| 摘要 |
Disclosed are in vitro active cell growth factors that stimulate deoxyribonucleic acid synthesis in the cells, are polypeptide in chemical structure, having a molecular weight range of from 4,000 to 6,000 and an isoelectric range of from pH 4.3 to 5.3, are inert to about 72% aqueous ethanol containing by volume about 0.047% of concentrated hydrochloric acid, soluble in and precipitated from such acid aqueous ethanol solution by admixing in it 3.5 times its volume of a mixture of five parts of acetone with three parts of ethanol, and are soluble in about twice their weight of 20% formic acid.
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