Decoupled Roles for the Atypical,Bifurcated Binding Pocket of the ybfF Hydrolase

Serine hydrolases have diverse intracellular substrates, biological functions, and structural plasticity, and are thus important for biocatalyst design. Amongst serine hydrolases, the recently described ybfF enzyme family are promising novel biocatalysts with an unusual bifurcated substrate‐binding cleft and the ability to recognize commercially relevant substrates. We characterized in detail the substrate selectivity of a novel ybfF enzyme from Vibrio cholerae (Vc‐ybfF) by using a 21‐member library of fluorogenic ester substrates. We assigned the roles of the two substrate‐binding clefts in controlling the substrate selectivity and folded stability of Vc‐ybfF by comprehensive substitution analysis. The overall substrate preference of Vc‐ybfF was for short polar chains, but it retained significant activity with a range of cyclic and extended esters. This broad substrate specificity combined with the substitutional analysis demonstrates that the larger binding cleft controls the substrate specificity of Vc‐ybfF. Key selectivity residues (Tyr116, Arg120, Tyr209) are also located at the larger binding pocket and control the substrate specificity profile. In the structure of ybfF the narrower binding cleft contains water molecules prepositioned for hydrolysis, but based on substitution this cleft showed only minimal contribution to catalysis. Instead, the residues surrounding the narrow binding cleft and at the entrance to the binding pocket contributed significantly to the folded stability of Vc‐ybfF. The relative contributions of each cleft of the binding pocket to the catalytic activity and folded stability of Vc‐ybfF provide a valuable map for designing future biocatalysts based on the ybfF scaffold.     

Absence of detectable human herpesvirus 8 in the semen of human immunodeficiency virus-infected men without Kaposi's sarcoma

The prevalence of human herpesvirus 8 (HHV-8)/Kaposi's sarcoma (KS)-associated herpesvirus was investigated in the semen of 99 human immunodeficiency virus (HIV)-infected men (median CD4 cell count, 357/mm3) by use of a polymerase chain reaction (PCR) assay capable of detecting <10 copies of HHV-8 DNA. Of the subjects, 95 (96%) self-identified as men who have sex with men (MSM), and 3 had a history of clinical KS. Seminal cell specimens were negative for HHV-8 in 98 subjects. None of the 26 without KS (27.1% of 96 tested) who were seropositive for HHV-8 by IFA for latency-associated nuclear antigens had HHV-8 detected in their semen. The only subject with any evidence for seminal HHV-8 DNA was seropositive for HHV-8 and had active KS. HHV-8 was detected in 10 (10.4%) of 96 peripheral blood mononuclear cell specimens. The prevalence of HHV-8 DNA by PCR in semen of HIV-infected MSM without KS is low.     

When your patient uses denial

There are may factors to consider when denial is encountered in a patient situation. Denial is a simple concept but is complicated by ego-maintaining mechanisms that denial may produce. It is important to evaluate each individual situation in order to identify suitable approaches for the situation. Denial may not be something that the nurse should take away since it can serve an important balancing function between depression and wellness.     

A generic morphological model of the anatomic variability in the m. flexor digitorum profundus, m. flexor pollicis longus and mm. lumbricales complex

This study examined the productivity and representation of past-tense marking in children with and without specific language impairment (SLI). Participants were 11 6-year-olds with SLI, 11 age-matched controls, and 11 MLU-matched controls. Regular and irregular verbs were used to examine the productivity of regular marking. Past-tense representation was examined by asking children to inflect homophonous pairs of denominal and irregular root verbs. All three groups demonstrated productive marking of past tense, although as expected the accuracy of the impaired groups was less than that of earlier control group. Patterns of past-tense marking as a function of a word's phonological composition and inflectional frequency were the same for the SLI- and MLU-matched groups, and all children presented a past-tense system that was sensitive to grammatical structure. The findings replicate previous research of the SLI morphological system and provide additional specification of these children's morphological strengths and weaknesses. Strengths include the children's sensitivity to grammatical and phonological characteristics of the lexicon; weaknesses include limited productivity of regular past-tense marking and a greater sensitivity to frequency manipulations as compared to normally developing children. Results are discussed in terms of the nature of the SLI profile. They also are used to evaluate the theoretical model on which the study was based.