Thymus nucleic acid

Thymus-driise, /. thymus gland, -nuclein-saure, /. thymonucleic acid, thymus nucleic acid. 

The discovery of deoxyribonucleic acid dates to 1869, when Miescher isolated a new chemical substance from white blood cells that he obtained from pus and later from sperm cells.3 The material, which became known as nucleic acid, occurred in both plants and animals, thymus glands and yeast cells being among the best sources. Chemical studies indicated that the nucleic acids isolated from thymus glands and from yeast cells were different. As we now know, thymus nucleic acid was primarily DNA and yeast nucleic acid primarily RNA. For a while it was suspected that animals contained only DNA and plants only RNA, and it was not until the early 1940s that it was established that both substances were present in all organisms.3 ... 

In the early attempts to identify the nitrogenous bases of desoxy-ribosenucleic acid, some confusion arose for two reasons. At first, the products obtained by hydrolysis of nucleoprotein were studied, and there was no assurance that any particular base came from the nucleic acid rather than from the protein. Then, when the nucleic acid itself became available, the hydrolytic agents at first employed were sufficiently drastic to cause some deamination of the amino-purines (with the production of some xanthine and hypoxanthine) and some demethylation of thymine to uracil. In 1874, Piccard isolated guanine (and h3T>oxanthine) from sperm nuclein. Kossel and Neumann discovered in the hydrolysate of thymus nucleic acid two new pyrimidine bases which they named thy-mine and cytosine but they assigned incorrect empirical formulas to them. In 1894, they correctly described thymine as CsHgOjNs, but cytosine was not purified and characterized till much later. " " Levene now analyzed a series of nucleic acids from a variety of sources and found " that they all contained guanine and adenine. By mild hydrolysis of thymus nucleic acid, Steudel obtained guanine and adenine as the sole purine bases and demonstrated that they occur in equi-molecular proportions. Levene and Mandel confirmed this result and showed that the two purine bases and the two pyrimidine bases (thymine and cytosine) all occur in thymus nucleic acid in equimolecular proportions. 

Desoxyribosenucleic acid is readily hydrolyzed by mineral acids but is more resistant to alkaline fission than is ribosenucleic acid. Owing to the nature of the constituent sugar, the purine nucleotides are even more unstable than those of ribosenucleic acid. Hence, by acid hydrolysis of thymus nucleic acid, only the two pyrimidine nucleotides" " can be isolated. 

The two desoxyribosylpurines isolated from thymus nucleic acid are nucleosides of adenine and guanine. The identification of the nitrogenous bases has already been discussed. 

Synthetic 2-desoxy-L-ribose (-L-arabinose), prepared by the action of dilute sulfuric acid on L-arabinal (L-ribal), had the same numerical values of initial and equilibrium specific rotation (but opposite sign) as had the sugar of thymus nucleic acid. Hence the sugar was identified as 2-desoxy-D-ribose. On treatment with dilute sul-... 

The two desoxyribosylpyrimidines isolated from thymus nucleic acid are nucleosides of thymine and of cytosine. On treatment with 5% sulfuric acid, hydrolysis takes place giving the readily recognizable pyrimidine, but the sugar liberated is immediately transformed to levu-linic acid. This fact, combined with the results of elementary analysis of the two pyrimidine nucleosides, indicates that the sugar is a 2-desoxy-pentose. There is no proof that it is 2-desoxy-n-ribose. Attempts to hydrogenate thymidine by the method used for uridine have not been successful. 

In 1933, Klein discovered that sodium arsenate inhibits the action of the nucleotidase" of intestinal mucosa. Consequently, Klein and Thannhauser were enabled to hydrolyze thymus nucleic acid by means of intestinal desoxyribonucleinase without subsequent dephosphorylation of the liberated nucleotides. Making use, also, of Klein s discovery of the deaminase-inhibiting activity of silver ions, they were successful in isolating the adenine nucleotide. Hence the phosphodesoxyribosyl nucleotides of adenine, guanine, thymine, and cytosine were isolated and characterized. 

In 1912, Levene and Jacobs"" discovered that, on hydrolysis of thymus nucleic acid by means of boiling 2% sulfuric acid during two hours, diphosphoric esters of thymidine and of desoxyribosyr -cytosine may be isolated. ... 

DNA thymus nucleic acid Desoxiribon Eucytol. Polynucleotide essential component of chromosomes in cell nuclei. In its role as the carrier of genetic information, DNA must have two functions be exactly reproducible in order to... 

Thymine. S-Methyt-2,4(IHt3H)-pyritnidinedione 5 -metbyluracil 2,4 -dihydroxy - 5 -methylpyrimidine. C,H4 -N202 mol wt 126.11. C 47.62%, H 4.80%, N 22.22%, O 25.37%. A pyrimidine derivative constituent of nucleic acids. Originally isolated from thymus nucleic acid Levene, Z. Physiol Chem. 39, 4 (1903). Prepn by heating 2-ethyl-mercapto-4-hydroxy-5-methyl pyrimidine Wheeler, Mer-... 

Thymol methyl ether, in 1-10048 Thymosin al (human), see T-30098 Thymosin al (ox), see T-30098 Thymus nucleic acid, see D-10041 Tienef, in T-30270 6a-Tigloyloxychaparrin, in H-10095 6y9-Tigloyloxyeuryopsin, in F-10033 13a-Tigloyloxymultiflorine, in M-10092 Tilifolidione, T-20123 Tinctomorone, in D-10180... 

The nucleic acids were discovered by Miescher in 1868-1869, when he isolated from pus cell nuclei a material which contained phosphorus, was soluble in alkali, but precipitated under acidic conditions. This material was subsequently prepared from other sources and when freed from protein it was called nucleic acid, a term introduced by Altman in 1889. The classical preparations of nucleic acid from yeast yielded a product which we now recognize as ribonucleic acid (RNA). The nucleic acid prepared from thymus glands, thymonucleic acid, was also extensively studied this material [which, in present terms, was deoxyribonucleic acid (DNA)) was different from yeast nucleic acid. From hydrolysates of these preparations the heterocyclic bases were isolated and characterized. At one time, yeast and thymus nucleic acids were thought to be representative of plant and animal nucleic acids, respectively (3). By 1909, it was apparent that yeast nucleic acid contained adenine, guanine, cytosine, uracil, phosphoric acid, and a sugar which Levene showed at that time to be D-ribose. Thymonucleic acid yielded adenine, guanine, cytosine, thymine, phosphoric acid, and a sugar which was not identified correctly until 1929, when it was characterized as 2-deoxy-D-ribose. 

Kornberg, in the 1930 s DNA was still called thymus nucleic acid and widely believed to occur only in animal cells RNA had been isolated only from plant cells and was called yeast nucleic acid. In fact, plant and animal cells were sometimes distinguished on the basis of this chemical feature. ... 

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