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pH-dependent electronic and spectroscopic properties of pyridoxine (vitamin B6)
Örebro University, Department of Natural Sciences. (Molekylär biokemi)
(Biofysikalisk och teoretisk kemi)
Örebro University, Department of Natural Sciences. (Molekylär biokemi)ORCID iD: 0000-0003-3315-8835
Örebro University, Department of Natural Sciences. (Biofysikalisk och teoretisk kemi)
2006 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, no 33, p. 16774-16780Article in journal (Refereed) Published
Abstract [en]

The key electronic and spectroscopic properties of vitamin B6 (pyridoxine) and some of its main charged and protonated/deprotonated species are explored using hybrid density functional theory (DFT) methods including polarized solvation models. It is found that the dominant species at low pH is the N1-protonated form and, at high pH, the O3¢-deprotonated compound. Computed and experimental UV-spectra for these species (experimental spectra recorded at pH 1.7 and 11.1, respectively) show a very close resemblance. At pH 4.3, the protonated species dominates, but with onset of the zwitterionic oxo form which is also the dominant species at neutral pH. The computational studies furthermore show that neither a polarized continuum model of the polar aqueous solvent or explicit hydrogen bonding through additional water molecules are sufficient to describe accurately the spectrum at physiological pH. Instead, Na+ and Cl- counterions were required to give a blue-shift of approximately 0.15 eV.

Place, publisher, year, edition, pages
2006. Vol. 110, no 33, p. 16774-16780
Keywords [en]
Electrons, Hydrogen-Ion Concentration, Molecular Structure, Pyridoxine/*chemistry, Quantum Theory, Solvents/chemistry, Spectrum Analysis, Thermodynamics, Vitamin B 6/*chemistry, Vitamin B Complex/chemistry, Water/chemistry
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-3112DOI: 10.1021/jp062800nOAI: oai:DiVA.org:oru-3112DiVA, id: diva2:137028
Available from: 2006-09-21 Created: 2006-09-21 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Vitamin B6 as a potential antioxidant: a study emanating from UV-B-stressed plants
Open this publication in new window or tab >>Vitamin B6 as a potential antioxidant: a study emanating from UV-B-stressed plants
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increased influx of solar UV-B radiation (280-320 nm), due to a decreasing stratospheric ozone layer, impacts severely on plants. Some of the UV-B effects on plants are related to stress induced by produced reactive oxygen species (ROS). Pyridoxine (vitamin B6) has been reported to be a potential quencher of ROS.

Previous studies have shown that the PDX1.3 gene (encoding a key enzyme in vitamin B6 biosynthesis) is up-regulated by UV-B. We showed that this up-regulation also occurs at the protein level in UV-B exposed Col-0 wild-type plants. Studies performed using pdx1 knock-out mutants of Arabidopsis thaliana showed elevated transcripts levels for LHCB1*3 and PR-5 compared with the Col-0 wild-type. The pdx1 knock-out mutants showed an increased sensitivity towards H2O2-stress, but no increased sensitivity towards low dose UV-B-stress.

To study the postulated role of pyridoxine as quencher of ROS in more detail, both theoretical and experimental studies were performed. Theoretical and experimental UV absorption spectra obtained at different protonation/deprotonation states of pyridoxine showed a very close resemblance at low and high pH. However, for the computational studies at physiological pH addition of counterions were required to accurately describe the experimental spectra.

When theoretically studying the reactivity of pyridoxine towards three different ROS, .OH, .OOH and .O2-, the hydroxyl radical (.OH) was shown to be the most reactive species, while the superoxide radical (.O2-) showed no reactivity towards pyridoxine.

In order to study the role of G-proteins in UV-B signal transduction pathways, UV-B irradiated G-protein mutants of Arabidopsis thaliana were studied. The regulation of the PDX1.3 gene was not affected in the G-protein mutants, regardless of the developmental stage of the plant. However, the expression of CHS was affected in the Ga subunit mutants.

Place, publisher, year, edition, pages
Örebro: Örebro universitetsbibliotek, 2006. p. 73
Series
Örebro Studies in Life Science ; 3
Keywords
Arabidopsis, UV-B irradiation, pyridoxine, vitamin B6, ROS
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-625 (URN)91-7668-497-0 (ISBN)
Public defence
2006-10-12, HSL3, Örebro universitet, Örebro, 10:00 (English)
Opponent
Supervisors
Available from: 2006-09-21 Created: 2006-09-18 Last updated: 2017-10-18Bibliographically approved

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Ristilä, MikaelStrid, ÅkeEriksson, Leif A.

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