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Biomedical subjects

S M Hadi

Publications and source records attributed to S M Hadi.

7 recordsLinked to original sources
PubMed1978

Effect of dimethyl sulfate on the secondary structure of DNA.

Hydroxyapatite chromatography has been used to demonstrate that alkylation of DNA at neutral pH may lead to denaturation under conditions where no significant depurination occurs. Presence of salt has a preventive effect on such denaturation.

Alkylating Agents↗
PubMed1977

Nuclease for DNA apurinic sites in chicken liver.

Chicken liver crude extract produced acid-soluble diphenylamine-positive material in the presence of depurinated and alkylated DNA, while the formation of such material from normal and single stranded DNA was comparatively low. The maximum acid-soluble material produced was not increased further by alkali, indicating that the enzymatic action is mostly directed towards apurinic sites.

Animals↗
PubMed1975

The role of S-adenosylmethionine in the cleavage of deoxyribonucleic acid by the restriction endonuclease from Escherichia coli K.

The restriction endonuclease from Escherichia coli K specifically cleaves foreign DNA in the presence of S-adenosylmethionine, ATP, and Mg2+. The role of S-adenosylmethionine in this reaction has been studied by following the specific binding of the enzyme to unmodified DNA. The results indicate that S-adenosylmethionine acts as an allosteric effector. However, the rate-limiting step in the activation of the enzyme is not the binding of the effector itself, but an event subsequent to it. The interaction of the S-adenosylmethionine with two mutant K restriction endonucleases isolated previously has also been investigated. One of them, which is defective in restriction, can be activated in a manner similar to the wild type enzyme, while the other one, which lacks both restriction and modification activities (due to a mutation in the subunit responsible for DNA recognition), shows no such effect.

Allosteric Regulation↗