[Secondary structure of DNA from T4 and T6 phages]

The secondary structure of NaDNA from E. coli T4 and T6 phages has been studied by the X-ray diffraction method. Molecules of these DNAs as well as T2 phage DNA molecules contain hydroxymethylcytosine glucosylated at different position instead of cytosine. At high relative humidity these DNAs are shown to exist in B-conformaion. As humidity decreases the transformation into T=conformation takes place in the T4 phage DNA whereas in the T6 phage DNA changes of secondary structure similar to B-T transformation occur which do not result however in the appearance of all the characteristics of the T-conformation.