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1. Details of an improved method for starch-gel electrophoresis of water-soluble muscle proteins are given. 2. Methods are described for detecting enzyme activities on the starch gel after electrophoresis, by using pieces of filter paper. 3. Compositions of incubation mixtures suitable for detecting any of the enzymes of glycolysis, and certain other enzymes, are given. 4. A comparison of the various enzymes in extracts of several muscles from one rabbit was made; most differences are quantitative only. 5. A detailed comparison of the mobilities of various enzymes in extracts of muscles from a wide variety of species was made. Each species was found to have a characteristic pattern of proteins on the starch gel, and the mobilities of individual enzymes varied considerably. 6. Potential uses and extensions of the methods are discussed.

FDP aldolase has been purified and crystallized from the muscle of codfish. The specific activity of the codfish enzyme was found to be two-thirds that of rabbit muscle aldolase. Other catalytic properties, the molecular weight, and the carboxyl-terminal structure were similar to those of rabbit muscle aldolase. A tryptic peptide containing the Schiff base-forming lysine (1) has been isolated and its primary structure determined as: Ala-Leu-Ser-Asp-His-His-Val-Tyr-Leu-Gln-Gly-Thr-Leu-Leu-βGlys-Pro-Asn-Met-Val-Thr-Ala-Gly-His-Ser-CMCys-Ser-His-Lys. Extensive homology observed in this region of the aldolase molecules isolated from biologically divergent sources indicates the importance of this structure for catalysis of the aldolase reaction.

A sequence of 107 amino acids has been determined in the single chain of the major parvalbumin (pI 4.36) from hake ( Merluccius merluccius ) muscle as a result of studies on peptides obtained after tryptic, chymotryptic, peptic and cyanogen bromide cleavages of the protein.

1. 1. Differences in muscle proteins of the species and subspecies of the genus Xiphophorous are discernable by means of paper electrophoresis. 2. 2. The lower limit of differentiation was found at the subspecies level, as the microevolutionary divergences of isolated populations of the species maculatus could not be detected with this method. 3. 3. The electrophoretic data parallel the independently established taxonomic division of the genus Xiphophorus into three species groups. Thus, there are two extreme pattern groupings and one intermediate for both species groups and muscle proteins.

VERTEBRATE neurohypophysial hormones have a common structural pattern characterized by a chain of nine amino-acid residues with a disulphide bridge connecting the amino-acids in positions 1 and 6. There are usually two hormones in each species, the active principles rarely varying from one species to another within a given class. Thus oxytocin and arginine vasopressin have been chemically identified in five species of mammals belonging to the orders Primates, Artiodactyla, Perissodactyla and Cetacea. Isotocin (Ser4-Ile8-oxytocin) and vasotocin (Arg8-oxytocin) have up to now been isolated from six species of bony fish belonging to the families Gadidae, Scombridae and Cyprinidae. The structural variations which occur between one vertebrate class and another are confined to one or two amino-acid substitutions in positions 3, 4 or 8 (for a review of this subject see ref. 1).