基才隐马尔可夫模型的蛋白质序列筛选算法

对蛋白质序列筛选算法进行了研究,针对蛋白质数据库中存在大量的冗余序列,提出了一种基于隐马尔可夫模型的蛋白质序列筛选算法。详细阐述了在蛋白质数据库中如何建立隐马尔可夫模型。对模型中主要参数的求解和估计给出了主要计算公式。然后利用所建立的模型对蛋白质数据库进行的序列筛选测试,测试结果表明本文设计的算法对同源蛋白质序列筛选精...     

Epitope-Imprinted Nanoparticles as Transforming Growth Factor-β3 Sequestering Ligands to Modulate Stem Cell Fate

Growth factors (GFs) are biomolecules with potent biological effects but inherent limitations hinder their potential as therapeutic agents and cell culture supplements in tissue engineering and regenerative medicine (TERM). Biomaterials that sequester endogenous GFs by affinity binding might circumvent such limitations and thus are being increasingly investigated. Here, molecularly imprinted nanoparticles (MINPs) are proposed as specific abiotic ligands for GFs. As a proof of concept, a conformational epitope of transforming growth factor-β3 (TGF-β3) is designed and surface imprinted onto polyacrylamide-based nanoparticles by inverse microemulsion polymerization. It is found that, depending on the polymerization mixture composition, MINPs can recognize and preferentially bind TGF-β3, either in noncompetitive assays or from a complex human fluid (platelet lysate). Substrates functionalized with MINPs are then used for 2D culture of adipose-derived stem cells. Remarkably, gene and protein expression profiles show a marked upregulation of SOX-9, suggesting activation of TGF-β3 signaling pathways without requiring supplementation with exogenous GF. Likewise, culturing these cells in pellets incorporating MINPs previously incubated with platelet lysate results in higher collagen II-rich matrix deposition, compared to pellets incorporating non-imprinted nanoparticles. In summary, results suggest MINPs can be used as cost-effective, stable, and scalable alternative abiotic GF ligands to guide cell fate in TERM applications.     

Nutritional supplements to increase muscle mass.

Although nutritional supplements purported to increase muscle mass are widely available at health food stores, gyms, by mail order, and over the Internet, many of these supplements have little or no data to support their claims. This article reviews the theory and research behind popular nutritional supplements commonly marketed as muscle mass builders. Included are the minerals chromium, vanadyl sulfate, and boron, the steroid hormone dehydroepiandrosterone (DHEA), beta-methyl-hydroxy-beta-methylbutyrate (HMB), creatine, protein supplements, and amino acids. Research has shown that chromium vanadyl sulfate, and boron do not appear to be effective in increasing lean body mass. The few studies examining DHEA have not supported the claim of increased muscle gain. Preliminary work on HMB supports an anticatabolic effect, but only one human study is currently available. Many studies reported increased body mass and several have reported increased lean body mass following creatine ingestion. This weight gain is most likely water retention in muscle but could also be due to some new muscle protein. Although athletes have a greater protein requirement than sedentary individuals, this is easily obtained through the diet, negating the use of protein supplements. Studies on amino acids have not supported their claim to increase growth hormone or insulin secretion. Nutritional supplements can be marketed without FDA approval of safety or effectiveness. Athletes who choose to ingest these supplements should be concerned with unsubstantiated claims, questionable quality control, and safety of long-term use.     

Water Vapor Permeability of Whey Protein Emulsion Films as Affected by pH

The water vapor permeability (WVP) of whey protein isolate-beeswax emulsion films was investigated as related to pH. Lower WVP was observed for films cast from solutions at pH 7.0. When pH of the film-forming solution was lowered, resulting film WVP increased. At the isoelectric point, WVP was the highest. As pH of the emulsion approached pI, a sharp change in viscosity occurred due to an increase in protein aggregation. This increase in viscosity probably lowered lipid mobility and reduced interconnectivity among lipid droplets, resulting in the higher WVP. For minimum WVP, such films should be applied at pH different from pI.     

Apparent chemical composition of nine commercial or semi-commercial whey protein concentrates, isolates and fractions

Summary Analytical results are given for whey powders prepared on a commercial or semi-commercial scale by three companies. Altogether, five preparations enriched in β-lactoglobulin, four whey protein isolates and a fraction enriched in α-lactalbumin were analyzed for protein composition, including %β-lactoglobulin, α-lactalbumin, bovine serum albumin, casein (glyco) macropeptide and the main triglycerides. Protein composition was determined by high pressure gel permeation and reversed phase liquid chromatography and by capillary zone electrophoresis. The extent of modification of the native β-lactoglobulin structure was also measured through the degree of lactosylation and the fraction of accessible free sulphydryl groups. One significant finding was that the calculated recovery of protein following quantitation of the chromatogram or electropherogram was seldom above 90% and occasionally below 60% of that loaded onto the column or capillary, raising doubts as to the reliability of the analytical results. Extrapolation by linear regression to 100% recovery allowed estimates to be made of the true β-lactoglobulin composition of the samples. The nine samples could be placed into three distinct groups with estimated true β-lactoglobulin weight % of 70.9 ± 1.1, 62.0 ± 3.4 and 39.5 ± 4.9. Physico-chemical properties of the group of samples are reported elsewhere (Holt et al ., 1999).     

Thermal Aggregation of Whey Proteins in Model Solutions as Affected by Casein/Whey Protein Ratios

Model solutions (32.5 g protein/L) prepared from milk, ultrafiltration permeate, and whey protein isolate were adjusted at pH 6.7 to casein:whey protein (C:W) ratios of 80:20, 60:40, 40:60,20:80, and 0:100. Heating was performed in test tubes at 95 °C for 5 min. Observations of the heated suspensions revealed the occurrence of heterogeneous particulates from the existing casein micelles complexed with denatured whey proteins and from aggregates essentially consisting of denatured whey proteins. The proportion of whey protein aggregates increased as C:W was changed from 80:20 to 20:80. The results from this study confirmed that heat-induced aggregates were formed not only from casein micelles but also from heat-denatured whey proteins.     

乳蛋白生物活性肽的研究概述

对源于乳蛋白的生物活性肽作一介绍,主要包括：阿片样肽,降血压肽,抗血栓肽及免疫促进肽等。这些活性肽的发现为今后进一步利用乳蛋白资源,生产功能食品基料或药品提供了一条新的途径。     

大豆蛋白的吸水和持水性能

对大豆蛋白的吸水和持水性能及其影响因素进行了论述,大豆蛋白制品吸水能力的差别很小,一般为 ４０ ｇ 水／１００ ｇ 蛋白～６０ ｇ 水／１００ ｇ 蛋白。大豆蛋白制品的持水能力差别很大,约为１３０ ｇ 水／１００ ｇ 蛋白～６２５ ｇ 水／１００ ｇ 蛋白,持水性能在本质上是蛋白分子物理截留水的能力,其影响因素包括蛋白分子大小、形状、空间、构象等。高分子物理方法是一种新的研究方法,对这个方法在大豆蛋白吸水及持水性能方面的应用进行了讨论。     

变性豆粕中蛋白质的酶水解特性的研究

变性豆粕是由大豆浸油后,经高温脱溶所得。本文以高温变性脱脂大豆粕为原料,用正交实验法对变性后在蛋白酶作用下的水解特性进行了深入研究。选用国产1398中性蛋白酶为水解酶对变性豆粕进行水解,研究了变性豆粕中蛋白质溶出率随温度、pH值、时间、底物浓度及用酶量的变化规律,找到了水解变性豆粕的最佳实验条件。为生产实践提供了基础数据,该研究结果对其它蛋白质原料的水解特性研究也具有参考价值。研究结果表明：1398中性蛋白酶水解高温变性豆粕的最佳条件为：温度45℃,时间3h,底物浓度1．0％,用酶量1600u/g,pH值7．0,在此条件下,变性豆粕中蛋白质可有90．71％水解溶出。     

Effects of cultivar and soil fertility on grain protein yield,grain protein content,flour yield and breadmaking quality of wheat

Grain protein content affects the flour yield and breadmaking characteristics of wheat (Triticum aestivum L). In this study, grain protein yield, grain protein content, flour yield and loaf volume were quantified for four wheat cultivars (Inia, Carina, Kariega and SST 86) grown under six different soil fertility regimes in a long-term fertilisation and irrigation experiment at the University of Pretoria. The experimental design was a randomised complete block replicated four times, with fertility as the main plots and cultivars as the subplot treatments. Grain protein yield, flour yield, loaf volume and mixograph dough peak mixing time varied among cultivars and soil fertility situations. Grain protein content differed among cultivars, but mixograph water absorption and dough characteristics did not differ. The highest grain protein yield was 873 kg ha⁻¹ for Carina and the lowest 527 kg ha⁻¹ for SST 86. Grain protein content averaged 131 g kg⁻¹ for Carina and 122 g kg⁻¹ for Kariega. Breadmaking performance showed that in a well-balanced soil fertility situation, Kariega produced 1025 cm³ of loaf volume while Inia averaged 950 cm³. Grain protein yield increased with increasing soil fertility, but grain protein content, flour yield, loaf volume, water absorption and mixograph peak mixing time varied with soil fertility. The interaction between cultivar and soil fertility was significant for grain protein yield, grain protein content, flour yield, loaf volume and water absorption but not dough peak mixing time. The results indicate cultivar differences in breadmaking quality characteristics and that soil fertility status affects grain protein yield, grain protein content, flour yield, loaf volume potential and water absorption but not mixograph peak mixing time and dough characteristics. © 1999 Society of Chemical Industry