Power B. Sogo

PHOTO SPIN RESONANCE IN CHLOROPHYLL-CONTAINING PLANT MATERIAL

UCRL37/> UNIVERSITY OF CALIFORNIA TWO-WEEK LOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Division, Ext. 5545 BERKELEY, CALIFORN^

Electron Spin Resonance Spectrum of Dibenzene Chromium Cation

The electron spin paramagnetic resonance of dibenzene chromium cation h a s been observed. I t s c e n t e r is a t a valhe of g = 1.98. I t shows eleven hyperfine components s e p a r a t e d by 3.5 gauss. These a r e i n t e r p r e t e d to b e eleven of the thirteen components expected to r e s u l t f r o m the interaction of the twelve equivalent protons with the unpaired electron.

ENERGY TRANSFER IN ORDERED AND UNORDERED PHOTOCHEMICAL SYSTEMS

BS>A qualitative discussion is presented of the theoretical mental criteria of this phenomenon and, finally, with its possible role in primary quantum conversion in photosynthesis. (W.L.H.)

NMR Study of Acetaldehyde‐Water Mixtures

Acetaldehyde-water mixtures were stadied by highresolution NMR. The acetaldehyde spectrum was observed to consist of quadruplets at delta = -4.3 and 0.7 and doublets at delta = 4.1 and 5.0, The quadruplet at delta = 0.7 and the doublet at delta = 5.0 were assigned to the hydrated form. (C.J.G.)

Nuclear and Electron Paramagnetic Resonance and its Application to Biology

Electron spin resonance and nuclear magnetic resonance both involve the absorption of electromagnetic radiation in the radio-frequency range. They may be considered as extensions of ultraviolet, visible, and infrared spectroscopy. They comprise a unque branch of spectroscopy in that one can vary the absorption energy levels at will, instead of having to use the energy levels nature has given. This advantage arises from the fact that one can vary the strength of the applied magnetic field and thus vary the spacing of the electronic and nuclear magnetic energy levels. No fundamental new truths have been demonstrated in biology by the use of nuclear magnetic resonance. Electron spin resonance measurements are beginning to give information from which one can construct a detailed picture of the nature of some biochemical reactions, such as reactions involving one-electron oxidation-reduction reactions or the so-called free radical reactions. The discovery by electron spin resonance of these free radicals in living material, and their correlation with biological activity, helps confirm what previously was only a hypothesis on certain types of enzymatic reactions. Studies to date employing electron spin resonance or nuclear magnetic resonance are reviewed. (91 references.) (C.H.)

ELECTRON-SPIN-RESONANCE STUDIES ON PHOTO-SYNTHETIC MATERIALS

A number of organisms have been examined for their ability to produce electron-spin-resonance signals at low temperatures in response to illumination. The efficiency of the response is of the order of not less than 5%, and the wavelength for maximum response is generally slightly on the longer side of the wavelength of maximum absorption, with a minimum appearing at the wavelength of maximum absorption.

Energy Conversion in Photosynthetic Processes

The concepts of solid-state photophysics are applied to biological materials, especially particulate matter derived from green plants. Photoinduced electron-spin resonance signals have been observed in isolated chloroplasts and other green plant materials; their growth time is not affected by reducing the temperature to -140 C. The luminescence of these materials has also been investigated under a variety of conditions. The results of these studies have been shown to be consistent with a mechanism involving the recombination of electrons and holes trapped in a quasi-crystalline lattice. Some details of such a mechanism have been proposed that suggest the mode of entry of the light energy into the photosynthetic pathway.

The Free Radical from Perinaphthene

The electron spin resonance spectrum of the perinaphthene free radical is reported and a discussion of electron spin density in this radical is given.