Ultrafast study of 9-diazofluorene: direct observation of the first two singlet states of fluorenylidene.

Ultrafast photolysis of 9-diazofluorene (DAF) produces a broadly absorbing transient within the instrument time resolution (300 fs), which is assigned to an excited state of the diazo compound. The diazo excited state fragments to form fluorenylidene (Fl) in both its lowest energy singlet state (1Fl, 405-430 nm, depending on the solvent) and a higher energy singlet state (370 nm, 1Fl*). The excited singlet carbene has a lifetime of 20.

Time-resolved step-scan Fourier transform infrared spectroscopy of the CO adducts of bovine cytochrome c oxidase and of cytochrome bo(3) from Escherichia coli.

We have used cryogenic difference FTIR and time-resolved step-scan Fourier transform infrared (TR-FTIR) spectroscopies to explore the redox-linked proton-pumping mechanism of heme-copper respiratory oxidases. These techniques are used to probe the structure and dynamics of the heme a(3)-Cu(B) binuclear center and the coupled protein structures in response to the photodissociation of CO from heme Fe and its subsequent binding to and dissociation from Cu(B). Previous cryogenic (80 K) FTIR CO photodissociation difference results were obtained for cytochrome bo(3), the ubiquinol oxidase of Escherichia coli [Puustinen, A.