Throughout the biological world, a 30 A hydrophobic film typically delimits the environments that serve as the margin between life and death for individual cells. Biochemical and biophysical findings have provided a detailed model of the composition and structure of membranes, which includes levels of dynamic organization both across the lipid bilayer (lipid asymmetry) and in the lateral dimension (lipid domains) of membranes. How do cells apply anabolic and catabolic enzymes, translocases and transporters, plus the intrinsic physical phase behaviour of lipids and their interactions with membrane proteins, to create the unique compositions and multiple functionalities of their individual membranes?

/pdf/membrane-lipids-where-they-are-and-how-they-behave-1rycz1l7v8.pdf

Membrane lipids: where they are and how they behave.

Antimicrobial peptides are an abundant and diverse group of molecules that are produced by many tissues and cell types in a variety of invertebrate, plant and animal species. Their amino acid composition, amphipathicity, cationic charge and size allow them to attach to and insert into membrane bilayers to form pores by 'barrel-stave', 'carpet' or 'toroidal-pore' mechanisms. Although these models are helpful for defining mechanisms of antimicrobial peptide activity, their relevance to how peptides damage and kill microorganisms still need to be clarified. Recently, there has been speculation that transmembrane pore formation is not the only mechanism of microbial killing. In fact several observations suggest that translocated peptides can alter cytoplasmic membrane septum formation, inhibit cell-wall synthesis, inhibit nucleic-acid synthesis, inhibit protein synthesis or inhibit enzymatic activity. In this review the different models of antimicrobial-peptide-induced pore formation and cell killing are presented.

Antimicrobial peptides: pore formers or metabolic inhibitors in bacteria?

T e purpose of this review is to assess the nature and magnitudes of the dominant forces in protein folding. Since proteins are only marginally stable at room temperature,’ no type of molecular interaction is unimportant, and even small interactions can contribute significantly (positively or negatively) to stability (Alber, 1989a,b; Matthews, 1987a,b). However, the present review aims to identify only the largest forces that lead to the structural features of globular proteins: their extraordinary compactness, their core of nonpolar residues, and their considerable amounts of internal architecture. This review explores contributions to the free energy of folding arising from electrostatics (classical charge repulsions and ion pairing), hydrogen-bonding and van der Waals interactions, intrinsic propensities, and hydrophobic interactions. An earlier review by Kauzmann (1959) introduced the importance of hydrophobic interactions. His insights were particularly remarkable considering that he did not have the benefit of known protein structures, model studies, high-resolution calorimetry, mutational methods, or force-field or statistical mechanical results. The present review aims to provide a reassessment of the factors important for folding in light of current knowledge. Also considered here are the opposing forces, conformational entropy and electrostatics. The process of protein folding has been known for about 60 years. In 1902, Emil Fischer and Franz Hofmeister independently concluded that proteins were chains of covalently linked amino acids (Haschemeyer & Haschemeyer, 1973) but deeper understanding of protein structure and conformational change was hindered because of the difficulty in finding conditions for solubilization. Chick and Martin (191 1) were the first to discover the process of denaturation and to distinguish it from the process of aggregation. By 1925, the denaturation process was considered to be either hydrolysis of the peptide bond (Wu & Wu, 1925; Anson & Mirsky, 1925) or dehydration of the protein (Robertson, 1918). The view that protein denaturation was an unfolding process was

/pdf/dominant-forces-in-protein-folding-42bjzlldw4.pdf

Dominant forces in protein folding

Prediction of protein conformation.

Thank you very much for downloading principles of fluorescence spectroscopy. As you may know, people have look hundreds times for their favorite novels like this principles of fluorescence spectroscopy, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they cope with some harmful bugs inside their desktop computer. principles of fluorescence spectroscopy is available in our digital library an online access to it is set as public so you can download it instantly. Our digital library spans in multiple locations, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the principles of fluorescence spectroscopy is universally compatible with any devices to read.

Principles Of Fluorescence Spectroscopy

Human cathelicidin LL-37 is a critical cationic antimicrobial peptide for host defense against infection, immune modulation, and wound healing. This article elucidates the functional roles of the cationic side chains of the major antimicrobial region of LL-37, corresponding to residues 17 to 32 (designated GF-17). Antimicrobial assays, killing kinetics studies, and vesicle leakage experiments all indicate that a conversion of lysines to arginines affected the ability of the peptide to kill the Gram-positive Staphylococcus aureus strain USA300. Alanine scanning experiments show that S. aureus is less sensitive than Escherichia coli to a single cationic residue mutation of GF-17. Among the five cationic residues, R23 appears to be somewhat important in killing S. aureus. However, R23 and K25 of GF-17 are of prime importance in killing the Gram-negative organism E. coli. In particular, R23 is essential for (i) rapid recognition, (ii) permeation of the E. coli outer membrane, (iii) clustering of anionic lipids in a membrane system mimicking the E. coli inner membrane, and (iv) membrane disruption. Bacterial aggregation (i.e., rapid recognition via charge neutralization) is the first step of the peptide action. Structurally, R23 is located in the interface (i.e., the first action layer), a situation ideal for the interactions listed above. In contrast, residues K18, R19, and R29 are on the hydrophilic surface of the amphipathic helix and play only a secondary role. Mapping of the functional spectrum of cationic residues of GF-17 provides a solid basis for engineering bacterium-specific antimicrobials using this highly potent template.

Decoding the functional roles of cationic side chains of the major antimicrobial region of human cathelicidin LL-37.

https://www.cell.com/biophysj/pdf/S0006-3495(07)70810-X.pdf

Novel Lipid Transfer Property of Two Mitochondrial Proteins that Bridge the Inner and Outer Membranes

Acyl chain dependence of diacylglycerol activation of protein kinase C activity in vitro.

Effect of influenza hemagglutinin fusion peptide on lamellar/inverted phase transitions in dipalmitoleoylphosphatidylethanolamine: implications for membrane fusion mechanisms.

https://www.cell.com/biophysj/pdf/S0006-3495(03)70035-6.pdf

Richard M. Epand

Papers

Decoding the functional roles of cationic side chains of the major antimicrobial region of human cathelicidin LL-37.

Novel Lipid Transfer Property of Two Mitochondrial Proteins that Bridge the Inner and Outer Membranes

Acyl chain dependence of diacylglycerol activation of protein kinase C activity in vitro.

Effect of influenza hemagglutinin fusion peptide on lamellar/inverted phase transitions in dipalmitoleoylphosphatidylethanolamine: implications for membrane fusion mechanisms.

Cholesterol in Bilayers of Sphingomyelin or Dihydrosphingomyelin at Concentrations Found in Ocular Lens Membranes