title: Multivariate curve resolution of rapid-scan FTIR difference spectra of quinone photoreduction in bacterial photosynthetic membranes.
abstract: Photosynthetic reaction centres and membranes are systems of particular interest and are often taken as models to investigate the molecular mechanisms of selected bioenergetic reactions. In this work, a multivariate curve resolution by alternating least squares procedure is detailed for resolution of time-resolved difference FTIR spectra probing the evolution of quinone reduction in photosynthetic membranes from Rhodobacter sphaeroides under photoexcitation. For this purpose, different data sets were acquired in the same time range and spectroscopic domain under slightly different experimental conditions. To enable resolution and provide meaningful results the different data sets were arranged in an augmented matrix. This strategy enabled recovery of three different species despite rank-deficiency conditions. It also results in better definition (identity and evolution) of the contributions. From the resolved spectra, the species have been attributed to: 1. the formation of ubiquinol, more precisely the disappearance of Q/appearance of QH(2); 2. conformational change of the protein in the surrounding biological medium; 3. oxidation of diaminodurene, a redox mediator. Because, moreover, results obtained from augmented data sets strategies enable quantitative and qualitative interpretation of concentration profiles, other effects, for example the consequence of repeated light excitation of the same sample, choice of illumination power, or the number of spectra accumulated could be compared and discussed.
authors.affiliation: Laboratoire de Spectrochimie Infrarouge et Raman (LASIR), UMR CNRS 8516, Université des Sciences et Technologies de Lille (USTL), bât C5, 59655 Villeneuve d'Ascq, France.
authors.forename: L
authors.initials: L
authors.lastname: Blanchet
authors.forename: A
authors.initials: A
authors.lastname: Mezzetti
authors.forename: C
authors.initials: C
authors.lastname: Ruckebusch
authors.forename: J-P
authors.initials: JP
authors.lastname: Huvenne
authors.forename: A
authors.initials: A
authors.lastname: de Juan
mesh_terms: D000465:Algorithms; D016227:Benzoquinones / Q000378:metabolism*; D008027:Light; D015999:Multivariate Analysis; D010084:Oxidation-Reduction / Q000528:radiation effects; D010363:Pattern Recognition, Automated / Q000379:methods*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000502:physiology*; D018717:Purple Membrane / Q000502:physiology* / Q000528:radiation effects; D012242:Rhodobacter sphaeroides / Q000502:physiology* / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
chemical_list: D016227:Benzoquinones; D045322:Photosynthetic Reaction Center Complex Proteins; C004532:quinone