ALCAR模型与叠加过程的分解

本文提出一种多变量时间序列分析的数学模型—待定线性组合自回归模型（ALCAR（n）），数字仿真分析表明在未知信号及噪声特性参数条件下，ALCAR（n）模型分析可以高精度地估出叠加过程中各信号的自回归参数以及高精度地将各叠加信号分解开。     

关于PLA优化设计的一个综合算法

讨论ＰＬＡ优化设计的组合函数分解问题和ＰＬＡ折迭问题，得出对算法有用的两个直接结果，最后将二者联系起来，给出一个综合算法。     

Twisting orientation and the role of transient states in polymer crystallization

A possible connection is suggested and explored between non-planer crystal habits in banded polymer spherulites and disordered chain folding in polymers crystallized relatively rapidly from the melt. It is proposed that, when lateral growth faces and fold surfaces are not orthogonal (because chain stems are tilted with respect to the lamellar normal), different degrees of disorder develop at opposite fold surfaces. Resulting differences in surface stress give rise to bending moments, but these are likely to be of transient existence. It is shown that, on this basis, an appealingly simple rationale can be developed to account for the complex and hitherto puzzling observations of Bassett and Hodge on polyethylene spherulites, including S-bending and non-uniform axial twisting in lamellae, and also an empirical correlation between these deformations. Much depends, however, upon interactions between interleaved crystals and upon relaxation of bending moments. Existing evidence in support of the rationale is outlined. Implications with respect to polymers other than polyethylene, and to kinetics of crystallization in general, are discussed briefly. Calculations concerning axial twisting under the influence of surface stresses suggest that the twisted crystals incorporate twist boundaries, possibly formed by aggregation of dislocations generated during the growth of what must initially be relatively disordered crystals. The ‘chiral’ factor determining handedness of twisting in a given crystal is the direction in which chain stems tilt with respect to the lamellar normal.     

Crystal structure of T4-lysozyme generated from synthetic coding DNA expressed in Escherichia coli

The polypeptide produced by expressing a chemically synthesizedgene coding for the amino-acid sequence of T4-lysozyme has beencrystallized and subjected to X-ray diffraction. The crystalstructure has been refined to a standard R-factor of 0.191 fordata between 8 and 2 ? resolution. The refined model is essentiallythe same as the well-known structure of wild-type T4-lysozymedetermined previously by Matthews et al. (1987). Some smallchanges in the C-terminal region, which is important in maintainingthe folded structure, have been noted. In addition to confirmingthat the synthetic gene product is very close to the wild type,this structure provides a benchmark for protein engineeringexperiments on the folding and the catalytic activity of thismolecule by the method of gene synthesis.     

Search for the most stable folds of protein chains: I. Application of a self-consistent molecular field theory to a problem of protein three-dimensional structure prediction

We present a general approach to the prediction of 3-D foldsof protein chains from their amino acid sequences. The approachis based on the use of the self-consistent molecular field theoryfor long-range interactions, the use of 1-D statistical mechanicsfor short-range interactions and on the discovery that thereis and should only be a relatively small discrete set of foldingpatterns. This makes it possible to examine the full varietyof ‘potentially stable’ folds and to determine thethermodynamically stable structure. In this paper, we give thegeneral theoretical background of the approach. The encouragingresults of the application of this approach to ß-domainsare described in another paper.     

Association of complementary fragments and the elucidation of protein folding pathways

Natural or engineered sites for chemical cleavage can be usedto generate complementary fragments of well characterized proteins.The peptide fragments represent a unique tool for studying earlyevents in protein folding, since these are usually the mostinaccessible to the experimentalist. Analysis of the isolatedfragments in nondenaturing conditions together with the determinationof the structure of the folded non-covalent complexes and, mostimportantly, the kinetic analysis of the resulting second-orderassociation/folding reaction can give a more complete pictureof a folding pathway. The contribution of fragments to the understandingof some well characterized protein folding pathways is discussed.     

Hierarchical strategy for protein folding and design: synthesis and expression of T4 lysozyme gene and two putative folding mutants

A T4 lysozyme-coding DNA sequence of 495 bp was chemically synthesizedand cloned by ligation of 26 deoxyribooligo-nucleotide fragmentsin two steps with a linearized plasmid followed by transformation.On selection by colony hybridization and DNA sequence analysis,clone pTLY.10 was identified to contain a complete T4 lysozymesynthetic DNA. On expression under lac-promoter, unfused T4lysozyme was obtained in {small tilde}4–6% yield. Thedesign and synthesis of two putative folding mutants, flexible(Gly-Gly-Gly) and rigid (Asn-Asp-Gly) at position 73-74-75,were based on hierarchical principles. Both mutants lost enzymaticactivity of the wildtype. These results are readily understandableif the hierarchical organization of the structure is taken intoaccount. A possible explanation is that the catalytic sitesare blocked in both mutants.     

行波离子迁移质谱技术在蛋白质结构研究中的应用

离子迁移(ion mobility)是一种在分子离子化后,非溶液环境下的分离技术。与依靠离子质量与电荷比进行分离的质谱技术不同,离子迁移是根据离子形状与电荷比实现分离的。因此,离子迁移技术可以实现对质量相同而形状不同的离子分离,其与质谱技术联用可为研究者提供更加丰富的结构信息。最新发展的行波离子迁移技术大大提高了灵敏度和分离速度,适用于研究天然浓度条件下的蛋白质,其在蛋白质单体折叠与去折叠以及蛋白复合体亚基组装的研究中已崭露头角。     

某雷达天线举升翻转机构的设计

针对某一机动型大阵列天线的举升翻转机构设计进行了详细的论述,着重介绍了该机构中以液压油缸作为驱动力的四连杆结构形式的翻转机构和由直线导轨和液压油缸组成的举升机构以及由螺旋机构、摩擦片组成的锁定机构的工作原理和结构设计。机构在系统设计中,采用了刚性同步原理,以实现两套翻转机构、举升机构间的同步翻转和拳升的运动过程。此外,还对该机构的液压系统的设计进行系统的阐述和论证。该机构已成功地应用于某机动式中远程三坐标雷达的结构设计中。     

YH-1800全自动糊箱机结构设计

为了克服国内糊箱机存在的速度慢、可靠性低、稳定性差等问题,结合目前市场需求,通过对纸张定位、上胶、折合、压合等机构的优化设计和电气控制系统的改进,设计出新型YH-1800全自动糊箱机,提高了我国全自动糊箱机的研发水平。