CooA is a dimeric CO-sensing heme protein from Rhodospirillum rubrum. The heme iron in reduced CooA is six-coordinate; the axial ligands are His-77 and Pro-2. CO displaces Pro-2 and induces a conformation change that allows CooA to bind DNA and activate transcription of coo genes. Equilibrium CO binding is cooperative, with a Hill coefficient of n ؍ 1.4, P 50 ؍ 2.
Performance characteristics are described for a kilohertz solid-state laser source for resonance Raman spectroscopy. Narrow line excitation in the 205–230 nm region is provided by quadrupling a titanium: sapphire laser which is pumped by the second harmonic of a Q-switched YLF laser. The combination of tunability, narrow line, high average power, and good stability makes this laser suitable for ultraviolet resonance Raman (UVRR) applications. UVRR spectra of hemoglobin, excited at 229 nm, are as high in quality as those produced by continuous-wave intracavity frequency-doubled Ar+ laser excitation. Raman excitation profiles are reported for aromatic acids in aqueous solution and in hemoglobin.
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