スキップしてメイン コンテンツに移動

投稿

4月, 2016の投稿を表示しています

A motif for reversible nitric oxide interactions in metalloenzymes

Shiyu Zhang , Marie M. Melzer , S. Nermin Sen , Nihan Çelebi-Ölçüm &  Timothy H. Warren Nature Chemistry (2016),  doi:10.1038/nchem.2502 1 Department of Chemistry, Georgetown University, Box 571227, Washington, DC 20057, USA. 2 Department of Chemical Engineering, Yeditepe University, Istanbul 34755, Turkey. 3 Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA. http://www.nature.com/nchem/journal/vaop/ncurrent/full/nchem.2502.html Abstract Nitric oxide ( NO ) participates in numerous biological processes, such as signalling in the respiratory system and vasodilation in the cardiovascular system. Many metal-mediated processes involve direct reaction of  NO  to form a metal–nitrosyl (M–NO), as occurs at the Fe 2+ centres of soluble guanylate cyclase or cytochrome  c  oxidase. However, some copper electron-transfer proteins that bear a type 1 Cu site (His 2 Cu–Cys) reversibly bind  N...

Mechanism of alkene, alkane and alcohol oxidation with H2O2 by an in situ prepared MnII/ pyridine-2-carboxylic acid catalyst

Pattama Saisaha ,  Jia Jia Dong ,  Tim Geert Meinds ,  Johannes W de Boer ,  Ronald Hage ,  Francesco Mecozzi ,  Johann B Kasper , and  Wesley R. Browne ACS Catal. , Just Accepted Manuscript DOI:  10.1021/acscatal.6b00320 Publication Date (Web): April 18, 2016 Copyright © 2016 American Chemical Society http://pubs.acs.org/doi/abs/10.1021/acscatal.6b00320 Abstract The mechanism by which the  Mn (II)/pyridine-2-carboxylic acid catalyzed oxidation of alkenes, alkanes and alcohols with H2O2 proceeds is elucidated using a combination of in-line spectroscopic analysis and product analysis. The equilibrium between ketone cocatalysts, in particular butanedione and H2O2 and a the competing formation of acetic acid is studied and it is shown that the formation of acetic acid is essential in triggering the onset of catalytic activity. The reactions are found to be zero order in both substrate and terminal oxidant and the dependen...

Readily Accessible Bulky Iron Catalysts exhibiting Site Selectivity in the Oxidation of Steroidal Substrates

Authors Dr. David Font, Dr. Mercè Canta, Michela Milan, Olaf Cussó, Dr. Xavi Ribas, Dr. Robertus J. M. Klein Gebbink , Dr. Miquel Costas First published:  5 April 2016 DOI:  10.1002/anie.201600785 Cited by:  0  articles  http://onlinelibrary.wiley.com/doi/10.1002/anie.201600785/full Abstract Bulky iron complexes are described that catalyze the site-selective oxidation of alkyl C−H bonds with hydrogen peroxide under mild conditions. Steric bulk at the iron center is introduced by appending trialkylsilyl groups at the  meta -position of the pyridines in tetradentate aminopyridine ligands, and this effect translates into high product yields, an enhanced preferential oxidation of secondary over tertiary C−H bonds, and the ability to perform site-selective oxidation of methylenic sites in terpenoid and steroidal substrates. Unprecedented site selective oxidat...

Bovine serum albumin–cobalt(II) Schiff base complex hybrid: an efficient artificial metalloenzyme for enantioselective sulfoxidation using hydrogen peroxide

Bovine serum albumin–cobalt( II ) Schiff base complex hybrid: an efficient artificial metalloenzyme for enantioselective sulfoxidation using hydrogen peroxide   Jie Tang , a b    Fuping Huang , a    Yi Wei , a    Hedong Bian , * a c    ...

Chemoselective synthesis of functional homocysteine residues in polypeptides and peptides

Eric G. Gharakhanian a and Timothy J. Deming* ab  a Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA b Department of Bioengineering, University of California, Los Angeles, CA 90095, USA.  http://pubs.rsc.org/en/Content/ArticleLanding/2016/CC/C6CC01253A#!divAbstract http://pubs.rsc.org/en/content/articlepdf/2016/cc/c6cc01253a   Abstract A methodology was developed for efficient, chemoselective transformation of methionine residues into stable, functional homocysteine derivatives. Methionine residues can undergo highly chemoselective alkylation reactions at low pH to yield stable sulfonium ions, which could then be selectively demethylated to give stable alkyl homocysteine residues. This mild, two-step process is chemoselective, efficient, tolerates many functional groups, and provides a means for creation of new functional biopolymers, site-specific peptide tagging, and s...

Conflicting Role of Water in the Activation of H2O2 and the Formation and Reactivity of Non-Heme FeIII–OOH and FeIII–O–FeIII Complexes at Room Temperature

Sandeep K. Padamati , Apparao Draksharapu , Duenpen Unjaroen , and Wesley R. Browne * Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, Faculty of Mathematics and Natural Sciences, University of Groningen , Nijenborgh 4, 9747AG, Groningen, The Netherlands Inorg. Chem. , Article ASAP DOI: 10.1021/acs.inorgchem.5b02976 Publication Date (Web): April 13, 2016 Copyright © 2016 American Chemical Society http://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.5b02976 Abstract The formation of an Fe III –OOH species by reaction of complex 1 ([(MeN3Py)Fe II (CH 3 CN) 2 ] 2+ ) with H 2 O 2 at room temperature is reported and is studied by a combination of UV/vis absorption, EPR, and resonance Raman spectroscopies. The formation of the Fe III –OOH species, and its subsequent conversion to relatively inert Fe III –O–Fe III species, is shown to be highly dependent on the concentration of water, with excess water favoring the formation of ...