Electrochemical evaluation of Abelson tyrosine-protein kinase 1 activity and inhibition by imatinib mesylate and danusertib

Abelson tyrosine-protein kinase 1 (ABL1) catalysed phosphorylation involves the addition of a phosphate group from ATP to the tyrosine residue on the substrate abltide. The phosphorylation reactions were carried out by incubating ABL1, ATP and the substrate abltide. Adsorption at the glassy carbon electrode surface in either reaction mixtures or control solutions, followed by differential pulse voltammetry in buffer allowed detection of the variation of abltide tyrosine residue oxidation peak reflecting the occurrence of the phosphorylation reaction. The effect of abltide, ATP and ABL1 concentrations as well as the time course of the phosphorylation reaction were studied. The influence of co-adsorption of ABL1, ATP and phosphorylated abltide was evaluated and the conditions for the electrochemical detection of ABL1-catalysed phosphorylation optimised. The Michaelis–Menten constant for abltide binding K_M ∼ 4.5 μM, turnover number k_cat ∼ 11 s⁻¹ and enzyme efficiency k_cat/K_M ∼ 2.3 s⁻¹ μM⁻¹ were calculated. The inhibition of ABL1 by imatinib mesylate and danusertib was also electrochemically investigated and IC50 values of 0.53 and 0.08 μM determined.     

Synthesis of new 10,11-dihydrodibenzo[a,d]cycloheptene S-thiocarbamate derivatives via a benzylic Newman–Kwart rearrangement

New S-thiocarbamates possessing a 10,11-dihydro-5H-dibenzo[a,d]cycloheptene moiety were obtained unexpectedly in the process of preparing new O-thiocarbamates starting from 5-dibenzosuberol (10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ol) and aroyl-isothiocyanates. These compounds were obtained via a benzylic Newman–Kwart rearrangement mechanism. The structures of the new thiocarbamates were confirmed by elemental analysis, IR, and NMR spectroscopy and by X-ray crystallography.     

Pure In‐Phase Heteronuclear Correlation NMR Experiments

A general NMR approach to provide pure in‐phase (PIP) multiplets in heteronuclear correlation experiments is described. The implementation of a zero‐quantum filter efficiently suppresses any unwanted anti‐phase contributions that usually distort the multiplet pattern of cross‐peaks and can hamper their analysis. The clean pattern obtained in PIP‐HSQMBC experiments is suitable for a direct extraction of coupling constants in resolved signals, for a peak‐fitting process from a reference signal, and for the application of the IPAP technique in non‐resolved multiplets.     

Engineering the Donor Selectivity of D‐Fructose‐6‐Phosphate Aldolase for Biocatalytic Asymmetric Cross‐Aldol Additions of Glycolaldehyde

D ‐Fructose‐6‐phosphate aldolase (FSA) is a unique catalyst for asymmetric cross‐aldol additions of glycolaldehyde. A combination of a structure‐guided approach of saturation mutagenesis, site‐directed mutagenesis, and computational modeling was applied to construct a set of FSA variants that improved the catalytic efficiency towards glycolaldehyde dimerization up to 1800‐fold. A combination of mutations in positions L107, A129, and A165 provided a toolbox of FSA variants that expand the synthetic possibilities towards the preparation of aldose‐like carbohydrate compounds. The new FSA variants were applied as highly efficient catalysts for cross‐aldol additions of glycolaldehyde to N‐carbobenzyloxyaminoaldehydes to furnish between 80–98 % aldol adduct under optimized reaction conditions. Donor competition experiments showed high selectivity for glycolaldehyde relative to dihydroxyacetone or hydroxyacetone. These results demonstrate the exceptional malleability of the active site in FSA, which can be remodeled to accept a wide spectrum of donor and acceptor substrates with high efficiency and selectivity.     

Identification and Quantification of Tocopherols in Vegetable Oils by Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC -     

Quantum automorphism groups of homogeneous graphs

Associated to a finite graph X is its quantum automorphism group G. The main problem is to compute the Poincaré series of G, meaning the series f(z)=1+c₁z+c₂z²+? whose coefficients are multiplicities of 1 into tensor powers of the fundamental representation. In this paper we find a duality between certain quantum groups and planar algebras, which leads to a planar algebra formulation of the problem. Together with some other results, this gives f for all homogeneous graphs having 8 vertices or less.     

Long-range 1H-1H NMR correlation: extending connectivities to remote bonds via an intermediate heterospin

An out-and-stay 2D proton-proton NMR correlation experiment is proposed to detect long-range proton-proton connectivities up to six and seven bonds away. The magnetization flow pathway is based on a consecutive, dual-step J(CH)-transfer mechanism and it allows one to trace out (1)H-(1)H connectivities between protons belonging to different spin systems. This novel experimental scheme will be particularly useful in cases when carbon resonances overlap, providing connectivity information that could not be obtained in a HMBC experiment. The success of the experiment is demonstrated in the structural studies of a wide variety of chemical compounds.     

The Lebesgue decomposition of the free additive convolution of two probability distributions

We prove that the free additive convolution of two Borel probability measures supported on the real line can have a component that is singular continuous with respect to the Lebesgue measure on ${\mathbb{R}}$ only if one of the two measures is a point mass. The density of the absolutely continuous part with respect to the Lebesgue measure is shown to be analytic wherever positive and finite. The atoms of the free additive convolution of Borel probability measures on the real line have been described by Bercovici and Voiculescu in a previous paper.     

Synthesis of C60/[10]CPP-Catenanes by Regioselective,Nanocapsule-Templated Bingel Bis-Addition

The addition of two unsymmetric malonate esters to the Buckminster fullerene C₆₀ can lead to 22 spectroscopically distinguishable isomeric products and therefore represents a formidable synthesis challenge. In this work, we achieve 87 % selectivity for the formation of a single (in,out-trans-3) isomer by combining three approaches: (i) we use a starting material, in which the two malonates are covalently connected (tether approach); (ii) we form the strong supramolecular complex of C₆₀ with the shape-persistent [10]CPP macrocycle (template approach) and (iii) we embed this complex further within a self-assembled nanocapsule (shadow mask approach). Variation of the spacer chain shed light on the limitations of the approach and the ring dynamics in the unusual [2]catenanes were studied in silico with atomistic resolution. This work significantly widens the scope of mechanically interlocked architectures comprising cycloparaphenylenes (CPP).