Abstract: A method for differentiating between a post-translationally modified peptide and a peptide contained in a sample, comprising: (a) contacting the sample with a peptide attachment surface to create a peptidized surface, wherein the sample includes at least one functional group; (b) contacting the peptidized surface with a recognition reagent that selectively binds or forms a complex with the post-translationally modified peptide in the sample to provide an incubated surface; and (c) contacting a liquid crystal with the incubated surface and detecting presence of post-translationally modified peptide in the sample with the liquid crystal.