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方法：应用ＴｒｉｔｏｎＸ１００和正丁醇分别提取了大肠癌组织粗提抗原和大肠癌细胞株ＨＲＴ－１８的ＣＢＥ（正丁醇提取物），二者均有抗原活性。抗原经抗大肠癌单抗Ｈｂ３－亲和层析进一步纯化，获得纯大肠癌相关抗原ＣＡ－Ｈｂ３。结果：经鉴定，ＣＡ－Ｈｂ３为糖蛋白，其抗原活性与糖链有关。其分子量随变性程度而异，变性完全（１００℃巯基乙醇作用５ｍｉｎ）时为５０ｋＤ，而变性不完全（１００℃３ｍｉｎ）约２７ｋＤ，故推测该抗原是由两个亚基（约２７ｋＤ）组成的同源二聚体。结论：在ＳＤＳ－ＰＡＧＥ鉴定蛋白质分子量时，使用不同变性时间处理样品可研究其亚基组成
METHODS: Triton X100 and n-butanol were used to extract crude extracts of colorectal cancer tissue and CBE (n-butanol extract) of colorectal cancer cell line HRT-18, respectively. Both of them had antigenic activity. The antigen was further purified by anti-colorectal cancer monoclonal antibody Hb3-affinity chromatography to obtain pure colorectal cancer-associated antigen CA-Hb3. Results: After identification, CA-Hb3 is a glycoprotein and its antigenic activity is related to the sugar chain. The molecular weight varies with the degree of denaturation. It is 50 kD when the denaturation is complete (100 mins of mercaptoethanol for 5 min), and the denaturation is incomplete (100 min for 3 min) is about 27 kD, so it is presumed that the antigen is composed of two subunits (about 27 kD). Homodimer. Conclusion: When SDS-PAGE is used to identify the molecular weight of a protein, the subunit composition can be studied by treating the sample with different denaturation times.