A method for detecting a plurality of target protein molecules in a sample comprising: a. contacting a sample with a composition comprising a plurality of target probes, wherein each target probe in the plurality comprises: i. a target-binding molecule that specifically binds to a distinct target molecule in the sample; ii. an identification nucleotide sequence that identifies the target-binding molecule; and iii. a cleavable linker between the target-binding molecule and the identification nucleotide sequence; b. separating unbound target probes from a plurality of complexes in the sample, each complex having a target protein molecule and a single target probe bound thereto, wherein the complex does not have a second target probe binding to a different region of the target protein molecule; c. releasing the identification nucleotide sequences from the plurality of complexes; and d. detecting signals from the released identification nucleotide sequences based on a non-gel electrophoresis method without any amplification steps, wherein the signals are distinguishable for the identification nucleotide sequences, thereby identifying the corresponding target-binding molecules and detecting a plurality of different target molecules in the sample, and the method further comprising, prior to the detecting step (d), coupling the released identification nucleotide sequences from the releasing step (c) to a detection composition comprising a plurality of reporter probes, wherein each reporter probe in the plurality comprises: a first target probe-specific region that is capable of binding a first portion of the identification nucleotide sequence; and a detectable label that identifies the reporter probe, wherein the label creates a unique distinguishable signal for each reporter probe. a. contacting a sample with a composition comprising a plurality of target probes, wherein each target probe in the plurality comprises: i. a target-binding molecule that specifically binds to a distinct target molecule in the sample; ii. an identification nucleotide sequence that identifies the target-binding molecule; and iii. a cleavable linker between the target-binding molecule and the identification nucleotide sequence; i. a target-binding molecule that specifically binds to a distinct target molecule in the sample; ii. an identification nucleotide sequence that identifies the target-binding molecule; and iii. a cleavable linker between the target-binding molecule and the identification nucleotide sequence; b. separating unbound target probes from a plurality of complexes in the sample, each complex having a target protein molecule and a single target probe bound thereto, wherein the complex does not have a second target probe binding to a different region of the target protein molecule; c. releasing the identification nucleotide sequences from the plurality of complexes; and d. detecting signals from the released identification nucleotide sequences based on a non-gel electrophoresis method without any amplification steps, wherein the signals are distinguishable for the identification nucleotide sequences, thereby identifying the corresponding target-binding molecules and detecting a plurality of different target molecules in the sample, and