Interactions Of Antimicrobial Peptides Amps With Model Membranes At Different Ph Values

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Interactions of Antimicrobial Peptides (AMPs) with Model Membranes at Different PH Values

Author : Gagandeep K. Sandhu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (131 download)

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Book Synopsis Interactions of Antimicrobial Peptides (AMPs) with Model Membranes at Different PH Values by : Gagandeep K. Sandhu

Download or read book Interactions of Antimicrobial Peptides (AMPs) with Model Membranes at Different PH Values written by Gagandeep K. Sandhu and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Antimicrobial peptides (AMPs) are important components of the innate immune systems of many different organisms. Their amphipathic and cationic characteristics promote interactions with the cell membrane. Gad peptides are rich in histidine, and thus have the potential to exhibit pH-dependent activity. The major focus of this study was to understand how Gad peptides interact with model lipid membranes and how these interactions depend on the peptides' overall charge and the composition of the model membranes. 2H NMR spectroscopy was used to study the effect of Gad peptides on lipid acyl chain order of model lipid bilayers at different pH values. 2H NMR results revealed that membrane disruption by Gad peptides was not pH-dependent. Zeta potential measurements were used to study the binding of Gad peptides to model lipid membranes. The binding studies showed that for both Gad-1 and Gad-2 at low pH, less peptide binds to the membrane and the peptide interacts with a larger number of lipid molecules. Experiments performed with model membranes containing cardiolipin (CL) in the presence of Gad-1 showed that the presence of CL allows the membrane to accommodate more Gad-1. In the presence of CL the peptide binds more strongly with the membrane and interacts with a larger number of lipids. Taken together, these results suggest that Gad peptides might disrupt membrane integrity by clustering anionic lipids. Clustering of anionic lipids away from zwitterionic lipids by cationic AMPs might be a contributing mechanism, which does not exclude other mechanisms, including the carpet mechanism and pore formation. The chemical shift values of 15N NMR spectroscopy can give an insight about the positioning of peptides in lipid bilayer surfaces. 15N NMR observations showed that Gad-1 aligned parallel to the membrane surface. The study of AMP-membrane interactions will help to identify criteria to recognize the important features of natural AMP sequences involved in the antimicrobial action and thus assist in the design of AMP-based antibiotics to help overcome the problem of antimicrobial resistance.

Antimicrobial Peptides

Author : Katsumi Matsuzaki
Publisher : Springer
ISBN 13 : 9811335885
Total Pages : 304 pages
Book Rating : 4.8/5 (113 download)

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Book Synopsis Antimicrobial Peptides by : Katsumi Matsuzaki

Download or read book Antimicrobial Peptides written by Katsumi Matsuzaki and published by Springer. This book was released on 2019-04-12 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents an overview of antimicrobial peptides (AMPs), their mechanisms of antimicrobial action, other activities, and various problems that must still be overcome regarding their clinical application. Divided into four major parts, the book begins with a general overview of AMPs (Part I), and subsequently discusses the various mechanisms of antimicrobial action and methods for researching them (Part 2). It then addresses a range of activities other than antimicrobial action, such as cell penetration, antisepsis, anticancer, and immunomodulatory activities (Part 3), and explores the prospects of clinical application from various standpoints such as the selective toxicity, design, and discovery of AMPs (Part 4). A huge number of AMPs have been discovered in plants, insects, and vertebrates including humans, and constitute host defense systems against invading pathogenic microorganisms. Consequently, many attempts have been made to utilize AMPs as antibiotics. AMPs could help to solve the urgent problem of drug-resistant bacteria, and are also promising with regard to sepsis and cancer therapy. Gathering a wealth of information, this book will be a bible for all those seeking to develop antibiotics, anti-sepsis, or anticancer agents based on AMPs.

Biophysical Modelling of Antimicrobial Peptide's Interactions with Phospholipid and Lipopolysaccharide Membranes

Author : Shokoofeh Nourbakhsh
Publisher :
ISBN 13 :
Total Pages : 163 pages
Book Rating : 4.:/5 (112 download)

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Book Synopsis Biophysical Modelling of Antimicrobial Peptide's Interactions with Phospholipid and Lipopolysaccharide Membranes by : Shokoofeh Nourbakhsh

Download or read book Biophysical Modelling of Antimicrobial Peptide's Interactions with Phospholipid and Lipopolysaccharide Membranes written by Shokoofeh Nourbakhsh and published by . This book was released on 2019 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Antimicrobial peptides (AMPs) are naturally-occurring peptide antibiotics. The way they work has inspired a vigorous search for optimized peptide antibiotics for fighting resistant bacteria. Cationic AMPs cleverly utilize their electrostatic interactions with the bacterial membrane to selectively attack bacteria. Here, we first present a physical model of membrane selectivity of these peptides. For this, we use model membranes: phospholipid bilayers, possibly carrying a certain fraction of anionic lipids. The simultaneous presence of several competing effects (e.g., lipid demixing and peptide-peptide interactions), however, poses a serious challenge to theoretical analysis. We first examine critically various models of peptide-membrane interactions and map out one, which incorporates adequately these competing effects as well as the geometry of various regions in membranes, occupied by bound peptides, anionic lipids within the interaction range of each peptide, and those outside this range. This leads to a systematically-improved model for peptide selectivity. Using the model, we relate the peptide's intrinsic (cell-independent) selectivity to an apparent, cell-dependent one, and clarify the relative roles of peptide parameters and cell densities in determining their selectivity. A natural consequence of this relationship is that the selectivity is more sensitive to peptide parameters at low cell densities; as a result, the optimal peptide charge, at which the selectivity is maximized, increases with the cell density such that this notion becomes less meaningful at high cell densities. It also enables us to map out intrinsic selectivity from apparent (cell-dependent) one or biologically-relevant one from "conveniently-measured" selectivity. This effort will benefit our endeavour in optimizing the peptide parameters for their enhanced selectivity in a physiological environment. We extend our effort to examine peptide adsorption on the outer membrane (OM) of Gram-negative bacteria (e.g., Escherichia coli). In particular, we focus our effort on developing a model for the interaction between AMPs and the wild-type lipopolysaccharide (LPS) layer in a biologically relevant medium, containing monovalent and divalent salt ions like Mg2+. This requires a non-trivial generalization of an earlier coarse-grained model, in which the effects of oligosaccharide and O-antigen chains are ignored. In our model, these effects are captured by modelling the LPS layer as forming a polymer brush on top of its anionic phosphate groups. Using this model, we examine how the presence of oligosaccharide and O-antigen chains modifies the binding of antimicrobials to the LPS layer. Our results demonstrate that the presence of the saccharide brush reduces the number of hydrophobically- bound peptides to the polymer-grafted interface of LPS, compared to the deep-rough LPS layer that lacks the polymer brush. Our LPS brush model predicts [sim] 30% reduction of peptide adsorption, which is consistent with recent experimental measurements. This can be attributed to the steric hindrance of the brush or the excluded-volume interaction of the saccharide chains with peptides. At a low cell density limit, we also note that the total number of peptides trapped within the brush is very small, compared to the number of bound peptides on the LPS interface. This implies that the hydrophobic binding of peptides is insensitive to brush lengths. This, however, does not exclude the possibility of kinetic slowing-down of the binding.

Biomembranes

Author : Robert B. Gennis
Publisher : Springer Science & Business Media
ISBN 13 : 1475720653
Total Pages : 549 pages
Book Rating : 4.4/5 (757 download)

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Book Synopsis Biomembranes by : Robert B. Gennis

Download or read book Biomembranes written by Robert B. Gennis and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 549 pages. Available in PDF, EPUB and Kindle. Book excerpt: New textbooks at all levels of chemistry appear with great regularity. Some fields like basic biochemistry, organic reaction mechanisms, and chemical thermody namics are well represented by many excellent texts, and new or revised editions are published sufficiently often to keep up with progress in research. However, some areas of chemistry, especially many of those taught at the graduate level, suffer from a real lack of up-to-date textbooks. The most serious needs occur in fields that are rapidly changing. Textbooks in these subjects usually have to be written by scientists actually involved in the research which is advancing the field. It is not often easy to persuade such individuals to set time aside to help spread the knowledge they have accumulated. Our goal, in this series, is to pinpoint areas of chemistry where recent progress has outpaced what is covered in any available textbooks, and then seek out and persuade experts in these fields to produce relatively concise but instructive introductions to their fields. These should serve the needs of one semester or one quarter graduate courses in chemistry and biochemistry. In some cases, the availability of texts in active research areas should help stimulate the creation of new courses.

Interaction of Antimicrobial Peptides with Bacterial Cell Envelopes

Author : Nury Paula Santisteban Vela
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (131 download)

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Book Synopsis Interaction of Antimicrobial Peptides with Bacterial Cell Envelopes by : Nury Paula Santisteban Vela

Download or read book Interaction of Antimicrobial Peptides with Bacterial Cell Envelopes written by Nury Paula Santisteban Vela and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Antimicrobial peptides (AMPs) are small chains of amino acids with the ability to cause bacterial death. AMPs are usually amphiphilic but diverse in charge and structure. The mechanism or mechanisms that AMPs implement to kill bacteria are still under discussion. Studies in model membranes have widely demonstrated the capacity of AMPs to interact with and disrupt the bacterial cell membrane. There are however, good reasons to suspect that AMP interactions with nonmembrane components of bacteria are important. For instance, there is an enormous discrepancy between the peptide to lipid molar ratio (P:L) necessary to generate membrane disruption in model systems (~ 1:100), and the P:L necessary to stop bacterial growth, i.e. the minimal inhibitory concentration (MIC) (~ 10- 100:1). One potential explanation for this discrepancy is that AMPs may interact with non-membrane components of the bacterial cell envelope. The peptidoglycan (PGN) layer is one of the primary non-membrane components of Gram-positive bacterial cell envelopes and is responsible for cell shape and stability. Currently, there is an open discussion about whether PGN can entrap AMPs and prevent them from reaching the cell membrane or, instead promote the accumulation of AMPs on the cell membrane. The primary experimental approach employed in this thesis was 2H NMR spectroscopy of intact bacteria with 2H-labeled membranes. Specifically, since the quadrupolar splittings obtained from the spectra are proportional to the order parameter of the lipid acyl chains, the spectra reflect the structure and dynamics of the membrane. In particular, 2H NMR spectroscopy allows us to characterize the disruption of lipid bilayers caused by AMPs. In this study, different methods to grow 2H-membrane-enriched bacteria were optimized to obtain 2H NMR spectra of E. coli LA8, E. coli JM109 and B. subtilis. Additionally, 2H NMR was used to observe the level of disruption of the cell membrane of B. subtilis caused by the presence of different AMPs, MSI-78 and BP100. Both MSI-78 and BP100 caused the same level of membrane disruption at similar concentrations. Separately, comparison of the 2H NMR spectra of B. subtilis with intact and compromised PGN layers showed no differences. The lack of change in the spectra of PGN-compromised and PGN intact bacteria indicates that there is no change in the dynamics or structure of the lipid bilayer even with a weakened PGN layer. Finally, the disruption caused by MSI-78 and BP100 was measured in B. subtilis with a compromised PGN layer. The results indicate that there is no change in the level of membrane disruption caused by MSI-78 and BP100 when the PGN layer is partially removed.

Peptide and Protein Interaction with Membrane Systems

Author : Sara Bobone
Publisher : Springer
ISBN 13 : 3319064347
Total Pages : 147 pages
Book Rating : 4.3/5 (19 download)

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Book Synopsis Peptide and Protein Interaction with Membrane Systems by : Sara Bobone

Download or read book Peptide and Protein Interaction with Membrane Systems written by Sara Bobone and published by Springer. This book was released on 2014-05-31 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: In her thesis, Sara Bobone outlines spectroscopic studies of antimicrobial peptides (AMPs) which are promising lead compounds for drugs used to fight multidrug resistant bacteria. Bobone shows that AMPs interact with liposomes and she clarifies the structure of pores formed by one of these molecules. These results help us to understand how AMPs are selective for bacterial membranes and how their activity can be finely tuned by modifying their sequence. Findings which solve several conundrums debated in the literature for years. In addition, Bobone uses liposomes as nanotemplates for the photopolymerization of hydrogels - exploiting the self- assembly properties of phospholipids. Bobone was able to trap an enzyme using nanometeric particles, while still allowing its activity by the diffusion of substrates and products through the network of the polymer. The innovative nano devices described in this thesis could solve many of the hurdles still hampering the therapeutic application of protein-based drugs.

Interaction of Antimicrobial Peptides with Model Lipid Membranes

Author : Ahmad Arouri
Publisher :
ISBN 13 :
Total Pages : 178 pages
Book Rating : 4.:/5 (455 download)

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Book Synopsis Interaction of Antimicrobial Peptides with Model Lipid Membranes by : Ahmad Arouri

Download or read book Interaction of Antimicrobial Peptides with Model Lipid Membranes written by Ahmad Arouri and published by . This book was released on 2009 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Membrane-active Peptides

Author : Miguel A. R. B. Castanho
Publisher : Internat'l University Line
ISBN 13 : 0972077456
Total Pages : 675 pages
Book Rating : 4.9/5 (72 download)

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Book Synopsis Membrane-active Peptides by : Miguel A. R. B. Castanho

Download or read book Membrane-active Peptides written by Miguel A. R. B. Castanho and published by Internat'l University Line. This book was released on 2010 with total page 675 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Drug–biomembrane interaction studies

Author : T. Musumeci
Publisher : Elsevier Inc. Chapters
ISBN 13 : 0128091851
Total Pages : 24 pages
Book Rating : 4.1/5 (28 download)

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Book Synopsis Drug–biomembrane interaction studies by : T. Musumeci

Download or read book Drug–biomembrane interaction studies written by T. Musumeci and published by Elsevier Inc. Chapters. This book was released on 2013-10-31 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Antimicrobial agents are from different classes of molecules that suppress multiplication and growth of or kill microorganisms such as bacteria, fungi, or viruses. The precise mechanism of action of some antimicrobial agents is unknown but they must interact with or cross the cell membrane to have an effect. Identification of the damage induced by these compounds is difficult due to the complexity of cell membranes. Studying interactions using membrane models is a first step in obtaining elementary information about the effects of such drugs. We discuss interaction studies in the recent literature that use calorimetric techniques, regarding the mechanism of action or side effects of antimicrobial agents. For interaction studies with mimetic membrane models using DSC analysis, we will try to answer some key questions: (a) Does lipid composition affect the interaction? (b) Does the composition of bilayers influence the secondary structure of a peptide antimicrobial? (c) Does lipid polymorphism influence the activity and toxicity of the molecules? We underline the importance of phospholipids (neutral or anionic) chosen to produce biomembrane vesicles as models for the different studies.

Peptide-Lipid Interactions

Author : Sidney A. Simon
Publisher : Academic Press
ISBN 13 : 0080925855
Total Pages : 606 pages
Book Rating : 4.0/5 (89 download)

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Book Synopsis Peptide-Lipid Interactions by : Sidney A. Simon

Download or read book Peptide-Lipid Interactions written by Sidney A. Simon and published by Academic Press. This book was released on 2002-11-13 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains a comprehensive overview of peptide-lipid interactions by leading researchers. The first part covers theoretical concepts, experimental considerations, and thermodynamics. The second part presents new results obtained through site-directed EPR, electron microscopy, NMR, isothermal calorimetry, and fluorescence quenching. The final part covers problems of biological interest, including signal transduction, membrane transport, fusion, and adhesion. Key Features * world-renowned experts * state-of-the-art experimental methods * monolayers, bilayers, biological membranes * theoretical aspects and computer simulations * rafts * synaptic transmission * membrane fusion * signal transduction

Activity of an Alfa-helical Antimicrobial Peptide on Different Model Membranes Studied with Biophysical Techniques

Author : Nathaly Melina Marín Medina
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)

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Book Synopsis Activity of an Alfa-helical Antimicrobial Peptide on Different Model Membranes Studied with Biophysical Techniques by : Nathaly Melina Marín Medina

Download or read book Activity of an Alfa-helical Antimicrobial Peptide on Different Model Membranes Studied with Biophysical Techniques written by Nathaly Melina Marín Medina and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Antibiotic resistance has been declared as a major threat to public health because, in the last decades, bacteria have shown a clear trend becoming resistant to new antibiotics in increasingly shorter periods of time. Antimicrobial peptides (AMPs), described as "nature's antibiotics", are small amphipathic molecules produced in most complex living organisms as essential components of the innate immune system, whose function is to halt bacterial infections mainly by destabilizing the structure of the bacterial membrane. During the last three decades AMPs have been widely investigated given that understanding their mechanisms of action would provide new strategies for developing innovative antibiotics. Several experimental techniques have been used to study the interactions between AMPs and lipid membranes, each technique showing a somewhat different aspect of AMP action. However, imaging and force spectroscopy obtained with atomic force microscopy (AFM) have been only modestly used. In our research project we studied the interaction between a short cationic alfa-helical AMP and different types of model membranes. The experimental techniques used were fluorescence spectroscopy, AFM and micropipette aspiration, exploring large unilamellar vesicles (LUVs), supported lipid bilayers (SLBs), and giant unilamellar vesicles (GUVs), respectively. Magainin-H2, the peptide under study, forms multimeric pores on lipid bilayers beyond certain peptide/lipid ratio.--Tomado del Formato de Documento de Grado.

Influence of Local PH Environment and Zn(II) on the Structure of the Antimicrobial Peptide Clavanin A and Its Dynamics with Different Membrane Models in MD Simulations

Download Influence of Local PH Environment and Zn(II) on the Structure of the Antimicrobial Peptide Clavanin A and Its Dynamics with Different Membrane Models in MD Simulations PDF Online Free

Author : Searle Aichelle Duay
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (141 download)

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Book Synopsis Influence of Local PH Environment and Zn(II) on the Structure of the Antimicrobial Peptide Clavanin A and Its Dynamics with Different Membrane Models in MD Simulations by : Searle Aichelle Duay

Download or read book Influence of Local PH Environment and Zn(II) on the Structure of the Antimicrobial Peptide Clavanin A and Its Dynamics with Different Membrane Models in MD Simulations written by Searle Aichelle Duay and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the latest report from the Centers for Disease Control and Prevention (CDC) on antimicrobial resistance, this problem remains to be an urgent global threat, infecting about three million people and killing about 36,000 people in the United States annually. Antimicrobial peptides (AMPs) offer a number of advantages over small molecule antibiotics, such as their structural flexibility in response to different local environments, allowing for having environment-responsive modes of action. In this dissertation, we will focus on Clavanin A (ClavA), an AMP that was identified and can be extracted from the tunicate Styela clava. Experimentally, it was shown that ClavA acts via different mechanisms at different pHs, pointing to a more membrane-active mechanism at pH 7 than at pH 5. Its antimicrobial activity is also enhanced by 16-fold in the presence of Zn2+ ions. In Chapter 2, we used unbiased molecular dynamics (MD) simulations to explore the structure of ClavA and its interaction with different membrane models of Escherichia coli in different environments. It was shown that the gain in positive charge increases electrostatic attraction between ClavA and the negatively charged model membrane. We proposed the domino-effect model showing how Zn2+ enhances the initial attraction of ClavA to the model membrane. In Chapter 3, we explored different enhanced sampling techniques to generate pathways of ClavA translocation across a more complex model of an E. coli outer membrane. The advantages and disadvantages of using these techniques in novel AMP-membrane systems were described. The free energy profiles constructed from Hamiltonian replica exchange simulations showed that monomeric translocation of ClavA across the model membrane is unlikely. In Chapter 4, we used principal component analyses with bacterial cytological profiling to identify the mechanisms enforced by ClavA under different environmental conditions. In Chapter 5, the applicability of metadynamics in a different protein-metal ion system was showcased. This dissertation is a significant contribution to complement the existing body of empirical knowledge on Clavanin A. Through this work, we have exposed the strengths and limitations of using molecular dynamics simulations in metal ion-binding AMPs, which is an exciting set of AMPs that can be further studied.

Nucleic Acid Transfection

Author : Wolfgang Bielke
Publisher : Springer Science & Business Media
ISBN 13 : 3642164293
Total Pages : 316 pages
Book Rating : 4.6/5 (421 download)

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Book Synopsis Nucleic Acid Transfection by : Wolfgang Bielke

Download or read book Nucleic Acid Transfection written by Wolfgang Bielke and published by Springer Science & Business Media. This book was released on 2010-10-21 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gene Delivery into Mammalian Cells: An Overview on Existing Approaches Employed In Vitro and In Vivo, by Peter Hahn and Elizabeth Scanlan * Strategies for the Preparation of Synthetic Transfection Vectors, by Asier Unciti-Broceta, Matthew N. Bacon, and Mark Bradley * Cationic Lipids: Molecular Structure/Transfection Activity Relationships and Interactions with Biomembranes, by Rumiana Koynova and Boris Tenchov * Hyperbranched Polyamines for Transfection, by Wiebke Fischer, Marcelo Calderon, and Rainer Haag * Carbohydrate Polymers for Nonviral Nucleic Acid Delivery, by Antons Sizovs, Patrick M. McLendon, Sathya Srinivasachari, and Theresa M. Reineke * Cationic Liposome–Nucleic Acid Complexes for Gene Delivery and Silencing: Pathways and Mechanisms for Plasmid DNA and siRNA, by Kai K. Ewert, Alexandra Zidovska, Ayesha Ahmad, Nathan F. Bouxsein, Heather M. Evans, Christopher S. McAllister, Charles E. Samuel, and Cyrus R. Safinya * Chemically Programmed Polymers for Targeted DNA and siRNA Transfection, by Eveline Edith Salcher and Ernst Wagner * Photochemical Internalization: A New Tool for Gene and Oligonucleotide Delivery, by Kristian Berg, Maria Berstad, Lina Prasmickaite, Anette Weyergang, Pål K. Selbo, Ida Hedfors, and Anders Høgset * Visualizing Uptake and Intracellular Trafficking of Gene Carriers by Single-Particle Tracking, by N. Ruthardt and C. Bräuchle

Bridging Membrane Biophysics to Microbiology: Innovating Towards New Peptide and Peptide-based Antimicrobials

Author : Miguel A. R. B. Castanho
Publisher : Frontiers Media SA
ISBN 13 : 2889713520
Total Pages : 109 pages
Book Rating : 4.8/5 (897 download)

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Book Synopsis Bridging Membrane Biophysics to Microbiology: Innovating Towards New Peptide and Peptide-based Antimicrobials by : Miguel A. R. B. Castanho

Download or read book Bridging Membrane Biophysics to Microbiology: Innovating Towards New Peptide and Peptide-based Antimicrobials written by Miguel A. R. B. Castanho and published by Frontiers Media SA. This book was released on 2022-02-01 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt:

LIPIDAT A Database of Thermo Data and Association Information on Lipid

Author : Martin Caffrey
Publisher : CRC Press
ISBN 13 : 9780849389245
Total Pages : 334 pages
Book Rating : 4.3/5 (892 download)

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Book Synopsis LIPIDAT A Database of Thermo Data and Association Information on Lipid by : Martin Caffrey

Download or read book LIPIDAT A Database of Thermo Data and Association Information on Lipid written by Martin Caffrey and published by CRC Press. This book was released on 1993-06-04 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: LIPIDAT is a convenient compilation of thermodynamic data and bibliographic information on lipids. Over 11,000 records in 15 information fields are provided. The book presents tabulations of all known mesomorphic and polymorphic phase transition types, temperatures, and enthalpies for synthetic and biologically derived lipids in dry, partially hydrated, and fully hydrated states. It also includes the effect of pH, protein, drugs, salt, and metal ion concentration on these thermodynamic values. Methods used in making the measurements and the experimental conditions are reported. Bibliographic information includes a complete literature reference and list of authors. The book will be an indispensable reference for biophysicists, chemical engineers, pharmaceutical and cosmetic researchers, dermatologists, nutritionists, biochemists, physiologists, food scientists, and fats and oils chemists.

Fragments of the Human Antimicrobial LL-37 and Their Interaction with Model Membranes

Author : Claudia Dannehl
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (935 download)

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Book Synopsis Fragments of the Human Antimicrobial LL-37 and Their Interaction with Model Membranes by : Claudia Dannehl

Download or read book Fragments of the Human Antimicrobial LL-37 and Their Interaction with Model Membranes written by Claudia Dannehl and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed description of the characteristics of antimicrobial peptides (AMPs) is highly demanded, since the resistance against traditional antibiotics is an emerging problem in medicine. They are part of the innate immune system in every organism, and they are very efficient in the protection against bacteria, viruses, fungi and even cancer cells. Their advantage is that their target is the cell membrane, in contrast to antibiotics which disturb the metabolism of the respective cell type. This allows AMPs to be more active and faster. The lack of an efficient therapy for some cancer types and the evolvement of resistance against existing antitumor agents make AMPs promising in cancer therapy besides being an alternative to traditional antibiotics. The aim of this work was the physical-chemical characterization of two fragments of LL-37, a human antimicrobial peptide from the cathelicidin family. The fragments LL-32 and LL-20 exhibited contrary behavior in biological experiments concerning their activity against bacterial cells, human cells and human cancer cells. LL-32 had even a higher activity than LL-37, while LL-20 had almost no effect. The interaction of the two fragments with model membranes was systematically studied in this work to understand their mode of action. Planar lipid films were mainly applied as model systems in combination with IR-spectroscopy and X-ray scattering methods. Circular Dichroism spectroscopy in bulk systems completed the results. In the first approach, the structure of the peptides was determined in aqueous solution and compared to the structure of the peptides at the air/water interface. In bulk, both peptides are in an unstructured conformation. Adsorbed and confined to at the air-water interface, the peptides differ drastically in their surface activity as well as in the secondary structure. While LL-32 transforms into an [alpha]-helix lying flat at the water surface, LL-20 stays partly unstructured. This is in good agreement with the high antimicrobial activity of LL-32. In the second approach, experiments with lipid monolayers as biomimetic models for the cell membrane were performed. It could be shown that the peptides fluidize condensed monolayers of negatively charged DPPG which can be related to the thinning of a bacterial cell membrane. An interaction of the peptides with zwitterionic PCs, as models for mammalian cells, was not clearly observed, even though LL-32 is haemolytic. In the third approach, the lipid monolayers were more adapted to the composition of human erythrocyte membranes by incorporating sphingomyelin (SM) into the PC monolayers. Physical-chemical properties of the lipid films were determined and the influence of the peptides on them was studied. It could be shown that the interaction of the more active LL-32 is strongly increased for heterogeneous lipid films containing both gel and fluid phases, while the interaction of LL-20 with the monolayers was unaffected. The results indicate an interaction of LL-32 with the membrane in a detergent-like way. Additionally, the modelling of the peptide interaction with cancer cells was performed by incorporating some negatively charged lipids into the PC/SM monolayers, but the increased charge had no effect on the interaction of LL-32. It was concluded, that the high anti-cancer activity of the peptide originates from the changed fluidity of cell membrane rather than from the increased surface charge. Furthermore, similarities to the physical-chemical properties of melittin, an AMP from the bee venom, were demonstrated.

The Action of Antimicrobial Peptides on Supported Lipid Bilayers Investigated by Biophysical Methods

Author : Stefania Piantavigna
Publisher :
ISBN 13 :
Total Pages : 738 pages
Book Rating : 4.:/5 (11 download)

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Book Synopsis The Action of Antimicrobial Peptides on Supported Lipid Bilayers Investigated by Biophysical Methods by : Stefania Piantavigna

Download or read book The Action of Antimicrobial Peptides on Supported Lipid Bilayers Investigated by Biophysical Methods written by Stefania Piantavigna and published by . This book was released on 2014 with total page 738 pages. Available in PDF, EPUB and Kindle. Book excerpt: The emergence of bacteria that have developed resistance towards "traditional" antibiotics is becoming a serious global health threat. Consequently, alternative approaches are needed to find new drugs that can act directly as antibiotics or to assist traditional drugs to improve efficacy. The emergence of antimicrobial peptides (AMPs) as a possible new class offers promise. AMPs represent a large and varied group of "natural antibiotics" present in virtually every organism. However, in order to develop new drugs derived from AMPs knowledge of the bioactivity of these is needed, such as concentration ranges and specific bacterial targets. Of great practical importance is to have a comprehensive understanding of the mechanism of action of AMPs, so that the risk of cross-reactivity and development of new bacterial resistance is minimised. All AMPs interact with the cell membrane, which is a complex and dynamic system, mostly containing phospholipids and proteins. Phospholipids are not simple "bricks" of the membrane, but they themselves are involved in various cellular processes. Therefore, biomimetic membranes, e.g. supported lipid bilayers (SLBs), represent a valid approach for investigating the interactions between lipids and AMPs. Creation of a supported membrane reduces the complexity of those studies to just one variable. Many variables influence the formation of SLBs and a protocol regarding the formation of SLBs assembled on gold-coated sensors is described in Paper 1. The membrane deposition and the peptide-membrane interactions were investigated using a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) (Paper 2). Thus, the action of various peptides were investigated with zwitterionic membranes, which contained negatively charged lipid (bacterial membranes), or cholesterol (mammalian membranes).The action of the two most widely studied AMPs, melittin and magainin 2, on SLBs, has been examined using QCM-D in Chapter 3. These peptides formed "toroidal pores", which lead to membrane disruption. However, the action of these peptides has been found to be both concentration and composition dependent.Many AMPs are enriched in a particular amino acid residue. The influence of several of these peptide residues has been investigated using QCM-D in Chapters 4, 5 and 6. The action of proline-rich peptides apidaecins HbI and HbII, the variant Api88 and oncocin peptides on SLBs, are illustrated in Papers 3, 4 and 5, respectively. These peptides were found to insert into the membrane without any evidence of disruption. The influence of lipid composition on the activity of the arginine-rich peptide Tat has also been investigated with QCM together with scanning electrochemical microscopy (SECM) (Chapter 5). The cell-penetrating Tat peptide was shown to act as a lytic AMP in the presence of negatively charged membranes (Papers 6 and 7).The addition of tryptophan residues in the sequence of a short arginine-rich peptide, (RW)3, caused a dramatic switch from cell penetrating to lytic activity, while the inclusion of ruthenocene in the peptide RcCO-W(RW)2 did not affect the peptide activity (Chapter 6).Finally, in Chapter 7, Uperin 3.5, an amyloid-like AMP, demonstrated that the amyloid fibrils are not necessary for the membrane-disruption. However, the action of Uperin 3.5 towards zwitterionic membranes is switched to insertion if cholesterol is present in the membrane. Thus, QCM has been demonstrated to be an invaluable technique for characterising, in real time, the action of various peptides on SLBs of bacterial mimetic composition and mammalian. However, the combination of QCM with other techniques e.g. SECM, is always encouraged to reinforce this data and to gain a wide perspective of activity.