问题描述：
氨基酸序列分析问题：已知一个七肽的组成为:gly,phe（2）,tyr,met,asp,用胰凝乳蛋白酶水解
已知一个七肽的组成为:gly,phe（2）,tyr,met,asp,用胰凝乳蛋白酶水解后可得一个三肽和一个四肽,三肽组成为phe,tyr,asp.此7肽经CNBR处理后,再经阳离子交换树脂层析并洗脱得到一个组分为arg,phe,gly的三肽.此七肽经胰蛋白酶水解可得phe,用FDNB反应后再水解得DNP-tyr.请写出此肽序列.
更正：七肽的组成为:gly,phe（2），tyr，met，asp，arg
问题解答：
我来补答
（2）是啥意思?
再问： 2个
再答： the answer is : NH2-tyr-phe-asp-met-gly-arg-phe-COOH
再问： 求详细的解析！！！谢谢
再答： First，FDNB is a technique to determine the n-terminus of the peptide, so the N-terminus of this polypeptide is tyr. then, pancreatic protease hydrolyze the polypeptide immediately after the carboxylic group of the acidic residue, that is asp, in this case. Since tyr, phe, and asp are together , the first 3 residues are : NH2-tyr-phe-asp. then, the pancreatic tripsin cuts the polypeptide after the carboxylic group of arg, so, the last two residues are -arg-phe-COOH. then, we are left with met and gly. Since arg, phe, gly are together,we now can be sure that the fourth one is met, and the fifth one is gly, so the final sequence is NH2-tyr-phe-asp-met-gly-arg-phe-COOH
再问： pancreatic protease hydrolyze the polypeptide immediately after the carboxylic group of the acidic residue, that is phe，not asp.
