菜芙蓉多糖对秀丽隐杆线虫抗氧化作用的研究

为进一步研究菜芙蓉多糖（AMP）的体内生物学作用,系统探究其抗氧化机理,以秀丽隐杆线虫(Caenorhabditis elegans)为模型,分析了正常生长条件及氧化应激条件下,空白对照组(0 mg/mL)、低剂量组(25 mg/mL)、中剂量组(50 mg/mL)、高剂量组(100 mg/mL)AMP对线虫生理指标、生化指标及细胞凋亡的影响。结果表明,正常生长条件下AMP可延长线虫寿命、降低生殖能力、提高运动能力,降低线虫体内MDA和ROS含量、提高SOD,CAT和GSH-Px 的酶活性。在200 μmol/L胡桃醌氧化应激条件下,AMP可提高线虫存活率,并能有效清除体内ROS、降低MDA含量,提高线虫体内SOD,CAT和GSH-Px 的酶活性,抑制细胞凋亡。AMP可通过提高线虫体内抗氧化防御系统酶活性及清除自由基提高氧化应激抵抗力,因此AMP有潜力成为一种新的抗氧化天然多糖。     

鸡精中呈味核苷酸二钠的高效液相色谱法测定

建立了高效液相色谱法测定呈味核苷酸二钠(IMP和GMP)含量的方法.以四丁基磷酸铵和磷酸二氢钾配以一定比例的乙腈为流动相,采用高耐水系Waters RP 18色谱柱,通过色谱条件的优化,获得了定性定量重复性相对标准偏差<2%的标准品色谱图,其中,IMP标准曲线在60～600μg/mL范围内的线性相关系数为R=1.0000,GMP标准曲线在50～480μg/mL范围内的线性相关系数为R=0.999 9.测得某品牌的鸡精内IMP质量含量为0.54%,GMP质量含量为0.60%,两次测定结果的精密度GMP为0.73%,IMP为1.17%.     

水合二氧化钛-磷钼酸铵微球复合无机离子交换剂的结构与性能

水合二氧化钛磷钼酸铵 (HTO AMP)球形复合无机离子交换剂在一定条件下具有对Cs+ 和Sr2 + 同时交换的性能 .从对复合交换剂组成分析看 ,有一部分基体二氧化钛在复合过程中转变为磷酸钛 ;结构分析表明 ,复合交换剂很稳定 ,与HTO和AMP的混合样品存在很大差异 ,在复合材料中可能形成新化学键Ti—O—Mo键 .将HTO AMP和磷酸钛磷钼酸铵 (TiPAMP)对Cs+ 的交换性能作了比较 ,发现前者的交换速率快 ,后者的交换容量则更大 ,但洗脱效果不如前者 .     

木薯酒精酵母菌种工程化选育的思路和方向

我国木薯酒精企业的发酵水平低,而国内酵母研究技术水平较高,但其选育的优良酵母菌种未能在企业得到推广应用,原因是高酒度等性能的酵母菌种需要改变现有工艺条件。因而,在不改变现有工艺条件下提高菌种的优良性能是木薯酒精酵母菌种选育的原则。本文在总结我国木薯酒精发酵技术现状的基础上,分析木薯酒精生产企业对酵母性能的要求,提出了现有工艺条件下酵母菌种工程化选育的思路和方向,为木薯酒精酵母菌种选育提供参考。     

毛细管电泳分析牦牛肉中肌苷酸含量方法的优化

为提高毛细管电泳(CE)测定牦牛肉中肌苷酸(IMP)含量的效率,用高氯酸法提取3岁公牦牛(n=8)背最长肌中的IMP,然后用短毛细管柱(有效长度30 cm)检测IMP含量.结果表明,短毛细管柱与长毛细管柱(有效长度50 cm)相比,测定的IMP含量十分接近,而且短柱获得的峰形更尖锐,检出时间缩短到3.5 min,在IMP浓度为10μg/ml~160μg/ml范围内具有良好的线性关系(R2=0.9974);通过精密度、加标回收率测定,以及IMP与其他几种核苷酸一磷酸的分离,均显示短毛细管柱对IMP的分离定量与长毛细管柱相近.建立了一种快速、低成本检测牦牛肉中IMP含量的方法.     

酵母菌对铅离子的吸附等温线研究

啤酒酵母菌作为吸附剂可以去除水溶液中的铅离子.分别在293,298,303 K时研究了铅离子质量浓度对吸附量的影响.质量浓度增加,吸附量增加,升温不利于吸附.用非线性回归分析对吸附等温线进行了拟合,在实验条件下Langmuir,Freundlich,Redlich-Peterson,Koble-Corrigan和Temkin模型均可用于分析等温线,其中Redlich-Peterson模型最好.293 K时酵母菌对铅的最大吸附量为6.07 mg/g.     

酵母菌厌氧发酵机制的教学探讨

酵母菌的厌氧发酵机制是微生物发酵机理的重要内容之一.然而,目前教材编排仍主要以产品进行分类,且代谢流过于复杂,使知识晦涩难懂.本研究以酵母菌为主旨,简明扼要地汇总分析了不同发酵条件下其发酵机制,使学生更容易掌握该知识点,促进其对微生物发酵机理知识的融会贯通,提升学习品质.     

含α-乙酰乳酸脱羧酶基因重组酿酒酵母的啤酒发酵

利用E .coli和酿酒酵母的穿梭质粒pYES2为载体 ,将地衣芽孢杆菌α 乙酰乳酸脱羧酶基因导入酿酒酵母中 ,构建了重组质粒pYEA ,实现了α 乙酰乳酸脱羧酶基因在酵母菌中的表达 .α 乙酰乳酸脱羧酶基因在酵母菌中的表达与菌体生长有关 .pYEA质粒在无选择压力的发酵条件下 ,仅能保持一定的稳定性 ,并具有降解α 乙酰乳酸的能力 ,但丢失率比较高 .     

耐酸酵母菌的筛选研究

依据白酒厂对酵母菌生产性能的特殊要求,并针对酵母菌的生理特性,采用差异酸度的培养基作选择条件,分别从采集于白酒厂的黄浆水、酒糟、酒曲、窖泥等含菌材料中,经分离、鉴定、筛选等相关技术方法,选择耐酸酵母菌.结果表明:通过酸性梯度差异培养法,分离到的兼性耐酸性酵母菌能在pH≤4的环境下继续表现出较强发酵代谢能力,适宜作白酒发酵生产用菌种.     

基于模糊控制的自适应播放算法

自适应媒体播放(AMP) 技术是提高流媒体播放性能的一种有效方法.为了减轻传统的AMP由于播放速度突变而对播放质量带来的影响,提出一种基于模糊控制的自适应媒体播放算法.通过当前缓冲和播放速度的情况来动态调节播放速度,产生比较平稳变化的播放速度,同时保持缓冲在一定范围内变化.仿真结果表明: 该算法能够在保持缓冲下溢概率和播放延迟基本不变的前提下,使播放速度变化幅值和变化增量减小到原有AMP算法的10%以下,该算法优于原有AMP算法.     

蜂花粉的灭菌和发酵试验

蜂花粉营养十分丰富，但花粉含杂菌较多，且具有苦涩味，不易为人们接受。我们通过温差灭菌，酵母菌发酵，乳酸菌发酵，以及米曲霉和酵母菌混合发酵，解决这一难题，收到良好效果。     

固定化啤酒酵母细胞生物合成三磷酸腺苷(ATP)的研究

用明胶包埋、戊二醛交联的方法制备固定化啤酒酵母细胞,方法简便、成本低廉、菌体包埋量大、机械性能好。初步考查用8％明胶溶液10毫升包埋15克湿菌体,1％戊二醛浸泡12分钟所制备的固定化细胞,在PH7.5、35℃、1mg/ml镁离子,6mg/mlAMP、1％葡萄糖、0.2M磷酸盐条件下,AMP转化为ATP的转化率最高。     

常温干燥法制备纳米炭粉

以煤焦油沥青为原料,浓硫酸和浓硝酸为氧化剂,利用溶胶-凝胶方法制备水性中间相沥青.将水性中间相沥青溶解于氨水中得到水相炭基凝胶,经过乙醇与水交换后进行常温干燥和热处理制备纳米炭粉.利用FT-IR光谱、TG、XRD和TEM等分析手段对水性中间相沥青、纳米炭原粉以及纳米炭粉进行了表征.结果表明:采用常温干燥方法制备纳米炭粉是可行的,制得的纳米炭粉粒度均匀、规则,形状近似于球形,平均粒径为20 nm左右,其炭结构为无序的乱层石墨结构.在沥青与混酸氧化过程中,主要发生硝化、氧化、磺化反应;纳米炭原粉的热解过程分为脱醇脱水、预热解、强烈热分解和结构重排等四个阶段.     

Patch- and voltage-clamp analysis of cyclic AMP-stimulated inward current underlying neurone bursting

The second messenger cyclic AMP has been variously reported to affect the electrical activity of different neurones by decreasing outward potassium current, increasing outward current and increasing inward current. The recently developed patch clamp method of recording single ionic channels allows direct measurement of the action of cyclic AMP on membrane conductances. Using the patch clamp, the closure of potassium channels by cyclic AMP has previously been documented on the single channel level. We report here that in a bursting molluscan neurone, intracellular iontophoresis of cyclic AMP under voltage clamp elicits an inward current of maximal amplitude in the pacemaker voltage region. Patch-clamp analysis reveals inward channels whose opening frequency is augmented by cyclic AMP stimulation and whose activity accompanies burst episodes. Channel opening frequency is significantly increased by depolarization of the whole soma, but not by focal depolarization of the patch; this may reflect the action of another second messenger that acts in concert with cyclic AMP to confer voltage sensitivity.     

Nerve growth factor induces adrenergic neuronal differentiation in F9 teratocarcinoma cells

Teratocarcinoma cells have been used as a model to study differentiation and development in vertebrates. Treatment with retinoic acid (RA) and dibutyryl cyclic AMP can in some embryonal carcinoma (EC) cell lines lead to neural differentiation, as judged by neurofilament expression and by the induction of enzymes involved in cholinergic transmission. Short-term culture of F9 line cells with RA and dibutyryl cyclic AMP results in a biochemically demonstrable rise in acetylcholinesterase (AChE) activity. We now report that long-term culture of F9 cells with RA and dibutyryl cyclic AMP induces neurofilament expression, demonstrated by immunofluorescence with specific antibodies. Furthermore, if nerve growth factor (NGF) is also added, the developing neurone-like cells exhibit immunoreactivity to tyrosine hydroxylase, a rate-limiting enzyme of catecholamine synthesis specific for adrenergic neurones. Immunoreactivity for Leu-enkephalin-like peptides is also induced. These results suggest that F9 cells can differentiate into cells with adrenergic characteristics.     

从吉林林蛙干皮中提取抗菌肽

从吉林林蛙干皮中分离提取了具有广谱抗菌作用的多肽 ,制备得到抗菌肽样品。在实验中摸索出提取抗菌肽的最佳工艺路线 ,建立了抗菌肽的纯化方法 ,并对所得到的抗菌肽的氨基酸进行组成分析     

Substituted benzimidazoles inhibit gastric acid secretion by blocking (H+ + K+)ATPase

Studies both in vivo and in vitro have shown that substituted benzimidazoles inhibit the stimulation of acid secretion produced by dibutyryl cyclic AMP and histamine. Furthermore, the results differ from those produced by H2 antagonists and anticholinergic agents in that the inhibition is not competitive, and the site of action is intracellular and peripheral to that of dibutyryl cyclic AMP. To investigate the biochemical mechanism of action of substituted benzimidazoles, one such compound, H 149/94 (2-([2-(3-methyl)pyridyl-methyl]-sulphinyl)-5-methoxycarbonyl-6-methylbenzimidazol), has been tested either directly on an (H+ + K+)ATPase isolated from pig and human gastric mucosa or on the function of this enzyme in gastric glands isolated from rabbit and human gastric mucosa. (H+ + K+)ATPase, which has only been found at the secretory surface of the parietal cell, catalyses a one-to-one exchange of protons and potassium ions. It is possibly the proton pump within the gastric mucosa, and may thus be the terminal or one of the terminal steps of the acid secretory process. We show here that H 149/94 inhibits (H+ + K+)ATPase, which may explain its inhibitory action on acid secretion in vitro and in vivo. Because of the unique distribution and properties of the (H+ + K+)ATPase, the inhibitory action of H 149/94 on this enzyme may be a highly selective clinical means of suppressing the acid secretory process.     

The allosteric transition of glycogen phosphorylase

The crystal structure of R-state glycogen phosphorylase b has been determined at 2.9 A resolution. A comparison of T-state and R-state structures of the enzyme explains its cooperative behaviour on ligand binding and the allosteric regulation of its activity. Communication between catalytic sites of the dimer is provided by a change in packing geometry of two helices linking each site with the subunit interface. Activation by AMP or by phosphorylation results in a quaternary conformational change that switches these two helices into the R-state conformation.     

Cyclic GMP increases photocurrent and light sensitivity of retinal cones

Like retinal rods, cone photoreceptors contain cyclic GMP and light-activated phosphodiesterase. The cGMP phosphodiesterase cascade is thought to mediate phototransduction in rods. Biochemical assays of nucleotide content in cone-dominant retinas, however, have failed to demonstrate light-induced changes in cGMP. Changes in cyclic AMP following light exposure have been reported, leading to the suggestion that in cone phototransduction cAMP assumes a role analogous to that played by cGMP in rods. Cyclic GMP introduced from tight-seal pipettes into isolated cones of the larval tiger salamander, Ambystoma tigrinum, rapidly increases light-modulated membrane current more than 10-fold. In cones, as in rods, cGMP also causes an approximately 10-fold increase in photocurrent duration and a 5- to 10-fold increase in light-sensitivity. Cyclic AMP has no effect on cone photocurrents under the same conditions. Because cGMP has similar effects on photocurrent magnitude and kinetics in both rods and cones, we conclude that cGMP plays corresponding roles in transduction in both vertebrate photoreceptor classes.     

Cloning and expression of human and rat D1 dopamine receptors

The importance of the dopaminergic system in brain function has been emphasized by its association with neurological and psychiatric disorders such as Parkinson's disease and schizophrenia. On the basis of their biochemical and pharmacological characteristics, dopamine receptors are classified into D1 and D2 subtypes. As the most abundant dopamine receptor in the central nervous system, D1 receptors seem to mediate some behavioural responses, modulate activity of D2 dopamine receptors, and regulate neuron growth and differentiation. The D dopamine receptor has been cloned by low-stringency screening. We report here the cloning of human and rat D1 dopamine receptors by applying an approach based on the polymerase chain reaction. The cloned human D1 dopamine receptor has been characterized on the basis of four criteria: the deduced amino-acid sequence, which reveals that it is a G protein-coupled receptor; the tissue distribution of its messenger RNA, which is compatible with that of the D1 dopamine receptor; its pharmacological profile when transfected into COS-7 cells; and its ability to stimulate the accumulation of cyclic AMP in human 293 cells.