We have described an in vitro system in which active s&r tRNATyr is synthesized from a @Ops&r DNA template. Using this system, we have identified four essential components that are required for synthesis of tRNA. The first of these is DNA-dependent RNA polymerase. It has been shown that a crude preparation of DNA-dependent RNA polymerase synthesizes s&r tRNATyr precursor similar to that which h...

The interaction of ribonuclease A with cupric and zinc ions has been studied spectrophotometrically and by potentiometric titration in the presence and absence of cytidylic acid derivatives. In the absence of cytidylic acid, the results suggest that each cupric ion distributes among a set of approximately four spectrally similar sites; each site appears to consist mainly of a single imidazole s...

In order to elucidate whether or not the spectral and circular dichroic changes observed during the biodegradative threonine deaminase reaction are caused by the Schiff base formation between the enzyme-bound pyridoxal phosphate and the dehydrated intermediate, the role of substituents and the absolute configuration of the 0 carbon of substrates was investigated using various analogs of L-threo...

A well supported mechanism for succinyl-CoA:3-ketoacid coenzyme A transferase (EC 2.8.3.5) involving an enzymeCoA intermediate requires the participation of an oxygen atom of the enzyme or of the CoA moiety. Measurements of loss of 180 from acetoacetate show that CoA oxygens do not participate. An oxygen-containing group on the enzyme is reversibly labeled from succinateJ*O in the presence of a...

Synthesis and turnover of nitrate reductase molecules and soluble proteins of tobacco XD cells were studied by labeling pre-existing proteins with 14C-arginine to make them radioactive and with 99 atom % ‘5N to increase their buoyant density. The cells were then transferred to medium in which new proteins were synthesized from 14N and were radioactively labeled with 3H-arginine. The breakdown o...

Native sodium and potassium adenosine triphosphatase from guinea pig kidney accepted a phosphate group from radioactive inorganic phosphate to form an acyl phosphate bond at the active site in the presence or absence of sodium ion. Magnesium ion was always required. In the presence of sodium ion and absence of adenosine triphosphate, there was no phosphorylation by inorganic phosphate. Addition...

Rabbit reticulocytes at elevated temperatures, such as 45”, rapidly show a decrease in the rate of hemoglobin synthesis to one-third to one-tenth of the rate at 3’7”. This lower rate, which becomes irreversible after a few minutes, remains linear for up to 75 min. The soluble protein made at 45” is hemoglobin. Synthesis occurs on small polysomes carrying only two or three ribosomes, but actidio...

The purification of a lipoprotein fraction from rat liver has been reported from this laboratory (I, 2). This lipoprotein fraction was precipitated from a sodium chloride extract by the low temperature, ethanol fractionation procedure of Cohn et al. (3), and exhibited flotation as observed in the analytical ultracentrifuge at a density of 1.21, analogous to the high density lipoproteins of seru...

This new edition of Folin's Manual follows the same general plan of topics treated as that which characterized the earlier editions. The first chapter treats of such fundamental topics as acidimetry, alkalimetry, calibration of apparatus, and nitrogen determination. Some commentators might be disposed to criticize this on the ground that such matters should be considered prerequisite for entran...

the heterocyclic compounds have a great importance in medicinal chemistry. one of the most important heterocycles in medicinal chemistry are quinazolines possessing wide spectrum of biological properties like antibacterial, antifungal, anticonvulsant, anti-inflammatory, anti-hiv, anticancer and analgesic activities. this skeleton is an important pharmacophore considered as a privileged structur...