Chl-a triplet quenching by peridinin in H-PCP and organic solvent revealed by step-scan FTIR time-resolved spectroscopy

Triplet-state dynamics in Chl-a/Per mixtures in organic solvent and in native H-PCP were studied by means of step-scan FTIR spectroscopy. A single decay component of 10 μs was observed for the H-PCP triplet, the spectrum of which closely matches the 13 μs component of A-PCP [Alexandre et al., Biophysical Journal 93 (2007) 2118-2128], implying that in H-PCP, as in A-PCP, the peridinin triplet state is shared with Chl-a. In a mixture of Chl-a and Per in THF, TEET from 3Chl-a to 3Per proceeds in 3.5 μs followed by 3Per decay in 7 μs. Using a target analysis procedure, 3Chl-a and 3Per infrared difference spectra were obtained. The specific carbonyl frequencies of 3Per and 3Chl-a in THF confirm our assignment of their co-existence in the infrared spectra of H-PCP and A-PCP.