NDLI: Oxidation triggers extensive conjugation and unusual stabilization of two di-heme dication diradical intermediates: role of bridging group for electronic communication

Content Provider	Royal Society of Chemistry (RSC)
Author	Bhowmik, Susovan Kumar, Amit Dey, Soumyajit Rath, Sankar Prasad Sil, Debangsu
Copyright Year	2016
Abstract	MauG is a diheme enzyme that utilizes two covalently bound c-type hemes to catalyse the biosynthesis of the protein-derived cofactor tryptophan tryptophylquinone. The two hemes are physically separated by 14.5 Å and a hole-hopping mechanism is proposed in which a tryptophan residue located between the hemes undergoes reversible oxidation and reduction to increase the effective electronic coupling element and enhance the rate of reversible electron transfer between the hemes in bis-Fe(IV) MauG. The present work describes the structure and spectroscopic investigation of 2e-oxidations of the synthetic diheme analogs in which two heme centers are covalently connected through a conjugated ethylene bridge that leads to the stabilization of two unusual trans conformations (U and P′ forms) with different and distinct spectroscopic and geometric features. Unlike in MauG, where the two oxidizing equivalents are distributed within the diheme system giving rise to the bis-Fe(IV) redox state, the synthetic analog stabilizes two ferric hemes, each coupled with a porphyrin cation radical, a scenario resembling the binuclear dication diradical complex. Interestingly, charge resonance-transition phenomena are observed here both in 1e and 2e-oxidised species from the same system, which are also clearly distinguishable by their relative position and intensity. Detailed UV-vis-NIR, X-ray, Mössbauer, EPR and 1H NMR spectroscopic investigations as well as variable temperature magnetic studies have unraveled strong electronic communications between two porphyrin π-cation radicals through the bridging ethylene group. The extensive π-conjugation also allows antiferromagnetic coupling between iron(III) centers and porphyrin radical spins of both rings. DFT calculations revealed extended π-conjugation and H-bonding interaction as the major factors in controlling the stability of the conformers.
Starting Page	1212
Ending Page	1223
Page Count	12
File Format	HTM / HTML PDF
ISSN	20416520
Volume Number	7
Issue Number	2
Journal	Chemical Science
DOI	10.1039/c5sc03120f
Language	English
Publisher	Royal Society of Chemistry
Access Restriction	Subscribed
Subject Keyword	Antiferromagnetism Ferric Enzyme EPR Ethylene Cofactor (biochemistry) Tryptophan Redox Ion Dication Tryptophan tryptophylquinone X-ray crystallography Diradical Porphyrin Nuclear magnetic resonance
Content Type	Text
Resource Type	Article
Subject	Chemistry

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

Aromatic amine dehydrogenase, a second tryptophan tryptophylquinone enzyme (1993).

Posttranslational Biosynthesis of the Protein-Derived Cofactor Tryptophan Tryptophylquinone

Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis.

A dimanganese(iii) porphyrin dication diradical and its transformation to a μ-hydroxo porphyrin-oxophlorin heterodimer.

Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis

Tryptophan tryptophylquinone cofactor biogenesis in the aromatic amine dehydrogenase of Alcaligenes faecalis

Dynamics of intramolecular spin exchange interaction of a nitronyl nitroxide diradical in solution and on surfaces

Enzyme Reactivation by Hydrogen Peroxide in Heme-based Tryptophan Dioxygenase

Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis.

Oxidation triggers extensive conjugation and unusual stabilization of two di-heme dication diradical intermediates: role of bridging group for electronic communication

Similar Documents

Aromatic amine dehydrogenase, a second tryptophan tryptophylquinone enzyme (1993).

Posttranslational Biosynthesis of the Protein-Derived Cofactor Tryptophan Tryptophylquinone

Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis.

A dimanganese(iii) porphyrin dication diradical and its transformation to a μ-hydroxo porphyrin-oxophlorin heterodimer.

Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis

Tryptophan tryptophylquinone cofactor biogenesis in the aromatic amine dehydrogenase of Alcaligenes faecalis

Dynamics of intramolecular spin exchange interaction of a nitronyl nitroxide diradical in solution and on surfaces

Enzyme Reactivation by Hydrogen Peroxide in Heme-based Tryptophan Dioxygenase

Diradical intermediate within the context of tryptophan tryptophylquinone biosynthesis.

Oxidation triggers extensive conjugation and unusual stabilization of two di-heme dication diradical intermediates: role of bridging group for electronic communication