Effects of Temperature and Pressure on the Aggregation Properties of an Engineered Elastin Model Polypeptide in Aqueous Solution

The pressure and temperature dependence of the cloud point transition of an aqueous solution of an elastin-like polypeptide (MGLDGSMG(VPGIG)_(40)VPLE), prepared by bacterial expression of the corresponding artificial gene, was measured. A temperature−pressure diagram was constructed over a wide range of conditions. The (VPGIG)_(40) solution exhibited a well-defined pressure-induced cloudpoint (P_c), as well as a temperature-induced transition (T_c). From near atmospheric pressure up to 100 MPa, T_c increased with increasing pressure, but decreased with further increases in pressure above 200 MPa. The maximum T_c was reached at 100−200 MPa. Between 10 and 25 °C, the Pc decreased with increasing temperature, and a broad maximum in P_c was observed in the range −10 to 0 °C. These results are compared with our previous results on synthetic thermoresponsive vinyl polymers.