PARENT SESSION
Posters P6A Type II reaction centres: Excited state dynamics and donor side. Abstracts (313-346)

Turnover studies using visible and far red light on PSII core samples from higher plants. Paul Smith^*,1, Joseph Hughes², Barry Prince², Elmars Krausz², Sindra Peterson-Arskold³, Ronald Pace¹, ¹ Department of Chemistry, Canberra, ACT, Australia² Research School of Chemistry, Australia³ Research School of Chemistry, Australia

ABSTRACT- We have examined the S State turnover of highly purified, highly active oxygenic PSII Core samples at temperatures between 120 and 260K and under varying light illumination regimes. (PSII Core samples typical character: 33 Chl a and 4.5Mn per RC, Chl a/b ratio > 30, VO2 > 3500micromol O2 per mg chl per hr). Two wavelength regions of illumination were used; green (visible), transmission window 500 to 600nm (excluding FR/NIR), and FR/NIR wavelengths (filters with transmission cut off > 697nm), and FR laser generating laser light between 750nm and 830nm, (wavelength bandwidth 1nm). The FR/NIR light excluded visible light below the high wavelength limit of the chlorophyll a Qy absorbance region. The PSII Core samples were examined under a number of buffer conditions to test cryoprotectant and presence of Quinones/ Quinols. The formation and changes of S2 g4, S2 ML, FeQa and Cyt B559 signals were monitored, with scaling to S2 state formation using green light at 240K (100% S1 to S2 turnover as S2 ML and FeQa-). Signal generation and S State turnover for the different wavelengths for illumination are discussed in terms of redox electron transfer within and through the PSII Core complexes.

KEY WORDS: Manganese, Photosystem II, S State turnover, ESR