Primary explants of P388, EL-4, and L1210 murine leukemia cells and of normal mouse bone marrow are shown to require sulfhydryl compounds for proliferation in vitro. Nine extablished cell lines show no stimulation by these compounds. Leukemia cells can lose the sulfhydryl dependence after various periods of adaptation to in vitro culture. Various sulfhydryl compounds have widely differing poten...

Spinach leaf glyoxylic acid reductase, an enzyme containing two identical or similar subunits, has been shown to have 12 half-cystine residues. Four of these are necessary for catalytic function and can be titrated as free sulfhydryl groups. One mole of cysteinyl residues per mole of enzyme is essential to catalytic activity when evaluated under conditions favoring optimal activity. All free su...

The results of previous work have indicated (2, 3) that one sulfhydryl group of microsomal cytochrome reductase is essential for the interaction of nucleotides with this enzyme. These results, however, do not rule out the possibility that there are other reactive sulfhydryl groups on the native enzyme and that they are involved directly or indirectly in nucleotide-enzyme interactions. In the ex...

Disullide bonds in proteins and in seed meals were reduced with /3-mercaptoethanol to sulfhydryl groups. The generated sulfhydryl groups were then alkylated by treatment with 4-vinylpyridine. The cysteine residues were thus derivatized to S-(4-pyridylethyl)-L-cysteine residues. The cysteine derivative is stable to acid hydrolysis and on amino acid analysis by ion exchange elutes just before arg...

1. Addition of 2 moles of mersalyl, mercuric chloride, p-chloromercuribenzoate (PCMB), or methyl mercury hydroxide per mole of hemoglobin greatly reduces heme-heme interactions (n), yet these substances have quite different effects on the oxygen affinity (-log p(50)). Mersalyl and mercuric chloride at this concentration each increase the oxygen affinity, while PCMB and methyl mercury have littl...

1. Methods have been described for reducing protein S-S groups, for oxidizing protein SH groups, and for estimating protein S-S and SH groups. 2. It has been found necessary in estimating the cystine content of proteins by the Folin-Marenzi method to take into account any cysteine that may be present. 3. A method for estimating the cysteine content of proteins has been described. 4. With these ...

The relationship of sulfhydryl and disulfide groups to protein synthesis in normal and rapidly growing tissues was investigated by quantitation of sulfhydryl groups in endoplasmic reticulum and polyribosomes of normal liver and hepatomas. Stripping by ethylenediaminetetraacetate and potassium chloride of normal liver smooth and rough endoplasmic reticulum reduced by 15 percent and increased 30 ...