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THE EFFECT OF BETA RADIATION ON PORPHYRIN 

 COMPOUNDS IN AQUEOUS SOLUTIONS 



R. TiRRELL 



School of Biological Sciences, University of New South Wales 



INTRODUCTION 



During the past few years there has been a marked interest in porphyrins 

 as biological and chemical compounds. This is reflected in the large number 

 of investigations carried out on the biosynthesis of porphyrins''"^' '^' ^' ^. 



Irradiation of porphyrin compounds has also received increased attention. 

 It is generally agreed that the product of irradiation of a porphyrin or haem 

 is an intact cyclical tetrapyrrole^. However, a precise knowledge of the 

 change occurring in porphyrin compounds on irradiation is lacking, and the 

 work herein deals with two aspects of this. 



The investigations are part of a programme concerned with the effects 

 of radiation on the synthesis of porphyrins by the erythrocytes of the domestic 

 fowl. Thus the first section describes the effect of ^ radiation on proto- 

 porphyrin when it is dissolved in plasma from fowl's blood; the effect of dose 

 rate, as well as the general effect of the radiation on the protoporphyrin, is 

 considered. The second section deals with changes in the molecular structure 

 of protoporphyrin and ferriprotoporphyrin when these are irradiated in 

 alkaline solution. 



EXPERIMENTAL 



Materials 

 Plasma 



The plasma was from blood collected during routine commercial killing 

 of adult fowls [Callus domesticus) . Age, sex and strain were neglected. 



The blood contained 15 mg penicillin G, 15 mg streptomycin and 20 mg 

 heparin (dissolved in 5 ml. 0-9 per cent NaCl) per 500 ml. blood. 



Radiation 



The ^°Sr-^^Y/S radiation (500 millicurie) source at the Radiochemistry 

 Laboratory, University of N.S.W., was used throughout. 



Details of procedure, dosimetry, etc., have been given previously*. 



All radiation doses given are stated in rads, and each is an 'average' dose 

 [i.e., energy absorption/ml. solution). This also applies to the dose rates 

 which are given, {i.e., rad ml.""' min~'). 



Methods 

 Protoporphyrin in plasma 

 (a) General effect 



Preparation of solution — 3-6 mg protoporphyrin were dissolved in 10 ml. 

 N NaHCOg and volume made up to 100 ml. with plasma. 



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