Effect of biotin supplementation on meat quality of F1 Wagyu/Black Angus feedlot steers of known genotype

Biotin (D-biotin) was supplemented to F1 Wagyu/Black Angus steers fed a wheat-based ration to evaluate the effect on meat quality. One hundred and eight steers of known Wagyu sire lines were assigned to three biotin treatments (0, 10 and 20mg/head/day) with each treatment replicated four times using an unfasted liveweight of 410.5kg (±24.42 SD). Biotin supplementation had no effect (P>0.05) on beef marbling standard at either the 5/6th or 10/11th rib quartering site, 10/11th rib intra-muscular fat percentage, intra-muscular fat fatty acid composition or adipose melting points. Wagyu genotype had an effect (P<0.05) on beef marbling standard and intra-muscular fat percentage at the 10/11th rib, inter-muscular and intra-muscular melting point and fatty acid composition of intra-muscular fat. A significant (P<0.001) but poor correlation existed between beef marbling standard and intra-muscular fat percentage (R(2)=0.198). Total conjugated linoleic acid had a highly significantly (P<0.0001) positive correlation to intra-muscular fat percentage (R(2)=0.446).     

三种维生素对小球藻的增殖效应研究

文章报道了维生素B1、维生素B12和维生素H对小球藻增殖的影响情况。试验采用一次性培养方式,在温度25℃±1℃,盐度29,光照5000lx条件下进行。用血球记数板法定时测定小球藻的细胞数量并计算出其生长速率。试验表明,维生素B1对小球藻的增殖有极显著的促进作用,另外2种维生素对小球藻的增殖无明显影响。3种维生素之间没有交互作用。维生素B1最适宜小球藻增殖的浓度范围是40μgL～80μgL。     

A new method of immobilization of proteins on activated ester terminated alkanethiol monolayers towards the label free impedancemetric detection

This paper investigates a new immobilization procedure for biological molecules that is based on the formation of reactive ω-functionalized-self-assembled thiol monolayers onto a gold electrode. The homogeneous self-assembled monolayer was characterized by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The SAM modified gold electrode showed a clear peak corresponding to S_2p that characterized the Au-thiolate bond, while cyclic voltammetry and electrochemical impedance spectroscopy measurements, in 10 mM phosphate buffer pH 7, in the presence of Fe(CN)₆^{− 3/− 4} as redox probe, showed that these monolayers were densely packed and prevented electron transfer towards the gold surface. These homogeneous SAMs were used to immobilize biotin hydrazide by covalent attachment, after the nucleophilic attack of the amino group of biotin hydrazide on the ω-activated ester function of thiols. The biotin–avidin interaction was then examined as a model for an affinity biosensor with electrochemical impedance spectroscopy. A Randles equivalent circuit was used for the interpretation of impedance data and the change in the interfacial properties at the modified-electrode/electrolyte interface were monitored through charge-transfer resistance variation. The proposed affinity biosensor showed a detection range that was linear between 200 and 800 ng/ml for avidin. In order to improve the sensitivity the technique of mixed self-assembled monolayers was adopted. Mixed SAMs were elaborated by co-adsorption of two differently substituted thiols, one was substituted by a reactive group that was used to react with the amino group of biotin hydrazide, whereas the other was substituted by an hydroxyl group that was chosen to mimic protein resistance. In this study, we started with a 1:3 activated ester:hydroxyl-terminated alkanethiol ratio. The results obtained with the mixed SAMs appeared to be better than those obtained with the homogeneous SAMs, and the corresponding affinity biosensor presented two detection ranges that were linear between 20 and 100 ng/ml and between 100 and 1200 ng/ml, respectively, with two different slopes.     

Availability of biotin incorporated in electrospun PLA fibers for streptavidin binding

Distribution of biotin at a depth of 3-10 nm from the surface of electrospun polylactic acid (PLA) fibers has been assessed by X-ray photoelectron spectroscopy (XPS) and compared to the distribution predicted by bulk calculations. Biotin concentration in the outer 3-10 nm of the fibers is greater than the predicted if biotin was distributed uniformly within the fiber. Availability of biotin for streptavidin binding at the surface of the fibers has been determined via a competitive colorimetric assay. Availability of biotin at the fiber surface was also determined to be greater than predicted by calculations assuming uniform biotin distribution. Additionally, the segregation of biotin to the exterior of the fiber increases disproportionately with increasing overall biotin concentration in the fibers. Confocal microscopy has been used to confirm capture of streptavidin, primary antibodies and fluorescence labeled secondary antibodies on PLA/biotin fibers.     

Toxicity of dietary avidin and streptavidin to the cowpea bruchid, Callosobruchus maculatus (F.)

Avidin, a large protein from egg whites, powerfully binds biotin, a vitamin for many insects. When avidin was incorporated into the diets of larval Callosobruchus maculatus (F.), the cowpea bruchid, at relatively low levels (10–30 ppm), there was a marked dose-dependent increase in mortality, as well as a small increase in the developmental time of survivors. Avidin toxicity was prevented when biotin was added to the diet together with avidin. Sub-lethal doses of avidin caused reductions in fecundity. Avidin had no effect on the larval feeding rates during the first three instars, even when the larvae were consuming amounts of the protein that would later cause death. In the fourth instar there was a dose-dependent reduction in the rates of feeding as the avidin level in the food increased. Death of the C. maculatus larvae usually occurred at the pupal/adult stage still within the host seed. Streptavidin, a biotin-binding protein from a bacterial source, had effects similar to chicken egg avidin.     

Monitoring protein binding to phospholipid monolayers using electrochemical impedance spectroscopy

Biotin was incorporated into dioleoyl phosphatidylcholine (DOPC) monolayers as dioleoyl phosphatidylethanolamine (DOPE)-biotin, DOPE-caproyl-biotin and DOPE-polyethylene glycol (PEG)-biotin. Experiments were carried out in electrolyte KCl (0.1 mol dm⁻³) buffered with 0.001 mol dm⁻³ phosphate buffer to pH 6.9. Bovine serum albumin (BSA), avidin, biotinylated anti-haemoglobin (IgG) and haemoglobin were added to the solution. The frequency dependence of the complex impedance of the coated electrode surfaces was estimated between 65,000 and 0.1 Hz at potentials −0.4 V versus Ag/AgCl 3.5 mol dm⁻³ KCl. The capacitance of the monolayers was measured at 75 Hz between potentials −0.4 and −1.1 V. Both non-specific and specific binding of the soluble proteins to DOPC gave rise to the occurrence of low frequency relaxations in the impedance data. The non-specific binding of BSA to DOPC can be suppressed by the incorporation of DOPE-PEG into the DOPC monolayer. The nature of the effect of specific binding of neutravidin to biotin on the impedance data depended on the positioning of the biotin group in relation to the DOPC monolayer surface. Successive binding of proteins to the biotin and then to each other gave rise to an increase in the significance of low frequency relaxations in the impedance data respectively.