Deciphering the Effect of Lysine Acetylation on the Misfolding and Aggregation of Human Tau Fragment 171IPAKTPPAPK180 Using Molecular Dynamic Simulation and the Markov State Model

The formation of neurofibrillary tangles (NFT) with β-sheet-rich structure caused by abnormal aggregation of misfolded microtubule-associated protein Tau is a hallmark of tauopathies, including Alzheimer’s Disease. It has been reported that acetylation, especially K174 located in the proline-rich region, can largely promote Tau aggregation. So far, the mechanism of the abnormal acetylation of Tau that affects its misfolding and aggregation is still unclear. Therefore, revealing the effect of acetylation on Tau aggregation could help elucidate the pathogenic mechanism of tauopathies. In this study, molecular dynamics simulation combined with multiple computational analytical methods were performed to reveal the effect of K174 acetylation on the spontaneous aggregation of Tau peptide ¹⁷¹IPAKTPPAPK¹⁸⁰, and the dimerization mechanism as an early stage of the spontaneous aggregation was further specifically analyzed by Markov state model (MSM) analysis. The results showed that both the actual acetylation and the mutation mimicking the acetylated state at K174 induced the aggregation of the studied Tau fragment; however, the effect of actual acetylation on the aggregation was more pronounced. In addition, acetylated K174 plays a major contributing role in forming and stabilizing the antiparallel β-sheet dimer by forming several hydrogen bonds and side chain van der Waals interactions with residues I171, P172, A173 and T175 of the corresponding chain. In brief, this study uncovered the underlying mechanism of Tau peptide aggregation in response to the lysine K174 acetylation, which can deepen our understanding on the pathogenesis of tauopathies.     

Kinetics of catalytic esterification of terephthalic acid with methanol vapour

This paper describes the investigations carried out on the kinetics of the solid-gas reaction between terephthalic acid and methyl alcohol in presence of phosphoric acid as the catalyst. As phosphoric acid itself reacts with the alcohol forming methyl phosphates, the kinetic data obtained have been analysed taking this reaction into account. The rate of formation of monomethyl phosphate has been found to be proportional to the square of the mole fraction of the acid present at any instant. The activation energy involved in this reaction is 11.3 kcal/g mole. The data obtained on terephthalic acid esterification show that; (i) the conversion sharply increases with an increase in the catalyst concentration between 30–35 per cent (w/w), (ii) the ‘shrinking particle’ model, proposed by Levenspiel for solid-gas reactions, can be conveniently adapted to represent the reaction, and (iii) the temperature dependency of the reaction follows the Arrhenius law, with activation energy being 11.5 kcal/g mole.     

Amido-Amine-Based Cationic Gemini Surfactants: Thermal and Interfacial Properties and Interactions with Cationic Polyacrylamide

Experimental studies were conducted to investigate thermal and interfacial properties of two in‐house synthesized amido‐amine‐based cationic gemini surfactants namely: dodecanoic acid [3‐({4‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐butyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐4‐12 ) and dodecanoic acid [3‐({6‐[(3‐dodecanoylamino‐propyl)‐dimethyl‐amino]‐hexyl}‐dimethyl‐amino)‐propyl]‐amide dibromide ( 12‐6‐12 ). Thermogravimetric analysis showed the excellent thermal stability of surfactants and no structural degradation was observed at temperatures up to 250 °C. The long‐term thermal stability of the surfactants was investigated with the aid of spectroscopic techniques such as nuclear magnetic resonance (NMR (¹H and ¹³C) and Fourier transform infrared (FTIR) spectroscopy. Both surfactants were found to be thermally stable, and no changes in structure were observed after aging for 10 days at 90 °C. The interfacial tension of the surfactants was measured at three different temperatures (30, 60, and 80 °C), and the results showed a decrease in interfacial tension with increasing temperature and increasing spacer length of the surfactants. Rheological measurements were used to assess the interactions between the cationic gemini surfactant and cationic polyacrylamide. The addition of cationic surfactant reduced the viscosity and storage modulus of the polymer at low shear rate and frequency due to surfactant–polymer interactions and charge screening. The investigated surfactant–polymer system has great potential in high‐temperature carbonate reservoirs, where conventional anionic surfactants are not recommended due to high adsorption.     

玉米须化学成分研究

将干燥玉米须水煮提取,提取液依次用乙酸乙酯和正丁醇萃取,制得乙酸乙酯和正丁醇提取物,用硅胶柱层析进行分别分离两种提取物得到4个化合物,依据理化性质及波普数据分析,分别鉴定它们的结构为：香草醛（1）、硬脂酸（2）、尿囊素（3）和邻苯二甲酸二异辛酯（4）。其中,化合物1和3为首次从该植物中分离得到。     

Acrylic Homo- and Co-polymers Based on 2, 4-dichlorophenyl Methacrylate and 8-quinolinyl Methacrylate

The monomer 2, 4-dichlorophenyl methacrylate (2,4-DMA) was synthesized from 2, 4-dichlorophenol and characterized by conventional methods. The homopolymers of 2,4-dichlorophenyl methacrylate and its copolymers with 8-quinolinyl methacrylate (8-QMA) in different feed ratio were prepared by free radical polymerization using dimethyl formamide (DMF) as a solvent and 2,2-azobis iso butyronitrile (AIBN) as an initiator. The resulting polymers were characterized by using IR spectroscopy. Reactivity ratios of monomer were evaluated using UV-spectroscopy. Average molecular weights and polydispersity were determined by gel permeation chromatography (GPC). Solution viscosity was also obtained. The thermal analysis was carried out using TGA and DSC. The homo- and co-polymers were also tested for their antimicrobial properties against selected microorganism. The metal ion uptake capacity of synthesized copolymers was estimated by batch equilibration method using different metal ion solution under different experimental conditions. It is observed that due to the presence of pendant ester bound quinoline group, the copolymers are capable of adsorbing cations from their aqueous solution.     

Influence of Distributed Particle Size on the Determination of the Parabolic Rate Constant for Oxidation by the Powder Method

The established analysis for the study of oxidation using powder specimens is based on the assumption of monosized particles. The experiments, however, are conducted on powders with a distributed particle size. Here we present a statistical approach for the calculation of the rate constant for oxidation. The results of the analysis are applied to new data on oxidation studies of dense powders of silicon carbonitride amorphous ceramics. The monosized model requires a wide range of values for the rate constant to fit the short term and the long-term data, leading to considerable ambiguity in the estimate of the parabolic rate constant, k _p, for oxidation. In contrast the statistical model fits over the entire range of data, yielding a much more reliable value for k _p. For example, the monosized approach gave a value in the range 19.7 × 10⁻¹⁸ < k _p < 2.7 × 10⁻¹⁸ m²/s. In contrast, the statistical model yields a specific value of 4.5 × 10⁻¹⁸ m²/s.     

Experimental estimation of the settling velocity and drag coefficient of the hollow cylindrical particles settling in non-Newtonian fluids in an annular channel

The drag coefficient data of particles settling in an annular channel is very much essential for designing different solid–fluid handling equipment, such as the fluidized bed. Experimental settling velocity, wall factor, and drag coefficient data of the hollow-cylinder particle are presented. Carboxymethyl cellulose solution has been used as the working fluid with a flow index of 0.64 ≤ n ≤ 0.91 and a consistency index of 0.31 ≤ K ≤ 1.81. The experimental results covered a wide diameter ratio range (0.14 ≤ d_eq/L ≤ 0.46), hollow cylinder inner to outer diameter ratio (0.2 ≤ d_i/d_o ≤0.8), and Reynolds number (0.05 ≤ Re ≤ 51 and 0.09 ≤ Re_∞ ≤ 55). d_eq, d_i, and d_o are the equivalent inner and outer diameters of the particle, L is the annular gap, and Re and Re_∞ are the Reynolds numbers in the presence and absence of the wall effect, respectively. The wall factor decreased, and the drag coefficient increased with d_eq/L and d_i/d_o ratios. The above parameters declined with the Reynolds number. The hollow cylinder experienced a lesser wall effect than the spherical particles settling in a non-annular channel. In some cases, the wall factor of the hollow cylinder is found to be equal to the spherical particles settling in an annular channel. The developed correlations have successfully predicted the drag coefficients of the hollow cylinder.     

Efficient Chemical and Enzymatic Syntheses of FAD Nucleobase Analogues and Their Analysis as Enzyme Cofactors**

Flavin adenine dinucleotide (FAD) is an essential redox cofactor in cellular metabolism. The organic synthesis of FAD typically involves coupling flavin mononucleotide (FMN) with adenosine monophosphate, however, existing synthesis routes present limitations such as multiple steps, low yields, and/or difficult-to-obtain starting materials. In this study, we report the synthesis of FAD nucleobase analogues with guanine/cytosine/uracil in place of adenine and deoxyadenosine in place of adenosine using chemical and enzymatic approaches with readily available starting materials, achieved in 1–3 steps with moderate yields (10–57 %). We find that the enzymatic route using Methanocaldococcus jannaschii FMN adenylyltransferase (MjFMNAT) is versatile and can produce these FAD analogues in high yields. Further, we demonstrate that Escherichia coli glutathione reductase is capable of binding and using these analogues as cofactors. Finally, we show that FAD nucleobase analogues can be synthesized inside a cell from cellular substrates FMN and nucleoside triphosphates by the heterologous expression of MjFMNAT. This lays the foundation for their use in studying the molecular role of FAD in cellular metabolism and as biorthogonal reagents in biotechnology and synthetic biology.     

Modelling the properties of pigment‐dyed polyester/cotton sheeting fabrics by response surface methodology

The aim of this study was to model the effect of pigment, binder and fixer concentrations on the rubbing fastness, crease recovery, tear strength and stiffness of pigment‐dyed polyester/cotton sheeting fabrics. The design and analysis of experiments were carried out using Minitab^® statistical software according to the central composite design of response surface methodology. It was found that an increase in the binder concentration significantly improves the dry rubbing fastness, crease recovery and stiffness of the fabric, with a corresponding decrease in fabric tear strength, without significantly affecting the wet rubbing fastness. An increase in the fixer concentration significantly improves both the dry and wet rubbing fastness and crease recovery, with a decrease in fabric tear strength and stiffness. The effect of binder and fixer concentrations on crease recovery was not linear and there was significant negative interaction between these factors for dry rubbing fastness. The effect of pigment concentration was not found to be statistically significant for the types and range of concentrations of pigment, binder and fixer used in this study.     

Effect of Absolute Configuration on the Optical and NMR Properties of Oligonucleotides Containing Benzo[a]Pyrene Adducts at N 6 of Deoxyadenosine

For oligonucleotide duplexes derived from trans opening of benzo[a]pyrene diol epoxides (BaP DEs) by the exocyclic N⁶-amino group of deoxyadenosine (dA), the hydrocarbon is intercalated toward the 5′-end of the modified strand when the configuration at the site of attachment of the base to the hydrocarbon (C-10) is R, and toward the 3′-end when this configuration is S. In oligonucleotide 11-mer duplexes modified by BaP DE-1 (benzylic 7-OH and epoxide oxygen cis) and DE-2 (7-OH and epoxide oxygen trans), as well as 7,8,9,10-tetrahydro BaP 9,10-epoxide, 10R adducts had consistently higher (5–9d°C) T_m values than the corresponding 10S adducts. Dodecamer duplexes from the HPRT gene with trans opened 10S (but not those with 10R) BaP DE-2 adducts at either of two adjacent dA residues exhibited blue shifts at ～350 nm at temperatures well below the T_m. We propose that these blue shifts result from a conformation in which the hydrocarbon is not stacked with the DNA bases.