# US 2019/0376958 A1 · Kit for detecting antigen or measuring its amount > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0376958 A1 - Document ID: US20190376958A1 - Status: Published application - Kind: A1 - Application number: 16/484,376 - Filed: 2018-01-17 - Published: 2019-12-12 - Earliest claimed: 2017-02-08 - Assignees: Tokyo Institute of Technology - Applicants: Tokyo Institute of Technology - Inventors: Hiroshi UEDA; Yuki OHMURO; Chihiro MIYAKE; Tomoya TSUKAHARA - Web page: https://patentgrep.com/patent/US20190376958A1 ## CPC - G01N 33/542: with steric inhibition or signal modification, e.g. fluorescent quenching - C07K 14/30: from Mycoplasmatales, e.g. Pleuropneumonia-like organisms [PPLO] - G01N 33/582: {with fluorescent label} - G01N 33/6854: {Immunoglobulins} - G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q) - C07K: PEPTIDES (peptides in foodstuffs A23; obtaining protein compositions for foodstuffs, working-up proteins for foodstuffs A23J; preparations for medicinal purposes A61K; peptides containing beta-lactam rings C07D; cyclic dipeptides not having in their molecule any other peptide link than those which form their ring, e.g. piperazine-2,5-diones, C07D; ergot alkaloids of the cyclic peptide type C07D519/02; macromolecular compounds having statistically distributed amino acid units in their molecules, i.e. when the preparation does not provide for a specific; but for a random sequence of the amino acid units, homopolyamides and block copolyamides derived from amino acids C08G69/00; macromolecular products derived from proteins C08H1/00; preparation of glue or gelatine C09H; single cell proteins, enzymes C12N; genetic engineering processes for obtaining peptides C12N15/00; compositions for measuring or testing processes involving enzymes C12Q; investigation or analysis of biological material G01N33/00) ## Abstract The purpose of the present invention is to develop a kit capable of detecting antigen or measuring its amount with high sensitivity without requiring an immobilization step and a washing step. The present invention provides a kit for detecting antigen or measuring its amount. The kit comprises a complex of a polypeptide including an antibody light chain variable region and a polypeptide including an antibody heavy chain variable region and a protein M fragment labeled with a fluorescent dye. The protein M fragment is a fragment having a binding ability to the complex. ## Claims ### Claim 1 A kit for detecting antigen or measuring its amount, comprising a complex composed of a polypeptide including an antibody light chain variable region and a polypeptide including an antibody heavy chain variable region and a protein M fragment labeled with a fluorescent dye, wherein the protein M fragment is a fragment having a binding ability to the complex. ### Claim 2 (depends on 1) The kit for detecting antigen or measuring its amount according to claim 1, wherein the protein M fragment is a fragment including all or part of the C-terminal subdomain of protein M. ### Claim 3 (depends on 1) The kit for detecting antigen or measuring its amount according to claim 1, wherein the protein M fragment is a fragment having deletion of 50 to 100 amino acid residues at the N-terminal side and 50 to 100 amino acid residues at the C-terminal side of protein M. ### Claim 4 (depends on 1) The kit for detecting antigen or measuring its amount according to claim 1, wherein the complex composed of a polypeptide including an antibody light chain variable region and a polypeptide including an antibody heavy chain variable region is a full-length antibody. ### Claim 5 (depends on 1) The kit for detecting antigen or measuring its amount according to claim 1, wherein the fluorescent dye labels the C-terminal side of the protein M fragment. ### Claim 6 (depends on 1) The kit for detecting antigen or measuring its amount according to claim 1, wherein the protein M fragment is labeled with two fluorescent dyes. ### Claim 7 (depends on 6) The kit for detecting antigen or measuring its amount according to claim 6, wherein the two fluorescent dyes are a rhodamine dye and a green fluorescent protein (GFP) or a variant thereof. ### Claim 8 A method for detecting antigen or measuring its amount in a sample, comprising sequentially performing steps (1) to (3): (1) bringing a sample into contact with a complex composed of a polypeptide including an antibody light chain variable region and a polypeptide including an antibody heavy chain variable region in the presence of a protein M fragment labeled with a fluorescent dye, wherein the protein M fragment is a fragment having a binding ability to the complex; (2) measuring the fluorescence intensity of the fluorescent dye; and (3) judging presence of an antigen in the sample from the fluorescence intensity or calculating an antigen level in the sample from the fluorescence intensity. ### Claim 9 (depends on 8) The method for detecting antigen or measuring its amount according to claim 8, wherein the protein M fragment is a fragment including all or part of the C-terminal subdomain of protein M. ### Claim 10 (depends on 8) The method for detecting antigen or measuring its amount according to claim 8, wherein the protein M fragment is a fragment having deletion of 50 to 100 amino acid residues at the N-terminal side and 50 to 100 amino acid residues at the C-terminal side of protein M. ### Claim 11 (depends on 8) The method for detecting antigen or measuring its amount according to claim 8, wherein the complex composed of a polypeptide including an antibody light chain variable region and a polypeptide including an antibody heavy chain variable region is a full-length antibody. ### Claim 12 (depends on 8) The method for detecting antigen or measuring its amount according to claim 8, wherein the fluorescent dye labels the C-terminal side of the protein M fragment. ### Claim 13 (depends on 8) The method for detecting antigen or measuring its amount according to claim 8, wherein the protein M fragment is labeled with two fluorescent dyes. ### Claim 14 (depends on 13) The method for detecting antigen or measuring its amount according to claim 13, wherein the two fluorescent dyes are a rhodamine dye and GFP or a variant thereof.