Biological & Soft Matter Seminar: Very Strong Hydrogels Formed by the Self-Assembly of GxG-type Tripeptides Explored by Vibrational Spectroscopy, Rheology, Microscopy and X-ray Diffraction

Zoom: https://tau-ac-il.zoom.us/j/88904888353?pwd=dDIwaXRxSjlsVElkR0dXdTNPTGhnZz09

Abstract: 

Over the last 15-20 years some ultrashort peptides have emerged as powerful gelators. These peptides have in common that they contain amino acid residues such as phenylalanine and/or end groups such as  fluorenylmethyloxycarbonyl (Fmoc). We recently observed that neither aromatic end groups nor aromatic side chains are a necessity for peptide gelation. For example, cationic GAG self-assemble into exceptionally long and thick crystalline fibrils with lengths on a sub-millimeter and even millimeter scale in water-ethanol mixtures. These fibrils are capable of forming sample spanning networks the topology of which depends on the concentration of peptides and the mole fraction of ethanol. GHG peptides were found to form a gel phase similar to that of GAG in aqueous solution upon deprotonation of its imidazole side chain. Other GxG peptides with aromatic guest residues (x=F,W.Y) can also gelate in water after being subjected either to a heating - cooling cycle or cyclic changes of pH. All GxG gels have in common that their storage moduli are very high with some values in the upper 100 kPa regime. Crystal structures obtained from Xray-diffraction data and amide I profiles in respective IR and vibrational circular dichroism spectra suggest that the observed fibrils are not formed by sheets exhibiting conventional β-sheet structures. Very preliminary measurements indicate that some of hydrophobic drugs can preferentially bind to the surface of the formed fibrils.