Effect of dietary fatty acids on expression of lipogenic enzymes and fatty acid profile in tissues of bulls

This study investigated the effects of dietary linolenic acid (C18:3n-3) v. linoleic acid (C18:2n-6) on fatty acid composition and protein expression of key lipogenic enzymes, acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase (SCD) and delta 6 desaturase (6d) in longissimus muscle and subcutaneous adipose tissue of bulls. Supplementation of the diet with C18:3n-3 was accompanied by an increased level of n-3 fatty acids in muscle which resulted in decrease of n-6/n-3 ratio. The diet enriched with n-3 polyunsaturated fatty acids (PUFAs) significantly inhibited SCD protein expression in muscle and subcutaneous adipose tissue, and reduced the 6d expression in muscle. There was no significant effect of the diet on ACC protein expression. Inhibition of the 6d expression was associated with a decrease in n-6 PUFA level in muscles, whereas repression of SCD protein was related to a lower oleic acid (C18:1 cis-9) content in the adipose tissue. Expression of ACC, SCD and 6d proteins was found to be relatively higher in subcutaneous adipose tissue when compared with longissimus muscle. It is suggested that dietary manipulation of fatty acid composition in ruminants is mediated, at least partially, through the regulation of lipogenic enzymes expression and that regulation of the bovine lipogenic enzymes expression is tissue specific. © 2010 The Animal Consortium

Self-Assembly of n-Alkanethiols: A Kinetic Study by Second Harmonic Generation

Thiolate formation of n-alkanethiols (CH3(CH2)m-1SH) adsorbing on polycrystalline gold was studied in situ and in real time under a variety of experimental conditions. The chain length of the thiols studied varied from m = 4 to m = 22. The influence of the thiol concentration in different solvents (ethanol, hexane, dodecane, and hexadecane) was examined in the range between 0.5 and 20.0 μmol/L. Among the models proposed in the literature, only Langmuir kinetics can explain the data, irrespective of the experimental conditions. As will be shown, all other kinetic models fail to describe the measured formation kinetics of thiolate films on a polycrystalline gold surface. However, small but significant differences between the experimental data and the Langmuir model assuming statistical adsorption are identified. A modified Kisliuk model accounting for different adsorption sites yields the best agreement with the experimental data. On the basis of these results we propose a kinetic model of thiolate formation which identifies the displacement of solvent molecules adsorbed on the substrate and/or incorporation of alkanethiols into thiolate islands as the rate-limiting steps

Self-assembled monolayers from organosulfur compounds: A comparison between sulfides, disulfides and thiols

Film formation of decanethiol [CH3(CH2)9SH], didecyl disulfide [CH3(CH2)9S−S(CH2)9CH3], and didecyl sulfide [CH3(CH2)9−S−(CH2)9CH3] on polycrystalline gold from ethanol solutions was studied in situ by second harmonic generation. The completed films were characterized by X-ray photoelectron spectroscopy and voltammetry. Film formation is described by Langmuir adsorption kinetics and is found to be fastest for the thiol. Referenced to the number of thiolate units the disulfide adsorbs about 40% more slowly. In sharp contrast, the rate of alkyl sulfide adsorption is smaller by more than 3 orders of magnitude. Films formed from the thiol and disulfide are indistinguishable and virtually free of contaminations. In contrast, the maximum coverage achieved with the sulfide is considerably lower and substantial amounts of contamination remain on the substrate. Differences between thiol/disulfide films and sulfide films are also indicated by their electrochemical behavior

Ultrahigh vacuum study on the reactivity of organic surfaces terminated by -OH and –COOH groups prepared by self-assembly of functionalized alkanethiols on Au substrates

Two different organic surfaces were created by self-assembly (SA) of bifunctionalized monomers using OH- and COOH-terminated alkanethiols. X-ray photoelectron (XP) and soft X-ray absorption (NEXAFS) spectroscopy have been used to determine the chemical composition of and the molecular orientation in the SA monolayers adsorbed on Au substrates. Subsequently the two OH- and COOH-terminated organic surfaces were exposed to phenyl isocyanate (C6H5NCO, PIC) in order to investigate their chemical reactivity. In both cases the reactivity to gas-phase PIC was very low for the sample at room temperature. Reaction yields of more than 80% could, however, be achieved by depositing multilayers on a sample cooled down to 120 K which was subsequently warmed to 290 K