Spectral diffusion and [sup 14]N quadrupole splittings in absorption detected magnetic resonance hole burning spectra of photosynthetic reaction centers

• Published in: The Journal of chemical physics 1994-04, Vol.100:7
• Main Authors: Greis, J.W., Angerhofer, A., Norris, J.R., Scheer, H., Struck, A., von Schuetz, J.U.
• Format: Article
• Language: English
• Subjects: 550200 - Biochemistry; 665100 - Nuclear Techniques in Condensed Matter Physics - (1992-); ABSORPTION SPECTRA; BACTERIA; BASIC BIOLOGICAL SCIENCES; CHEMICAL REACTIONS; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DETECTION; DEUTERATION; EXTRAPOLATION; ISOTOPES; LIGHT NUCLEI; MAGNETIC RESONANCE; MICROORGANISMS; NITROGEN 14; NITROGEN ISOTOPES; NUCLEI; NUMERICAL SOLUTION; ODD-ODD NUCLEI; PHOTOCHEMICAL REACTIONS; PHOTOSYNTHESIS; RESONANCE; RHODOPSEUDOMONAS; SPECTRA; STABLE ISOTOPES; SYNTHESIS
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.467242

Zero field absorption detected magnetic resonance hole burning measurements were performed on photosynthetic reaction centers of the bacteria [ital Rhodobacter] [ital sphaeroides] R26 and [ital Rhodopseudomonas] [ital viridis]. Extrapolation to zero microwave power yielded pseudohomogeneous linewidths of 2.0 MHz for [ital Rhodopseudomonas] [ital viridis], 1.0 and 0.9 MHz for the protonated forms of [ital Rhodobacter] [ital sphaeroides] R26 with and without monomer bacteriochlorophyll exchanged, and 0.25 MHz as an upper limit for fully deuterated reaction centers of [ital Rhodobacter] [ital sphaeroides] R26. The measured linewidths were interpreted as being due to unresolved hyperfine interaction between the nuclear spins and the triplet electron spin, the line shape being determined by spectral diffusion among the nuclei. The difference in linewidths between [ital Rhodobacter] [ital sphaeroides] R26 and [ital Rhodopseudomonas] [ital viridis] is then explained by triplet delocalization on the special pair in the former, and localization on one dimer half on the latter. In the fully deuterated sample, four quadrupole satellites were observed in the hole spectra arising from the eight [sup 14]N nitrogens in the special pair. The quadrupole parameters seem to be very similar for all nitrogens and were determined to [kappa]=1.25[plus minus]0.1 MHz and [eta]=0.9[plus minus]0.1 MHz.