Melvin Calvin

The absorption spectra of suspensions of living micro-organisms☆

A new method is described for obtaining sharp absorption spectra from suspensions of micro-organisms. The principle of this technique is this technique is to measure the total asorbance of the suspensions by attaching opalescent plates to cuvettes for both solvent and suspension. It must be emphasized that this technique does not involve any treatment of the suspension or any change of the optical system of the spectrophotometer for measurement. We can obtain a clear absorption spectrum of living micro-organisms with the commonly-used spectrophotometer just by attaching opalescent plates to the cuvettes. The applications to the other translucent materials such as suspensions of blood and crystals and a piece of leaf or petal have been shown.

The Path of Carbon in Photosynthesis. XXI. The Cyclic Regenerationof Carbon Dioxide Acceptor

IJCEL-2369 Unclassified Chemistry D i s t r i b u t i o n UNIVERSITY O CALIFORML4 F Radiation Laboratory Contract No. M-7405- eng THE P T O CARBON I N PHdGSYNTHESIS .BI. A H F T E CYCLIC REGENERATION O CARBON DIOXIDE ACCEPTOR H F J. A , Bassham, &Ae A. Benson, Lorel D. K r ~ r ~ Anne Z. Harris, A. T. Wilson and M. Calvin October, 1953 Berkeley, California

Bonding in Copper(II) Chelates: Solvent Effects in Their Visible Absorption Spectra

UNIVERSITY OF CALIFORNIA BONDING IN COPPER SOLVENT CHELATES: VISIBLE EFFECTS IN THEIR ABSORPTION SPECTRA 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. Diuision. Ext. 5545

The Chemistry of 1,2-Dithiolane (Trimethylene Disulfide) As aModel for the Primary Quantum Conversion Act in Photosynthesis

Some chemical and photochemical observations of 1,2-dithiolane and its derivatives are reported with particular reference to the possible mode of function of the naturally occurring system, 6-thioctic acid. Experimental evidence is presented to demonstrate that the strain energy in this 5-membered ring is not less than 6.5 Kcals and probably larger. Reagents which both oxidize and reduce this ring are described together with the conditions required for its reformation from the corresponding dithiol. Evidence is adduced to indicate that the primary product of photolysis of this ring in acetic media is very likely a thiol and sulfenic acid or derivative thereof.

ELECTROCHEMISTRY OF EXCITED MOLECULES: PHOTO‐ELECTROCHEMICAL REACTIONS OF CHLOROPHYLLS*

Abstract— Semiconductors with a sufficiently large energy gap, in contact with an electrolyte, can be used as electrodes for the study of electrochemical reactions of excited molecules. The behavior of excited chlorophyll molecules at single crystal ZnO‐electrodes has been investigated. These molecules inject electrons from excited levels into the conduction band of the electrode, thus giving rise to an anodic photocurrent. The influence of various agents on this electron transfer has been studied. In the presence of suitable electron donors (e.g., hydroquinone, phenylhydrazine) in the electrolyte chlorophyll molecules, absorbing quanta, mediate the pumping of electrons from levels of the reducing agents into the conduction band of the semiconductor‐electron acceptor. The electron capture by the semiconductor electrode is irreversible, when an adequate electrochemical gradient is provided in the electrode surface. Some properties of excited chlorophyll at semiconductor electrodes (unidirectional electron transfer, highly efficient charge separation, chlorophyll as electron pump and able to convert electronic excitation into electric energy) show similarity to the behavior of chlorophyll in photosynthetic reaction centers.

Hydrocarbons of Biological Origin from a One-Billion-Year-Old Sediment

The isoprenoid hydrocarbons, phytane (C20H42) and pristane (C19H40), are present in the oil seeping from the Precambrian Nonesuch formation at the White Pine Mine, Michigan. Gas-liquid chromatography and mass spectrometry provide the isolation and identification procedures.

The organic geochemistry of ancient sediments—Part II†☆

Oils and shales from 3 million to 2.7 billion years old analyzed for hydrocarbon content, using gas chromatography and mass spectrometry

Plant crops as a source of fuel and hydrocarbon-like materials.

Chemical analyses have been made of a number of plant species in order to assess their suitability as renewable sources of hydrocarbon-like photosynthetic products. Yields of rubber and wax, glycerides, isoprenoids, and other terpenoids were estimated. Individual sterols were identified in latex from some species.

PHOTOSYNTHESIS AS A RESOURCE FOR ENERGY AND MATERIALS

Abstract— Photosynthesis, both natural and as a model process, is examined as a possible annually renewable resource for both material and energy. The conversion of carbohydrate from cane, beets and other sources through fermentation alcohol to hydrocarbon may again become economic in the light of improved fermentation technology. It may also be possible to produce material by direct fermentation of relatively labile carbohydrates in seaweed. Even the direct photosynthetic production of hydrocarbon from known sources (Hevea, etc.), or newly bred ones, seems possible in view of the large number of species and the new techniques of plant cell cloning which have already been successful on sugar cane.

Photovoltaic effect and photoconductivity in laminated organic systems

As a result of a wide variety of studies on photosynthesis in living plants and plant fragments, together with the development of photosensitive, photovoltaic junctions in inorganic crystals and the discovery and exploration of semiconduction in organic molecular substances, a suggestion has been made that the primary quantum conversion process in photosynthetic tissues involves the creation and separation of charge to opposite sides of an asymmetrically-constructed lamina, followed by the trapping of both the electrons and the holes which then lead to their respective chemical processes, namely reduction of carbon dioxide and oxidation of the water to oxygen. This has led us to study model systems as semiconductors with a view to creating an organic photovoltaic junction.