Benzene oxidation under sulfate-reducing conditions in columns simulating in situ conditions

The oxidation of benzene under sulfate-reducing conditions was examined in column and batch experiments under close to in situ conditions. Mass balances and degradation rates for benzene oxidation were determined in four sand and four lava granules filled columns percolated with groundwater from an anoxic benzene-contaminated aquifer. The stoichiometry of oxidized benzene, produced hydrogen carbonate and reduced sulfate correlated well with the theoretical equation for mineralization of benzene with sulfate as electron acceptor. Mean retention times of water in four columns were determined using radon (²²²Rn) as tracer. The retention times were used to calculate average benzene oxidation rates of 8–36 μM benzene day⁻¹. Benzene-degrading, sulfide-producing microcosms were successfully established from sand material of all sand filled columns, strongly indicating that the columns were colonized by anoxic benzene-degrading microorganisms. In general, these data indicate a high potential for Natural Attenuation of benzene under sulfate-reducing conditions at the field site Zeitz. In spite of this existing potential to degrade benzene with sulfate as electron acceptor, the benzene plume at the field site is much longer than expected if benzene would be degraded at the rates observed in the column experiment, indicating that benzene oxidation under sulfate-reducing conditions is limited in situ.     

Characteristic features of adaptation to experimental conditions in primates with various initial keeping conditions

Ethological study of emotional state and behavior was carried out in male macaques of two species (Macaca mulatta and Macaca fascicularis), which were divided in three groups according to their initial keeping: isolated, family, and gregarious. During instrumental conditioning, the initial keeping was changed for identical conditions (individual caging or sitting in a primatological chair). It was shown that adaptation to stress associated with a sharp enviromental change depended on initial keeping conditions. Monkeys brought up in family with experience of both intra- and interspecies interactions (for example, monkey--human) had the highest adaptation and learning abilities. Individual and gregarious keeping of monkeys impoverished their individual experience, and their adaptation to experimental conditions required additional efforts. The learning of individually caged monkeys was successful, if their keeping conditions were not changed. Initially gregarious monkeys were successfully trained after their habituation to contact with humans.     

Metabolic conditions in Chlorella

1. The effect of nitrate reduction and assimilation on the CO(2)/O(2) quotient of gas exchange has been used as an index of the relative rates of carbon and nitrogen assimilation in Chlorella pyrenoidosa. Changes in over-all metabolism induced by starvation, high light intensity, and nitrogen deficiency have been studied in comparison with the metabolism of cells growing at light-limiting intensities. 2. Starvation, which results in depletion of carbohydrate reserves, gives rise to a high CO(2)/O(2) quotient ( approximately 0.9) during photosynthesis and, therefore, a high C/N assimilation ratio. Starved cells apparently restore their normal C/N ratio before becoming growing cells. 3. Under photosynthesis-saturating light intensities cells show the high CO(2)/O(2) quotient (0.9) indicative of a high C/N assimilation ratio. Return to low light intensities is followed by the abnormally low CO(2)/O(2) quotient ( approximately 0.4) of a low C/N assimilation ratio. High light intensity apparently gives rise to a condition of a limiting rate of nitrogen assimilation and to an overflow metabolism analogous to that found in other microorganisms. 4. Nitrogen deficiency leads to a completely carbohydrate metabolism in short time experiments and makes still more pronounced the effects characteristic of high light intensity alone. 5. Considerations of nutritional economy sustain the experimental evidence in establishing the metabolism of cells growing under light-limiting intensities as the normal or reference metabolic condition in Chlorella.     

Evapotranspiration under advective conditions

Arid and semi-arid regions are heterogeneous landscapes in which irrigated fields are surrounded by arid areas. The advection of sensible heat flux from dry surfaces is a significant source of energy that has to be taken into consideration when evaluating the evaporation from crops growing in these areas. The basic requirement of most of the common methods for estimating evapotranspiration [Bowen ratio, aerodynamic and Penman–Monteith (PM) equation] is that the horizontal fluxes of sensible and latent heat are negligible when compared to the corresponding vertical fluxes. We carried out measurements above an irrigated tomato field in a desert area. Latent and sensible heat fluxes were measured using a four-level Bowen machine with aspirated psychrometers. Our results indicate that under advective conditions only measurements carried out in the lowest layer are satisfactory for the estimation of latent heat fluxes and that the use of the PM equation with an appropriately parameterized canopy resistance may be preferable.This work was carried out by the author during her sojourn at the Wyler Department for Drayland Agriculture, Jacob Blaustein Institute for Desert Research, Ben Gurion University of the Negev, Israel.Manufacturers names are provided for the benefit of the reader and do not imply endorsement by the authors.     

High-throughput identification of purification conditions leads to preliminary crystallization conditions for three inner membrane proteins

Abstract

An important factor in the crystallization, and subsequent structural determination, of integral membrane proteins is the ability to produce a stable and monodisperse solution of the protein. Obtaining the correct purification detergent to achieve this can be laborious and is often serendipitous. In this study, high-throughput methods are used to analyze the suitability of eight different detergents on the stability of 12 inner transmembrane proteins from Escherichia coli. The best results obtained from the small-scale experiments were scaled up, the aggregation state of the proteins assessed, and all monodisperse protein solutions entered into crystallization trials. This resulted in preliminary crystallization hits for three inner membrane proteins: XylH, PgpB and YjdL and this study reports the methods, purification procedures and crystallization conditions used to achieve this.     

High-throughput identification of purification conditions leads to preliminary crystallization conditions for three inner membrane proteins

An important factor in the crystallization, and subsequent structural determination, of integral membrane proteins is the ability to produce a stable and monodisperse solution of the protein. Obtaining the correct purification detergent to achieve this can be laborious and is often serendipitous. In this study, high-throughput methods are used to analyze the suitability of eight different detergents on the stability of 12 inner transmembrane proteins from Escherichia coli. The best results obtained from the small-scale experiments were scaled up, the aggregation state of the proteins assessed, and all monodisperse protein solutions entered into crystallization trials. This resulted in preliminary crystallization hits for three inner membrane proteins: XylH, PgpB and YjdL and this study reports the methods, purification procedures and crystallization conditions used to achieve this.     

Influence of reaction conditions on the enantioselectivity of biocatalyzed C-C bond formations under high pressure conditions

Benzoylformate decarboxylase (BFD, EC 4.1.1.7) is a homotetrameric thiamine diphosphate (ThDP)-dependent enzyme which catalyzes the synthesis of chiral 2-hydroxyketones accepting a broad range of aldehydes as substrates. In this study the synthesis of 2-hydroxypropiophenone (2-HPP) from benzaldehyde and acetaldehyde was catalyzed by three BFD variants namely BFD F464I, BFD A460I and BFD A460I-F464I. This paper reports the effect of hydrostatic pressure up to 290 MPa when the reactions were carried out at different benzaldehyde concentrations (5-40 mM) as well as at different pH values (7.0-8.5). Acetaldehyde concentration was fixed at 400 mM in all biotransformations. Reactions performed at high benzaldehyde concentrations and at high hydrostatic pressures showed an increase in (R)-2-HPP formation catalyzed by all BFD variants. For BFD A460I-F464I we observed an increase in the ee of (R)-2-HPP up to 80%, whereas at atmospheric conditions this variant synthesizes (R)-2-HPP with an ee of only 50%. Alkaline conditions (up to pH 8.5) and high hydrostatic pressures resulted in an increase of (R)-2-HPP synthesis, especially in the case of BFD A460I and BFD F464I.     

Effects of developmental conditions on glucocorticoid concentrations in adulthood depend on sex and foraging conditions

Developmental conditions in early life frequently have long-term consequences on the adult phenotype, but the adult environment can modulate such long-term effects. Glucocorticoid hormones may be instrumental in mediating developmental effects, but the permanency of such endocrine changes is still debated. Here, we manipulated environmental conditions during development (small vs. large brood size, and hence sibling competition) and in adulthood (easy vs. hard foraging conditions) in a full factorial design in zebra finches, and studied effects on baseline (Bas-CORT) and stress-induced (SI-CORT) corticosterone in adulthood. Treatments affected Bas-CORT in females, but not in males. Females reared in small broods had intermediate Bas-CORT levels as adults, regardless of foraging conditions in adulthood, while females reared in large broods showed higher Bas-CORT levels in hard foraging conditions and lower levels in easy foraging conditions. Female Bas-CORT was also more susceptible than male Bas-CORT to non-biological variables, such as ambient temperature. In line with these results, repeatability of Bas-CORT was higher in males (up to 51%) than in females (25%). SI-CORT was not responsive to the experimental manipulations in either sex and its repeatability was high in both sexes. We conclude that Bas-CORT responsiveness to intrinsic and extrinsic conditions is higher in females than in males, and that the expression of developmental conditions may depend on the adult environment. The latter finding illustrates the critical importance of studying of causes and consequences of long-term developmental effects in other environments in addition to standard laboratory conditions.     

Preparation of sulfated-chitins under homogeneous conditions

Sulfated-chitins of varying degrees of sulfation were prepared by the reaction of chitin with sulfur trioxide–pyridine complex under homogeneous conditions in 5% LiCl/DMAc solvent system. Sulfation at 8 °C or room temperature was regio-selective for the C6–OH position with the degree of sulfation (D.S.) ranging from 0.53 to 1.00 depending on the reaction time. When the reaction temperature was elevated, sulfation at the C3–OH position also occurred. The extent of sulfation at the C3 position was a function of the concentration of sulfating reagent, reaction time and temperature. The structure of sulfated-chitins was established by ¹H, ¹³C NMR and 2D HMQC. The degree of sulfation at the C6 position was estimated by ¹H NMR while that of the C3 position was by elemental analyses. The anticoagulant activity of the prepared sulfated-chitins correlated closely with D.S. The higher the D.S. yielded, the better the anticoagulant activity. In particular, a continuous sequence of 36S units was critical for obtaining high anticoagulation activity.