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Mohiti, Maziar. „Asymmetric addition of chiral boronate complexes bearing π system to iminium intermediates exploiting cation-π interaction“. Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690759.
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Chen, Jing. „SOLUTION AND SOLID STATE INTERACTIONS BETWEEN IONIC π-SYSTEMS“. UKnowledge, 2006. http://uknowledge.uky.edu/gradschool_diss/289.
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Although attractive interactions between π systems (π-π interaction) have been known for many years, understanding of its origin is still incomplete. Quantitative measuring of π-stacking is challenging due to the weak nature of the π-π interaction. This dissertation aims at elucidating a quantitative conformational analysis by NMR ring current anisotropy of an organic compound capable of intramolecular π-stacking in solution and studying charge effects on the stacking of π-systems. This dissertation offers four contributions to the area. (1) A general approach to four-state, conformational analysis based on the magnetic anisotropy of molecules undergoing fast dynamic exchange is described. (2) Study unveiled the importance of charges in the conformation of a dication in the solution. (3) Novel aromatic salt pairs of triangulene derivatives with the delocalized cation-anion interaction were synthesized and studied. (4) Study unveiled ionic π-systems preferred face-to-face stacking due to strong cation-π and anion-cation attractions.
A general protocol for the application of magnetic anisotropy to quantitative multi-state conformational analysis of molecules undergoing fast conformational exchange was suggested in the current study. The reliability of this method of conformational analysis was checked by the mass balance. VT-NMR was also conducted to study the enthalpic parameters. This technique can be further used to study canonical interactions such as ion pairing, hydrogen boning, and molecular recognition.
In the current study, dependence of the probe conformations on the dispersive interactions at the aromatic edges between solvent and probes was tested by conformational distributions of the fluorinated derivatives (2b and 2c) of the probe molecule (1a). Solution and solid studies of these molecules put the previous conclusion drawn by the Cammers group in question. Current studies show that the dispersive interaction at the aromatic edge could not be the predominant force on the conformational changes in the probe molecule 1a during the fluoroalkanol perturbation. This study indicated that charges might be important in the formation of the folding conformations in the solution and solid state of 1a, 2b, and 2c. A contribution of this thesis was to prepare and study a conformational model that lacked charges. The previous molecules were charged.
The solid-state structures of pyridinium-derived aromatic rings from the CSD (Cambridge Structural Database) were studied to investigate the π-π interaction between cationic π-systems in solid state. Novel aromatic salt pairs of triangulene derivatives with the delocalized cation-anion interaction were synthesized to study the π-π interaction between two aromatic rings that carried opposite charges. This study showed that the interaction between ionic π-systems can be enhanced by cation-π and anion-cation attractions. The stackings of these π-systems introduce more overlap, closer packing and stronger atomic contact than that of the solid states of comparable neutral species. Cation-π and anion-cation attractions are synergistic in aromatic salts.
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He, Tao. „I. Exploration of Amphitropic Protein Interactions at the Membrane Interface; II. DNF2—A Plant Protein with Homology to Bacterial PI-PLC Enzymes“. Thesis, Boston College, 2015. http://hdl.handle.net/2345/bc-ir:104815.
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Thesis advisor: Mary F. RobertsAmphitropic proteins, such as the virulence factor phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis, often depend on lipid-specific recognition of target membranes. However, the recognition mechanisms for zwitterionic lipids such as phosphatidylcholine (PC), which is enriched in the outer leaflet of eukaryotic cell membranes, are not well understood. Molecular dynamics (MD) simulation and mutagenesis results strongly indicate that PI-PLC interacts with PC head groups via cation-π interactions with aromatic tyrosine residues, and suggest that cation-π interactions at the interface may be a mechanism for specific lipid recognition by amphitropic and membrane proteins. Aromatic amino acids can not only form cation-π interactions at the interface but also insert into membranes and have hydrophobic interactions with lipid tails. Heretofore there has been no facile way to differentiate these two types of interactions. We show that specific incorporation of fluorinated amino acids into proteins can experimentally distinguish cation-π interactions from membrane insertion of the aromatic side-chains. Fluorinated aromatic amino acids destabilize the cation-π interactions by altering electrostatics of the aromatic ring while their enhanced hydrophobicity enhances membrane insertion. Incorporation of pentafluorophenylalanine or difluorotyrosine into a Staphylococcus aureus phosphatidylinositol-specific phospholipase C (PI-PLC) variant engineered to contain a specific PC-binding site demonstrates the effectiveness of this methodology. Applying this methodology to the plethora of tyrosine residues in Bacillus thuringiensis PI-PLC identifies those involved in cation-π interactions with PC. Cation-π interactions provide a likely molecular mechanism for BtPI-PLC PC specificity but do not account for its preference for bilayers containing a small fraction of anionic lipids. MD simulations and fluorescence correlation spectroscopy (FCS) vesicle binding measurements of positively charged amino acids as well as surface tyrosine residues are used to formulate a complete model of BtPI-PLC specific binding to mixed anionic phospholipid/PC membrane. DNF2, a new plant protein with homology to bacterial PI-PLC, is confirmed to be the first plant small PI-PLC enzyme that can cleave both PI and glycosylphosphatidylinositol (GPI) anchored proteins. GPI-anchored protein cleavage also confirms that DNF2 plays an important role in symbiosome, the intracellular compartment formed by the plant that contains nitrogen fixing bacteria
Thesis (PhD) — Boston College, 2015
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Ortega, Varga Laura. „Innovative inhibition strategy against functional structural transitions of essential pathogenic factors : Computational applications to Malarial and Neurotransmitter targets“. Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS455.
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Ce projet de thèse décrit la conception d'inhibiteurs de deux enzymes de l'agent du paludisme et de modulateurs de la sous-unité α5 des récepteurs nicotiniques de l'acétylcholine (nAChR) impliqués dans les dépendances. La subtilase de Plasmodium vivax (SUB1), nécessaire pour la sortie des parasites des cellules a été ciblée avec des inhibiteurs covalents réversibles. Nous avons effectué un docking covalent de peptidomimétiques candidats et étudié leur cyclisation. Plusieurs mimétiques ont montré une activité sub-micromolaire et leur structure a pu être résolue par co-cristallisation. Nous avons ciblé la lactate déshydrogénase, essentielle au métabolisme de Plasmodium falciparum avec des inhibiteurs conçus par analogie du tandem cofacteurs-substrat. Nous avons construit une bibliothèque combinatoire que nous avons criblé in silico, en évitant de cibler les isoenzymes humaines. Nous avons sélectionné une cinquantaine de molécules, en cours de synthèse pour tests ex vivo. Enfin, pour lutter contre les dépendances, une chimère α5-α4 de l'AChBP a été utilisée dans une approche multidisciplinaire. La structure en complexe avec les premiers ligands connus d'α5 a été résolue et nous l'avons utilisée avec deux modèles comparatifs pour un criblage in silico. Nous avons introduit l'interaction cation-π dans le logiciel FlexX, autorisé des chaînes latérales flexibles dans le site de liaison et développé un pipeline interactif pour l'analyse des résultats de criblage virtuel. Les molécules obtenues ont été confirmées par des expériences STD-RMN. Des modèles de réseaux neuronaux profonds ont également été construits pour prédire la bioactivité sur cible et hors cibleThis PhD project describes the design of inhibitors of two essential malaria enzymes and of novel modulators of specific nicotinic acetylcholine receptors (nAChRs). Plasmodium vivax subtilase SUB1 is required for parasite egress. We focused our efforts on the design of reversible covalent inhibitors of PvSUB1. We performed covalent docking of potential peptide and peptidomimetic candidates and studied peptide cyclization. Several peptides have shown activity in the submicromolar range and could be resolved after co-crystalization. Plasmodium falciparum lactate dehydrogenase is critical for parasite metabolism. We targeted it by design on the basis of inhibitory cofactor analogs. We have built a combinatorial library aiming to bridge the cofactor and the substrate binding site, while avoiding affecting the human isoenzymes. We screened it in silico and selected about fifty molecules that are under synthesis for ex vivo testing. We also targeted α5 subunit containing nAChRs to address addiction. A multidisciplinary approach has been established. It uses an AChBP engineered chimera, which structure was solved in complex with the first known 5 ligands. This structure, and two comparative modeling models were used to perform in silico screening. A cation-π interaction definition was introduced in the FlexX software and side chain flexibility was allowed in the binding site. An interactive pipeline was developed for the analysis of the virtual screening results and hit molecules have been confirmed by STD-NMR experiments. Deep neural networks models were also built to assess on- and off-target bioactivity prediction in a panel of nAChRs and putative off-targets
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Berry, Bruce W. „Using de novo design proteins to explore tyrosine radicals and cation-π interactions“. Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-102008.
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Redox cofactors and amino-acid free radicals play important roles in biology. Although many of the same cofactors and amino acids that form these radicals are found across a broad range of biological systems, identical cofactors can have different reduction potentials. The local environment plays a role in defining these redox potentials. An understanding of this local-environment effect can shed more light on how redox chemistry works in nature. Our laboratory has developed a library of model proteins that are well suited to study amino-acid radicals. a3X is a de novo designed protein that is composed of 67 residues. It forms a three-helix bundle connected by two glycine loops. The radical site is located at position 32 on the central a-helix. The a3X protein is designed to be well-folded and thermodynamically stable across a broad pH range. Paper 1 describes the structural and electrochemical characterization of a3Y, a tyrosine variant of a3X. We were able to obtain a unique Faradaic response from Y32 at both low and high pH, using differential pulse voltammetry. In addition, we successfully redesigned α3Y by introducing a histidine in close proximity to Y32, creating a tyrosine/histidine pair. Our goal in creating this pair was to study proton-coupled electron transfer (PCET) in a well-structured and solvent-sequestered protein environment. In paper 2 we illustrated the redox reversibility of Y32 and produced the first ever Pourbaix diagram for a tyrosine radical in a protein. The formal potential of the Y32-O/Y32-OH redox couple was determined to be 918 ± 2 mV vs. the normal hydrogen electrode (NHE) at pH 8.40. While at pH 5.52, the formal potential of the Y32-O/Y32-OH redox couple was recorded at 1.07 V. Papers 3 and 4 utilize a3W to study cation-π interactions. In paper 3, we showed how solvation can affect the strength of these interactions by -0.9 kcal/mol. In Paper 4, we were able to monitor the disruption of the cation-π interaction with the use of high-pressure fluorescence and were able to calculate the interaction energy for a solvent exposed cation-π. The aim of the work described in this thesis was to use model proteins to study tyrosine radicals to gain a broader perspective and better understanding of the versatility of biological electron transfer and to measure cation-π interactions and how they behave in different environments.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.
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Arnal-Hérault, Carole. „Matériaux biomimétiques adaptatifs programmés par auto-assemblage de nucléobases ou par interactions cation-π“. Montpellier 2, 2006. http://www.theses.fr/2006MON20100.
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7
Alshamrani, Nouf. „Cation-π Interactions of Selected Alkali Metal Ions with Two Benzene Rings Connected through Linear Chains“. DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2018. http://digitalcommons.auctr.edu/cauetds/147.
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Quantum chemical calculations at M06-2X/6-311+G(2d,2p) level were employed to examine the structures, dissociation energies and vibrational spectra of complexes formed by Li+, Na+ and K+ with diphenylmethane, 1,2-diphenylethane, 1,3-diphenylpropane, [2.2]paracyclophane and [3.3]paracyclophane molecules. The effect of heteroatom substitution in the connecting chains of 1,3-diphenylpropane and [3.3]paracyclophane molecules on the binding affinity of cations with ligands was also included in this study. The complexes of [3.3] paracyclophane based molecules seem to have weak cation-pi interactions with metal ions Na+ and K+ when they were placed between two rings. The binding affinity of the metal ion varies from the ligands possessing single fusion to double fusion of alkyl chain (or hetero substituted alkyl chain) with two benzene rings. Vibrational frequencies related to metal-ligand stretching, C-H, N-H and P-H stretching are useful to characterize the complexes with different metal ions and their positional preference.
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Mihai, Simona. „Systèmes biomimétiques multifonctionnels via des interactions cation-π, sucres-protéines et autoassemblages de quartets de guanosine“. Montpellier 2, 2009. http://www.theses.fr/2009MON20217.
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Le fonctionnement du monde vivant repose sur des processus de reconnaissance moléculaire entre les différents partenaires. Cette reconnaissance a lieu grâce à diverses interactions faibles non covalentes. Dans le cadre de ce travail de thèse nous nous sommes intéressés aux processus de reconnaissance moléculaire impliquant les chaînes latérales d'aminoacides aromatiques rencontrées dans l'adhésion cellulaire, le transport de divers cations et la reconnaissance de neurotransmetteurs au niveau des synapses du système nerveux central. Nous avons ainsi mis en évidence la compléxation de carbohydrates par des noyaux aromatiques au travers d'interactions CH-pi ainsi que la complexation de divers sels organiques et inorganiques au travers d'interactions cation-pi par ces mêmes récepteurs. Nous avons ainsi réalisé le transport compétitif de neurotransmetteurs au travers d'une membrane hybride alumino-siliciée fonctionnalisée par nos récepteurs synthétiques. D'autre part, nous avons accordé une importance particulière à la superstructure dynamique formée de quartets de guanosine et cherché notamment à observer le transfert de chiralité de cette structure à la matrice inorganique durant un processus sol gel. Nous avons également stabilisé les G-quadruplexes dans un milieu confiné silicié et avons développé une méthode d'encapsulation de principes actifs basée sur la reconnaissance spécifique des G4The functioning of the living world rests on processes of molecular recognition between the various partners. This recognition takes place thanks to diverse weak interactions not covalentes. Within the framework of this work of thesis we were interested in the processes of molecular recognition involving the side chains of aromatic aminoacides met in the cellular membership, the transport of diverse cations and the recognition of neurotransmitters at the level of the synapses of the central nervous system. We so put in evidence the compléxation of carbohydrates by aromatic nuclei through interactions CH-pi as well as the compléxation of diverse organic and inorganic salts through interactions cation-pi by these same receivers. We so realized the competitive transport of neurotransmitters through a hybrid membrane alumino-siliciée fonctionnalisée by our synthetic receivers. On the other hand, we granted a particular importance for the dynamic superstructure formed by quartets of guanosine and tried in particular to observe the transfer of chirality of this structure in the inorganic matrix during a sol-gel process. We also stabilized G-quadruplexes in a stuffy silicié environment and developed a method of encapsulation of active principles based on the specific recognition of G4
9
Pratuangdejkul, Jaturong. „Modélisation moléculaire de la sérotonine et de son transporteur“. Paris 5, 2005. http://www.theses.fr/2005PA05P634.
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L'objet de cette thèse a été dans un premier temps d'établir les relations quantitatives entre la structure et l'activité en trois dimensions (3D-QSAR) de 121 composés chimiques afin de déterminer les propriétés physicochimiques requises pour que ces molécules soient transportées par SERT. A partir de cette étude nous avons pu élaborer un pharmacophore du transport par SERT. Nous avons basé cette première étude sur une analyse conformationnelle exhaustive de la sérotonine par chimie quantique. Nous avons pu montrer d'une part que les forces électrostatiques qui influencent la conformation de la sérotonine sont majoritairement des interactions cation-p, avec une participation non négligeable d'un transfert de charge. Et d'autre part, que ces mêmes forces conditionnent les deux pKa de la sérotonine correspondant à l'ionisation des groupements ammonium et hydroxyle en 5, que nous avons pu prédire par calculs quantiques, en bon accord avec les valeurs expérimentalesThe object of this thesis was initially to establish the three dimensions quantitative structure-activity relationships (3D-QSAR) of 121 chemical compounds in order to determine the necessary physicochemical properties of these molecules transported through SERT. From this study we extracted a pharmacophore for the 3D definition of compound transported by SERT. We have based this study on an exhaustive conformational analysis of serotonin by quantum chemistry. We could show that the electrostatic forces which influence the conformation of serotonin are mainly due to cation-p interactions with a predominant participation of a charge transfer. We also showed that these non-bonded forces influence the two pKa of serotonin that correspond to the ionization of the ammonium and 5-hydroxyl groups. We could predict both pKa's in agreement with the experimental values by using ab initio calculations
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Kotze, Izak Aldert. „Self-association of [PtII(1,10-Phenanthroline)(N-pyrrolidyl-N-(2,2-dimethyl-propanoyl)thiourea)]+ and non-covalent outer-sphere complex formation with fluoranthene through cation-π interactions : a high resolution 1H and DOSY NMR study“. Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1796.
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11
Chiang, Chu-Harn, und 江曲涵. „Study of Cation−π Interaction Induced Folding of the Collagen Heterotrimers“. Thesis, 2019. http://ndltd.ncl.edu.tw/handle/ywra76.
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博士國立清華大學
化學系
107
Collagen is the most predominant component of the extracellular matrix. Exploring the forces to assemble synthetic collagen mimetic peptides (CMPs) into trimers has been an attractive topic in preparing collagen-related biomaterials. Natural collagens consist of all identical (AAA, homotrimer), two different (AAB, heterotrimer), or three different (ABC, heterotrimer) peptide chains. Many natural collagens are either AAB- or ABC-type heterotrimers, making heterotrimeric helices better mimics for studying such collagen structures in nature. We prepared CMPs containing cationic (Arg, Lys) or aromatic (Phe, Tyr) residues to explore the folding of collagen heterotrimers via cation−π interactions. We designed three systems of CMPs, the first two systems focus on generating AAB-type heterotrimers by interspersed cation−π interactions and C-terminal multiple cation−π interactions. The third system shows how ABC-type heterotrimer was brought out by cation−π interactions. In the first system, circular dichroism (CD), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) measurements showed that the interchain cation−π interactions between cationic and aromatic peptides could induce AAB-type heterotrimer formation. By controlling the mixing molar ratios of cationic and aromatic peptides in solution, we could obtain the heterotrimers with various compositions. The thermodynamic results revealed that the folding of such heterotrimers is an enthalpy-driven process, which directly showed the contribution of cation−π interactions to the folding of an AAB-type heterotrimer. In the second system, CD and NMR spectroscopy showed that heterotrimers (CR-CF) and (CK-CF) could be induced by the C-terminal multiple pairwise Arg-Phe and Lys-Phe interactions, suggesting that the C-terminal cation−π interactions between cationic and aromatic residues could serve as a nucleation force and substantially promote the folding of heterotrimers. In particular, only one major heterotrimeric fold was found in this system. For CR−CF mixtures, either the heterotrimer with two CR chains and one CF chain or that with one CR chain and two CF chains could form, depending on the molar ratios of CR to CF in solution. By contrast, in CK−CF mixtures only the heterotrimer consisting of two CK chains and one CF chain was found in solution even increasing the ratio of CF, implying that the heterotrimer composed of one CK chain and two CF chains is highly unstable. Additionally, DSC analysis showed that the folding of these heterotrimers is governed by entropic effects. In the third system, we used NMR to identify the composition of different heterotrimers by inlaying different numbers of 15N-isotopically enriched glycine in each peptide. The formation of a cation−π interaction induced ABC-type heterotrimer, which the interacting pairs were concentrated at both the N- and C-termini, was confirmed by NMR. Together, we have demonstrated the effectiveness of cation−π interactions as a force to fold collagen heterotrimers and revealed new insights into their folding thermodynamics. We also provide a new level of structural details that were not achieved for ABC-type collagen heterotrimers before.
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Orabi, Esam Abd El-Malek Abd-Allah. „Molecular modeling of cation–π interactions and ammonium permeation in AmtB“. Thesis, 2011. http://spectrum.library.concordia.ca/7274/1/Orabi_MSc_S2011.pdf.
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Cation–π interactions are noncovalent interactions known to play various important roles in chemical and biological systems. In proteins, such interactions usually involve Phe, Tyr or Trp in contact with inorganic cations or positively charged amino acids (Arg and Lys). AmtB is a transmembrane protein that has a high affinity for ammonium and facilitates its transport across the membrane which provides a source of nitrogen for amino acid synthesis in bacteria. The amino acid residues that line the pore of the crystallographically-identified outer binding site, S1, of AmtB (Trp148, Phe107, and Phe103) are known to stabilize NH4+ through cation–π interactions. However, the nature of the transported species, NH3 or NH4+, and the permeation mechanism are not yet known. In this study, ab initio quantum mechanical calculations at the MP2/6-311++G(d,p) level of theory are performed on the interaction of Li+, Na+, K+ and NH4+ with benzene monomer, dimer, and trimer in order to measure the strength of cation–π interactions in these systems and to parameterize a polarizable force field for these interactions. The resulting force field is used to investigate cation–π interactions and their effect on π–π interactions in water. Polarizable potential models for NH3, Na+, K+, and NH4+ interacting with H2O and with model compounds of the amino acids found along the AmtB permeation pathway are also developed based on ab initio calculations on these interactions at the same level of theory. The resulting models are used to investigate the binding selectivity of S1 toward NH4+ and the biologically abundant monovalent ions Na+ and K+. The nature of the permeable species and possible permeation mechanisms are also investigated based on molecular dynamics free energy calculations.
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Pan, Ming-Ta, und 潘銘達. „Importance of Cation-π Interactions for Protonated Serotonin and Fluoxetine based on DFT methods“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/20366795223621966585.
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碩士國立中正大學
化學暨生物化學研究所
99
Serotonin (5-hydroxytryptamine) is a kind of neurotransmitter and it plays an important role in the central nervous system. Fluoxetine is known as the selective serotonin reuptake inhibitors (SSRI) drug. In this study I would like to explore the importance of cation-π interaction for protonated serotonin and fluoxetine, based on DFT methods in aqueous solution. The aim and goal of this study is to model and help experimental and theoretical studies toward understanding the cation-π interaction compared to hydrogen bond interaction of protonated serotonin and fluoxetine, based on several different conformers and chirality of fluoxetine as well.
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Hsu, Wei, und 徐維. „Self-Assembly of Mimetic Collagen Peptides via Histidine-Metal Coordination and Cation-π Interactions“. Thesis, 2011. http://ndltd.ncl.edu.tw/handle/26551639616482318229.
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碩士國立清華大學
化學系
99
Collagen, the most abundant protein in mammals, has been widely used in biomedical materials. Searching for an effective way to assemble short mimetic collagen peptides into a higher order structure has been an emerging topic for the preparation of collagen-related biomaterials. In this work, we have incorporated histidine residue into two mimetic collagen peptides to promote the self-assembly of short collagen triple helices into supermolecular structure via His-metal coordination. Our results indicate that His-metal coordination can serve as an effective force to assemble mimetic collagen peptides into large scale structures and their topology depends on metal ions and His-metal coordination sites. Furthermore, the process of self-assembly can be reversed upon adding the cation chelator, EDTA, in solution. In addition, we have introduced a cationic residue into the N-terminus and an aromatic residue into the C-terminus of a collagen-related peptide which can generate favorable cation-π interactions between the termini of collagen triple helices. The experimental results demonstrate that cation-π interactions can promote the self-assembly of collagen triple helices into higher-order fibril structures in a head-to-tail manner. The work shows that cation-π interactions can serve as an effective force in preparing collagen-related biomaterials.
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Kao, Tang-Chun, und 高堂畯. „Using Cation-π Interactions to Form Heterotrimeric Collagen Helices and Assemble Collagen-Related Peptides“. Thesis, 2012. http://ndltd.ncl.edu.tw/handle/62946110639544354793.
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碩士國立清華大學
化學系
100
Collagen is an important structural component of tissues in animals. It has an unique right-handed triple helix consisted of three left-handed polyproline II like chains which are composed of X-Y-Gly repeats in the sequence. TypeⅠcollagen, a heterotrimer, is the most abundant form, and thus using heterotrimeric helices can be more appropriate to mimic nature collagen. In this work, we used cation-π interactions to assist collagen-related peptides to fold into heterotrimers. CD and NMR measurements indicate that (POGPRG)3(POG) &; (POGFOG)3(POG), (POGPRG)3(POG) &; (POGFOG)3(POG) &; (POG)7 mixed peptide solution could form a single heterotrimeric helices with Tm values of 26 and 27.5 ºC respectively, and no homotrimers were found. The results demonstrate that heterotrimers could be formed by interchain cation-π interactions. We have previously shown that terminal cation-π interactions can promote RG(POG)10F to rapidly assemble into fibrils. Here we further synthesized (POG)4(PRG)(FOG)(POG)4, (POG)3(PRG)(POG)2(FOG)(POG)3, (POG)2(PRG) (POG)4(FOG)(POG)2, and RG(POG)3(PRG)(POG)2(FOG)(POG)3F to study the position dependent effects of cation-π interactions on their self-assembly process. Turbility and dynamic light scattering measurements showed that such designs and arrangements do not significantly promote the assembly process. The results imply that the PRG and FOG triplets in place of POG in the middle of a collagen related peptide may impose steric effects through the bulky side chains of arginine and phenylalanine residues, which prevent the formation of strong cation-π interactions and retard the packing between collagen triple helices.
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Chen, Chia-Ching, und 陳佳青. „Study of Cation-π interactions in the stability and self-assembly of collagen triple helix“. Thesis, 2010. http://ndltd.ncl.edu.tw/handle/50835071376218003030.
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Fu, Yi-Hsuan, und 傅懿萲. „Effects of cation-π interactions and mutation of glycine residues on the stability of AAB-type collagen heterotrimers“. Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7ck6xf.
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碩士國立清華大學
化學系所
105
Collagen is a right-handed triple helix, and each helix is a left-handed polyproline type II structure containing many (X-Y-Gly) repeats. Many natural collagens consist of two or three different peptide chains. Type I collagen, the most abundant protein in the human body, is an AAB-type heterotrimer. Many forces were shown to have great contributions to collagen triple helix stability. Cation-π interaction, one of the forces, was found to be important in our previous studies. In this work, we prepared the collagen-mimetic peptides containing cationic or aromatic residues by incorporating Lys or Phe into the C-terminal end of the peptide chains. We attempted to use cation-π interactions to assist the folding of heterotrimers. Circular dichroism (CD), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) measurements showed that the cation-π interactions could effectively induced the formation of AAB-type heterotrimers. Compared to the results of Arg-containing CR3/CF3 series, (CK3)2(CF3)1 heterotrimers were less stable due to the weaker cation-π interactions between Lys and Phe. In addition, we prepared CR3_Sar and CK3_Sar in which a Gly residue near the center of CR3 and CK3 was substituted to sarcosine (Sar). Our results revealed that CR3_Sar could form homotrimers and AAB-type heterotrimers with CF3. The existence of cation-π interactions between chains has been confirmed by NMR measurements. Due to the weaker cation-π interactions between Lys and Phe, CK3_Sar, by contrast, could form neither homotrimers nor AAB-type heterotrimers with CF3.
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Li, Yu-Sheng, und 李育昇. „Preparation of the collagen-mimetic peptide-borane conjugate and the effects of disulfides and cation-π interactions on the folding of collagen heterotrimers“. Thesis, 2017. http://ndltd.ncl.edu.tw/handle/mqzhhy.
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碩士國立清華大學
化學系所
105
Collagen is the most abundant protein in mammals and is an important protein in human body. Collagen has been widely used in biomedical materials because of its biocompatibility, low immunity, and biodegradability. In the first part of this thesis, we prepared the collagen mimetic peptides (POG)7-boroncage conjugate, and investigated the delivery of boron into cells for the potential application in boron neutron capture therapy (BNCT). The results show that the boroncage moiety only slightly destabilize the collagen triple helix and the peptide-boroncage conjugate can enter cells. Most of natural collagens are heterotrimers composed of two (AAB) or three (ABC) different peptide chains, and thus studying heterotrimers can better mimic natural collagens. In our early study, we showed that (POG)6(PKG)3 can form heterotrimers with (POG)6(FOG)3 via cation-π interaction. Here we futher added Cys into the N-terminus of (POG)6(PKG)3, CGGG(POG)6(PKG)3, and replaced Gly to Sar, CGGG(POG)5(POSar)(POG) (PKG)3 to study the effects of disulfides and hydrogen bonding on heterotrimers. The results reveal that CGGG(POG)6(PKG)3 is similar to (POG)6(PKG)3 can form AAB-type heterotrimers with (POG)6(FOG)3, and the cation-π interactions could induce the AAB-type heterotrimers. However, neither disulfide-linked CGGG(POG)6(PKG)3 nor disulfide-linked CGGG(POG)5(POSar) (POG)(PKG)3 can form AAB-type heterotrimers with (POG)6(FOG)3. The resulted showed that the disulfide bond at the N-terminus could not facilitate to the folding of collagen heterotrimers and the replacement of Gly to Sar significantly destabilized the triple helix.