Characterization of the cytosolic epoxide hydrolase-catalyzed hydration products from 9,10:12,13-diepoxy stearic esters.

In a previous report we hypothesized that diepoxy fatty methylesters are metabolized to tetraols and/or tetrahydrofurandiols through an epoxydiol intermediate. In this study, p-nitrophenyldiepoxystearate was incubated with affinity-purified liver cytosolic epoxide hydrolase and product formation was monitored by reverse phase HPLC. The diepoxystearate was converted to the corresponding 9,10,12,13-tetraol using a concentrated enzyme (greater than or equal to 100 micrograms/ml). When lower concentration of the enzyme was used, simultaneous elevation of 9,10-epoxy-12,13-dihydroxy and 12,13-epoxy-9,10-dihydroxystearate along with disappearance of tetraol was observed. The epoxydiols were intermediates which could be isolated and cyclized quantitatively to form two chromatographically distinct tetrahydrofurandiols (A with a low Rf value and B with a high Rf value on TLC). Gas chromatographic analysis on a cyclodex-beta capillary column revealed that each compound was composed of two different isomers. The structure of these isomers was 9(12)-oxy-10,13-dihydroxystearate and 10(13)-oxy-9,12-dihydroxystearate using mass spectrometry. Stereochemistry of the aliphatic chain across the tetrahydrofuran moiety was determined by nuclear Overhauser effect spectroscopy. Chemically and enzymatically generated tetrahydrofurandiols had similar retention time on GC and HPLC, and identical mass spectra using the electron impact mode.     

Urinary Metal Levels with Relation to Age,Occupation, and Smoking Habits of Male Inhabitants of Eastern Iran

Biological Trace Element Research - In low-income and middle-income countries such as Iran, smoking is becoming increasingly popular, especially among young people. This has led to additional...     

Elucidating the exact role of engineered CRABPII residues for the formation of a retinal protonated Schiff base

Cellular Retinoic Acid Binding Protein II (CRABPII) has been reengineered to specifically bind and react with all‐trans‐retinal to form a protonated Schiff base. Each step of this process has been dissected and four residues (Lys132, Tyr134, Arg111, and Glu121) within the CRABPII binding site have been identified as crucial for imine formation and/or protonation. The precise role of each residue has been examined through site directed mutagenesis and crystallographic studies. The crystal structure of the R132K:L121E‐CRABPII (PDB‐3I17) double mutant suggests a direct interaction between engineered Glu121 and the native Arg111, which is critical for both Schiff base formation and protonation. Proteins 2009. © 2009 Wiley‐Liss, Inc.     

An axisymmetric single-path model for gas transport in the conducting airways

In conventional one-dimensional single-path models, radially averaged concentration is calculated as a function of time and longitudinal position in the lungs, and coupled convection and diffusion are accounted for with a dispersion coefficient. The axisymmetric single-path model developed in this paper is a two-dimensional model that incorporates convective-diffusion processes in a more fundamental manner by simultaneously solving the Navier-Stokes and continuity equations with the convection-diffusion equation. A single airway path was represented by a series of straight tube segments interconnected by leaky transition regions that provide for flow loss at the airway bifurcations. As a sample application, the model equations were solved by a finite element method to predict the unsteady state dispersion of an inhaled pulse of inert gas along an airway path having dimensions consistent with Weibel's symmetric airway geometry. Assuming steady, incompressible, and laminar flow, a finite element analysis was used to solve for the axisymmetric pressure, velocity and concentration fields. The dispersion calculated from these numerical solutions exhibited good qualitative agreement with the experimental values, but quantitatively was in error by 20%-30% due to the assumption of axial symmetry and the inability of the model to capture the complex recirculatory flows near bifurcations.     

Comparison of axisymmetric and three-dimensional models for gas uptake in a single bifurcation during steady expiration

Reactive gas uptake is predicted and compared in a single bifurcation at steady expiratory flow in terms of Sherwood number using an axisymmetric single-path model (ASPM) and a three-dimensional computational fluid dynamics model (CFDM). ASPM is validated in a two-generation geometry by comparing the average gas-phase mass transfer coefficients with the experimental values. ASPM predicted mass transfer coefficients within 20% of the experimental values. The flow and concentration variables in the ASPM were solved using Galerkin finite element method and in the CFDM using commercial finite element software FIDAP. The simulations were performed for reactive gas flowing at Reynolds numbers ranging from 60 to 350 in both symmetric bifurcation for three bifurcation angles, 30 deg, 70 deg, and 90 deg, and in an asymmetric bifurcation. The numerical models compared with each other qualitatively but quantitatively they were within 0.4-8% due to nonfully developed flow in the parent branch predicted by the CFDM. The radially averaged concentration variation along the axial location matched qualitatively between the CFDM and ASPM but quantitatively they were within 32% due to differences in the flow field. ASPM predictions compared well with the CFDM predictions for an asymmetric bifurcation. These results validate the simplified ASPM and the complex CFDM. ASPM predicts higher Sherwood number with a flat velocity inlet profile compared to a parabolic inlet velocity profile. Sherwood number increases with the inlet average velocity, wall mass transfer coefficient, and bifurcation angle since the boundary layer grows slower in the parent and daughter branches.     

Leptosphaeria maculans AvrLm9: a new player in the game of hide and seek with AvrLm4‐7

Blackleg disease of Brassica napus caused by Leptosphaeria maculans (Lm) is largely controlled by the deployment of race‐specific resistance (R) genes. However, selection pressure exerted by R genes causes Lm to adapt and give rise to new virulent strains through mutation and deletion of effector genes. Therefore, a knowledge of effector gene function is necessary for the effective management of the disease. Here, we report the cloning of Lm effector AvrLm9 which is recognized by the resistance gene Rlm9 in B. napus cultivar Goéland. AvrLm9 was mapped to scaffold 7 of the Lm genome, co‐segregating with the previously reported AvrLm5 (previously known as AvrLmJ1). Comparison of AvrLm5 alleles amongst the 37 re‐sequenced Lm isolates and transgenic complementation identified a single point mutation correlating with the AvrLm9 phenotype. Therefore, we renamed this gene as AvrLm5‐9 to reflect the dual specificity of this locus. Avrlm5‐9 transgenic isolates were avirulent when inoculated on the B. napus cultivar Goéland. The expression of AvrLm5‐9 during infection was monitored by RNA sequencing. The recognition of AvrLm5‐9 by Rlm9 is masked in the presence of AvrLm4‐7, another Lm effector. AvrLm5‐9 and AvrLm4‐7 do not interact, and AvrLm5‐9 is expressed in the presence of AvrLm4‐7. AvrLm5‐9 is the second Lm effector for which host recognition is masked by AvrLm4‐7. An understanding of this complex interaction will provide new opportunities for the engineering of broad‐spectrum recognition.     

Di(1‐naphthyl) methanol ester of carboxylic acids for absolute stereochemical determination

The absolute stereochemistry of chiral carboxylic acids is determined as a di(1‐naphthyl)methanol ester derivative. Computational scoring of conformations favoring either P or M helicity of the naphthyl groups, capable of exciton‐coupled circular dichroic coupling, leads to a predicted stereochemistry for the derivatized carboxylic acids.     

Dissection of the critical binding determinants of cellular retinoic acid binding protein II by mutagenesis and fluorescence binding assay

The binding of retinoic acid to mutants of Cellular Retinoic Acid Binding Protein II (CRABPII) was evaluated to better understand the importance of the direct protein/ligand interactions. The important role of Arg111 for the correct structure and function of the protein was verified and other residues that directly affect retinoic acid binding have been identified. Furthermore, retinoic acid binding to CRABPII mutants that lack all previously identified interacting amino acids was rescued by providing a carboxylic acid dimer partner in the form of a Glu residue. Proteins 2009. © 2008 Wiley‐Liss, Inc.     

Enhancement of exciton coupled circular dichroism with sterically encumbered bis-porphyrin tweezers

Porphyrin tweezers have been successfully used as hosts for the absolute stereochemical determination of a variety of chiral compounds. A set of new porphyrin tweezers with substituted aryl groups on the meso position of the porphyrin rings have been synthesized. The modified tweezers are used as hosts for the stereochemical determination of chiral diamines and carrier-derivatized alpha-chiral carboxylic acids in order to monitor the influence of the various substitutions of the aryl group on the amplitude and sign of the ECCD couplet. t-Butyl substitution at the meta positions of the porphyrin's meso phenyl substituents leads to enhanced ECCD amplitudes.