Detection of Specific Noncovalent Zinc Finger Peptide–Oligodeoxynucleotide Complexes by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Faster than with conventional solution-phase methods , mass spectrometry can be used to recognize the formation of noncovalent complexes. This is shown by the detection of the specific triple complex between an 18-residue zinc finger peptide from the gag protein p55 of HIV-1, Zn²⁺, and the oligodeoxynucleotide d(TTGTT) by MALDI-MS (see the spectrum). The results also indicate that MALDI mass spectra can qualitatively reflect solution-phase chemistry.     

Inside Cover: Structural and Mechanistic Studies on Substrate and Stereoselectivity of the Indole Monooxygenase VpIndA1: New Avenues for Biocatalytic Epoxidations and Sulfoxidations (Angew. Chem. Int. Ed. 17/2023)

Flavoprotein monooxygenases are a versatile group of enzymes for biocatalytic transformations. Among these, group E monooxygenases (GEMs) catalyze enantioselective epoxidation and sulfoxidation reactions. Here, we describe the crystal structure of an indole monooxygenase from the bacterium Variovorax paradoxus EPS, a GEM designated as VpIndA1. Complex structures with substrates reveal productive binding modes that, in conjunction with force-field calculations and rapid mixing kinetics, reveal the structural basis of substrate and stereoselectivity. Structure-based redesign of the substrate cavity yielded variants with new substrate selectivity (for sulfoxidation of benzyl phenyl sulfide) or with greatly enhanced stereoselectivity (from 35.1 % to 99.8 % ee for production of (1S,2R)-indene oxide). This first determination of the substrate binding mode of GEMs combined with structure-function relationships opens the door for structure-based design of these powerful biocatalysts.     

Reaction between Dichlorophosphines and Azoalkenes: A General Synthesis of 3,4-Dihydro-2H-1,2,3-diazaphosphole Derivatives

The reaction between dichlorophosphines and azoalkenes provides a smooth method for the preparation of 3,4-dihydro-2H-1,2,3-diazaphosphole-3-oxides. When R¹ ≠ H, the cis: trans ratio is strongly dependent on the nature of the R⁴ substituent. Compounds arising from phenylazoalkenes are stable for several months, whereas compounds arising from methylazoalkenes undergo modifications during silica gel chromatography. Trichlorosilane reduction of these oxides gives the corresponding phosphines with retention of configuration. In some cases, this process competes with stereomutation of the starting phosphine oxide. Aryl-substituted phosphines are much more stable than the corresponding alkyl-substituted phosphines.