Both the determination and the identification of the naturally occurring coproporphyrin isomers I and III depend upon the exactness of the data relating to their physical properties and to those of their methyl esters. Quantitative estimation of these isomers involves spectrophotometric or fluorimetric comparisons with standard solutions usually prepared from the crystalline tetramethyl ester of isomer I. The accuracy of such determinations depends upon the purity of this ester and also upon the knowledge of the spectral absorption of the isomers or of the relative fluorescence efficiencies of the two molecules. Differential identification of the coproporphyrin isomers is achieved through differences in the properties of their tetramethyl esters, particularly their solubility in organic solvents and their melting-points. A clean-cut separation of the esters is not easily effected. This difficulty must be borne in mind in considering the melting-points of the methyl esters isolated from natural sources, unless careful recrystallizations have been done. In studies of porphyrin metabolism, an obvious essential is the definition of those properties which form the basis of quantitative methods of estimation and of identification. This paper presents data obtained in an attempt to correlate the spectral absorption and fluorescence of the isomers and the m.p.'s of their esters, so that their additive and constitutive properties may be more closely defined.The necessity for such data became apparent when we found that solutions prepared from synthetic coproporphyrin I tetramethyl ester (as received from Prof. H. Fischer) gave extinction coefficients, E1 J(wlv), as much as 12 % lower than those made up from the same specimen after recrystallization. Recrystallization, however, caused no appreciable change in m.p.'s, which were throughout within the generally accepted range of good values for this substance (Table 1 and Fig. 4). Similar observations were made on synthetic coproporphyrin III tetramethyl ester and on several natural specimens. This experience led us to investigate the criteria for the purity of the tetramethyl esters of coproporphyrins I and III, and to attempt to define more closely the additive properties of standard solutions of coproporphyrins I and III. EXPERIMENTALMaterial8 Sources. The synthetic tetramethyl esters of coproporphyrins I and III were those of Prof. Fischer (Munich):for the latter sample we are indebted to Dr C. Rimington, as also for two specimens of the tetramethyl ester of coproporphyrin I isolated by him, and for several specimens of the corresponding coproporphyrin III ester obtained by decarboxylation of uroporphyrin III made from its copper complex, turacin (Rimington, 1939). Another specimen of coproporphyrin I tetramethyl ester was isolated by us from faeces of a patient with haemolytic anaemia.Purification. Coproporphyrin I tetramethyl ester was recrystallized from chloroform-anhydrous methanol mixtures, the crystals being removed while the volume of mother liquor was still fai...

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Preliminary studies of the rates of disappearanc of Methemoglobin (MHb) and Sulphemoglobi (SHb) from human blood in vivo after cessatio of contact with the agents, such as sulphonamide: acetanilide or TNT, causing these abnormal piE ments : Jope, O'Brie and Watson (1942)), revealed a striking contra: between MHb and SHb in this respect. MHb wa found to disappear rapidly from the circulatin blood and was undetectable after 2 to 5 days fror removal of the causative agent (cf. also Cox an Wendel (1942)), whereas SHb was found to persi and was still detectable after many weeks. Meth4 moglobin also disappeared rapidly from draw blood, being usually no longer detectable after aboi 24 hours at room temperature (Jope and O'Brie (1942) (1930, 1931Wendel (1933): Cox and Wendel (1942): and Dral kin (1945 ). SHb, on the other hand, may be kel unchanged in drawn blood even longer than the re cells can be kept intact, and remains for sever, weeks after hemolysis as a constant fraction of ti total pigment present, so long in fact as the bloc can be kept sterile. It appears, therefore, that ti red cell has no mechanism within it for the tran formation of SHb. If this is so, the body can ha) no means of removing SHb other than by destru tion of the red cells that contain it.The disappearance of sulphemoglobin in vil was therefore studied in some detail, both in ord4 to gain a more precise knowledge of the conditioi necessary for recovery from SHb cyanoses, and as possible means of studying the dynamics of red cc destruction.

Maize grains from an archaeological site in N.E. Arizona have been examined by light microscopy and electron microscopy. Their endosperm tissue was intact and was similar to that of modern maize although some of the features seen in other non-viable seeds were present; the embryos, however, were discoloured and damaged. Protein has been extracted from both endosperm and embryos although only a small quantity was extracted from the latter. The protein sub-unit profiles of these extracts and of storage protein fractions prepared by serial extraction of endosperm meal in salt, alcohol and sodium dodecyl sulphate (SDS) solutions have been determined after electrophoresis in SDS-acrylamide gels. The data obtained indicate that zein and glutelins similar to modern maize proteins were the major storage proteins but that their proportions differed to those in modern maizes; these conclusions are supported by the amino acid composition of the wholse seed meal. It is suggested that these procedures may be applicable to other archaeological samples of seeds including those of other species and that the data so obtained may be of use in cultural studies and in botanical studies of crop plant origins and evolution.

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