Micromethods of quantitative organic analysis
- J. B. Niederl, V. Niederl
- New York, 2nd edition,
Established methods for the preparation of desoxyribonucleic acid are time-consuming and result in low yields. The end-products are often depolymerized and, in some cases, are highly contaminated with protein. One of the earliest (and perhaps still one of the best) methods to be made available was that proposed by Hammarsten in 1924 (1). By employing a modification of this method, Schwander and Signer (2) obtained one of the most homogeneous, highly polymerized (3) nucleic acids so far described. For our purpose, however, both methods proved too cumbersome for the large scale preparation of desoxyribonucleic acid. For the same reason, the methods devised by Mirsky and Pollister (4) and by Gulland et al. (5) were not considered suitable, even though they provide a product of high molecular weight (6). The micromethods of Schneider (7) and of Schmidt and Thannhauser (8) yield an extensively degraded product, apparently because of the drastic treatments with strong acids and bases. To supply our need for large amounts of native sodium desoxyribonucleate (NaDNA), a simplified method was devised which permits almost quantitative isolation of the product in a purified form. This procedure is also based on the principles used by Hammarsten, but simplified and modified so that the extractions are carried out under neutral conditions. Since ripe salmon testes consist almost entirely of masses of spermatozoa, and thus provide one of the richest sources of nucleoproteins, we have used this tissue as starting material for the preparation of NaDNA. The mild conditions employed for isolation of NaDNA outlined here have enabled us to obtain as much as 28 gm. of nucleic acid from 400 gm. of salmon testes in a matter of a few hours. This represents more than 3 times the yield obtained by Hammarsten from thymus (I ).