Performance Enhancements in Differential Ion Mobility Spectrometry-Mass Spectrometry (DMS-MS) by Using a Modified CaptiveSpray Source

Differential ion mobility spectrometry (DMS) spatially separates ions in the gas phase using the mobility differences of the ions under applied low and high electric fields. The use of DMS as an ion filter (or ion selector) prior to mass spectrometry analysis has been compromised by the limited ion transmission efficiency. This paper reports enhancement of the DMS-MS sensitivity and signal stability using a modified CaptiveSpray? source. In terms of the ion sampling and transmission efficiency, the modified CaptiveSpray source swept ~ 89% of the ions generated by the tapered capillary through the DMS device (compared to ~ 10% with a conventional microspray source). The signal fluctuation improved from 11.7% (relative standard deviation, RSD) with microspray DMS-MS to 3.6% using CaptiveSpray-DMS-MS. Coupling of LC to DMS-MS via the modified CaptiveSpray source was simple and robust. Using DMS as a noise-filtering device, LC-DMS-MS performed better than conventional LC-MS for analyzing a BSA digest standard. Although LC-DMS-MS had a lower sequence coverage (55%), a higher Mascot score (283) was obtained compared to those of LC-MS (sequence coverage 65%; Mascot score 192) under the same elution conditions. The improvement in the confidence of the search result was attributed to the preferential elimination of noise ions.

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The Mesomeric Effect of Thiazolium on non‐Kekulé Diradicals in Pichia stipitis Transketolase

It is theoretically plausible that thiazolium mesomerizes to congeners other than carbene in a low effective dielectric binding site; especially given the energetics and uneven electronegativity of carbene groups. However, such a phenomenon has never been reported. Nine crystal structures of transketolase obtained from Pichia stipitis (TKps) are reported with subatomic resolution, where thiazolium displays an extraordinary ring‐bending effect. The bent thiazolium congeners correlate with non‐Kekulé diradicals because there is no gain or loss of electrons. In conjunction with biophysical and biochemical analyses, it is concluded that ring bending is a result of tautomerization of thiazolium with its non‐ Kekulé diradicals, exclusively in the binding site of TKps. The chemophysical properties of these thiazolium mesomers may account for the great variety of reactivities carried out by thiamine–diphosphate‐containing (ThDP) enzymes. The stability of ThDP in living systems can be regulated by the levels of substrates, and hydration and dehydration, as well as diradical‐mediated oxidative degradation.     

Intramolecular (4+3) Cycloadditions of Pyrroles and Application to the Synthesis of the Core of Class II Galbulimima Alkaloids

The first intramolecular (4+3) cycloaddition of pyrroles with epoxy enolsilanes as the electrophiles was developed and used to generate optically‐enriched cycloadducts containing the nortropane substructure in good yields. Using this pyrrole cycloaddition as the key step, we achieved the asymmetric synthesis of a nortropane compound bearing the BCDEF ring structure common to the Class II galbulimima alkaloids.     

Steered Molecular Dynamics for Investigating the Interactions Between Insulin Receptor Tyrosine Kinase (IRK) and Variants of Protein Tyrosine Phosphatase 1B (PTP1B)

The aim of this study is to use steered molecular dynamics to investigate the dissociation process between IRK and PTP1Bs for wild type and five mutants (consisting of p.D181E, p.D181A, p.Q262A, p.D181A-Y46F, and p.D181A-Q262A). The gained results are observed not only the unbinding mechanism of IRK-PTP1B complexes came from pulling force profile, number of hydrogen bonds, and interaction energy between IRK and PTP1Bs but also described PTP1B’s point mutations could variably change its binding affinity towards IRK. Additionally, the binding free energy calculated by Molecular Mechanics/Poisson-Boltzmann Surface Area (MM-PBSA) is also revealed that electrostatic energy and polar solvation energy mainly made up the binding free energy of PTP1B-IRK complexes.     

A method to improve crystal quality of CZTSSe absorber layer

Journal of Sol-Gel Science and Technology - In this work, a fabrication process of high crystallinity CZTSSe absorber layer is presented. The CZTS structure is firstly prepared by spin-coating...     

Compact quantum groups associated with monoidal functors

We provide a -algebra structure on the bialgebra associated with a monoidal linear -functor. The -algebra obtained in this way is a compact quantum group in the sense of Baaj and Skandalis. We show that the category of finite dimensional unitary corepresentations of this -algebra is equivalent to the given category.

     

Discriminants of cubic curves and determinantal representations

The Ramanujan Journal - The discriminant of a smooth plane cubic curve over the complex numbers can be written as a product of theta functions. This provides an important connection between...     

Conical averagedness and convergence analysis of fixed point algorithms

Journal of Global Optimization - We study a conical extension of averaged nonexpansive operators and the role it plays in convergence analysis of fixed point algorithms. Various properties of...     

Some notes about affine diameters of convex figures

Given a pointx in a convex figureM, let(x) denote the number of all affine diameters ofM passing throughx. It is shown that, for a convex figureM, the following conditions are equivalent.