Rafael Jordan

First photosystem II crystals capable of water oxidation

Oxygen evolution and proton release of crystallised photosystem II core complexes isolated from Synechococcus elongatus were measured. The yields show that the crystals themselves are capable of highly active water oxidation. This opens the possibility for the structural analysis of the outstanding water-oxidising apparatus.

Charge Recombination Between the Reduced Iron-Sulphur Clusters and P700+

Photosystem I (PS I) is a membrane-bound pigment-protein complex, consisting of at least 11 subunits (1). The cofactors which are involved in the electron transfer are located in the PsaA and PsaB subunits (P700, a chlorophyll a dimer, A0 a monomeric chlorophyll a, Al, a phylloquinone and FX, a [4Fe-4S] cluster) and in the PsaC subunit (two additional [4Fe-4S] clusters, FA and FB) (for a recent review see (2)). In this work, the recombination of the flash-induced charge separated pair was studied by transient absorbance spectroscopy under conditions of oxidized and stepwise prereduced [4Fe-4S] cluster to clarify the kinetics of the different recombination reactions. Measurements of the amplitudes of the recombination phases as a function of the potential offer the possibility to determine the midpoint potentials of the first and second reduction of the iron-sulphur clusters at room temperature. In the past, midpoint potentials were mostly measured by EPR at cryogenic temperatures (e.g. 3,4). In addition, the activation energy of the charge recombination between P700+ and (FAFB) has been measured since values described in the literature are contradictory (200 meV in (5) and 460 meV in (6)).

A VCSEL-based miniature laser-self-mixing interferometer with integrated optical and electronic components

It has been previously published how, using two separate Vertical-Cavity-Surface-Emitting-Lasers (VCSELs), a miniature laser-Doppler interferometer can be made for quasi-three-dimensional displacement measurements. For the use in consumer applications as PC-mice, the manufacturing costs of such sensors need to be minimized. This paper describes the fabrication of a low-cost laser-self-mixing sensor by integrating silicon and GaAs components using flip-chip technology. Wafer-scale lens replication on GaAs wafers is used to achieve integrated optics. In this way a sensor was realized without an external lens and that uses only a single GaAs VCSEL crystal, while maintaining its quasi-three-dimensional sensor capabilities.