Clarke Stevenson

ALKALI-LABILE PHOTOLESIONS MAPPING TO PURINE SITES IN ULTRAVIOLET-IRRADIATED DNA

Gel sequencing experiments with the 5′‐ and 3′‐end‐labeled oligonucleotides d(A3GA4GA5GA6GA3G) and d(AT) 10 have demonstrated that dimeric adenine photoproducts and thymine‐adenine photoadducts constitute alkali‐labile lesions in UV‐irradiated DNA. On treatment with hot piperidine, DNA strand breakage occurs predominantly at the sites of 5′‐adenines in the dimeric photoproducts and of 3′‐adenines in the thymine‐adenine photoadducts. With 5′‐end‐labeled oligonucleotides of mixed sequence, major UV‐induced loci for alkaline cleavage map to purine bases flanked on their 5′‐side by two pyrimidines. This behavior does not arise from enhanced photoreactivity of purines in this sequence context as has been inferred from photofootprinting studies. Instead, as shown by 3′‐labeling and selective substitution with 5‐methylcytosine, it results from the anomalous electrophoretic mobility of 5′‐end‐labeled fragments produced by alkaline cleavage of DNA at adjacent pyrimidine (6‐4) pyrimidone photoproducts.

Oxidation of guanine Nucleosides to 4-amidinocarbamoyl-5-hydroxyimidazoles by dimethyldioxirane

Abstract Final oxidation products generated from guanosine and 2′-deoxyguanosine by reaction with dimethyldioxirane have been identified as 4-amidinocarbamoyl-5-hydroxyimidazoles.

Rapid hydrolytic cleavage of the mRNA model compound HPNP by glycine based macrocyclic lanthanide ribonuclease mimicsElectronic supplementary information (EI) available: full experimental details, Fig. S1???S6. See http://www.rsc.org./suppdata/cc/b2/b205349g/

The lanthanide ion based macrocyclic complexes 1.Ln mimic the hydrophobic nature of ribonucleases, where the lanthanide ions induce the formation of a hydrophobic cavity for 1, giving rise to a large order of magnitude enhancement in the hydrolytic cleavage of HPNP.