Method for acquiring information of target polypeptide and reagent kit

A method for acquiring information of a target polypeptide, comprising:

• acquiring a diffusion time of a fluorescently labeled target polypeptide and a diffusion time of each of a plurality of fluorescently labeled reference polypeptides by fluorescence correlation spectroscopy or fluorescence cross-correlation spectroscopy, and
• acquiring information on size of the fluorescently labeled target polypeptide from the diffusion time of the fluorescently labeled target polypeptide with reference to the diffusion times of the plurality of fluorescently labeled reference polypeptides,
• wherein information on size of each of the plurality of fluorescently labeled reference polypeptides is known,
• the sizes of the plurality of reference polypeptides are different from each other;
• the plurality of fluorescently labeled reference polypeptides comprises:
• a fluorescently labeled first reference polypeptide, which is a first reference polypeptide labeled with a fluorescent dye;
• and a fluorescently labeled second reference polypeptide, which is a second reference polypeptide labeled with the same fluorescent dye as the fluorescent dye of the fluorescently labeled first reference polypeptide,
• the fluorescently labeled first reference polypeptide and the fluorescently labeled second reference polypeptide are different in size from each other,
• before the step of acquiring diffusion time, dividing a specimen containing the target polypeptide collected from a living body into at least a first aliquot, a second aliquot and a third aliquot, fluorescently labeling the target polypeptide contained in the first aliquot to prepare the fluorescently labeled target polypeptide, mixing the second aliquot and the fluorescently labeled first reference polypeptide, and mixing the third aliquot and the fluorescently labeled second reference polypeptide,
• in the step of acquiring diffusion time, a diffusion time of the fluorescently labeled target polypeptide in the first aliquot, a diffusion time of the fluorescently labeled first reference polypeptide in the second aliquot and a diffusion time of the fluorescently labeled second reference polypeptide in the third aliquot are acquired, and
• in the step of acquiring the information, information on size of the fluorescently labeled target polypeptide is acquired from the diffusion time of the fluorescently labeled target polypeptide with reference to the diffusion time of the fluorescently labeled first reference polypeptide and the diffusion time of the fluorescently labeled second reference polypeptide.