title: Direct evidence of the C-like form of sodium deoxyribonucleate.
abstract: 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 degrees (+/-2 degrees ) 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.
mesh_terms: D000227:Adenine Nucleotides; D000818:Animals; D001412:Bacillus subtilis / Q000032:analysis; D001483:Base Sequence; D002417:Cattle; D003016:Clostridium perfringens / Q000032:analysis; D003589:Cytophaga / Q000032:analysis; D004247:DNA / Q000302:isolation & purification*; D004269:DNA, Bacterial; D005673:Fusobacterium / Q000032:analysis; D008094:Lithium; D008297:Male; D009174:Mycoplasma / Q000032:analysis; D009690:Nucleic Acid Conformation; D012474:Salmon; D012965:Sodium Chloride; D013055:Spectrophotometry, Infrared; D013094:Spermatozoa / Q000032:analysis; D013942:Thymine Nucleotides; D013950:Thymus Gland / Q000032:analysis
chemical_list: D000227:Adenine Nucleotides; D004269:DNA, Bacterial; D013942:Thymine Nucleotides; D012965:Sodium Chloride; D004247:DNA; D008094:Lithium