An assessment of DFT methods for predicting the thermochemistry of ion-molecule reactions of group 14 elements (Si, Ge, Sn)

Experimental mass-spectrometry data on thermochemistry of methide transfer reactions (CH₃)₃M⁺ + M'(CH₃)₄ ? M(CH₃)₄?+?(CH₃)₃M'⁺ (M, M'?=?Si, Ge or Sn) and the formation energy of the [(CH₃)₃Si-CH₃-Si(CH₃)₃]⁺ complex are used as benchmarks for DFT methods (B3LYP, BMK, M06L, and ωB97XD). G2 and G3 theory methods are also used for the prediction of thermochemical data. BMK, M06L, and ωB97XD methods give the best fit to experimental data (close to chemical accuracy) as well as to G2 and G3 results, while B3LYP demonstrates poor performance. From the first three methods M06L gives the best overall result. Structures and formation energies of intermediate “mixed” [(CH₃)₃M-CH₃- M′(CH₃)₃] complexes not observed in experiment are predicted. Their structures, better described as M(CH₃)₄?[M′(CH₃)₃]⁺ complexes, explain their fast decompositions.

Synthesis and Evaluation of Biphenyl Compounds as Kinesin Spindle Protein Inhibitors

Kinesin spindle protein (KSP), an ATP‐dependent motor protein, plays an essential role in bipolar spindle formation during the mitotic phase (M phase) of the normal cell cycle. KSP has emerged as a novel target for antimitotic anticancer drug development. In this work, we synthesized a range of new biphenyl compounds and investigated their properties in vitro as potential antimitotic agents targeting KSP expression. Antiproliferation (MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide)) assays, combined with fluorescence‐assisted cell sorting (FACS) and Western blot studies analyzing cell‐cycle arrest confirmed the mechanism and potency of these biphenyl compounds in a range of human cancer cell lines. Structural variants revealed that functionalization of biphenyl compounds with bulky aliphatic or aromatic groups led to a loss of activity. However, replacement of the urea group with a thiourea led to an increase in antiproliferative activity in selected cell lines. Further studies using confocal fluorescence microscopy confirmed that the most potent biphenyl derivative identified thus far, compound 7 , exerts its pharmacologic effect specifically in the M phase and induces monoaster formation. These studies confirm that chemical scope remains for improving the potency and treatment efficacy of antimitotic KSP inhibition in this class of biphenyl compounds.     

Evaluation of the performance and accuracy of Global Positioning System bug transmitters deployed on a small mammal

Recent technological advances in Global Positioning System (GPS) telemetry have allowed the production of lightweight devices suitable for use on small mammals. We evaluated the use of GPS bugs on the European hedgehog (Erinaceus europaeus) in a series of static and field tests. Static tests were conducted in five different rural habitats, affording different degrees of obstruction to satellites. GPS bug performance was good in all habitats (fix success rate (FSR): median ≥?66.8 %; location error (LE): mean ≤?13.5 m), except woodland (FSR?=?37.7 %; LE?=?15.6 m), with performance highest in the open pasture habitat (FSR?=?100 %; LE?=?6.4 m). Field tests revealed mean FSR was high (84.6 %), with the use of nesting habitats, the probable cause of most failed fixes. Despite being more expensive, GPS bugs require less survey effort and substantially lower labour costs with unlimited longevity permitting re-use in multiple seasons. We recommend the use of GPS bugs in the spatial ecological study of any small mammal in a rural environment, providing accurate and unbiased movement data. Further performance testing is recommended before deployment on species inhabiting forested habitats where reduced FSR and high LE support the alternative use of very high frequency tracking.     

A new theoretical analysis of the cooperative effect in T-shaped hydrogen complexes of CnHm∙∙∙HCN∙∙∙HW with n = 2, m = 2 or 4, and W = F or CN

In this theoretical work, a new idea about cooperativity in intermolecular clusters of C_nH_m???HCN???HW stabilized by hydrogen bonds composed by lone-electron pairs (nitrogen) and π clouds (C?=?C and C?≡?C) as proton acceptors is developed. The structural study and vibrational analysis have pointed out deformations in the intermolecular clusters caused by the HW terminal proton-donor, in which if W?=?fluorine the largest perturbation occurs. On the contrary, the HCN molecule is considered an intermolecular mediator because its structure is practically unaltered upon the formation of the trimolecular complexes. In order to understand the real contribution of the proton-donor either mediator (HCN) or terminal (HW with W?=?CN or F), a chemometric analysis was performed uniquely to discover which interaction plays a key role in the collapse of the cooperative effect. The formation of strongest interactions leads to more drastic variations in the energy distribution. In this way, the application of the quantum theory of atoms in molecules (QTAIM) has been extremely important because the hydrogen bond strengths followed by indiciums of covalence were predicted, and therefore the cooperative effect could be understood at last.     

Electrochemical surface modification of carbon mesh anode to improve the performance of air-cathode microbial fuel cells

A convenient and promising alternative to surface modification of carbon mesh anode was fulfilled by electrochemical oxidation in the electrolyte of nitric acid or ammonium nitrate at ambient temperature. It was confirmed that such an anode modification method was low cost and effective not only in improving the efficiency of power generation in microbial fuel cells (MFCs) for synthetic wastewater treatment, but also helping to reduce the period for MFCs start-up. The MFCs with anode modification in electrolyte of nitric acid performed the best, achieving a Coulombic efficiency enhancement of 71 %. As characterized, the electrochemical modification resulted in the decrease of the anode potential and internal resistance but the increase of current response and nitrogen-containing and oxygen-containing functional groups on the carbon surface, which might contribute to the enhancement on the performances of MFCs.     

Selection of antimalarial drug resistance after intermittent preventive treatment of infants and children (IPTi/c) in Senegal

Senegal has since 2003 used sulphadoxine-pyrimethamine (SP) for Intermittent Preventive Treatment (IPT) of malaria in risk groups. However, the large-scale IPT strategy may result in increasing drug resistance. Our study investigated the possible impact of SP-IPT given to infants and children on the prevalence of SP-resistant haplotypes in the Plasmodium falciparum genes Pfdhfr and Pfdhps, comparing sites with and without IPTi/c. P. falciparum positives samples (n = 352) were collected from children under 5 years of age during two cross-sectional surveys in 2010 and 2011 in three health districts (two on IPTi/c and one without IPTi/c intervention) located in the southern part of Senegal. The prevalence of SP-resistance-related haplotypes in Pfdhfr and Pfdhps was determined by nested PCR followed by sequence-specific oligonucleotide probe (SSOP)–ELISA. The prevalence of the Pfdhfr double mutant haplotypes (CNRN and CICN) was stable between years at < 10% in the control group (P = 0.69), while it rose significantly in the IPTi/c group from 2% in 2010 to 20% in 2011 (P = 0.008). The prevalence of the Pfdhfr triple mutant haplotype (CIRN) increased in both groups, but only significantly in the IPTi/c group from 41% to 65% in 2011 (P = 0.005). Conversely, the Pfdhps 437G mutation decreased in both groups from 44.6% to 28.6% (P = 0.07) and from 66.7% to 47.5% (P = 0.02) between 2010 and 2011 in the control and the IPTi/c groups, respectively. Combined with Pfdhfr, there was a weak trend for decreasing prevalence of quadruple mutants (triple Pfdhfr + Pfdhps 437G) in both groups (P = 0.15 and P = 0.34). During the two cross-sectional surveys, some significant changes were observed in the SP-resistance-related genes. However, since these changes were observed in the two groups, the IPTi/c strategy does only seem to have limited impact on resistance development and other factors as well. However, continuous monitoring will be needed, due to the up-scaling of the IPTi/c strategy in Senegal according to WHO recommendations.     

Identification of the phosphoglycerate dehydrogenase isoform EDA9 as the essential gene for embryo and male gametophyte development in Arabidopsis

Three different pathways of serine (Ser) biosynthesis have been described in plants: the Glycolate pathway, which is part of the Photorespiratory pathway, and 2 non-Photorespiratory pathways, the Glycerate and the Phosphorylated pathways. The Phosphorylated Pathway of Ser Biosynthesis (PPSB) has been known to exist since the 1950s, but its biological relevance was not revealed until quite recently when the last enzyme of the pathway, the Phosphoserine Phosphatase, was functionally characterized. In the associated study¹, we characterized a family of genes coding for putatite phosphoglycerate dehydrogenases (PGDH, 3-PGDH, and EDA9), the first enzyme of the PPSB. A metabolomics study using overexpressing plants indicated that all PGDH family genes were able to regulate Ser homeostasis but only lacking of EDA9 expression caused drastic developmental defects. We provided genetic and molecular evidence for the essential role of EDA9 for embryo and pollen development. Here, some new insights into the physiological/molecular function of PPSB and Ser are presented and discussed.     

Semen CD4+ T Cells and Macrophages Are Productively Infected at All Stages of SIV infection in Macaques

The mucosal events of HIV transmission have been extensively studied, but the role of infected cells present in the genital and rectal secretions, and in the semen, in particular, remains a matter of debate. As a prerequisite to a thorough in vivo investigation of the early transmission events through infected cells, we characterized in detail by multi-parameter flow cytometry the changes in macaque seminal leukocytes during SIVmac251 infection, focusing on T cells, macrophages and dendritic cells. Using immunocytofluorescence targeting SIV proteins and real-time quantitative PCR targeting SIV DNA, we investigated the nature of the infected cells on sorted semen leukocytes from macaques at different stages of infection. Finally, we cocultured semen CD4⁺ T cells and macrophages with a cell line permissive to SIV infection to assess their infectivity in vitro. We found that primary infection induced strong local inflammation, which was associated with an increase in the number of leukocytes in semen, both factors having the potential to favor cell-associated virus transmission. Semen CD4⁺ T cells and macrophages were productively infected at all stages of infection and were infectious in vitro. Lymphocytes had a mucosal phenotype and expressed activation (CD69 & HLA-DR) and migration (CCR5, CXCR4, LFA-1) markers. CD69 expression was increased in semen T cells by SIV infection, at all stages of infection. Macrophages predominated at all stages and expressed CD4, CCR5, MAC-1 and LFA-1. Altogether, we demonstrated that semen contains the two major SIV-target cells (CD4+ T cells and macrophages). Both cell types can be productively infected at all stages of SIV infection and are endowed with markers that may facilitate transmission of infection during sexual exposure.