CC/NUMBER 21 This Week’s Citation Classic MAY26,1986 ~ Spirin A S. Spektrofotometrichesloe opredelenie summarnogo kolichestva . nukleinovykh kislot (Spectrophotometric determination of total nucleic acids). Biokhimiya (USSR) 23:656-62. 1958. (A.N. Bakh Institute of Biochemistry, Academy of Sciences of the USSR, Moscow, USSR]

The paper describes a simple universal cient of molar extinction ~270= 10,000 in method of determining nucleic acids in bio- hot HCIO extracts of nucleic acids re- logical materials based on the measurement gardless of4 the type (DNA or RNA) and of the difference in optical densities of the base composition of the nucleic acids hot HCIO extract at two wavelengths, 270 under investigation. m~iand 2904 mp. [The SCI® indicates that this Subsequently, a modification had to paper has been cited in over 760 publica- be made to reduce the effect of extract- tions.] ed ultraviolet-absorbing materials of a nonnucleic acid nature; instead of a di- rect measurement of optical density at 270 m~i,I suggested using the difference of optical densities at two close wave- lengths, 270 m~and 290 m~(the differ- ence in optical densities at 270 m~and Alexander Spirin 290 m~idivided by 0.19 gives the number Institute of Protein Research of nucleic acid phosphorus micrograms Academy of Sciences of the USSR per milliliter). The method proved to be 142292 Pushchino, Moscow Region very convenient and yielded precise re- USSR sults at testing on a large number of ob- jects of animal and plant origin. (Howev- er, when applied to bacteria, the meth- od in this differential variant gave some February 20, 1986 under- or overestimation in the cases of extreme GC or AT types of their DNA, respectively.) Under strong pressure from my col- In 1955.1957 I was a postgraduate stu- leagues, I sent a two-page typewritten dent in A.N. Belozersky’s laboratory description of the method to Biokhimiya working on the content and base compo- (USSR). The manuscript was rejected as sition1 of nucleic acids of various bacte- unsubstantiated. This was one of the first ria. In the course of the work, a quick lessons for me as a beginning scientist. and precise determination of the total Then I supplied the manuscript with for- nucleic acid content in biological mate- mulae, equations, spectra, and so on, rials was required, and, naturally, I and this scientifically equipped paper turned my attention2 primarily to spec- was accepted. tral methods applied2~to hot HCIO ex- The method proved to be so simple, tracts of the cells. I noticed 4that precise, and widely applicable that it is though there were big differences in the used up to the present and is frequently absorbance spectra of different nucleo- cited even though it is not well known to tides, their molar extinction coefficients the international scientific community, iii an acidic medium differ relatively lit- having been published only in Russian. tle at 270 m~t.So I began to employ, and Among Soviet biochemists, it is the most also urged my colleagues working with popular method for determining nucleic me to do the same, the standard coeffi- acids.

I. Belozeriky A N & Spine A S. A correlation between the compositions of deoxyribonucleic and nbonucleic acids. Nature 182:lll-12, 1958. (Cited 65 times.) 2. Ogne M & Rosen G. The nucleic acids of plant tissues. 1. The extraction and estimation of desoxypentose nucleic acid and pentOse nucleic acid. Arch. Biochem. 25:262-76. 1950. (Cited l,095 times since 1955.) 3. SchneIder W C. Hageboom C H & Rose H E. Intracellular distribution of enzymes. VII. The distribution of nucleic acids and adenosinetriphosphatase in normal mouse liver and mouse hepatoma. I. Nat. Cancer Ins:. 10:977-82. 1950. (Cited 120 times since 1955.) 4. Ogur M. MlnklerS. Undegren C & Lladegrea C C. The nucleic acids in polyploid series of Sacc#tammyces. I Arch. Biochem. Biophys. 40:175-84, 1952. (Cited 140 times since 1955.)

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