(634d) Molecular Description of LCST Behavior of Elastin-like Peptides Poly(VPGVG) and Poly(VGPVG)

The elastin-like peptide (ELP) is temperature sensitive biopolymer which undergoes conformational transition at critical temperature. Elastin-like polypeptides (ELPs) with the repeat sequence of VPGVG are widely used as a model system for investigation of lower critical solution temperature (LCST) transition behavior. Recent experimental observations show that the order of amino acids in the ELP sequence also plays an important role since (VGPVG)_n and (VPGVG)_n peptides show the differences in thermo-transition behavior. In order to elucidate the factors driving the conformational transitions of ELPs we performed molecular dynamics simulations of (VPGVG)_n and (VGPVG)_n peptides with different length and at a range of temperatures. Comprehensive analyses of the hydrophobicity, shape, size, hydration and dynamics of (VPGVG)_n and (VGPVG)_n suggest that the transition behavior includes the thermal disruption of water network, loss of hydration, and increase in peptide hydrophobicity. Our simulations show that single poly(VGPVG) is more hydrophilic than poly(VPGVG) at high temperatures while similar hydrophobicity of two types of ELPs at low temperatures is observed. Simulations of the peptide-peptide association demonstrated that the aggregates formed by double poly(VGPVG) chains are more densely associated than poly(VPGVG) at high temperature. Even more compact association of double poly(VGPVG) was observed upon cooling the aggregates obtained from the double-peptide simulation. In the contrary, poly(VPGVG) aggregates dissociate  upon cooling which is consistent with the reversibility exhibited in experiments. The results from our study provide an atomic-level description of the thermo-responsive conformational properties of elastin-like peptides and explain experimental observations. Support for this research was provided by the NSF's Research Triangle MRSEC (DMR-1121107).