双孢菇多酚氧化酶酶学特性研究

为了抑制双孢菇的褐变,研究温度、p H值、底物浓度和作用时间对双孢菇多酚氧化酶活性的影响。结果表明:该酶的最适温度为35℃、最适p H5.0、最适底物浓度0.07mol/L,90℃加热80 s时,该酶几乎全部失活。     

银杏叶中苯丙氨酸解氨酶基本特性的研究

苯丙氨酸解氨酶(PAL)在硼酸缓冲液中最适pH是8.8,在Tris-HCl缓冲液中最适pH为:pH8.0、pH8.8。用pH10和pH4 Tris-HCl处理,5min后,PAL活性分别残存13.07％,45.64％。PAL最适反应温度为50℃,在40℃、50℃水浴30min,60℃、70℃、80℃水浴20 min,90℃水浴10 min,100℃水浴5 min时,酶活性还残存50％左右。酶液酶活性残存50％左右时,贮存时间长短依次为:-20℃甘油贮存液37d、-20℃40％(NH4)2SO4悬浮液21d、-20℃上清液15d、4℃甘油贮存液21d、4℃上清液5d、4℃40%(NH4)2SO4悬浮液3d。PAL最适底物浓度为0.02mol·L-1,其Km为8.568×10-3mol·L-1。     

铁棍山药POD特性及褐变抑制研究

以铁棍山药为试材,采用分光光度法,研究了与其褐变相关的过氧化物酶(POD)的特性以及抑制剂对POD活力的影响.结果表明:铁棍山药POD对愈创木酚的最适反应pH为5.0,温度为50'℃,在80℃下温育5 min基本失活,酶促反应的最佳底物为愈创木酚,且最适浓度为0.04 mol/L,Km值为 0.012mol/L;L-半...     

黄瓜果实脂氧合酶活性测定方法的建立

采用紫外分光光度法,以亚油酸钠为反应底物,研究了黄瓜果实脂氧合酶(LOX)的酶活性测定方法。结果表明,黄瓜果实脂氧合酶最适pH为7.0,最适温度为40℃,最适底物浓度为3.3×10-4mol.L-1。该酶有着很好的热稳定性,90℃保温1h后仍具有很高的活性,70℃保温1h可能对该酶的活性有激活作用。     

金线莲驯化过程中光照强度(PPFD)对生长及光合速率的研究

[目的]研究光照强度对驯化过程中金线莲生长的影响。[方法]把金线莲器内苗分别在光照强度为20、50、100、150、200μmol/(m2.s)、光周期为16 h/d、温度为(25±2)℃的条件下,驯化培养3个月。[结果]结果表明,在50μmol/(m2.s)的光照强度下植株的鲜重和干重都最重,净光合速率最高。强光照强度降低叶绿素的含量,PSⅡ最大光化学效率(Fv/Fm)随着光照强度的增高而减弱。[结论]在光照强度强时金线莲诱发光抑现象,导致生长缓慢。50μmol/(m2.s)为驯化时最适光照强度。     

丝瓜多酚氧化酶及过氧化物酶酶学特性的研究

应用分光光度法研究丝瓜多酚氧化酶及过氧化物酶酶学特性的影响因素,为丝瓜酶促褐变的研究提供基础。以普通丝瓜果肉为材料,PPO以邻苯二酚为底物,POD以愈创木酚为底物,研究分析反应温度、反应时间、pH及测量波长、底物的浓度、PPO提取酶液添加量对丝瓜PPO、POD活性的影响。丝瓜褐变相关酶提取和测定方法的优化:(1)PPO最佳反应体系:测定波长408nm、反应温度是35℃、pH为6.0、酶液用量0.15mL,最适底物为邻苯二酚,底物浓度为0.056mol·L~(-1);(2)POD最佳反应体系:测定波长410nm,反应温度为40℃,最佳pH为5.5,酶液用量0.1mL,底物是愈创木酚,浓度为0.067mol·L~(-1)。     

温度和光照对缘管浒苔光合作用的短期交互影响

为研究温度和光照对缘管浒苔Ulva linza光合作用的短期交互影响,设置了不同温度和光照交互作用藻体24 h的试验,试验设置30℃(高温)、20℃(最适温度,对照)、4℃(低温)3个温度组,在每个温度下设置400μmol/(m²·s)(高光照)、100μmol/(m²·s)(最适光照,对照)和20μmol/(m²·s)(低光照)3个光照度,试验结束时进行了转录组学测序和光合荧光参数的测定。结果表明：试验周期内,缘管浒苔光合作用相关基因的表达变化受温度的影响大于光照,30℃和4℃下藻体的差异表达基因更多,其中,碳同化相关酶基因表达情况变化较大;短期高温和高光照处理对缘管浒苔具有协同胁迫作用,在高温高光照处理下,藻体的光化学效率(F_v/F_m)显著下降且差异表达基因最多,其中,光合固碳相关差异基因表达显著下调(P<0.01);低光照处理提高了缘管浒苔对低温的耐受性,此条件下藻体的F_v/F_m显著高于单一低温下;在低温低光照处理下,缘管...     

余甘子果实多酚氧化酶活性影响因素研究

多酚氧化酶(PPO)是酶促褐变的关键酶,以余甘子(Phyllanthus emblica)果实PPO为研究对象,采用分光光度法研究余甘子果实PPO作用的最适底物,同时探究反应体系pH、反应温度、底物浓度、抑制剂对余甘子果实中PPO活性的影响。结果表明,余甘子果实PPO作用的最佳底物为焦性没食子酸,最适pH为6.0,最适反应温度为10℃,底物最佳浓度为0.14 mol/L,抗坏血酸(VC)、柠檬酸、亚硫酸钠、L-半胱氨酸4种抑制剂对余甘子果实PPO活性均表现出不同程度的抑制作用,其中抗坏血酸对余甘子果实PPO活性抑制效果最好。     

重组酶Xar的表达纯化及性质研究

为获得高效的半纤维素类饲料酶制剂,将含嗜热厌氧乙醇菌α-阿拉伯糖苷酶/木糖苷酶(Xar)基因的重组质粒p ET-20b-xar导入大肠杆菌DH10B中,经IPTG诱导进行高效表达,将表达的重组酶进行热处理和Ni~(2+)亲和层析纯化,并对纯化的重组酶Xar的性质进行研究。结果表明,以对硝基苯酚-α-阿拉伯呋喃糖苷(p NPAF)为底物,重组酶Xar的最适反应温度和最适p H值分别是75~80℃和6.0,米氏常数(Km)、最大反应速度(Vmax)分别为2.42 mmol/L、20.7μmol/(min·mg);以对硝基苯酚-β-木糖苷(p NPX)为底物,重组酶Xar的最适反应温度和最适p H值分别为93℃和5.8~6.2,Km、Vmax值分别为0.60 mmol/L、43.8μmol/(min·mg)。将重组酶Xar置于80℃保温1 h,木糖苷酶的相对活性仍为56.4%,在p H值4.2~8.2条件下仍保持较高的稳定性。当木糖浓度达到400 mmol/L时,木糖苷酶的相对活性仍有97.9%。Mn~(2+)对重组酶Xar有明显的激活作用,而Cu~(2+)和Zn~(2+)对其有明显的抑制作用。可见,重组酶Xar具有良好的热稳定性。     

壳聚糖固定化氨基酰化酶的研究

以壳聚糖为载体,戊二醛为交联剂,用吸附交联法对氨基酰化酶进行了固定化研究.结果表明,在pH值为6.0,温度30℃的条件下,0.1g壳聚糖微球与5mL 1%戊二醛交联后,固定0.8mg氨基酰化酶的固定化效果最佳.固定化酶的最适温度和pH值分别为50℃和7.0,而游离酶的最适温度为40℃,最适pH值为7.5,固定化酶在50～70℃都保持了较高的酶活力,热稳定性远高于游离酶,固定化酶的Km值为11.796×10-2mol/L,较游离酶有所升高,该固定化酶具有良好的操作稳定性.     

Segregation of form, color, movement, and depth: anatomy, physiology, and perception

Anatomical and physiological observations in monkeys indicate that the primate visual system consists of several separate and independent subdivisions that analyze different aspects of the same retinal image: cells in cortical visual areas 1 and 2 and higher visual areas are segregated into three interdigitating subdivisions that differ in their selectivity for color, stereopsis, movement, and orientation. The pathways selective for form and color seem to be derived mainly from the parvocellular geniculate subdivisions, the depth- and movement-selective components from the magnocellular. At lower levels, in the retina and in the geniculate, cells in these two subdivisions differ in their color selectivity, contrast sensitivity, temporal properties, and spatial resolution. These major differences in the properties of cells at lower levels in each of the subdivisions led to the prediction that different visual functions, such as color, depth, movement, and form perception, should exhibit corresponding differences. Human perceptual experiments are remarkably consistent with these predictions. Moreover, perceptual experiments can be designed to ask which subdivisions of the system are responsible for particular visual abilities, such as figure/ground discrimination or perception of depth from perspective or relative movement--functions that might be difficult to deduce from single-cell response properties.     

Mineralogy, petrology, and surface features of lunar samples 10062,35, 10067,9, 10069,30, and 10085,16

The primary rocks are a sequence of titanium-rich basic volcanics, composed of clinopyroxene, plagioclase, and ilmenite with minor olivine, troilite, and native iron. The soil and microbreccias are respectively loose and compacted mixtures of fragments and aggregates of similar rocks, minerals, and glassy fragments and spheres. Impact events are reflected by the presence of shock metamorphosed rock fragments, breccias, and glasses and their resulting compaction to form complex breccias, glass-spattered surfaces, and numerous glass-lined craters. Chemistry of the glasses formed by the impact events is highly variable, and the high iron and nickel content of a few moundlike features suggests that at least some of the projectiles are iron and nickel-rich meteorites.     

Research and development, productivity, and inflation

R & D, through its effects on the rate of productivity increase, can significantly restrain the rate of inflation in the medium and long run. High rates of inflation damage the workings of the price system and impair the efficiency of practically all economic activities, including R & D. Findings suggest that the percentage increase between 1969 and 1979, in total real R & D expenditures, has been exaggerated due to the inadequacy of the gross national product deflator as applied to R & D.