Discrimination experienced by sexual minority males in Australia: Associations with suicidal ideation and depressive symptoms.

INTRODUCTION: Discrimination has been under-examined as a social determinant of the higher rates of poor mental health experienced by sexual minorities. The objectives of our study were to: 1) assess whether discrimination was independently associated with poor mental health among sexual minority males, and 2) assess the potential mediation role of discrimination in the associations between sexual minority status and poor mental health. METHODS: We used cross-sectional data on 13,230 males aged 18-55 years from the Australian Longitudinal Study on Male Health; bisexual and homosexual males comprised 1.5% and 1.6% of the sample, respectively. We fit Poisson regression and zero-inflated negative binomial regression models to examine suicidality, depressive symptoms and perceived discrimination in the past two years as correlates of suicidality and depressive symptoms. RESULTS: Statistically significant differences were observed in the prevalence of perceived discrimination by sexual orientation (p < 0.001), with the highest prevalence among bisexual (29.3%) and homosexual (40.4%) males, and the lowest prevalence among heterosexual males (18.6%). After adjusting for confounding, bisexual/homosexual males had higher rates of perceived discrimination (IRR = 1.88, p < 0.001), recent suicidal ideation (IRR = 1.51, p = 0.008), lifetime suicide attempt (IRR = 2.09, p < 0.001) and recent depressive symptoms (IRR = 1.34, p < 0.001) than heterosexual males. Analysis of ß-coefficients suggested that discrimination may mediate a small to moderate proportion of the association between sexual minority status and poor mental health. LIMITATIONS: Use of cross-sectional data. CONCLUSION: Poor mental health is more common among sexual minority males, and discrimination may be a contributor to these mental health disparities. Reducing discrimination should be considered as part of a strategy to improve the mental wellbeing of sexual minority males.

The thermodynamics and kinetics of electron transfer in the cytochrome P450cam enzyme system.

In anaerobic environments the first electron transfer in substrate-free P450cam is known to be thermodynamically unfavourable, but in the presence of dioxygen the reduction potential for the reaction shifts positively to make electron transfer thermodynamically favourable. Nevertheless a slower rate of electron transfer is observed in the substrate-free P450cam compared to substrate-bound P450cam. The ferric haem centre in substrate-free P450cam changes from six co-ordinate to five co-ordinate when reduced whereas in substrate-bound P450cam the iron centre remains five co-ordinate in both oxidation states. The slower rate of electron transfer in the substrate-free P450cam is therefore attributed to a larger reorganisation energy as predicted by Marcus theory.

The introduction of a negative charge into the hydrophobic patch of Pseudomonas aeruginosa azurin affects the electron self-exchange rate and the electrochemistry.

By changing Met64 into a glutamate by means of site-directed mutagenesis a negative charge was introduced into the hydrophobic patch of azurin from Pseudomonas aeruginosa. The three-dimensional structure of the protein and the structure of the metal site in particular, appear unaffected by the mutation. The observed change of the midpoint potential of the mutant of 28 mV is ascribed to the deprotonation of Glu64. The electron-self-exchange rate constant equals that of the wild-type protein at pH 4.5 but decreases by almost two orders of magnitude at high pH. Electron transfer is inhibited only when both of the reacting azurin molecules have an ionized glutamate at position 64 in their hydrophobic patch. Electron transfer at a graphite electrode is slowed down by the presence of the negative charge in the hydrophobic patch. The results demonstrate once again that the Cu-ligand His117 in the hydrophobic patch is the likely entry and exit point for electrons. This observation holds both for the (homogeneous) electron-self-exchange reaction in solution as well as for the (heterogenous) reaction at an electrode.

Carbon-2 proton exchange at histidine-41 in bovine erythrocyte superoxide dismutase.

The C-2 proton of one histidine residue in bovine erythrocyte superoxide dismutase is shown to be particularly labile. This residue is identified by tritiation, protein digestion and subsequent peptide 'mapping' as histidine-41. A half-life for the exchange of histidine C-2 1H for 2H in 2H2O as solvent, at pD 8.1 and 40 degrees C, is estimated as approx. 9.2h, by 1H nuclear-magnetic-resonance spectroscopy.

Investigation of the structure of bovine erythrocyte superoxide dismutase by 1H nuclear magnetic resonance spectroscopy.

The 270-MHz 1H nuclear magnetic resonance spectra of the apo, copper(I)-zinc(II), and copper(II)-zinc(II) forms of bovine erythrocyte superoxide dismutase (EC 1.15.1.1) are reported, and assignments of resonances to ten amino acid residues are proposed. The data require that at least four and probably six histidine residues serve as ligands to the metals in each subunit of the enzyme, consistent with x-ray diffraction results. The remaining assigned resonances are associated with His-19, His-41, Tyr-108, and the N-terminal N-acetyl group. The imidazole C(2)H of His-41 exchanges readily at pH greater than 8. The structural implications of the effect of the paramagnetic Cu(II) in the holoenzyme on the proton relaxation times are in reasonable accord with the data from x-ray diffraction studies.