Optimized folding simulations of protein A.

We describe optimized parallel tempering simulations of the 46-residue B-fragment of protein A. Native-like configurations with a root-mean-square deviation of approximately 3 A to the experimentally determined structure (Protein Data Bank identifier 1BDD) are found. However, at biologically relevant temperatures such conformations appear with only approximately 10 % frequency in our simulations. Possible shortcomings in our energy function are discussed.