Biomaterial Database

Radioprotection of DNA by thiols: relationship between the net charge on a thiol and its ability to protect DNA. 1988

S Zheng, and G L Newton, and G Gonick, and R C Fahey, and J F Ward

Department of Chemistry, University of California, San Diego, La Jolla 92093.

Release of free bases from calf thymus DNA upon irradiation in aerated 0.1 mol dm-3NaClO4 at pH 7 has been measured by HPLC and shown to be markedly influenced by the presence of thiols during irradiation. The ability of thiols to protect DNA was shown to depend upon the net charge (Z) at pH 7 in the order WR 1065 (Z = +2) greater than cysteamine (Z = +1) greater than 2-mercaptoethanol (Z = 0) approximately equal to dithiothreitol (Z = 0) greater than GSH (Z = -1) approximately equal to 2-mercaptoethanesulfonic acid (Z = -1) approximately equal to 2-mercaptosuccinate (Z = -2). A similar dependence of protection upon net charge was found for disulfides: cystamine (Z = +2) greater than 2-mercaptoethyl disulfide (Z = 0) greater than GSSG (Z = -2). Protection by WR 1065, but not by 2-mercaptoethanol or GSH, was found to decrease significantly with increasing ionic strength. Protection by WR 1065 and GSH was not markedly dependent upon pH between pH 6 and 8. The results are explained in terms of electrostatic interaction of the thiols with DNA, leading to high concentrations of cations near DNA, which allow them to scavenge hydroxyl radicals and repair DNA radicals effectively and to low concentrations of anionic thiols near DNA, which limit their effectiveness as protectors. Poly(dG,dC) and calf thymus DNA exhibited comparable release of G and C upon changing from 0.1 to 0.7 mol dm-3 MgSO4. Since this change causes poly(dG,dC), but not calf thymus DNA, to undergo a change from the B-form to the Z-form of DNA, both forms must have a comparable susceptibility to radiation-induced base release.

UI	MeSH Term	Description	Entries
D008623	Mercaptoethanol	A water-soluble thiol derived from hydrogen sulfide and ethanol. It is used as a reducing agent for disulfide bonds and to protect sulfhydryl groups from oxidation.	2-ME,2-Mercaptoethanol,2 Mercaptoethanol
D008624	Mercaptoethylamines	Ethylamines, including CYSTEAMINE, that contain a sulfhydryl group in their structure.
D011837	Radiation-Protective Agents	Drugs used to protect against ionizing radiation. They are usually of interest for use in radiation therapy but have been considered for other purposes, e.g. military.	Radiation Protectant,Radiation Protective Agent,Radiation-Protective Agent,Radiation-Protective Drug,Radioprotective Agent,Radioprotective Agents,Radioprotective Drug,Agents, Radiation-Protective,Radiation Protectants,Radiation Protective Agents,Radiation-Protective Drugs,Radiation-Protective Effect,Radiation-Protective Effects,Radioprotective Drugs,Agent, Radiation Protective,Agent, Radiation-Protective,Agent, Radioprotective,Agents, Radiation Protective,Agents, Radioprotective,Drug, Radiation-Protective,Drug, Radioprotective,Drugs, Radiation-Protective,Drugs, Radioprotective,Effect, Radiation-Protective,Effects, Radiation-Protective,Protectant, Radiation,Protectants, Radiation,Protective Agent, Radiation,Protective Agents, Radiation,Radiation Protective Drug,Radiation Protective Drugs,Radiation Protective Effect,Radiation Protective Effects
D002412	Cations	Positively charged atoms, radicals or groups of atoms which travel to the cathode or negative pole during electrolysis.	Cation
D003543	Cysteamine	A mercaptoethylamine compound that is endogenously derived from the COENZYME A degradative pathway. The fact that cysteamine is readily transported into LYSOSOMES where it reacts with CYSTINE to form cysteine-cysteamine disulfide and CYSTEINE has led to its use in CYSTINE DEPLETING AGENTS for the treatment of CYSTINOSIS.	Cysteinamine,Mercaptamine,2-Aminoethanethiol,Becaptan,Cystagon,Cysteamine Bitartrate,Cysteamine Dihydrochloride,Cysteamine Hydrobromide,Cysteamine Hydrochloride,Cysteamine Maleate (1:1),Cysteamine Tartrate,Cysteamine Tartrate (1:1),Cysteamine Tosylate,Cysteamine, 35S-Labeled,Mercamine,Mercaptoethylamine,beta-Mercaptoethylamine,2 Aminoethanethiol,35S-Labeled Cysteamine,Bitartrate, Cysteamine,Cysteamine, 35S Labeled,Dihydrochloride, Cysteamine,Hydrobromide, Cysteamine,Hydrochloride, Cysteamine,Tartrate, Cysteamine,Tosylate, Cysteamine,beta Mercaptoethylamine
D004229	Dithiothreitol	A reagent commonly used in biochemical studies as a protective agent to prevent the oxidation of SH (thiol) groups and for reducing disulphides to dithiols.	Cleland Reagent,Cleland's Reagent,Sputolysin,Clelands Reagent,Reagent, Cleland,Reagent, Cleland's
D004247	DNA	A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).	DNA, Double-Stranded,Deoxyribonucleic Acid,ds-DNA,DNA, Double Stranded,Double-Stranded DNA,ds DNA
D004249	DNA Damage	Injuries to DNA that introduce deviations from its normal, intact structure and which may, if left unrepaired, result in a MUTATION or a block of DNA REPLICATION. These deviations may be caused by physical or chemical agents and occur by natural or unnatural, introduced circumstances. They include the introduction of illegitimate bases during replication or by deamination or other modification of bases; the loss of a base from the DNA backbone leaving an abasic site; single-strand breaks; double strand breaks; and intrastrand (PYRIMIDINE DIMERS) or interstrand crosslinking. Damage can often be repaired (DNA REPAIR). If the damage is extensive, it can induce APOPTOSIS.	DNA Injury,DNA Lesion,DNA Lesions,Genotoxic Stress,Stress, Genotoxic,Injury, DNA,DNA Injuries
D005978	Glutathione	A tripeptide with many roles in cells. It conjugates to drugs to make them more soluble for excretion, is a cofactor for some enzymes, is involved in protein disulfide bond rearrangement and reduces peroxides.	Reduced Glutathione,gamma-L-Glu-L-Cys-Gly,gamma-L-Glutamyl-L-Cysteinylglycine,Glutathione, Reduced,gamma L Glu L Cys Gly,gamma L Glutamyl L Cysteinylglycine
D000838	Anions	Negatively charged atoms, radicals or groups of atoms which travel to the anode or positive pole during electrolysis.	Anion