The Effects of the Porosity of a Support and of Attachment on the Mode of Action of Immobilized Endopolygalacturonase

Endopolygalacturonase of Aspergillus sp. was immobilized by three different methods; viz. (a) via amino groups, (b) via carboxyl groups and (c) by means of epoxy groups to a nonporous microparticular silicon dioxide (Cabosil), functionalized by 3-(amino)-propyl groups and 3-(2',3'-epoxypropoxy)-propyl groups, respectively. The conjugates were compared in their mode of action with corresponding immobilized preparations based on microporous ceramics. The binding via amino groups and via carboxyl groups lead, by itself, to changes in the mode of action of the enzyme, consisting of a decrease in randomness of glycosidic linkage splitting. The changes were greater in microporous support conjugates due to additional size-exclusion effects. The action pattern of endopolygalacturonase bound by means of epoxy groups was modulated exclusively by the porosity of the support, whereas the binding alone did not play any role.     

Effect of the Pore Size of a Support on Activity and Action Pattern of Immobilized Endopolygalacturonase

Endopolygalacturonase (E.C. 3.2.1.15) was covalently bound to silica supports of different porosity treated with 3-(2',3'-epoxypropoxy)propyltrimethoxysilane. The activity and action pattern on sodium pectate and tetra(D-galactosiduronic acid) were investigated in batch and continuous flow-reactors. Pore size of the supports affected the loading of the enzyme as well as its action pattern and kinetics. A decrease in randomness of degradation of D-galacturonan, loss of specificity of (3 + 1) splitting of tetra(D-galactosiduronic acid) and decrease in K_m value were found with the supports containing predominantly micropores. The extent of the changes decreased with increasing pore size of the support. The catalytic behaviour of endopolygalacturonase bound on the supports with large pores was quite analogous to that of the free enzymes.     

Effect of the Pore Size of a Support on Activity and Action Pattern of Immobilized Endopolygalacturonase

Endopolygalacturonase (E.C. 3.2.1.15) was covalently bound to silica supports of different porosity treated with 3-(2′,3′-epoxypropoxy)propyltrimethoxysilane. The activity and action pattern on sodium pectate and tetra(D-galactosiduronic acid) were investigated in batch and continuous flow-reactors. Pore size of the supports affected the loading of the enzyme as well as its action pattern and kinetics. A decrease in randomness of degradation of D-galacturonan, loss of specificity of (3 + 1) splitting of tetra(D-galactosiduronic acid) and decrease in K_m value were found with the supports containing predominantly micropores. The extent of the changes decreased with increasing pore size of the support. The catalytic behaviour of endopolygalacturonase bound on the supports with large pores was quite analogous to that of the free enzymes.     

Structure of xylogalacturonan fragments from watermelon cell-wall pectin. Endopolygalacturonase can accommodate a xylosyl residue on the galacturonic acid just following the hydrolysis site

A combination of xylogalacturonan (XGA), homogalacturonan, and rhamnogalacturonan was extracted from watermelon fruit cell walls with 0.1 M NaOH. In contrast to the resistance of xylogalacturonans from most other sources to endopolygalacturonase (EPG), about 50% of the extracted XGA could be converted into oligosaccharides by EPG digestion with a commercial EPG from Megazyme International. The oligosaccharides were fractionated by ion-exchange chromatography, and their structures were investigated by mass spectrometry and NMR spectroscopy. The smallest oligosaccharide was beta-D-Xylp-(1-->3)-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)-GalAp. The most abundant was beta-D-Xylp-(1-->3)-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)(beta-D-Xylp-(1-->3)-alpha-D-GalAp-(1-->4))-alpha-D-GalAp-(1-->4)-alpha-D-GalAp-(1-->4)-GalAp. Given that the nonreducing ends of the oligosaccharides often were xylosylated GalA residues, and that fungal EPG digests homogalacturonans between the third and fourth GalA bound to the enzyme, it appears that EPG can accommodate a xylosylated GalA in the site that binds the fourth GalA. Since all of the oligosaccharides characterized had three unsubstituted GalA residues at their reducing ends, the enzyme appears not to accommodate xylosylated residues in the first three sugar-binding sites. Thus, XGA regions with fewer than three unsubstituted residues between branch points will be resistant to EPG. The EPG-susceptible XGA was not recovered from cell walls prepared using phosphate buffer for the homogenization of the watermelon tissue, probably because it was degraded by endogenous watermelon EPG and lost during isolation of the walls. Use of Tris-buffered phenol during wall isolation to prevent enzyme action caused some amidation of GalA residues with Tris.     

Effects of monovalent cations on red cell shape and size

Human erythrocytes were incubated in isotonic solutions of different monovalent cations. The apparent size of the red cells measured on scanning electron microscopic pictures decreases in the order Li⁺>Na⁺=K⁺>Rb⁺. These differences in size are abolished after pretreatment with trypsin, which removes a large part of the charges associated with membrane glycoproteins. Shape alterations are also observed. Normal biconcave shapes are visible after Na⁺ or K⁺ incubation, whereas Li⁺ leads to flabby, flattened cells with a certain tendency to crenation, and Rb⁺ causes more pronounced biconcavity with a certain tendency to cupping. The overall effects of pretreatment with trypsin are similar to those of Li⁺. Our results provide evidence that the electrostatic repulsion of glycoproteins and other charged membrane components may play an essential role in maintaining red cell shape.     

高精度遥感影像下农牧交错带小流域景观特征的粒度效应

在GIS和RS技术支持下,以农牧交错带六道沟小流域2010年的WV-1高精度遥感影像为基础,编制了小流域景观类型图,选取经典景观指数,在类型和整体景观的水平上,探讨了农牧交错带小流域景观格局指数随粒度变化的基本规律,并分析了各景观格局指数间的相关性。结果表明：在1-50 m粒度范围内,农牧交错带六道沟小流域景观格局指数的“临界粒度”现象明显,总体而言,在0.5 m分辨率下六道沟小流域的景观格局指数的“临界粒度”为10 m,适宜计算的粒度范围为5-10 m,所以在利用高精度影像对小流域景观进行预测、对比和评价等研究时,需注意粒度的影响并进行一定的粒度转换。农牧交错带小流域景观形态具有分形特征,各类景观斑块的分维数对粒度变化的响应不同,分维数随粒度的增大呈非线性下降趋势,表明景观类型边界趋于简单化。相关性分析一方面定量反映了所选景观指数受粒度变化影响的相关性程度,另一方面可为后续农牧交错带小流域因“退耕还林（草）”工程引起的景观格局变化研究提供参考。     

Physico-chemical Approach of the Amylolytic Action Pattern of a Thermostable Amylopullulanase

This paper describes the amylolytic action pattern of Thermococcus hydrothermalis recombinant amylopullulanase (Th-ApuΔ2) [E.C 3.2.1.41]. A comparison was made between amylose hydrolysis catalyzed by this enzyme and by two other amylolytic enzymes: α-amylase [E.C 3.2.1.1] (from Aspergillus oryzae) and glucoamylase [E.C. 3.2.1.3] (from Aspergillus niger), respectively taken as models for “endo” and “exo” catalytic patterns. Different independent physico-chemical methods were used to characterize the hydrolysis products obtained with the studied enzymes. Viscosity results were correlated to reducing sugars analysis to show a similarity between glucoamylase [E.C. 3.2.1.3] and Th-ApuΔ2 [E.C 3.2.1.41] behavior. On the other hand, whereas α-amylase [E.C 3.2.1.1] action rapidly decreased the viscosity of medium, glucoamylase and Th-ApuΔ2 hydrolysates have only shown a negligible reduction in viscosity. Glass transition temperatures of glucoamylase and Th-ApuΔ2 hydrolysates were found comparable (225–226°C) and significantly different from that of α-amylase (197°C). Thin-layer chromatographic analysis of hydrolysates mainly revealed the presence of glucose in the case of glucoamylase and Th-ApuΔ2 activities and in addition to glucose the Th-ApuΔ2 chromatograms have shown oligosaccharides with polymerization degree ranging from 2 to 7. These results incite us to conclude that Th-ApuΔ2 has a dual “endo” and “exo” catalytic action pattern. Analysis of the Fourier transform infrared (FTIR) results shows a comparable general aspect for all spectra. The presence of more numerous differentiated and intense peaks in the spectrum of Th-ApuΔ2 hydrolysate reveals the presence of short-chain oligosaccharides. These results confirm thin-layer chromatography results and support a dual action pattern.     

海枣曲霉木聚糖酶降解寡聚木糖的特性

利用滤纸层析或ＡｃｒｙｌｅｘＰ－２凝胶过滤从落叶松木聚糖硫酸水解液中分离纯化子木二糖至木五糖。采用硅胶薄层层析分析底物和产物的方法研究了海枣霉木聚糖酶降解寡聚木糖的特点。此酶作用于寡糖的最适ＰＨ为５．０,终产物为Ｘ和Ｘ２。酶作用于Ｘ３、Ｘ４及Ｘ５的相对初速度分别为１、３４和４００,Ｘ２几乎不被酶解,推断该酶的底物结合部位至少具有５个亚位点,在高底物浓度,低酶量,远离最适ＰＨ以及在反应初期都能检测到     

遥感影像空间分辨率及粒度变化对城市景观格局分析的影响

尺度是景观生态学和遥感领域的重要问题,已有研究主要考虑景观的粒度效应,很少涉及遥感影像空间分辨率对景观格局,尤其是对城市景观格局的影响.基于2000年和2002年分别由ETM 和IRS-PAN影像解译得到的土地利用图,从景观和类型两个层次分析了不同粒度下上海市一城市化样带的景观格局.结果表明,城市景观有明显的尺度效应,空间分辨率和粒度变化都会影响城市景观格局,而道路等线性廊道对尺度变化的敏感则是造成这一影响的主要原因.斑块密度、边界密度、平均斑块分维度、景观聚集度和最大斑块指数的粒度效应比较明显,而景观比例、Shannon多样性指数对粒度变化并不敏感.高分辨率影像适用于城市景观格局,尤其是破碎度的分析,其用于分析的合适粒度是5～10m.     

情绪调节时间知觉的作用方式及认知神经机制

人类的时间知觉会受到情绪的调节发生主观扭曲,这种调节可以通过情绪的体验与预期来实现.本文区分了体验性情绪和预期性情绪调节时间知觉的作用方式和认知机制,基于标量计时理论,提出了在不同加工阶段情绪调节时间知觉的认知理论模型,并梳理了情绪调节时间知觉的神经生理学基础和脑机制方面的证据.未来研究需更关注预期性情绪对时间知觉的调节作用,考察注意、唤醒和效价等因素的交互影响,并进一步探究情绪调节时间知觉的神经机制.     

各种因子对固定化烟草核酮糖1,5-二磷酸羧化酶/加氧酶解离作用的影响

pH,温度、离子强度及效应剂等对固定化烟草RuBP羧化酶在2.5mol/L尿素处理下的解离作用有各种不同的影响。在pH6.0时,仅小亚基从大亚基核(L_8)解离,当pH为中性偏碱时,大亚基核也解离。低温和低离子强度均促进酶的解离,而温度和离子强度对大亚基之间的解离的影响显著大于对大、小亚基之间的影响。这表明酶的亚基之间存在着不同的极性和疏水作用,而大亚基之间的疏水作用比大、小亚基之间的强。6-PG对大、小亚基之间解离的抑制作用表明大亚基上的催化位置与小亚基之间有一定的密切关系。     

Effects of dietary tin and aluminum on selenium utilization by adult males

The main purpose of these studies was to determine whether the amounts of tin and aluminum that can enter foods during processing and storage are sufficient to affect the utilization of selenium by human subjects. Two 40-day balance studies were conducted. The eight adult males who participated in the first study lost significantly more selenium in their feces when fed a test diet containing 50 mg tin daily than when fed the control diet containing 0.1 mg tin daily. During the first study subjects tended to excrete less selenium in the urine when fed the test diet rather than the control diet. In the second study, the dietary treatments (5 and 125 mg aluminum daily) had no effect on the excretion and apparent retention of selenium by eight adult males.     

Effects of male genetic contribution and paternal investment to egg and hatchling size in the cricket,Gryllus firmus

Egg provisions represent the complete energy supply of oviparous organisms from fertilization until hatching, and egg size is generally correlated with initial offspring size and a suite of other early fitness related traits. Since egg size is determined by the mother, little attention has been given to potential sources of paternal effects on either egg size or initial offspring size. This study considers two processes by which the sire can affect the egg size and/or initial body size of his offspring, in the multiply mated cricket, Gryllus firmus. The first is a paternal genetic effect, whereby differences in offspring genotype result in differences in the efficiency of metabolising available resources. The second is a paternal environmental effect, whereby the quality or size of paternal investment varies among male phenotypes and this is correlated with the size of eggs the females subsequently produce. Using a one-locus two-allele recessive mutation for pale eye colour as a marker, a mating experiment was designed which enabled the discrimination between eggs fertilized by two males mated simultaneously to a single female. The results of this experiment suggest that sire effects on egg and initial body size occur through both processes. Eggs fertilised by the two males were significantly different at day ten of development, suggesting that the genetic contribution of the sire is affecting embryonic body size. Further, a negative correlation was found between the head size of the pale eyed male and the size of all the eggs that the female laid, suggesting an effect of male size of the amount of nutrients the female receives from her mates. The results of this study suggest that paternal effects may be both more common and more profound than previously thought, and that studies examining early fitness traits that are correlated to egg size or initial body size, in oviparous animals, should consider the possibility and importance of the paternal contribution.     

脱乙酰壳聚糖固定化宇佐美曲霉木聚糖酶及固定化酶的性质和应用(英文)

研究壳聚糖吸附和戊二醛交联对木聚糖酶固定化条件 .将酶液加入到经醋酸溶液处理过的脱乙酰壳聚糖的pH 4 8的悬液中 ,加入浓度为 0 3%～ 0 4 %的戊二醛溶液 ,室温下 ,8h后得到固定化酶 .固定化酶的半失活温度比游离酶高 ,由 5 1℃升至 71℃ ,Km 值由游离酶的 1 2mg ml增加到1 5mg ml ,最适反应温度也由 5 5℃增加到 71℃ ,而最适反应pH由 4 6下降到 3 8.该固定化木聚糖酶可用于制造低聚木糖 .经过 10次连续应用实验后 ,该固定化酶的活力保持 81%     

干湿交替和冻融作用对土壤肥力和生态环境的影响

干湿交替和冻融作用对土壤肥力和生态环境的影响朴河春,刘广深,洪业汤（中国科学院地球化学研究所,贵阳５５０００２）ＥｆｆｅｃｔｓｏｆＡｌｔｅｒｎａｔｉｖｅＤｒｙｉｎｇ－ＲｅｗｅｔｔｉｎｇａｎｄＦｒｅｅｚｉｎｇ－ＴｈａｗｉｎｇｏｎｓｏｉｌＦｅｒｔｉｌｉｔ...     

Effects of ovarian hormones on cell membranes in the rat uterus

Histochemical techniques, including radioisotope histochemistry, have been used to investigate the nature of the surface carbohydrates at the apex of cells of the luminal epithelium of the rat uterus under various hormonal conditions. Binding of ruthenium red was quantitatively similar in ovariectomized rats without further treatment and in those given three daily injections of progesterone. Ruthenium red binding was significantly lower after 3 days treatment with estradiol, and also after 3 days treatment with progesterone with an additional dose of estradiol on day 3, a regime known to produce an epithelium receptive to the implanting blastocyst. Binding of concanavalin A (con A), whether studied by electron microscope histochemistry after incubation of tissue with con A-horseradish peroxidase, or by light microscope autoradiography after incubation with³H-con A, was not statistically different in any of the four groups of rats. The results with ruthenium red show a reduction in net negative charge of the carbohydrates on the apical cell membrane in conditions permitting implantation: this change is not due to variations in the amounts of the neutral carbohydrates, mannose and glucose, as demonstrated by con A.     

Effects of Glucocorticoids and Epinephrine on the Modulatory Action of Purines in the Frog Neuromuscular Junction

The effect of corticoids (hydrocortisone and dexamethasone) and epinephrine on the presynaptic action of purines was studied at the neuromuscular junction of the frog under two-electrode voltage-clamp conditions. Daily administration of hydrocortisone/dexamethasone (100 mg/kg into the lymphatic system) increased initially and later depressed the amplitude of multiquantum end-plate currents evoked by motor nerve stimulation. An initial facilitatory phase of the hormone action was accompanied by removal of the presynaptic action of ATP (for hydrocortisone only). Within the later phase (2 weeks of hydrocortisone administration), the inhibitory action of ATP was restored once again. The counteraction of ATP effect was reproduced under superfusion of the isolated muscle by a physiological solution containing hydrocortisone (not dexamethasone), indicating the nongenomic nature of the action of the hormone on presynaptic P2 receptors. This proved to be true in experiments on animals, which were stressed 30 min prior to the beginning of the experiment by electrical stimulation in a special cage. Independently of acute or chronic administration of hydrocortisone, the presynaptic action of another purine, adenosine, was preserved. Epinephrine only partially abolished the inhibitory effect of purines, which is indicative of the difference in the paths of incorporation of the biological effects of these agents. We suggest that prevention of the inhibitory action of ATP might be one of the components of a facilitatory acute stress reaction, while such an inhibitory feedback action is missing under chronic stress conditions.     

Effect of mother plant age on germination and size of seeds and seedlings in the perennial sedge Carex secalina (Cyperaceae)

The performance of seeds and seedlings in relation to the age of the mother plant was studied in Carex secalina. Seeds of this sedge can differ substantially in size. We planted 100 C. secalina individuals from three populations in a common garden and followed them for four years. We found that mean seed mass varied with plant age, but the pattern of variation was population-specific, with only one population showing significant reduction in seed mass with age. Similarly, germination frequency changed with age differently in different populations. The relationship between the age of the mother plant and the height of emerged seedlings did not differ between populations. In spite of the fact that plant size and mean seed mass exhibited similar patterns of variation within populations, there was no correlation between these two variables at the level of individuals. This means that the size of C. secalina tufts does not determine how big the seeds will be. Moreover, there was no relationship between mean seed mass and the height of seedlings. Presumably, factors intrinsic to each plant determine the production of either small or large seeds in a population-specific way.     

富营养化与污染物间的相互作用及其生态效应

1　引　言进入 90年代 ,为了改善水环境条件 ,越来越多的国家认识到必须减少养分、稳定的有机物和金属元素的输入。富营养化和持续污染物 (Ｃｈｒｏｎｉｃｐｏｌｌｕｔａｎｔｓ)是当前全球水生态系统的两个主要问题[1 ,2 ]。尽管对富营养化和污染物已有很多研究 ,但很少调查二者之间的相互关系。有证据表明两者之间可能存在相互作用过程[5～ 7],但在自然的水生态系统中其作用的大小和关系尚不清楚。滇池是我国典型的遭受富营养化和重金属污染双重胁迫的高原湖泊 ,本研究以滇池富营养化和重金属污染为背景 ,通过室内模拟 ,初步探索富营养化和…     

Immobilized inulinase: a new horizon of paramount importance driving the production of sweetener and prebiotics

In recent times, inulinase has emerged as one the most prominent and industrially upcoming enzymes applied to meet the ever increasing demand of d-fructose and fructooligosaccharides (FOS) as sweetener and prebiotics in the food and pharmaceutical industry, respectively. This review deals with types of inulinase and the attempts made to modify it for better thermal stability and shelf life. The ease of immobilization of inulinase has led us to the path of experimenting with different methods of enzyme immobilization since 1979. Several modes of immobilization ranging from simple cross-linking of enzymes onto a polymer support to nanoparticles have been applied over the years. The approach and concept of this review provide a yet unexplored focus on pioneering advances for the development of white biotechnology, for instance production of immobilized inulinase-based reusable biocatalysts and bioreactors designed for their use and for the continuous production of fructose and FOS.