Investigating How Organic Solvents Affect Tissue Culture Polystyrene Surfaces through Responses of Mesenchymal Stem Cells

Polymer coating of tissue culture polystyrene (TCPS) surfaces promotes their biofunctionality, which can aid manipulation of cellular functions. However, the effect of the solvent used for polymer coating is yet to be elucidated. In this study, solvent‐treated TCPS surfaces using water, methanol, ethanol, 2‐propanol, and dimethyl sulfoxide are fabricated. Solvent treatment of TCPS surfaces is performed by spreading solvents onto the surfaces and allowing them to dry. Solvent treatment changes the surface roughness and wettability, depending on the kind of solvents. In addition, these surface property changes affected the extension, proliferation, and differentiation of human bone marrow–derived mesenchymal stem cells. These results suggest that solvent selection for polymer coating is crucial in the regulation of cell responses. Further, treatment with an appropriate solvent can result in a more suitable culture environment for modulating cellular functions.     

Hydrogen bond donors and acceptors are generally depolarized in α-helices as revealed by a molecular tailoring approach

Hydrogen-bond (H-bond) interaction energies in α-helices of short alanine peptides were systematically examined by precise density functional theory calculations, followed by a molecular tailoring approach. The contribution of each H-bond interaction in α-helices was estimated in detail from the entire conformation energies, and the results were compared with those in the minimal H-bond models, in which only H-bond donors and acceptors exist with the capping methyl groups. The former interaction energies were always significantly weaker than the latter energies, when the same geometries of the H-bond donors and acceptors were applied. The chemical origin of this phenomenon was investigated by analyzing the differences among the electronic structures of the local peptide backbones of the α-helices and those of the minimal H-bond models. Consequently, we found that the reduced H-bond energy originated from the depolarizations of both the H-bond donor and acceptor groups, due to the repulsive interactions with the neighboring polar peptide groups in the α-helix backbone. The classical force fields provide similar H-bond energies to those in the minimal H-bond models, which ignore the current depolarization effect, and thus they overestimate the actual H-bond energies in α-helices. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.     

Arithmetic functions and the Cauchy product

It is known that under the Dirichlet product, the set of arithmetic functions in several variables becomes a unique factorization domain. A. Zaharescu and M. Zaki proved an analog of the ABC conjecture in this ring and showed that there exists a non-trivial solution to the Fermat equation $$z^n=x^n+y^n$$ ($$n\ge 3$$). It is also known that under the Cauchy product, the set of arithmetic functions becomes a unique factorization domain. In this paper, we consider the ring of arithmetic functions in several variables under the Cauchy product and prove an analog of the ABC conjecture in this ring to show that there exists a non-trivial solution to the Fermat equation $$z^n=x^n+y^n$$ ($$n\ge 3$$).     

Room-Temperature,Metal-Free,and One-Pot Preparation of 2H-Indazoles through a Mills Reaction and Cyclization Sequence

The Mills reaction and cyclization of readily available 2-aminobenzyl alcohols and nitrosobenzenes using thionyl bromide provided 2H-indazoles in up to 88 % yields. In the metal-free process, acetic acid played a crucial role for the both Mills reaction and cyclization. A brominated 2H-indazole could also be obtained through the one-pot sequence.     

Recyclable carbon fiber‐reinforced plastics (CFRP) containing degradable acetal linkages: Synthesis,properties, and chemical recycling

Two epoxy resins containing degradable acetal linkages were synthesized by the reaction of cresol novolak‐type phenolic resin (CN) with vinyl ethers containing a glycidyl group [cyclohexane dimethanol vinyl glycidyl ether (CHDMVG) and 4‐vinyloxybutyl glycidyl ether (VBGE). Carbon fiber‐reinforced plastics (CFRPs) were prepared by heating laminated prepreg sheets with CN‐CHDMVG resin (derived from CN and CHDMVG) and CN‐VBGE resin (derived from CN and VBGE), in which carbon fibers are impregnated with epoxy resins containing curing agents [dicyandiamide (DICY)] and curing accelerator [3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU)]. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs exhibited almost the same tensile strength as the conventional bisphenol‐A‐based CFRPs. CN‐CHDMVG‐based CFRPs and CN‐VBGE‐based CFRPs underwent smooth breakdown with the treatment of hydrochloric acid in tetrahydrofuran at room temperature for 24 h to regenerate strands of carbon fibers. The surface conditions of the recovered carbon fibers had little changes during degradation and recovery processes on the basis of scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The recovered carbon fibers exhibited almost the same tensile strength as virgin carbon fibers and hence would be reused for the production of CFRPs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1052–1059     

Recognition of dicarboxylates in aqueous acetonitrile by a dinuclear zinc(II) complex of 2,2’-binaphthalene-based receptor

Molecular recognition of dicarboxylates by a dinuclear zinc(II) complex of 2,2?-binaphthalene bearing di(2-pyridyl)aminomethyl groups at 8- and 8?-positions ([Zn₂L]⁴⁺) by UV-vis and fluorescence spectral titrations in an aqueous solvent was investigated. In a series of α,ω-dicarboxylate, receptor [Zn₂L]⁴⁺ showed the highest binding affinity for succinate and UV-vis and fluorescence changes were also largest upon the addition of this guest. In a series of phthalate derivatives, phthalate was strongly bound by [Zn₂L]⁴⁺. The characteristic UV-vis and fluorescence changes strongly depend on the dihedral angle of two naphthyl groups of the complex [Zn₂L]⁴⁺· dicarboxylate estimated by spectral titrations and DFT calculations.     

Total synthesis of kehokorins A and B

The total synthesis of a dibenzofuran rhamnoside, kehokorin A, and its aglycone, kehokorin B, was achieved via a route including Suzuki-Miyaura cross-coupling followed by Ullmann ether synthesis to form a dibenzofuran, stepwise bromination at C7 of the dibenzofuran, a second Suzuki-Miyaura cross-coupling to install a 4-methoxyphenyl group at C7, and rhamnosylation.     

Power of isotopic fine structure for unambiguous determination of metabolite elemental compositions: In silico evaluation and metabolomic application

In mass spectrometry (MS)-based metabolomics studies, reference-free identification of metabolites is still a challenging issue. Previously, we demonstrated that the elemental composition (EC) of metabolites could be unambiguously determined using isotopic fine structure, observed by ultrahigh resolution MS, which provided the relative isotopic abundance (RIA) of ¹³C, ¹⁵N, ¹⁸O, and ³⁴S. Herein, we evaluated the efficacy of the RIA for determining ECs based on the MS peaks of 20,258 known metabolites. The metabolites were simulated with a ≤25% error in the isotopic peak area to investigate how the error size effect affected the rate of unambiguous determination of the ECs. The simulation indicated that, in combination with reported constraint rules, the RIA led to unambiguous determination of the ECs for more than 90% of the tested metabolites. It was noteworthy that, in positive ion mode, the process could distinguish alkali metal-adduct ions ([M + Na]⁺ and [M + K]⁺). However, a significant degradation of the EC determination performance was observed when the method was applied to real metabolomic data (mouse liver extracts analyzed by infusion ESI), because of the influence of noise and bias on the RIA. To achieve ideal performance, as indicated in the simulation, we developed an additional method to compensate for bias on the measured ion intensities. The method improved the performance of the calculation, permitting determination of ECs for 72% of the observed peaks. The proposed method is considered a useful starting point for high-throughput identification of metabolites in metabolomic research.     

Chemical investigation of metabolites produced by an endophytic Aspergillus sp. isolated from Limonia acidissima

Endophytic fungi are considered as a good source to produce important secondary metabolites with interesting bioactivities. In a continuation of our studies towards the search for environmentally friendly bioactive compounds from Sri Lankan flora, we investigated the secondary metabolites produced by the endophytic fungi Aspergillus sp. isolated from the seeds of the popular edible fruit Limonia acidissima L. of the family Rutaceae. The pure culture of the Aspergillus sp. was grown on potato dextrose broth media. After 4 weeks fermentation, fungal media were extracted with organic solvents. Chromatographic separation of the fungal extracts over silica gel, Sephadex LH-20 and RP-HPLC furnished flavasperone (1), rubrofusarin B (2), aurasperone A (3), fonsecinone D (4) and aurasperone B (5). Compounds 1–4 showed moderate activities in brine shrimp toxicity assay. This is the first report of the ¹³C NMR data of compounds 4 and 5.     

Method development for the determination of 24S‐hydroxycholesterol in human plasma without derivatization by high‐performance liquid chromatography with tandem mass spectrometry in atmospheric pressure chemical ionization mode

We developed a highly sensitive and specific high‐performance liquid chromatography with tandem mass spectrometry method with an atmospheric pressure chemical ionization interface to determine 24S‐hydroxycholesterol, a major metabolite of cholesterol formed by cytochrome P450 family 46A1, in human plasma without any derivatization step. Phosphate buffered saline including 1% Tween 80 was used as the surrogate matrix for preparation of calibration curves and quality control samples. The saponification process to convert esterified 24S‐hydroxycholesterol to free sterols was optimized, followed by liquid–liquid extraction using hexane. Chromatographic separation of 24S‐hydroxycholesterol from other isobaric endogenous oxysterols was successfully achieved with gradient mobile phase comprised of 0.1% propionic acid and acetonitrile using L‐column2 ODS (2 μm, 2.1 mm id × 150 mm). This assay was capable of determining 24S‐hydroxycholesterol in human plasma (200 μL) ranging from 1 to 100 ng/mL with acceptable intra‐ and inter‐day precision and accuracy. The potential risk of in vitro formation of 24S‐hydroxycholesterol by oxidation from endogenous cholesterol in human plasma was found to be negligible. The stability of 24S‐hydroxycholesterol in relevant solvents and human plasma was confirmed. This method was successfully applied to quantify the plasma concentrations of 24S‐hydroxycholesterol in male and female volunteers.