FRACTAL-LIKE PATTERNS IN DNA FILMS, B-FORM AT 0-PERCENT RELATIVE-HUMIDITY, AND ANTIHETERONOMOUS DNA - AN IR STUDY

This report details the observation of (a) the intact double helix of DNA at 0% relative humidity in poly(dA).poly(dT) and poly(dA-dT).poly( dA-dT) films, (b) the fractallike growth of DNA crystals in films of p oly(dA).poly(dT), and (c) poly(dA).poly(dT) with adenines in the B for m and thymines in the A form. Observation (a) is based on the behavior of the middle ir signature of double-helical base stacking, the 1714 cm(-1) peak, at low water activity. This observation is modeled as a t rapping of water in the polycrystalline part of these films. We interp ret the glycosidic region of the middle ir spectra of the polycrystall ine films of poly(dA).poly(dT) at 0% relative humidity to indicate tha t at least part of the adenine strand in is the B conformation and the thymine strand is in the A form, whereas previous assignments of poly (dA).poly(dT) films at 75% relative humidity indicated the opposite st rand conformation assignment [E. Taillandier et al. (1987) Biochemistr y, Vol, 26 p. 3361]. (C) 1994 John Wiley & Sons, Inc.