▎ 摘　　要

NOVELTY - Polypeptide molecules comprising fully defined sequence of amino acids (SEQ ID NO:1-4) as given in the specification, is new. USE - The polypeptide molecules and fluorescently labeled polypeptide are useful for detecting protease activity in blood sample and evaluating quality of blood samples (all claimed). ADVANTAGE - The method: improves the quality of blood samples used in scientific research, clinical medicine, biological sample banks and other fields; and avoids laboratory or clinical medical data errors caused by the decline in sample quality. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) fluorescently labeled polypeptide whose structural equation is P-F, where P is the polypeptide molecule, and F is a fluorescent group, and the two are ligated by using a covalent bond, and the fluorescent group is 5-(2-aminoethylamino)-1-naphthalenesulfonic acid (EDANS), , 7-methoxycoumarin-4-acetic acid (MCA) 5-FAM or rhodamine; (2) kit comprising the fluorescently labeled polypeptide and a fluorescence quencher, where the fluorescence quencher is graphene oxide; and (3) evaluating the quality of a blood sample, comprising using protease activity in the blood sample as a quality parameter for evaluating the blood sample, and using the polypeptide molecule or the fluorescently-labeled polypeptide as a protease substrate for detecting the activity of the protease.