[Optical measurements of nucleic acids in the presence of phenol and protein impurities].

Spectrophotometric method of determining the presence of phenol admixture in nucleic acid samples is presented. The method is based on determining the optical density ratio at 270 and 240 nm. This ratio is highly sensitive to the presence of phenol in solution. The method of determining nucleic acid concentration in the presence of phenol is also described. It is based on recording circular dichroism values at 265 nm for RNA and 275 nm for DNA. It is shown that the ratio of optical densities of nucleic acid samples at 260 and 280 nm is not a very sensitive criterion of the presence of proteins in solution. A much more sensitive characteristics is the ratio of circular dichroism values at 222 and 265 nm.