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D Tooth

Publications and source records attributed to D Tooth.

4 recordsLinked to original sources
PubMed2001

Purification of poly-ubiquitinated proteins by S5a-affinity chromatography.

Poly-ubiquitination, the post-translational covalent conjugation of isopeptide-linked chains of ubiquitin to other target proteins, is the central signal for proteolytic degradation by the 26S proteasome complex. The S5a subunit of the 26S proteasome binds poly-ubiquitin chains containing four or more ubiquitins. We have used an immobilised glutathione-S-transferase (GST)-S5a fusion protein to purify poly-ubiquitinated proteins from mammalian tissues, with the intention of expanding the repertoire of known substrates of the ubiquitin pathway. A complex mixture of poly-ubiquitinated proteins was successfully purified from normal pig brain extract following induction of in vitro ubiquitination. Western blots of two-dimensional gels of this mixture showed at least two diagonal series of ubiquitin-positive spots. Individual spots in each series were separated by approximately 9 kDa suggesting that they represent poly-ubiquitinated proteins with increasing numbers of ubiquitins in the chains. S5a-binding proteins purified from ubiquitination-induced human placental extracts, resolved by sodium dodecyl sulfate polyacrylamide gel electrophoresis and visualised by Coomassie staining, contained a single major species with an apparent denatured molecular mass of approximately 60 kDa. Edman degradation identified this protein as hHR23B, a human homologue of the Saccharomyces cerevisiae DNA repair protein Rad23p. In this case hHR23B is not ubiquitinated but instead contains an intrinsic ubiquitin-like domain at its N-terminus, through which it interacts with S5a (Hiyama, H., et al., J Biol. Chem. 1999, 274, 28,019-28,025).

Animals↗
PubMed1989

Anxiety and study methods in preclinical students: causal relation to examination performance.

Stress and anxiety are substantially raised in many preclinical students in their first year at medical school. Although correlated with poor end-of-year examination performance, anxiety levels did not cause poor performance, but were themselves caused by previous poor performance in sessional examinations. Study habits showed declining deep and strategic approaches, and increasing surface ('rote-learning') approaches. Surface learning correlated with poor end-of-year examination performance, and was a result of previous poor sessional examination performance. Deep learning did not correlate with performance, whereas strategic learning correlated positively with examination success, even when measured 2 years previously during application to medical school.

Achievement↗
PubMedDate not supplied

The reaction of alkylnitronates with glutathione.

Nitroalkanes are agents of occupational importance, and 2-nitropropane has been shown to be mutagenic and hepatotoxic. Here the reaction of alkylnitronates, such as propyl-2-nitronate, with glutathione and other thiol nucleophiles has been studied by using TLC, HPLC, and spectroscopic methods. Propyl-2-nitronate, but not 2-nitropropane, reacted with glutathione in acidic media. The reaction yielded an inseparable mixture of oxidized glutathione and a product that was identified as S-nitrosoglutathione. S-Nitrosoglutathione is known to be generated by reaction of nitrous acid with glutathione and furnishes a characteristic UV spectrum, but its NMR and mass spectral properties are described here for the first time. The 1H NMR spectrum of S-nitrosoglutathione showed in principle the resonance signals of glutathione except that the cysteine beta-protons gave two broad signals shifted downfield by 1 ppm as compared to the resonance frequencies of the glutathione cysteine beta-protons. The interpretation of the spectrum was aided by investigation of the properties of S-nitroso-N-acetylcysteine, the product of the reaction of N-acetylcysteine with propyl-2-nitronate. The nitronates of primary nitroalkanes, such as nitromethane, nitroethane, or 1-nitropropane, did not react with glutathione. The reaction between propyl-2-nitronate and glutathione did not occur at pH values greater than 5; therefore, the relevance of these findings to the disposition of propyl-2-nitronate in vivo is unclear.

Chromatography, High Pressure Liquid↗