Biophysical Journal 24: 335-345 (1978)
© 1978 the Biophysical Society

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Related articles in Biophys. J. Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ballard, S G Articles by Mauzerall, D Search for Related Content PubMed PubMed Citation Articles by Ballard, S G Articles by Mauzerall, D

Photo-initiated ion formation from octaethyl-porphyrin and its zinc chelate as a model for electron transfer in reaction centers.

ABSTRACT

Ion formation from the reaction of triplet (T) and ground state (P) octaethyl-porphyrin (OEP) and zinc octaethyl porphyrin (ZnOEP) and the corresponding cross-reactions have been measured in dry acetonitrile. A uniquely sensitive and fast conductance apparatus and a pulsed dye laser allowed the measurements to be made at the necessarily very low concentrations of T. The hemogeneous reaction of T (ZnOEP) and P (ZnOEP) occurs with rat constant k(1) = 2.0 x 10(8) M(-1)s(-1) and an ion yield of 67%. The similar homogeneous reaction of OEP has k(2) = 1.3 x 10(8)M(-1)s(-1) but an ion yield of only 3%. The cross-reaction of T (OEP) with P (ZnOEP) has k(3) = 1.5 x 10(8) M(-1)s(-1) and an ion yield of 27%, while the inverse cross-reaction of T (ZnOEP) with P (OEP) has k(4) = 3 x 10(8) M(-1)s(-1) and an ion yield of 20%. Thus, the rate constants are only slightly affected but the yields are sensitive to the porphyrin. The possible formation of the heterogeneous ions ZnOEP+ + OEP-, thermodynamically favored by 0.3 V over the homogeneous ions, has little influence on the observed yields. The data are explained by electron transfer and Coulomb field-electon spin-controlled escape of the initial ion-pair.

Related articles in Biophys. J.:

DISCUSSION

Biophys. J. 1978 24: 342-345. [PDF]