DMT-MM mediated functionalisation of the non-reducing end of glycosaminoglycans

Efficient functionalisation of the non-reducing end of uronic acid derivatives and glycosaminoglycan-derived disaccharides using peptide coupling has been achieved, mediated by the water-soluble agent DMT-MM.     

Structure and reactivity of the polarised liquid–liquid interface: what we know and what we do not

Charge transfer phenomena at the interface between two immiscible electrolyte solutions (ITIES) are electrochemical reactions taking place in soft media. Owing to their liquid nature, the ITIES shows a large panel of electrochemical reactions including electron transfer reactions, ion transfer reactions, coupled electron–ion transfer reactions or biomimetic redox reactions. Nevertheless, the mechanisms by which these reactions proceed are yet to be fully understood. The goal of this short review is to summarise the work accomplished over the past decades towards the elucidation of the structure and reactivity at the ITIES, highlighting the main questions still to be answered.     

Synthesis and microbial transformation of β-amino nitriles

Rhodococcus equi A4, Rhodococcus erythropolis NCIMB 11540 and Rhodococcus sp. R312 were investigated towards their ability to produce β-amino amides and acids from β-amino nitriles. The microorganisms show comparable trends: five-membered alicyclic 2-amino nitriles were transformed significantly faster than the six-membered compounds and the products of trans-2-amino nitriles (amides and acids) were formed considerably faster than the cis-counterparts (amides). The trans-five membered nitriles gave the amides (1b, 5b) in excellent enantiomeric excess (94-99%), the biotransformation of trans-six membered substrates resulted in the formation of the acid (3c, 7c) in excellent ee (87-99%). The ee's of the cis-compounds were throughout lower. Fifteen new substances were synthesized and characterized in the course of this work.     

An unprecedented tetranuclear niobium aqua ion with a capping mu4-sulfido ligand

The aqueous solution chemistry of niobium is rather unexplored, and well characterized aqua complexes are scarce. In this work, a new niobium aqua ion is obtained upon treatment of Zn-reduced ethanolic solutions of NbCl5 with HCl in the presence of a sulfide source. The red aqua ion, obtained upon cation-exchange chromatography, forms readily the thiocyanate complex which has been crystallized as Cs(4.26)Na(1.74)[Nb4SO5(NCS)10] . 0.33H2O. X-ray crystallography revealed an unprecedented metal-metal bonded tetranuclear Nb4(mu4-S)(mu2-O)5(4+) core with a capping mu4-S ligand.     

NKT cell-dependent glycolipid–peptide vaccines with potent anti-tumour activity

It is known that T cells can eliminate tumour cells through recognition of unique or aberrantly expressed antigens presented as peptide epitopes by major histocompatibility complex (MHC) molecules on the tumour cell surface. With recent advances in defining tumour-associated antigens, it should now be possible to devise therapeutic vaccines that expand specific populations of anti-tumour T cells. However there remains a need to develop simpler efficacious synthetic vaccines that possess clinical utility. We present here the synthesis and analysis of vaccines based on conjugation of MHC-binding peptide epitopes to α-galactosylceramide, a glycolipid presented by the nonpolymorphic antigen-presenting molecule CD1d to provoke the stimulatory activity of type I natural killer T (NKT) cells. The chemical design incorporates an enzymatically cleavable linker that effects controlled release of the active components in vivo. Chemical and biological analysis of different linkages with different enzymatic targets enabled selection of a synthetic vaccine construct with potent therapeutic anti-tumour activity in mice, and marked in vitro activity in human blood.     

Advances in photolithographically fabricated ENFET membranes

A photolithographically fabricated membrane for enzyme immobilisation based on an Ion Sensitive Field Effect Transistor (ISFET) is described. The preparation of an Enzyme-FET (ENFET) containing urease was successful. The ENFET has been used for the determination of urea and pesticides; this depends on the chosen enzyme level in the membrane and can be employed in a flow-injection system. The urea sensitive sensor (high enzyme load) has a wide linear range (1–500 mmol/l) a fast response (t₉₅=20 s) and a lifetime greater than 30 days. The application of this sensor to the determination of urea in the waste water from a fertilizer plant and in blood serum is discussed. The second sensor (low enzyme level) was able to detect pesticides in water based on the inhibition of urease. The detection limit was found to be 0.1 µg/l for Carbofuran (10 minutes incubation time, without preconcentration).     

Online LC-MS-MS process monitoring for optimization of biological treatment of wastewater containing azo dye concentrates

A biological high-performance treatment process comprising two 40-L reactor compartments has been developed for purification and decoloration of concentrated textile wastewater containing up to 15 g L⁻¹ reactive dyestuff. The decoloration rate of 95% meets the requirements of German legislation for textile wastewater treatment. Successful process development and optimization was achieved by use of high-performance liquid chromatography, with diode-array and electrospray tandem mass spectrometric (LC-ESI-MS-MS) detection, coupled with inline microfiltration membrane-sampling devices, applied online to bioreactors as a process analytical tool for the first time. The optimum process performance was found by correlation of dye and decoloration product-specific concentrations with summary properties such as redox potential and dissolved oxygen content. Details of the degradation and decoloration mechanism for the azo dye reactive black 5 was revealed by using mass spectrometry for structure elucidation.