Experimental and calculated infrared spectra of disubstituted naphthoquinones
Journal Article
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· Spectrochimica Acta. Part A. Molecular and Biomolecular Spectroscopy
- Georgia State University, Atlanta, GA (United States); OSTI
- Georgia State University, Atlanta, GA (United States)
In recent years there has been interest in incorporating substituted 1,4-naphthoquinones (NQs) into the A1 binding site in photosystem I (PSI) photosynthetic protein complexes. This interest in part stems from the considerably altered bioenergetics of electron transfer that occur in PSI with such substitutions. Time resolved FTIR studies of PSI complexes with disubstituted NQs incorporated have and currently are being undertaken, and with this in mind it is worth considering FTIR absorption spectra of these disubstituted NQs in solution. Here we present FTIR absorbance spectra for 2-bromo-3-methyl-1,4-naphthoquinone (BrMeNQ), 2-chloromethyl-3-methyl-1,4-naphthoquinone (CMMeNQ) and 2-ethylthio-3-methyl-1,4-naphthoquinone (ETMeNQ) in tetrahydrofuran (THF). The FTIR spectra of these di-substituted naphthoquinones (NQs) were compared to FTIR spectra of 2-methyl-3-phytyl-1,4-naphthoquinone [phylloquinone (PhQ)], 2,3-dimethyl-1,4-naphthoquinone (DMNQ), and 2-methyl-1,4-naphthoquinone (2MNQ). To aid in the assignment of bands in the experimental spectra, density functional theory (DFT) based vibrational frequency calculations for all the substituted NQs in solution were undertaken. The calculated and experimental spectra agree well. By calculating normal mode potential energy distributions, unambiguous quantitative band assignments were made. The calculated and experimental spectra together make predictions about what may be observable in time resolved FTIR difference spectra obtained using PSI with the different NQs incorporated. As a result, time resolved FTIR difference spectra are presented that support these predictions.
- Research Organization:
- Georgia State University, Atlanta, GA (United States)
- Sponsoring Organization:
- National Science Foundation Major Research Instrumentation (MRI); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0017937
- OSTI ID:
- 1977620
- Journal Information:
- Spectrochimica Acta. Part A. Molecular and Biomolecular Spectroscopy, Journal Name: Spectrochimica Acta. Part A. Molecular and Biomolecular Spectroscopy Journal Issue: C Vol. 268; ISSN 1386-1425
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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Tue Aug 07 00:00:00 EDT 1990
· Biochemistry; (USA)
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OSTI ID:6086533