Forty-five crystals of complexes between proteins and RNA molecules from the Protein Data Bank have been statistically surveyed for the number of contacts between RNA components (phosphate, ribose and the four bases) and amino acid side chains. Three groups of complexes were defined: the tRNA synthetases; the ribosomal complexes; and a third group containing a variety of complexes. The types of atomic contacts were a priori classified into ionic, neutral H-bond, C-H...O H-bond, or van der Waals interaction. All the contacts were organized into a relational database which allows for statistical analysis. The main conclusions are the following: (i) in all three groups of complexes, the most preferred amino acids (Arg, Asn, Ser, Lys) and the less preferred ones (Ala, Ile, Leu, Val) are the same; Trp and Cys are rarely observed (respectively 15 and 5 amino acids in the ensemble of interfaces); (ii) of the total number of amino acids located at the interfaces 22% are hydrophobic, 40% charged (positive 32%, negative 8%), 30% polar and 8% are Gly; (iii) in ribosomal complexes, phosphate is preferred over ribose, which is preferred over the bases, but there is no significant preference in the other two groups; (iv) there is no significant prevalence of a base type at protein-RNA interfaces, but specifically Arg and Lys display a preference for phosphate over ribose and bases; Pro and Asn prefer bases over ribose and phosphate; Met, Phe and Tyr prefer ribose over phosphate and bases. Further, Ile, Pro, Ser prefer A over the others; Leu prefers C; Asp and Gly prefer G; and Asn prefers U. Considering the contact types, the following conclusions could be drawn: (i) 23% of the contacts are via potential H-bonds (including CH...O H-bonds and ionic interactions), 72% belong to van der Waals interactions and 5% are considered as short contacts; (ii) of all potential H-bonds, 54% are standard, 33% are of the C-H...O type and 13% are ionic; (iii) the Watson-Crick sites of G, O6(G) and principally N2(G) and the hydroxyl group O2' is more often involved in H-bonds than expected; the protein main chain is involved in 32% and the side chains in 68% of the H-bonds; considering the neutral and ionic H-bonds, the following couples are more frequent than expected-base A-Ser, base G-Asp/Glu, base U-Asn. The RNA CH groups interact preferentially with oxygen atoms (62% on the main chain and 19% on the side chains); (iv) the bases are involved in 38% of all H-bonds and more than 26% of the H-bonds have the H donor group on the RNA; (v) the atom O2' is involved in 21% of all H-bonds, a number greater than expected; (vi) amino acids less frequently in direct contact with RNA components interact frequently via their main chain atoms through water molecules with RNA atoms; in contrast, those frequently observed in direct contact, except Ser, use instead their side chain atoms for water bridging interactions.

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This issue, pp 496-8.

Osteoporosis and osteopenia are frequent in HIV-infected males. After ARV initiation, BMD decreased, and bone turnover markers increased, even though the BMD remained stable in non-treated patients. These results underline the impact of HIV treatment on BMD and bone metabolism.

ObjectivesThe care of exposed individuals to HIV remains a challenge regarding follow-up completion and HIV-testing of the partner. Identifying patients with risk of not fulfilling HIV-testing follow-up completion (FC), among patients demanding non-occupational post-exposure prophylaxis (nPEP), may improve clinical practice.MethodsA retrospective chart review was conducted in a single French HIV-infection care center. FC predictors were assessed in a multivariate logistic regression model (Likelihood ratios test).ResultsBetween 2009 and 2013, 646 sexual exposures to HIV were evaluated for nPEP, of which 507 effectively received nPEP (78%). FC rate was 30% (194/646). In the multivariate analysis, FC rates rose with age of exposed individuals (OR, 1.04 [0.25–4.28]; p<0.001) and decreased with the year of sexual exposure (OR, 0.74 [0.65–0.85]; p<0.001). FC was associated with sexual encounter with a sex worker (OR, 4.07 [0.98–16.82]; p<0.001) and nPEP use (OR, 2.69 [2.37–3.06]; p<0.001). nPEP early discontinuation was associated with decreased FC rates (OR, 0.18 [0.08–0.39]; p<0.001). No documented nPEP failure was identified. However, five Men who have Sex with Men (MSM) nPEP recipients for unprotected anal receptive intercourse subsequently seroconverted to HIV more than 6 months after nPEP. Seroconversion to HIV was associated with the lack of FC (p = 0.04) and multiple presentations for nPEP over the study period (p = 0.002).ConclusionsWe identified significant predictors of not fulfilling sequential HIV-testing. They appear to be linked with a self-perceived HIV risk, especially in young adults recently exposed. Enhanced counseling in targeted individuals with high risk behaviors and using smartphone and internet-based strategies may be interesting retention in care options.