Jh. Riazancelawrence et al., FLOW LINEAR DICHROISM AND FOURIER-TRANSFORM IR-SPECTRA REVEAL GEOMETRY FOR X-FORM DNA, Biopolymers, 34(11), 1994, pp. 1469-1476
Flow linear dichroism measurements extended into the vacuum uv region
yield inclinations for the base normal from the helix axis of 21 degre
es for dA and 40 degrees for dT in the X-form of poly(dAdT).poly (dAdT
). These inclination angles are similar to the B form of the synthetic
polymer, but the axes around which the bases incline are different. H
ydrogen-bonded base pairs are consistent with the geometry for the sta
ndard B, C, D, and Z forms of natural DNA, but will not fit into the A
form. Fourier transform ir spectra indicate that the X form has sugar
pucker and phosphate geometry similar to B-form DNA, and supports the
dinucleotide repeat with two kinds of phosphates seen in earlier work
, in analogy to Z-form DNA. Clearly, X-form DNA has a unique geometry.
(C) 1994 John Wiley and Sons, Inc.