Gauging of Cytochrome c Structural Fluctuation by Time-Resolved Proton Pulse

A brief proton pulse technique, based on photo-excitation of pyranine, was employed for measuring the protonation dynamics of cytochrome c in aqueous solutions. Time-resolved monitoring of the protonation state of the pyranine anion yielded detailed information from which the temporal state protonation of the surface carboxylates and histidine residues were deduced. The surface groups were found to be coupled by electrostatic interaction where the state of protonation of one affects the pK of the others. In the same sense, altering the charge distribution of a protein by a redox reaction affects the reactivity of the surface groups with protons in the bulk. The surface groups can exchange protons among themselves at a very high rate. The velocities of these reactions are functions of the connectivity between the proton binding sites. A single proton exchange reaction between the surface groups could be identified as the proton exchange between H26 and E44. The reaction is fast and affected by the redox state of the protein. It is proposed that the enhanced rate of this reaction is coupled with transient conformational changes that are not noticeable in time-averaging measurements such as X-ray diffraction or NMR.     

Rosuvastatin Enhances the Catabolism of LDL apoB‐100 in Subjects with Combined Hyperlipidemia in a Dose Dependent Manner

Dose‐associated effects of rosuvastatin on the metabolism of apolipoprotein (apo) B‐100 in triacylglycerol rich lipoprotein (TRL, d < 1.019 g/ml) and low density lipoprotein (LDL) and of apoA‐I in high density lipoprotein (HDL) were assessed in subjects with combined hyperlipidemia. Our primary hypothesis was that maximal dose rosuvastatin would decrease the apoB‐100 production rate (PR), as well as increase apoB‐100 fractional catabolic rate (FCR). Eight subjects received placebo, rosuvastatin 5 mg/day, and rosuvastatin 40 mg/day for 8 weeks each in sequential order. The kinetics of apoB‐100 in TRL and LDL and apoA‐I in HDL were determined at the end of each phase using stable isotope methodology, gas chromatography‐mass spectrometry, and multicompartmental modeling. Rosuvastatin at 5 and 40 mg/day decreased LDL cholesterol by 44 and 54 % (both P < 0.0001), triacylglycerol by 14 % (ns) and 35 % (P < 0.01), apoB by 30 and 36 % (both P < 0.0001), respectively, and had no significant effects on HDL cholesterol or apoA‐I levels. Significant decreases in plasma markers of cholesterol synthesis and increases in cholesterol absorption markers were observed. Rosuvastatin 5 and 40 mg/day increased TRL apoB‐100 FCR by 36 and 46 % (both ns) and LDL apoB‐100 by 63 and 102 % (both P < 0.05), respectively. HDL apoA‐I PR increased with low dose rosuvastatin (12 %, P < 0.05) but not with maximal dose rosuvastatin. Neither rosuvastatin dose altered apoB‐100 PR or HDL apoA‐I FCR. Our data indicate that maximal dose rosuvastatin treatment in subjects with combined hyperlipidemia resulted in significant increases in the catabolism of LDL apoB‐100, with no significant effects on apoB‐100 production or HDL apoA‐I kinetics.     

Concentrations and determinants of organochlorine levels among pregnant women in Eastern Spain

Persistent organic pollutants (POPs) comprise a large variety of toxic substances with ample distribution. While exposure to these toxins occurs mainly through diet, maternal POP levels may be influenced by certain sociodemographic, environmental, or lifestyle factors. This is important given that these substances may have adverse effects on fetal development. The aim of this study is to examine the sociodemographic, environmental, lifestyle, and dietary determinants of the levels of hexachlorobenzene (HCB), b-hexachlorocyclohexane (b-HCH), 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (4,4′-DDT), 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (4,4′-DDE), and polychlorinated biphenyls (PCB congeners 118, 138, 153, 180) measured in the blood of pregnant women participating in a mother-child cohort study conducted in Valencia (Spain).The study population consisted of 541 pregnant women who formed part of the INMA (Childhood and the Environment) cohort (2004-2006). POP levels were determined in blood taken during the 12th week of pregnancy with the aid of gas chromatography with electron capture detection. Sociodemographic, environmental, and dietary information was obtained from a questionnaire. Multivariate Tobit regression models were constructed in order to assess the association between POP levels and selected covariates.The results showed that all the women had detectable levels of at least one of these compounds while in 43% of the subjects, all eight compounds were detected. The compounds found in the greatest number of women were 4,4′-DDE (100%) and PCBs 153 and 180 (95%). The most important determinants of high POP levels were the mother's age, country of origin, increased body mass index, and number of weeks of breastfeeding after previous pregnancies. With regard to diet, 4,4′-DDT and 4,4′-DDE levels increased with the intake of meat, fruit, and cereal. PCB 153 levels increased with the intake of seafood. The levels of HCB, b-HCH, 4,4′-DDT, and 4,4′-DDE observed in this study were slightly higher than in other studies, whereas the PCB levels were similar.     

HRM in project groups: The effect of project duration on team development effectiveness

The literature has found contradictory results regarding the impact of human resource management on project success. This paper focuses on one important human resource management process – team development – to investigate its importance in the project environment. Results show that most team development practices that work well in the operational business environment do not have a significant influence on project success. However, project duration was found to moderate the relationship between team development and project success: the effectiveness of team development increases in longer projects. The paper identifies and analyzes team development practices that have a positive impact on project success exclusively in long projects.     

Self-assembly of iron oxide-poly(ethylene glycol) core-shell nanoparticles at liquid-liquid interfaces

Nanoparticles (NPs) play an increasingly important role in the fabrication of functional advanced materials. Two major steps need to be carried out in order to achieve control of the material properties. First of all, the properties of the single NPs have to be under control, especially in relation to colloidal stability; aggregation and corrosion negate all the benefits associated to the nanoscopic dimensions. Secondly, the assembly process has to be controlled to achieve a material with the desired properties. We propose here to use stabilized ceramic NPs consisting of a magnetite core, coated by a poly(ethylene glycol) (PEG) shell and study their assembly at polar/ non-polar liquid interfaces, en route to fabricating functional NP membranes. These NPs show extraordinary stability in aqueous solutions achieved by anchoring linear PEG chains through an end-terminating nitroDOPA group to their surface. Furthermore, the core and shell sizes of these NPs can be independently varied with ease. We first describe the details of the NP synthesis and stabilization in bulk solutions, discussing the PEG molecular weight needed to achieve bulk stability. Subsequently, we demonstrate self-assembly of these particles at liquid-liquid interfaces (SALI) into monolayers of stable properties. SALI has been chosen as path for the assembly given its suitability for fabricating two-dimensional materials. We report here results from pendant drop tensiometry which illustrate the kinetics of NP adsorption at the liquid-liquid interface and highlight the role played by the molecular weight of the PEG shell in the interfacial assembly. In particular we show that the requisites to ensure particle stability at a liquid interface are more stringent compared to the bulk case.     

Cationic peptides that increase the thermal stabilities of 2'-O-MeRNA/RNA duplexes but do not affect DNA/DNA melting

Several different cationic nonapeptides have been synthesized and investigated with respect to how they can influence the thermal melting of 2′‐O‐methylRNA/RNA and DNA/DNA duplexes. Each peptide has a C‐terminal L ‐phenylalanine unit and is otherwise uniformly composed of a sequence of a specific basic D ‐amino acid that in most cases will be largely charged at neutral pH. These N‐terminal octamer stretches are composed variously of the amino acids D ‐lysine, D ‐diaminobutyric acid (D ‐Dab), D ‐diaminopropionic acid (D ‐Dap), or D ‐histidine. None of the peptides substantially affected the thermal melting of DNA/DNA duplexes, which was in sharp contrast with their effects on 2′‐O‐methylRNA/RNA duplexes. In particular, the peptides based on diaminopropionic and diaminobutyric acid units had strong positive effects on the melting temperatures of the 2′‐O‐methylRNA duplexes (up to 16 °C higher with 1 equivalent of peptide) at pH 7, whereas at pH 6 the effect was even more drastic (ΔT_m up to +25 °C). The shorter R groups of the Dap and Dab groups appear to have a better length than lysine for enhancement of the thermal melting of the 2′‐O‐methylRNA/RNA duplex, an effect that is more pronounced at lower pH but substantial even at pH 7, although the Dap derivative is not likely to be fully protonated. The dramatic difference between the influence, or lack thereof, on the 2′‐O‐methylRNA/RNA and the DNA/DNA thermal meltings suggest that, although electrostatic interactions probably play a role, there is another major and structurally dependent component influencing the properties of the duplexes. This is also seen in the observation that the oligo‐Dap and oligo‐Dab peptides give greater melting point enhancements than both the lysine peptide (with a longer side chain) and a β‐linked Dap peptide with a shorter side chain and a longer backbone.     

Inhibition Studies of Mycobacterium tuberculosis Salicylate Synthase (MbtI)

Mycobacterium tuberculosis salicylate synthase (MbtI), a member of the chorismate‐utilizing enzyme family, catalyses the first committed step in the biosynthesis of the siderophore mycobactin T. This complex secondary metabolite is essential for both virulence and survival of M. tuberculosis, the etiological agent of tuberculosis (TB). It is therefore anticipated that inhibitors of this enzyme may serve as TB therapies with a novel mode of action. Herein we describe the first inhibition study of M. tuberculosis MbtI using a library of functionalized benzoate‐based inhibitors designed to mimic the substrate (chorismate) and intermediate (isochorismate) of the MbtI‐catalyzed reaction. The most potent inhibitors prepared were those designed to mimic the enzyme intermediate, isochorismate. These compounds, based on a 2,3‐dihydroxybenzoate scaffold, proved to be low‐micromolar inhibitors of MbtI. The most potent inhibitors in this series possessed hydrophobic enol ether side chains at C3 in place of the enol‐pyruvyl side chain found in chorismate and isochorismate.     

Estimation of soil water repellency of different particle size fractions in relation with carbon content by different methods

The water repellency of soils with different texture under different types of plant cover was determined by applying the WDPT and MED methods to both whole samples and the following size fractions: 2-1, 1-0.5, 0.5-0.25, 0.25-0.05 and <0.05 mm. Based on the results, the soils under maize crop and grassland, which were mostly wettable in the whole samples, exhibited water repellency in the finest fraction (<0.05 mm) as a result of its higher organic carbon content. On the other hand, all fractions in the forest soils, which were extremely water repellent, contributed to the overall repellency; in any case, the MED test revealed that the finest fraction was strongly repellent in the forest soils as well.     

A biofilm model for flowing systems in the food industry

When bacteria attach to the walls of pipelines, they can form biofilms, which can cause the recontamination of food products. In order to quantify such recontamination, a one-dimensional biofilm model was developed taking into account adsorption, desorption, and the growth of cells. The model consisted of two mass balances describing increases in biofilm formation at the wall and the accumulation of cells in the liquid phase. The necessary parameters for the model were obtained in laboratory biofilm experiments. These experiments involved a flowing system and the use of Staphylococcus aureus as a model pathogen and silicon tubing as a testing material. S. aureus was inoculated into the system for 2 h, and then the system was changed to a sterile medium. Both biofilm formation and the release of cells into the flowing liquid were measured until steady-state conditions were reached (for up to 9 days). The experiments were performed in duplicate for different flow conditions (i.e., for Reynolds numbers of 3.2, 32, and 170). It was shown that at higher Reynolds numbers, the biofilm developed faster, probably owing to an increase in the transfer of nutrients to the surface. The proposed biofilm model was capable of describing the data obtained for the three different flow conditions with the use of the specific growth rate in the biofilm and the desorption coefficient as fit parameters. The specific growth rates were 0.16, 0.27, and 0.49 h(-1) for Reynolds numbers of 3.2, 32, and 170, respectively, and the desorption coefficients were about 1% of these values.