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published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Orientador: Mario Sergio Palma / Banca: João Ruggiero Neto / Banca: Carlos Henrique Inácio Ramos / Banca: Eduardo Maffud Cilli / Banca: Clovis Ryuchi Nakaie / Resumo: Neste trabalho foram realizados estudos de caracterização estrutural e funcional de alguns peptídeos da classe dos mastoparanos de vespas, que apresentam diferentes padrões de anfipaticidade, em função das diferentes seqüências de aminoácidos que cada um possui. Os peptídeos foram manualmente sintetizados, utilizando-se estratégia Fmoc, e purificados através de técnicas de cromatografia líquida de alta performance. Após a obtenção do material sintético, foram realizadas análises de espectrometria de massas ESI-MS, para monitoração do controle de qualidade. A estrutura secundária foi investigada com o uso de espectroscopia de dicroísmo circular. Além disso, foram realizadas as modelagens moleculares e dinâmica dos peptídeos para análise de suas trajetórias. Foram feitos ensaios para investigar a interação desses peptídeos com membranas fosfolipídicas sintéticas (lipossomos), sendo esta interação, monitorada por medidas de dicroísmo circular e de troca isotópica H/D combinada com espectrometria de massas. Além disto, foram realizados ensaios de atividades biológicas de cada um dos peptídeos, onde foram testadas as atividades de degranulação de mastócitos, hemólise e antibiose. Os dados de Dicroísmo Circular revelaram que todos os peptídeos possuem a tendência de se estruturar em hélice-a quando em ambientes hidrofóbicos, ou em contato com membranas. Além disso, a presença de fosfolipídios ácidos nas membranas aumenta a interação eletrostática destas com peptídeos positivamente carregados. Os estudos de dinâmica molecular em meio aquoso mostraram alta flexibilidade estrutural dos peptídeos e uma variedade de estados conformacionais, em que predominam conformações randômicas, sem, contudo deixar de apresentar alguma porção helicoidal. Além disso, foi mostrado que esses peptídeos possuem caráter anfifílico quando estruturados em hélice / Abstract: The aim of the present investigation was to study the structure/activity relationship of a series of mastoparan-like peptides presenting different patterns of amphipathicit given by their distinct amino acid sequences. The peptides were manually synthesized by using Fmoc strategy and purified under HPLC. The synthetic material homogeneity was analyzed by ESI mass spectrometry and Edman Degradation Chemistry. The secondary structure was investigated through circular dichroism (CD) spectroscopy. In addiction, the secondary structures were modeled and their structural trajectories observed through Molecular Dynamics. The interaction of peptides with membranes was investigated through the combination of synthetic vesicles with H/D exchange and ESI-mass spectrometry. Some biological activities, like: mast cell degranulation, hemolysis and antibiosis were investigated for all the peptides. The CD spectra revealed that the peptides in presence of hydrophobic environment or in presence of biological membranes have the tendency to form helix conformations. Highly organized structures were not observed in aqueous or buffer solutions, however, the peptides always presented some tendency to form helices. The mastoparans interacts strongly and preferentially with the charged PG headgroups. The positive charges of these peptides enable selective binding to bacterial membranes through electrostatic interactions. The molecular dynamic studies of the peptides in water solvent revealed that all the peptides have high structural flexibility and many conformational states. Probably, these molecules assume different conformational states depending on the environment. In addition, it has been shown that the helical conformation gives the amphipathic feature to these peptides. The insertion and orientation of the mastoparan in the bilayer environment was investigated by H/D exchange, combined with mass spectrometry analysis / Doutor

Cone snails are venomous marine gastropods that produce venom rich in neuroactive peptides, called conopeptides. The majority of published work on conopeptides has been from fish-hunting and mollusk-hunting cone snails. The work in this dissertation focuses on the discovery and characterization of novel conopeptides from the venom of worm-hunting cone snails. Eleven novel conopeptides have been isolated and biochemically characterized from the venom of C. nux using high performance liquid chromatography for the isolation and purification, and mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy were used for the biochemical characterization of the conopeptides. Nano-NMR spectroscopy was used as a tool to elucidate the three-dimensional structures of four conotoxins using native quantities of peptide isolated from the venom of C. nux, C. villepinii, and C. regius. In addition, the sequence-specific assignments and molecular model of a conotoxin from the venom of C. flo ridanus was also completed. The first chapter reviews the known conotoxin three-dimensional structures and cystine-constrained frameworks. The second chapter presents the mini-M conotoxins isolated from the venom of C. nux. The third chapter presents the three-dimensional NMR solution structure of a mini-M conotoxin from the venom of C. regius. The fourth chapter presents the cysteine-free conopeptides isolated from the venom of C. nux; conorfamide-nux1, a RFamide-related peptide, and nux770, a short pentapeptide. The fifth chapter presents the T-superfamily conotoxins isolated from the venom of C. nux, as well as the three-dimensional solution structure of one of the T-superfamily conotoxins. The sixth chapter presents the NMR solution structure of the first conotoxin with a cysteine-stabilized helix-loop-helix fold. / Finally, the seventh chapter presents the O-superfamily conotoxins isolated from the venom of C. nux, as well as the three-dimensional solution structure of one of the O- superfamily conotoxins with an unusually knotted fold. This work shows the vast structural diversity of peptides that cone snails continue to engineer. / by Sanaz Dovell. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Cone snails are predatory marine animals that rely on their venom components to immobilize and capture their prey. According to the type of prey preference, cone snails can be divided into three groups: vermivorous, molluscivorous and piscivorous. Conus ermineus had been identified as the only piscivorous snail of the Atlantic Ocean. Cone snail venom is a complex and rich sources of natural toxins. The majority of the components of the venom are peptidic in nature, and they act over different ionic channels and membrane receptors. Initial studies using mixture of venom collected from dissected venom ducts concluded that the venom from the same species do not exhibit unusual peptide polymorphism [Olivera, Hillyard, et al., 1995] and that the only major difference between individuals of the same species are different concentrations of the venom components [Vianna, et al., 2005]. For this study, peptides in the injected venom were collected from individual snails and characterized usin g analytical RP-HPLC for a maximum of three years. The different fractions collected were processed through capillary HPLC coupled with Q-TOF ESI-MS, and compared with analytical RP-HPLC fractions processed with MALDI-TOF MS. This study demonstrates that there is an animal-to-animal variation in the peptide components of the injected venom. The injected venom remains relatively constant over time for specific specimens in captivity. Finally, there are some peptides that had been found in all specimens both by MALDI-TOF MS and by ESI-MS. In this study, these peptides are called "molecular fingerprint" peptides. Based on matches of their derived masses to those predicted by published cDNA sequences, nine novel peptides were putatively identified. This study establishes that variations due to enzymatic posttranslational modification are omitted when we consider only information extrapolated from cDNA. / The results of this study support the idea of the existence of a novel regulatory mechaism to expressed specific venom peptides for injection into the prey. / by Jose A. Rivera-Ortiz. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

Cone snails are venomous marine predators whose venom is a complex mixture of modified peptides (conopeptides). Conopeptides have direct specificity towards voltage- and ligand-gated ion channels and G-protein coupled receptors. More specifically, alpha conotoxins target nicotinic acetylcholine receptors (nAChR) and are of great interest as probes for different nAChR subtypes involved in a broad range of neurological function. Typically, the amount of peptide provided directly from the cone snails (from either dissected or “milked” venom) is minimal, thus hindering the wide use of bioassay-guided approaches for compound discovery. Biochemical-based approaches for discovery by means of identification and characterization of venom components can be used due to their compatibility with the small quantities of cone snail venom available; however, no direct assessment of the bioactivity can be gleaned from these approaches. Therefore, newly discovered conotoxins must be acquired synthetically, which can be difficult due to their complicated folding motifs. The ability to test small quantities of peptide for bioactivity during the purification process can lead to the discovery of novel components using more direct approaches. Presented here is the description of use of an effective method of bioassay-guided fractionation for the discovery of novel alpha conotoxins as well as further biological characterization of other known alpha conotoxins. This method requires minimal amounts of sample and evaluates, via in vivo electrophysiological measurements, the effect of conotoxins on the functional outputs of a well-characterized neuronal circuit in Drosophila melanogaster known as the giant fiber system. Our approach uses reversed-phase HPLC fractions from venom dissected from the ducts of Conus brunneus in addition to synthetic alpha conotoxins. Fractions were individually tested for activity, re-fractionated, and re-tested to narrow down the compound responsible for activity. A novel alpha conotoxin, bru1b, was discovered via the aforementioned approach. It has been fully characterized in the giant fiber system through the use of mutant flies, as well as tested in Xenopus oocytes expressing nicotinic acetylcholine channels and against the acetylcholine binding protein. Other well-known alpha conotoxins have also been characterized in the giant fiber system. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

by Fred. C. Pflueger. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliographical references at end of each chapter. / Cone snails are predatory marine gastropods that use venom for means of predation and defense. This venom is a complex mixture of conopeptides that selectivity binds to ion channels and receptors, giving them a wide range of potential pharmaceutical applications. Conus brunneus is a wide spread Eastern Pacific cone snail species that preys upon worms (vermivorous). Vermivorous cone snails have developed very specific biochemical strategies for the immobilization of their prey and their venom has not been extensively studied to date. The main objective of this dissertation is the characterization of novel conopeptides isolated from Conus brunneus. Chapter 1 is an introduction and background on cone snails and conopeptides. Chapter 2 details the isolation and characterization of a novel P-superfamily conotoxin. Chapter 3 presents the 3D solution structure of the novel P-superfamily conotoxin. Chapter 4 details the isolation and characterization of two novel M-superfamily conotoxins. Chapter 5 covers the use of nano-NMR to characterize a novel P-superfamily conotoxin using nanomole quantities of sample. Chapter 6 is a reprint of a paper published in the Journal of the American Chemical Society in which we combined and implemented techniques developed in the previous chapters to report the presence of D-(Sd(B-Hydroxyvaline in a polypeptide chain. This dissertation contains the first reported work of a P-superfamily structure obtained directly from the crude venom therefore accurately representing native post-translational modifications. In this paper, crude cone snail venom was characterized by: high performance liquid chromatography, nuclear magnetic resonance spectroscopy, nanonuclear magnetic resonance spectroscopy, mass spectrometry, amino acid analysis, Edman degradation sequencing, and preliminary bioassays.

The venom of marine gastropods belonging to the genus Conus has yielded numerous structurally and functionally diverse peptidic components. The increase variety of bioactive peptides identified in cone snail venoms is the product of the variety of molecular adaptations taken by Conus species in evolving neuroactive molecules to suit their diverse biological purposes. Toxins from cone snails are classified into two major groups. One group consists of disulfide-rich peptides commonly termed conotoxins; the second group comprises peptides with only one disulfide bond or none. In this work, we present the discovery and characterization from the marine snails C. planorbis and C. ferrugineus. Both species are commonly found in the Indo-Pacific region and are very similar and is not distinguishable by size and shape of the shell. Novel P and T-Supefamiles were found in both species along with small linear peptides with have a high frequency of tyrosine residues. Each chapter contains a detailed look at the discovery process for the isolation and characterization of C. planorbis and C. ferrugineus. At discussion part, we also compared the peptides isolated in this work with other peptides from the literature. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

The venom of cone snails is a potent cocktail of peptides, proteins, and other small molecules. Several of the peptides (conopeptides and conotoxins) target ion channels and receptors and have proven useful as biochemical probes or pharmaceutical leads. In this study, the venom of a fish-hunting cone snail, Conus purpurascens was analyzed for intraspecific variability; α-conotoxins from the venom were isolated by high performance liquid chromatography, identified by mass spectrometry and nuclear magnetic resonance, and tested in a electrophysiological assay in Drosophila melanogaster; the effects of diet change on venom composition was investigated. It has been determined that each specimen of C. purpurascens expresses a distinct venom, resulting in the expression of more than 5,000 unique conopeptides across the species. α- conotoxin PIA was shown to inhibit the Dα7 nicotinic acetylcholine receptor. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection

Made available in DSpace on 2014-06-11T19:30:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-13Bitstream added on 2014-06-13T19:40:31Z : No. of bitstreams: 1 souza_bm_dr_rcla.pdf: 2198506 bytes, checksum: e0710a5511f60c3053d26f8713b6478b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho foram realizados estudos de caracterização estrutural e funcional de alguns peptídeos da classe dos mastoparanos de vespas, que apresentam diferentes padrões de anfipaticidade, em função das diferentes seqüências de aminoácidos que cada um possui. Os peptídeos foram manualmente sintetizados, utilizando-se estratégia Fmoc, e purificados através de técnicas de cromatografia líquida de alta performance. Após a obtenção do material sintético, foram realizadas análises de espectrometria de massas ESI-MS, para monitoração do controle de qualidade. A estrutura secundária foi investigada com o uso de espectroscopia de dicroísmo circular. Além disso, foram realizadas as modelagens moleculares e dinâmica dos peptídeos para análise de suas trajetórias. Foram feitos ensaios para investigar a interação desses peptídeos com membranas fosfolipídicas sintéticas (lipossomos), sendo esta interação, monitorada por medidas de dicroísmo circular e de troca isotópica H/D combinada com espectrometria de massas. Além disto, foram realizados ensaios de atividades biológicas de cada um dos peptídeos, onde foram testadas as atividades de degranulação de mastócitos, hemólise e antibiose. Os dados de Dicroísmo Circular revelaram que todos os peptídeos possuem a tendência de se estruturar em hélice-a quando em ambientes hidrofóbicos, ou em contato com membranas. Além disso, a presença de fosfolipídios ácidos nas membranas aumenta a interação eletrostática destas com peptídeos positivamente carregados. Os estudos de dinâmica molecular em meio aquoso mostraram alta flexibilidade estrutural dos peptídeos e uma variedade de estados conformacionais, em que predominam conformações randômicas, sem, contudo deixar de apresentar alguma porção helicoidal. Além disso, foi mostrado que esses peptídeos possuem caráter anfifílico quando estruturados em hélice. / The aim of the present investigation was to study the structure/activity relationship of a series of mastoparan-like peptides presenting different patterns of amphipathicit given by their distinct amino acid sequences. The peptides were manually synthesized by using Fmoc strategy and purified under HPLC. The synthetic material homogeneity was analyzed by ESI mass spectrometry and Edman Degradation Chemistry. The secondary structure was investigated through circular dichroism (CD) spectroscopy. In addiction, the secondary structures were modeled and their structural trajectories observed through Molecular Dynamics. The interaction of peptides with membranes was investigated through the combination of synthetic vesicles with H/D exchange and ESI-mass spectrometry. Some biological activities, like: mast cell degranulation, hemolysis and antibiosis were investigated for all the peptides. The CD spectra revealed that the peptides in presence of hydrophobic environment or in presence of biological membranes have the tendency to form helix conformations. Highly organized structures were not observed in aqueous or buffer solutions, however, the peptides always presented some tendency to form helices. The mastoparans interacts strongly and preferentially with the charged PG headgroups. The positive charges of these peptides enable selective binding to bacterial membranes through electrostatic interactions. The molecular dynamic studies of the peptides in water solvent revealed that all the peptides have high structural flexibility and many conformational states. Probably, these molecules assume different conformational states depending on the environment. In addition, it has been shown that the helical conformation gives the amphipathic feature to these peptides. The insertion and orientation of the mastoparan in the bilayer environment was investigated by H/D exchange, combined with mass spectrometry analysis.