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Interfacial chemistry: drugs, peptides and ezymes interactions with membrane models

Grant number: 16/00709-8
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): May 01, 2016
Effective date (End): January 31, 2017
Field of knowledge:Biological Sciences - Biophysics
Principal Investigator:Iolanda Midea Cuccovia
Grantee:Bhaskar Manda
Home Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated research grant:13/08166-5 - Interfacial chemistry: drugs, peptides and ezymes interactions with membrane models, AP.TEM

Abstract

Peptide interaction Antimicrobial Agents and Membrane Model. Antimicrobial peptides are molecules that act on membranes causing disturbances that can lead to transient formation of pores or the removal of a portion of the lipid bilayer via a detergent-like action. These molecules may have different structures, many of which have predominantly helical secondary structures. These peptides are more efficient when they have an amphipathic nature, where the cationic face of the helix is the first interaction of electrostatic nature, with the anionic phospholipids of the membrane. Then, the hydrophobic side of the helix peptide promotes insertion of the lipid bilayer leading to the formation of pores or detergent effect. An undecapeptide class was designed and its antimicrobial activity and selectivity against mammalian cells were assayed. Knowledge of selectivity between prokaryotic and eukaryotic membranes, which has clear biotechnological importance, depends on the detailed physical-chemical study of the interaction of these peptides with lipid bilayers and the investigation of how the lipid composition can affect the selectivity This study has been conducted for the undecapeptide BP100, whose selectivity of action on bacteria compared to the action on mammalian cells is high.Modifications will be made to the structure of the peptide BP100 in order to check the effect on the activity and selectivity. The first strategy is to introduce a cyclization between the propeller ends. Alanine and glycine residues will be inserted as spacers in the N-terminal and C-terminal regions of the propeller and the amino and carboxyl groups are linked by amide bond. Alternatively, azide groups, and alkyne are introduced into the chain ends with spacer residues allowing their union by means of the cycloaddition reaction Click catalyzed by Cu (I) in a method complement recently applied to peptides of this class, but here applied to form a cyclopeptide. The second strategy is the insertion of a cysteine residue in the chain of BP100 to enable the formation of a chain homodimer. The BP100 connecting two chains can lead to an increase in its activity. Studies with the heterodimeric Distinctina peptide, originally isolated from the skin of the frog phyllomedusa distincta showed that one of the chains can help to anchor the other chain in the lipid bilayer. Therefore, structural analogues of BP100 are synthesized with the addition of spacers, and a cysteine residue for forming a disulfide bridge between two identical chains.It will be prepared a peptide hybrid and a photoactive molecule, the class of the naphthalimides, which are known to promote photochemical damage to nucleic acids and proteins. The naphthalimides when excited with a high yield conversion of intersystem singlet state to the triplet state. The triplet state of naphthalimides, which has a lifetime of the order of microseconds to milliseconds in solution, is oxidant and may lead to the formation of radical cations of tryptophan in protein and nitrogenous base guanine in the DNA. The effect of naphthalimides on lipids is less studied, but the unsaturated constituents of phospholipids fatty acids are common oxidizing molecules targets. The strategy proposed is the connection imides naftálicas at the amino-terminus of BP100 chain added alanine or glycine residues as spacers. The connection will be conducted from the corresponding naphthalic anhydrides compatible with solid phase synthesis of peptides. It is intended to thereby promote the photo-oxidation of integral membrane proteins and unsaturated lipids while the peptide is anchored in the lipid bilayer and thereby change irreversibly the membrane. (AU)