The LLSGIV stretch of the N-terminal region of HIV-1 gp41 is critical for binding to a model peptide, T20

A number of peptides and peptide analogs derived from the membraneproximal region of gp41 ectodomain are found to be effectiveinhibitors of human immunodeficiency virus type 1 (HIV-1)-mediatedfusion events. One of them, T20 (aa 638–673), was founddisordered and sparingly soluble in water, but became solubleupon mixing with selected, structured peptides from the aminoterminal heptad repeat (HR1) region of gp41 using a simple andsensitive method of reduction in the scattering of T20 suspension.From the results on mapping the locus of interaction with T20by employing partially overlapping peptides derived from HR1,it was concluded that the LLSGIV segment was a critical dockingsite for the C-terminal peptide of gp41 in its putative inhibitoryaction consistent with a previous fluorescence study. It wasalso found that peptides capable of solubilizing T20 dispersionhave a high content of helix, as well as ß-strand,conformation in aqueous solution. Specificity of T20/HR1-derivedpeptide binding was ascertained by using a scrambled sequenceof a T20-active peptide and a plateau in scattering reductionof T20 suspension with variation in the concentration of a T20-activeHR1 peptide. Implications on the mechanism of T20 inhibitionand the sequence of folding of the gp41 core structure are discussed.     

Applications of the critical phenomena concept in liquid chromatography for functionally type separation of macromolecules

Summary Functional type separation of hydroxyl-containing poly(butylen terephtalates) by liquid chromatography of molecules in “critical conditions” was investigated. Under such conditions the change in the free energy, ΔF, of a homogeneous macromolecule equals zero when entering a pore, irrespective of its length; in this case the chromatogram obtained is not complicated by the separation of the molecules in terms of sizes, and contains information only on the types of functionality. The critical conditions of investigation have been determined on silica in a heptane-tetrahydrofuran (THF) mixture.     

A new concept for glycosyltransferase inhibitors: nonionic mimics of the nucleotide donor of the human blood group B galactosyltransferase

Glycosyltransferases play an important role in the formation of oligosaccharides and glycoconjugates. To find suitable and selective inhibitors for this class of enzymes is still challenging. Here, we describe a novel concept that allows the design of inhibitors based on the structure of the donor substrate binding pocket. As a first step we describe the design, synthesis and analysis of inhibitors of the human blood group B galactosyltransferase (GTB). This enzyme served as a model system to study the concept, which can be used for easy access of glycosyltransferase inhibitors in general. In silico docking of bicyclic heteroaromatic ligands to GTB and experimental verification of binding affinities by saturation transfer difference NMR (STD NMR) spectroscopy gave 9-N-pentityl uric acid derivatives as non-ionic mimics of UDP. Two derivatives were synthesized and showed inhibitory activity for GTB as determined by competitive STD NMR experiments and by a radiolabeled enzyme assay.     

Testing for nonlinear deterministic components when the order of integration is unknown

We consider testing for the presence of nonlinearities in the deterministic component of a time series, approximating the potential nonlinear behaviour using a Fourier function expansion. In contrast to procedures that are currently available, we develop tests that are robust to the order of integration, in the sense that they are asymptotically correctly sized regardless of whether the stochastic component of the series is stationary or contains a unit root. The tests we propose take the form of Wald statistics based on cumulated series, together with a correction factor to line up the asymptotic critical values across the I(0) and I(1) environments. The local asymptotic power and finite sample properties of the tests are evaluated using various different correction factors. We envisage that the testing procedure we recommend should be very useful to applied researchers wishing to draw robust inference regarding the presence of nonlinear deterministic components in a series.     

Two-Stage Procedures for Estimating the Difference of Means when the Sampling Cost is Different

Abstract

We suppose that there are two independent normal populations, π₁: N(μ₁, σ²) and π₂: N(μ₂, a ²σ²), where μ₁, μ₂, σ² are unknown but a (0 < a ≤ 1) is known. We suppose that the sampling cost from π₂ is more expensive than that from π₁. We consider estimating Δ = μ₁ ? μ₂ by some appropriately constructed fixed-width confidence interval. We give two types of two-stage procedures denoted by 𝒫₅ and 𝒫₆ for this purpose. Assuming that both two-stage sampling strategies are implementable in some situation, we show that 𝒫₆ compares favorably with 𝒫₅ and suggest implementing 𝒫₆ in practice. We also reaffirm these sentiments with illustrations using a real data set from Mukhopadhyay et al. (2004 Mukhopadhyay , N. , Son , M. S. , and Ko , Y. C. ( 2004 ). A New Two-Stage Sampling Design for Estimating the Maximum Average Time to Flower , Journal of Agricultural, Biological, and Environmental Statistics 9 : 479 – 499 .[Crossref], [Web of Science ®] , [Google Scholar]).     

An exact method for determining the surface of a countercurrent heat exchanger when the tube side coefficient governs and is a parabolic function of temperature

The “Thermal effectiveness-Transfer unit” charts developed by the authors, for the countercurrent heat exchanger, assume that the overall heat transfer coefficient varies as a parabolic function of temperature; their use can lead to greater accuracy in calculating heat transfer areas.     

碳纤维类材料用于电芬顿体系电极的研究现状

电芬顿技术作为先进氧化技术的一种,基于电化学原理间接性地产生·OH自由基,可以高效快速地去除水中的有机污染物。碳纤维类材料因其比表面积大、密度低、耐腐蚀等优点而被常用作电芬顿体系的电极材料。本文首先介绍了电芬顿技术的基本原理,对近年来碳纤维类材料用于电芬顿电极的研究现状进行了归纳总结,分析了碳纤维材料用于电芬顿电极时的改性手段及应用方式。着重分析了其用于电芬顿阴极时的改性机理与改性方式,并指出了其应用优势与局限性。同时也对碳纤维类材料在电芬顿阳极的应用进行了总结。最后,针对碳纤维类材料用于电芬顿体系时的产业化问题、能耗问题、电极的多功能化等问题进行了分析和展望,为碳纤维类材料应用于电芬顿体系的深入研究提供参考。     

REPLACE: a strategy for iterative design of cyclin-binding groove inhibitors

We describe a drug-design strategy termed REPLACE (REplacement with Partial Ligand Alternatives through Computational Enrichment) in which nonpeptidic surrogates for specific determinants of known peptide ligands are identified in silico by using a core peptide-bound protein structure as a design anchor. In the REPLACE application example, we present the effective replacement of two critical binding motifs in a lead protein-protein interaction inhibitor pentapeptide with more druglike phenyltriazole and diphenyl ether groups. These were identified through docking of fragment libraries into the volume of the cyclin-binding groove of CDK2/cyclin A vacated through truncation of the inhibitor peptide-binding determinants. Proof of concept for this strategy was obtained through the generation of potent peptide-small-molecule hybrids and by the confirmation of inhibitor-binding modes in X-ray crystal structures. This method therefore allows nonpeptide fragments to be identified without the requirement for a high-sensitivity binding assay and should be generally applicable in replacing amino acids as individual residues or groups in peptide inhibitors to generate pharmaceutically acceptable lead molecules.     

Modification of epoxy resins for improvement of adhesion: a critical review

Modification of epoxy resins for improvement of adhesion has been the subject of intense research throughout the world. Unlike for thermoplastics, physical blending is not successful for improvement of bond strength and impact strength of epoxy resins. The bond strength of an epoxy resin can be improved only by chemical modification with a suitable flexible modifier. Such chemical modification may either plasticize the epoxy matrix or lead to a two-phase microstructure. Both methods of chemical modifications are discussed critically in the present review.     

等温过程吉布斯函数变化计算公式的另一种推导方法

本文从吉布斯函数的定义式中学生最为熟悉的G=H-TS出发,推导了封闭系统经过等温且非体积功等于零的过程时,其吉布斯函数变化的计算公式,并进一步明确了等温过程吉布斯函数变化每个计算公式的适用条件,从而为教师的备课和学生的自学理清了脉络。教学实践表明:取得了较好的教学效果。     

Dithiobiurets: a novel class of acid corrosion inhibitors for mild steel

The corrosion inhibition behaviour of some substituted dithiobiurets, namely, -1,5-diphenyl-2,4-dithiobiuret (DPDTB), 1-tolyl-5-phenyl-2,4-dithiobiuret (TPDTB), 1-anisidyl-5-phenyl-2,4-dithiobiuret (APDTB), 1-chorophenyl-5-diphenyl-2,4-dithiobiuret (CPDTB) were studied in 1 to 5 M HCl on mild steel. The characteristics of these compounds are explained in terms of factors such as inhibitor concentration, acid concentration, temperature, immersion time and molecular structure. Potentiodynamic polarization and a.c. impedance techniques were used to investigate the inhibition mechanism. Among the compounds studied APDTB exhibited the best performance giving more than 98% inhibition efficiency (IE) in HCl solutions. DPDTB and CPDTB were found to reduce hydrogen permeation through mild steel in HCl solutions. The adsorption of APDTB was also confirmed by Auger electron spectroscopy (AES).     

Chemical synthesis of a dual branched malto-decaose: a potential substrate for alpha-amylases

A convergent block strategy for general use in efficient synthesis of complex alpha-(1-->4)- and alpha-(1-->6)-malto-oligosaccharides is demonstrated with the first chemical synthesis of a malto-oligosaccharide, the decasaccharide 6,6'-bis(alpha-maltosyl)-maltohexaose, with two branch points. Using this chemically defined branched oligosaccharide as a substrate, the cleavage pattern of seven different alpha-amylases were investigated. Alpha-amylases from human saliva, porcine pancreas, barley alpha-amylase 2 and recombinant barley alpha-amylase 1 all hydrolysed the decasaccharide selectively. This resulted in a branched hexasaccharide and a branched tetrasaccharide. Alpha-amylases from Asperagillus oryzae, Bacillus licheniformis and Bacillus sp. cleaved the decasaccharide at two distinct sites, either producing two branched pentasaccharides, or a branched hexasaccharide and a branched tetrasaccharide. In addition, the enzymes were tested on the single-branched octasaccharide 6-alpha-maltosyl-maltohexaose, which was prepared from 6,6'-bis(alpha-maltosyl)-maltohexaose by treatment with malt limit dextrinase. A similar cleavage pattern to that found for the corresponding linear malto-oligosaccharide substrate was observed.     

Improvements of anode properties of aluminium alloys for aluminium primary cell: heat treatment and corrosion inhibitors

Improvements of anode properties of aluminium alloys were attempted for application to a primary dry cell. Heat treatments were investigated chiefly for the alloy A1—3.0Zn—0.13Sn—0.01Ga—0.07Bi(% w/w) derived from high purity aluminium (99.999%). The solution heat treatment (homogenization) of the alloy at 400°C for 4 h presented the best anode properties, ie the faradaic efficiency and the rate of corrosion in 1 M AlCl₃ aqueous solution as the electrolyte. The average grain size diameters of the alloy specimens were also measured after heat treatment at various temperatures. The electrochemical properties were discussed in connection with the structures of alloy. Corrosion inhibitors were investigated for suppression of corrosion rates. Addition of agar and α-amilase to 1 M AlCl₃ significantly reduced the current loss (100 — faradaic efficiency, %) and the rate of corrosion. The alloy mentioned above treated at 400°C (homogenization) combined with agar (2 g l⁻¹) as a corrosion inhibitor gave the best electrochemical properties; the faradaic efficiency 99.8% and the average rate of corrosion 0.008 mg cm⁻² h⁻¹ (short term) and 0.005 mg cm⁻² h⁻¹ (long term).     

The peak-shift method for the description of structural relaxation in glassy materials: a critical review

Nowadays, the glass transition kinetics is most commonly described in terms of the Tool–Narayanaswamy–Moynihan (TNM) model. Evaluation of one of the most prominent features of the structural relaxation motions—the relaxation nonlinearity—was traditionally done using the peak-shift (PS) method. This paper introduces, for the first time, extensive testing of the PS method by means of theoretical simulations for all practically observable types of structural relaxation behavior and all types of glassy/amorphous materials (tested range of the glass transition temperatures: −55 to 1000°C; tested range of the relaxation activation energies: 300–1300 kJ⋅mol⁻¹). For the majority of types of structural relaxation behavior, the PS method tends to slightly overestimate the value of the TNM nonlinearity parameter x (by ∼ 0.05–0.10). In the specific cases of the highly linear behavior (↑ x) combined with a broad distribution of relaxation times, the PS method systematically vastly underestimates the value of x. A new, improved temperature program was proposed for the PS method, eliminating the major intrinsic drawback of the originally proposed version of the PS methodology. In addition, based on the comparison between the theoretically simulated and real-life experimental data, a new approach (based on the characteristic PS dependence shape) was introduced to estimate the width of the relaxation times distribution.