Open AccessDirect Evidence of the C-Like Form of Sodium Deoxyribonucleate
Author(s) -
J. Brahms,
J. Pilet,
Tran-Thi Phuong Lan,
L. R. Hill
Publication year - 1973
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.70.12.3352
Subject(s) - relative humidity , dna , chemistry , circular dichroism , molecule , sodium , infrared spectroscopy , crystallography , infrared , linear dichroism , analytical chemistry (journal) , biochemistry , chromatography , organic chemistry , optics , physics , thermodynamics
From infrared linear dichroism studies, direct evidence is given for a new Na DNA form, which is similar to the C form of Li DNA. This C-like form in Na DNA occurs under conditions of very low NaCl content (at high relative humidity), high NaCl content (at low relative humidity), and low G + C content of the DNA (at low relative humitiy). The C form of Li DNA was originally discovered by x-ray diffraction, but has not previously been characterized by infrared spectroscopy. The C form is primarily characterized by the orientation of the O2- -O3 line of the phosphate group, which is about 48° (±2°) with respect to the helical DNA axis and which is different from that of the B and A forms. Na DNA molecules rich in A + T may entirely or partially adopt the C form at low relative humidity. Since from infrared evidence, the C-like form is found not only in Li DNA at low relative humidity but also in Na DNA under different conditions, the C form may be biologically important. A possible role for recognition by proteins is suggested.