Author : Sara S. Rocks
Publisher :
ISBN 13 :
Total Pages : 448 pages
Book Rating : 4.:/5 (567 download)
Book Synopsis Modeling Ring Cleaving Dioxygenases by : Sara S. Rocks
Download or read book Modeling Ring Cleaving Dioxygenases written by Sara S. Rocks and published by . This book was released on 2009 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Extradiol catechol dioxygenases (EDOs), which regiospecifically cleave catechols, have been identified as the bottleneck in the catabolism of PCBs. The sensitivity of EDOs to chlorinated substrates has led to extensive studies of the ring cleaving mechanism both in enzyme systems and with synthetic model complexes. The active site of the enzyme contains a mononuclear iron(II) ligated to the enzyme through two histidines and a glutamate, yet no fully characterized iron(II)-catecholate model complexes supported on tridentate ligands have been reported. Unlike the well studied EDOs, hydroquinone cleaving enzymes (HQDOs) have yet to be studied via model chemistry. The active site of HQDOs is proposed to be similar to that of EDOs, however HQDOs prefer chlorinated substrates while EDOs can be mechanistically inactivated by chlorinated substrates. In Chapters 2 and 3, iron(II) complexes of tridentate ligands with N,N,O and N,N,N donor sets were investigated with X-ray crystallography and NMR spectroscopy. The N,N,O donor ligands were labile, forming a mixture of 1:1 and 2:1 ligand:iron complexes in aqueous solution. A series of triaminocyclohexane (TACH) based N,N,N donor ligands that varied by sterics were bound to iron(II), and the 1:1 and 2:1 complexes were evaluated by NMR spectroscopy. When mixed with catecholate, the iron complexes produced NMR silent purple colored products regardless of ligand donor set, steric modulation, iron(II) source or catecholate substitution. An investigation of the purple colored products resulting from mixing a tridentate ligand, iron(II) and catecholate is discussed in Chapter 4. The purple product was determined to contain high-spin iron(II) despite it being NMR silent. Based on UV-visible spectroscopy, the catecholate and N-donor are structural components of the purple material. The formation of the purple product was an inevitable consequence of mixing iron(II) with a tridentate ligand and catecholate. Chapter 5 presents TACH-ligand iron(II) phenolate and chlorophenolate complexes characterized by NMR spectroscopy and in the solid state. The tolylidene substituted TACH ligand thermally isomerized in the presence of iron(II). Preliminary evidence of an iron-chlorine secondary bonding interaction were determined based on solid state structures, which may shed light on the substrate specificity of the hydroquinone dioxygenases"--Leaves vi-vii.
