Structure, Stability, and Hydration of a Polypeptide in AOT Reverse Micelles

It has been known for a time, both from experiments1 and theory,2 that confining a peptide chain within a geometrically restricted environment increases the relative stability of the folded state against unfolded states. This finding is of biological relevance as (in vitro) intrinsically disordered proteins have shown to be structured or folded in their native cellular environment where excluded volume effects are important. A convenient means to confine a protein within a certain region of space is through encapsulation in reverse micelles3 (RM). In this communication, we provide theoretical evidence that the folded structure of a simple peptide, alanine zwitterionic octapeptide, or A8, unstable in solution, becomes stable in an RM of appropriate size. Our molecular dynamics simulations were carried out for realistic models of sodium 2-ethylhexylsulfo-succinate (AOT) RM in isooctane, simulated for an extended period of time. For the RM of the smaller size, we find that a helica