Insights into the molecular dynamics of plant light-harvesting proteins in vivo.

To understand physiological processes at the molecular level, new techniques are needed to determine the details of protein structure and dynamics in intact systems. We describe a specific example of such an approach, involving differential analysis of the carotenoid resonance Raman signal in the plant photosynthetic membrane. Carotenoids play important roles in the photosynthetic membrane and are particularly vital to photoprotective regulatory mechanisms. Our methodology selectively revealed the details of associations between specific carotenoid molecules and specific protein binding sites. Changes in the molecular configuration of these cofactors associated with alterations in the physiological state of the photosynthetic system were observed. This approach can be applied to a wide range of complex biological systems, whenever a protein with a light-absorbing cofactor is involved.