The plant growth regulator, abscisic acid (ABA), is synthesized via the oxidative cleavage of an epoxy-carotenoid. Specifically, a double bond is cleaved by molecular oxygen and an aldehyde is formed at the site of cleavage in both products. The Vp14 gene from maize encodes an oxidative cleavage enzyme for ABA biosynthesis and the recombinant VP14 protein catalyzes the cleavage reaction in vitr...

Abstract: Systematic studies on the substituent effect in para substituted Fe(CO)4–pyridine complexes have been studied on the basis of DFT quantum-chemical calculations. The following substituents were taken into consideration: NO2, CN, CHO, F, H, CH3, and OH. Additionally, the Fe–N and Fe–C bonds were characterized on the basis of Atoms in Molecules topological analysis of electron density. I...

Radical induced disulfide bond cleavage in peptides was demonstrated by ultraviolet (UV) radiation of the electrospray ionization (ESI) plume using a low pressure mercury (LP-Hg) lamp. Tandem mass spectrometry and accurate mass measurements confirmed that the primary reaction products were due to disulfide bond cleavage to form thiol (-SH) and sulfinyl radical (-SO˙). Mechanistic studies showed...

The Fe/N/C catalysts have emerged recently as a representative class of non-Pt catalysts for oxygen electrocatalytic reduction, which could have a competitive catalytic performance to Pt. However, the nature of the catalyst remains elusive, especially on the active site structure and the electrocatalytic kinetics. Here we examine two kinds of Fe/N active sites for Fe/N/C catalysts, namely, the ...

We investigate the mechanism of disulfide bond cleavage in gaseous peptide and protein ions initiated by a covalently-attached regiospecific acetyl radical using mass spectrometry (MS). Highly selective S-S bond cleavages with some minor C-S bond cleavages are observed by a single step of collisional activation. We show that even multiple disulfide bonds in intact bovine insulin are fragmented ...

Fragmentation at the Xxx-Pro bond was analyzed for a group of peptide mass spectra that were acquired in a Finnigan ion trap mass spectrometer and were generated from proteins digested by enzymes and identified by the Sequest algorithm. Cleavage with formation of a + b + y ions occurred more readily at the Xxx-Pro bond than at other locations in these peptides, and the importance of this cleava...

Tin-oxo cage ions undergo Sn–C bond cleavage upon (V)UV excitation. Counterions influence further fragmentation, as they form covalent bonds to the cage.

A nonenzymatic digestion technique allows proteins to be well suited for collision-induced dissociation tandem mass spectrometry. This method utilizes microwaves and Dithiothreitol (DTT) to selectively cleave at aspartic acid (D) and disulfide bonds. This microwave digestion technique is reproducible and produces peptides with a shortened sequence length. Insulin I is used in this study to opti...

Abstract Treatment of 1-aryl-2,5-diphenylpyrroles with lithium powder in tetrahydrofuran at 0 °C results the generation corresponding aryllithium reagents through reductive C–N bond cleavage.