The authors are grateful toM.Wulff and F. Schotte for early
developments of the absorption spectrometer. We acknowledge
R. Kort, J. Hendriks and K. J. Helliwerf for providing
PYP crystals, and A. Irimia, M. Weik and G. Zaccai for
providing MalDH crystals. We thank M. Weik for fruitful
discussions and Philippe Charrault for technical assistance.
This work was supported by the EU Biotechnology program
BIO4-CT98-0354.