Hi, We have updated the ffAMBER website to include AMBER ports for v3.3.1 and also incorporated the AMBER-03 force field of Duan et al. in all ffAMBER ports (v3.1.4 thru v3.3.1). Please visit http://folding.stanford.edu/ffamber/ for more info. Enjoy! Eric J. Sorin Pande Group Stanford University Department of Chemistry