Transesterification of vegetable oils on basic large mesoporous alumina supported alkaline fluorides-Evidences of the nature of the active site and catalytic performances

KF, LiF and CsF/A(2)O(3) catalysts with different loadings from 1 to 20 wt% were prepared using aqueous solutions of the alkaline fluoride compounds by wet impregnation of basic mesoporous MSU-type alumina. The catalysts were activated under At at 400 degrees C for 2 h and monitored by in situ XRD measurements. The catalysts were also characterized using several techniques: N-2 adsorption/desorption isotherms at -196 degrees C, FTIR, DR-UV-vis, CO2-TPD, XRD, Al-27 CP/MAS NMR. These characterizations led to the conclusion that the deposition of alkaline fluorides on the alumina surface generates fluoroaluminates and aluminate species. The process is definitivated at 400 degrees C. The fluorine in these structures is less basic than in the parent fluorides, but the oxygen becomes more basic. The catalysts were tested for the transesterification of fatty esters under different experimental conditions using conventional heating, microwave and Ultrasound irradiation. Recycling experiments showed that these catalysts are stable for a limited number of cycles. (C) 2009 Elsevier Inc. All rights reserved.

Patterns of variation at a mitochondrial sequence-tagged-site locus provides new insights into the postglacial history of European Pinus sylvestris populations

Due to their maternal mode of inheritance, mitochondrial markers can be regarded as almost 'ideal' tools in evolutionary studies of conifer populations. In the present study, polymorphism was analysed at one mitochondrial intron (nad 1, exon B/C) in 23 native European Pinus sylvestris populations. In a preliminary screening for variation using a polymerase chain reaction-restriction fragment length polymorphism approach, two length variants were identified. By fully sequencing the 2.5 kb region, the observed length polymorphism was found to result from the insertion of a 31 bp sequence, with no other mutations observed within the intron. A set of primers was designed flanking the observed mutation, which identified a novel sequence-tagged-site mitochondrial marker for P. sylvestris. Analysis of 747 trees from the 23 populations using these primers revealed the occurrence of two distinct haplotypes in Europe. Within the Iberian Peninsula, the two haplotypes exhibited extensive population differentiation (Phi(ST) = 0.59; P less than or equal to 0.001) and a marked geographical structuring. In the populations of central and northern Europe, one haplotype largely predominated, with the second being found in only one individual of one population.

Sleeping site selection by the golden-handed tamarin Saguinus midas midas: The role of predation risk, proximity to feeding sites, and territorial defence

Tamarin monkeys, of the genus Saguinus, spend over half their lives at arboreal sleeping sites. The decision as to which site to use is likely to have considerable fitness consequences. These decisions about sleeping sites by three troops of golden-handed tamarin Saguinus midas midas were examined over a 9-mo period at a rainforest site in French Guiana. Data are presented on the physical nature of sleeping sites, their number, position within home ranges, and pattern of use and reuse, aspects of behaviour at retirement and egress, and predation attempts on the study troops. Cumulative plot analysis indicated that a tamarin troop used 30-40 sleeping sites in a 100-day period, approximately half of which were used very infrequently, so that consecutive reuse was never greater than three nights. Sleeping trees were superior in architectural parameters and liana weight to non-sleeping trees. There were no more sleeping sites than expected within the home range boundary region of the tamarins or in areas of overlap with the home ranges of neighbouring troops. Tamarins selected sleeping sites nearest to the last feeding site of the day on 25% of occasions. The study troops engaged in a number of activities that may reduce predation risk; raptor attacks on the study troops over 9 mo were frequent but unsuccessful. Tamarins often visited a sleeping site several hours before arrival, and were more likely to visit a site before use if they had not used it recently. The decision to select a sleeping site therefore involved knowledge of the previous frequency of use of that site.

Evidence That Interspecies Polymorphism in the Human and Rat Cholecystokinin Receptor-2 Affects Structure of the Binding Site for the Endogenous Agonist Cholecystokinin

The cholecystokinin (CCK) receptor-2 exerts very important central and peripheral functions by binding the neuropeptides cholecystokinin or gastrin. Because this receptor is a potential therapeutic target, great interest has been devoted to the identification of efficient antagonists. However, interspecies genetic polymorphism that does not alter cholecystokinin-induced signaling was shown to markedly affect activity of synthetic ligands. In this context, precise structural study of the agonist binding site on the human cholecystokinin receptor-2 is a prerequisite to elucidating the molecular basis for its activation and to optimizing properties of synthetic ligands. In this study, using site-directed mutagenesis and molecular modeling, we delineated the binding site for CCK on the human cholecystokinin receptor-2 by mutating amino acids corresponding to that of the rat homolog. By doing so, we demonstrated that, although resembling that of rat homolog, the human cholecystokinin receptor-2 binding site also displays important distinct structural features that were demonstrated by susceptibility to several point mutations (F120A, Y189A, H207A). Furthermore, docking of CCK in the human and rat cholecystokinin receptor-2, followed by dynamic simulations, allowed us to propose a plausible structural explanation of the experimentally observed difference between rat and human cholecystokinin-2 receptors.