The UvrD303 Hyper-helicase Exhibits Increased Processivity

DNA helicases use energy derived from nucleoside 5′-triphosphate hydrolysis to catalyze the separation of double-stranded DNA into single-stranded intermediates for replication, recombination, and repair. Escherichia coli helicase II (UvrD) functions in methyl-directed mismatch repair, nucleotide excision repair, and homologous recombination. A previously discovered 2-amino acid substitution of residues 403 and 404 (both Asp → Ala) in the 2B subdomain of UvrD (uvrD303) confers an antimutator and UV-sensitive phenotype on cells expressing this allele. The purified protein exhibits a “hyper-helicase” unwinding activity in vitro. Using rapid quench, pre-steady state kinetic experiments we show the increased helicase activity of UvrD303 is due to an increase in the processivity of the unwinding reaction. We suggest that this mutation in the 2B subdomain results in a weakened interaction with the 1B subdomain, allowing the helicase to adopt a more open conformation. This is consistent with the idea that the 2B subdomain may have an autoregulatory role. The UvrD303 mutation may enable the helicase to unwind DNA via a “strand displacement” mechanism, which is similar to the mechanism used to processively translocate along single-stranded DNA, and the increased unwinding processivity may contribute directly to the antimutator phenotype.     

Particulate matter and bacteria characteristics of the Middle East Dust (MED) storms over Ahvaz,Iran

The Middle East Dust storms have greatly affected the south and west parts of Iran during the last decade. The main purpose of this study was to examine and compare culturable airborne bacteria concentration in particulate matter (PM) during normal, semi-dust, and dust event days in different places and seasons in Ahvaz from November 2011 to May 2012. Sampling was performed every 6 days and on dust event days at different sampling stations. The overall mean concentrations of PM₁₀, PM_2.5, and PM₁ for the entire study period were 598.92, 114.8, and 34.5 μg/m³, respectively. The PM concentrations during the dust event days were much higher than normal and semi-dust event days. The highest mean PM concentrations were observed in March 2011. The low PM_2.5/PM₁₀ ratios indicate that these PM are mostly originating from natural sources such as dust storms. The overall mean concentration of total bacteria during the study period was 620.6 CFU/m³. The greatest bacterial concentrations were observed during dust event days and at areas with high traffic and more human activities compared with normal days and greener areas. The percentage of gram-positive bacteria was significantly higher than that during the study period (89 vs 11 %). During this study, 26 genera of culturable bacteria were identified from all the sampling stations. The most dominant genera in all sampling stations were Streptomyces, Bacillus, Kocuria, Corynebacterium, and Paenibacillus. The results also showed that there were positive correlations between PM and bacterial concentrations during the study period (p < 0.05).     

Biochemical characterization of the decaprenyl diphosphate synthase of Rhodobacter sphaeroides for coenzyme Q10 production

Coenzyme Q₁₀ (CoQ₁₀), like other CoQs of various organisms, plays indispensable roles not only in energy generation but also in several other processes required for cells’ survival. In this study, a gene encoding for a decaprenyl diphosphate synthase (Rsdds) was cloned from Rhodobacter sphaeroides in Escherichia coli. The in vivo catalytic activity and product specificity of Rsdds were compared with those of a counterpart enzyme from Agrobacterium tumefaciens (Atdds) in E. coli as a heterologous host. In contrast with Atdds, Rsdds showed lower catalytic activity but higher product specificity for CoQ₁₀ production, as indicated by the amount of CoQ₉ formation. The higher product specificity of Rsdds was also confirmed by utilizing both Rsdds and Atdds for in vitro synthesis of polyprenyl diphosphates. Thin layer chromatography indicated that the Rsdds enzyme resulted in relatively much less solanesyl diphosphate formation. The purified Rsdds catalyzed the addition of isopentenyl diphosphate to dimethyl allyl diphosphate, geranyl diphosphate, ω,E,E-farnesyl diphosphate (FPP), and ω,E,E,E-geranylgeranyl diphosphate as priming substrates. The kinetic parameters of V _max (pmol/min), K _M (μM), k _cat (1/min), and k _cat /K _M of the enzyme using FPP as the most appropriate substrate were determined to be 264.6, 13.1, 8.8, and 0.67, respectively.     

Relative contribution of vegetation types to regional biodiversity in Central Zagross forests of Iran

Managers in conservation biology are continually faced with the dilemma of needing to demonstrate which areas should receive conservation priority based on the diversity of species contained. Darenasab (Hashtadpahloo) forest catchment with dominated oak species in Mediterranean forests of Zagross in Iran was chosen as a case study. In order to estimate plant species richness in different vegetation types at landscape level, field method that sample both trees and herbs strata simultaneously (modified multi-scale Whittaker plots) was used to make species–area curves. Twenty-one modified multi-scale Whittaker plots (250 m² area) were located randomly in four vegetation types. Three species–area, species–log (area) and log (species)–log (area) curves models were constructed. The log (species)–log (area) model had the highest adjusted r² among others. Based on Jaccard’s coefficient, the pure oak vegetation type was the most heterogeneous (22% overlap), and the cushion plants vegetation type is the most homogeneous (29% overlap). The slope of species–area curves had the least range (0.05) and the slope of species–log (area) curves had the largest range (4.38). When the slopes of species–log (area) curves divided by mean Jaccard’s coefficient, the species–log (area) curves estimated values closest to those observed. The index of vegetation types contribution to regional diversity for determining conservation priority in off-reserve area, based on ranking of the observed mean species per plots, slopes of the species–log (area) curves, mean of Jaccard’s coefficient, mean unique species per plot, and the number of threatened species in each vegetation types were calculated. This composite index may provide a scientific method to rank vegetation types with high conservation value.     

Boundary layer considerations in a multi-layer model for LDL accumulation

Abstract

Boundary layer effects for Low-Density Lipoprotein (LDL) concentration problems in a multi-layer artery model are analyzed in this work. Both a straight artery and aorta-iliac bifurcation are analyzed. Mass, momentum and species governing equations are based on the porous media theory and solved with the commercial finite-element based code COMSOL Multiphysics. For the straight artery, various inlet velocities, arterial sizes and intramural pressure values are investigated. Results are presented in terms of concentration profiles close to the lumen/endothelium interface and boundary layer thickness. It is shown that the boundary layer is affected by all of the three analyzed parameters. The results in this work will further clarify the concentration polarization effects imposed by the arterial wall.     

Thrips (Insecta,Thysanoptera) of Iran: a revised and?updated checklist

In Iran, as a result of recent changes in nomenclature 201 species and one species group of the insect Order Thysanoptera, are here listed in 70 genera and five families. In considering species listed previously from this country, the presence of 7 species is considered not confirmed, and 12 species are excluded from the Iranian list. Problems in the study of Iranian Thysanoptera are discussed briefly.     

A new species of Haplothrips from southern Iran (Thysanoptera,Phlaeothripidae)

Haplothrips herajius sp. n. is described from leaves and flowers of a species of Suaeda in the south of Fars Province, Iran. This is the second Iranian species of Haplothrips with the unusual character state of extra setae on the metanotum. Information on variation in color and structure of the new species is provided. The similarities and host plant associations of this new species and Haplothrips kermanensis are discussed,as both are phytophagous on species of Chenopodiaceae.     

Arterial vasodilatory and ventricular diastolic reserves determine the stroke volume response to exercise in elderly female hypertensive patients

Elderly female hypertensives with arterial stiffening constitute a majority of patients with heart failure with preserved ejection fraction (HFpEF), a condition characterized by inability to increase cardiac stroke volume (SV) with physical exercise. As SV is determined by the interaction between the left ventricle (LV) and its load, we wished to study the role of arterial hemodynamics for exertional SV reserve in patients at high risk of HFpEF. Twenty-one elderly (67 ± 9 yr) female hypertensive patients were studied at rest and during supine bicycle stress using echocardiography including pulsed-wave Doppler to record flow in the LV outflow tract and arterial tonometry for central arterial pressure waveforms. Arterial compliance was estimated based on an exponential relationship between pressure and volume. The ratio of aortic pressure-to-flow in early systole was used to derive characteristic impedance, which was subsequently subtracted from total resistance (mean arterial pressure/cardiac output) to yield systemic vascular resistance (SVR). It was found that patients with depressed SV reserve (NoRes; reserve <15%; n = 10) showed decreased arterial compliance during exercise, while patients with SV reserve ≥15% (Res; n = 11) showed increased compliance. Exercise produced parallel increases in LV end-diastolic volume and arterial volume in Res patients while NoRes patients exhibited a lesser decrease in SVR and a drop in effective arterial volume. Poor SV reserve in elderly female hypertensives is due to simultaneous failure of LV preload and arterial vasodilatory reserves. Abnormal arterial function contributes to a high risk of HFpEF in these patients.     

Dietary Supplementation of Potential Probiotics Bacillus subtilis,Bacillus licheniformis,and Saccharomyces cerevisiae and Synbiotic Improves Growth Performance and Immune Responses by Modulation in Intestinal System in Broiler Chicks Challenged with Salmonella Typhimurium

Probiotics and Antimicrobial Proteins - This study evaluates the effects of probiotics and synbiotics on the performance, immune responses, and intestinal morphology, and the expression of...     

The role of the S1 binding site of carboxypeptidase M in substrate specificity and turn-over

The influence of the P1 amino acid on the substrate selectivity, the catalytic parameters K(m) and k(cat), of carboxypeptidase M (CPM) (E.C. 3.4.17.12) was systematically studied using a series of benzoyl-Xaa-Arg substrates. CPM had the highest catalytic efficiency (k(cat)/K(m)) for substrates with Met, Ala and aromatic amino acids in the penultimate position and the lowest with amino acids with branched side-chains. Substrates with Pro in P1 were not cleaved in similar conditions. The P1 substrate preference of CPM differed from that of two other members of the carboxypeptidase family, CPN (CPN/CPE subfamily) and CPB (CPA/CPB subfamily). Aromatic P1 residues discriminated most between CPM and CPN. The type of P2 residue also influenced the k(cat) and K(m) of CPM. Extending the substrate up to P7 had little effect on the catalytic parameters. The substrates were modelled in the active site of CPM. The results indicate that P1-S1 interactions play a role in substrate binding and turn-over.