Håkan Nilsson
PhD Student

M.Sc in molecular biology, Umeå university, Sweden
Home town: Luleå, Sweden

The purpose of my research project is to obtain new knowledge of how substrate water interacts with the manganese complex in photosystem II during the process of oxygen evolution. The manganese complex cycles through five different oxidation steps denoted S 0 , S 1 , S 2 , S 3 , and S 4 for every turn over of this cycle, two water molecules are oxidized to one molecule of oxygen and four protons.

This cycle can be driven stepwise from one S-state to the next S-state by giving activating light flashes. I make use of this intrinsic behaviour of the manganese complex when I determine the kinetics of substrate water exchange. I use membrane inlet mass-spectrometry to measure mass-peaks of unlabeled and labelled oxygen molecules ( 16 O 2 ; 16/18 O 2 ; 18/18 O 2 ). The magnitudes of the resulting O 2 mass-peaks depends of the incubation time between photosystem II and labelled substrate water molecules (H 2 18 O). The exchange kinetics of both substrate waters is determined by plotting mass-peaks obtained from several measurements. I am also carrying out studies on thermodynamics of O-O bond formation.

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