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1. Synthesis and structure of clozapine N-oxide hemi(hydrochloride): an infinite hydrogen-bonded poly[n]catenane

Author

Phillip L. van der Peet, Rohan D. Joyce, Holger Ott, Sebastian M. Marcuccio, Jonathan M. White, and Spencer J. Williams

Subjects
hydrogen bonding, crystal structure, hydrogen-bonding catenation, Crystallography, QD901-999
Abstract

The structure of the title compound, 2C18H19ClN4O·HCl or (CNO)2·HCl (C36H39Cl3N8O2), at 100 K has tetragonal (I4/m) symmetry. The dihedral angle between the benzene rings of the fused ring system of the CNO molecule is 40.08 (6)° and the equivalent angle between the seven-membered ring and its pendant N-oxide ring is 31.14 (7)°. The structure contains a very strong, symmetrical O—H...O hydrogen bond [O...O = 2.434 (2) Å] between two equivalent R3N+—O− moieties, which share a proton lying on a crystallographic twofold rotation axis. These units then form a (CNO)4·(HCl)2 ring by way of two equivalent N—H...Cl hydrogen bonds (Cl− site symmetry m). These rings are catenated into infinite chains propagating along the c-axis direction by way of shape complementarity and directional C—H...N and C—H...π interactions.

Published
2022
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2. Isotope-Coded Maleimide Affinity Tags for Proteomics Applications

Author

Matthew J. Piggott, Mark C. Walkey, Marisa N. Duong, Peter G. Arthur, Adam P. Wdowiak, Rohan D. Joyce, Gareth L. Nealon, and Amber E. Boyatzis

Subjects
Male, Models, Molecular, Proteomics, Protein Conformation, Quantitative proteomics, Biomedical Engineering, Pharmaceutical Science, Muscle Proteins, Bioengineering, 02 engineering and technology, Mass spectrometry, 01 natural sciences, Adduct, Maleimides, chemistry.chemical_compound, Mice, Dogs, Tandem Mass Spectrometry, Animals, Muscle, Skeletal, Maleimide, Pharmacology, Carbon Isotopes, 010405 organic chemistry, Organic Chemistry, 021001 nanoscience & nanotechnology, Combinatorial chemistry, 0104 chemical sciences, chemistry, Gene Expression Regulation, Isotope Labeling, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization, Electrophile, Proteome, Mice, Inbred mdx, 0210 nano-technology, Linker, Biotechnology, Chromatography, Liquid
Abstract

Isotope-coded affinity tags (ICATs) are valuable tools for mass spectrometry-based quantitative proteomics, in particular, for comparison of protein (cysteine-residue) thiol oxidation state in normal, stressed, and diseased tissue. However, the iodoacetamido electrophile used in most commercial ICATs suffers from poor thiol-selectivity and modest rates of adduct formation, which can lead to spurious results. Hence, we designed and synthesized three ICATs containing thiol-selective N-alkylmaleimide electrophiles (isotope-coded maleimide affinity tags = ICMATs) and assessed these as mass spectrometry probes for ratiometric analysis of lysozyme and muscle proteomes. Two ICMAT pairs containing butylene/D8-butylene linkers were effective MS probes, but not ideal for typical proteomics workflows, because peptides bearing these tags frequently did not coelute with HPLC. A switch to a phenylene/13C6-phenylene linker solved this issue without compromising the efficiency of adduct formation.

Published
2021

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