title: Variation of type-B DNA x-ray fiber diagrams with base composition.
abstract: Eight natural DNAs of widely differing base composition have been studied by x-ray diffraction in fibers at high relative humidity. The resulting type B diffraction diagrams showed that all of the DNAs had a 34-A pitch and 3.4-A interbase pair separation. However, the intensity distribution on the inner three layer lines was a strong function of the base content. In diffraction diagrams of very AT-rich DNA, the intensity of the first and third layer line was 2- or 3-times stronger than in the patterns of GC-rich DNA. These high humidity diffraction patterns agree with x-ray scattering from solutions of DNA. The results are interpreted to imply that each AT base pair may have a different cross section than a GC pair. If this is so, it would appreciably alter the currently held ideas concerning DNA recognition.
mesh_terms: D000818:Animals; D001409:Bacillus cereus / Q000032:analysis; D001483:Base Sequence; D002417:Cattle; D003016:Clostridium perfringens / Q000032:analysis; D003589:Cytophaga / Q000032:analysis; D004247:DNA / Q000302:isolation & purification; D004269:DNA, Bacterial / Q000302:isolation & purification; D004272:DNA, Mitochondrial / Q000302:isolation & purification; D004926:Escherichia coli / Q000032:analysis; D008837:Micrococcus / Q000032:analysis; D009690:Nucleic Acid Conformation; D012441:Saccharomyces cerevisiae / Q000032:analysis; D012505:Sarcina / Q000032:analysis; D013210:Staphylococcus / Q000032:analysis; D013950:Thymus Gland / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D004269:DNA, Bacterial; D004272:DNA, Mitochondrial; D004247:DNA