Infrared linear dichroism reveals that A-, B-, and C-DNAs in films have bases highly inclined from perpendicular to the helix axis.
Infrared linear dichroism has been employed to investigate the inclination of the bases in films of poly[d(AC)].poly[d(GT)], poly[d(AG)].poly[d(CT)], and natural DNAs (from Escherichia coli and calf thymus). All DNAs investigated assume the B-form at high (> 94%) relative humidity. Poly[d(AC)].poly[d(GT)], E. coli DNA, and calf thymus DNA assume the A-form at low (75%) relative humidity, whereas poly[d(AG)].poly[d(CT)] assumes the C-form at low (66%) relative humidity. Infrared linear dichroism demonstrates that the bases for DNA in films are highly inclined from perpendicular to the helix axis, even for B-DNA. C-DNA has almost same inclinations as in B-DNA, and the inclinations are slightly increased in A-DNA. These inclination angles confirm our earlier UV linear dichroism results for the orientation of the bases for DNA in solution. Infrared linear dichroism has also been used to obtain conformational angles for the phosphodiester backbone geometry of the A-, B-, and C-forms of DNA.
Department of Biochemistry and Biophysics, Oregon State University, Corvallis 97331-7305.
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D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004247:DNA / Q000737:chemistry*; D004269:DNA, Bacterial / Q000737:chemistry; D003903:Deuterium; D004926:Escherichia coli / Q000235:genetics; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013950:Thymus Gland / Q000737:chemistry
D004269:DNA, Bacterial; D011089:Polydeoxyribonucleotides; D004247:DNA; D003903:Deuterium