Catalytic residues of gamma delta resolvase act in cis.

The resolvase protein of the gamma delta transposon is a site-specific recombinase that acts by a concerted break-and-join mechanism. To analyse the role of individual resolvase subunits in DNA strand cleavage, we have directed the binding of catalytic mutants to specific recombination crossover sites or half-sites. Our results demonstrate that the resolvase subunit bound at the half-site proximal to each scissile phosphodiester bond provides the Ser10 nucleophile and Arg8, Arg68 and Arg71 residues essential for cleavage and covalent attachment to the DNA. Several other residues near the presumptive active site are also shown to act in cis. Double-strand cleavage at one crossover site can proceed independently of cleavage at the other site, although interactions between the resolvase dimers bound at the two crossover sites remain essential. An appropriately oriented heterodimer of active and inactive protomers can in most cases mediate either a 'top' or 'bottom' single-strand cleavage, suggesting that there is no obligatory order of strand cleavages. Top-strand cleavage is associated with the topoisomerase I activity of resolvase, suggesting that a functional asymmetry may be imposed on the crossover site by the structure of the active synapse.     

Maternal and child health in China.

China has made great progress in improving the health of women and children over the past two generations. The success has been attributed to improved living standards, public health measures, and good access to health services. Although overall infant and maternal mortality rates are relatively low there are large differences in patterns of mortality between urban and rural areas. The Chinese have developed a hierarchical network of maternal and child health services, with each level taking a supervisory and teaching role for the level below it. Maternal and child health in China came to international attention in 1995 with the promulgation of the maternal and child health law. In China this was seen as a means of prioritising resources and improving the quality of services, but in the West it was widely described as a law on eugenics.     

外消旋薄荷醇对映选择性酶促酯化中酸酐与羧酸的比较研究

利用脂肪酶在有机溶剂中催化对映选择性酯化反应对外消旋薄荷醇进行了有效的光学拆分。对分别使用酸酐和相应的游离羧酸作酰基给体时的反应性能进行了比较。发现酸酐的反应性远高于对应的游离羧酸,但在酶的催化作用下酸酐易水解成为游离羧酸;在微水系统中使用过高浓度的酸酐会导致酶缺水而失活,同时会促进手性醇的非选择性酯化,从而降低产物的光学纯度。然而,在连续流加丙酸酐的半批式反应系统中,所有这些缺点均可有效地克服。与使用游离丙酸的批式反应系统相比,ｄｌ-薄荷醇的反应时间缩短了一半,酶的稳定性大幅度提高,而产物ｌ薄荷醇酯的光学纯度不相上下（＞９８％ｅ）。     

棘豆属刺垫棘豆亚属(豆科)的订正

1971年,N.Ulzijkhutag根据采自阿拉善戈壁(=Bordzon-Go-bi)的标本(1970-07-29,V.I.Grubov,N.Ulzijkhutag et G.Tserendalzhid,无号)发表新种Oxytrops grubovii,并以此建立新组Oxytropis subgen.Traganthoxytropis sect.Monan-thos;1987年,G.P.Yakovlev将O.grubovii归入海绵豆属Spongiocarpella;1988年,张振万同意N.Ulzijkhutag的意见,并根据刺垫棘豆之龙骨瓣无喙等特征将Ulzijkhutag的刺     

长臂生物素对硝基苯酯的合成

以羰基二咪唑为催化剂,生物素与6－氨基己酸甲酯反应生成生物素－6－氨基己酸甲酯,该化合物通过酸碱萃取与原料分离,皂化后生成生物素氨基己酸．生物素氨基己酸在吡啶存在下与三氟乙酸对硝基苯酯进行转酯反应即得生物素对硝基苯酯．最后经光谱、色谱及核酸杂交证实了长臂生物素对硝基苯酯的化学结构和生物学活性．     

Optimization of the culture medium composition for the antibody response of mouse spleen cells

Summary The Mishell-Dutton culture system for in vitro primary antibody response of mouse spleen cells was used to optimize the amino acid composition of RPMI 1640 media. Each of the 20 amino acids was tested over a broad range of concentrations always leaving the remaining 19 amino acids unaltered (i.e. at the formula recommended concentration). In several instances, higher plaque-forming cell responses were obtained with an amino acid concentration that was either higher or lower than that recommended: (a) the optimum concentration for valine, glutamine, and lysine lies considerably above the recommended one, (b) the optimum concentration for leucine as well as for several other amino acids lies below the recommended concentration, and (c) the optimum concentration for arginine corresponds exactly to the recommended concentration. The second round of optimization, i.e. combining of two conditions that individually yielded an improved response often caused a decrease of response. The possibility is discussed that for an optimal response a ratio of two or several amino acids rather than the absolute concentration of any one amino acid is of importance. The Basel Institute for Immunology was founded and is supported by F. Hoffman-La Roche & Co., Ltd.     

Mechanisms of increasing the intensity of ultraviolet fluorescence of irradiated cells

As shown on the in vitro irradiated Ehrlich ascites tumor cells the increase in the intensity of ultraviolet fluorescence (UVF) of the exposed cells occurs only in such incubation conditions when an increase in the tryptophan content of irradiated cells becomes possible. The increase in the UVF intensity and in the tryptophan content are quantitatively identical. It is concluded that the increase in the content of the fluorescing substance, tryptophan, in the irradiated cells is the cause of the increase in the UVF intensity.     

去传入神经引起大鼠延髓后角P物质、胆囊收缩素、神经降压肽、亮-脑啡肽变化机制的探讨

去传入神经可引起后角一些肽类变化和含肽的大颗粒小泡以胞吐的形式在非突触部位释放。为了探讨这一作用机制,本文切除一侧刚髭部皮肤,应用免疫组化方法观察并定量分析术后不同时间延髓后角浅层SP、CCK、NT、L-ENK阳性纤维的变化及利多卡因对后角浅层SP的影响。结果显示:术后1小时,延髓后角浅层SP损伤侧较对照侧升高,第3～7天未见显著性减少或升高,第8天开始脱失(P<0.05),第14天脱失更甚,第30天开始恢复,第90～120天基本恢复。CCK变化基本同SP。NT、L-ENK术后不同时间(7～120天),两侧比较未见显著性差异(P>0.05)。应用和多卡因后,后角浅层SP损伤侧较对照侧未见明显减少(P>0.05)。根据上述结果,本文推测:去传入神经导致延髓后角浅层神经肽的变化,可能是神经损伤区(神经瘤或再生芽)产生异常电活动,引起延髓后角浅层神经肽释放的结果。     

用于聚合酶链式反应(PCR)引物设计的计算机程序

 本文报道了两个用于PCR引物设计的计算机程序PCRDESN和PCRDESNA。PCRDESN程序主要从以下4个方面评价用户自己设计的一对引物的质量:(1)引物内的碱基反向重复或发夹结构,(2)两个引物之间的碱基互补配对,(3)两个引物之间的同源性,(4)引物的碱基组成及特点和T_m值计算。通过用多例文献发表的及本院有关实验室提供的引物对序列的验证,确定了程序的运算参数,证明该程序能较好地检验引物对的质量和解释某些PCR实验失败的原因。PCRDESNA程序采用逐级优化的方法和比PCRDESN所选用的更严紧的引物选择参数对用户提供的核酸序列进行快速检索,以确定所有可能的和合适的引物对。