黔西县野生刺梨果实品质调查研究

[目的]调查黔西县野生刺梨资源,为该资源的开发利用以及黔西县特色经果林产业发展提供参考。[方法]以不同株系14个野生刺梨果实为材料,测定野生刺梨果实外在品质(单果重、果形指数)和内在品质(可溶性固形物含量、可滴定酸含量、可溶性总糖含量、VC含量、固酸比、糖酸比),并对其果实品质进行分析和讨论。[结果]株系QX-11和QX-7果实外观品质和经济价值最好;QX-7可溶性固形物含量最高;QX-2可滴定酸含量最高,QX-10最低;QX-13可溶性总糖含量最高,QX-10最低;QX-1、QX-6、QX-3VC含量较高;QX-9固酸比最大;QX-13糖酸比较高。[结论]不同地区之间气候、土质等方面的差异可能导致果实品质出现差异。     

Protein catalysis of the retinal subpicosecond photoisomerization in the primary process of bacteriorhodopsin photosynthesis

The rate of retinal photoisomerization in wild-type bacteriorhodopsin (wt bR) is compared with that in a number of mutants in which a positively charged (Arg(82)), a negatively charged (Asp(85) or Asp(212)), or neutral hydrogen bonding (Asp(115) or Tyr(185)) amino acid residue known to be functionally important within the retinal cavity is replaced by a neutral, non-hydrogen bonding one. Only the replacements of the charged residues reduced the photoisomerization rate of the 13-cis and all-trans isomers present in these mutants by factors of approximately 1/4 and approximately 1/20, respectively. Retinal photo- and thermal isomerization catalysis and selectivity in wt bR by charged residues is discussed in terms of the known protein structure, the valence-bond wave functions of the ground and excited state of the retinal, and the electrostatic stabilization interactions within the retinal cavity.     

丁香油和MS-222对大泷六线鱼幼鱼的麻醉效果

为研究丁香油和MS-222麻醉剂对大泷六线鱼Hexagrammos otakii的麻醉效果,选择体质量为(83.3±7.8)g的大泷六线鱼幼鱼进行试验,根据大泷六线鱼被麻醉和复苏时的行为特征,将整个麻醉过程分为10期,其中麻醉6个时期,复苏4个时期。结果表明:丁香油浓度在50~100 mg/L、MS-222浓度在50~70 mg/L时鱼体均可在3 min内入麻并均可在5 min内复苏;当丁香油浓度≥100 mg/L、MS-222浓度≥70 mg/L时,鱼体在麻醉液中浸浴15 min后部分鱼体出现休克死亡;用丁香油麻醉鱼时,整个麻醉过程中鱼体的呼吸频率呈下降趋势,而用MS-222麻醉鱼时,鱼体在达到4期阶段后呼吸频率明显加快,但仅见鳃盖后缘小幅度张合;鱼体进入深度麻醉以后在空气中暴露时间越长,鱼体复苏所需时间就越长,用丁香油或MS-222麻醉的鱼体可在空气中分别暴露7、5 min。研究表明,丁香油和MS-222均对大泷六线鱼幼鱼有良好的麻醉效果,具有入麻时间短、复苏快的特点,两者均可作为大泷六线鱼理想的麻醉剂。     

棉仁(籽)饼—玉米型肉仔鸡饲粮的研究

用LOHMANN品种肉仔鸡608只进行两次试验,研究了棉仁(籽)饼—玉米型饲粮的应用问题,单因子设计。第一次试验给饲八种试粮:(1)、棉仁饼(CSM)为0,游离棉酚(FG)为0;(2)、CSM为7.5%,FG为111ppm;(3)、(2)+亚铁离子(Fe~(++))111ppm;(4)、CSM为15.0%,FG222ppm;(5)、(4)+F~(++)222ppm;(6)CSM为30％,FG为444ppm;(7)、(6)+Fe(++)444ppm;(8)、(6)+L—赖氨酸(Lys)。第二次试验给饲4种试粮:(9).CSM:大豆饼(SBM)=20:80,粉料;(10).CSM:SBM=50:50,粉料;(11).CBM:SBM=100:0,粉料;(12)、(11),颗粒料。结果:(1)、CSM配比为0—7.5—15.0—30.0%,FG为0—111—222—444ppm时,不经任何脱毒处理,各组49日龄增重(分别为1779.3—1853.8—1861.3—1819.0克)、累积耗料(分别为3978—4217—4208—4158克)、耗料比(分别为2.24—2.27—2.26—2.29)等均未随FG水平提高而产生有规律的明显差异;鸡肝脏残留FG均在安全水平以下;氰化高铁血红蛋白(CNMHb)在正常生理范围以内。(2)、日粮FG为111—222—444ppm时,分别添加111—222—444ppm的Fe~(++)后,对试粮各项生产指标、能量代谢率、蛋白质表现存留率、鸡肝脏残留FG水平、血液CNMHb量均未发生明显影响。(3)、当CSM:SBM分别为20:80、50:50、100:0,构成等蛋白质(%),不等能量浓度(不以饲料脂肪调整)的试粮,试鸡各项生产指标差异均不显著(P>0.05)。(4)、CSM配比为30%时,添加L—Lys,将Lys:精氨酸(Arg.)由1:1.6～1.7调整为1:1.2。结果,Lys:Arg.平衡组(为1:1.2时)试鸡49日龄体重明显较高,但累积耗料量、耗料比,试粮能量代谢率、蛋白质表观存留率差异均不显著(P>0.05)。(5)、用棉仁饼100%地取代豆饼的低能量浓度试粮,经颗粒加工后,其饲料进食量,增重量明显提高。     

Asymmetry of the acetylcholine channel revealed by quaternary anesthetics

Tissue-cultured rat myoballs were examined electrophysiologically with a suction pipette, which was used for voltage clamping and internal perfusion. The lidocaine derivative QX-314 caused a time- and membrane potentia-dependent block of acetylcholine-induced current only when applied from the extracellular membrane surface. The same compounds caused a use-dependent block of the sodium channel only from the intracellular membrane surface. These experiments demonstrate a fundamental asymmetry of the acetylcholine receptor-channel complex.     

麻醉剂MS-222对金鱼体内AKP、CAT和ACP活性的影响

在实验室条件下,采用4个浓度0mg/L、30mg/L、60mg/L和90mg/L,分析了麻醉剂MS-222对金鱼鳃、肝脏和肌肉组织中碱性磷酸酶(AKP)、酸性磷酸酶(ACP)和过氧化氢酶(CAT)活性的影响。试验结果表明:ACP明显出现一个先增后降的趋势,呈抛物线状;在低浓度(≤60mg/L)下,酶活性在各组织中呈现一定的稳定状态,而当麻醉剂浓度升高和麻醉时间增长,酶活性逐渐下降。AKP在低浓度麻醉剂溶液中,酶活性有明显的增加,随着浓度的升高(≥60mg/L)和时间的增长,酶活性呈抑制状态。而在肌肉中这种情况并不明显。CAT在一定阶段(30mg/L～60mg/L)呈现稳定的状态、而后抑制逐渐明显,当麻醉剂MS-222浓度达到一定量(≥60mg/L)以后,对鱼体的刺激就不再增加了,酶活性也相对处于较稳定的状态;当麻醉剂随着时间的增长和浓度的增大时,在鱼体内富集的麻醉剂破坏鱼体内的过氧化氢酶的分子构象,使酶体失去活性。     

麻醉剂MS-222对金鱼体内AKP、CAT和ACP活性的影响

在实验室条件下,采用4个浓度0mg/L、30mg/L、60mg/L和90mg/L,分析了麻醉剂MS-222对金鱼鳃、肝脏和肌肉组织中碱性磷酸酶(AKP)、酸性磷酸酶(ACP)和过氧化氢酶(CAT)活性的影响。试验结果表明:ACP明显出现一个先增后降的趋势,呈抛物线状;在低浓度(≤60mg/L)下,酶活性在各组织中呈现一定的稳定状态,而当麻醉剂浓度升高和麻醉时间增长,酶活性逐渐下降。AKP在低浓度麻醉剂溶液中,酶活性有明显的增加,随着浓度的升高(≥60mg/L)和时间的增长,酶活性呈抑制状态。而在肌肉中这种情况并不明显。CAT在一定阶段(30mg/L～60mg/L)呈现稳定的状态、而后抑制逐渐明显,当麻醉剂MS-222浓度达到一定量(≥60mg/L)以后,对鱼体的刺激就不再增加了,酶活性也相对处于较稳定的状态;当麻醉剂随着时间的增长和浓度的增大时,在鱼体内富集的麻醉剂破坏鱼体内的过氧化氢酶的分子构象,使酶体失去活性。     

Expanding the genetic code of Escherichia coli with phosphoserine

O-Phosphoserine (Sep), the most abundant phosphoamino acid in the eukaryotic phosphoproteome, is not encoded in the genetic code, but synthesized posttranslationally. Here, we present an engineered system for specific cotranslational Sep incorporation (directed by UAG) into any desired position in a protein by an Escherichia coli strain that harbors a Sep-accepting transfer RNA (tRNA(Sep)), its cognate Sep-tRNA synthetase (SepRS), and an engineered EF-Tu (EF-Sep). Expanding the genetic code rested on reengineering EF-Tu to relax its quality-control function and permit Sep-tRNA(Sep) binding. To test our system, we synthesized the activated form of human mitogen-activated ERK activating kinase 1 (MEK1) with either one or two Sep residues cotranslationally inserted in their canonical positions (Sep(218), Sep(222)). This system has general utility in protein engineering, molecular biology, and disease research.     

渔用麻醉剂使用现状和检测技术研究进展

随着水产品交易市场的不断扩大,为了保证水产品品质及鲜活程度,麻醉剂的使用愈发普遍,其中渔用麻醉剂的安全隐患愈发受到关注,而我国在渔用麻醉剂方面的监管却突显不足,对动物体内麻醉剂残留检测技术的研究也比较缺乏。通过研究各国渔用麻醉剂使用现状,提出我国建立相应监管措施的必要性。目前市场上渔用麻醉剂已被普遍使用,包括间氨基苯甲酸乙酯甲烷磺酸盐(MS-222)和丁香酚类化合物,但我国还未建立相应的检测标准或基准方法。对国内外相关检测方法进行总结和比较,为后续方法研究提供理论支持。     

烤烟品种生产对比试验研究

为了鉴定不同烤烟品种对土壤、栽培、烘烤条件的反应和在生产上的利用价值,为生产选用后备品种和配套技术的制定提供科学依据,以K326为对照,对QX-1、GTH-1、云烟97等3个品种进行了对比试验研究。从试验结果看,参试材料的综合指标优于对照材料K326,但还需要反复试验才能定论。     

MS-222、丁香酚对刀鲚幼鱼的麻醉效果

研究了MS-222、丁香酚2种麻醉剂对人工繁养刀鲚(Coilia nasus Schlegel)幼鱼的麻醉效果,探索了2种麻醉剂在安全浓度下麻醉后刀鲚幼鱼暴露在空气中的时间,并运用该2种麻醉剂的适宜剂量对刀鲚幼鱼进行了运输实验。麻醉实验表明:(1)理想MS-222浓度为150 mg/L,理想丁香酚麻醉剂浓度为30 mg/L;(2)经MS-222浓度为150 mg/L深度麻醉后,适宜的暴露在空气中的时间应4 min;经丁香酚浓度为30 mg/L深度麻醉后,适宜的在空气中的时间应5 min;(3)养殖长江刀鲚幼鱼采用30 mg/L MS-222和8 mg/L丁香酚分别麻醉后,其复苏率和48 h内的成活率均达到100%,与各自对照组存在明显差异(P0.05)。     

Effects of buried ionizable amino acids on the reduction potential of recombinant myoglobin

The temperature dependences of the reduction potentials (E degrees') of wild-type human myoglobin (Mb) and three site-directed mutants have been measured by the use of thin-layer spectroelectrochemistry. Residue Val68, which is in van der Waals contact with the heme in Mb, has been replaced by Glu, Asp, and Asn. The changes in E degrees' and the standard entropy (delta S degrees') and enthalpy (delta H degrees') of reduction in the mutant proteins were determined relative to values for wild type; the change in E degrees' at 25 degrees C was about -200 millivolts for the Glu and Asp mutants, and about -80 millivolts for the Asn mutant. At pH 7.0, reduction of Fe(III) to Fe(II) in the Glu and Asp mutants is accompanied by uptake of a proton by the protein. These studies demonstrate that Mb can tolerate substitution of a buried hydrophobic group by potentially charged and polar residues and that such amino acid replacements can lead to substantial changes in the redox thermodynamics of the protein.     

利用反向遗传技术对H_3N_2亚型流感病毒NA基因突变的研究

为了拯救出H3N2亚型流感病毒的重组新病毒,利用反向遗传学手段,8个质粒共同转染293T细胞,包装带有双点突变（第119位氨基酸由E突变为V,第222位氨基酸由I突变成L）、单点突变和野生型的流感病毒H3N2;在MDCK细胞中传代包装成的H3N2病毒。结果表明,野生流感病毒H3N2和其突变株包装成功,第119位氨基酸单点突变型滴度与野生型的相近,而第222位氨基酸单点突变和双突变型滴度要比野生型的低。本实验成功证明了H3N2神经氨酸酶上两个位点（第119和222位氨基酸）对病毒包装及复制起到关键的作用,且NA上第222位氨基酸相对于第119位氨基酸显得要更重要。     

MS-222、丁香油、苯唑卡因对养殖美洲鲥幼鱼的麻醉效果

研究了MS-222、丁香油、苯唑卡因3种麻醉剂对美洲鲥Alosa sapidissima幼鱼的麻醉效果,并运用该3种麻醉剂的适宜剂量对美洲鲥幼鱼进行了运输试验。麻醉试验结果表明:在较高麻醉浓度(MS-222为75 mg/L以上,丁香油为20 mg/L以上,苯唑卡因为40 mg/L以上)下,鱼很快(30 min内)停止鳃盖张合运动,且停止鳃盖运动的鱼在空气中暴露一定时间(10 min内)后也能够复苏;在适宜的麻醉浓度(MS-222为20-30 mg/L,丁香油为8-10 mg/L;苯唑卡因为20-30 mg/L)下,鱼能够进入麻醉状态,且能保持很长时间(12 h);麻醉效果随着水温的升高而增强;在20 mg/L MS-222麻醉剂下,小规格鱼较大规格鱼更容易进入麻醉状态,而在10 mg/L丁香油和20 mg/L苯唑卡因麻醉剂下,小规格鱼却难进入麻醉状态。运输试验结果表明:麻醉运输组和对照组(非麻醉运输组)鱼血清中皮质醇的含量均显著高于基础组(运输前)(P<0.05);麻醉运输后鱼血清中皮质醇的含量虽均有一定程度的升高,但明显低于对照组,其中仅苯唑卡因麻醉运输组鱼血清中皮质醇的含量显著低于对照组(P<0.05)。试验结果表明,苯唑卡因更适合用于运输美洲鲥的麻醉。     

Redesigning trypsin: alteration of substrate specificity

A general method for modifying eukaryotic genes by site-specific mutagenesis and subsequent expression in mammalian cells was developed to study the relation between structure and function of the proteolytic enzyme trypsin. Glycine residues at positions 216 and 226 in the binding cavity of trypsin were replaced by alanine residues, resulting in three trypsin mutants. Computer graphic analysis suggested that these substitutions would differentially affect arginine and lysine substrate binding of the enzyme. Although the mutant enzymes were reduced in catalytic rate, they showed enhanced substrate specificity relative to the native enzyme. This increased specificity was achieved by the unexpected differential effects on the catalytic activity toward arginine and lysine substrates. Mutants containing alanine at position 226 exhibited an altered conformation that may be converted to a trypsin-like structure upon binding of a substrate analog.     

Location and chemical synthesis of a binding site for HIV-1 on the CD4 protein

The human immunodeficiency virus type 1 (HIV-1) uses the CD4 protein as a receptor for infection of susceptible cells. A candidate structure for the HIV-1 binding site on the CD4 protein was identified by epitope mapping with a family of eight functionally distinct CD4-specific monoclonal antibodies in conjunction with a panel of large CD4-derived synthetic peptides. All of the seven epitopes that were located reside within two immunoglobulin-like disulfide loops situated between residues 1 and 168 of the CD4 protein. The CD4-specific monoclonal antibody OKT4A, a potent inhibitor of HIV-1 binding, recognized a site between residues 32 and 47 on the CD4 protein. By analogy to other members of the immunoglobulin superfamily of proteins, this particular region has been predicted to exist as a protruding loop. A synthetic analog of this loop (residues 25 to 58) showed a concentration-dependent inhibition of HIV-1-induced cell fusion. It is proposed that a loop extending from residues 37 to 53 of the CD4 protein is a binding site for the AIDS virus.     

Resolution of a signal transfer region from a general binding domain in gbeta for stimulation of phospholipase C-beta2

Signaling by guanine nucleotide-binding proteins (G proteins) involves sequential protein-protein interactions. G protein-betagamma subunit (Gbetagamma) interactions with phospholipase C-beta2 (PLC-beta2) were studied to determine if all Gbeta contacts are required for signaling. A peptide encoding Gbeta amino acid residues 86 to 105 stimulated PLC-beta2. Six residues (96 to 101) within this sequence could transfer signals and thus constitute a core signal transfer region. Another peptide, encoding Gbeta amino acid residues 115 to 135, did not substantially stimulate PLC-beta2 by itself but inhibited Gbetagamma stimulation, indicating that residues 115 to 135 constitute a general binding domain. Resolution of signal transfer regions from general binding domains indicates that all protein-protein contacts are not required for signal transfer and that it may be feasible to synthesize agonists and antagonists that regulate intracellular signal flow.     

Receptor and antibody epitopes in human growth hormone identified by homolog-scanning mutagenesis

A strategy, termed homolog-scanning mutagenesis, was used to identify the epitopes on human growth hormone (hGH) for binding to its cloned liver receptor and eight different monoclonal antibodies (Mab's). Segments of sequences (7 to 30 residues long) that were derived from homologous hormones known not to bind to the hGH receptor or Mab's, were systematically substituted throughout the hGH gene to produce a set of 17 chimeric hormones. Each Mab or receptor was categorized by a particular subset of mutant hormones was categorized by a particular subset of mutant hormones that disrupted binding. Each subset of the disruptive mutations mapped within close proximity on a three-dimensional model of hGH, even though the residues changed within each subset were usually distant in the primary sequence. The mapping analysis correctly predicted those Mab's which could or could not block binding of the receptor to hGH and further suggested (along with other data) that the folding of these chimeric hormones is like that of HGH. By this analysis, three discontinuous polypeptide determinants in hGH--the loop between residues 54 and 74, the central portion of helix 4 to the carboxyl terminus, and to a lesser extent the amino-terminal region of helix 1--modulate binding to the liver receptor. Homolog-scanning mutagenesis should be of general use in identifying sequences that cause functional variation among homologous proteins.     

Detection of a nonuniform distribution of polonium-210 on the moon with the apollo 16 alpha particle spectrometer

The polonium-210 activity of the lunar surface is significantly larger than the activity of its progenitor radon-222. This result establishes unequivocally that radon emanation from the present-day moon varies considerably within the 21-year half-life of lead-210, the parent nuclide of polonium-210. There are large variations and well-localized enhancements in polonium-210 activity over much of the moon's surface.