Tom Simonson and Dave Case have collaborated to implement the Amber force
field and generalized Born solvation model into Xplor-NIH. This is primarily
useful for NMR structure calculations (and especially for those persons who are
already familiar with Xplor or CNS). There are interesting similarities and
differences between the way sander and Xplor-NIH handle NMR
analyses, but the similarities are probably more striking than the
For a discussion of the effects of using the Amber/GB force field (rather than the Engh-Huber-based targets) see B. Xia, V. Tsui, D.A. Case, H.J. Dyson, and P.E. Wright. Comparison of protein solution structures refined by molecular dynamics simulation in vacuum, with a generalized Born model, and with explicit water. J. Biomol. NMR 22, 317-331 (2002).