of bioactive amphibian skin peptides." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247347.
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3
Shi, Daning. "Functional studies on the peptides from amphibian skin secretions." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711901.
Повний текст джерелаАнотація:
Therapeutic peptides are continuing to grow in prominence among pharmaceutical manufacturers. Drugs based on peptides offer lower toxicity, show higher specificity, and demonstrate fewer toxicology issues than small molecule drugs. The specificity of peptides has tremendous clinical value and makes them very attractive and potentially lucrative therapeutics. In order to protect themselves from a great variety of potential predators, amphibians have evolved different morphological, physiological and behavioural features. One such defence mechanism is the secretion from granular skin glands. Frogs and toads have two different types of skin glands -mucous and granular. The mucous glands are present throughout the skin and their secretion provides a moist coating that is necessary for cutaneous respiration. The granular glands may be distributed across the body but are often concentrated around the head or neck and are usually activated by stress or injury. Secretions from these glands are complex, species-specific cocktails of bioactive molecules, including peptides. The Chinese have perhaps the most advanced and temporally tested system of natural therapies among traditional medicines and therapeutics have been derived from both plants and animals, including amphibians. This study focuses on the vast potential of natural peptide libraries contained in amphibian skin secretions as a source of novel drug candidates for conditions such as hypertension, cancer, and bacterial infection.
4
Wang, Ran. "Biological effects of novel amphibian skin peptides and their catabolism." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557850.
Повний текст джерелаАнотація:
Amphibian skin secretions are known to contain numerous peptides with a large array of biological activities. Among the anuran amphibians, the Neotropical hylid frogs belonging to the subfamily Phyllomedusinae, are an excellent source of such bioactive peptides with antimicrobial and pharmacological activities. To date, more than 200 peptides from this frog taxon have been reported in the scientific literature and their structures have been deposited in genomic and proteomic data banks such as the Universal Protein Resource Consortium (UniProt). In this thesis, we have identified four novel tryptophyllins (TPHs) from the skin secretions of four different phyllomedusine species (Phyllomedusa sauvagei, Phyllomedusa hypocondrialis, Agalyehnis eallidryas and Phyllomedusa bieolor). The primary structures of these peptides were determined by combinations of Edman degradation and mass spectrometry techniques. Molecular cloning of respective cDNA sequences encoding the precursors of these TPHs was achieved from skin cDNA libraries of each species. The amino acid sequences deduced from the nucleotide sequences of cloned precursor cDNAs corresponded exactly with those obtained by chemical/mass spectrometric techniques. Some of these novel TPH peptides were found to have potent effects on mammalian smooth muscle and here we report for the first time that TPHs can antagonise the bradykinin-induced relaxation responses in rat tail artery smooth muscle preparations and that they have anticancer effects on human prostate cancer (LNCaPIPC3IDU145) cell lines. The catabolism of these TPHs by prostate cancer cells was analysed and all were found to be highly-resistant to degradation under the experimental conditions employed. The polyadenylated mRNAs encoding both bradykinin receptor subtypes, Bland B2, were also shown to be expressed in all three prostate cancer cell lines through molecular cloning of specific receptor cDNA fragments from cDNA libraries constructed from each. These data suggest that bradykinin receptors could be a hitherto uninvestigated target of potential utility in the treatment of prostate cancer. The data generated through the discrete studies reported in this thesis may aid in the understanding of possible biological roles played by amphibian skin TPHs and the contributions made by specific structural features within this heterogenous and largely unstudied family of amphibian skin peptides. The peptides described here for the first time may represent novel lead compounds for the design/development of new therapeutics for human neoplastic disease.
5
Gao, Yitian. "Peptidomic and bioinformatic studies on bioactive peptides from amphibian skin secretions." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.726351.
Повний текст джерелаАнотація:
Phyllomedusa, as a significant genus of South American and Neotropical hylid frogs, has been researched for several years and this has produced abundant bioactive peptides. Most frog species have poisonous skin secretions that can act as a defence against potential predators and pathogens. Therefore, Phyllomedusa frogs have been referred to as a "treasure store” and compared to be the most promising drug sources. Antimicrobial peptides (AMPs), as the most widely isolated group of peptides from skin secretions of Phyllomedusa frogs, have been considered as a novel therapeutic approach to address the serious difficulties in treating antibiotic resistant infections. In addition to their direct antimicrobial activities, AMPs can regulate innate immune responses and can facilitate wound healing and angiogenesis. Phylloseptins are a family of potent AMPs that are widely distributed in the skin secretions of phyllomedusine frogs. The structures of these peptides are relatively conserved, containing 19-21 amino acids with C-terminal amidation, a cationic amphiphilic structure and an a-helical domain. Medusins are a recently discovered family of AMPs in the Phyllomedusinae, with highly-conserved sequences and relatively strong antimicrobial activity against Gram-positive bacteria and fungi, but without obvious cytotoxicity against eukaryotic cells at effective antibacterial concentrations. Dermaseptins are one of the most significant families of amphibian host defence peptides that are usually cationic, contain 10-50 amino acids and inhibit the growth of a wide range of microbes. Here, we report novel peptides from the skin secretion of the Phyllomedusa frogs,Phyllomedusa tarsius and Phyllomedusa sauvagii, identified using a high throughput method combining molecular cloning with mass spectrometry to establish their primary structures. A phylloseptin peptide, a medusin peptide and two dermaseptin peptide-precursor-encoding cDNAs were cloned from defensive skin secretion-derived cDNA libraries by a rapid amplification of cDNA ends technique. R6verse-phase HPLC and tandem mass spectrometry confirmed the presence and primary structure of mature peptide sequences. The secondary structure and physicochemical parameters of each peptide were predicted with using a predictive software system. Cationicity- and amphipathicity- enhanced analogues of the phylloseptin and medusin were by engineered through amino acid substitutions by computational modelling. The synthetic peptides displayed varying degrees of activities. Phylloseptin was active against Staphylococcus aureus and Candida albicans and medusin only against Staphylococcus aureus. However, cationicity-enhanced peptides displayed significant increases in potency and broader spectra of antimicrobial activities. In addition, the appearance of activity against antibiotic-resistant MRSA and biofilms was observed after modification of the structures. Both D-substituted analogues of phylloseptin and medusin showed potent antimicrobial activities as well as stable functional efficiency in the serum. Two dermaseptin peptides exhibited high inhibition against multiple tested microorganisms and a range of cancer cells. These data provide evidence thatAMPs may be candidates as novel antibiotic leads and that targeted modification of a natural AMP template can provide new insights into antibiotic design and development.
6
Lv, Liangchun. "Peptidomic and genomic analyses on bioactive peptides from the amphibian skin." Thesis, Queen's University Belfast, 2017. https://pure.qub.ac.uk/portal/en/theses/peptidomic-and-genomic-analyses-on-bioactive-peptides-from-the-amphibian-skin(ffa8be66-4a1e-404f-b22a-3f6fbb4782b5).html.
Повний текст джерелаАнотація:
Amphibian skin can secrete mucus from skin glands and this mucus always contains many types of antimicrobial peptides (AMPs) which can protect the hosts from bacterial infection. AMPs have been studied for a few decades with significant results as increasing numbers have been found, explored and developed to be evaluated as clinical drugs. This is a huge source of new molecules to help humans in their fight against diseases. In Chapter 3, a phylloxin-like AMP, QUB1966 and its analogue QUB2260, were studied. The results showed that QUB1966 exhibited antimicrobial effects against Gram-positive (Staphylococcus aureus) bacteria, Gram-negative (Escherichia coli) bacteria and yeast (Candida albicans). The modification increased the positive charge of the AMP, which enhanced the interaction between the peptide and the membrane of the selected microbes. The results showed that the modified peptide, QUB2260, expressed more potent antimicrobial function than the wild-type peptide QUB1966, increasing its inhibitory effect by 32-fold against E. coli and C. albicans, and 4-fold against S. aureus. Thus, the modified peptide might provide favourable prospects for novel biomedicine design and antibiotics substitution. In Chapter 4, a bradykinin-related peptide (BRP), QUB1315 (RAA-Val1, Thr6-bradykinin), was isolated from the skin secretion of Odorrana schmackeri with the defined primary sequence of RAAVPPGFTPFR. After bioactivity studies, QUB1351 revealed a dose-dependent contractile property on rat bladder. The analogue peptide, QUB1281 (RAA-Val1, Thr6, Leu8-bradykinin), was modified based on QUB1315 by replacing a single amino acid from Phe8 to Leu8 to test the antagonistic activity. However, the results showed that the modified peptide, QUB1281, was still an agonist. QUB1281 expressed less potency on bladder contraction than the wild-type QUB1315. It was also found that Thr6 and Leu8 might contribute to agonist effects and the substitution at position 8 could affect the affinity between peptides and bradykinin receptors. In Chapter 5, two novel peptides from Odorrana schmackeri, QUB1517 and QUB2025, were found to exhibit antibacterial potency against Gram-positive (Staphylococcus aureus) bacteria, Gram-negative (Escherichia coli) bacteria and yeast (Candida albicans). Their similar antimicrobial effects against these three microbes assumed that the same sequence domain might contribute to the antimicrobial activity. However, they both showed higher inhibitory activity on Gram-positive bacteria than Gram-negative bacteria. It is expected that the novel data described in this thesis will contribute to the burgeoning database of biologically-active peptides from amphibian skin secretions and may ultimately provide a basis for the development of new classes of peptide drugs for both major diseases and for orphan indications.
7
Zheng, Huiru. "New algorithms for the analysis of mass spectral profiles from amphibian data." Thesis, University of Ulster, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272069.
Повний текст джерела
8
Chia, Brian Cheng San. "Amphibian antimicrobial peptides : their structures and mechanisms of action : a thesis presented for the degree of Doctor of Philosophy." Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phc532.pdf.
Повний текст джерелаАнотація:
Copy of author's previously published works inserted. Bibliography: leaves 183-220. Three antimicrobial peptides, maculatin 1.1, uperin 3.6 and caerin 4.1 have been isolated from the respective skin glands of the Australian amphibians Litoria genimaculata, Uperoleia mjobergii and Litoria caerulea. To gain a deeper insight into their mechanisms of action, three dimensional structural studies have been conducted using circular dichroism, two-dimensional nuclear resonance and computer modelling techniques. The role of central flexibility within antibiotic peptides in their interaction with bacterial membranes is also discussed.
9
Wabnitz, Paul Andrew. "Chemistry and medical implications of novel amphibian peptides : a thesis submitted for the degree of Doctor of Philosophy /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phw112.pdf.
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10
Brinkworth, Craig Steven. "The primary and secondary structure determination of bioactive amphibian peptides : a thesis submitted for the degree of Doctor of Philosophy." Title page, contents and abstract only, 2003. http://web4.library.adelaide.edu.au/theses/09PH/09phb8586.pdf.
Повний текст джерелаАнотація:
"May 2003." Includes a list of publications by the author (journal articles related to thesis); and , copies of journal articles co-authored by the author. Includes bibliographical references (leaves 226-242) The solution structures of three peptides: Ala4Lys14-citopin 1.1 (amphipathic đ-helix); Gly15Gly19-caerin 1.1 (a less defined đ-helix); and, frenatin 3.1 (amphipathic đ-helix with a flexible c-terminal end) are presented in a discussion about structure/activity relationship
11
McLeod, Janet Leigh, and janet mcleod@deakin edu au. "The natriuretic peptides and their receptors in the brain of the amphibian, Bufo marinus." Deakin University. School of Biological and Chemical Sciences, 1999. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20071024.112730.
Повний текст джерелаАнотація:
The natriuretic peptides, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) are members of a family of hormones that play an important role in mammalian fluid and electrolyte balance. In the periphery, natriuretic peptides reduce blood volume and subsequently blood pressure by increasing renal natriuresis and diuresis and relaxation of vascular smooth muscle. The actions of natriuretic peptides are mediated via two membrane-linked guanylate cyclase receptors (NPR-GC); natriuretic peptide receptor-A (NPR-A) which has a high affinity for ANP and BNP; and natriuretic peptide receptor-B (NPR-B)which has the greatest affinity for CNP. A third receptor not linked to guanylate cyclase, natriuretic peptide receptor-C (NPR-C) also exists, which binds to ANP, BNP and CNP with a relatively equal affinity, and is involved with clearance of the peptides from the circulation and tissues. The natriuretic peptides are present in the brain and are particularly predominant in cardiovascular and fluid and electrolyte regulating areas such as the anteroventral third ventricle (AV3V) region. This distribution has led to the suggestion natriuretic peptides play a neuromodulatory role in the central control of fluid homeostasis. Natriuretic peptides in the brain have been observed to inhibit the release of other fluid and electrolyte regulating hormones such as arginine vasopressin (AVP) and angiotensin II (AII).
Natriuretic peptides have also been identified in the non-mammalian vertebrates although information regarding the distribution of the peptides and their receptors in the non-mammalian brain is limited. In amphibians, immunohistochemical studies have shown that natriuretic peptides are highly concentrated in the preoptic region of the brain, an area believed to be analogous to the A\T3\ region in mammals, which suggests that natriuretic peptides may also be involved in central fluid and electrolyte regulation in amphibians. To date, CNP is the only natriuretic peptide that has been isolated and cloned from the lower vertebrate brain, although studies on the distribution of CNP binding sites in the brain have only been performed in one fish species. Studies on the distribution of ANP binding sites in the lower vertebrate brain are similarly limited and have only been performed in one fish and two amphibian species. Moreover, the nature and distribution of the natriuretic peptide receptors has not been characterised. The current study therefore, used several approaches to investigate the distribution of natriuretic peptides and their receptors in the brain of the amphibian Bufo marinus. The topographical relationship of natriuretic peptides and the fluid and electrolyte regulating hormone arginine vasotocin was also investigated, in order to gain a greater understanding of the role of the natriuretic peptide system in the lower vertebrate brain.
Immunohistochemical studies showed natriuretic peptides were distributed throughout the brain and were highly concentrated in the preoptic region and interpeduncular nucleus. No natriuretic peptide-like immunoreactivity (NP-IR) was observed in the pituitary gland. Arginine vasotocin-like immunoreactivity (AvT-IR) was confined to distinct regions, particularly in the preoptic/hypothalamic region and pituitary gland. Double labelling studies of NP-JR and AvT-IR showed the peptides are not colocalised in the same neural pathways.
The distribution of natriuretic peptide binding sites using the ligands 125I-rat ANP (125I-rANP) and 125I-porcine CNP (125I-pCNP) showed different distributions in the brain of B. marinus. The specificity of binding was determined by displacement with unlabelled rat ANP, porcine CNP and C-ANF, an NPR-C specific ligand. 125I-rANP binding sites were broadly distributed throughout the brain with the highest concentration in pituitary gland, habenular, medial pallium and olfactory region. Minimal 125I-rANP binding was observed in the preoptic region. Residual 125I-rANP binding in the presence of C-ANF was observed in the olfactory region, habenular and pituitary gland indicating the presence of both NPR-GC and NPR-C in these regions. 125I-pCNP binding was limited to the olfactory region, pallium and posterior pituitary gland. All 125I-pCNP binding was displaced by C-ANF which suggests that CNP in the brain of B. marinus binds only to NPR-C.
Affinity cross-linking and SDS-PAGB demonstrated two binding sites at 136 kDa and 65 kDa under reducing conditions. Guanylate cyclase assays showed 0.1 µM ANP increased cGMP levels 50% above basal whilst a 10-fold higher concentration of CNP was required to produce the same result. Molecular cloning studies revealed a 669 base pair fragment showing 91% homology with human and rat NPR-A and 89% homology with human, rat and eel NPR-B. A 432 base pair fragment showing 67% homology to the mammalian NPR-C and 58% homology with eel NPR-D was also obtained.
The results show natriuretic peptides and their receptors are distributed throughout the brain of B. marinus which indicates that natriuretic peptides may participate in a range of regulatory functions throughout the brain. The potential for natriuretic peptides to regulate the release of the fluid and electrolyte regulating hormone AVT also exists due to the high number of natriuretic peptide binding sites in the posterior pituitary gland. At least two populations of natriuretic peptide receptors are present in the brain of B. marinus, one linked to guanylate cyclase and one resembling the mammalian clearance receptor. Furthermore, autoradiography and guanylate cyclase studies suggest ANP may be the major ligand in the brain of B. marinus, even though CNP is the only natriuretic peptide that has been isolated from the lower vertebrate brain to date.
12
Dong, Yanjing. "Identification, molecular cloning and functional characterization of novel bioactive peptides from amphibian skin secretion." Thesis, Queen's University Belfast, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.766285.
Повний текст джерела
13
Power, Gavin Jude. "Isolation, structural characterisation and mechanisms of action of novel insulin-releasing peptides from amphibian skin secretions." Thesis, University of Ulster, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.554281.
Повний текст джерелаАнотація:
Amphibian skin secretions are considered to be one of the richest resources of bioactive molecules in the animal kingdom for pharmaceutical prospecting. This thesis has investigated amphibian skin peptides of eight different species of anurans (frogs and toads) for insulin-releasing and anti-diabetic properties. The skins of Pseudis paradoxa, Hylarana guntheri, Hylomantis lemur and Leptodactylus laticeps, were tested for the presence of peptides with stimulatory effects on insulin-release from the clonal BRIN-BDll cell line. Upon purification of the skin secretions/extract, multiple insulin-releasing peptides were isolated and fully characterised by mass spectrometry along with N-terminal amino acid sequencing by Edman degradation. A number of synthetic peptides demonstrated potent in vitro biological activities, possessing the ability to stimulate insulin release up to a concentration of 3 flM without any association of cellular toxicity. For example, brevinin-2GUb isolated from the skin extract of H. guntheri stimulated insulin release 3.7 fold compared to 5.6 mmol/l glucose control (P
14
Gericke, Maria Catharina. "Aspects of amphibian chytrid infections in South Africa / M.C. Gericke." Thesis, North-West University, 2008. http://hdl.handle.net/10394/3713.
Повний текст джерелаАнотація:
The waterborne pathogen Batrachochytrium dendrobatidis (Bd), amphibian chytrid, is
implicated as being the causative agent for global amphibian declines. The fungus attacks the keratinized skin of adult and postmetamorphic animals and the keratinized mouthparts of tadpoles. Postmetamorphic animals seem to be more susceptible to Bd than tadpoles and adult frogs. Hypotheses exist that the origin of the fungus is in Africa. During the study different aspects of Bd infections in South African frogs were examined including the distribution of Bd, cultivation of Bd, preservation of cultures, the morphology of Bd as an infection as well as in culture and finally differences in host defense. Positive and negative localities for Bd were identified through surveys conducted in South Africa. These data will be contributed to the Bd Mapping Project and the African Bd Database in order to determine whether chytrid has any environmental preferences. Cultures obtained from the positive localities were maintained and cryopreserved for use in numerous experiments. In a future study, DNA extractions from the cultures will be analyzed using multilocus sequence typing in order to determine the sequence type of South African strains in comparison with global strains. This will provide important epidemiological information concerning the origin and control of Bd. The morphology of Bd was also examined using scanning electron microscopy and laser scanning confocal microscopy. Damage due to Bd infections was more severe on the larval mouthparts of Amietia vertebralis than that of Hadromophryne natalensis. The adverse effect of Bd is therefore not limited to postmetamorphic animals. Confocal microscopy uses fluorescent stains and lasers to examine specific structures within organisms. An especially effective stain used during confocal microscopy on Bd is Calcofluor White M2R. Due to its specificity this stain can be used as an effective screening tool for Bd in tissue. The role of antimicrobial skin peptides as a defense against Bd was also examined. A. vertebralis experiences die-offs due to chytrid, while H. natalensis does not experience the same effect in the presence of Bd. H. natalensis possess more antimicrobial skin peptides against Bd with a higher effectiveness than peptides extracted from A. vertebralis. This may explain the observed susceptibility of A. vertebralis to Bd. The relevance of this study is in order to identify areas in South Africa in which the probability of finding Bd is high. This will help in the surveillance of Bd and in the identification of susceptible species to be monitored and protected against the fungus. The effect of Bd on frog species can also be determined by means of exposure experiment using cultures isolated during this study. Through the identification of peptides effective against Bd, predictions can be made with regard to the susceptibility of different frogs to Bd, improving our ability to protect the amphibian biodiversity in South Africa. With the use of confocal microscopy in the examination of Bd, we became the first group to use the method. By the identification of a stain with a high potential as a screening tool, we also contributed to the more efficient identification of Bd in tissue. Keywords: Batrachochytrium dendrobatidis, Bd, amphibian chytrid, distribution, cultivation, antimicrobial skin peptides, laser scanning confocal microscopy, Amietia vertebralis, Hadromophryne natalensis, South AfricaThesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2009.
15
O'Rourke, Martin Gerard. "An investigation of the signalling pathways in mammalian tissues stimulated by an adenosine analogue and amphibian derived peptides." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393765.
Повний текст джерела
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Costa, André Sónia Maria. "Mécanisme d’action et relation structure-fonction des temporines SH, une famille de peptides antimicrobiens de la peau d’Amphibien." Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066757.
Повний текст джерелаАнотація:
Les peptides antimicrobiens (PAM) sont des effecteurs clés de l’immunité innée constituant une première ligne de défense contre les pathogènes. Ces peptides ont généralement un large spectre d’action antimicrobien et agissent efficacement et rapidement via un mécanisme membranolytique qui limite le développement de résistances. Face à l’émergence de microorganismes résistants, qui constitue un problème majeur de santé publique, les PAM représentent donc de bons candidats pour le développement thérapeutique d’agents anti-infectieux efficaces. Au cours de ma thèse je me suis intéressée aux PAM de la peau d’Amphibiens. Dans un premier temps, à l’aide d’approches biochimiques et de biologie moléculaire, nous avons identifié 5 précurseurs potentiels de PAM à partir de la grenouille Trachycephalus resinifictrix, dont deux précurseurs de cathélicidines, deux précurseurs similaires à ceux des “PAM/opioïde“ (T. venulosus) et un précurseur similaire à celui des hylareleasines (Hyla simplex). Dans un deuxième temps, je me suis intéressée à différentes temporines SH, de petits PAM précédemment identifiés par notre équipe à partir de la grenouille Pelophylax saharicus. Une étude a été menée pour établir les relations structure-fonction de la temporine-SHf, un PAM linéaire d’Amphibien considéré aujourd’hui comme le plus petit (8 résidus). Les résultats obtenus ont permis d’identifier plusieurs analogues dont l’index thérapeutique est fortement amélioré. D’autre part, le mécanisme d’action antimicrobien de la temporine-SHa et de ses analogues a été approfondi. Nous avons démontré que les temporines agissent rapidement via un mécanisme membranolytique entrainant la rupture de la membrane bactérienne (effet détergent). Contre les formes promastigotes du parasite Leishmania, le mécanisme primaire des temporines est également membranolytique mais cependant, une apoptose des parasites est observée à des concentrations de peptides plus élevées. Enfin, la temporine-SHe, qui restait non caractérisée, a été étudiée structuralement et fonctionnellement grâce à des techniques biophysiques couplées à des techniques biologiques. Comme la temporine-SHa, ce PAM possède un spectre d’action large incluant également le parasite Leishmania. L’ensemble des résultats indique que les temporines pourraient servir de composés chefs de file pour la conception d’une nouvelle classe thérapeutique d’anti-infectieuxAntimicrobial peptides (AMPs) are key effectors of innate immunity that provide a first line of defense against pathogens. These peptides typically have broad-spectrum antimicrobial activity and act rapidly and efficiently through a membranolytic mechanism that limits the development of resistance. With the emergence of resistant microorganisms, a major public health concern, AMPs therefore represent good candidates for the therapeutic development of new and valuable compounds. During my thesis, I focused on AMP from amphibian skin. Firstly, five potential AMP precursors were identified from the frog Trachycephalus resinifictrix using a combined biochemical /molecular biology approach. Among these, two correspond to cathelicidin precursors, two were similar to the “AMP/opioid“ precursors (T. venulosus), and one was similar to hylareleasin precursors (Hyla simplex). Secondly, I was interested in temporins SH, small AMPs previously isolated from the frog Pelophylax saharicus by our team. We performed structure-activity relationship studies on temporin-SHf, the smallest linear amphibian AMP known to date (8 residues). This allowed us to identify several potent analogs with a higher therapeutic index. Furthermore, we also thoroughly studied the mechanism of action of temporin-SHa and its analogs. We showed that temporins act rapidly through a membranolytic mechanism, leading to bacterial membrane disruption (detergent-like effect). For Leishmania promastigotes, the same membranolytic mechanism was observed with also a temporin-induced apoptosis that takes place at higher peptide concentrations. Finally, biophysical and biological techniques enabled us to structurally and functionally characterize temporin-SHe. Like temporin-SHa, this peptide displayed a broad-spectrum activity including Leishmania. Our results indicate that temporins could serve as lead compounds to develop a new class of therapeutic anti-infective peptides
17
Burkart, David. "UNDERSTANDING CHYTRIDIOMYCOSIS RESISTANCE BY INVESTIGATING THE CUTANEOUS DEFENSE MECHANISMS OF MARSUPIAL FROGS." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1835.
Повний текст джерелаАнотація:
Anurans are declining worldwide because of the spread of Batachochytrium dendrobatidis (Bd), the fungus that causes chytridiomycosis. However, some frogs are resistant to this disease, and understanding why may be critical to saving those that are susceptible. In Peru, Gastrotheca excubitor is resistant to chytridiomycosis while Gastrotheca nebulanastes is susceptible. Two anuran skin defenses, symbiotic bacteria and antimicrobial peptides (AMPs), have demonstrated the ability to inhibit Bd in vitro when isolated from certain frogs. We tested if these defenses can explain the difference in susceptibility between the two Gastrotheca species. The cutaneous bacteria and AMPs of both species were collected, tested for their abilities to inhibit the growth of Bd, and analyzed for their compositions. Results indicate that 34%of the strains of skin bacteria from G. excubitor were able to inhibit the growth of Bd whereas only 10% isolated from G. nebulanastes were effective. Gastrotheca excubitor also has stronger anti-Bd skin bacteria. Neither frog species has peptide mixtures capable of completely inhibiting Bd, and overall species did not differ in the anti-Bd abilities of their peptides. These results suggest that the chytridiomycosis resistance experienced by G. excubitor may be attributed to its skin bacteria.
18
Krynak, Katherine L. "ENVIRONMENTAL INFLUENCES ONAMPHIBIAN INNATE IMMUNE DEFENSE TRAITS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1435590530.
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Marenah, Lamin. "Novel peptide discovery : isolation and characterisation of peptides with antidiabetic properties from the skin secretions of amphibians." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274394.
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Condamine, Eric. "Etudes pharmacologiques et structurales des peptides E bovin et amphibien, dérivés de la proenképhaline A." Rouen, 1999. http://www.theses.fr/1999ROUES020.
Повний текст джерелаАнотація:
Un peptide dérivé de la proenképhaline A a été isolé en 1995 à partir d'un extrait de cerveau de grenouille verte européenne (Rana Ridibunda) et nommé peptide E de grenouille. Ce peptide de 25 acides aminés ne diffère du peptide E de boeuf (proenképhaline A [206-230]) que par deux substitutions d'acides aminés (M15 →Q et L25→M). Depuis la découverte du peptide E bovin (1981), ce peptide était décrit comme un agoniste sélectif du récepteur mu ayant une puissante activité analgésique. Cependant, les premieres études pharmacologiques entreprises sur le peptide E de grenouille n'ont montré aucune activité antinociceptive significative. Face à de telles différences d'activité, alors que les peptides présentent une grande homologie de structure primaire, nous avons entrepris une analyse des relations structure-activité sur les peptides E de boeuf et de grenouille. L'étude pharmacologique a été reprise en élargissant l'investigation à plus forte dose, et la détermination des structures secondaires des deux peptides a été mise en oeuvre. - les effets pharmacologiques mesurés (épreuves de la plaque chaude et des crampes abdominales) sont identiques pour les deux peptides. L'activité antinociceptive, mettant en jeu le système opioïdergique, ne s'exprime qu'à forte dose et met donc en doute le caractère analgésique puissant prêté au peptide E bovin dans la littérature. - l'étude structurale a été réalisée par calculs de prédiction de structure secondaire, dichroïsme circulaire, résonance magnétique nucléaire et modélisation sous contraintes RMN. Les deux peptides adoptent des structures secondaires similaires, incluant une partie hélicoïdale entre les résidus 10 et 20, en accord avec les résultats pharmacologiques identiques relevés. Les résultats obtenus sont discutés en regard de la β-endorphine qui possède une très forte activité antinociceptive et une structure secondaire relativement semblable à celles des peptides E.
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Houston, Rebecca. "Cell biological studies on a novel amphibian derived peptide analogue." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.676522.
Повний текст джерелаАнотація:
Amphibian skin is a multi-functional organ which has adapted to function as a barrier against hostile environmental pathogens and to protect against predatory attack. Highly specialised dermal glands release a complex cocktail of bioactive compounds onto the skin; this mixture contains biogenic amines, proteins, alkaloids and a plethora of bioactive peptides. A vast array of peptides have been identified from over 500 species of amphibians to date which have been found to exert, a range of biological effects. Families of peptides derived from amphibian skin secretions which have been studied in particular detail include the bombesins and related peptides, the bradykinins and related peptides, the skin opiates and those with antimicrobial activities. This thesis presents a study of the biological activities of a novel hybrid pentapeptide derived from amphibian skin secretions.
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Raja, Zahid. "Caractérisation fonctionnelle de peptides antimicrobiens de peau d'amphibien." Paris 6, 2013. http://www.theses.fr/2013PA066829.
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Pan, Hao. "Studies on novel bioactive peptides from the skin secretion of amphibians." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709692.
Повний текст джерелаАнотація:
Over many decades, naturally-occurring substances have been considered as an integral part of the treatment of human diseases. Skin secretions from amphibians play an important role for sourcing such agents with therapeutic potential. Amongst all types of substances discovered from amphibian skin secretion, peptides represent a large family of bioactive molecules with distinctive biological functions. To date, more than 2000 host defence peptides have been studied and many of them possess antimicrobial, antifungal or anticancer properties. In the present study, bioactive peptides have been isolated from skin secretions of four amphibians, the green tree frog Litoria caerulea, the white-lipped tree frog Litoria infrafrenata, the green and golden bell frog Litoria aurea and the European edible frog Rana esculenta. Amongst three bioactive peptides, three belong to the neuromedin U family and the other is a brevinin analogue. By using genomic and proteomic techniques, biosynthetic precursor-encoding cDNAs from each species were selectively cloned. The chemical structures of mature peptides was confirmed by MS/MS fragmentation sequencing and reverse phase HPLC. Biological functions of their synthetic replicates were screened in functional assays, including smooth muscle preparations and minimum inhibitory concentration assays for determining effects on microorganism growth.
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Hou, Xiaojuan. "Identification and molecular cloning of skin secretion peptides from selected Eurasian amphibians." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680080.
Повний текст джерелаАнотація:
The skin secretions of amphibians are used as a chemical defence mechanism as protection against predators within their natural environments. Among the classes of compounds contained within the secretions, peptides with diverse bioactivities, such as antimicrobial and pharmacological, are generally the most abundant. Such peptides may have therapeutic potential. In particular, the antimicrobial peptides have their own advantages, when compared with conventional clinical antibiotics. Many scientists have thus been studying the biologically-active peptides of amphibian skin and attempting to assess them as candidates for future therapeutic drugs. This thesis describes analyses performed on bioactive peptides from the skins of bombinid toads and ranid frogs. However, as the skin secretions of amphibians are complex mixtures of compounds, the identification of single active compounds in the past years was complicated and the outputs were consequently of a relatively low order. In recent years, advances in detection and analytical techniques have greatly aided in the identification of single active novel compounds from such skin secretions. In this thesis, several antimicrobial peptides and one pharmacological peptide were identified from the selected amphibian species. These isolated novel peptides demonstrate that the skins/skin secretions of amphibians continue to represent a rich source of natural peptides with varied structures and distinct bioactivities.
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Vanhoye, Damien. "Analyse évolutive, moléculaire et fonctionnelle des peptides antimicrobiens des amphibiens." Paris 6, 2004. http://www.theses.fr/2004PA066326.
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Farragher, Susan. "Study of peptide transcripts in the skin and stimulated skin secretions of three different species of amphibians." Thesis, University of Ulster, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232839.
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Chen, Dong. "Identification, molecular cloning and functional characterisation of novel bioactive peptide drugs from amphibian skin secretions." Thesis, Queen's University Belfast, 2017. https://pure.qub.ac.uk/portal/en/theses/identification-molecular-cloning-and-functional-characterisation-of-novel-bioactive-peptide-drugs-from-amphibian-skin-secretions(a5d6ffd1-1440-4528-af7a-4f6d9e244f76).html.
Повний текст джерелаАнотація:
Skin secretions of amphibians, which contain a large amount of bioactive compounds, play an essential role in their survival. For instance, some toxic or irritant secretions can protect them against predators. Due to the pharmacological and bioactive characteristics of the components in amphibian skin secretion, these secretions have been considered as one of the world’s richest source of such agents. In this study, the skin secretions of the frogs Odorrana livida, Hylarana latouchii and Phyllomedusa sauvagii were collected from the dorsal surface and immediately frozen in liquid nitrogen. Afterwards, a series of molecular techniques, including mRNA isolation, cDNA library construction, PCR, agarose gel analysis and DNA sequencing were applied. The novel peptide sequences were deduced from cloned cDNAs and then confirmed by using MALDI-TOF mass spectrometry and MS/MS fragmentation sequencing. Finally, three novel peptides were chemically-synthesised. The determination of the therapeutic bioactivities of the three novel peptides was carried out by a series of assays. QUB-1384, exhibited BK-receptor agonist-like functions which induced the contraction of rat bladder and uterus tissues. QUB-1906 is a Bowman-Birk inhibitor which could efficiently inhibit the activity of trypsin. The novel dermaseptin peptide, QUB-2949, had broad-spectrum anticancer activities against human cancer cell lines including PC-3 (ATCC-CRL-1435), U251MG (ecacc-09063001), H157 (ATCC-CRL-5802), MCF-7 (ATCC-HTB-22) and MDA-MB-435S (ATCC-HTB-129). Meanwhile, like other dermaseptin peptides, QUB-2949 showed effective growth inhibitory activity against the standard Gram-negative bacterium Escherichia coli (NCTC 10418), the standard Gram-positive bacterium Staphylococcus aureus (NCTC 10788), the pathogenic yeast Candida albicans (NCPF 1467), the drug-resistant bacterium Enterococcus faecalis (ATCC 29212), Methicillin-resistant Staphylococcus aureus (MRSA) (ATCC BAA-2094) and Pseudomonas aeruginosa (NCTC 13437). In addition, according to the results of haemolysis assay and HMEC-1 MTT assay, all the peptides exhibited low cytotoxicity. In conclusion, three novel peptides were found and assessed in this project. The multifunction and low cytotoxicity of these bioactive peptides make them promising candidates for natural drug discovery and provide new prospect for clinical treatments.
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Steinborner, Simon Todd. "The observation of evolutionary trends in amphibians and the analysis of negative ion fragmentations in large peptide systems by mass spectrometry /." Title page, contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phs819.pdf.
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Amiche, Mohamed. "Les Peptides opioïdes de la peau d'amphibiens : la dermophine et la dermenkephaline : études structurales et pharmacologique." Paris 6, 1990. http://www.theses.fr/1990PA066017.
Повний текст джерелаАнотація:
La peau des amphibiens est riche en peptides et amines biogènes porteurs d'activités physiologiques variées : plus d'une quarantaine de peptides ont été isolés au cours de ces vingt dernières années. Parmi ceux-ci, la dermorphine (Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-conh2), peptide opioïde isole de la peau de phyllomedusa sauvagii, possède une activité analgésique 700 à 1000 fois plus puissante que celle de la morphine. Des expériences de liaison et d'autoradiographie que nous avons réalisé avec une dermorphine tritiée à haute radioactivité spécifique, montrent que cet heptapeptide est le premier opioïde endogène combinant une haute affinité à une haute sélectivit pour le récepteur opioïde de type mu. Dans l'un des précurseurs de la dermophine (pro-dermorphine II) une des séquences dermorphine est remplacée par une séquence distincte. Nous avons fait l'hypothèse que cette séquence correspondait à une nouvelle molécule contenant un résidu methionyl sous la configuration D en position 2 : Tyr-D-Met-Phe-His-Leu-Met-Asp-conh2. A l'aide d'anticorps spécifiques dirigés contre cette séquence nous avons isolé ce peptide de la peau de Phyllomedusa Sauvagii. Ce nouveau peptide, baptise dermenkephaline se comporte comme un puissant agoniste du récepteur opioïde Delta. La pro-dermorphine offre donc un exemple unique de précurseur biosynthétique plurifonctionnel susceptible de générer deux peptides possédant un acide aminé de la série D, peptides qui se lient spécifiquement à deux des classes des récepteurs opioïdes. A l'instar des enképhalines, dynorphines et endorphines, les dermorphines-dermenkephalines pourraient donc représenter une quatrième famille de peptides opioïdes endogènes qui serait caractérisée par une exceptionnelle spécificité de liaison aux récepteurs opioïdes
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Netchitailo, Pierre. "La corticostéroïdogénèse chez un amphibien anoure : mécanismes intracellulaires et contrôle multifactoriel." Rouen, 1987. http://www.theses.fr/1987ROUES037.
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Abbassi, Feten. "Caractérisation structurale et fonctionnelle des temporines-SH : de nouveaux peptides antimicrobiens isolés chez l'espèce de grenouille nord-africaine Pelophylax saharica." Paris 6, 2009. http://www.theses.fr/2009PA066702.
Повний текст джерелаАнотація:
Durant cette thèse, nous avons étudié le répertoire peptidique antimicrobien de la grenouille Pelophylax saharica. Nous avons identifié trois nouvelles temporines : Temp-SHa, -SHb et -SHc. Les temporines sont de petits peptides antimicrobiens (13-14 résidus) surtout actifs contre les bactéries Gram+. Seule la Temp-SHa s’est révélée très active, particulièrement contre les bactéries Gram- et contre le parasite Leishmania infantum. Parmi les temporines (13 résidus, charge nette +2), la Temp-SHa présente la meilleure activité et le plus large spectre antimicrobien. L’analogue [K3]Temp-SHa plus cationique que le peptide parent est, quant à lui, beaucoup plus antimicrobien. Il perturbe plus efficacement et sélectivement les modèles membranaires anioniques et perméabilise la membrane de bactéries Gram- (E. Coli). La petite taille de l’analogue [K3]Temp-SHa, son fort pouvoir antimicrobien et son large spectre d’action en font un bon candidat pour une utilisation potentielle en thérapeutique
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Leboulenger, François. "Contribution à l'étude de l'activité de la corticosurrénale des amphibiens anoures, une glande endocrine sous contrôle multifactoriel." Rouen, 1986. http://www.theses.fr/1986ROUES027.
Повний текст джерелаАнотація:
Mise en évidence des fluctuations saisonnières et journalières des taux circulants de corticostéroïdes. Analyse des paramètres de la réponse corticosurrénalienne à l'ACTH et à différents peptides issus de la maturation de la proopiomélanocortine. Mise en évidence de la co-localisation du VIP et de peptides opiacés dans les granules de sécrétion des cellules chromaffines, rôle de ces peptides dans la stimulation de la stéroïdogenèse. Structure de la proenképhaline A d'amphibien. Rôle de l'acétylcholine via des récepteurs muscariniques utilisant les prostaglandines comme second messager
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Rudolf, Étienne. "Expression, purification et caractérisation biochimique partielle de la peptidase-1 marqueur du sexe génotypique chez pleurodèles waltl (amphibien urodèle)." Nancy 1, 1995. http://www.theses.fr/1995NAN10393.
Повний текст джерелаАнотація:
La peptidase-1 chez pleurodèles waltl est un marqueur du sexe génotypique. L’étude de son expression enzymatique au cours du développement à température ambiante et à 32C° ainsi que sa localisation corporelle chez les adultes nous permet d'affirmer qu'elle ne joue pas de rôle dans la détermination du sexe. Sa purification a été entreprise et a permis d'obtenir deux sous-unités de masse moléculaire distincte de 90 et 99 kda. Certains paramètres biochimiques ont été définis à partir d'extraits prépurifiés. La peptidase-1 est une métalloenzyme d'une masse moléculaire d'environ 170 kda, elle hydrolyse essentiellement des dipeptides in vitro. Son rôle biologique n'est à l'heure actuelle pas encore connu
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Galanth, Cécile. "Etude du mécanisme d'action d'une peptide cationique antibactérien, la dermaseptine B2." Paris 6, 2009. http://www.theses.fr/2009PA066047.
Повний текст джерелаАнотація:
L’objet de cette thèse est l’étude du mécanisme antibactérien de la dermaseptine B2 (Drs B2), peptide isolé de la peau de grenouille amazonienne du genre Phyllomedusa. Nous avons montré qu’elle induit une courbure positive de la membrane du fait de sa forte charge positive lors de son insertion, laissant présager la formation de pores toroïdaux. De plus, la flexibilité de la région N-terminale du peptide ainsi que le caractère hydrophobe, réparti en deux domaines séparés par un coeur hydrophile, sont indispensables à son adaptabilité et à son insertion dans le corps hydrophobe de la bicouche. Une étude comparative entre les PAM et les CPP a montré que ces deux familles peptidiques recrutaient préférentiellement des lipides membranaires chargés négativement à chaînes acyles courtes et insaturées. Par ailleurs, nous avons observé que la Drs B2 ne possédait pas la capacité à franchir les membranes des cellules de mammifère. La frontière entre ces deux familles peptidiques est à élucider.
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Almeida, Richardson Alves de. "Peptídeos antimicrobianos de Hypsiboas cinerascens (Spix, 1824)." Universidade Federal do Amazonas, 2011. http://tede.ufam.edu.br/handle/handle/4452.
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Amphibian skin secretions are rich sources of biologically active substances with various physiological functions and defense, most of low molecular weight, as biogenic amines, alkaloids, steroids, peptides and proteins of high molecular weight. The genus Hypsiboas, belonging to the family Hylidae from class of amphibians, presents as promissing supplier of peptides with biological potential. Peptides identified of species Hypsiboas are analogous to the known antimicrobial peptides. This work was realized a systematic study of the skin secretion of Hypsiboas cinerascens obtained by stimulation, where it was possible to identify a new peptide with wide antimicrobial activity, named cinerascetina. Its sequence was identified by techniques of high performance liquid chromatography (HPLC) and mass spectrometry (MALDI-TOFTOF) and confirmed by genetic sequencing, and was also possible identified six new peptides with possible antimicrobial activity.
Secreções de pele de anfíbios são fontes ricas de substâncias biologicamente ativas com diversas funções fisiológicas e de defesa, a maioria de baixa massa molecular como as aminas biogênicas, alcaloides, esteroides, peptídeos e proteínas de massa molecular elevada. O gênero Hypsiboas, pertencente à família Hylidae da classe dos anfíbios, apresenta-se como promissor fornecedor de peptídeos com potencial biológico. Peptídeos identificados de espécies de Hypsiboas apresentaram analógia a peptídeos antimicrobianos conhecidos. Neste trabalho foi realizado um estudo sistemático da secreção da cutânea de Hypsiboas cinerascens obtida por estimulação, onde foi possível identificar um novo peptídeo com ampla atividade antimicrobiana, o qual foi denominado de Cinerascetina. Sua sequência foi identificada por técnicas de cromatografia liquida de alta eficiência (CLAE) e espectrometria de massa (MALDITOF- TOF) e confirmada por técnica de sequenciamento genético, sendo que através desse estudo de sequenciamento genético, também foi possível identificar seis novos peptídeos com possível atividade antimicrobiana.
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Pinto, Erika Gracielle. "Isolamento, caracterização e atividade anti-leishmania chagasi e anti-trypanosoma cruzi de compostos bioativos de venenos de anfíbios brasileiros." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/99/99131/tde-31012014-154317/.
Повний текст джерелаАнотація:
Dentre as doenças parasitárias tropicais, as causadas por protozoários se apresentam como um grande desafio para a saúde pública, sendo representadas pela leishmaniose e doença de Chagas. Afetam grandes populações marginais ao processo econômico globalizado, e desta forma, não são vistas como mercados potenciais. O presente projeto visou o isolamento de novos compostos naturais de venenos animais com atividade anti-Leishmania e anti-T. cruzi. O presente estudo fracionou por diferentes técnicas cromatográficas, os venenos dos anfíbios Siphonops annulatus, Corythomantis greeningi, Aparasphenodon brunoi e Phyllomedusa hypochondrialis, visando o isolamento de peptídeos e metabólitos secundários através de ensaios biomonitorados. Utilizando-se a espectrometria de massas e seqüenciamento por degradação química de Edman, foi possível a caracterização bioquímica de cinco peptídeos ativos da secreção de Phyllomedusa hypochondrialis, sendo estes a bradicinina, as dermaseptinas 1 e 4 e as filoseptinas 7 e 8. Os peptídeos apresentaram uma Concentração Efetiva 50% (CE50) variando entre 0,7 a 20 ?g/mL em L. (L.) infantum chagasi e T. cruzi, com baixa ou nenhuma citotoxicidade para células de mamíferos nas concentrações testadas. Além disso, a separação química da secreção do anfíbio Siphonops annulatus forneceu uma fração altamente ativa em promastigotas de L. (L.) infantum chagasi, com CE50 0,065 ?g/mL, porém com toxicidade bastante elevada para macrófagos peritoneais e nenhuma seletividade nas formas intracelulares. Estudos ultraestruturais de Leishmania demonstraram severos danos mitocondriais, além da formação de grande vacúolos citoplasmáticos, levando o parasita a morte em poucas horas. O presente estudo demonstrou o potencial de peptídeos e metabólitos secundários de venenos de anfíbios, que se adequadamente estudados, poderão contribuir como novos protótipos de fármacos para a doenças negligenciadas.Among the tropical parasitic diseases, those caused by protozoa present a major challenge to public health, being represented by leishmaniasis and Chagas disease. Affect large populations marginal to the global economic process, and thus are not seen as potential markets. This project aimed the isolation of new natural compounds in animal venoms with anti-Leishmania activity and anti-T. cruzi. The present study fractionated by different chromatographic techniques, the poisons of the amphibians Siphonops annulatus, Corythomantis greeningi, Aparasphenodon brunoi and Phyllomedusa hypochondrialis, aiming the isolation of peptides and secondary metabolites through bioguided assays. By using mass spectrometry and sequencing by Edman degradation, it was possible to do the biochemical characterization of five active peptides from the poison of Phyllomedusa hypochondrialis, as bradykinin, dermaseptins 1 and 4 and phylloseptins 7 and 8. The peptides showed a 50% Effective Concentration (EC50) ranging from 0.7 to 20 ?g/mL in L. (L.) infantum chagasi and T. cruzi, with little or no cytotoxicity to mammalian cells at the tested concentrations. In addition, the chemical separation of the poison of the amphibian Siphonops annulatus provided a highly active fraction against promastigotes of L. (L.) infantum chagasi, with an EC50 of 0.065 ?g/mL, but highly toxicity to peritoneal macrophages and without selectivity against the intracellular forms of Leishmania. Ultrastructural studies of Leishmania showed severe mitochondrial damages and the formation of large cytoplasmic vacuoles, leading to parasite death within few hours. The present study demonstrated the potential of peptides and secondary metabolites of amphibian poisons, and if adequately studied, may contribute as prototypes of new drugs for neglected diseases.
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Maselli, Vita Marie. "Amphibian neuropeptides : isolation, sequence determination and bioactivity." 2006. http://hdl.handle.net/2440/37864.
Повний текст джерелаАнотація:
The skin extracts from amphibians have been investigated for over fifty years and have been found to contain numerous components with therapeutic and medicinal uses. Host - defence compounds are secreted onto the dorsal surface of the animal from specialised granular glands in response to a variety of stimuli, such as stress induced by a predator. Isolated peptides can exhibit either pharmacological properties or antibiotic activity. Previous studies isolated a potent hypotensive neuropeptide, crinia angiotensin II, within skin secretions of the Australian frog Crinia georgiana. This prompted further investigations into the isolation and sequence determination of host - defence compounds from other species in this genus - C. signifera, C. riparia and C. deserticola. Fifteen novel peptides were identified. The major peptide components were potent disulfide containing neuropeptides of a type not observed in other Australian anurans that have been previously investigated. The remaining peptides demonstrate either antibiotic activity or inhibit the enzyme neuronal nitric oxide synthase. The skin components from anurans of the Litoria genus have been extensively studied, with a number of peptides exhibiting both antibacterial and pharmacological activity. The skin secretion of Litoria dentata has been investigated, with five novel peptides identified. The neuropeptide tryptophyllin L 1.3 was previously isolated from the related frog L. rubella. Other components that are unique in structure have not yet been tested for biological activity. The parasitic disease malaria is responsible for over one million deaths per year. The increase in resistance of current antimalarial compounds has led to the development of new treatments from various animal - derived peptide antimicrobials. A number of amphibian peptides and their derivatives were investigated as potential antiplasmodial agents against the malaria parasite Plasmodium falciparum. Results indicate that these compounds inhibit parasite growth with minimal haemolytic activity, making them promising tools for malaria research.The defence chemistry of amphibian neuropeptides has been extensively studied and is important in understanding both the ecology and physiology of the vertebrate. Neuropeptides are classified into groups with similar structural characteristics. Biological activity occurs via interaction with a G protein - coupled receptor. The most studied of all amphibian neuropeptides is caerulein, which has a similar spectrum of activity to the mammalian peptide cholecystokinin. This includes smooth muscle contraction that occurs via interaction with cholecystokinin receptors. The pharmacological activity of Australian anuran neuropeptides from various genera was investigated. Two biological assays were conducted - a smooth muscle contraction test and a lymphocyte proliferation assay. A range of neuropeptides contracted smooth muscle at nanomolar concentrations, while others only proliferated lymphocytes. Some peptides were inactive in both assays. Young marsupials are born at an immature stage of development and rely on immune protection provided by the mother. Eugenin is a host - defence compound isolated from pouch secretions of the Tammar wallaby. The immunomodulator activates CCK2 receptors, resulting in lymphocyte proliferation. Therefore, eugenin stimulates immune cells in the pouch providing vital immune protection for pouch young.Thesis (Ph.D.)--School of Chemistry and Physics, 2006.
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Apponyi, Margit Anneliese. "Amphibian skin peptides which inhibit nNOS : structure and binding studies using heteronuclear NMR." 2006. http://hdl.handle.net/2440/37795.
Повний текст джерелаАнотація:
Using 2 - D NMR spectroscopy, the structure of the sex pheromone from Litoria splendida has been determined, in order to elucidate its mode of transport through the aquatic environment. The peptide was found form an α - helical structure, with a central flexible hinge region. The mode of transport through the aquatic environment has been discussed in relation to the structure. Previous work indicated that the Australian amphibian host defence skin peptides that inhibit neuronal nitric oxide synthase ( nNOS ) were likely to act indirectly on the enzyme, by binding to the co - enzyme of nNOS, calmodulin. [superscript 15] N labelled calmodulin was expressed and purified via a bacterial protein expression system and a series of 2 - D NMR [superscript 15] N - HSQC titrations was performed with Australian amphibian host defence skin peptides. in order to determine whether these peptides bind to calmodulin. The three peptides tested were found to bind, and with differing strengths of interaction. One of these was selected for further study. [superscript 15] N and [superscript 13] C doubly labelled calmodulin was then prepared in order to study the complex between this protein and the selected peptide, caerin 1.8, an Australian amphibian skin peptide isolated from Litoria chloris. A series of 3 - D NMR spectra has been recorded on this complex. The backbone atom resonances have been assigned for free calmodulin and for the calmodulin - peptide complex, using a combination of main chain directed and sequential assignment strategies. By analysing the changes in chemical shift that occur upon binding the peptide, it was determined that the mode of binding involves a stronger interaction with the C - terminal domain than the N - terminal domain.Thesis (Ph.D.)--School of Chemistry and Physics, 2006.
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Brinkworth, Craig Steven. "The primary and secondary structure determination of bioactive amphibian peptides." Thesis, 2003. http://hdl.handle.net/2440/80313.
Повний текст джерелаАнотація:
Amphibians secrete a mixture of biologically active compounds from within glands under the skin in response to attack by predators. One of the major class of compounds secreted in this
biological arsenal are bioactive polypeptides. These peptides possess many biological functions including acting as antibiotics, anti cancer agents and inhibiting the formation of NO by nNOS. These functions make them interesting from a therapeutic viewpoint as potential drugs. Negative ion mass spectrometry of peptides contains significant sequencing information differing from that obtained in the positive ion mode. Information unique to negative ion mass spectrometry of peptides includes fragmentations (i) identifying the presence of a specific amino acid in the sequence (Ser, Thr, Asp, Asn, Gln, Glu) and (ii) identifying the position of specific amino acids within the peptide sequence (Phe, ser, Thr, Asp, Asn, Gln Glu). The skin secretion of the Litoria eucnemis contains four novel peptides belonging to two peptide families -the caerin 1s and maculatins and is the first Australian frog investigated to demonstrate this property. Three of the peptides exhibit antibacterial and anticancer activities. However, the three peptides are some of the least active, among their respective families. Primary and secondary structural properties are important factors in determining the biological activity of polypeptides. The solution structures of three peptides Ala4Lysl4- citopin 1.1 (amphiparhic α-helix), Glyl5Glyl9-caerin 1.1 (a less-defined α-helix) and frenatin 3.1 (amphipathic α-helix with a flexible C-terminal end) are presented in a discussion about this structure/activity relationship.Thesis (Ph.D.) -- University of Adelaide, Dept. of Chemistry, 2003
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Apponyi, Margit Anneliese. "Amphibian skin peptides which inhibit nNOS : structure and binding studies using heteronuclear NMR." Thesis, 2006. http://hdl.handle.net/2440/37795.
Повний текст джерелаАнотація:
Using 2 - D NMR spectroscopy, the structure of the sex pheromone from Litoria splendida has been determined, in order to elucidate its mode of transport through the aquatic environment. The peptide was found form an α - helical structure, with a central flexible hinge region. The mode of transport through the aquatic environment has been discussed in relation to the structure. Previous work indicated that the Australian amphibian host defence skin peptides that inhibit neuronal nitric oxide synthase ( nNOS ) were likely to act indirectly on the enzyme, by binding to the co - enzyme of nNOS, calmodulin. [superscript 15] N labelled calmodulin was expressed and purified via a bacterial protein expression system and a series of 2 - D NMR [superscript 15] N - HSQC titrations was performed with Australian amphibian host defence skin peptides. in order to determine whether these peptides bind to calmodulin. The three peptides tested were found to bind, and with differing strengths of interaction. One of these was selected for further study. [superscript 15] N and [superscript 13] C doubly labelled calmodulin was then prepared in order to study the complex between this protein and the selected peptide, caerin 1.8, an Australian amphibian skin peptide isolated from Litoria chloris. A series of 3 - D NMR spectra has been recorded on this complex. The backbone atom resonances have been assigned for free calmodulin and for the calmodulin - peptide complex, using a combination of main chain directed and sequential assignment strategies. By analysing the changes in chemical shift that occur upon binding the peptide, it was determined that the mode of binding involves a stronger interaction with the C - terminal domain than the N - terminal domain.Thesis (Ph.D.)--School of Chemistry and Physics, 2006.
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Chia, Brian Cheng San. "Amphibian antimicrobial peptides : their structures and mechanisms of action / by Brian Cheng San Chia." Thesis, 2000. http://hdl.handle.net/2440/19636.
Повний текст джерелаАнотація:
Copy of author's previously published works inserted.Bibliography: leaves 183-220.
xiii, 226 leaves : ill. (chiefly col.) ; 30 cm.
Three antimicrobial peptides, maculatin 1.1, uperin 3.6 and caerin 4.1 have been isolated from the respective skin glands of the Australian amphibians Litoria genimaculata, Uperoleia mjobergii and Litoria caerulea. To gain a deeper insight into their mechanisms of action, three dimensional structural studies have been conducted using circular dichroism, two-dimensional nuclear resonance and computer modelling techniques. The role of central flexibility within antibiotic peptides in their interaction with bacterial membranes is also discussed.
Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2000
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Calabrese, Antonio Nickolas. "Characterisation of protein structure and interactions: novel applications to the study of bioactive peptides." Thesis, 2013. http://hdl.handle.net/2440/82148.
Повний текст джерелаАнотація:
The studies of protein/peptide folding, misfolding, structure, and interactions are vital to understanding complex biological problems. The work presented in this thesis describes the development and application of a variety of biophysical techniques to investigate protein structure and interactions, with applications to the structure and function of several bioactive peptides. Firstly, the development of a novel negative ion amenable chemical crosslinking-mass spectrometry (CX-MS) approach is described. CX-MS is a low-resolution technique to study protein structure and interactions. It involves covalent modification and tethering of a protein complex by a reactive reagent, followed by proteolytic digestion. The sites of the intra- and inter-molecular crosslinks provide distance restraints for modelling and enables conclusions to be drawn about the three-dimensional structure and binding interfaces within a protein complex. However, easy identification of crosslinks amongst the large quantity of proteolytic fragments remains challenging. In this study, the application of novel disulfide-based MS cleavable crosslinking reagents was investigated as a tool to easily identify crosslinked peptides by their highly reproducible and characteristic fragmentation patterns in the negative ion mode. MS3 analysis of the product anions allows easy sequencing and identification of crosslinking sites. Preliminary investigations validate these reagent as a tools to readily identify chemical crosslinks within proteins and their complexes, demonstrating that this approach is an effective and efficient means to determine aspects of the topologies of protein complexes of biological importance. Secondly, the use of several biophysical methods is described to probe the structures of a variety of complexes involving the regulatory protein calmodulin (CaM) with bioactive amphibian peptides. CaM is ubiquitous in nature and plays a regulatory role in numerous biological processes, including some in amphibians and their predators; for example, it is involved in the upregulation of nitric oxide synthesis in vivo. Isothermal titration calorimetry was used to investigate the specific heats of the interactions, ion mobility-mass spectrometry was used to investigate the changes in collision cross section that occur as a result of complexation and nuclear magnetic resonance spectroscopy was used to track chemical shift changes upon binding. The results obtained confirm that these complexes adopt canonical collapsed structures and demonstrate the strength of the interaction between the peptides and CaM. Next, work is presented which investigated the abilities of several bioactive amphibian peptides to inhibit fibril formation by disease related proteins. The peptide caerin 1.8 and several synthetic modifications were tested for their ability to inhibit fibril formation by the Alzheimer’s related amyloid-β (1-42) peptide. The results obtained show that caerin 1.8 redirects the aggregation process of amyloid-β (1-42) toward the amorphous aggregation pathway. In addition, the self-assembly properties of the antimicrobial peptide uperin 3.5 were investigated using a variety of biophysical techniques, including transmission electron microscopy, ion mobility-mass spectrometry, circular dichroism, thioflavin T binding and cell viability assays. Similarities were observed between the fibrils formed by this peptide and those of disease related proteins, supporting the notion that information can be obtained about disease related amyloid fibril formation by studying amyloidogenic host-defence peptides. Lastly, work detailing the effect of aspartic acid (Asp) isomerisation to isoAsp on the structure, activity and proteolytic cleavage susceptibility of three amphibian peptides, Crinia angiotensin II, uperin 1.1 and citropin 1.1 is presented. isoAsp formation has been shown to occur naturally as a result of age-related protein degradation, and is a consideration when preparing formulations of peptide therapeutics. isoAsp formation causes a ‘kink’ in the normally helical structure of citropin 1.1, as determined by nuclear magnetic resonance spectroscopy, which results in a reduction of its antimicrobial activity. The effect of this isomerisation process on the smooth muscle activities of Crinia angiotensin II and uperin 1.1 was different, with Asp isomerisation in Crinia angiotensin II causing a decrease in activity, and Asp isomerisation in uperin 1.1 causing greater contraction at lower concentrations. Proteolytic cleavage with trypsin was identical for each pair of Asp/isoAsp isomers, whilst cleavage with α-chymotrypsin was different for the two Asp/isoAsp citropin 1.1 isomers due to the presence of isoAsp adjacent to the cleavage site.Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, 2013.
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Wabnitz, Paul Andrew. "Chemistry and medical implications of novel amphibian peptides : a thesis submitted for the degree of Doctor of Philosophy / by Paul Andrew Wabnitz." Thesis, 1999. http://hdl.handle.net/2440/19494.
Повний текст джерелаАнотація:
Copies of author's previously published articles inserted.Includes bibliographical references.
xv, 210 leaves : ill. ; 30 cm.
A chemical and pharmacological investigation of compounds derived from amphibian skin. Isolates novel amphibian peptides and further investigates the biological activity of some of the peptides discovered.
Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2000
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Moreira, Anabela Durães de Sousa. "Two birds, one study: evaluating the therapeutic potential of amphibian ocellatin-PT4 and -PT9 peptides for application in leishmaniasis and neuroinflammation-related diseases." Master's thesis, 2019. https://hdl.handle.net/10216/123262.
Повний текст джерела
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Moreira, Anabela Durães de Sousa. "Two birds, one study: evaluating the therapeutic potential of amphibian ocellatin-PT4 and -PT9 peptides for application in leishmaniasis and neuroinflammation-related diseases." Dissertação, 2019. https://hdl.handle.net/10216/123262.
Повний текст джерела
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Jackway, Rebecca Jo. "Biologically active peptides from Australian amphibians." Thesis, 2008. http://hdl.handle.net/2440/62877.
Повний текст джерелаАнотація:
Amphibians secrete potent host defence compounds from dorsal glands onto the skin when stressed, sick or under attack by predators and microbials. Many of these defence compounds, such as biologically active peptides, provide potential targets for new biotechnological and therapeutic investigation. The research presented in this study focuses on the isolation and investigation of peptides from Australian frogs of the genera Litoria and Crinia and endeavours to determine the biological activity and important structural and mechanistic features of these biological compounds.
Isolation and identification of the skin peptide profile of the Eastern Dwarf Tree Frog Litoria fallax has revealed a number of novel peptides named fallaxidins. This frog species is quite unique in that it does not secrete a peptide that displays potent broad spectrum antimicrobial activity nor a peptide that inhibits nitric oxide formation through the enzyme neuronal nitric oxide synthase. Instead it secretes several narrow spectrum antimicrobial peptides, including fallaxidin 3.1. In addition, there are numerous small peptides displaying unique primary structures with unknown biological function. Interestingly, L. fallax produces a skin peptide profile that is quite distinct from the skin peptide profiles of other related Litoria species.
The majority of anurans from the Litoria genus contain at least one peptide in their skin secretion that inhibits the enzyme neuronal nitric oxide synthase. These peptides exert this action by preventing the association of the regulatory cofactor Ca²⁺ calmodulin to the enzyme binding site. The non-covalent binding of the potent neuronal nitric oxide synthase inhibitor dahlein 5.6 (L. dahlii) to calmodulin in the presence of Ca²⁺ is confirmed by electrospray ionisation mass spectrometry. A peptide-protein complex was observed in the gas-phase with a 1:1:4 calmodulin/dahlein 5.6/Ca²⁺ stoichiometry. In addition, the structure and binding interactions have been investigated by means of nuclear magnetic resonance spectroscopy. These experiments illustrated that upon binding dahlein 5.6, Ca²⁺ calmodulin undergoes a substantial conformational transition towards a globular complex with the helical dahlein 5.6 engulfed in a hydrophobic channel.
Typically, the granular secretion of amphibians contains numerous peptides that exert activities in the central nervous system, termed neuropeptides. The biological activities, in particular smooth muscle action, proliferation of lymphocytes and opioid action are investigated to provide insight into the role of these peptides in the host defence. The structure activity relationships of disulfide peptides, caerulein peptides, tryptophyllins, rothein 1 and its related synthetically modified peptides has identified several important structural features essential for their corresponding biological function.
Peptides from the granular secretion of anurans are synthesized within and released from larger precursors molecules. The genes that encode for the skin peptides of Crinia riparia and several Litoria species were isolated and identified. The cDNA sequence of the precursors provides a mechanism by which the evolution of amphibian species can be traced and information about the relationships existing among closely or distantly related species be obtained. All prepropeptides isolated from the Litoria species illustrated sequence homology to those isolated from numerous ranid and hylid frogs and demonstrate that the skin prepropeptides originated from a common ancestral gene. The precursors of peptides from C. riparia are significantly diverse and suggest that these prepropeptides either originated from the same common ancestral gene but have undergone substantial divergent evolution relative to the ranid and hylid frogs or that they have originated from distinct ancestral genes.Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, 2008
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Fu, Hung-Jiang, and 傅宏江. "The structure-specificity relationship study of amphibian peptide pheromones." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/79186566391922948853.
Повний текст джерелаАнотація:
碩士朝陽科技大學
應用化學系碩士班
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Three female newt attracting decapeptide pheromones-sodefrin, silefrin and V8-sodefrin, demonstrate significant difference in their species-specificity. We investigated the conformation of the three peptide pheromones under different environments through circular dichroism, nuclear magnetic resonance and molecular modeling. It was found that three peptides exist mainly as random coils in aqueous solution, with introduction of SDS micelle, a stabe turn-like conformation can be observed in fragments of Ile2~Lys5 and Asp6~Lys10 in silefrin, and in fragments of Lys5~Leu8 and Asp6~Leu9 in both sodefrin and its analogue V8-sodefrin. It is also found that the conformation of V8-sodefrin is more flexible than that of native sodefrin. Our results suggest that the species-specificity of the newt peptide pheromones may be triggered by their structural variations.
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ARRULO, Miriam Raquel Figueiredo. "Antibacterial, antiparasitic and anticancer properties of host-defence peptides from argentinian amphibians." Master's thesis, 2019. http://hdl.handle.net/10362/116369.
Повний текст джерелаАнотація:
Os péptidos de defesa do hospedeiro (PDH) são geralmente moléculas curtas, anfipáticas e catiónicas que fazem parte do sistema imune inato da maioria dos organismos multicelulares. Inicialmente descritos como péptidos antimicrobianos (PAMs) devido à interação e destruição de paredes celulares bacterianas que são naturalmente aniónicas, contudo, estudos recentes mostraram que os PDH possuem uma gama de ação mais variada sendo capazes de interagir com células cancerígenas e podendo assim também ser designados de péptidos anticancerígenos (PACs).
O aumento da multirresistência a fármacos, juntamente com a baixa taxa de descoberta de novos compostos e o facto de os tratamentos atualmente utilizados na terapêutica de várias doenças poderem ser abrasivos e até prejudiciais aos seres humanos, culminaram na necessidade urgente de estudar novas alternativas como os PDH.
Várias espécies de anfíbios Patagónicos adaptaram-se a sobreviver em condições climáticas adversas, habitando zonas áridas ou semiáridas da Patagónia. A pele destes anfíbios produz uma secreção protetora a partir da qual os PDH foram extraídos, identificados e sintetizados nos péptidos PSo-4, PSo-7, PSo2-2, Thau-3 e Ooc-1.
O objetivo deste trabalho foi caracterizar as propriedades antimicrobianas e anticancerígenas dos referidos péptidos e a sua estrutura em solução e na presença de vesículas lipídicas.
A atividade antimicrobiana bem como a interação com membranas bacterianas foram avaliadas em bactérias Gram-positivas e -negativas por determinação da concentração mínima inibitória e através de microscopia de força atómica. Foram ainda realizados ensaios antiparasitários em formas sanguíneas, tipo selvagem, de Trypanosoma brucei brucei, ao passo que estudos anticancerígenos foram praticados em células Huh-7 de carcinoma hepatocelular humano através de métodos fluorimétricos e de absorção respetivamente. A caracterização da conformação dos péptidos, quando em meio aquoso ou em solução contendo vesículas lipídicas POPC:POPG, foi realizada por ensaios de espectrofluorometria e de dicroísmo circular.
PSo-4, PSo-7, Thau-3 e Ooc-1 exibiram atividade antimicrobiana, mas apenas contra E. coli. PSo-4 demonstrou a atividade mais forte enquanto Ooc-1 provou ser bactericida. A análise por AFM apoia a hipótese de que a ação destes péptidos possa ocorrer ao nível da parede celular bacteriana, ou potencialmente interferindo com vias ou alvos intracelulares, culminando na desintegração da célula. Resultados preliminares também indicam que o péptido Ooc-1 exerce efeitos inibitórios no parasita T. b. brucei. Além disso, os péptidos Pso-7, Pso-4 e PSo2-2 revelaram potencial nocivo contra células Huh-7. Estruturalmente, a maioria dos péptidos apresentou propensão à agregação, quando em solução, e estrutura secundária com algum conteúdo de α-hélice, contrariamente a PSo-7 e PSo-4 que mantiveram uma disposição aleatória e baixos níveis de agregação.
Tendo em consideração o comportamento e raio de ação demonstrados, é nossa convicção de que estes péptidos seriam dignos candidatos a investigação adicional e possível manipulação a nível da sua sequência, com o fim de aperfeiçoar as capacidades demonstradas de modo a abrir um caminho viável de desenvolvimento farmacológico.Host-defence peptides (HDPs) are usually short, cationic and amphipathic molecules that are part of the innate immune system of most multicellular organisms. Initially described as antimicrobial peptides (AMPs) due to their interaction and destruction of bacterial cell walls which are naturally anionic, however, recent studies have shown that HDPs have a broader range of action being able to interact with cancer cells and may therefore also be referred to as anticancer peptides (ACPs). Increasing worldwide multidrug resistance (MDR) together with the low discovery rate of new drugs and the fact that the current treatments used in the therapy of various diseases can be very harsh and damaging to human beings, culminated in an urgent need to study new alternatives such as HDPs. Several species of Patagonian amphibians have adapted to survive in adverse climatic conditions, inhabiting arid or semi-arid zones of Patagonia. The skin of these amphibians produces a protective secretion from which the HDPs were extracted, identified and synthesized into peptides PSo-4, PSo-7, PSo2-2, Thau-3 and Ooc-1. The aim of this work was to characterize the antimicrobial and anticancer properties of the peptides mentioned as well as their structure in solution and in the presence of lipid vesicles. Antimicrobial activity and interaction with bacterial membranes were assessed in Gram-positive and Gram-negative bacteria by minimal inhibitory concentration determination and atomic force microscopy. In addition, antiparasitic assays were carried out on wild-type bloodstream forms of Trypanosoma brucei brucei while anticancer studies were performed on human hepatocellular carcinoma Huh-7 cells through fluorescence and absorption spectrophotometry methods respectively. The characterization of the peptides conformation when in aqueous medium or in a solution containing POPC:POPG lipid vesicles was done via spectrofluorometric and circular dichroism assays PSo-4, PSo-7, Thau-3 and Ooc-1 exhibited antimicrobial activity but only against the Gram-positive bacteria E. coli. PSo-4 showed the strongest activity while Ooc-1 proved to be bactericidal. Analysis by AFM supports the hypothesis that the action of these peptides may occur either at the bacterial cell wall level or by potentially interfering with intracellular pathways or targets, culminating in cell disintegration. Preliminary results also indicate that peptide Ooc-1 exerts inhibitory effects on the parasite T. brucei brucei. Furthermore, peptides PSo-7, PSo-4, and PSo2-2 revealed deleterious capacity against Huh-7 cells. Structurally most peptides exhibited a propensity for aggregation, when in solution, and presented a secondary structure with some α-helix content, except for PSo-7 and PSo-4 that maintained a random coil arrangement and lower aggregation levels. Considering the behaviour and scope of action demonstrated, we believe these peptides to be worthy candidates for further investigation and possible sequence manipulation to enhance their demonstrated capabilities in order to open the path of pharmacological viability.
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Pukala, Tara Louise. "Structural and mechanistic studies of bioactive peptides." 2006. http://hdl.handle.net/2440/37851.
Повний текст джерелаАнотація:
Venoms, toxins and host-defence systems constitute rich sources of biologically active molecules, many of which have enormous therapeutic and biotechnological potential. In particular, peptides are often a significant component of these chemical arsenals, and are fundamentally important as biological effector molecules. The research presented in this thesis is centred on the isolation and investigation of peptides from both frogs and spiders, and endeavours to probe the important structural and mechanistic features of these bioactive compounds. The skin peptide profiles of interspecific hybrids between the green tree frog Litoria caerulea and the magnificent tree frog Litoria splendida have been investigated in a ninemonth survey. Fourteen peptides were characterised primarily using mass spectrometry, of which three had not been identified previously in the skin secretions of either parent. A number of these peptides are antibacterial agents, while others effectively inhibit the formation of nitric oxide by neuronal nitric oxide synthase. Implications for the genetics and expression of amphibian dermal peptides are also discussed. The majority of frogs of the genus Litoria contain at least one peptide in their glandular secretion capable of inhibiting the formation of nitric oxide by the enzyme neuronal nitric oxide synthase. This was proposed to occur by preventing the association of the regulatory cofactor, Ca²⁺ -calmodulin, with its binding site on the enzyme. Non-covalent binding of the amphibian peptides to calmodulin in the presence of Ca²⁺ has been confirmed using electrospray ionisation mass spectrometry, by the observation of complexes in the gas phase with a 1 : 1 : 4 calmodulin / peptide / Ca²⁺ stoichiometry. In addition, the structure and binding interactions of caerin 1.8, a potent nitric oxide synthase inhibitor, have been further probed using mass spectrometry and nuclear magnetic resonance spectroscopy techniques. Recently a number of small, disulfide - containing neuropeptides of the signiferin and riparin families have been characterised from the skin secretion of frogs of the Crinia genus. Of these, signiferin 1 and riparin 1.1 are both ten residue peptides with similar primary sequences, however appear to have a significantly different spectrum of bioactivity. Although both act at cholecystokinin-2 receptors, signiferin 1 is smooth muscle active while riparin 1.1 is not, and instead causes proliferation of lymphocytes. The three-dimensional structures of these peptides were determined using nuclear magnetic resonance spectroscopy and restrained molecular dynamics calculations. Both signiferin 1 and riparin 1.1 adopt β - turn type conformations, however differences in these structures may be responsible for the variation in biological activity noted for these peptides. The dermal secretions of most Australian frogs contain at least one broad-spectrum peptide antibiotic, and often a series of peptides with differing activity to afford greater protection against microbial pathogens. Solid state nuclear magnetic resonance spectroscopy studies were carried out to investigate the interaction of a number of these antibacterial peptides with anionic model membranes, and the results are compared with work previously reported using neutral lipids. It appears the peptides may have a different mode of interaction with the membranes depending upon the charge of the lipid head group. The cupiennin 1 peptides have been identified in the venom of the neotropical wandering spider, Cupiennius salei, and demonstrate potent wide-spectrum antibacterial activity. Primary sequence analysis of these peptides suggests a unique amphipathic structure distinctly different from that of other potentially helical cationic antimicrobial peptides isolated thus far. Using nuclear magnetic resonance spectroscopy and restrained molecular dynamics calculations, cupiennin 1a was found to adopt an α- helical structure with a flexible central hinge region in membrane mimicking solvents. Following this, nuclear magnetic resonance spectroscopy methods were used to further probe the antibacterial and the newly identified neuronal nitric oxide synthase inhibitory activity of this peptide.Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, Discipline of Chemistry, 2006
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Steinborner, Simon Todd. "The observation of evolutionary trends in amphibians and the analysis of negative ion fragmentations in large peptide systems by mass spectrometry / by Simon Todd Steinborner." Thesis, 1997. http://hdl.handle.net/2440/19030.
Повний текст джерелаАнотація:
Copies of author's previously published articles inserted.The aim of this research is to observe the evolutionary relationships within and between frog species, as well as to discover potentially useful medicinal peptides. The two main areas of research of this thesis are the characterisation of peptides from frogs belonging to the genus Litoria and the analysis of negative ion fragmentations from large peptides.
Thesis (Ph.D.) -- University of Adelaide, Dept. of Chemistry, 1997?