1H NMR study of the reactions between carboplatin analogues [Pt(en)(Me-mal-O,O′)] and [Pt(en)(Me2-mal-O,O′)] and various methionine- and histidine-containing peptides under physiologically relevant conditions
摘要:
H-1 NMR spectroscopy was applied to the study the reactions of [Pt(en)(Me-mal-O,O')] and [Pt(en)(Me-2-mal-O,O')] complexes (en is ethylenediamine, Me-mal and Me-2-mal are bidentate coordinated anions of 2-methylmalonic and 2,2-dimethylmalonic acids, respectively) with N-acetylated Ac-L-Met-Gly and Ac-L-Met-L-His-type peptides (Ac-L-Met-L-His, Ac-L-Met-Gly-L-His-GlyNH(2) and Ac-L-Met-Gly-Gly-L-His-Gly). The use of Me-mal and Me2-mal Pt(II) complexes in the above reactions allows convenient monitoring of their biscarboxylate group via methyl peaks by H-1 NMR measurements. All reactions were realized at 37 degrees C with equimolar amounts of the Pt(II) complex and the dipeptide at pH 7.40 in 50 mM phosphate buffer in D2O. In all these reactions the ring-opened Me-mal and Me-2-mal Pt(II) adducts as an intermediate products were detected in solution for more than 48 h. We found that during this time in the reaction with Ac-L-Met-Gly these monodentate bound malonate ligands have been replaced by water molecule leading to the formation of the corresponding aqua Pt(II)-peptide complex which further promotes the regioselective cleavage of the peptide. However, in the reaction with Ac-L-Met-L-His-type peptides a selective intramolecular replacement of these malonate anions by the N3 imidazole nitrogen atom from histidine residue was occurred. This replacement reaction leads to the formation of the S, N3-macrochelate Pt(II)-peptide complex which was shown as very stable and hydrolytically inactive for more than two weeks. (c) 2012 Elsevier B.V. All rights reserved.
1H NMR study of the reactions between carboplatin analogues [Pt(en)(Me-mal-O,O′)] and [Pt(en)(Me2-mal-O,O′)] and various methionine- and histidine-containing peptides under physiologically relevant conditions
作者:Snežana Rajković、Darko P. Ašanin、Marija D. Živković、Miloš I. Djuran
DOI:10.1016/j.ica.2012.11.004
日期:2013.1
H-1 NMR spectroscopy was applied to the study the reactions of [Pt(en)(Me-mal-O,O')] and [Pt(en)(Me-2-mal-O,O')] complexes (en is ethylenediamine, Me-mal and Me-2-mal are bidentate coordinated anions of 2-methylmalonic and 2,2-dimethylmalonic acids, respectively) with N-acetylated Ac-L-Met-Gly and Ac-L-Met-L-His-type peptides (Ac-L-Met-L-His, Ac-L-Met-Gly-L-His-GlyNH(2) and Ac-L-Met-Gly-Gly-L-His-Gly). The use of Me-mal and Me2-mal Pt(II) complexes in the above reactions allows convenient monitoring of their biscarboxylate group via methyl peaks by H-1 NMR measurements. All reactions were realized at 37 degrees C with equimolar amounts of the Pt(II) complex and the dipeptide at pH 7.40 in 50 mM phosphate buffer in D2O. In all these reactions the ring-opened Me-mal and Me-2-mal Pt(II) adducts as an intermediate products were detected in solution for more than 48 h. We found that during this time in the reaction with Ac-L-Met-Gly these monodentate bound malonate ligands have been replaced by water molecule leading to the formation of the corresponding aqua Pt(II)-peptide complex which further promotes the regioselective cleavage of the peptide. However, in the reaction with Ac-L-Met-L-His-type peptides a selective intramolecular replacement of these malonate anions by the N3 imidazole nitrogen atom from histidine residue was occurred. This replacement reaction leads to the formation of the S, N3-macrochelate Pt(II)-peptide complex which was shown as very stable and hydrolytically inactive for more than two weeks. (c) 2012 Elsevier B.V. All rights reserved.
Mutant Malonyl-CoA Synthetases with Altered Specificity for Polyketide Synthase Extender Unit Generation
作者:Irina Koryakina、Gavin J. Williams
DOI:10.1002/cbic.201100383
日期:2011.10.17
saturation mutagenesis followed by colorimetric screening to identify mutant malonyl‐CoA synthetases with altered substrate specificity. One particular mutant displayed a 240‐fold shift in specificity (see graphic). These mutant enzymes will be useful tools for providing extenderunits to probe the activity of polyketidesynthases.