Stereoselectivity of Isoflurane in Adhesion Molecule Leukocyte Function-Associated Antigen-1

Background: Isoflurane in clinical use is a racemate of S- and R-isoflurane. Previous studies have demonstrated that the effects of S-isoflurane on relevant anesthetic targets might be modestly stronger (less than 2-fold) than R-isoflurane. The X-ray crystallographic structure of the immunological target, leukocyte function-associated antigen-1 (LFA-1) with racemic isoflurane suggested that only S-isoflurane bound specifically to this protein. If so, the use of specific isoflurane enantiomers may have advantage in the surgical settings where a wide range of inflammatory responses is expected to occur. Here, we have further tested the hypothesis that isoflurane enantioselectivity is apparent in solution binding and functional studies. Methods: First, binding of isoflurane enantiomers to LFA-1 was studied using 1-aminoanthracene (1-AMA) displacement assays. The binding site of each enantiomer on LFA-1 was studied using the docking program GLIDE. Functional studies employed the flow-cytometry based ICAM binding assay. Results: Both enantiomers decreased 1-AMA fluorescence signal (at 520 nm), indicating that both competed with 1-AMA and bound to the αL I domain. The docking simulation demonstrated that both enantiomers bound to the LFA-1 “lovastatin site.” ICAM binding assays showed that S-isoflurane inhibited more potently than R-isoflurane, consistent with the result of 1-AMA competition assay. Conclusions: In contrast with the x-ray crystallography, both enantiomers bound to and inhibited LFA-1. S-isoflurane showed slight preference over R-isoflurane

Conservation of Carbohydrate Binding Interfaces — Evidence of Human HBGA Selection in Norovirus Evolution

Human noroviruses are the major viral pathogens of epidemic acute gastroenteritis. These genetically diverse viruses comprise two major genogroups (GI and GII) and approximately 30 genotypes. Noroviruses recognize human histo-blood group antigens (HBGAs) in a diverse, strain-specific manner. Recently the crystal structures of the HBGA-binding interfaces of the GI Norwalk virus and the GII VA387 have been determined, which allows us to examine the genetic and structural relationships of the HBGA-binding interfaces of noroviruses with variable HBGA-binding patterns. Our hypothesis is that, if HBGAs are the viral receptors necessary for norovirus infection and spread, their binding interfaces should be under a selection pressure in the evolution of noroviruses.Structural comparison of the HBGA-binding interfaces of the two noroviruses has revealed shared features but significant differences in the location, sequence composition, and HBGA-binding modes. On the other hand, the primary sequences of the HBGA-binding interfaces are highly conserved among strains within each genogroup. The roles of critical residues within the binding sites have been verified by site-directed mutagenesis followed by functional analysis of strains with variable HBGA-binding patterns.Our data indicate that the human HBGAs are an important factor in norovirus evolution. Each of the two major genogroups represents an evolutionary lineage characterized by distinct genetic traits. Functional convergence of strains with the same HBGA targets subsequently resulted in acquisition of analogous HBGA binding interfaces in the two genogroups that share an overall structural similarity, despite their distinct locations and amino acid compositions. On the other hand, divergent evolution may have contributed to the observed overall differences between and within the two lineages. Thus, both divergent and convergent evolution, as well as the polymorphic human HBGAs, likely contribute to the diversity of noroviruses. The finding of genogroup-specific conservation of HBGA binding interfaces will facilitate the development of rational strategies to control and prevent norovirus-associated gastroenteritis

Mortality among People Living with HIV and AIDS in China: Implications for Enhancing Linkage.

To assess the patterns and predictors of AIDS-related mortality and identify its correlates among adult people living with HIV/AIDS (PLWHA) in China, a retrospective record-based cohort study was conducted among 18 years or older PLWHA, who had at least one follow up reported to the national database between January-1989 and June-2012. Cumulative Incidence Function was used to calculate AIDS-related mortality rate. Gray's test was used to determine the variation in cumulative incidence across strata. The Fine and Gray model was used to measure the burden of cumulative incidence of AIDS-related mortality and strength of its association with potential correlates. Among 375,629 patients, 107,634 died during study period, of which 54,759 (50.87%) deaths were AIDS-related. Cumulative mortality rates of AIDS-related death at one, two, five, 10 and 15 years post-diagnosis were 5.7%, 8.2%, 14.3%, 22.9% and 30.9%, respectively. Among PLWHA, male gender, ethnic minority and having AIDS were associated with significantly higher mortality. Further, homosexual transmission, being on ART and increasing CD4-testing frequency were associated with lower mortality. To reduce mortality among PLWHA, efficient interventions targeting males, ethnic minority, heterosexually infected and AIDS patients should be combined with immunologic monitoring, enhancement of coverage of HIV-testing and ART

Recognition of Anesthetic Barbiturates by a Protein Binding Site: A High Resolution Structural Analysis

Barbiturates potentiate GABA actions at the GABAA receptor and act as central nervous system depressants that can induce effects ranging from sedation to general anesthesia. No structural information has been available about how barbiturates are recognized by their protein targets. For this reason, we tested whether these drugs were able to bind specifically to horse spleen apoferritin, a model protein that has previously been shown to bind many anesthetic agents with affinities that are closely correlated with anesthetic potency. Thiopental, pentobarbital, and phenobarbital were all found to bind to apoferritin with affinities ranging from 10–500 µM, approximately matching the concentrations required to produce anesthetic and GABAergic responses. X-ray crystal structures were determined for the complexes of apoferritin with thiopental and pentobarbital at resolutions of 1.9 and 2.0 Å, respectively. These structures reveal that the barbiturates bind to a cavity in the apoferritin shell that also binds haloalkanes, halogenated ethers, and propofol. Unlike these other general anesthetics, however, which rely entirely upon van der Waals interactions and the hydrophobic effect for recognition, the barbiturates are recognized in the apoferritin site using a mixture of both polar and nonpolar interactions. These results suggest that any protein binding site that is able to recognize and respond to the chemically and structurally diverse set of compounds used as general anesthetics is likely to include a versatile mixture of both polar and hydrophobic elements

Comparison of Pretreatment Methods for Production of Ethanol from Sugarcane Bagasse

Sugarcane bagasse (SCB) was modified by steam explosion pretreatment at 190 °C for 10 min and 210 °C for 5 min using green liquor (GL) combined with hydrogen peroxide (GL-H2O2) and ethanol (GL-Ethanol) for simultaneous saccharification and fermentation (SSF)-based ethanol production. The results showed that 85.02% and 100% of hemicelluloses were solubilized by steam explosion pretreatment at 190 °C for 10 min and 210 °C for 5 min, respectively. Moreover, 20.08% and 73.77% of the lignin was removed through GL-H2O2 and GL-Ethanol pretreatments, respectively. The steam explosion pretreatments greatly improved the specific surface area of the SCB and led to the highest ethanol yield of 92.20% at 190 °C for 10 min and 93.19% of 210 °C for 5 min, respectively. In addition, the ethanol yield reached 72.58% for the GL-Ethanol pretreatment, and about 70% of active lignin could be recovered from the pretreatment liquid. When the GL-H2O2 pretreatment was used, the maximum ethanol yield of 20.92% was achieved