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Artykuły w czasopismach na temat "Lactam Based Molecules"
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Bai, Yuchen, Leina Dou, Weilin Wu, Zhimin Lu, Jiaqian Kou, Jianzhong Shen, Kai Wen i Zhanhui Wang. "Anti-Metatype Antibody Screening, Sandwich Immunoassay Development, and Structural Insights for β-Lactams Based on Penicillin Binding Protein". Molecules 26, nr 18 (13.09.2021): 5569. http://dx.doi.org/10.3390/molecules26185569.
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Theoretically, sandwich immunoassay is more sensitive and has a wider working range than that of competitive format. However, it has been thought that small molecules cannot be detected by the sandwich format due to their limited size. In the present study, we proposed a novel strategy for achieving sandwich immunoassay of β-lactams with low molecular weights. Firstly, five β-lactam antibiotics were selected to bind with penicillin binding protein (PBP)2x* to form complexes. Then, monoclonal and polyclonal antibodies against PBP2x*-β-lactams complexes were produced by animal immunization. Subsequently, the optimal pairing antibodies were utilized to establish sandwich immunoassay for detection of 18 PBP2x*-β-lactam complexes. Among them, ceftriaxone could be detected at as low as 1.65 ng/mL with working range of 1–1000 ng/mL in milk. To reveal the detection mechanism, computational chemistry and molecular recognition study were carried out. The results showed that β-lactams with a large size and complex structures maybe conducive to induce conformational changes of PBP2x*, and then exhibit greater possibility of being detected by sandwich immunoassay after combination with PBP2x*. This study provides insights for subsequent investigations of anti-metatype antibody screening and sandwich immunoassay establishment for small-molecule detection.
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Becker, D., M. Botoshansky, N. Gasper, F. H. Herbstein i M. Karni. "2-Phenyl-4-hydroxyphthalazin-1-one: A Benzoannelated Derivative of Maleic Hydrazide". Acta Crystallographica Section B Structural Science 54, nr 5 (1.10.1998): 671–76. http://dx.doi.org/10.1107/s0108768197015760.
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The monoclinic crystals (space group P21/a, Z = 8) of 2-phenyl-4-hydroxyphthalazin-1-one, C14H10N2O2, have two independent molecules (A and B) in the asymmetric unit. Both occur as the lactim–lactam (hydroxy–one) structure, which is also found in the parent molecule maleic hydrazide (both triclinic and monoclinic polymorphs), dichloromaleic hydrazide and luminol (3-aminophthalhydrazide). The molecular arrangement is based on strings of alternating A and B molecules linked by hydroxyl...carbonyl hydrogen bonds, with only van der Waals interactions between adjacent strings. Comparison is made of the measured bond lengths for (monoclinic) maleic hydrazide and values from high-level ab initio calculations, and reasonably good agreement is obtained, with indications of improvements when allowance is made for electron correlation and hydrogen bonding.
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Cox, Robin A. "Lactams in sulfuric acid. The mechanism of amide hydrolysis in weak to moderately strong aqueous mineral acid media". Canadian Journal of Chemistry 76, nr 6 (1.06.1998): 649–56. http://dx.doi.org/10.1139/v98-012.
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Reaction rate constants obtained in moderately concentrated sulfuric acid for the hydrolysis of simple lactams of ring sizes five, six, seven, and eight as a function of acidity and temperature have been analyzed using the excess acidity kinetic method. The basicity constants for these substrates have been recalculated; the 13C NMR spectra used to obtain these values are very sensitive to medium effects. It was found that the basicities of the lactams at 0.003-0.1 M lactam concentration were over half a pK unit more basic than they were at 0.5 M lactam, presumably because of the medium effect. Apart from this, the rate constant results obtained at different times by different groups using different techniques for monitoring the kinetics are in adequate agreement. The excess acidity analysis showed that the kinetics could be fitted according to the "three-water-molecule followed by one-water-molecule" mechanistic scenario previously found, or could just as well be fitted by a "one-water-molecule followed by unknown mechanism" scenario, with the mechanistic change taking place at 50 wt.% sulfuric acid for all the substrates. Other evidence makes the latter seem the more likely possibility of the two, and activation parameters based upon the "one-water-molecule" process were determined. Sufficient data points to enable the unknown mechanism to be established were not present; possible mechanisms applicable in media more concentrated than 50 wt.% sulfuric acid are discussed. Previously obtained values of the parameter r, the number of water molecules involved with the substrate in A2 processes, are now questionable.Key words: amides, lactams, excess acidity, hydrolysis, mechanism.
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Pestana-Nobles, Roberto, Yani Aranguren-Díaz, Elwi Machado-Sierra, Juvenal Yosa, Nataly J. Galan-Freyle, Laura X. Sepulveda-Montaño, Daniel G. Kuroda i Leonardo C. Pacheco-Londoño. "Docking and Molecular Dynamic of Microalgae Compounds as Potential Inhibitors of Beta-Lactamase". International Journal of Molecular Sciences 23, nr 3 (31.01.2022): 1630. http://dx.doi.org/10.3390/ijms23031630.
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Bacterial resistance is responsible for a wide variety of health problems, both in children and adults. The persistence of symptoms and infections are mainly treated with β-lactam antibiotics. The increasing resistance to those antibiotics by bacterial pathogens generated the emergence of extended-spectrum β-lactamases (ESBLs), an actual public health problem. This is due to rapid mutations of bacteria when exposed to antibiotics. In this case, β-lactamases are enzymes used by bacteria to hydrolyze the beta-lactam rings present in the antibiotics. Therefore, it was necessary to explore novel molecules as potential β-lactamases inhibitors to find antibacterial compounds against infection caused by ESBLs. A computational methodology based on molecular docking and molecular dynamic simulations was used to find new microalgae metabolites inhibitors of β-lactamase. Six 3D β-lactamase proteins were selected, and the molecular docking revealed that the metabolites belonging to the same structural families, such as phenylacridine (4-Ph), quercetin (Qn), and cryptophycin (Cryp), exhibit a better binding score and binding energy than commercial clinical medicine β-lactamase inhibitors, such as clavulanic acid, sulbactam, and tazobactam. These results indicate that 4-Ph, Qn, and Cryp molecules, homologous from microalgae metabolites, could be used, likely as novel β-lactamase inhibitors or as structural templates for new in-silico pharmaceutical designs, with the possibility of combatting β-lactam resistance
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Twamley, Brendan, Niamh M. O'Boyle i Mary J. Meegan. "Azetidin-2-ones: structures of antimitotic compounds based on the 1-(3,4,5-trimethoxyphenyl)azetidin-2-one core". Acta Crystallographica Section E Crystallographic Communications 76, nr 8 (3.07.2020): 1187–94. http://dx.doi.org/10.1107/s2056989020008555.
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A series of related substituted 1-(3,4,5-trimethoxyphenyl)azetidin-2-ones have been characterized: 3-(4-fluorophenyl)-4-(4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one, C25H24FNO5 (1), 3-(furan-2-yl)-4-(4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one, C23H23NO6 (2), 4-(4-methoxyphenyl)-3-(naphthalen-1-yl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one, C29H27NO5 (3), 3-(3,4-dimethoxyphenyl)-4-(4-methoxyphenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one, C27H29NO7 (4) and 4,4-bis(4-methoxyphenyl)-3-phenyl-1-(3,4,5-trimethoxyphenyl)azetidin-2-one, C32H31NO6 (5). All of the compounds are racemic. The lactam and 3,4,5-trimethoxyphenyl rings are approximately co-planar and the orientation of the lactam and the 4-methoxyphenyl substituent is approximately orthogonal. The chiral centres, although eclipsed by geometry, have torsion angles ranging from −7.27 to 13.08° for the 3 position, and −8.69 to 13.76° for the 4 position of the β-lactam. The structures display intramolecular C—H...O bonding between the 3,4,5-trimethoxyphenyl ring and the lactam ketone. Further C—H...O interactions are observed and form either an opposing methoxy `buckle' to join two molecules together or a cyclic dimer.
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Shiri, Pezhman. "Novel Hybrid Molecules Based on triazole-β-lactam as Potential Biological Agents". Mini-Reviews in Medicinal Chemistry 21, nr 5 (2021): 536–53. http://dx.doi.org/10.2174/18755607mtewaotyn5.
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Molteni, Elena, Giovanni Onida, Matteo Ceccarelli i Giancarlo Cappellini. "Ab Initio Spectroscopic Investigation of Pharmacologically Relevant Chiral Molecules: The Cases of Avibactam, Cephems, and Idelalisib as Benchmarks for Antibiotics and Anticancer Drugs". Symmetry 13, nr 4 (3.04.2021): 601. http://dx.doi.org/10.3390/sym13040601.
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The ability to accurately measure or predict several physicochemical properties of molecules which play a role as active substances in drugs can be of strategic importance for pharmacological applications, in addition to its possible interest in fundamental research. Chirality is a relevant feature in the characterization of drug molecules: enantiomers can show different pharmacological activity and adverse effects. The ability to separate stereoisomers and to assign their absolute configuration can thus be crucial. Circular dichroism (CD) spectra are a useful tool to distinguish between enantiomers. In this work we apply an in-house developed code, based on an efficient DFT approach for circular dichroism, to fully characterize the molecular optical properties in the case of few selected fundamental molecules for current medical and pharmaceutical research, namely avibactam, as representative of non β-lactam inhibitors, two cephems (cefepime and cefoxitin), as examples of β-lactam antibiotics, and idelalisib, as a recent relevant anticancer active substance to treat major leukemias. For the above molecules, in addition to their optical absorption spectra, we calculate their CD spectra within state-of-the-art computational techniques. We then investigate both the conformational and chemical sensitivity of absorption and CD spectra for the chosen molecules. The outcomes of the present research could be of fundamental importance to gain additional information on molecules involved in therapeutic protocols for severe diseases or in drug design.
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Kurmaz, Svetlana V., Natalia V. Fadeeva, Vladislav M. Ignat’ev, Vladimir A. Kurmaz, Sergei A. Kurochkin i Nina S. Emel’yanova. "Structure and State of Water in Branched N-Vinylpyrrolidone Copolymers as Carriers of a Hydrophilic Biologically Active Compound". Molecules 25, nr 24 (18.12.2020): 6015. http://dx.doi.org/10.3390/molecules25246015.
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Hydrated copolymers of N-vinylpyrrolidone (VP) with triethylene glycol dimethacrylate as a promising platform for biologically active compounds (BAC) were investigated by different physical chemical methods (dynamic light scattering, infrared spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry) and the quantum chemical modeling of water coordination by the copolymers in a solution. According to the quantum chemical simulation, one to two water molecules can coordinate on one O-atom of the lactam ring of VP units in the copolymer. Besides the usual terminal coordination, the water molecule can form bridges to bind two adjacent C=O groups of the lactam rings of VP units. In addition to the first hydration shell, the formation of a second one is also possible due to the chain addition of water molecules, and its structure depends on a mutual orientation of C=O groups. We showed that N,N-dimethylbiguanidine hydrochloride (metformin) as a frontline drug for the treatment of type 2 diabetes mellitus can be associated in aqueous solutions with free and hydrated C=O groups of the lactam rings of VP units in studied copolymers. Based on the characteristics of the H-bonds, we believe that the level of the copolymer hydration does not affect the behavior and biological activity of this drug, but the binding of metformin with the amphiphilic copolymer will delight in the penetration of a hydrophilic drug across a cell membrane to increase its bioavailability.
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Shlaes, D. M., i C. Currie-McCumber. "Mutations altering substrate specificity in OHIO-1, and SHV-1 family β-lactamase". Biochemical Journal 284, nr 2 (1.06.1992): 411–15. http://dx.doi.org/10.1042/bj2840411.
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The OHIO-1 beta-lactamase does not normally hydrolyse oxyimino-beta-lactam substrates like cefotaxime, ceftriaxone, ceftazidime or aztreonam. We were able to select spontaneous mutants of an OHIO-1-bearing strain of Escherichia coli using the antibiotic substrates listed above by enrichment methods of frequencies of 10(-8)-10(-10) for all antibiotics except ceftazidime (frequency less than 10(-10)). Most mutants with increased resistance to the other beta-lactams were also more resistant to ceftazidime. Mutations identified by DNA sequencing included a Gly238----Ser238 substitution identical with the SHV-2 mutation previously described, cysteine and valine substitutions at the identical site, and a Gly242----Cys242 substitution. The Cys238 and Cys242 mutant enzymes had less affinity for aztreonam than had the other mutant enzymes. Hydrolysis of cefotaxime, but not cephaloridine, by the cysteine-substituted enzymes was inhibited by p-chloromercuribenzoate. The mutant enzymes had, in general, greater affinity for the mechanism-based inhibitors sulbactam, clavulanic acid and tazobactam. These results suggest two non-mutually exclusive hypotheses for the structural role of substitutions in this area of the enzyme. Either potential hydrogen-bond donors, such as serine and cysteine, interact directly with the beta-lactam molecules, or the steric bulk of these substitutions distorts the beta-pleated sheet such that the beta-lactam is held in a position favourable for stable binding and catalysis. Finally, our data raise questions about a strategy relying on oligonucleotide-probe technology to detect such mutations, because of the variety of substitutions that give rise to similar phenotypes.
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Maity, Arindam, Sarmi Sardar, Shilpa Chatterjee, Nripendra Nath Bala, Sudhan Debnath i Debanjan Sen. "De-Novo Design of Hits Against New Delhi Metallo-β-Lactamase Enzyme". International Journal of Quantitative Structure-Property Relationships 7, nr 2 (kwiecień 2022): 1–13. http://dx.doi.org/10.4018/ijqspr.290010.
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The New Delhi Metallo-β-lactamase 1 (NDM-1) is a class of Metallo-β lactamase enzyme. It is responsible for hydrolyzing almost all β-lactam antibiotics, leading to multi-drug resistance in bacteria. The lack of specific therapeutic options against this target creates an emerging need to develop new molecules against it. The multistep fragment- and knowledge-based de-novo design methods were considered for this study to design small molecules. The designed molecules were evaluated by molecular docking and dynamics simulation, followed by drug-likeness prediction. This study reports that a new drug-like chemical entity exhibits good binding behavior against the MDM-1 enzyme. Nonetheless, in-depth biological evaluation is required to determine the efficacy of the designed binders to develop new therapeutics against NDM-1.
Rozprawy doktorskie na temat "Lactam Based Molecules"
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Nichols, Derek Allen. "Structure-Based Design of Novel Inhibitors and Ultra High Resolution Analysis of CTX-M Beta-Lactamase". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5284.
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The emergence of CTX-M class-A extended-spectrum β-lactamases, which confer resistance to second and third-generation cephalosporins, poses a serious health threat to the public. CTX-M β-lactamases use a catalytic serine to hydrolyze the β-lactam ring. Specifically, the hydrolysis reaction catalyzed by CTX-M β-lactamase proceeds through a pre-covalent complex, a high-energy tetrahedral acylation intermediate, a low-energy acyl-enzyme complex, a high-energy tetrahedral deacylation intermediate after attack via a catalytic water, and lastly, the hydrolyzed β-lactam ring product which is released from the enzyme complex. The crystallographic structure of CTX-M at sub-angstrom resolution has enabled us to study enzyme catalysis as well as perform computational molecular docking in our efforts to develop new inhibitors against CTX-M. The goal of this project was to determine the hydrogen bonding network and proton transfer process at different stages of the reaction pathway as well as develop novel inhibitors against CTX-M β-lactamases. The results I have obtained from the project have elucidated the catalytic mechanism of CTX-M β-lactamase in unprecedented detail and facilitated the development of novel inhibitors for antibiotic drug discovery.
The first aim of the project focused on developing high affinity inhibitors against class A β-lactamase using a structure-based drug discovery approach, which ultimately led to the identification of CTX-M9 inhibitors with nanomolar affinity. Compound design was based on the initial use of computational molecular docking results along with x-ray crystal structures with known inhibitors bound in the active site. In addition, chemical synthesis was used to build and extend the existing inhibitor scaffold to improve affinity to CTX-M9 and related serine β-lactamases. Through a fragment-based screening approach, we recently identified a novel non-covalent tetrazole-containing inhibitor of CTX-M. Structure-based design was used to improve the potency of the original tetrazole lead compound more than 200-fold with the use of small, targeted structural modifications. A series of compounds were used to probe specific binding hotspots present in CTX-M. The designed compounds represent the first nM-affinity non-covalent inhibitors of a class A β-lactamase. The complex structures of these potent compounds have been solved using high resolution x-ray crystallography at ~ 1.2-1.4 Å, which provides valuable insight about ligand binding and future inhibitor design against class A β-lactamases.
Specifically, the first aim of the project was to use ultra-high resolution x-ray crystallography to study β-lactamase catalysis. Through the use of ultra-high resolution x-ray crystallography with non-covalent and covalent inhibitors, I was able to structurally characterize the critical stages of the enzyme mechanism. Here we report a series of ultra-high resolution x-ray crystallographic structures that reveal the proton transfer process for the early stages of the class A β-lactamase catalytic mechanism. The structures obtained include an a 0.89 Å crystal structure of CTX-M β-lactamase in complex with a recently-developed 89 nM non-covalent inhibitor, and a 0.80 Å structure in complex with an acylation transition state boronic acid inhibitor. Nearly all the hydrogen atoms in the active site, including those on the ligand, polar protein side chains and catalytic water, can be identified in the unbiased difference electron density map. Most surprisingly, compared with a previously determined 0.88 Å apo structure determined under the same conditions, the hydrogen-bonding network has undergone a series of reshuffling upon the binding of the non-covalent ligand. Two key catalytic residues, Lys73 and Glu166, appear to have both changed from a charged state to being neutral. Interestingly, structural evidence suggests the presence of a low barrier hydrogen bond (LBHB) shared between Lys73 and Ser70. These unprecedented detailed snapshots offer direct evidence that ligand binding can alter the pKa's of polar protein side chains and their affinities for protons. Such effects can be a common mechanism utilized by enzymes to facilitate the proton transfer process of a reaction pathway. They also have important implications for computational modeling of protein-ligand interactions. Ultra-high resolution x-ray crystallography allowed us to determine the hydrogen atom positions for key active site residues involved in catalysis. As a result, the ability to characterize the hydrogen bonding network led to the determination of the specific proton transfer process that occurs during the reaction stages of the CTX-M β-lactamase mechanism. Overall, the results from this project demonstrate the effectiveness of using ultra high resolution x-ray crystallography as a useful tool to study enzyme catalysis as well as develop and discover novel inhibitors.
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Chien-Hsien, Kuo. "Molecular phylogeny and evolution of hagfish based on mtDNA and lactate dehydrogenase genes". 2000. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0021-2603200719104655.
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Kuo, Chien-Hsien, i 郭建賢. "Molecular phylogeny and evolution of hagfish based on mtDNA and lactate dehydrogenase genes". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/03269412909281228290.
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博士國立臺灣師範大學
生物研究所
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Abstracts The study included molecular phylogeny of hagfish and evolution of lactate dehydrogenase. The mitochondrial DNA sequences from the large ribosomal RNA gene may be of great value for systematic and phylogenetic studies within families. Partial sequences of the 16S rRNA gene were obtained for comparisons among the following hagfish species, Paramyxine nelsoni, P. sheni, P. taiwanae, P. yangi, P. cheni, Eptatretus burgeri, E. stouii, E. cirrhatus, Myxine glutinosa, M. formosana, M. circifrons, M. sp1 and M. sp2. The boundary of first four Paramyxine species from 16S rRNA sequences is ambiguous; however, they are valid based on our further unpublished isozyme data as well as the gill aperture arrangement pattern. The present molecular data show that the genus Paramyxine is polyphyletic. Eptatretus and Paramyxine form a clade, but their included species can be grouped separately into two different subfamilies, the Myxininae and Eptatretinae. The phylogenetic pattern is not congruent with the number of branchial pouches or branchial apertures proposed by Nelson (1994) and Fernholm (1998), who addressed the evolutionary trend of hagfish as being from polybranchiates to monobranchiates and with all hagfish belonging to a monophyletic group. Furthermore, the larger genetic distance between P. cheni and the other Eptatretinae species suggest that P. cheni could be as a basal taxa in Eptatretinae. A new genus and species of Rubicundus oligoporos collected from the northeastern coast of Taiwan is described here. Rubicundus is distinguished by pink body coloration. Rubicundus oligoporos is a five-gilled species with a three-cusp multicusp on the anterior rows and a two-cusp one on the posterior rows. The putative taxonomic position of Rubicundus is discussed based on mitochondrial 16S rRNA gene fragment sequences. In order to understand the expression of the multiple LDH isozymes in aves, the brain, eye, heart, liver, muscle, and testis were analyzed. Horizontal starch gel electrophoresis was used to examine isozymes of L-lactate dehydrogenase in 4 families and 7 genera of lizards and 33 aves species assigned to 6 orders. Like all other vertebrates, bords possess 2 fundamental LDH loci (LDH-A and LDH-B). A LDH-C product of the third locus was detected in only 8 species of birds and 4 lizards and, for the first time, was reported from the Passeriformes and lizards. The results of this study and those of other previous research suggest that avian LDH-C, reptile LDH-C, and mammalian LDH-C may be orthologous, and may have been derived from ancestor amniote LDH-A. The present study has determined a cDNA sequence of LDH-A from the muscle of hagfish, it contains 1428 nucleotides including a protein-encoding sequences of 1026 nucleotides, the 5’(54 nucleotides) and 3’ (342 nucleotides) untranslated region. The hagfish LDH-A protein that we deduced from the nucleotide sequence is 341 amino acids long. Compared to the other vertebrate LDH, the sequence added 8 amino acids in the low hydrophobicity region at position 220-227. Hagfish LDH unique 9 positions exhibit alternative amino acid those conserved in all vertebrates. None of the alternative amino acids positions makes up the active center. Of the 10 positions that are diagnostic for LDH-A versus LDH-B in the gnathostome vertebrate examined, the hagfish LDH-A sequence resemble LDH-A at four, LDH-B at two, and neither at four. Hagfish LDH, like that of the all vertebrate LDH-As is also missing an amino acid at the penultimate position. The hagfish sequence, with its greater similarity to chordate LDH-A sequence in this region, provides additional evidence that the amino acid was added in the common ancestor of LDH-Bs. Our phylogenetic conclusions that LDH of hagfish muscle is a ancestral LDH-A and the lamprey single locus condition is due to gene loss. Both distance and maximum parsimony analysis strongly reject a relationship of hagfish LDH-A with lamprey LDH.
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Barbosa, João Alberto Cunha. "Development of a poly(L-Lactic acid) based drug release system". Master's thesis, 2015. http://hdl.handle.net/1822/41125.
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Dissertação de mestrado em Biofísica e BionanossistemasNanomedicine and controllable drug delivery systems have recently initiated their way into therapeutics. Faulty and, many times, ineffective approaches that conventional medicine uses need to be replaced by novel and smart materials that assure that a drug is delivered in the right place, at the right time. Polymeric materials are now widely used to produce drug delivery vehicles with tunable characteristics and, if needed, triggered releases. Although several polymeric materials are already being used to produce drug delivery systems it is, however, necessary to reach an active control of the drug release rate. Hence, the addition of a stimuli-sensitive component to the system that could trigger or increase the drug release rate would be of great interest. Therefore, during this work a polymeric platform containing a drug carrier (zeolite) and a stimuli-sensitive component (Terfenol-D) was developed. Firstly, a theoretical and experimental screening involving different zeolites with different characteristics (structure, crystal size, Si/Al ratio and counter ion) and loading methods with different solvents (hexane, ethanol and acetone) was performed in order to understand their influence in the loading of a model drug – Ibuprofen. Next, preparation of poly(L-lactic acid) membranes was optimized by testing three different polymer concentration. The membranes were prepared by freeze-drying method. Preliminary results from the molecular modelling studies indicated that faujasite and beta polymorph- A structures were the ones allowing a greater displacement of the drug inside the pores. Experimental trials indicated that hexane was the solvent providing greater loadings. From the tested zeolites, the nanosized faujasite (crystal size of ~250nm) was selected due to its complete drug release at 24h. Moreover, membranes prepared with 5(wt/vol.)% presented the best morphological and mechanical characteristics that were maintained after the incorporation of the zeolite and Terfenol-D particles. Comparing the four different drug release systems prepared (loaded zeolites; loaded membranes; membranes with loaded zeolites; and membranes with loaded zeolites and Terfenol-D under magnetic fields) it is clear that the systems present significant differences in the release kinetics and mechanisms. The membranes containing IBU-loaded zeolites appear to present a combination between the release of IBU-loaded membranes and the IBU-loaded zeolites. The release assays with the membranes containing loaded zeolite and Terfenol-D particles confirmed the influence of the applied magnetic fields in the release ratio. When the trigger is applied the Korsmeyer-Peppas model indicates a super case-II transport, indicating that the release of the drug is being driven mostly by a swelling or erosion mechanism, explained by the movement of the magnetostrictive particles when subject to the magnetic field.
A nanomedicina e os sistemas de entrega controlada de fármacos iniciaram recentemente a sua utilização terapêutica. Várias práticas utilizadas pela medicina convencional apresentam diversas limitações e são, muitas vezes, ineficazes, sendo necessária a sua substituição por novos materiais que assegurem que um fármaco é entregue no local certo, no momento adequado. Apesar de vários materiais poliméricos serem já utilizados para produzir sistemas de entrega de fármacos com características moduláveis é no entanto necessário ter um controlo ativo da taxa de libertação. Assim, a adição de um componente sensível a um estímulo que pudesse iniciar ou acelerar a libertação seria uma grande vantagem. Deste modo, neste trabalho foi desenvolvida uma plataforma polimérica contendo um veículo no qual o fármaco esta integrado (zeólito) e um componente sensível a campos magnéticos (Terfenol-D). Inicialmente, foi realizado um estudo teórico e experimental envolvendo diversos zeólitos com diferentes características (estrutura, tamanho do cristal, razão Si/Al e contra-ião) e métodos de incorporação do fármaco usando diferentes solventes (hexano, etanol e acetona), de maneira a entender a influência dos diferentes parâmetros na incorporação de um fármaco modelo – ibuprofeno. Seguidamente, foi otimizada a preparação das membranas de ácido poli(L-láctico) para a incorporação dos restantes componentes, tendo sido testadas quatro concentrações de polímero. Os resultados demonstraram que a as estruturas faujasite e beta polimorph-a foram as que apresentaram maior mobilidade para a molécula do fármaco e o hexano mostrou ser o solvente que permite maiores taxas de encapsulação. Dos zeólitos testados, foi selecionado o que apresentava libertação total do seu conteúdo às 24h (faujasite com tamanho de cristal de ~250nm). Os testes às membranas mostraram que a membrana com 5 (m/vol.)% de polímero apresentava as características morfológicas e mecânicas mais adequadas, mantendo-as após a incorporação do zeólito e das partículas de Terfenol-D Comparando as cinéticas de libertação dos quatro sistemas de libertação preparados (zeólitos e membranas carregados; membranas com zeólitos carregados; e membranas com zeólitos carregados e Terfenol-D sob campos magnéticos) claras diferenças são observadas. A libertação de IBU das membranas contendo zeólitos carregados aparenta ser uma combinação das cinéticas de libertação dos zeólitos e das membranas carregados. Os ensaios de libertação com as membranas contendo zeólito e Terfenol- D sob campos magnéticos confirmaram a influência do estímulo na taxa de libertação. O resultado foi um transporte denominado super caso-II, indicando que o mecanismo de libertação é controlado sobretudo pelas variações na matriz polimérica, causada pelo movimento das partículas magnetostritivas.
Części książek na temat "Lactam Based Molecules"
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Delpiccolo, Carina M. L., Maitena Martinez-Amezaga i Ernesto G. Mata. "Recent Approaches Toward the Generation of Molecular Diversity Based on β-Lactam Structures". W Beta-Lactams, 129–62. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55621-5_5.
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Barber, Michael S., Ulrich Giesecke, Arno Reichert i Wolfgang Minas. "Industrial Enzymatic Production of Cephalosporin-Based β-Lactams". W Molecular Biotechnolgy of Fungal beta-Lactam Antibiotics and Related Peptide Synthetases, 179–215. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b99261.
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Coelho-Rocha, Nina D., Fernanda A. L. Barroso, Laísa M. Tavares, Ester S. S. dos Santos, Vasco Azevedo, Mariana M. Drumond i Pamela Mancha-Agresti. "Main Features of DNA-Based Vectors for Use in Lactic Acid and Update Protocols". W Methods in Molecular Biology, 285–304. New York, NY: Springer US, 2020. http://dx.doi.org/10.1007/978-1-0716-0872-2_16.
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Tuzar, Zdeněk. "Molecular Characterization". W Lactam-Based Polyamides, 95–131. CRC Press, 2019. http://dx.doi.org/10.1201/9780367813062-4.
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Le Rouzic, Morgan, Pauline Bruniaux, Cyril Raveschot, François Krier, Vincent Phalip, Rozenn Ravallec, Benoit Cudennec i François Coutte. "Lactobacillus Use for Plant Fermentation: New Ways for Plant-Based Product Valorization". W Lactobacillus - A Multifunctional Genus [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.104958.
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Today, plant production is increasing, but most industrial processes generate a lot of waste and by-products for which, in the current context, it is a priority to recycle or valorize them. One of the cheapest valorization routes is fermentation, in particular lactic fermentation by Lactobacillus species, which produces lactic acid and other molecules of industrial interest such as bioactive compounds such as anthocyanin, organic acid, peptides, or phenol, which are widely found in the plant matrix, mainly in cereals, grass, fruits, and vegetables. Bioactive compounds may exert beneficial health effects, such as antioxidant, anti-inflammatory, antimicrobial, or prebiotic activities. In addition, lactic acid fermentation can improve existing products and lead to new applications in food, livestock feeding and biotechnology, such as the production of lactic acid, protein, or silage. This chapter reviews the use of Lactobacillus strains in the fermentation process of many plant bioresources or by-products through their different bioactivities, active molecules, and applications.
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Zong, Liang, Jingning Zhang, Dan Li, Shaohui Sui, Yanhua Xiao, Jian Li, Meng Liu, Bo Zhuang, Daxue Li i Weihui Wu. "A Rhodamine-Based Probe for Detection of Nerve Agents Simulants". W Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210333.
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In this paper, a rhodamine-based fluorescent and chromogenic probe, N-(Rhodamine B)-lactam-2-aminobenzyl alcohol (RB-AB), was designed to detect nerve agent simulants. We firstly synthesized RB-AB probe by using rhodamine B and 2-aminobenzyl alcohol as main materials. Secondly, the RB-AB probe was applied to evaluate its ability to detect two nerve agent simulants, diethyl chloride phosphate (DCP) and methyl ethyl chloride phosphate (MECP). It was assumed that RB-AB could react with the nerve agent simulants through the benzyl alcohol group and then undergoes structural changes. As a result, the RB-AB detection solution shows fluorescent and color changes during detecting process. The maximum intensity of fluorescence emission increases with the addition of DCP or MECP in a dose-dependent manner. The LOD (limit of detection) of the probe is about 20 ppm for DCP. Moreover, a significant pink color change can be observed in the RB-AB system within a few seconds when detecting DCP or MECP. In conclusion, a rhodamine-based molecule as a fluorescent and chromogenic probe was developed for detecting nerve agent simulants. The RB-AB probe solutions can give rapid and off-on type optical changes including color and fluorescence when reacting with DCP or MECP. We anticipate that RB-AB probe can be used as a helpful tool for visual and fluorescent detection of nerve agents when meeting with terrorist attacks involving with these agents so that effective measures could be promptly taken to cope with the crises.
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Dinodia, Monica. "Greener Approach towards the Synthesis of Nitrogen Based Heterocycles". W Strategies Towards the Synthesis of Heterocycles and Their Applications [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108489.
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The preferable application of green chemistry in research is to utilize environment benign, mild, non toxic, reproducible catalyst and efficient solvents in synthesis of molecules. Use of green chemistry techniques had enabled in dramatically reducing chemical waste and reaction times as has recently been reported in several organic syntheses reactions. Greener routes are required in the synthesis of N-heterocycles, due to the remarkable importance of these compounds in medicinal chemistry. This chapter is dedicated to the synthesis of N containing heterocyclic compounds using eco-friendly solvent like water and bio-derived solvents (glycerol, ethyl lactate, and gluconic acid aqueous solution). Water and bio-based solvents for the synthesis of aromatic nitrogen heterocycles was chosen due to the negligible toxicity associated with these solvents. Apart from being eco-friendly, water also has the potential to become a universally acceptable solvent due to its abundance and low cost. Work on microwave synthesis is also reported as it is an eco-friendly and faster process for the synthesis of these N-based heterocyclic compounds. Due to its rapid action to produce products with greater purity and yield, it is now being used worldwide.
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Bhukya, Bhima, Chandrasekhar Banoth, Praveen K. Keshav, MD Saddam Hussain i Shanthipriya Ajmera. "Biotechnological Production of Various Fungal Metabolites and their Applications in White Biotechnology". W Mycology: Current and Future Developments, 255–86. BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815040340122040019.
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The rapid growth of science and technology resulted in an increase in the production and utilization of chemical-based value-added compounds. Due to the involvement of greenhouse gases and global warming, there is a shift towards alternative strategies to replace chemical-based value-added products. Primary and secondary metabolites produced by various microorganisms could be an effective and environmentally friendly alternative to chemically manufactured value-added products. Metabolites produced from various fungal strains (filamentous fungi and yeast) are of high importance for their widespread applications in the food, agriculture, and pharmaceutical sectors. These value-added bioproducts include biofuel (bioethanol), organic acids (citric acid, lactic acid, succinic acid, and cis, cis-muconic acid), hydrolytic enzymes (cellulases, xylanase, phytase, lipase, ligninolytic enzymes, and proteases), vitamins, amino acids, antibiotics, drug molecules, and other industrialrelevant chemicals. Advances in industrial microbiology and biotechnology by metabolic engineering, protein engineering, systems biology, and synthetic biology led to the analysis and discovery of novel metabolic pathways and successive heterologous expression of metabolites of commercial importance. This chapter highlights the biotechnological production of a few relevant primary and secondary metabolites by both filamentous and unicellular fungi.
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Taber, Douglass F. "The Tan/Chen/Yang Synthesis of Schindilactone A". W Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0088.
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Schindilactone A 3 is one of a closely related family of polycyclic lactones that have been used in China for the treatment of rheumatic disease. The synthesis of 3 reported (Angew. Chem. Int. Ed. 2011, 50, 7373) by Ye-Feng Tang of Tsinghua University and Jia-Hua Chen and Zhen Yang of Peking University is an elegant tour of metal-mediated bond construction, as exemplified by the cyclization of 1 to 2. The preparation of 1 began with the Diels-Alder reaction of 4 with the butadiene 5. Addition of methyl magnesium chloride converted 6 to the crystalline lactone 7. Angular hydroxylation followed by ring expansion gave the bromo enone 8, which was homologated to the lactone 11. Apparently, the bulky silyloxy group directed the addition of the butenyl Grignard reagent 10 to the top face of the ketone carbonyl. Hydroxylation of the lactone followed by the addition of 12 then gave 1 as a mixture of diastereomers. Only one of the two diastereomers of 1 could undergo ring-closing metathesis to form the second of the three carbocyclic rings of 3. The two lactol diastereomers were in equilibrium with each other by way of the open-chain enone. When MgBr2 was added to encourage equilibration, the metathesis proceeded to completion to give 2. The tertiary alcohol of 2 was esterified with 2-butynoic acid to give 13. Intramolecular Pauson-Khand cyclization, using the optimized protocol developed by the authors, then delivered the enone 13, completing the last carbocyclic ring of 3. The last remarkable metal-mediated reaction in the synthesis was the oxidative carbonylation of 14 to 15. It is not clear if the postcarbonylation event is direct Pd-mediated C–O bond formation or the intramolecular addition of alkoxide to a transient butenolide. To complete the synthesis, 15 was methylated, then deprotonated and kinetically quenched to set the proper relative configuration of the last methyl group. Remarkably, despite the presence in the molecule of three other acidic protons, including the one that had just been removed and kinetically reset, exposure of the acetate 16 to a large excess of base, followed by oxidation, gave clean conversion to schindilactone A 3.
Streszczenia konferencji na temat "Lactam Based Molecules"
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Rob, Mohammad A., i Frank C. Franceschetti. "Atmospheric Multi-Component Pollution Analysis Using CO2 Laser". W Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/laca.1992.wc7.
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The laser spectroscopic techniques for detecting minor gaseous pollutants of the atmosphere have made rapid advances in the last few years. The most important optical process for detection of air pollutants is based on the extinction of radiation by molecular absorption. Each molecule absorbs light at a particular wavelength or a range of wavelengths, a characteristic of the molecule. Thus a measurement of absorption of light at the molecule's characteristic wavelength produces a mean of determining a particular molecule at the presence of other molecules. Problems can, and often arise from overlapping spectrums due to other molecules of the atmosphere. In this case, it is necessary to identify the molecules which cause these overlappings. In some cases, one might be interested in finding multiple pollutants of the atmosphere.
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Hill, S. C., M. D. Barnes, W. B. Whitten i J. M. Ramsey. "Modeling Fluorescence Collection from Single Molecules in Liquid Microspheres". W Laser Applications to Chemical and Environmental Analysis. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/lacea.1996.lwd.7.
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Optimization of molecular detection efficiencies is of central importance in analytical applications involving single molecule detection.1 In addition to limitations imposed on the fraction of molecules which can be detected by the average signal-to-noise ratio, experimental factors such as excitation inhomogeneity and molecular diffusion conspire to further limit "molecular detectability." Recent single molecule detection experiments in microdroplets suggest that such experimental limitations can be significantly reduced primarily because the molecule cannot diffuse away from the excitation volume. However, unlike fluorescence detection from bulk streams where the fluorescence intensity is isotropic in space, the large refractive index change at the surface of microdroplets implies that the fluorescence intensity collected by a lens will be strongly dependent on the position of the molecule within the droplet. In addition, the same refractive index discontinuity at the droplet surface produces a complicated excitation intensity distribution within the droplet as a result of interference between refracted and totally-internally-reflected rays. Thus, issues such as whether molecules near the surface of the sphere can "hide" from the detector as a result of total internal reflection of emission near the droplet surface, or poor excitation efficiency due to the molecule being located in a "shadow" region of the droplet will have a potential effect on molecular detection efficiencies. These questions are nontrivial to address in a quantitative way. Here we discuss development of numerical tools for modeling the fluorescence collected from a single molecule within a microdroplet as a function of position, orientation, and detection geometry based on the semiclassical electrodynamics formalism developed by Chew2 for light scattering in dielectric microspheres. In addition we also examine effects of excitation inhomogeneity within the sphere, molecular diffusion, and transition rate modification in order to obtain a realistic model of molecular detection efficiencies in microdroplets.
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Lermer, N., M. D. Barnes, C.-Y. Kung, W. B. Whitten i J. M. Ramsey. "High-Speed Single Molecule Detection in Microdroplet Streams". W Laser Applications to Chemical and Environmental Analysis. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/lacea.1996.lwb.7.
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The detection of individual fluorescent molecules in liquids has been of great interest in recent years. Various fluorescence-based techniques shown to provide single molecule sensitivities include confocal microscopy [1], flow cell techniques [2], and levitated microdroplets [3]. The application of the microdroplet technique to single molecule detection offers many advantages. First, fluoresence decay rates and total fluoresence yield have been shown to be enhanced in glycerol microdroplets [4]. Additionally, the droplet confines the single fluorophore to a small volume thereby removing difficulties arising from diffusion of the fluorophore. Furthermore, the discrete detection unit of the droplet is ideally suited to the application of digital molecular detection for the analysis of ultradilute solutions [5]. Previous liquid microdroplet work has exhibited single molecule detection with signal-to-noise ratios in the range of 10-40 [3]. In our previous work, an electrodynamic trap was employed to trap glycerol microdroplets for a period much longer than the average photochemical lifetime, thus obtaining the maximum possible signal from the analyte. However, the application of digital molecular analysis to real systems requires tens of thousands of droplet measurements [5]; the time required to trap (and to size) the droplet in a levitated system prohibits its application in a high-speed molecular counting technique. In addition, many biological applications of single molecule fluorescence detection require aqueous samples. The present work discusses the development of an instrument designed to permit single molecule detection in water microdroplets at count rates in the range of 10 - 1000 Hz.
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Terekhova, M. I., E. V. Rogacheva, I. A. Derevyanchenko i L. A. Kraeva. "WHOLE-GENOME SEQUENCING-BASED ANTIBIOTIC RESISTANCE PROFILE OF LISTERIA MONOCYTOGENES STRAINS FROM SAINT-PETERSBURG AND THE VOLOGDA REGION". W Molecular Diagnostics and Biosafety. Federal Budget Institute of Science 'Central Research Institute for Epidemiology', 2020. http://dx.doi.org/10.36233/978-5-9900432-9-9-109.
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The increasing number of antibiotic-resistant isolates of L. monocytogenes is required to establish a genotypic resistance profile to ensure appropriate antibiotic therapy of listeriosis. In this study, whole-genome sequencing and de novo assembly was performed on L. monocytogenes strains from St. Petersburg and the Vologda region. We obtained the MLST ST, phylogenetic lineage and PCR-serogroups in silico for isolates under the study, revealed genes and mutations associated with antibiotic resistance. In general, the genetic composition was similar between the strains from different regions and included a wide range of antibiotic resistance mechanisms. Listeria strains possessed genes that code for resistance to β-lactam antibiotics, fluoroquinolones, tetracyclines and macrolides, — classes that are commonly used in the treatment of listeria infection. The present study is important in the sanitary and epidemiological surveillance of listeriosis in Russia.
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Willey, K. F., V. Vorsa i N. Winograd. "Molecular Photoionization and Chemical Imaging". W Laser Applications to Chemical and Environmental Analysis. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/lacea.1998.ltub.4.
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It is now possible to desorb a variety of organic molecules from surfaces using a tightly focused energetic ion beam. The molecules are detected as secondary ions using time-of-flight mass spectrometry, and may be spatially resolved by rastoring the ion beam over a larger area. A chemically resolved image is then acquired by examining the intensity of a particular mass as a function of x,y position. Presently, liquid metal ion sources using 25 KeV Ga+ ion projectiles can be focused to a spot of less than 20 nm in diameter. The limiting factor for molecule-specific imaging is sensitivity. The ion dose must be kept less than 1% of the total number of surface molecules to prevent chemical damage. Moreover, the ionization probability of desorbed molecules is generally less than 1 in 104. Since the molecules desorb from the first layer and since there are at most 4 × 106 molecules per square micron (depending on size of course), the signal rapidly approaches zero as the spatial resolution or beam probe size is reduced below 1 micron.1 Here we investigate the use of high intensity 100 fs laser pulses to photoionize the desorbed neutral molecules in an attempt to increase the measurement efficiency of this type of experiment. Our model system is dopamine, an important neurotransmitter that has aromatic character, but is subject to significant fragmentation using ns laser pulses. The results suggest that this approach can indeed expand the performance of mass-spectrometry based imaging experiments and can open new applications in bioimaging.
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Dovichi, Norman J., Shade Wu i Da Yung Chen. "High Sensitivity Fluorescence Detection of Biological Molecules". W Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/laca.1990.tha1.
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Fluorescein is a good fluorescent label for high sensitivity analysis. The molecule has high molar absorptivity, 5 × 104 L mol-1 cm-1 at 488 nm and near unit fluorescence quantum yield in the pH range of 8 to 10. Unfortunately, the molecule is not photostable undergoing irreversible photobleaching after absorbance of about 8,000 photons. Fluorescein may be used to label amino groups in amino acids, peptides, and proteins through the isothiocyanate derivative. Under basic conditions, the thiocarbamoyl derivative is formed, with relatively good stability. The reaction between amino acids and fluorescein isothiocyanate is first order in bod the concentration of amino acid and derivative, with an activation energy of about 16 kcal/mol. Under acidic conditions, the cyclic thiohydantoin derivative is formed, cleaving the terminal amino acid from proteins and peptides. This thiohydantoin derivative possesses greater photostability than the thiocarbamoyl derivative, decomposing after absorbance of about 12,000 photons. The thiocarbamoyl-thiohydantoin derivative series is the basis of an Edmon degradation scheme for protein sequencing. In addition to amino acid labeling, fluorescein may be used to label thiols through the bromobimane derivatives; a high sensitivity DNA analysis is based on this compound. Last, succinylfluorescein labeled chain terminating dideoxynucleotides are used in DNA sequencing, these molecules have similar spectral properties as fluorescein.
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Yeung, Edward S. "Laser Based Analytical Measurements In Liquids". W Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/laca.1987.ma4.
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The use of lasers for detection in liquid chromatography (LC) has been gaining in popularity. The reason is that unique properties of the laser beam fit well with many of the requirements in LC. Fluorescence is one of the widely used laser-based techniques. However, one is often limited by the availability of a fluorophore, the availability of the appropriate laser wavelength, and the poor intensity stability of lasers. A possible solution is to use indirect fluorometry. Because there is always a solvent present in LC, one can include a fluorescent probe in the solvent. There is then a large background fluorescence in the optical region at all times. When analytes elute from the chromatographic system, they can displace the probe molecules to cause a lower fluorescence signal. This then allows fluorometry to be used to detect non-fluorescing species. Since the choice of the fluorophore is governed by some broad guidelines, a convenient laser wavelength can be used. The stability of the laser intensity is critical to detection at low concentrations. Good stability can be achieved in a double-beam arrangement with modulation at high frequencies. To enhance detection, we make use of the competition between the probe molecule and the analyte either by ion exchange or by adsorption on the LC column. Good mass detectability is possible when microbore or open capillary LC columns are used.
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Jett, James H., Lloyd C. Davis, Jong Hoon Hahn, Richard A. Keller, Letitia Krakowski, Babetta Marrone, John C. Martin, Robert Ratliff, Newton K. Seitzinger i E. Brooks Shera. "Single Molecule Detection in Flowing Sample Streams As An Approach to DNA Sequencing". W Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1990. http://dx.doi.org/10.1364/laca.1990.tha3.
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We are exploring a technique which has the potential to sequence large fragments of DNA at a rate of hundreds of bases per second. Our technique is based upon a projected ability to detect single chromophores by laser-induced fluorescence in flowing sample streams.1 The technique involves: (1) labeling the nucleotides with base specific tags suitable for fluorescence detection, (2) selecting a desired fragment of DNA, (3) suspending the single DNA fragment in a flowing sample stream, (4) sequentially cleaving labeled bases from the free end of the DNA fragment using an exonuclease, and (5) detecting and identifying the cleaved, labeled bases as they flow through a focused laser beam.2
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Kudo, Hiroyuki, Yusuke Suzuki, Yoshiki Tojo, Haruna Saito i Keigo Enomoto. "Sweat Lactic Acid Monitoring System using Adhesive Plaster-based Sweat Sampling Device". W 2019 IEEE 14th International Conference on Nano/Micro Engineered and Molecular Systems (NEMS). IEEE, 2019. http://dx.doi.org/10.1109/nems.2019.8915655.
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Hieftje, Gary M. "New Laser-Based Measurements in Analytical Spectrometry: From Remote Testing to Thomson Scattering". W Laser Applications to Chemical Analysis. Washington, D.C.: Optica Publishing Group, 1987. http://dx.doi.org/10.1364/laca.1987.ma5.
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In this presentation, several laser-based procedures and techniques for measuring chemical substances and for characterizing chemical instrumentation will be described. However, greatest emphasis will be placed on describing some new methods for determining the time-dependent characterics of molecules in condensed phase.