Direct Observation of the Contraction of an Unfolded Protein with Temperature

Abstract

A fundamental tenet in protein folding is that the hydrophobic effect promotes chain collapse. For the unfolded state, however, we and others find that proteins adopt conformations that closely resemble a self-avoiding random walk (SARW). That an unfolded protein would remain expanded suggests that the hydrophobic effect is smaller than anticipated or other factors promote chain expansion such as backbone solvation. In a similar vein, NMR data on Gly-rich proteins and poly(Asn) consistently measure minimal protection factors across a variety of buffer conditions.