The low-molecular-weight compound represented by the general formula (1): ArX-(Linker)-ArYHB (1), wherein ArX is a structure containing an optionally substituted aromatic six-membered ring, ArYHB is a structure containing an optionally substituted aromatic six-membered ring having a proton donor, the atom group “Linker” has not less than 4 and not more than 30 atoms and binds ArX with ArYHB, is used for binding a proteinaceous substance.