Respitory proteids : researches in biological chemistry / A.B. Griffiths.

  • Arthur Bower Griffiths
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: Respitory proteids : researches in biological chemistry / A.B. Griffiths. Source: Wellcome Collection.

    90/158 (page 78)
    introduction of chromophores (containing iron) into albuminoid molecules. Witt maintains that the coloration of carbon compounds is due to the presence of a heterogeneous ring in the molecule, though it must be admitted that the existence of such a ring in many coloured organic bodies cannot at present be understood. It, may be mentioned that the “ quinonoid ” hypothesis of Dr. Armstrong* is, so far, the only satisfactory attempt to formu- late a theory of chromogenesis. In fact, among complex carbon compounds colour is conditioned by a quinonoid structure. “A quinonoid com- pound may be defined as a hexapliene—i.e., an unsaturated cycloid composed of six ‘elements,’ two ‘ elements ’ of which are groups in either para- or ortho-positions. Coloured sub- stances generally appear to fall within this ■definition,” and a change of colour is indicative of a change of structure. From what has already been said it may be gathered that in order to arrive at the consti- tutional formulae of such complex molecules plants) is a derivative of indol, the pyrrol of the aromatic or benzene series ; and that indol (CBH4 [CH]2 NH) may be obtained by the pancreatic decomposition of albuminoids, and by the fusion of the latter with potassium hydroxide. * Armstrong, Proc. Chem. &'oc., 18S8, p. 27 ; 1S92, p. 101, p. 1S9; 1893, p. 52, p. 206.