A new family of yeast genes implicated in ergosterol synthesis is related to the human oxysterol binding protein

We have identified three yeast genes, KES1, HES1 and OSH1, whose products show homology to the human oxysterol binding protein (OSBP). Mutations in these genes resulted in pleiotropic sterol-related phenotypes. These include tryptophan-transport defects and nystatin resistance, shown by double and triple mutants. In addition, mutant combinations showed small but apparently cumulative reductions in membrane ergosterol levels. The three yeast genes are also functionally related as overexpression of HES1 or KES1 alleviated the tryptophan-transport defect in kes1Δ or osh1Δ mutants, respectively. Our study implicates this new yeast gene family in ergosterol synthesis and provides comparative evidence of a role for human OSBP in cholesterol synthesis.     

Characterization of Acetyl Starch by Means of NMR Spectroscopy and SEC/MALLS in Comparison with Hydroxyethyl Starch

The properties of starch derivatives which may be used as plasma substitutes, are dependent upon the molecular structure. Seven acetyl starch (AS) samples were determined and compared with results from hydroxyethyl starch (HES) samples. The molar masses and their distributions were determined with the combination of size exclusion chromatography and light scattering. Slightly asymmetric distributions were determined with a polydispersity M_w/M_n = 2.4 and weight-average molar masses of M_w = 250,000–300,000 g/mol for six AS samples and M_w/M_n = 3.6 and a weight-average molar mass of 766,000 g/mol for one AS sample. The average degrees of substitution (DS) and the substitution pattern were determined by high resolution NMR spectroscopy. The AS samples investigated had a DS of 0.42 to 0.81, comparable to HES, but the regioselective substitution pattern revealed differences. While for HES the position C-2 is preferred and the position C-3 has nearly no substituent, for AS both positions, C-2 and C-3, are substituted likewise. Degradability by α-amylase was tested in the laboratory for AS as well as for HES having nearly the same degree of substitution and molar mass, but C-2/C-6 = 2 for AS and C-2/C-6 = 1.4 for HES. An exponential decrease in the molar mass was observed over time, down to a limiting molar mass M_w = 50,000 g/mol for AS and M_w = 30,000 g/mol for HES, the degradation of AS occurred more slowly.     

Die Nutzung der Nah-Infrarot-Spektroskopie (NIR) zur Prozeßkontrolle bei der Synthese von Hydroxyethylstärke (HES)

The reaction of starch and ethylene-oxide giving hydroxy-ethyl starch (HES) can be controlled by near infra-red spectroscopy (NIR) The controlled parameter is the molar substitution (MS), which is measured by means of a probe directly from the neutralized and filtered reaction solution. According to the type of HES (200/0.5, 130/0.4 or 50/0.2) the measured MS depends on the concentration of HES in the solution. To prevent distorted results the content of HES 130/0.4 and HES 50/0.2 must be adjusted to 25% (w/v) for this individual calibration. Only in the case of HES 200/0.5 the concentration can vary between 19 and 29% for measuring the MS. Sodium chloride as a byproduct of the process does not effect the measurement up to 10% NaCl in the sample. The temperature of the solution does not influence the result significantly (in the range of 20 to 34°C). The reproducibility of the MS determination is good. The day-to-day standard deviation of 25 repetitions is +/– 0.005 for a sample with MS = 0.405. The relative standard deviation is 1,1%. Nevertheless the biggest problem for the determination of MS by NIR is ethylene glycol (EG), the most important by-product of the reaction. If the concentration of EG differs significantly from that in the calibration samples, the calibration of the method must be revised.     

A Study of Hydroxyethyl Starch. Part V. Some Physicochemical and Biological Properties of Hydroxyethyl Starch Isolated from the Blood and Urine,and Limit Hydroxyethyl Starch

Hydroxyethyl starch (HES) was isolated from blood and urine, and also limit HES was isolated which was obtained by exhaustive degradation of HES by α-amylase. From the study on their physicochemical properties and molecular-size distributions, the results were obtained that [η] and molecular substitution (M. S.) of HES isolated from the blood were almost unchanged, while [η] of HES isolated from urine was decreased and M. S. of it was slightly changed. Furthermore, it was calculated that limit HES contained only about 1.5% of higher-molecular-weight fractions against the amount of parent HES than those of HES excreted in urine.     

Immumochromatographic assay for determination of hexoestrol residues

One-step membrane-based competitive colloidal gold-based immunoassays in lateral-flow formats for the rapid detection of hexoestrol (HES) were developed. Nitrocellulose membrane strip was separately coated with goat anti-rabbit IgG (control line) and HES hapten–OVA conjugate (test line). Anti-HES polyclonal antibody labelled with colloidal gold particles was firstly incubated with HES. A positive reaction as a result of the remaining antibody–gold conjugate combining with antigen coated on the membrane was obvious by visual detection, with detection limits for lateral flow of 10 μg/kg for detecting HES standard solution, and the limit of detection was 20 μg/kg for detecting the HES spiked in swine urine and liver. The assay time for test was less than 5 min, suitable for rapid testing on-site.     

橙皮苷、柚皮苷与酪蛋白相互作用机制比较分析

采用荧光光谱、同步荧光光谱结合热力学参数分析及分子对接比较研究酪蛋白（casein,CA）与橙皮苷（hesperidin,HES）及柚皮苷（naringin,NAR）之间的相互作用及机制,结果表明：两种多酚对CA的猝灭均为静态猝灭,但HES对CA的荧光猝灭效果及结合亲和力较强,且CA与HES的结合位点数较多。热力学参数证明CA与HES、NAR的结合均为以疏水作用力为主的自发反应。同步荧光光谱显示,两种多酚的加入引起了CA氨基酸内部疏水环境的改变。分子对接进一步证实,两种多酚与CA的结合主要以疏水作用力为主,但HES与CA间存在更多的氢键作用,并使HES与CA之间结合得更为稳定。本研究可为多酚与蛋白质间的相互作用研究以及CA作为黄酮类多酚载体的可行性提供参考依据。     

Molar Mass Distribution and Size of Hydroxyethyl Starch Fractions Obtained by Continuous Polymer Fractionation

By the use of continuous polymer fractionation (CPF) the initial polymer can be separated into fractions of different molar masses, which makes it possible to obtain hydroxyethyl starch (HES) fractions tailor‐made for specific application. Two samples of HES (HES A and HES B) were fractionated by means of CPF. By size‐exclusion chromatography‐multi‐angle laser light‐scattering‐differential refractive index (SEC/ MALLS/DRI) measurements it was shown that CPF is able to remove the low‐molarmass components and to adjust the samples to various desired molar masses with lower polydispersities than the original samples. In terms of the weight‐average mean molar mass M_W , the sol fractions have smaller molar masses than the starting sample, whilst the gel fractions have higher molar masses. Furthermore the radius of gyration R_G could be determined for the initial sample HES B with 19.7 and 19.4 nm and also for some of its fractions. However, no general R_G—M_W relationship could be established for the HES samples fractionated using CPF. This is probably due to the complex branched structure of amylopectin. M_W and M_W/M_n of the six fractions obtained from HES A with M_W = 161, 000 g/mol and M_W/M_n = 4.7 ranged from 19, 000 to 362, 000 g/mol with M_W/M_n from 1.8 to 3.1. The molar masses of the four fractions obtained from HES B with M_W = 460, 000 g/mol and M_W/M_n = 6.0 were between 18, 000 and 680, 000 g/mol with M_W/M_n from 1.7 to 4.8 or between 202, 000 and 1, 005, 000 g/mol with M_W/M_n from 2.7 to 4.7 depending on fractionation strategy.     

Gaschromatographic Analysis of the Substitution Pattern of Hydroxyethyl Starch

The substitution parameters, molar substitution (MS) and degree of substitution (DS) for commercial O-(2-hydroxyethyl) derivatives (HES) of starch have been determined by measuring the relative amounts of glucose and its O-(2-hydroxyethyl) derivatives in hydrolysates of HES. The monomers in the hydrolysate were estimated by conversion to per-O-ethylated alditols which were analysed by gas chromatography. The identity of the monosubstituted derivatives was confirmed by their mass spectra and by synthesis of model compounds. Disubstituted monomers were identified by their mass spectra while trisubstituted components were not separated.     

A Study of Hydroxyethyl Starch. Part II. Degradation-Sites of Hydroxyethyl Starch by Pig Pancreas α-Amylase

The degradation sites of hydroxyethyl starch (HES) by pig pancreas α-amylase were determined by gas liquid chromatography. As a result, it was confirmed that HES could be hydrolyzed by α-amylase only at the glucosidic bond of unsubstituted glucose residues, but not at the bond of 2-0-, 3-0-, and 6-0-hydroxyethylglucose residues. Furthermore, it was suggested that the enzymic degradation rate of HES could be well determined by measuring the reducing power.     

Draw pH and Storage Affect Rheological Properties of Mozzarella Cheese

Cheeses with whey pH at draw of 6.15 or 6.40 were stored at 4°for 50 days. Compression test at 10°(Instron) showed a decrease in compressive stress with storage. Failure points were near a true strain value of 0.5 for the cheeses at day 3. The failure region became less obvious by day 50. The hypothetical equilibrium stress (HES) in the stress-relaxation test was higher with a draw pH of 6.40 than 6.15, possibly indicating that higher calcium led to a stronger network structure. The HES decreased with storage, suggesting cleavage of structural crosslinks caused by the coagulant.     

Strategies for increasing energy density of dry cow diets.

The objective of this trial was to compare the effects of increasing dietary energy density from 1.51 to 1.65 Mcal/kg of dry matter (DM) by replacing forage with concentrate or by further increasing concentrate via the substitution of corn silage and alfalfa silage by a mixture of straw, starch, and soybean meal. Our hypothesis was that the latter diet would be more glucogenic while increasing rumen fill and be potentially desirable for transition cows. Nine far-off dry cows (greater than 3 wk before parturition at the end of the trial) were fed three diets: low energy diet, [LE, 1.51 Mcal/kg of DM, 14.0% crude protein (CP) and 35% nonfiber carbohydrates (NFC)], high energy diet, (HE, 1.65 Mcal/kg of DM, 13.9% CP and 39.5% NFC) and high energy diet, where a portion of alfalfa and corn silage was replaced by straw, soybean meal, and cornstarch (HES, 1.65 Mcal/kg of DM, 13.5% CP and 40.5% NFC). The experiment was a replicated 3 x 3 Latin square design with 21-d periods. Six cows from two squares were used to examine kinetics of DM disappearance from nylon bags suspended in the rumen. Two contrasts of interest were: LE versus HE, HES (effects of energy density) and HE versus HES (method of increasing energy density). Increasing energy density increased the potentially degradable (B) and decreased the undergradable (C) DM fractions of the diets. Because HES had greater B and a faster rate of degradation of fraction B (k), effective rumen degradable DM (ERDDM) was higher in HES compared to HE. Cows fed high energy diets had greater DM intake. No differences in DM intake were observed between HE and HES. Rumen volume or DM pool sizes were not affected by treatment. High energy diets increased total ruminal fluid volatile fatty acid concentration compared with LE. Propionate concentration was higher in cows fed high energy diets compared with cows fed LE. The partial replacement of alfalfa and corn silage by straw, soybean meal, and cornstarch further increased propionate concentration. The greatest increase in serum insulin concentration following feeding was observed in cows fed HE. Cows consuming high energy diets had lower plasma nonesterified fatty acids (NEFA) before and after feeding. The HES diet was less effective in decreasing plasma NEFA concentration after feeding compared to HE. In conclusion, increasing diet energy density of far-off dry cows positively affected DMI, ruminal propionate, serum insulin, and plasma NEFA. Increasing energy density with a blend of feeds that represent extremes in rates of carbohydrate fermentation may be a strategy to provide greater amounts of glucogenic precursors. Applicability of this strategy should be examined in transition cows.     

Cryoprotective Role of Exogenous Trehalose in Frozen Dough Products

Aim of this work is to study the cryoprotective role of extracellular trehalose in the production of bakery products from frozen dough. Therefore, different levels of trehalose (up to 200 ppm) were incorporated in dough/bread samples made from white and whole-wheat flour, and their quality (loaf volume, weight loss during baking, crust and crumb color) and texture characteristics (dough, crust and crumb firmness) were examined during frozen storage. To investigate the role of trehalose on dough behavior, the sugar content (glucose, fructose, and sucrose) of dough samples composed with or without trehalose was monitored, and dough microstructure was also analyzed with scanning electron microscopy. The cryoprotective effect of trehalose was confirmed, and it was found proportional to its level for both flour types. Trehalose can improve dough behavior under freezing conditions in terms of bread volume and texture characteristics.     

鲢鱼酶解产物对酵母菌的抗冻保护作用

优选酵母抗冻剂对改善冷冻面团品质具有重要意义。通过酶法制备了系列鲢鱼酶解产物,分析其基本组成和电泳图谱变化,并考察酶解时间及其浓度对面包酵母冻融过程中存活率的影响。结果表明:面包酵母耐冻性差,1个冻融循环后存活率仅为0.69%;不同酶解时间的鲢鱼酶解产物基本组成相差不大,但酶解15,30min的酶解产物对酵母菌的抗冻保护效果最好;添加4%的30min酶解产物使酵母菌的冷冻存活率提高到90.73%,较8%的甘油提高了42.88%。Tricine-SDS-PAGE分析发现,酶解产物的蛋白条带分布基本相似,但信号随着酶解时间的延长逐渐减弱,其中新增约13kDa的蛋白可能与酶解产物的抗冻保护活性有重要关系。     

海藻糖对乳酸菌冷冻干燥保护机理的研究

研究了海藻糖对乳酸菌冷冻干燥的保护机理。用DSC方法测定海藻糖浓度和加热速度对海藻糖玻璃化转变温度的影响,海藻糖的浓度和升温速度对玻璃化转变温度都有影响,但浓度变化对海藻糖的玻璃化转变温度影响不显著。测定了几种糖类(10%)的玻璃化转变温度,发现海藻糖具有最高的玻璃化转变温度(-27.79℃),蔗糖为-31.43℃,葡萄糖为-42.90℃。通过对海藻糖和卵磷脂的混合物的红外光谱的分析结果表明,海藻糖能够和细胞膜成分形成氢键作用,取代水的位置,保护细胞膜的稳定性,为"水替代"假定提供支持。     

聚葡萄糖对冻藏鳙鱼鱼糜抗冻作用的研究

本文以Ca2+-ATP酶活性、肌原纤维蛋白溶出量、总巯基含量、二磺键含量、表面疏水性、水结合能力等的变化(WHC)为指标,研究了聚葡萄糖在4％、8％水平上对鳙鱼鱼糜蛋白在-18℃冻藏10周的抗冻作用,并与传统的商业抗冻剂(4％蔗糖+4％山梨醇)进行比较.结果表明:4％聚葡萄糖具有显著的抗冻作用,可与商业抗冻剂相比拟,而...     

嗜酸乳杆菌泠冻干燥过程中保护剂的选择

采用不同保护剂组合，对嗜酸乳杆菌在冷冻干燥中存活率进行了测定。结果表明，保护剂对提高冻干过程中嗜酸乳杆菌的存活率具有明显效果，且组合不同保护剂协同累加效果不同，其中10％脱脂乳 10％乳糖La-1和La-2的存活率均为100％。     

酸-冷交互胁迫对保护冷冻干燥发酵乳杆菌活性的作用

为探究酸-冷交互胁迫对冷冻干燥发酵乳杆菌(Lactobacillus fermentum)ATm的影响,考察酸-冷交互胁迫的处理方式对细胞存活率、滞后时间以及酸化速率的影响,同时测定交互胁迫对乳酸脱氢酶、ATP酶活性以及细胞膜完整性的影响。结果表明,pH 4.5、4℃酸-冷交互胁迫能够显著提高细胞冷冻干燥存活率及酸化速率,其中冷冻干燥存活率能够达到87.19%,优于单因素胁迫;pH 4.5、4℃酸-冷交互胁迫能够提高发酵乳杆菌ATm的冷冻干燥存活率保护其活性,提高酶活性,维持细胞膜完整性。     

瑞士乳杆菌冷冻干燥保护剂的研究

本实验采用单因素试验、正交试验及均匀试验对瑞士乳杆菌在冷冻干燥过程中的保护剂进行了研究,确定了复合保护剂的组成及用量。结果表明添加保护剂后,瑞士乳杆菌的冻干存活率都有不同程度的提高,复合保护剂效果明显优于单一保护剂,以10.4%海藻糖+4.0%谷氨酸钠+11.2%脱脂乳组合的效果为最佳,冻干存活率高达86.7%。     

复配大豆磷脂和蔗糖酯对面包酵母冷冻保护作用

以质量比为2∶1的大豆磷脂和蔗糖酯复配处理面包酵母,研究了其对酵母抗冻性的影响。结果表明,与未添加乳化剂组相比,酵母在-30℃含复配乳化剂质量分数为4 g/dL的YPD培养液中冷冻贮藏5 d,解冻并于30℃平板培养48 h,存活率提高了60%,酵母生长适应期缩短了10 h左右。将乳化剂处理酵母应用于冷冻面团体系,面团经-30℃冷冻贮藏60 d后醒发时间缩短,醒发体积增大。扫描电镜观察表明酵母与乳化剂呈聚集状,存在一定的交互作用。     

浓香型白酒饮用舒适度与白酒中微量成分相关性分析

目的:通过分析浓香型白酒饮用舒适度与白酒中微量成分之间的相关性,为浓香型白酒舒适度的评价提供指导。方法:使用气相色谱仪(GC)对白酒中的微量成分进行定量检测,运用饮用后感受评价表对各不同白酒进行舒适度评价,评分越高,说明白酒饮用舒适度越好。结果:通过对浓香型白酒不同样品的微量组分进行主成分分析,可以得到各档次白酒的综合指标得分,将感官得分与其建立起一种联系,能够得到四次方的回归方程X=54.76F4+53.936F3-20.175F2+11.629F+60.978,R2=0.9999。结论:该模型能够较为准确的对白酒档次进行分级,为不同种浓香型白酒的品质识别提供理论支持。