Method for detecting mutations in target base sequence of nucleic acid, method for selectively inhibiting amplification of nucleic acid, and kit for implementing same

A kit comprising:

• a clamp nucleic acid having a base sequence complementary to the standard base sequence and containing at least one artificial nucleotide residue, and
• an amphoteric copolymer comprising a cationic constituent unit (1) with an amino group in its structure and an anionic constituent unit (2), wherein a molar ratio of the cationic constituent unit (1) to the anionic constituent unit (2) (cationic constituent unit (1)/anionic constituent unit (2)) is in the range of 0.13 to 1.62, and wherein at least some of the cationic constituent units (1) are a constituent unit (1-1), (1-3) or (1-4) having a structure represented by general formula (I-a), (I-b), (I-e) or (I-f), or a structure of an acid addition salt thereof:
• wherein R1 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms that may have a hydroxyl group, a cycloalkyl group having 5 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms,
• wherein R4 and R5 independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms that may have a hydroxyl group, an aralkyl group having 7 to 12 carbon atoms, or a cycloalkyl group having 5 to 6 carbon atoms, or
• wherein R6 represents a hydrogen atom or a methyl group, R7 and R8 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 2 to 4, and
• at least some of the anionic constituent units (2) are a constituent unit (2-1), (2-2) or (2-4) represented by general formula (II-a), (II-b) or (II-d):
• wherein R9 is hydrogen or a methyl group, and Y's each independently are hydrogen, Na, K, NH4, 1/2Ca, 1/2Mg, 1/2Fe, 1/3Al, or 1/3Fe for every carboxy group bonded thereto,
• wherein Y represents a hydrogen, Na, K, NH4, 1/2Ca, 1/2Mg, 1/2Fe, 1/3Al, or 1/3Fe independently for each carboxy group to be bonded, or
• wherein R10 is a hydrogen or a methyl group, and Y is a hydrogen, Na, K, NH4, 1/2Ca, 1/2Mg, 1/2Fe, 1/3Al, or 1/3Fe independently for each carboxy group to be bonded.

A method for suppressing amplification of a nucleic acid in a sample having a predetermined target base sequence in a nucleic acid amplification reaction, comprising:

• subjecting the nucleic acid in the sample to a nucleic acid amplification reaction as a template with
• a clamp nucleic acid having a base sequence complementary to the target base sequence and containing at least one artificial nucleic acid residue, and
• an amphoteric copolymer comprising a cationic constituent unit (1) with an amino group in its structure and an anionic constituent unit (2), wherein a molar ratio of the cationic constituent unit (1) to the anionic constituent unit (2) (cationic constituent unit (1)/anionic constituent unit (2)) is in a range of 0.13 to 1.62, and wherein at least some of the cationic constituent units (1) are a constituent unit (1-1), (1-3) or (1-4) having a structure represented by general formula (I-a), (I-b), (I-e) or (I-f), or a structure of an acid addition salt thereof:
• wherein R1 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms that may have a hydroxyl group, a cycloalkyl group having 5 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms,
• wherein R4 and R5 independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms that may have a hydroxyl group, an aralkyl group having 7 to 12 carbon atoms, or a cycloalkyl group having 5 to 6 carbon atoms, or
• wherein R6 represents a hydrogen atom or a methyl group, R7 and R8 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 2 to 4, and
• at least some of the anionic constituent units (2) are a constituent unit (2-1), (2-2) or (2-4) represented by general formula (II-a), (II-b) or (II-d):
• wherein R9 is hydrogen or a methyl group, and Y's each independently is hydrogen, Na, K, NH4, 1/2Ca, 1/2Mg, 1/2Fe, 1/3Al, or 1/3Fe for every carboxy group bonded thereto,
• wherein Y represents a hydrogen, Na, K, NH4, 1/2Ca, 1/2Mg, 1/2Fe, 1/3Al, or 1/3Fe independently for each carboxy group to be bonded, or
• wherein R10 is a hydrogen or a methyl group, and Y is a hydrogen, Na, K, NH4, 1/2Ca, 1/2Mg, 1/2Fe, 1/3Al, or 1/3Fe independently for each carboxy group to be bonded.