194 



RADIATION BIOLOGY 



mt)\ I's (1k' position of (lie loiif^cr wjivc hand lo '.V2{)() A, without affect ing 

 the '2')()() A hand. Addition of a .S-liy(h<)xy f2;rouj) to flax'onc, as in llu; 

 flavonols causes thi- appcai'ance of an additional hand at XioO 3400 A 

 (Fig. 5-29). Hydroxy or mothoxy side groups in various positions may 



6000 5500 5000 4500 4000 3500 3000 2500 2000 



WAVE LENGTH, A 



Fig. 5-28. Absorption spectra of I, pclargonidin ; II, cyanidin; and III, delphinidin. 

 {Schou, 1927.) 



2.6 



2300 2500 2700 2900 3100 3300 3500 3700 3900 

 WAVE LENGTH. A 



Fig. 5-29. Absorption spectra of I, flavone; II, 3-oxy-flavone (fiavonol); and III, 

 flavonone. (Skarzynski, 1939.) 



shift these maxima by as much as 100-200 A (AronofT, 1940; Skarzynski, 

 1939). 



The catechins, which occur widely in woods and leaves, may be 

 regarded as partially reduced anthocyanidins. The reduction has 

 destroyed the extensive conjugation, and the absorption of catechins may 



