scholarly journals Structural and Spectroscopic Characterization of TPGS Micelles: Disruptive Role of Cyclodextrins and Kinetic Pathways

Langmuir ◽  
2017 ◽  
Vol 33 (19) ◽  
pp. 4737-4747 ◽  
Author(s):  
Joan Puig-Rigall ◽  
Isabelle Grillo ◽  
Cécile A. Dreiss ◽  
Gustavo González-Gaitano
Keyword(s):  
Spectroscopic Characterization

Spectroscopic characterization of free-base hydroxy(arylethynyl)porphyrins in acidic and basic media

2017 ◽  
Vol 21 (10) ◽  
pp. 680-691
Author(s):  
Kaarin K. Evens ◽  
Kathryn E. Splan
Keyword(s):  
Spectroscopic Characterization ◽  
Spectral Features ◽  
Free Base ◽  
Enhanced Absorption ◽  
Spectral Shifts ◽  
Porphyrin Macrocycle ◽  
Show Evidence ◽  
Acidic Conditions

The addition of arylethynyl groups to the porphyrin macrocycle represents an effective strategy with which to enhance the light-harvesting properties of porphyrins. We now extend this modification to arylethynyl porphyrins with two or four [Formula: see text]-hydroxyphenyl substituents. Arylethynyl porphyrins bearing four, but not two, [Formula: see text]-hydroxyphenyl substituents show evidence of aggregation under acidic conditions. Under basic conditions, deprotonation of the peripheral hydroxyphenyl substituents results in substantially red-shifted spectral features and enhanced absorption in the Q-band region. When the hydroxyphenyl groups are appended to the porphyrin macrocylce via the ethynyl spacers, the spectral shifts observed upon deprotonation are significantly enhanced relative to those observed for hydroxyphenylporphyrins, highlighting the role of expanded conjugation in altering porphyrin photophysics.

scholarly journals Spectroscopic Characterization of YedY: The Role of Sulfur Coordination in a Mo(V) Sulfite Oxidase Family Enzyme Form

2009 ◽  
Vol 131 (43) ◽  
pp. 15612-15614 ◽  
Author(s):  
Jing Yang ◽  
Richard Rothery ◽  
Joseph Sempombe ◽  
Joel H. Weiner ◽  
Martin L. Kirk
Keyword(s):  
Spectroscopic Characterization ◽  
Sulfite Oxidase ◽  
Enzyme Form

Cytochrome cbb3 oxidase and bacterial microaerobic metabolism

2002 ◽  
Vol 30 (4) ◽  
pp. 653-658 ◽  
Author(s):  
R. S. Pitcher ◽  
T. Brittain ◽  
N. J. Watmugh
Keyword(s):  
Active Site ◽  
Reduction Potential ◽  
Oxygen Affinity ◽  
Pseudomonas Stutzeri ◽  
Spectroscopic Characterization ◽  
High Oxygen Affinity ◽  
Copper Oxidase ◽  
Reduced State

Cytochrome cbb3 oxidase is a member of the haem-copper oxidase superfamily. It is characterized by its high oxygen affinity, while retaining the ability to pump protons. These attributes are central to its proposed role in bacterial microaerobic metabolism. Recent spectroscopic characterization of both the cytochrome cbb3 oxidase complex from Pseudomonas stutzeri and the dihaem ccoP subunit expressed separately in Escherichia coli has revealed the presence of a low-spin His/His co-ordinated c-type cytochrome. The low midpoint reduction potential of this haem (Em < + 100 mV), together with its unexpected ability to bind CO in the reduced state at the expense of the distal histidine ligand, raises questions about the role of the ccoP subunit in the delivery of electrons to the active site.

The ability of the NiSOD binding loop to chelate zinc(ii): the role of the terminal amino group in the enzymatic functions

2019 ◽  
Vol 48 (18) ◽  
pp. 6217-6227 ◽  
Author(s):  
Gizella Csire ◽  
András Kolozsi ◽  
Tamás Gajda ◽  
Giuseppe Pappalardo ◽  
Katalin Várnagy ◽  
...  
Keyword(s):  
Crucial Role ◽  
Spectroscopic Characterization ◽  
Amino Group ◽  
Amino Groups ◽  
Enzymatic Function ◽  
Terminal Amino ◽  
Binding Loop

Equilibrium and spectroscopic characterization of zinc(ii) complexes with NiSOD related peptides highlights the crucial role of terminal amino groups in the enzymatic function.

Physical, Crystallographic, and Spectroscopic Characterization of a Crystalline Pharmaceutical Hydrate:  Understanding the Role of Water

2006 ◽  
Vol 6 (10) ◽  
pp. 2333-2354 ◽  
Author(s):  
Frederick G. Vogt ◽  
Jeffrey Brum ◽  
Lee M. Katrincic ◽  
Agnes Flach ◽  
Jerome M. Socha ◽  
...  
Keyword(s):  
Spectroscopic Characterization

scholarly journals Spectroscopic characterization of the Co-substituted C-terminal domain of rubredoxin-2

2018 ◽  
Vol 399 (7) ◽  
pp. 787-798
Author(s):  
Lisa M. Galle ◽  
George E. Cutsail III ◽  
Volker Nischwitz ◽  
Serena DeBeer ◽  
Ingrid Span
Keyword(s):  
Metal Binding ◽  
Spectroscopic Characterization ◽  
Paramagnetic Resonance ◽  
Terminal Domain ◽  
Linear Alkanes ◽  
Regioselective Hydroxylation ◽  
Membrane Bound ◽  
X Ray Absorption

Abstract Pseudomonas putida rubredoxin-2 (Rxn2) is an essential member of the alkane hydroxylation pathway and transfers electrons from a reductase to the membrane-bound hydroxylase. The regioselective hydroxylation of linear alkanes is a challenging chemical transformation of great interest for the chemical industry. Herein, we report the preparation and spectroscopic characterization of cobalt-substituted P. putida Rxn2 and a truncated version of the protein consisting of the C-terminal domain of the protein. Our spectroscopic data on the Co-substituted C-terminal domain supports a high-spin Co(II) with a distorted tetrahedral coordination environment. Investigation of the two-domain protein Rxn2 provides insights into the metal-binding properties of the N-terminal domain, the role of which is not well understood so far. Circular dichroism, electron paramagnetic resonance and X-ray absorption spectroscopies support an alternative Co-binding site within the N-terminal domain, which appears to not be relevant in nature. We have shown that chemical reconstitution in the presence of Co leads to incorporation of Co(II) into the active site of the C-terminal domain, but not the N-terminal domain of Rxn2 indicating distinct roles for the two rubredoxin domains.

scholarly journals Heme-thiolate ferryl of aromatic peroxygenase is basic and reactive

2015 ◽  
Vol 112 (12) ◽  
pp. 3686-3691 ◽  
Author(s):  
Xiaoshi Wang ◽  
René Ullrich ◽  
Martin Hofrichter ◽  
John T. Groves
Keyword(s):  
Driving Force ◽  
Spectroscopic Characterization ◽  
Nitroxyl Radicals ◽  
Rapid Mixing ◽  
Bond Scission ◽  
Vis Spectroscopy ◽  
Ph Jump ◽  
Uv Visible

A kinetic and spectroscopic characterization of the ferryl intermediate (APO-II) from APO, the heme-thiolate peroxygenase from Agrocybe aegerita, is described. APO-II was generated by reaction of the ferric enzyme with metachloroperoxybenzoic acid in the presence of nitroxyl radicals and detected with the use of rapid-mixing stopped-flow UV-visible (UV-vis) spectroscopy. The nitroxyl radicals served as selective reductants of APO-I, reacting only slowly with APO-II. APO-II displayed a split Soret UV-vis spectrum (370 nm and 428 nm) characteristic of thiolate ligation. Rapid-mixing, pH-jump spectrophotometry revealed a basic pKa of 10.0 for the FeIV−O−H of APO-II, indicating that APO-II is protonated under typical turnover conditions. Kinetic characterization showed that APO-II is unusually reactive toward a panel of benzylic C−H and phenolic substrates, with second-order rate constants for C−H and O−H bond scission in the range of 10–107 M−1⋅s−1. Our results demonstrate the important role of the axial cysteine ligand in increasing the proton affinity of the ferryl oxygen of APO intermediates, thus providing additional driving force for C−H and O−H bond scission.

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