Fluorescent probes

A compound represented by the following general formula (I) or a salt thereof:

• where:
• A and B each independently represent an amino acid residue, and the amino acid residues may be identical to or different from each other,
• where a bond between A and NH bonded to A is an amide bond between a C-terminal of A and the NH, A and B are bonded through an amide bond, and a bond between B and a carbonyl group (C═O) bonded to B is an amide bond between an N-terminal of B and the carbonyl group (C═O);
• R1s may be identical to or different from each other, and each represent a substituent bonded to a benzene ring;
• “p” represents an integer of from 0 to 4;
• R2, R3, R4, R5, R6, and R7 each independently represent a hydrogen atom, a hydroxyl group (OH group), a halogen atom, or a linear, branched, or cyclic alkyl group that may be substituted;
• R8 and R9 each independently represent a hydrogen atom, or a linear, branched, or cyclic alkyl group that may be substituted, or R8 and R9 may be bonded to form a ring, or R3 and R8 may be bonded to form a ring, and/or R4 and R9 may be bonded to form a ring;
• X represents a linear or branched C1 to C3 alkylene group;
• R10 and R11 each independently represent a hydrogen atom, a hydroxyl group (OH), an alkoxy group, or a linear, branched, or cyclic alkyl group that may be substituted, or R10 and R11 may be bonded to form a ring;
• R12 represents a hydrogen atom, a linear, branched, or cyclic alkyl group that may be substituted, a linear or branched alkenyl group that may be substituted, a linear or branched alkynyl group that may be substituted, an aryl group that may be substituted, or a heterocyclic group that may be substituted, or R2 may be bonded to R10 or R11 to form a ring;
• and
• L represents an amide bond, an ester bond, or -(linear or branched alkylene-O—)n— where “n” represents an integer of from 1 to 10, or L represents a single bond.