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Summary

Direct resolution of enantiomers of (RS)-ketorolac was achieved by thin-layer chromatography on silica gel plates using enantiomerically pure L-tryptophan, L-valine, L-methionine, and L-histidine as chiral additive in the stationary phase. The solvent system (acetonitrile, methanol water, and chloroform) with different ratios was successful in resolving the enantiomers. Spots were detected by use of iodine vapor. The detection limit was 0.4 µg mL−1 for each enantiomer of (RS)-ketorolac. The native enantiomers were isolated and characterized.

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Abstract  

Radio high pressure liquid chromatography (radio-HPLC) is the method of choice for quality control of radiopharmaceuticals labelled with short lived isotopes. Our preparations of “no carrier added”11C-labelled palmitic acid and L-methionine are both designed to end with a HPLC separation on either silica gel or C-18 reversed phase material. Since the crude reaction mixtures contain milligram amounts of inactive substrate materials, both separations must be carried out at preparative scale. Nevertheless they are performed in less than 10 min. The most critical factor for the separation of11C-palmitic acid from the main by-product pentadecane is the solvent composition: while the11C-L-methionine separation is especially sensitive to pH variations.

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Abstract  

The sulphur-containing proteinaceous amino acids l-cysteine, l-cystine and l-methionine were irradiated in the solid state to a dose of 3.2 MGy. This dose corresponds to that delivered by radionuclide decay in a timescale of 1.05 × 109 years to the organic matter buried at a depth >20 m in comets and asteroids. The purity of the sulphur-containing amino acids was studied by differential scanning calorimetry (DSC) before and after the solid state radiolysis and the preservation of the chirality after the radiolysis was studied by chirooptical methods (optical rotatory dispersion, ORD) and by FT-IR spectroscopy. Although the high radiation dose of 3.2 MGy delivered, all the amino acids studied show a high radiation resistance. The best radiation resistance was offered by l-cysteine. The radiolysis of l-cysteine leads to the formation of l-cystine. The radiation resistance of l-methionine is not at the level of l-cysteine but also l-methionine is able to survive the dose of 3.2 MGy. Furthermore in all cases examined the preservation of chirality after radiolysis was clearly observed by the ORD spectroscopy although a certain level of radioracemization was measured in all cases. The radioracemization is minimal in the case of l-cysteine and is more pronounced in the case of l-methionine. In conclusion, the study shows that the sulphur-containing amino acids can survive for 1.05 × 109 years and, after extrapolation of the data, even to the age of the Solar System i.e. to 4.6 × 109 years.

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A new ligand has been synthesized by anchoring anthracene to l -methionine. The ligand enables easy identification of amino acids on thin-layer chromatography plates by developing distinguishable colors. This paper deals with the detailed synthesis, characterization, and application of the new ligand. Estimation of binding constants of this new ligand with different amino acids are also reported. A theoretical calculation ( Hartree-Fock ) has been performed to investigate interaction of the ligand with the amino acid.

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Abstract  

The method developed for the determination of the optical purity of L-selenomethionine-75Se is based on the conversion of the mixture of L-and D-amino acids into the diastereoisomeric derivatives by reaction with (−)-camphorsulphonyl chloride. The diastereoisomeric derivatives are separated by means of thin layer chromatography. From the ratio of the radioactivities of the two spots on the chromatogram, the optical purity is calculated, and given in % D. For a sample of L-methionine-14C the following value was found: 0.53±0.05 (S.D. of mean, n=7). For a sample of DL-methionine-14C the percentage of D found, was: 48.5±0.5 (S. D. of mean, n=7). Of 30 different samples of L-selenomethionine-75Se the percentages of D-isomer were determined in duplicate. From the 30 differences between duplicates the S. D. of a single measurement is calculated to be 0.2.

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, Petković MŽ, Vasić VM. Mechanism of complex formation between [AuCl 4 ] − and l -methionine. Polyhedron. 2009; 28:593–9.

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, Roles , KA , Wunderlich , B . A possible glass transition in poly( l -methionine) and poly( l -serine) . Polymer . 1993 ; 34 : 2559 – 2563 . 10.1016/0032-3861(93)90589-3 . 21. Pyda

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. Hutchens , JO , Cole , AG , Stout , JW . Heat capacities and entropies of l -cystine and l -methionine. The transition of l -methionine near 305.5K . J Biol Chem . 1964 ; 239 : 591 – 595 . 22

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. 32. Darshan Malhotra , P , Narula , A 2009 K. Effect of structure of diamide–diimide–diamine based on l -methionine on curing behaviour and thermal stability of DGEBA . Ind J Chem

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