protein

(pro’te-in) (Gr. πρῶτος first]. Any one of a group of nitrogenized, non-crystallizable com- unds, similar to each other, widely distributed in the animal and vegetable kingdoms, and forming the characteristic constituents of the ti ues and fluids of the animal body. They are e entially combinations of a-amino acids and _ their derivatives. They are formed by plants, the animal organism recciving them in food, a imilating and metamorphosing them. They all contain carbon, hydrogen, nitrogen, oxygen, and sulphur. Proteins are coagulable by heat and minerfl acids, and are insoluble in ether and alcohol: their solutions are levorotatory. The following cla ification has been recommended: 1. Simple proteins, or protein substances that yield only a-amino acids or their derivatives on hydrolysis. They are albumins, globulins, glutelins, alcohol-soluble proteins, albuminoids, histons, and protamins. 2. Conjugated proteins, or those that contain the protein molecule united to some other molecule or molecules otherwise than as a salt. They are nucleoproteins, glycoproteins, phosphoproteins, nucleo-albumins, hemoglobins, _lecithoproteins. 3. Derived proteins, or derivatives of the protein molecule formed by hydrolytic changes. They are proteans, meta proteins, coagulated proteins, proteoses, peptones, and peptids. The most important members of this group are albumin, casein, legumin, fibrin, vegetable fibrin, myosin, syntonin, gluten. alcohol-soluble p.,_ giliadin. _ bacterial p., a protein formed by the action of bacteria upon ti ue; a toxalbumin. bacterial cellular p., a protein that forms part of the substance of a bacterium. Bence-Jones Pp. See Bence-Jones' albumose, under albumose. coagulated p., a protein coagulated by boiling or by chemic agents. compound p., a protein which on hydrolysis yields a simple protein and a non-protein matter. conjugated p. See under protein. defensive p., any protein formed within the body and serving as a protection against disease; any alexin, phylaxin, or sozin. derived p. under protein. floating P., a protein which does not constitute part of the ti ues, but simply circulates in the body and is then excreted. immune proteins formed by the combination of albumizous matters of the body with the enzymes of pathogenic bacteria. insoluble p., a substance left behind after the other proteins have been extracted from a cell. protective p. Same as defensive p. pyocyanic p., a substance prepared by treating the Bacillus pyocyaneus with pota a: used in suppuration. serum p., any protein found in the serum of the blood. simple p. See under