No abstract
1. An investigation of the physicochemical properties of myosin has been carried out. Prepared under standard conditions, the ratio of flow-birefringence to protein concentration is uniform. The effect of electrolytes, pH, and urea on the flow-birefringence and viscosity (relative and anomalous) of myosin has been examined. 2. Decrease or abolition of flow-birefringence does not necessarily imply far reaching denaturation, since such effects can be reversed by a variety of means. 3. When a myosin solution is treated with adenosinetriphosphate, its flow-birefringence is decreased (average 48 per cent), its anomalous viscosity is retained, and its relative viscosity is decreased (average 14 per cent). The full effect of adenosinetriphosphate is obtained at 0.004 M; a molarity very much less than that of other substances which decrease the flow-birefringence of myosin. 4. The changes in the physicochemical properties of myosin brought about by adenosinetriphosphate are spontaneously reversible, and are connected with the enzymatic action of the protein as adenosinetriphosphatase. 5. Effects similar to those of adenosinetriphosphate on the physicochemical properties of purified myosin have been obtained so far only with inosinetriphosphate. 6. Inorganic phosphate is split off by myosin from inosinetriphosphate as well as from adenosinetriphosphate. Inorganic triphosphate is split by 1 to 2 per cent solution of three times precipitated myosin. 7. Adenosinediphosphate and inorganic triphosphate act as competitive inhibitors with adenosinetriphosphate, blocking the fall of flow-birefringence. 8. The implications of the results, and the conception of active enzymic groups attached to proteins participating in cell structure, whether contractile or non-contractile, are discussed in relation to present views on muscle physiology and other biological problems.
In the foregoing paper a description has been given of apparatus whereby the flow-birefringence and the relative viscosity of a protein solution may be measured and its anomalous viscosity assessed, careful distinction being made between effects due to the bulk phase and those due to the surface film at the air-water interface. We have now to turn to the more specific detailed results of the investigation of a number of proteins. 1 Beha~iour o/ProteinsTobacco Mosaic Disease Virus Nudeoprotein.--This plant virus protein, 2 (for full descriptions of which see Bawden, 1939;Bernal and Fankuchen, 1941) has already been subjected to measurements of viscosity and birefringence, in the work of Robinson (1939). The specimen used by us gave the flow-birefringenee curves seen in Fig. 1; allowing for differences in conditions (in our experiments 1.5 cm. column as against 21 cm.; 0.5 per cent as against 0.02 per cent concentration of virus; shear rate 13.1 as against 18.8; Robinson's rumple was more flow-birefringent than ours. In the viscosimeter it was interesting to find that under both low level (film) and flood level (bulk) conditions, the virus gives a strongly anomalous type of flow, see Figs. 2 and 3.) This probably means that the virus aggregates retain their anisometric shape when they enter into the formation of the surface film.The only difference is that the viscosity curve of 0.025 per cent virus for the bulk descends to its orientation plateau by about 20 R.p.,x. while that for the film does not do so until a speed of between 70 and 80 g.P.~, is attained. Orientation within the film must therefore be a good deal more difficult than oriental
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