The protein constituents of egg white.

  • Thomas Burr Osborne
Date:
[1900]
Catalogue details

Licence: In copyright

Credit: The protein constituents of egg white. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    12/28 page 360
    Ovalbumin is the chief constituent of egg. white, 50 p. c of its proteids having been obtained in this investigation in the form of perfectly crystallized preparations of this substance, while a large proportion of the remaining proteid matter also consisted of this albumin. Heat coagulum of ovalbumin. Solutions in pure water, containing 2.5 p. c. of pure ovalbumin, become turbid at 6o°, and at 64° yield a flocculent coagulum. When 10 p. c. of sodium chloride is added to these solutions the temperature of coagulation becomes higher, turbidity devel- oping at 69°, and flocks at 700.* When its solution is evaporated to dryness below 50°, and the ovalbumin redissolved in water or in brine, a small amount of substance coagulating at the lower temperature appears to be formed. Thus, sodium chloride solutions containing 2.5 p. c. of B.i, B.2, or C.i, before these substances had been separated by evaporation at 50°, remained absolutely clear until heated to 68° or 69°, while similar solutions, made by dissolving the dried substance, became turbid at 590 and yielded flocks in small quantity at 63°. Preparations of ovalbumin obtained by evaporating their solutions in pure water to dryness below 50°, do not completely redissolve when treated with water. Solutions of some preparations thus made, become very rapidly turbid when filtered, and gradually deposit a not incon- siderable quantity of insoluble matter. The amount of insolu- ble matter in all of our preparations was so small, that we have been unable to learn its nature, but in one case we obtained 0.72 grams from 15 grams of a preparation containing a larger proportion than any we had seen before. This insoluble sub- stance, which contained 15.65 p. c. N, and 1.8 p. c. S, was prob- ably a mechanical coagulum, as it tended to separate at points of contact between the surface of the albumin solution and the vessel containing it. Sodium chloride added to the solution in sufficient quantity diminishes the amount, or prevents its forma- tion. See Plopkins, Jour, of Physiology, 25, 324. It has been stated by Idammarsten that with a constant amount * Stilrke (Pfliiger’s Archiv 12, 18) notes this effect of sodium chloride on the coagulation of the albumin.
    digitised image 1
    digitised image 2
    digitised image 3