title: Computer programming for nucleic acid studies. II. Total chemical shifts calculation of all protons of double-stranded helices.
abstract: A FORTRAN computer program called SHIFTS is described. Through SHIFTS, one can calculate the NMR chemical shifts of the proton resonances of single and double-stranded nucleic acids of known sequences and of predetermined conformations. The program can handle RNA and DNA for an arbitrary sequence of a set of 4 out of the 6 base types A,U,G,C,I and T. Data files for the geometrical parameters are available for A-, A'-, B-, D- and S-conformations. The positions of all the atoms are calculated using a modified version of the SEQ program [1]. Then, based on this defined geometry three chemical shift effects exerted by the atoms of the neighboring nucleotides on the protons of each monomeric unit are calculated separately: the ring current shielding effect: the local atomic magnetic susceptibility effect (including both diamagnetic and paramagnetic terms); and the polarization or electric field effect. Results of the program are compared with experimental results for a gamma (ApApGpCpUpU) 2 helical duplex and with calculated results on this same helix based on model building of A'-form and B-form and on graphical procedure for evaluating the ring current effects.
mesh_terms: D001483:Base Sequence; D003201:Computers; D004247:DNA; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D012330:RNA, Double-Stranded
chemical_list: D011522:Protons; D012330:RNA, Double-Stranded; D004247:DNA