The feasibility of combining safe permeation enhancers in a mucoadhesive particulate system for the oral delivery of peptide drugs was investigated in this study. Polyelectrolyte complex nanoparticles (NPs) were prepared by ionic interaction of spermine (SPM) with polyacrylic acid (PAA) polymer. Cytotoxicity studies in Caco-2 monolayers revealed the safety of the delivery system in the concentration range used for permeation enhancement. The cellular transport of fluorescein isothiocyanate dextran (FD4) showed higher permeation enhancing profiles of SPM-PAA NPs, as compared to SPM solution or PAA NPs prepared by ionic gelation with MgCl2 (Mg-PAA NPs). These permeation enhancing effects were associated with a reversible decrease in TEER values, suggesting a paracellular permeation pathway by reversible opening of the tight junctions. Furthermore, confocal microscopy results revealed strong association of the NPs prepared using fluorescence labeled PAA to Caco-2 cells. The permeation enhancing properties of SPM-PAA NPs were further evaluated in vivo after oral administration to rats, using FD4 and calcitonin as models of poorly permeating drugs. Confocal microscopy images of rats’ small intestine confirmed previous findings in Caco-2 cells and revealed a strong and prolonged penetration of FD4 from the mucosal to the basolateral side of the intestinal wall. In addition, the proposed NPs were efficient in improving the oral absorption of calcitonin, as evidenced by the significant and prolonged reduction of the blood calcemia in rats.

The utility of wild-type and variant carboxymethylproline synthases for biocatalysis was demonstrated by preparing functionalised 5-, 6- and 7-membered N-heterocycles from amino acid aldehydes and (alkylated) malonyl-coenzyme A derivatives; the N-heterocycles produced were converted to the corresponding bicyclic β-lactams by a carbapenem synthetase.

Formaldetected: Application of 1H- and 1D 13C HSQC NMR spectroscopy methods for monitoring the activity of a 2-oxoglutarate dependent histone Nε-methyllysine demethylase (JMJD2E) enabled the in situ quantitative analysis of the different components of the reaction, including the direct observation of hydrated formaldehyde resulting from enzyme-catalysed demethylation.

L-Glutamate semialdehyde (L-GSA) is an intermediate in biosynthetic pathways including those leading to the carbapenem antibiotics. We describe studies on asymmetric deuteration or hydrogenation of appropriate didehydro-amino acid precursors for the stereoselective synthesis of C-2- and/or C-3-[2H]-labelled L-GSA suitable for use in mechanistic studies. Regioselective deuterium incorporation into the 5-position of L-GSA was achieved using a labelled form of the Schwartz reagent (Cp2Zr2HCl). 4,4-Dideuterated and fully backbone deuterated L-GSAs were prepared. The application of the labelled L-GSA derivatives to biosynthetic studies was exemplified by the chemo-enzymatic preparation of selectively deuterated trans-carboxymethylprolines using two different carboxymethylproline synthases (CarB and ThnE), enzymes that catalyse early steps in the biosynthesis of two carbapenems: (5R)-carbapenem-3-carboxylate and thienamycin, respectively.

Unusual antibiotic biosynthesis enzymes: The observation that formation of trans-carboxymethylproline (t-CMP) and 6-methyl-t-CMP is catalyzed by ThnE from Streptomyces cattleya using glutamate semi-aldehyde and malonyl- or methylmalonyl-CoA implies the need for a C-5 epimerization step in the biosynthesis of thienamycin and reveals the possibility that a methyl group at C-6 might be introduced at an early stage.

Three of a kind: Vicinal tricarbonyl compounds undergo C-C cleavage mediated by ferric ions (see scheme). The observed cleavage of ninhydrin and dehydroascorbic acid has relevance for amino acid detection and the metabolism of vitamin C.