1. Determination of δ-[L-α-aminoadipyl]-L-cysteinyl-D-valine in cell extracts of Penicillium chrysogenum using ion pair-RP-UPLC-MS/MS
Reza Maleki Seifar, Amit T Deshmukh, Joseph J Heijnen, Walter M van Gulik J Sep Sci. 2012 Jan;35(2):225-30. doi: 10.1002/jssc.201100527.
δ-[L-α-Aminoadipyl]-L-cysteinyl-D-valine (ACV) is a key intermediate in the biosynthesis pathway of penicillins and cephalosporins. Therefore, the accurate quantification of ACV is relevant, e.g. for kinetic studies on the production of these β-lactam antibiotics. However, accurate quantification of ACV is a challenge, because it is an active thiol compound which, upon exposure to air, can easily react with other thiol compounds to form oxidized disulfides. We have found that, during exposure to air, the oxidation of ACV occurs both in aqueous standard solutions as well as in biological samples. Qualitative and quantitative determinations of ACV and the oxidized dimer bis-δ-[L-α-aminoadipyl]-L-cysteinyl-D-valine have been carried out using ion pair reversed-phase ultra high-performance liquid chromatography, hyphenated with tandem mass spectrometry (IP-RP-UPLC-MS/MS) as the analytical platform. We show that by application of tris(2-carboxy-ethyl)phosphine hydrochloride (TCEP) as the reducing reagent, the total amount of ACV can be determined, while using maleimide as derivatizing reagent enables to quantify the free reduced form only.
2. Beta-lactam and aminoglycoside production from streptomycetes
P G Berwick J Appl Bacteriol. 1988 Jan;64(1):9-15. doi: 10.1111/j.1365-2672.1988.tb02424.x.
Streptomyces cattleya, S. fradiae and S. griseus produced different amounts of growth when cultured sequentially through sporulation, vegetative and antibiotic production media. Only S. griseus grew well on all three types of medium. Streptomyces cattleya grew poorly on both sporulation and vegetative media. Growth was 1.6 and 8.0 mg/1/h respectively. For all three species, biomass yield in the final antibiotic production medium was dependent on amount of inoculum. Antibiotic yields were obtained only from production media. Under slow growth conditions L-cysteine and L-valine supplementation stimulated S. cattleya beta-lactam production, giving 1000 micrograms/ml beta-lactam equivalents compared with 45 micrograms/ml beta-lactam equivalents for no supplementation. For aminoglycosides the agar well diffusion bioassay was more sensitive towards the hydrochloride than the neutral salt. Paper chromatography confirmed the main antibiotic classes. RF values for replicate samples indicated aminoglycoside homogeneity and beta-lactam heterogeneity.
3. Synthesis, antioxidative and antiviral activity of hydroxycinnamic acid amides of thiazole containing amino acid
Ivanka Stankova, Kiril Chuchkov, Stoyan Shishkov, Kalina Kostova, Luchia Mukova, Angel S Galabov Amino Acids. 2009 Jul;37(2):383-8. doi: 10.1007/s00726-008-0165-z. Epub 2008 Oct 14.
The synthesis and the biological (antioxidant and antiviral) activities of novel hydroxycinnamic acid amides of a thiazole containing TFA.valine-4-carboxylic acid ethyl ester are reported. The amides have been synthesized from p-coumaric, ferulic and sinapic acids with the corresponding TFA.valine-thiazole-4-carboxylic acid ethyl ester using the coupling reagent N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) and 4-(dimethylamino) pyridine (DMAP) as a catalyst. The antioxidant properties of the newly synthesized amides have been studied for then antioxidative activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH)* test. The newly synthesized compounds have been tested against the replication in vitro of influenza virus A (H3N2) and human herpes virus 1 and 2 (HSV-1 and HSV-2).
