A compound according to Formula IV: or a pharmaceutically acceptable salt thereof, wherein Z is (a) or and A 4 is a bond, -(OCH 2 CH 2) n -, or -NHC CH 2 (OCH 2 CH 2) n -, wherein n is independently 1 or 2; or (b) Z-A 4 - is wherein R* is 123 I, 125 I, 131 I, or 18 F, L is a bond, or -(OCH 2 CH 2) n -; wherein n is independently 1 or 2; wherein Y 10 is CH or N; W has the structure: wherein R 20 and R 21 are each independently an amino acid residue linked via an amino group thereof to the adjacent -C - group; or W has the structure: wherein R 2 is hydrogen or a carboxylic acid protecting group G is O, S, or NR 3; R 1 is hydrogen or a carboxylic acid protecting group; R 3 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, alkylaryl, and heteroaryl. R 11, R 12, R 13, R 14, R 15, and R 16 are each independently hydrogen, alkyl, alkoxyl, or halide; R 17 and R 18 are each independently hydrogen, alkyl, aryl, or alkylaryl; R 19 is selected from the group consisting of alkyl, alkoxyl, halide, haloalkyl, and CN; m is an integer from 1 to 6; and o is an integer from 0 to 4, wherein when o is greater than 1, each R 19 is the same or different. Z is (a) or and A 4 is a bond, -(OCH 2 CH 2) n -, or -NHC CH 2 (OCH 2 CH 2) n -, wherein n is independently 1 or 2; or (b) Z-A 4 - is wherein R* is 123 I, 125 I, 131 I, or 18 F, L is a bond, or -(OCH 2 CH 2) n -; wherein n is independently 1 or 2; (a) or and A 4 is a bond, -(OCH 2 CH 2) n -, or -NHC CH 2 (OCH 2 CH 2) n -, wherein n is independently 1 or 2; or (b) Z-A 4 - is wherein R* is 123 I, 125 I, 131 I, or 18 F, L is a bond, or -(OCH 2 CH 2) n -; wherein n is independently 1 or 2; wherein R* is 123 I, 125 I, 131 I, or 18 F, L is a bond, or -(OCH 2 CH 2) n -; wherein n is independently 1 or 2; wherein Y 10 is CH or N; W has the structure: wherein R 20 and R 21 are each independently an amino acid residue linked via an amino group thereof to the adjacent -C - group; or W has the structure: wherein R 2 is hydrogen or a carboxylic acid protecting group G is O, S, or NR 3; R 1 is hydrogen or a carboxylic acid protecting group; R 3 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, alkylaryl, and heteroaryl. R 11, R 12, R 13, R 14, R 15, and R 16 are each independently hydrogen, alkyl, alkoxyl, or halide; R 17 and R 18 are each independently hydrogen, alkyl, aryl, or alkylaryl; R 19 is selected from the group consisting of alkyl, alkoxyl, halide, haloalkyl, and CN; m is an integer from 1 to 6; and o is an integer from 0 to 4, wherein when o is greater than 1, each R 19 is the same or different. wherein R 2 is hydrogen or a carboxylic acid protecting group G is O, S, or NR 3; R 1 is hydrogen or a carboxylic acid protecting group; R 3 is selected from the group consisting of hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, alkylaryl, and heteroaryl. R 11, R 12, R 13, R 14, R 15, and R 16 are each independently hydrogen, alkyl, alkoxyl, or halide; R 17 and R 18 are each independently hydrogen, alkyl, aryl, or alkylaryl; R 19 is selected from the group consisting of alkyl, alkoxyl, halide, haloalkyl, and CN; m is an integer from 1 to 6; and o is an integer from 0 to 4, wherein when o is greater than 1, each R 19 is the same or different.