Fluorescent probes for biological studies

A compound of the formula (IV):

• where R4, R5, R6, R7, R8, and R9 are each independently hydrogen, fluorine, or alkyl, with the proviso that one of R6 or R7 is —NR1R2, —OR1, or —SR1;
• R1 and R2 are each independently hydrogen or alkyl;
• or
• R1 and R2 together with the nitrogen to which they are attached, may form a substituted or unsubstituted 5- or 6-membered ring;
• wherein said nitrogen is not conjugated with said 5- or 6-membered ring;
• Y is NH2 or C(O)X;
• X is halogen, hydroxy or alkoxy;
• and
• n is 1, 2, 3, or 4.

A peptide comprising at least two amino acids linked via a peptide bond wherein at least one of the amino acids is of the formula (I):

• where R4, R5, R6, R7, R8, and R9 are each independently hydrogen, fluorine, or alkyl, with the proviso that one of R6 or R7 is —NR1R2, —OR1, or —SR1;
• R1 and R2 are each independently hydrogen or alkyl;
• or
• R1 and R2 together with the nitrogen to which they are attached, may form a substituted or unsubstituted 5- or 6-membered ring;
• wherein said nitrogen is not conjugated with said 5- or 6-membered ring;
• R3 is hydrogen or a N-protecting group;
• n is 1, 2, 3 or 4.

A method of probing biological interactions comprising:

• (a) incorporating the amino acid of formula (I) into a peptide
• where R4, R5, R6, R7, R8, and R9 are each independently hydrogen, fluorine, or alkyl, with the proviso that one of R6 or R7 is —NR1R2, —OR1, or —SR1;
• R1 and R2 are each independently hydrogen or alkyl;
• or
• R1 and R2 together with the nitrogen to which they are attached, may form a substituted or unsubstituted 5- or 6-membered ring;
• wherein said nitrogen is not conjugated with said 5- or 6-membered ring;
• R3 is hydrogen or a N-protecting group;
• n is 1, 2, 3 or 4;
• (b) contacting a target molecule with said peptide to form a biological sample;
• (c) monitoring the fluorescence of said biological sample.