摘要:

Structure-function relationships can provide valuable insight into the function of enzymes. These relationships can be obtained by chemical variation or modification of the original enzyme. Many enzymes contain metal ions which either stabilize the tertiary structure or serve as active sites for the biochemical process catalyzed by the enzyme under consideration. This Comment is devoted to the use of “unnatural” metals in metalloporphyrins that may be regarded as enzyme models.

ISSN:0260-3594    

DOI:10.1080/02603598708072289

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Some of the problems encountered in the determination of the electronic spectra of μ-peroxodicobalt(III) complexes are discussed. After account is taken of the common formation of mixtures of different μ-peroxocomplexes upon oxygenation of Co(II)-ligand solutions, it can be concluded that three classes of spectra exist. Planar single-bridged complexes exhibit a strong (ε ≃ 12,500) π*h→dσ-* peroxide LMCT band at 300–310 nm, with a weak (ε ≃ 600) π*v→dε* band at 425–430 nm. Nonplanar (dihedral angle near 145°) single-bridged complexes exhibit two strong (ε ≃ 6000) π*(02-2) → dσ* bands near 320 and 390 nm. Dibridged μ.-(OH-,02-2) complexes, with a dihedral angle near 60°, exhibit one broad peroxide LMCT band at ≃ 355 nm (ε ≃ 6000). The latter compounds have an additional band near 280 nm which is not due to peroxide. All of the peroxide LMCT spectra are shown to be consistent with a simple model that assumes a sinusoidal dependence of π*(022) energies and σ-overlaps upon the dihedral angle.

ISSN:0260-3594    

DOI:10.1080/02603598708072290

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Expressions for the rate constants for nonadiabatic electron-transfer reactions are presented. These expressions are valid when the electronic coupling between the two redox sites is small and the energy surfaces for the initial and final states are harmonic with identical force constants. High- and low-temperature limiting forms of the rate equations are presented and closed-form expressions which are good approximations to the Franck-Condon sums appearing in these equations are described. Systems in which the electron transfer causes a displacement in one or more vibrational modes are considered. When several vibrational modes are “active,” the higher frequency modes have different effects on the rate constants in the normal and inverted free-energy regions. In the inverted region nuclear tunneling effects are large when hwf> 2kT. Under these conditions the rate has only a weak dependence on temperature and the rate constants can exhibit “quantum beats.” Nuclear tunneling effects are smaller in the normal region: the rate has a stronger dependence on temperature and quantum beats are not observed.

ISSN:0260-3594    

DOI:10.1080/02603598708072291

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0260-3594    

DOI:10.1080/02603598708072288

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor