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A TD-DFT study of the photochemistry of urocanic acid in biologically relevant forms and solvent - influence of ionic, rotameric and protomeric state
Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
2001 In: Journal of the American Chemical Society, ISSN 0002-7863, Vol. 123, no 40, 9817- p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2001. Vol. 123, no 40, 9817- p.
Identifiers
URN: urn:nbn:se:su:diva-23380OAI: oai:DiVA.org:su-23380DiVA: diva2:191663
Note
Part of urn:nbn:se:su:diva-261Available from: 2004-10-07 Created: 2004-10-07Bibliographically approved
In thesis
1. Computational chemistry studies of UV induced processes in human skin
Open this publication in new window or tab >>Computational chemistry studies of UV induced processes in human skin
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents and uses the techniques of computational chemistry to explore two different processes induced in human skin by ultraviolet light. The first is the transformation of urocanic acid into a immunosuppressing agent, and the other is the enzymatic action of the 8-oxoguanine glycosylase enzyme.

The photochemistry of urocanic acid is investigated by time-dependent density functional theory. Vertical absorption spectra of the molecule in different forms and environments is assigned and candidate states for the photochemistry at different wavelengths are identified.

Molecular dynamics simulations of urocanic acid in gas phase and aqueous solution reveals considerable flexibility under experimental conditions, particularly for for the cis isomer where competition between intra- and inter-molecular interactions increases flexibility.

A model to explain the observed gas phase photochemistry of urocanic acid is developed and it is shown that a reinterpretation in terms of a mixture between isomers significantly enhances the agreement between theory and experiment , and resolves several peculiarities in the spectrum.

A model for the photochemistry in the aqueous phase of urocanic acid is then developed, in which two excited states governs the efficiency of photoisomerization. The point of entrance into a conical intersection seam is shown to explain the wavelength dependence of photoisomerization quantum yield.

Finally some mechanistic aspects of the DNA repair enzyme 8-oxoguanine glycosylase is investigated with density functional theory. It is found that the critical amino acid of the active site can provide catalytic power in several different manners, and that a recent proposal involving a SN1 type of mechanism seems the most efficient one.

Place, publisher, year, edition, pages
Stockholm: Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2004. 260 p.
Keyword
Photochemistry, Theoretical chemistry, Density functional theory, UV effects, TD-DFT, enzyme catalysis, DNA damage, Molecular dynamics
National Category
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-261 (URN)91-7265-960-2 (ISBN)
Public defence
2004-10-29, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 13:00
Opponent
Supervisors
Available from: 2004-10-07 Created: 2004-10-07Bibliographically approved

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