An Easy Route to Aziridine Ketones and Carbinols

N,N-Dimethylaziridine-2-carboxamides react with organolithium reagents yielding 2-aziridinylketones. The reaction with one equivalent of organolithium compound is selective to amide carbonyl at a low (−78 °C) temperature. These ketones, in reaction with organolithium reagents, give symmetrical and unsymmetrical aziridinyl carbinols. The usage of excess phenyllithium may serve as a special N-Boc-protecting group cleavage method for acid-sensitive substrates.

Improving the Identification and Coverage of Plant Transmembrane Proteins in Medicago Using Bottom–Up Proteomics

Plant transmembrane proteins (TMPs) are essential for normal cellular homeostasis, nutrient exchange, and responses to environmental cues. Commonly used bottom–up proteomic approaches fail to identify a broad coverage of peptide fragments derived from TMPs. Here, we used mass spectrometry (MS) to compare the effectiveness of two solubilization and protein cleavage methods to identify shoot-derived TMPs from the legume Medicago. We compared a urea solubilization, trypsin Lys-C (UR-TLC) cleavage method to a formic acid solubilization, cyanogen bromide and trypsin Lys-C (FA-CTLC) cleavage method. We assessed the effectiveness of these methods by (i) comparing total protein identifications, (ii) determining how many TMPs were identified, and (iii) defining how many peptides incorporate all, or part, of transmembrane domains (TMD) sequences. The results show that the FA-CTLC method identified nine-fold more TMDs, and enriched more hydrophobic TMPs than the UR-TLC method. FA-CTLC identified more TMPs, particularly transporters, whereas UR-TLC preferentially identified TMPs with one TMD, particularly signaling proteins. The results suggest that combining plant membrane purification techniques with both the FA-CTLC and UR-TLC methods will achieve a more complete identification and coverage of TMPs.

Elucidation of LCC bonding sites via γ-TTSA lignin degradation: crude milled wood lignin (MWL) from Eucalyptus globulus for enrichment of lignin xylan linkages and their HSQC-NMR characterization

The selective lignin degradation in a LCC was proceeded with the γ-TTSA method, which is a selective cleavage method for β-O-4 linkages in lignins, in order to obtain more precise information concerning LCC bonding sites. To this purpose, crude MWL from Eucalyptus globulus, containing lignin and xylan, was treated by the γ-TTSA method. This approach consists of four steps: (1) γ-tosylation, (2) thioetherification, (3) sulfonylation, and (4) mild alkali treatment. The degradation products were extracted consecutively with Et2O, EtOAc, and THF for the lignin removal, and thus the residue was enriched in LCCs. The residue was characterized by HSQC-NMR. Results indicated that the residue contained xylan and β-β substructures, although lignin was degraded. It can be concluded that the β-β substructures play an important role in the bonding sites between lignin and xylan of Eucalyptus globulus.