Warren M. Garrison

The radiation chemistry of amino acids, peptides and proteins in relation to the radiation sterilization of high-protein foods

Abstract An important source of information on the question of whether or not toxic or other deleterious substances are formed in the radiation sterilization of foods is the chemical study of reaction products and reaction mechanisms in the radiolysis of individual food components. The present evaluation of the radiation chemistry of amino acids, peptides and proteins outlines the various radiation-induced processes which lead to amino acid degradation and to the synthesis of amino acid derivatives of higher molecular weight. Among the latter are the α,α-diamino dicarboxylic acids which are formed as major products in the radiolysis of peptides both in aqueous solution and in the solid state. The α,α-diamino acids are of particular interest as irradiation products because they represent a class of compounds not normally encountered in plant and animal protein sources. Such compounds have, however, been isolated from certain types of bacteria and bacterial products. All of the available data strongly sug...

Radiation-Chemical Oxidation of Peptides in the Solid State

Gamma-ray irradiation of polypeptides as highly dispersed fluffs under oxygen leads to chemical degradation of the peptide bond with the remarkably high oxygen consumption of about one molecule per 2 ev of absorbed energy. A radical chain mechanism appears to be involved, and there is evidence that excited states of the polypeptide aggregate undergo chemical quenching by molecular oxygen.

Carrier‐Free Radioisotopes from Cyclotron Targets. VI. Preparation and Isolation of Ag105,106,111 from Palladium

Author(s): Haymond, Herman R.; Larson, Kermit H.; Maxwell, Roy D.; Garrison, Warren M.; Hamilton, Joseph G.

RADIOLYTIC CLEAVAGE OF THE PEPTIDE MAIN-CHAIN IN CONCENTRATED AQUEOUS SOLUTION: ENERGY LEVEL OF EXCITED-MOLECULE INTERMEDIATES.

Abstract The γ-radiolysis of oxygen-free solutions of simple peptides such as N-acetylglycine and N-acetylalanine at concentrations above 0.1 M leads to formation of excited species RCONHCHR2∗. Reactions of these excited-molecule intermediates lead to cleavage of the peptide main-chain with formation of amide and fatty acid functions. Through use of a series of aromatic second-solutes as excitation quenchers it is possible to assign the energy level of RCONHCHR2∗ at ∼3.5 eV.

Water Decomposition Yields in the Radiolysis of Aqueous Formic Acid‐Oxygen Solutions by Cyclotron‐Produced Radiations

Water decomposition yields in the radiolysis of aqueous formic acid-- oxygen solutions by cyclotron-produced protons and neutrons are reported. Two primary processes occur, (1) H/sub 2/O = H + OH and (2) H/sub 2/O + 1/2H/sub 2/0/ sub 2/. The absolute yields of reactions 1 and 2 are essentially independent of pH over the corresponding range and, to a first approximation, are related to the yields of observed products by the equations G(l) = G(CO/sub 2/) = -G(0/sub 2/), G(2) = 2G(H/sub 2/), and G(1) + 0.5 G(2) = G(H/sub 2/0/sub 2/). The values G(l) = 2.39 plus or minus 0.05 and G(2) = 1.26 plus or minus 0.18 were obtained for 10Mev protons. The value G(1)/G(2) = 2.73 plus or minus 0.10 was obtained from the neutron data. (L.T.W.)

Radiolysis of liquid N-ethylacetamide

Abstract The γ-radiolysis of liquid N -ethylacetamide leads to formation of acetaldehyde and ethyl amine as major decomposition products. The mechanism of formation of these products is examined through use of added electron and radical scavengers such as RCl, RSH and Fe III. The results are consistent with a reaction scheme in which the radiation-induced steps involve the stoichiometries: A detailed reaction scheme for the intermediate processes is presented.

Comparative free radical chemistry in the radiolytic deamination and dephosphorylation of bio-organic molecules. II: Oxygenated solutions

A wide range of experimental data is evaluated in support of the hypothesis that the reductive deamination of amino acids and peptides by eaq- and the oxidative dephosphorylation of glycol phosphates by OH in oxygen free solution are related in terms of a common elimination reaction involving free-radical intermediates of the same genre, that is, XCH(R)C(OH)R----HX + CH(R)COR where X = NH2, RCONH, and H2PO4 respectively. The proposed reaction model unifies for the first time the basic free-radical chemistry of N-C and PO-C bond cleavage in the radiolysis of peptides and glycol phosphates including proteins and nucleic acids in oxygen-free solution.

Methodology in the radiolysis of biochemical compounds with cyclotron beams at low flux densities.

Abstract A modification of the standard beam-optics of the LBL 88-Inch Cyclotron now makes it practicable to use cyclotron radiations in the detailed study of the effects of linear energy transfer (LET) in the radiation chemistry of organic compounds in the solid state. Dosages and dose-rates are comparable to those employed in conventional γ-ray studies. The modification involves passing the focused beam through a pair of “beam-sweeping” electromagnets so that a circular target area up to 10 cm in diameter can be uniformly irradiated with beams in the nanoamp range. Yield data are given for the radiolysis of the Fricke dosimeter with beams of H+, H+2, Be+4, C+6 and Ne+10 at ∼10 MeV per nucleon. Preliminary data on the effects of LET in the radiolysis of solid glycine are reported.

Role of excited species (RCONHCHR2)∗ in the radiolytic oxidation of the peptide main-chain in aqueous systems☆

Abstract In the γ-radiolysis of oxygen-free solutions of simple peptides at concentrations above ≈ 0·1 mol/l the formation of excited species, RCOue5f8NHue5f8CHR 2 ∗ , leads to dissociation of the peptide main-chain with formation of amide and fatty acid functions ( Advanc. Chem. Ser. 1968, 81 , 384). Reported here is detailed chemical evidence that the species RCOue5f8NHue5f8CHR 2 ∗ reacts quantitatively with oxidizing solutes such as O 2 and Fe III to yield hitherto undetected oxidation products which have the chemical properties of dehydropeptides.

A Centrifugal Pump Target Assembly for the Cyclotron Bombardment of Liquids

Author(s): Garrison, Warren M.; Haymond, Herman R.; Powell, Harry; Corum, Charles; Hamilton, Joseph G.