Abstract
During the course of an investigation of the chemistry of beef pancreas, two protein materials were prepared. The experiments described in the following paper 1 indicate that one of these (P-1) has unusual growth-promoting properties as tested with white rats.
Preparation. Frozen beef pancreas was finely minced and treated for 24 hr with acid 90% 3A alcohol (30 gallons of alcohol and 1 liter of concentrated hydrochloric acid for each 100 1b of pancreas). The insoluble residue was centrifuged off and thoroughly washed with 70% 3A alcohol (28 gallons of alcohol for the residue from 100 1b of glands). After separation with the centrifuge, the air-dried insoluble material was treated continuously with warm acetone and the treatment continued until nearly all of the lipid had been removed. Acetone was removed by air-drying or by the use of the vacuum by air-drying or by the use of the vacuum oven. P-1a and P-1b were prepared from 2 separate lots of this acetone-treated material by successive passages through a meat grinder and a sieve (20 mesh). P-1c was passed through the meat grinder, but was not sieved. P-1d was finely powdered in a hammer mill.
The alcoholic centrigugate and filtrate mentioned above were combined and adjusted to pH 8 with ammonium hydroxide. The insoluble material that separated was removed by filtration, throughly treated with hot acetone, and air-dried. This material was designated P-2. It contained some P-1 material that was not removed when the alcoholic mixture was centrifuged.
Analysis. Analytical figures for the various preparations are given in Table I. Tyrosine and tryptophane analyses were carried out by the method of Lugg, 2 without the use of stannite. Phosphorus was determined by the method of Benedict and Theis, 3 or by the method of Fiske and Subbarow.
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