O2- oxidizes the [4Fe-4S] clusters of dehydratases, such as aconitase, causing-inactivation and release of Fe(II), which may then reduce H2O2 to OH- +OH.. SODs inhibit such HO. production by scavengingO2-, but Cu, ZnSODs, by virtue of a nonspecific peroxidase activity, may peroxidize spin trapping agents and thus give the appearance of catalyzing OH. production from H2O2. There is a glycosylated, tetrameric Cu, ZnSOD in the extracellular space that binds to acidic glycosamino-glycans. It minimizes the reaction of O2- with NO. E. coli, and other gram negative microorganisms, contain a periplasmic Cu, ZnSOD that may serve to protect against extracellular O2-. Mn(III) complexes of multidentate macrocyclic nitrogenous ligands catalyze the dismutation of O2- and are being explored as potential pharmaceutical agents. SOD-null mutants have been prepared to reveal the biological effects of O2-. SodA, sodB E. coli exhibit dioxygen-dependent auxotrophies and enhanced mutagenesis, reflecting O2(-)-sensitive biosynthetic pathways and DNA damage. Yeast, lacking either Cu, ZnSOD or MnSOD, are oxygen intolerant, and the double mutant was hypermutable and defective in sporulation and exhibited requirements for methionine and lysine. A Cu, ZnSOD-null Drosophila exhibited a shortened lifespan.

Superoxide Radical and Superoxide Dismutases

/pdf/the-surface-chemistry-of-amorphous-silica-zhuravlev-model-4kfs2lx66q.pdf

The surface chemistry of amorphous silica. Zhuravlev model

A preparative method for isolating high-molecular-weight DNA from animal cells is described. This method is based on the use of proteinase K, a powerful proteolytic enzyme with a broad action spectrum, which is very active in the presence of sodium dodecylsulfate and ethylene-diamine tetraacetate. The DNA preparation is free of RNA, protein and degrading enzymes. The number-average molecular weight of the native DNA is 190 × 106, whereas it is 90 × 106 for single-stranded DNA, indicating that the DNA molecules do not contain single-stranded nicks. The native DNA molecules range in molecular weight from 40 × 106 to more than 500 × 106.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1973.tb02881.x

Isolation of high-molecular-weight DNA from mammalian cells.

Towards the physiological function of uric acid

Studies on a variety of chemical carcinogens have demonstrated that their ultimate reactive and carcinogenic forms are strong electrophiles. Some carcinogens, such as alkylating agents, are in their ultimate forms as administered, but most require metabolism to these active derivatives. The ultimate carcinogens react, usually non-enzymatically, with nucleophilic constituents in vivo. Of particular interest in regard to their possible importance in carcinogenesis have been the covalent interactions of these electrophilic reactants with cellular informational macromolecules, the DNAs, RNAs, and proteins. Current data are consistent with the idea that the initiation step of chemical carcinogenesis is a mutagenic event and is caused by alteration of DNA by the ultimate carcinogens. The nature of the carcinogen metabolite(s) involved in the promotion phase has not been determined, but there appears to be no requirement that they be electrophilic. The development of the concept of ultimate chemical carcinogens as strong electrophilic reactants is reviewed, especially with respect to the studies carried in the authors' laboratory.

Searches for ultimate chemical carcinogens and their reactions with cellular macromolecules

Thiation of Nucleosides. II. Synthesis of 5-Methyl-2'-deoxycytidine and Related Pyrimidine Nucleosides1

The transfer of the methyl group from methionine to choline and creatine

Pyrimidine Nucleosides. I. A New Route for the Synthesis of Thymine Nucleosides1

1. Adenosine analogs with substitutions in the 2-position have been shown to elicit adenosine-like vasodepression in the cat. Several of these analogs were found more potent than adenosine; all caused hypotension of greater duration than that produced by the parent riboside.

2. The relatively transient nature of the hypotension induced by adenosine in the cat has been attributed to the activity of adenosine deaminase. Persistence of vasodepression, characteristic of the 2-substituted congeners, has been attributed to failure of the enzyme to deaminate these analogs.

3. A manometnic method has been described which was employed to study the adenosine deaminase activity of various tissues of cats, rats and rabbits and to ascertain the relative susceptibility of adenosine and its analogs to enzymatic degradation.

4. The influence of molecular alteration on the vasodepressor activity of purine nibosides has been discussed.

George Bosworth Brown

Papers

Thiation of Nucleosides. II. Synthesis of 5-Methyl-2'-deoxycytidine and Related Pyrimidine Nucleosides1

The transfer of the methyl group from methionine to choline and creatine

Pyrimidine Nucleosides. I. A New Route for the Synthesis of Thymine Nucleosides1

Enzymatic deamination and vasodepressor effects of adenosine analogs.

Purine N-Oxides. I. Mono-oxides of Aminopurines1