东北地区高温对玉米生产的影响及对策

极端高温是制约东北农作区玉米生产的主要气象灾害之一.本文通过研究气候变暖背景下玉米不同生育时期内日最高温度大于30℃的积温(AT)和日最高温度大于30℃的天数(AD)的时空变化特征,分析了极端高温对东北农作区不同地区玉米生产的影响,并探讨了应对高温的对策.结果表明:1961—2010年,东北农作区玉米生育期内温度显著升高,开花期(花前花后20 d)最高温度明显大于其他生育时期,玉米全生育期、营养生长期(播种到开花前11 d)、花期和生育后期(开花后11 d到收获)4个时期日最高温度的气候趋向率分别为0.16、0.14、0.06和0.23℃·10 a-1.近50年东北农作区玉米全生育期AT明显增加,西南部地区的AT明显高于其他区域,营养生长期AT的增加趋势明显大于其他两个时期.玉米全生育期AD明显增加,高值区也主要集中在西南部地区,生育后期的AD的增加趋势大于其他两个生育时期.东北农作区玉米生育期内极端高温显著影响玉米生产,其中营养生长期的极端高温对玉米产量的不利影响十分显著,松辽平原地区玉米生产的高温风险明显大于其他地区.优化作物布局,培育耐高温品种,调整玉米生产管理措施,构建防灾减灾玉米生产体系是东北农作区玉米生产应对高温风险的有效措施.     

Contribution of Residue B5 to the Folding and Function of Insulin and IGF-I: CONSTRAINTS AND FINE-TUNING IN THE EVOLUTION OF A PROTEIN FAMILY*

Proinsulin exhibits a single structure, whereas insulin-like growth factors refold as two disulfide isomers in equilibrium. Native insulin-related growth factor (IGF)-I has canonical cystines (A6—A11, A7–B7, and A20—B19) maintained by IGF-binding proteins; IGF-swap has alternative pairing (A7–A11, A6—B7, and A20—B19) and impaired activity. Studies of mini-domain models suggest that residue B5 (His in insulin and Thr in IGFs) governs the ambiguity or uniqueness of disulfide pairing. Residue B5, a site of mutation in proinsulin causing neonatal diabetes, is thus of broad biophysical interest. Here, we characterize reciprocal B5 substitutions in the two proteins. In insulin, His^B5 → Thr markedly destabilizes the hormone (ΔΔG_u 2.0 ± 0.2 kcal/mol), impairs chain combination, and blocks cellular secretion of proinsulin. The reciprocal IGF-I substitution Thr^B5 → His (residue 4) specifies a unique structure with native ¹H NMR signature. Chemical shifts and nuclear Overhauser effects are similar to those of native IGF-I. Whereas wild-type IGF-I undergoes thiol-catalyzed disulfide exchange to yield IGF-swap, His^B5-IGF-I retains canonical pairing. Chemical denaturation studies indicate that His^B5 does not significantly enhance thermodynamic stability (ΔΔG_u 0.2 ± 0.2 kcal/mol), implying that the substitution favors canonical pairing by destabilizing competing folds. Whereas the activity of Thr^B5-insulin is decreased 5-fold, His^B5-IGF-I exhibits 2-fold increased affinity for the IGF receptor and augmented post-receptor signaling. We propose that conservation of Thr^B5 in IGF-I, rescued from structural ambiguity by IGF-binding proteins, reflects fine-tuning of signal transduction. In contrast, the conservation of His^B5 in insulin highlights its critical role in insulin biosynthesis.     

Protein structure and the spandrels of San Marco: insulin's receptor-binding surface is buttressed by an invariant leucine essential for its stability.

Insulin provides a model of induced fit in macromolecular recognition: the hormone's conserved core is proposed to contribute to a novel receptor-binding surface. The core's evolutionary invariance, unusual among globular proteins, presumably reflects intertwined constraints of structure and function. To probe the architectural basis of such invariance, we have investigated hydrophobic substitutions of a key internal side chain (Leu(A16)). Although the variants exhibit perturbed structure and stability, moderate receptor-binding activities are retained. These observations suggest that the A16 side chain provides an essential structural buttress but unlike neighboring core side chains, does not itself contact the receptor. Among invertebrate insulin-like proteins, Leu(A16) and other putative core residues are not conserved, suggesting that the vertebrate packing scheme is not a general requirement of an insulin-like fold. We propose that conservation of Leu(A16) among vertebrate insulins and insulin-like growth factors is a side consequence of induced fit: alternative packing schemes are disallowed by lack of surrounding covariation within the hormone's hidden receptor-binding surface. An analogy is suggested between Leu(A16) and the spandrels of San Marco, tapering triangular spaces at the intersection of the dome's arches. This celebrated metaphor of Gould and Lewontin emphasizes the role of interlocking constraints in the evolution of biological structures.     

利用肠道菌群的分布和16S DNA序列研究鲤科肠道菌系统演化关系

肠道微生物与寄主具有复杂的、多方面的相互依存效应,这种依存效应所产生的共生关系或协同进化关系既可反映寄主间的系统演化关系,也可显示肠道微生物间的系统演化关系,共生关系或协同进化关系是由于寄主与肠道微生物两者之间存在着相互自然选择作用所形成的,在长期的进化历程中逐步发生的共生关系信息很可能被记录在DNA序列中。本文通过检测鲤鱼科8种鱼中9种肠道菌群的分布含量对这9种菌群进行分析,且利用从GenBank调取这9种肠道细菌菌属的43个种或亚种的16S DNA序列的构建NJ树和MP树,将这6个科9个属43个种或亚种分为革兰氏阴性和革兰氏阳性两大类群（一级分枝）。在这两类群中,又以科为单位分为6个亚类群（二级分枝）,而肠杆菌科中则以属为单位分为4个小类群（三级分枝）,此外球状菌与杆状菌也能截然分开。将16S DNA的NJ树隐去所有的种,以属为单位所得到的以分枝形式的无根树在拓扑结构上与菌群分布含量（寄主范围）所构建的无根树相近,但芽孢杆菌在两种无根树的位置中有较大的差异。如果提高检测水平,扩大所检测的寄主对象,这种差异有可能消除。 Abstract:There is a complex- and multi-effect for interdependent survival between intestinal- microorganisms and hosts.The symbiosis or coevolution that results from this effect for interdependent survival is used to reveal the phylogenies of hosts as well as intestinal microorganisms.The symbiosis or coevolution between intestinal microorganisms and hosts has been generated by interactive natural selection occurred between them.The symbiosis information that has been formed by interactive natural selection during a long evolutionary process must be recorded in DNA sequences.According to this point of view,we analyzed the phylogeny of 9 intestinal bacteria genera using their contents in intestines of 8 Cyrinidate species.At the same time,we fetched the 16S rRNA gene DNA sequences of 43 intestinal bacteria species being included in these nine genera of six intestinal families from GeneBank and constructed phylogenetic trees by NJ and MP methods.The NJ tree and MP tree have the same topologic configuration and are identical with the classical phylogenetic tree.Both the trees of 16S rRNA gene separated 43 bacteria species into gram-negative bacteria group and the gram-positive bacteria group,which are the first branches.Each of the first branches (groups) made again 6 subbranches (subgroups) where each subbranch is a family.Especially,the subbranch (subgroup) of enterobacteriaceace made again four small branches as genus taxon.This tree also shows that bacilliform bacterium is distinct from each other in the NJ and MP trees.After all species on the tree are merged,the topological configuration of the unrooted tree of 16S gene is closed to that of the host range unrooted tree.However,the position of bacillus is greatly changed on both the unrooted trees.The difference can be found if we increase the examination level and extend the hosts examed.     

用于原油开采的假单胞菌G31的特性研究

菌株G31是从胜利油田污水中分离到的1株假单胞菌（Pseudomonas sp.),该菌株在石油液体培养基中能够生长发酵,产生有机酸和表面海活性物质,可以应用于微生物三次采油。菌株G31可以降解和乳化石油、降低石油的粘度,其产物可以降低油水的界面张力,增加石油的流动性。室内岩心试验结果表明利用菌株G31发酵液进行驱油可使原油采收率提高10%以上。     

Enhancing the Activity of a Protein by Stereospecific Unfolding: CONFORMATIONAL LIFE CYCLE OF INSULIN AND ITS EVOLUTIONARY ORIGINS*S??

A central tenet of molecular biology holds that the function of a protein is mediated by its structure. An inactive ground-state conformation may nonetheless be enjoined by the interplay of competing biological constraints. A model is provided by insulin, well characterized at atomic resolution by x-ray crystallography. Here, we demonstrate that the activity of the hormone is enhanced by stereospecific unfolding of a conserved structural element. A bifunctional β-strand mediates both self-assembly (within β-cell storage vesicles) and receptor binding (in the bloodstream). This strand is anchored by an invariant side chain (Phe^B24); its substitution by Ala leads to an unstable but native-like analog of low activity. Substitution by d-Ala is equally destabilizing, and yet the protein diastereomer exhibits enhanced activity with segmental unfolding of the β-strand. Corresponding photoactivable derivatives (containing l- or d-para-azido-Phe) cross-link to the insulin receptor with higher d-specific efficiency. Aberrant exposure of hydrophobic surfaces in the analogs is associated with accelerated fibrillation, a form of aggregation-coupled misfolding associated with cellular toxicity. Conservation of Phe^B24, enforced by its dual role in native self-assembly and induced fit, thus highlights the implicit role of misfolding as an evolutionary constraint. Whereas classical crystal structures of insulin depict its storage form, signaling requires engagement of a detachable arm at an extended receptor interface. Because this active conformation resembles an amyloidogenic intermediate, we envisage that induced fit and self-assembly represent complementary molecular adaptations to potential proteotoxicity. The cryptic threat of misfolding poses a universal constraint in the evolution of polypeptide sequences.How insulin binds to the insulin receptor (IR)² is not well understood despite decades of investigation. The hormone is a globular protein containing two chains, A (21 residues) and B (30 residues) (Fig. 1A). In pancreatic β-cells, insulin is stored as Zn²⁺-stabilized hexamers (Fig. 1B), which form microcrystal-line arrays within specialized secretory granules (1). The hexamers dissociate upon secretion into the portal circulation, enabling the hormone to function as a zinc-free monomer. The monomer is proposed to undergo a change in conformation upon receptor binding (2). In this study, we investigated a site of conformational change in the B-chain (Phe^B24) (arrow in Fig. 1A). In classical crystal structures, this invariant aromatic side chain (tawny in Fig. 1B) anchors an antiparallel β-sheet at the dimer interface (blue in Fig. 1C). Total chemical synthesis is exploited to enable comparison of corresponding d- and l-amino acid substitutions at this site, an approach designated “chiral mutagenesis” (3-5). In the accompanying article, the consequences of this conformational change are investigated by photomapping of the receptor-binding surface (6). Together, these studies redefine the interrelation of structure and activity in a protein central to the hormonal control of metabolism.Open in a separate windowFIGURE 1.Sequence and structure of insulin. A, sequences of the B-chain (upper) and A-chain (lower) with disulfide bridges as indicated. The arrow indicates invariant Phe^B24. The B24-B28 β-strand is highlighted in blue. B, crystal structure of the T₆ zinc insulin hexamer (Protein Data Bank code 4INS): ribbon model (left) and space-filling model (right). The B24-B28 β-strand is shown in blue, and the side chain of Phe^B24 is highlighted in tawny. The B-chain is otherwise dark gray; the A-chain, light gray; and zinc ions, magenta. Also shown at the left are the side chains of His^B10 at the axial zinc-binding sites. C, cylinder model of the insulin dimer showing the B24-B26 antiparallel β-sheet (blue) anchored by the B24 side chain (tawny circle). The A- and B-chains are shown in light and dark gray, respectively. The protomer at the left is shown in the R-state, in which the central α-helix of the B-chain is elongated (B3-B19 in the frayed R^f protomer of T₃R^f₃ hexamers and B1-B19 in the R protomer of R₆ hexamers). The three types of zinc insulin hexamers share similar B24-B26 antiparallel β-sheets as conserved dimerization elements.The structure of an insulin monomer in solution resembles a crystallographic protomer (Fig. 2A) (7-9). The A-chain contains an N-terminal α-helix, non-canonical turn, and second helix; the B-chain contains an N-terminal segment, central α-helix, and C-terminal β-strand. The β-strand is maintained in an isolated monomer wherein the side chain of Phe^B24 (tawny in Fig. 2A), packing against the central α-helix of the B-chain, provides a “plug” to seal a crevice in the hydrophobic core (Fig. 2B). Anomalies encountered in previous studies of insulin analogs suggest that Phe^B24 functions as a conformational switch (4, 7, 10-14). Whereas l-amino acid substitutions at B24 generally impair activity (even by such similar residues as l-Tyr) (15), a seeming paradox is posed by the enhanced activities of nonstandard analogs containing d-amino acids (10-12).

TABLE 1

Previous studies of insulin analogs

生态能质(eco-exergy)在水生生态系统建模和评价中的应用

生态能质(eco-exergy)是指系统从给定状态达到热力学平衡状态所做的功,可以度量生态系统的复杂生物化学组分及生态结构。系统具有的能质越大,有序化程度越高,稳定性也越强。生态能质和比生态能质(specific eco-exergy)指标能够评价水生生态系统健康状况,对水生生态系统演替阶段具有指示作用。本文阐述了生态能质的定义、生态学意义以及生态能质值和权重因子fi值的计算方法。对生态能质作为功能函数在水生生态系统结构动力学模型(structural dynamic models,SDMs)中以及作为生态指标在生态系统健康评价、生态恢复研究中的实际应用进行了总结。最后探讨了生态能质指标的局限性以及未来的发展。此外,文中建议将eco-exergy和specific eco-exergy统一翻译为生态能质和比生态能质。     

茁芽短梗霉原生质体激光诱变及高产菌株筛选

目的：通过普鲁兰(pullulan)产生菌-茁芽短梗霉(Aureobasidium Pullulans)原生质体的激光诱变,以得到普鲁兰高产菌株。方法：利用正交实验研究了茁芽短梗霉原生质体的制备与再生并确定了其最佳条件为：菌体以1％的甘氨酸预处理;在0．1mol／L pH 6．0柠檬酸一柠檬酸钠缓冲液,含0．7mol／L NaCl的高渗稳定液中;经蜗牛酶0．2％、纤维素酶0．1％、溶菌酶0．2％的混合酶酶解15min。采用He-Ne激光诱变茁芽短梗霉原生质体筛选得到普鲁兰高产菌株J208,其蔗糖转化率达到53．3％,是原始菌株的10．6倍。结论：用激光诱变茁芽短梗霉原生质体是获得普鲁兰高产菌株的新途径。     

基于热扩散方法测定树木蒸腾的潜在误差分析

蒸腾作为植被蒸散的主要分量,是植物水分生理生态学研究的核心内容,其测定方法的研究备受关注.热扩散方法是测量树木蒸腾的最优方法之一.大量研究表明,应用热扩散方法测定的单株树木蒸腾量以及扩展到林分尺度蒸腾耗水量均相对准确,但在测定过程以及测定值与蒸腾真实值之间存在着潜在误差.本文综述了热扩散方法在树干液流通量密度测定以及从温差测定点到单株、从单株到林分尺度扩展过程中存在的潜在误差,展望了我国开展热扩散方法潜在误差分析的主要研究方向,并提出了解决其潜在测量误差的方法.