文摘
A few experimental and theoretical studies on the molecular structure of N-acetylproline amide (AP) in D2Osolution have been reported recently. However, there is no consensus of the precise structure of AP in D2Obecause spectroscopically determined structures and a theoretically simulated one have been found to bedifferent from one another. To determine its aqueous solution structure, IR and vibrational circular dichroismspectra of both L- and D-form AP solutions were measured. Molecular dynamics simulations with two differentforce fields and density functional theory calculations for the trans and cis rotamers of AP were performedto numerically simulate those spectra. Comparisons between experimentally measured and computationallysimulated spectra directly suggest that the AP in water adopts a polyproline II-like conformation and that theforce field parameter ff03 in the AMBER 8 suite of programs is more realistic and reliable in predictingmolecular structure of AP in water than the ff99 in AMBER 7.