UV resonance Raman spectra reveal a structural basis for diminished proton and CO2 binding to alpha,alpha-cross-linked hemoglobin.

UV resonance Raman difference spectra between ligated and deoxyhemoglobin contain tryptophan and tyrosine signals which arise from quaternary H-bonds in the T state, which are broken in the R state. These H-bonds are unaffected by bis(3,5-dibromosalicyl) fumarate cross-linking at the Lys alpha 99 residues, which prevents dissociation of Hb tetramers to dimers. However, when the pH is lowered from 9.

Structural changes in cytochrome c upon hydrogen-deuterium exchange.

The resonance Raman spectra of yeast ferri- and ferro-iso-1-cytochrome c dissolved in H2O and D2O are reported. Hydrogen exchange in the protein leads to distinct spectral changes of heme vibrational bands, particularly in the region between 670 and 710 cm-1 and at approximately 443 and approximately 450 cm-1. The latter two bands, which have previously been assigned to porphyrin modes including bending vibrations of the propionate side chains [Hildebrandt, P.

Unusual heme structure in cytochrome aa3 from Sulfolobus acidocaldarius: a resonance Raman investigation.

Well-resolved Soret-excited resonance Raman spectra have been obtained in the heme marker band region (1440-1700 cm-1) for the fully oxidized and fully reduced forms of the terminal oxidase aa3 from Sulfolobus acidocaldarius. The results demonstrate that in both heme groups the structural properties depart from those of other aa3 oxidases. In the fully oxidized form, the formyl stretching vibration of heme a is observed at 1656 cm-1, approximately 7 cm-1 higher in frequency than found for beef heart cytochrome c oxidase.

Comparative resonance Raman study of cytochrome c oxidase from beef heart and Paracoccus denitrificans.

Well-resolved, Soret band excited resonance Raman spectra were measured from the fully oxidized and fully reduced cytochrome c oxidase from beef heart and Paracoccus denitrificans. The vibrational patterns in the marker band region (1450-1700 cm-1) were analyzed, and a complete assignment of heme a and heme a3 vibrational modes is presented, permitting a detailed structural comparison of the mammalian and bacterial enzymes. Similar frequencies of the porphyrin modes for the reduced heme a and the reduced and oxidized heme a3 are found, indicating a close relationship of the ground-state conformations in all oxidase species studied.

Fourier transform resonance Raman spectroscopy of phytochrome.

The Pr and Pfr forms of phytochrome in H2O and D2O have been studied by Fourier transform resonance Raman spectroscopy with near-infrared excitation (1064 nm). It is demonstrated that this technique is a powerful method for analyzing the chromophore structures of photosensitive pigments. The high spectral quality allows discussion of vibrational assignments based on an empirical approach using previously published data obtained from model compounds.

Resonance Raman study of cytochrome aa3 from Sulfolobus acidocaldarius.

The single subunit terminal oxidase of Sulfolobus acidocaldarius, cytochrome aa3, was studied by resonance Raman spectroscopy. Results on the fully oxidized, the fully reduced, and the reduced carbon monoxide complex are reported and compared with those of eucaryotic cytochrome oxidase. It is shown that in both redox states the hemes a and a3 are in the six-coordinated low-spin and six-coordinated high-spin configuration, respectively.

Nanosecond kinetic absorption and calorimetric studies of cyclopentenone: the triplet, self-quenching, and the predimerization biradicals.

The photolysis of 2-cyclopentenone has been studied by a combination of kinetic absorption spectrophotometry and time-resolved photoacoustic calorimetry. The lifetime of the cyclopentenone triplet is strongly concentration dependent and corresponds to a value of 380 +/- 75 ns at infinite dilution in acetonitrile. The biradical intermediate (or pair of isomeric biradicals) immediately preceding formation of photodimer forms with very high efficiency upon quenching of triplet cyclopentenone by a second ground state cyclopentenone molecule and has an energy of 47 kcal/mol relative to two molecules of reactant.

Determination of triplet excitation energies of cyclic enones by time-resolved photoacoustic calorimetry.

Energies and lifetimes of triplet states of a series of 2-cyclohexenones have been measured in solution under ambient conditions by time-resolved photoacoustic calorimetry (PAC). The PAC triplet lifetimes are in excellent agreement with lifetimes measured by kinetic absorption spectrophotometry (KAS) using nanosecond flash techniques, indicating that the present data indeed pertain to the enone triplets previously studied using KAS. The data demonstrate that, as previously proposed, the pi pi triplet energies in these systems are indeed correlated with triplet lifetimes, and vary sensibly with the anticipated extent of conformational flexibility of the C = C bond.