Abstract
We report on a molecular dynamics simulation based study of the thermal and mechanical properties of the elastin mimetic peptide [LGGVG](n) (n = 3, 7). Our findings indicate that this peptide undergoes an inverse temperature transition as the temperature is raised from ~20 °C to 42 °C. The thermal behavior is similar to what has been observed in other well studied short mimetic peptides of elastin. Both [LGGVG](n) (n = 3, 7) peptides exhibit an increase in the number of side chain contacts and peptide-peptide hydrogen bonds when the temperature is raised from ~20 °C to 42 °C. These observations are accompanied by a decrease in the number of proximal water molecules and number of peptide-water hydrogen bonds. This work also reports on a comparison of the thermal and mechanical properties of [LGGVG](3) and [VPGVG](3) and quantifies the interaction with surrounding waters of hydration under mechanically strained conditions. It is demonstrated, via a quasi-harmonic approach, that both model peptides exhibit a reduction in the population of low-frequency modes and an increase in population of high-frequency modes upon elongation. The shift in population of frequency modes causes the peptide entropy to decrease upon elongation and is responsible for the development of an entropic force that gives rise to elasticity. These observations are in disagreement with a previously published notion that model elastin peptides, such as [VPGVG](18), increase in entropy upon elongation.
Highlights
Elastin, the principal protein component of the elastin fiber, is an extracellular insoluble protein responsible for the remarkable elasticity of many vertebrate tissues
Via short 9 ns simulations, that the signatures of an inverse temperature transition in repeats of [VPGVG]n (n = 18) include a decrease in solventaccessible surface area (SASA), radius of gyration, number of peptide-water hydrogen bonds, and number of proximal water molecules concomitant with an increase in number of peptidepeptide hydrogen bonds and side chain contacts as the temperature is raised from 7 ◦C to 45 ◦C.7
More recently it was demonstrated that the oligopeptide GVG[VPGVG] behaves as a two-state system that undergoes an inverse temperature transition and that a re-entrant unfolding occurs near the boiling point of water
Summary
The principal protein component of the elastin fiber, is an extracellular insoluble protein responsible for the remarkable elasticity of many vertebrate tissues. Via short 9 ns simulations, that the signatures of an inverse temperature transition in repeats of [VPGVG]n (n = 18) include a decrease in solventaccessible surface area (SASA), radius of gyration, number of peptide-water hydrogen bonds, and number of proximal water molecules concomitant with an increase in number of peptidepeptide hydrogen bonds and side chain contacts as the temperature is raised from 7 ◦C to 45 ◦C.7 In these studies, a type II β-turn was observed in the Ramachandran maps of glycine, valine, and proline segments at 10 ◦C and 42 ◦C.7. These observations are in disagreement with a previously published notion that model elastin peptides, such as [VPGVG]18, increase in entropy upon elongation.
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