The Role of Specific Amino Acid Residues in The Vibrational Properties of Plastocyanin

Abstract

Resonance Raman spectra for zucchini, cucumber, bean, and lettuce plastocyanins, blue copper proteins involved in plant photosynthetic electron transport, have been measured at wavelengths throughout their intense 600-nm absorption band. A comparison of the resonance Raman spectra of these four plastocyanins, and two others previously quantified, demonstrates that they all exhibit vibrational bands with similar frequencies but significantly different relative intensities. Self-consistent analysis of the absorption band and resulting resonance Raman excitation profiles using a time-dependent wave packet formalism for these four plastocyanins demonstrates that many of the derived molecular parameters are similar to those determined previously for two other species of plastocyanin. However, significant differences are observed in the mode-specific displacements and reorganization energies, although the total reorganization energy is 0.16 ( 0.01 eV for all six plastocyanins. A detailed comparison of the structural and compositional differences among the six plastocyanins, using the previously reported structure of poplar a plastocyanin, suggests that these modespecific differences arise from specific amino acid differences within 10-12 Å of the copper site. These results are interpreted as arising from a through-bond mode-mixing mechanism and a through-space electrostatic mechanism and suggest that the normal modes of the copper site are delocalized into the protein. In addition, lettuce plastocyanin has a significantly greater homogeneous line width, probably as a result of compositional differences adjacent to the copper active site. These results demonstrate that the protein environment is strongly coupled to or mixed in with the copper site vibrational dynamics. Further evidence for the sensitivity of the resonance Raman intensities to particular electron-transfer pathways within the protein is also discussed.

Resonance Raman Spectroscopic and Density Functional Theory Study of Benzoin Diethyl Phosphate

“…The utility of employing Raman spectroscopy to help determine molecular structure is well known, and resonance Raman spectroscopy has been recognized to be a valuable technique to use in obtaining information about the excited state potential surface in the Franck−Condon (FC) region of the ground state. − The intensity distribution of the resonance Raman bands can provide important information regarding the molecular structure and properties of the excited electronic state. ,− , The resonance enhancement pattern can also contain information about the nature of the vibronic interaction between nearby excited states. ,− , To help elucidate the nature of excited states and the possible interaction between them, resonance Raman spectra of ground state BDP have been obtained in resonance with two different electronic statesthe so-called ring ππ* (S 3 ) and carbonyl nπ* (S 1 ) statesusing excitation wavelengths of 252.7 and 354.7 nm, respectively. A simple model and calculation were made to simulate the absorption spectrum and resonance Raman intensities for the 252.7 nm excitation.…”

An analytic approach to electron-molecule potentials using STOs

“…( 1 2) and (1 3) are calculated for the two ground-state target representation of McLean et al [4] and Fraga and Ransil [ 5 ] . Tables I and I1 give the form of the wavefunction data appropriate for substitution into Eqs.…”

“…. @b'*N(Nl ) a ( Nl ) @ y (N ) p ( N ))( 5 ) where the operator P permutes the coordinates of the space-spin orbitals in Eq.…”

Theoretical treatment of hydrogen abstraction by hot tritium atoms

“…As a check on the validity of the calculational method using Cusachs's approximation, a comparison was made of the overlap population for H, as a function of distance computed by the semiempirical technique using a 1s basis STO on each H against the single configuration LCAO-MO-SCF results of Fraga and Ransil using Is, 2s, 2p STO'S (where all 5 were varied independently) [19]. From Table I, it may be seen that the two methods give closely comparable results, especially in the regions near equilibrium where the greatest contribution to the Fraga and Ransil function was due to 1s STO'S on H. (For H, itself there is no maximum of overlap population in the binding region even with the LCAO-MO-SCF calculation.…”