A realistic in silico model for structure/function studies of molybdenum–copper CO dehydrogenase

CO dehydrogenase (CODH) is an environmentally crucial bacterial enzyme that oxidizes CO to CO₂ at a Mo–Cu active site. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the protonation state of the water-derived equatorial ligand coordinated at the Mo-center, as well as the nature of intermediates formed during the catalytic cycle. To address the protonation state of the equatorial ligand, we have developed a realistic in silico QM model (~179 atoms) containing structurally essential residues surrounding the active site. Using our QM model, we examined each plausible combination of redox states (Mo^VI–Cu^I, Mo^V–Cu^II, Mo^V–Cu^I, and Mo^IV–Cu^I) and Mo-coordinated equatorial ligands (O^2?, OH^?, H₂O), as well as the effects of second-sphere residues surrounding the active site. Herein, we present a refined computational model for the Mo(VI) state in which Glu763 acts as an active site base, leading to a MoO₂-like core and a protonated Glu763. Calculated structural and spectroscopic data (hyperfine couplings) are in support of a MoO₂-like core in agreement with XRD data. The calculated two-electron reduction potential (E = ?467 mV vs. SHE) is in reasonable agreement with the experimental value (E = ?558 mV vs. SHE) for the redox couple comprising an equatorial oxo ligand and protonated Glu763 in the Mo^VI–Cu^I state and an equatorial water in the Mo^IV–Cu^I state. We also suggest a potential role of second-sphere residues (e.g., Glu763, Phe390) based on geometric changes observed upon exclusion of these residues in the most plausible oxidized states.     

Nongenomic effects of an anti-idiotypic antibody as an estrogen mimetic in female human and rat osteoblasts

We investigated the early effects of the anti-idiotypic antibody (clone 1D₅), which recognized the estrogen receptor (ER), on cytosolic free calcium concentration ([Ca²⁺]i) and its long term effects on creatine kinase (CK) specific activity in female human and rat osteoblasts. These actions were compared to the known membrane and genomic effects of 17β estradiol (E₂). Like E₂, clone 1D₅ increased within 5 s [Ca²⁺]i in both cell types by two mechanisms: 1) Ca²⁺ influx through voltage-gated Ca²⁺ channels as shown by using EGTA, a chelator of extracellular Ca²⁺, and nifedipine, a Ca²⁺ channel blocker; 2) Ca^2+; mobilization from the endoplasmic reticulum as shown by using phospholipase C inhibitors, such as neomycin and U-73122, which involved a Pertussis toxin-sensitive G-protein. Clone 1D₅ and E₂ stimulated CK specific activity in human and rat osteoblasts with ten fold higher concentrations than those needed for the membrane effects (0.1 μg/ml and 10 pM, respectively). Both effects were gender-specific since testosterone and 5α-dihydotesterone were uneffective. Tamoxifen and Raloxifene, two estrogen nuclear antagonists, inhibited CK response to 1D₅ and E₂ and Ca²⁺ response to 1D₅, but not CA²⁺ response to E₂. By contrast, (Fab′)₂ dimer, a proteolytic fragment of 1D₅ with antagonist properties, inhibited both membrane and genomic effects of 1D₅ and E₂. In conclusion, these results imply that clone 1D₅ has an estrogen like activity both at the membrane and nuclear levels in female human and rat osteoblasts. 1D₅ must therefore interact with membrane binding sites, penetrate the cells, and reach the nuclear receptors by an as yet uncharacterized mechanism. J. Cell. Biochem. 65:53–66. © 1997 Wiley-Liss, Inc.     

Life cycle assessment of waste strategies for used lubricating oil

Purpose

The study aimed to evaluate the environmental impacts of used lubricating oil (ULO) recovery in the largest oil consumer country in Africa, Egypt. The main questions were: What are the impacts of the different waste management strategies for the recovery of used lubricating oil and which waste management strategy is more eco-friendly?

Methods

Life cycle assessment (LCA) was employed to model the environmental impacts of the two waste management approaches for used lubricating oil recovery in Egypt: recycling by re-firing and recovery by co-firing. The model was applied to assess the impacts of one of the largest ULO recovery units in the Middle East and North Africa (MENA) region and the only operating unit in Egypt. The following impact categories were included: global warming potential (GWP), acidification potential (AP), eutrophication potential (EP), carcinogens potential (CP), ecotoxicity potential (ETP), respiratory inorganic formation potential (RIFP), respiratory organic formation potential (ROFP), radiation potential (RP), ozone layer depletion (OLD), mineral depletion (MD), land use (LU) and fossil fuel depletion (FFD).

Results and discussion

Results indicated that recycling by re-refining strategy is more environment-friendly. De-asphalting, de-aromatization and de-waxing processes are the main processes that affect the environmental impacts of lubricating oil production in both strategies, due to the use of hazard materials and toxic solvents in these processes. Fuel gas and fuel oil used as a fuel in the refinery and power units are the main contributors affecting the environmental impacts in case of recycling by re-refining strategy. The highest impacts were detected on FFD, followed by RIFP, GWP, AP, EP, ETP and CP in both strategies; no impacts were detected on RP, OLD and MD.

Conclusions

It can be concluded that recycling by re-refining of ULO is the more eco-friendly approach. This strategy is more energy conservative, saves a diminishing fossil fuel resource and reduces burdens on the environment. ULO containing high percentages of additive remnants such as viscosity index improvers and pour point depressants which represents a valuable resource and its proper management should be given the most attention.

     

Nitrogen-induced variations in leaf gas exchange of spring triticale under field conditions

Nitrogen (N) is the key factor limiting photosynthetic processes and crop yield. Little is known about the response of leaf gas exchange of spring triticale (Triticosecale Wittm.) to N supply. The effect of N fertilizers on different gas exchange variables, i.e., photosynthetic rate (A), transpiration rate (E), stomatal conductance (g _s), instantaneous water use efficiency (WUE) and maximum quantum yield of photosystem II (PSII) (F _v/F _m), chlorophyll index (SPAD, soil–plant analysis development), and the relationship of these variables with yield were studied in spring triticale grown under field conditions. Six treatments of N—0, 90, 180, 90 + 30, 90 + 30 + 30 kg ha^?1 (applied as ammonium nitrate, AN) and one treatment of N 90 + 30 + 30 kg ha^?1 (applied as urea ammonium nitrate solution, UAN) were compared. The analysis of variance showed that throughout the triticale growing season, N fertilization had significant effects on A, WUE, g _s and SPAD. On average, N fertilizer application increased A values by 14–70%. E and F _v/F _m values were not influenced by N fertilization levels. The effect of growth stage and year on gas exchange variables and F _v/F _m and SPAD was found to be significant. At different growth stages, A values varied and maximum ones were reached at BBCH 31–33 (decimal code system of growth stages) and BBCH 59. With aging, values of A decreased independently of N fertilization level. The gas exchange variables were equally affected by both fertilizer forms. The interplay among grain yield, leaf gas exchange variables, F _v/F _m and SPAD of spring triticale was estimated. The statistical analysis showed that grain yield positively and significantly correlated with A and SPAD values throughout the growing season.     

Different pathways of choline metabolism in two choline-independent strains of Streptococcus pneumoniae and their impact on virulence

The two recently characterized Streptococcus pneumoniae strains—R6Chi and R6Cho⁻—that have lost the unique auxotrophic requirement of this bacterial species for choline differ in their mechanisms of choline independence. In strain R6Chi the mechanism is caused by a point mutation in tacF, a gene that is part of the pneumococcal lic2 operon, which is essential for growth and survival of the bacteria. Cultures of lic2 mutants of the encapsulated strain D39Chi growing in choline-containing medium formed long chains, did not autolyze, had no choline in their cell wall, and were completely avirulent in the mouse intraperitoneal model. In contrast, while the Cho⁻ strain carried a complete pneumococcal lic2 operon and had no mutations in the tacF gene, deletion of the entire lic2 operon had no effect on the growth or phenotype of strain Cho⁻. These observations suggest that the biochemical functions normally dependent on determinants of the pneumococcal lic2 operon may also be carried out in strain Cho⁻ by a second set of genetic elements imported from Streptococcus oralis, the choline-independent streptococcal strain that served as the DNA donor in the heterologous transformation event that produced strain R6Cho⁻. The identification in R6Cho⁻ of a large (20-kb) S. oralis DNA insert carrying both tacF and licD genes confirms this prediction and suggests that these heterologous elements may represent a “backup” system capable of catalyzing P-choline incorporation and export of teichoic acid chains under conditions in which the native lic2 operon is not functional.     

Role of nitric oxide in D-galactosamine-induced cell death and its protection by PGE1 in cultured hepatocytes.

Prostaglandin E(1) (PGE(1)) reduces cell death in experimental and clinical manifestations of liver dysfunction. Nitric oxide (NO) has been shown to exert a protective or noxious effect in different experimental models of liver injury. The aim of the present study was to investigate the role of NO during PGE(1) protection against D-galactosamine (D-GalN) citotoxicity in cultured hepatocytes. PGE(1) was preadministered to D-GalN-treated hepatocytes. The role of NO in our system was assessed by iNOS inhibition and a NO donor. Different parameters related to apoptosis and necrosis, NO production such as nitrite+nitrate (NO(x)) release, iNOS expression, and NF-kappaB activation in hepatocytes were evaluated. The inhibition of iNOS reduced apoptosis induced by D-GalN in hepatocytes. PGE(1) protection against D-GalN injury was associated with its capacity to reduce iNOS expression and NO production induced by D-GalN. Nevertheless, iNOS inhibition showed that protection by PGE(1) was also mediated by NO. Low concentrations of a NO donor reduced D-GalN injury with a decrease in the extracellular NO(x) concentration. High concentrations of the NO donor enhanced NO(x) concentration and increased cell death by D-GalN. The present study suggests that low NO production induced by PGE(1) preadministration reduces D-GalN-induced cell death through its capacity to reduce iNOS expression and NO production caused by the hepatotoxin.     

Versatility of choline metabolism and choline-binding proteins in Streptococcus pneumoniae and commensal streptococci

The pneumococcal choline-containing teichoic acids are targeted by choline-binding proteins (CBPs), major surface components implicated in the interaction with host cells and bacterial cell physiology. CBPs also occur in closely related commensal species, Streptococcus oralis and Streptococcus mitis , and many strains of these species contain choline in their cell wall. Physiologically relevant CBPs including cell wall lytic enzymes are highly conserved between Streptococcus pneumoniae and S. mitis . In contrast, the virulence-associated CBPs, CbpA, PspA and PcpA, are S. pneumoniae specific and are thus relevant for the characteristic properties of this species.     

Structure–activity relationship studies of curcumin analogues

Two series of curcumin analogues, a total of twenty-four compounds, were synthesized and evaluated. The most potent compound, compound 23, showed potent growth inhibitory activities on both prostate and breast cancer lines with IC₅₀ values in sub-micromolar range, fifty times more potent than curcumin. Curcumin analogues might be potential anti-tumor agents for breast and prostate cancers.     

A genome-wide genetic signature of Jewish ancestry perfectly separates individuals with and without full Jewish ancestry in a large random sample of European Americans

Background  

It was recently shown that the genetic distinction between self-identified Ashkenazi Jewish and non-Jewish individuals is a prominent component of genome-wide patterns of genetic variation in European Americans. No study however has yet assessed how accurately self-identified (Ashkenazi) Jewish ancestry can be inferred from genomic information, nor whether the degree of Jewish ancestry can be inferred among individuals with fewer than four Jewish grandparents.