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mmblum

mmblum has written 10 posts for Blum Scientific

Adducts of nerve agents in phosphate buffer and their hydrolysis

After our publication on the formation of buffer adducts of G-type nerve agents with buffer compounds like TRIS, TES or HEPES we now report in a new publication in the journal Toxicology Letters the formation of pyrophosphate-like adducts of Gagents with phosphate buffer. In contrast to the phosphodiesters formed for example with TRIS, the phosphate adducts are not resistant to hydrolysis. Their hydrolysis at pH 7.4 is slow and follows a pseudo-0th order kinetic. This leads to a complex mixture of phosphorus containing species in solution with changing concentrations over time. Therefore we recommend to avoid the use of phosphate buffer for analytical applications with G-type nerve agents.

Characterization of the catalytic calcium binding-site in DFPase and comparison with other beta-propeller enzymes

The catalytic calcium binding-site of the enzymes DFPase displays remarkable similarities to metal binding sites in structurally related proteins like Paraoxonase (PON1), Drug Resistance Protein 35 (Drp35) from S. aureus or the Gluconolactonase XC5397 from Xanthomonas campestris. DFPase mutants targeting calcium binding residues and their structural characterization allow new insights with respect to metal binding and catalytic activity. The results are described in a new publication in Chemico-Biological Interactions (CBI). The article is part of a Special Issue of CBI on the occasion of the 10th International Meeting on Cholinesterases, which took place in Croatia in September 2009.

Stable adducts of nerve agents with buffer compounds like TRIS and HEPES

A new publication in the Journal of Chromatography B describes the formation of stable adducts of nerve agents like Sarin, Soman or Cyclosarin and common buffer compounds like TRIS,TES or HEPES. The molecular structure of the adducts was determined by LC-ESI-MS/MS and NMR spectroscopy. They were found to be phosphodiesters (“O-adducts”). Alternative buffering compounds for the work with warfare agents are proposed.

Reaction monitoring with 1H-31P HSQC NMR spectroscopy

A new publication in Analytical and Bioanalytical chemistry describes the use of 1H-31P HSQC NMR spectroscopy to monitor the degradation of highly toxic organophosphorus compounds by the enzyme DFPase.The method can be used for methylphosphonates, a group of compounds including nerve agents sarin (GB), soman (GD), cyclosarin (GF) and also VX. The limit of quantitation (LOQ) of the method is around 100 μM when using a 400 MHz NMR spectrometer.

“Research Highlight” in Nature Chemistry

Our recently published article in JACS on engineering enantioselectivity in DFPase is now a “Research Highlight” in Nature Chemistry. The article is publicly available but a nature account is required.

Reversed Enantioselectivity of DFPase by Rational Design

Based on structural and mechanistic knowledge, mutants of the phosphotriesterase enzmye DFPase were created that reverse the enantioselectivity of the enzyme from the less toxic to the more toxic stereoisomer of G-type nerve agents. The mutants not only feature a reversed enantioselectivity but also increased enzymatic activity compared to the wildtype. The results are described in a new paper published in the Journal of the American Chemical Society (JACS).

Cited in Chemistry World

“Chemistry World” a publication of the Royal Society of Chemistry in the UK reported on a recently published article in JACS about the decontamination of sulfur mustard in microemulsions by oxidative chemistry. I was asked to comment on this article. A few lines managed to get into the ChemWorld coverage, which you can find here.

The Fish and the Venom

The German newspaper “Frankfurter Rundschau” published an article about DFPase and our neutron structure with the title “Der Fisch und das Gift” (The Fish and the Venom). The article can be found here.

Neutron Structure of the Enzyme DFPase

A new publication in the journal Proceedings of the National Academy of Sciences of the USA (PNAS) describes the neutron diffraction structure of the enzyme DFPase. Neutron diffraction allows the visualization of hydrogen atoms in protein structures and thus the determination of protonation states and orientations of solvent water molecules. The results of the study confirm the proposed reaction mechanism for DFPase and permit the directed introduction of modifications to the enzyme by mutagenesis to enhance both turnover rates and substrate diversity.

Reaction Monitoring with FTIR Spectroscopy

A new publication describes the use of in-situ FTIR spectroscopy to monitor the degradation of highly toxic organophosphorus compounds by the enzyme DFPase. The use of Attenuated Total Reflexion (ATR) allows direct meassurements in the reaction vessel without the need for cuvettes. In comparison to established methods the total reaction volume can be significantly reduced, which also leads to a substantial reduction in the required ammount of toxic substrate and therefore to an increase in work safety.