Synthesis of polymeric models of elastin: Polyhexapeptides and an insoluble, hybrid cross-linked polypeptide

Synthesis of Peptide-Based Polymers by Microwave-Assisted Cycloaddition Backbone Polymerization

The optimized reaction conditions for the Cu(I)-catalyzed N-->C polymerization of azido-phenylalanyl-alanyl-propargyl amide to yield either high molecular weight linear polymers or medium-sized cyclic polymers is described. These reaction conditions will be applied to tailor the synthesis, properties, and structure of biologically relevant peptide-based biopolymers.

Crystal structure of cyclic (APGVGV)2, an analog of elastin, and a suggested mechanism for elongation/contraction of the molecule

Tropoelastin is a complex polymeric protein composed primarily of repeating segments of Val-Pro-Gly-Gly, Val-Pro-Gly-Val-Gly, and Ala-Pro-Gly-Val-Gly-Val that occurs in connective tissue and arteries. It has rubber-like extensible properties. A synthetic cyclic dodecapeptide, with a double repeat of the hexapeptide sequence, has been shown to undergo a reversible inverse temperature transition; that is, crystals grow at 60 degrees C and dissolve in the mother liquor upon cooling. An x-ray crystal structure analysis established that the cyclic backbone formed an elongated loop with a Pro-Gly, type II beta turn at both ends. Six internal cross strand NH...OC hydrogen bonds form between six NH donors and four O=C acceptors where two of the carbonyl O atoms are bifurcated acceptors. As a result, the molecule is pulled up into a corrugated profile. The corrugated loops form extended beta-sheets by additional intermolecular hydrogen bonds. An analysis of the dome region in a corrugated sheet suggests a reversible mechanism for extending and contracting the length of the whole molecule, akin to the motion of opening and closing an umbrella, caused by the motion of a water molecule with its associated hydrogen bonds acting as spokes. Crystal parameters: C44H72N12O12.3H2O, sp. gr. P2(1)2(1)2(1), a = 9.212 angstroms, b = 19.055 angstroms, c = 32.247 angstroms, d = 1.157 g/cm3.

Stimulation of cell proliferation and autoregulation of elastin expression by elastin peptide VPGVG in cultured chick vascular smooth muscle cells

Synthetic elastin peptides, VPGVG or its polymer (VPGVG)n, enhanced the proliferation of smooth muscle cells 1.5-fold during 48 h treatment at the concentrations over 10(-6) M or 1.0 microgram/ml, respectively. Monomeric and polymeric VPGVG sequences reduced elastin synthesis and its mRNA level to one-third and one-half of control respectively under the conditions in which the proliferation of cells were enhanced, but did not change collagen synthesis as measured by bacterial collagenase digestion. The elastin-specific autoregulation by elastin fragments may reflect the feedback regulation of elastin expression which may play an essential role in elastin metabolism under the normal and diseased conditions.