Chirality and Template‐Mediated Induction of Helical Preferences in Achiral β‐Peptides

This study describes chirality‐ or template‐mediated helical induction in achiral β‐peptides for the first time. A strategy of end capping β‐peptides derived from β‐hGly (the smallest achiral β‐amino acid) with a chiral β‐amino acid that possesses a carbohydrate side chain (β‐Caa; C‐linked carbo β‐amino acid) or a small, robust helical template derived from β‐Caas, was adopted to investigate folding propensity. A single chiral (R)‐β‐Caa residue at the C‐ or N‐terminus in these oligomers led to a preponderance of right‐handed 12/10‐helical folds, which was reiterated more strongly in peptides capped at both the C‐ and N‐terminus. Likewise, the presence of a template (a 12/10‐helical trimer) at both the C‐ and N‐terminus resulted in a very robust helix. The propagation of the helical fold and its sustenance was found in a homo‐oligomeric sequence with as many as seven β‐hGly residues. In both cases, the induction of helicity was stronger from the N terminus, whereas an anchor at the C terminus resulted in reduced helical propensity. Although these oligomers have been theoretically predicted to favor a 12/10‐mixed helix in apolar solvents, this study provides the first experimental evidence for their existence. Diastereotopicity was found in both the methylene groups of the β‐hGly moieties due to chirality. Additionally, the β‐hGly units have shown split behavior in the conformational space to accommodate the 12/10‐helix. Thus, end capping to assist chiralty‐ or template‐mediated helical induction and stabilization in achiral β‐peptides is a very attractive strategy.     

Dissecting heterogeneous molecular chaperone complexes using a mass spectrum deconvolution approach

Small heat-shock proteins (sHSPs) are molecular chaperones that prevent irreversible aggregation through binding nonnative target proteins. Due to their heterogeneity, these sHSP:target complexes remain poorly understood. We present a nanoelectrospray mass spectrometry analysis algorithm for estimating the distribution of stoichiometries comprising a polydisperse ensemble of oligomers. We thus elucidate the organization of complexes formed between sHSPs and different target proteins. We find that binding is mass dependent, with the resultant complexes reflecting the native quaternary architecture of the target, indicating that protection happens early in the denaturation. Our data therefore explain the apparent paradox of how variable complex morphologies result from the generic mechanism of protection afforded by sHSPs. Our approach is applicable to a range of polydisperse proteins and provides a means for the automated and accurate interpretation of mass spectra derived from heterogeneous protein assemblies.     

Simultaneous Chemo/Enantioseparation and Assay of R-(+)-Rabeprazole and Related Impurities in Pharmaceutical Formulations

Simultaneous chiral and chemoseparation of R-(+)-rabeprazole and related (enantio)impurities was achieved on a cellulose tris-(3,5-dichlorophenylcarbamate) stationary phase chemically bonded to silica gel (Chiralpak IC). A gradient elution was applied in the reverse-phase separation mode. The mobile phase consisted of a mixture of acetonitrile and aqueous phosphate buffer at pH 7. The other operational parameters were flow rate of 1 mL min⁻¹, column temperature of 35 °C and ultraviolet (UV) detection at 282 nm. Quantification limits for R-(+)-rabeprazole and the related impurities ranged in the interval of 0.02–0.03 %. Linear response intervals of 0.02–0.66 % were obtained with UV detection. Validation of the proposed method was achieved according to current regulations in force. For better understanding of the R-(+)-rabeprazole impurity profile, (+)-EMS/MS and MS/MS detection were also used.

     

Microwave-assisted neat synthesis of α-aminophosphonate/phosphinate derivatives of 2-(2-aminophenyl)benzothiazole as potent antimicrobial and antioxidant agents

A series of diethyl/ethylphenyl {2-(benzo[d]thiazol-2-yl)phenylamino}phosphonates and phosphinates were synthesized under microwave irradiation and neat conditions via Kabachnik-Fields reaction in high yields (80%–93%). The compounds were screened for antimicrobial and antioxidant properties. A few compounds showed effective antibacterial and antifungal activities at MIC value 12.5 μg/mL as compared with the standard at MIC value 6.25 μg/mL.     

Stark constant of ar I lines

Summary The half-width of Ar I lines, obtained by photoelectric method, is measured at different values of plasma electron temperature for an arc discharge. Good agreement is obtained in comparison with other reported results. The Stark constant is calculated for narrow and wide argon lines using two empirical formulae. Comparison with other reported data indicates that these formulae give results which are in good agreement with the recent publication by Windholz.

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Riassunto La semiampiezza delle linee I di Ar ottenuta col metodo fotoelettrico, si misura a differenti valori di temperature del plasma di elettroni per una scarica ad arco. Si ottiene un buon accordo in confronto ad altri risultati riportati. La costante di Stark si calcola per linee dell'argon strette e larghe usando due formule empiriche. Il paragone con altri dati riportati indica che queste formule danno risultati che sono in buon accordo con la recente pubblicazione di Windholz.

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Резюме При различных злектрнных температурах плазмы для разряда электрической дуги была измерена полуширина линий ArI, полченных фотоэктрическим методом. Получается хорошее сорласие с другими орубикованными резльтатами. Постоянная Штарка вычисляется для узких и широкш линий аргона, исппльзуя две эмпирических формлы. Сравнение с имеющимися данными показывает, что эти формулы дают результаты, которые хорошо согласуются с недавней Публикацей Вндгольца.

     

Design,synthesis and biological evaluation of substituted 2-amino-1,3-thiazine derivatives as antituberculosis and anti-cancer agents

A series of substituted 2-amino-1,3-thiazines were synthesized as amides (9a–9i), carbamates (9j–9m), sulfonamides (9n–9o) and urea derivatives (9p–9q) by treating the compound 7 with acid chlorides (8a–8i), chloroformates (8j–8m), sulfonyl chlorides (8n–8o) and isocyanates (8p–8q) respectively. The synthesized compounds (9a–9q) were screened for antituberculosis activity against Mycobacterium tuberculosis H₃₇Rv ATCC 27294 and the results show that some of these derivatives possess good activity against Mycobacterium tuberculosis H₃₇Rv ATCC 27294. A few also display promising cytotoxic activity against human breast cancer MCF-7 and human esophageal cancer EC-9706 cell lines. Regarding both biological profiles 9b, 9m and 9h are the most active for anti-cancer, anti-TB activity.     

Discrete optimization in partially ordered sets

The primary aim of this article is to resolve a global optimization problem in the setting of a partially ordered set that is equipped with a metric. Indeed, given non-empty subsets A and B of a partially ordered set that is endowed with a metric, and a non-self mapping ${S : A \longrightarrow B}$ , this paper discusses the existence of an optimal approximate solution, designated as a best proximity point of the mapping S, to the equation Sx?=?x, where S is a proximally increasing, ordered proximal contraction. An algorithm for determining such an optimal approximate solution is furnished. Further, the result established in this paper realizes an interesting fixed point theorem in the setting of partially ordered set as a special case.     

Common best proximity points: global minimization of multi-objective functions

Given non-empty subsets A and B of a metric space, let ${S{:}A{\longrightarrow} B}$ and ${T {:}A{\longrightarrow} B}$ be non-self mappings. Due to the fact that S and T are non-self mappings, the equations Sx = x and Tx = x are likely to have no common solution, known as a common fixed point of the mappings S and T. Consequently, when there is no common solution, it is speculated to determine an element x that is in close proximity to Sx and Tx in the sense that d(x, Sx) and d(x, Tx) are minimum. As a matter of fact, common best proximity point theorems inspect the existence of such optimal approximate solutions, called common best proximity points, to the equations Sx = x and Tx = x in the case that there is no common solution. It is highlighted that the real valued functions ${x{\longrightarrow}d(x, Sx)}$ and ${x{\longrightarrow}d(x, Tx)}$ assess the degree of the error involved for any common approximate solution of the equations Sx = x and Tx = x. Considering the fact that, given any element x in A, the distance between x and Sx, and the distance between x and Tx are at least d(A, B), a common best proximity point theorem affirms global minimum of both functions ${x{\longrightarrow}d(x, Sx)}$ and ${x{\longrightarrow}d(x, Tx)}$ by imposing a common approximate solution of the equations Sx = x and Tx = x to satisfy the constraint that d(x, Sx) = d(x, Tx) = d(A, B). The purpose of this article is to derive a common best proximity point theorem for proximally commuting non-self mappings, thereby producing common optimal approximate solutions of certain simultaneous fixed point equations in the event there is no common solution.     

Hollow Reticular Shaped Highly Ordered Rice Husk Carbon for the Simultaneous Determination of Dopamine and Uric Acid

We have prepared activated porous carbon material through simple pyrolysis method from rice husks (rhAC) for sensitive detection of dopamine (DA) and uric acid (UA). The prepared rhAC material was thoroughly characterized using various spectroscopic, microscopic, and electroanalytical techniques. Analysis of the voltammetric data showed that the analytes followed a first order reaction kinetics while following a 2e^?/2H⁺ transfer process. We have discussed the possible oxidation mechanism for the analytes based on the results from our experimental analysis. The rhAC_GCE sensor was tested for interference, reproducibility, and stability. The sensor was also tested to evaluate its applicability in real life.