由人发制备胱氨酸的工艺研究

实验对胱氨酸的生产流程作了进一步的探讨 ,讨论了原料的用量、酸度、水解时间、水解温度及收得率的最佳条件 ,在提高生产工艺的同时 ,降低生产成本。     

用氧化亚铜从人发水解液中沉淀胱氨酸的研究

用氧化亚铜沉淀毛发水解液中的胱氨酸 ,其沉淀率最高可达 90 %左右。沉淀剂的用量 ,溶液的pH值及沉淀时水用量对沉淀效率有影响。通过实验确定了氧化亚铜沉淀毛发水解液中胱氨酸的最佳操作条件。     

从生产半胱氨酸的废母液中回收胱氨酸的工艺研究

研究了一种从生产半胱氨酸的废母液中回收胱氨酸的工艺,介绍了工艺过程并讨论了其主要原理及影响因素。该方法工艺简单,操作方便,对设备的要求低,而回收率、产品含量均较高,是一种回收利用氨基酸、减少环境污染的好方法。     

从人发中连续提取亮氨酸和胱氨酸工艺初探

介绍了一种从人发中连续提取亮氨酸和胱氨酸的新工艺。人发用盐酸水解后 ,将水解液减压赶酸 ,再直接加入邻二甲苯 - 4-磺酸沉淀亮氨酸 ,所得沉淀经氨解及后续的精制过程可得亮氨酸精品 ,沉淀亮氨酸后所得的母液按传统的工艺用液氨和得胱氨酸粗品 ,再经一次精制中和可得胱氨酸精品。亮氨酸和胱氨酸的收率分别可达 4 .9%和 7.8% ,产品质量符合日本味之素标准     

猪毛水解液中胱氨酸含量的测定

<正> 国内生产胱氨酸一般都采用猪毛或人发酸水解来提取的。在水解过程中怎样较快而准确地确定出料时间,这是生产过程中的一个关键问题,以前,我厂采用做小样的方法,就是在水解过程中,每隔半小时取一定量的水解液,做出胱氨酸的精品,然后根据在不同时间里胱氨酸精品的量绘成水解曲线。水解曲线的高峰点为出料时间。但这一方法存在着很大的毛病,因为用这一方法,在提取过程中的损失大,最后得到胱氨酸精品的量,不能完全表示所取     

不同来源毛发酸水解液中胱氨酸含量的差异

<正> 以毛发为原料酸水解生产 L-胱氨酸已在我国许多单位进行,如何提高 L-胱氨酸的收得率,降低成本是生产中关键问题。L-胱氨酸的收得率与水解条件,中间提取条件是密切相关的,但在水解条件相同的情况下,不同来源的毛发酸水解液中 L-胱氨酸含量有无差别,对 L-胱氨酸收率有什么影响呢?我们1976年在广东省东莞县拷胶厂,对不同来源毛发酸水解液中 L-胱氨酸含量和产量进行了分析和试验。     

黄姜皂素母液回收皂素工艺研究

介绍从黄姜生产皂素的废母液中回收皂素的工艺研究。采用清洁剂除油去杂 ,添加填充剂加溶剂萃取等措施 ,可从 1 0 0g废母液中回收得到 2g以上的皂素。     

人琼脂糖电泳凝胶中回收DNA的几种简便方法

介绍两类从普通琼脂糖电泳凝胶中回收ＤＮＡ的简便,快捷,高效且廉价的方法,第一类为电泳洗脱法,方法ａ．利用１．５ｍＬ微量离心管,１ｍＬ吸头,尼龙网膜和透析膜做成的一个小装置,快速有效回ＤＮＡ,最终回收率为７０％左右,方法ｂ：不用ＤＥＡＥ－纤维素膜,而用透析膜在凝胶中作出横隔挡在ＤＮＡ条带前,最终回收率为５０％左右,第二类为冰冻融解法,最终回收率也在５０％左右,如果联合使用冰冻融解法和电泳洗脱法,回收     

胱氨酸制备中自动化技术的应用

指出了目前胱氨酸制备中存在难点，并提出了解决办法，即自动化技术的应用。     

D-半胱氨酸盐酸盐制备研究

D-半胱氨酸盐是手性药物,主要是第三代头孢抗生素药物—头孢米诺钠的重要中间体。本文介绍了D-半胱氨酸盐酸盐的研制。采用L-半胱氨酸盐酸盐为出发原料,经消旋、沉淀异构体、结晶分离、提纯的方法,制成达到日本味之素公司1997年公布的产品质量指标的D-半胱氨酸盐酸盐。     

Recovery process of lactic acid using two distillation columns

Lactic acid is of interest as the raw materials of polylactide that is a biodegradable polymer. For an effective purification of lactic acid, batch distillation with the simultaneous reactions was used. Two Oldershaw columns and reboilers were used for fractionation of methanol and reactions. Esterification reaction of lactic acid with methanol produced methyl lactate and water. The products of the esterification reaction, methyl lactate and water were transported to the reboiler of the hydrolysis part. In hydrolysis part, reaction of methyl lactate and water reproduced lactic acid and methanol. Methanol produced in the hydrolysis part and unreacted methanol in the esterification part were separated by distillation and recycled to the reboiler of the esterification part so that the esterification reaction would be stimulated. Thus, pure lactic acid solution remained in the reboiler of the hydrolysis part. The effect of the number of stages in column on the recovery yield was also investigated. In the operation with columns the recovery yield of lactic acid was improved. It is due to the fact that the columns improved the fractionation of components and stimulated the reactions in two parts.     

Optimization of the hydrochloric acid concentration used for trifluoroacetate removal from synthetic peptides.

Trifluoroacetate (CF3COO-, or TFA) is almost always present in commercially synthesized peptides. Unfortunately, it has a strong infrared (IR) absorption band at 1673 cm-1, significantly overlapping or even completely obscuring the amide I band of a peptide. In such cases TFA must be removed from the solution in order to be able to use IR absorption spectroscopy for peptide secondary structure determination. The most convenient and widely used procedure involves peptide lyophilization from a 0.1 M HCl solution. In our studies of the tryptophan-rich antimicrobial peptide indolicidin, we have found that caution should be taken when using this HCl concentration. High HCl concentrations (>10 mM in unbuffered solutions and > 50 mM in buffered solutions) may modify the peptide structure and reduce its thermal stability, thereby interfering with subsequent structural investigations of the peptide. Our results indicate that HCl concentrations between 2 and 10 mM are adequate to remove essentially all TFA impurities without any modification of the peptide secondary structure.     

Structure of Lily Glucomannan Deduced from Enzymic Hydrolyzate

A thermostable acetylxylan esterase gene, TTE0866, which catalyzes the deacetylation of cellulose acetate, was cloned from the genome of Caldanaerobacter subterraneus subsp. tengcongensis. The pH and temperature optima were 8.0 and 60 °C. The esterase was inhibited by phenylmethylsulfonyl fluoride. A mixture of the esterase and cellulolytic enzymes efficiently degraded insoluble cellulose acetate with a higher degree of substitution.     

Recovery of protein from reverse micelles through gas hydrate formation

The recovery of cytochrome c and ribonuclease A from di-2-ethylhexyl sodium sulfosuccinate (AOT) reverse micelles have been examined by the gas hydrate formation. The recovery of cytochrome c depended upon the kind of gas and the water content (w0=[H₂O]/[AOT]) of reverse micellar solution containing cytochrome c prepared. Recoveries of cytochrome c and ribonuclease A were more than 80%, when 1,1,1,2-tetrafluoroethane (TFE) was used as a hydrating gas. The activity of cytochrome c recovered from reverse micelles was maintained perfectly.     

Recovery of fertile plants from isolated,cultured maize shoot apices

Maize shoot apices (1 to 2mm size) from two sources were used to recover normal plantlets. The first explant source included shoot apices from the embryonic axis of immature embryos, 12–14 days post pollination in the glasshouse (spring) or 15–20 days post pollination in the summer nursery. In most explants, the shoot apical meristem was surrounded by a coleoptile primordium which was removed before culture. The second explant source included shoot apices from the plumules of 72 h imbibed mature kernels. The coleoptile and all other leaf layers (leaf-1 to leaf-3 or 4) of the plumule were removed before culture to expose the apical meristem. Among the genotypes studied, a recovery of 43% (Mo17) to 100% (Oh43) of plantlets was achieved from shoot apices from immature embryo plumules cultured in MS medium. Recovery of 80% of Oh43 plantlets in MS medium and 40% of A188 plantlets from apices of plumules of imbibed (72 h) seeds in MS medium containing 2,4-dichlorophenoxyacetic acid was recorded. The plantlets derived from both explant sources grew normally and produced viable seeds upon pollination.     

Cysteine and Cystine Transport at the Blood-Brain Barrier

Abstract: The nature of cysteine and cystine uptake from the cerebral capillary lumen was studied in the rat using the carotid injection technique. [³⁵S]-Cysteine uptake was readily inhibited by the synthetic amino acid 2-amino-bicyclo(2,2,1)heptane-2-carboxylic acid (BCH), the defining substrate for the leucine-preferring (L) system in the Ehrlich ascites cell. The addition of non-radioactive alanine or serine, representatives of the alanine, serine, and cysteine-preferring (ASC) system, produced no significant decrease in the uptake of cysteine after cysteine transport by the L system was blocked with BCH. This indicated that the major component of cysteine's transport from the brain capillary lumen was by the L system with no detectable uptake of cysteine by the ASC system. No carrier-mediated transport of cystine, the disulfide form of the amino acid, was detected, nor was there any inhibition by cystine of the transport of the neutral amino acid methionine or the basic amino acid arginine. These results suggest that the ASC system, if present, is not quantitatively important for the transport of neutral amino acids from the brain capillary lumen.     

Recovery from acidification in boreal lakes inferred from macroinvertebrates and subfossil chironomids

Acidification of waters and soils caused by emissions and the long-range transport of air pollutants has been a serious worldwide problem during the last decades. The extent of the acidification problem in Finnish acid-sensitive forest lakes was examined in the Acidification Research Project (HAPRO) in the mid-1980s. The recent decline in the emissions of air pollutants has resulted in the chemical recovery of watersheds in many regions, and the present work on the recovery processes in acidified Finnish headwater lakes (REPRO) was launched to examine whether the chemical recovery has already been accompanied by biological recovery. The patterns of recovery were studied by re-sampling littoral macrozoobenthos in a subset of the previously sampled HAPRO lakes. Paleolimnological samples were taken in order to assess the possible dependence of lacustrine chironomid communities on the changing degree of acidification. Acid sensitive and moderately acid sensitive benthic species revealed slight recovery in the formerly most acidic (pH 5.5) but recently recovered lakes. The most significant factors affecting the response of benthic communities were increased mean lake pH and decreased labile aluminium concentration. Paleolimnological chironomid analysis revealed a slight response along the pH gradient, but also significant structural similarity between the present and pristine chironomid assemblages. This implies that no major changes in chironomid communities of these acidic lakes have occurred during the past centuries. The alternative future trends and threats to biological recovery in small headwater lakes are discussed.     

Recovery from the most profound mass extinction of all time

The end-Permian mass extinction, 251 million years (Myr) ago, was the most devastating ecological event of all time, and it was exacerbated by two earlier events at the beginning and end of the Guadalupian, 270 and 260 Myr ago. Ecosystems were destroyed worldwide, communities were restructured and organisms were left struggling to recover. Disaster taxa, such as Lystrosaurus, insinuated themselves into almost every corner of the sparsely populated landscape in the earliest Triassic, and a quick taxonomic recovery apparently occurred on a global scale. However, close study of ecosystem evolution shows that true ecological recovery was slower. After the end-Guadalupian event, faunas began rebuilding complex trophic structures and refilling guilds, but were hit again by the end-Permian event. Taxonomic diversity at the alpha (community) level did not recover to pre-extinction levels; it reached only a low plateau after each pulse and continued low into the Late Triassic. Our data showed that though there was an initial rise in cosmopolitanism after the extinction pulses, large drops subsequently occurred and, counter-intuitively, a surprisingly low level of cosmopolitanism was sustained through the Early and Middle Triassic.