Electrophoresis of flexible macromolecules: evidence for a new mode of transport in gels

Movement of macromolecules through low concentration agarose gels was investigated with linear poly(styrenesulfonate), linear DNA, star-shaped poly(styrenesulfonate), and circular DNA. Mobilities of weakly entangled flexible macromolecules were independent of molecular radius; within a homologous chemical sequence, electrophoretic separation at low field strengths depended solely on the degree of polymerization. These observations cannot be explained either by sieving or by reptation mechanisms; transport was apparently controlled by spatial variations of chain configurational entropy. Only when the chain was highly entangled did chain topology affect mobility. Evidence for entropically regulated transport clarifies how gel electrophoresis separates flexible macromolecules.     

Threonine deaminase: a novel activity stain on polyacrylamide gels

With phenazine methosulfate and nitro blue tetrazolium, an activity stain for threonine deaminase has been developed. Because the deamination reaction does not involve any overall oxidation or reduction, it is proposed that one of the intermediates of the reaction, alpha-aminocrotonate or alpha-iminobutyrate, is the reducing agent. Studies with ferricyanide as the artificial electron acceptor indicate that a decarboxylation of the intermediate occurs during the dye reduction.     

Colloidal jamming at interfaces: a route to fluid-bicontinuous gels

Colloidal particles or nanoparticles, with equal affinity for two fluids, are known to adsorb irreversibly to the fluid-fluid interface. We present large-scale computer simulations of the demixing of a binary solvent containing such particles. The newly formed interface sequesters the colloidal particles; as the interface coarsens, the particles are forced into close contact by interfacial tension. Coarsening is markedly curtailed, and the jammed colloidal layer seemingly enters a glassy state, creating a multiply connected, solidlike film in three dimensions. The resulting gel contains percolating domains of both fluids, with possible uses as, for example, a microreaction medium.     

Collagen molecules: distribution of alpha chains

To ascertain the distribution of alpha chains within the collagen molecule, intramolecular cross-links were introduced into tropocollagen by reacting formaldehyde with dilute homogeneous molecular dispersions of collagen extracted from lathyritic guinea pig skin. Denaturation, chromatography on carboxymethyl cellulose, measurement of molecular weight, and analyses of the amino acids of the cross-linked product indicate that most, if not all, of the collagen molecules consist of two alpha1 chains and one alpha2 chain [(alpha1)(2)(alpha2)(1)].     

Collagen: mobile water content of frozen fibers

From the change in the nuclear magnetic resonance splitting of heavy water in oriented wet collagen fibers at low temperatures, it is estimated that about 0.6 gram of heavy water per gram of collagen does not freeze. This estimate has been confirmed by a measurement of the heat evolved on melting "frozen" wet collagen. The water that does not freeze retains liquid-like mobility even at temperatures as low as -50 degrees C.     

Reference architecture design for farm management information systems: a multi-case study approach

Precision Agriculture - One of the key elements of precision agriculture is the farm management information system (FMIS) that is responsible for data management, analytics and subsequent decision...     

Crystal structure of a neutralizing human IGG against HIV-1: a template for vaccine design

We present the crystal structure at 2.7 angstrom resolution of the human antibody IgG1 b12. Antibody b12 recognizes the CD4-binding site of human immunodeficiency virus-1 (HIV-1) gp120 and is one of only two known antibodies against gp120 capable of broad and potent neutralization of primary HIV-1 isolates. A key feature of the antibody-combining site is the protruding, finger-like long CDR H3 that can penetrate the recessed CD4-binding site of gp120. A docking model of b12 and gp120 reveals severe structural constraints that explain the extraordinary challenge in eliciting effective neutralizing antibodies similar to b12. The structure, together with mutagenesis studies, provides a rationale for the extensive cross-reactivity of b12 and a valuable framework for the design of HIV-1 vaccines capable of eliciting b12-like activity.     

儿童专用型羊骨胶原多肽速溶粉的研制

以奶粉、豆粉为基料,在添加羊骨胶原多肽的同时,适当添加各种蔬菜粉、燕麦粉及其他辅料,生产儿童专用型羊骨胶原多肽速溶粉。以单因素试验和正交试验为主要研究方法筛选最优配方。结果表明：儿童型羊骨胶原多肽速溶粉的配方Ⅰ（按100g产品计算）为：17．58g豆粉＋9．48g奶粉＋5．40g胡萝卜粉＋2．70g菠菜粉＋2．70g南瓜粉＋8．10g山楂粉＋6．50g白砂糖＋7．50g羊骨胶原多肽＋41．10g燕麦粉。配方Ⅱ（按100g产品计算）为：27．18g豆粉＋14．63g奶粉＋8．38g胡萝卜粉＋4．18g菠菜粉＋4．18g南瓜粉＋O．33g木糖醇＋0．18g柠檬酸＋7．50g羊骨胶原多肽＋33．45g燕麦粉。经检测,配方Ⅰ、Ⅱ中钙（mg／（100g））含量分别为1044．5和1929．8。     

Collagen has a discrete family of reactive hydroxylysyl and lysyl side-chain amino groups

Several cross-linking substances which derive from lysine have been isolated from hydrolyzates of collagen and elastin. This observation suggests that certain lysyl side chains exhibiting enhanced reactivity and unique configuration may participate in cross-linking. In native collagen there is a small family of lysyl and hydroxylysyl side chains which exhibit a high propensity of Schiff base formation.     

猪皮胶原蛋白提取过程中酶解条件优化及其结构鉴定

采用酶法从猪皮中提取胶原蛋白,以胶原蛋白的提取率为评价指标,对工艺中的酶解pH,酶解时间和胃蛋白酶用量3个因素进行优化,实验结果表明,酶解液pH 2.2,酶解时间18h,酶用量1%为最佳工艺组合,在此条件下胶原蛋白提取率可达84.35%±0.33%,纯度为82.5%±1.6%;所得胶原主要由α,β和γ3种亚基组分组成,具有较高的热稳定性;红外光谱和圆二色谱测定结果显示,其具备典型的胶原蛋白吸收特征,证明胶原天然三螺旋结构保存完整.     

DEPIVOT: A model for center-pivot design and evaluation

Center-pivot sprinkler irrigation became very popular. Hence, aimed at farmers advising, the simulation model DEPIVOT has been developed with the objective of design new systems or changes in systems in operation. The software consists of a simulation package developed in Visual Basic and data base in Access. The model comprises five main sub-models for: (a) computation of the gross irrigation requirements; (b) sizing of the lateral pipe spans through the hydraulics computation of the friction losses and respective operative simulation considering to the effects of topography and the possible requirements of an end gun; (c) selecting a sprinklers package with computation of pressure and discharge at each outlet and including the consideration of pressure regulators; (d) verification of the sprinklers package through estimation of runoff potential by comparing application and infiltration rates at selected locations along the lateral; and (e) estimating the expected uniformity performance indicators when in operation. The user verifies if performance is within target values set at start and may develop and compare alternative sprinkler packages until appropriate conditions are obtained. When the model is used for evaluation of systems under operation using data collected in farmers’ fields performance indicators are computed and, responding to farmers’ needs, the model may be used to design changes in the existing systems and to improve management. This paper describes the model and shows examples of applications to select a sprinkler package and assess the respective runoff potential.     

An interface design for microcomputer control of a potato storage

The design of an interface circuit to connect a microcomputer with a potato storage is described. The interface provides for the measurement of 21 temperatures, input of 8 digital signals and output of 16 digital signals under computer control. Computer I/O is handled through one input and one output port. Interface design, programing and preliminary test are described.     

计算机应用基础考试系统的设计

为了适应计算机课程的特点,更加准确地测试学生计算机实际操作能力,我们开发了计算机应用基础考试系统。该系统提供了开放式的考试环境,可以测试学生在Windows环境下计算机操作能力和各种应用软件使用能力。