We present a comparative theoretical study on a novel class of materials which can be used as biomarkers, namely the oligothiophene-N-succinimidyl esters. We study by ab initio coupled-cluster and first-principles density-functional theory calculations the electronic structure and the optical properties of a model system, namely bithiophene-N-succinimidyl, both isolated and coupled to a –C(O)–NH–(CH2)3CH3 group at one terminal position. The latter is supposed to simulate the molecule after the binding to a biomolecule. We show that, although the electronic and optical properties of the isolated molecule are different from those of bithiophene, the binding to a biomolecule almost restores the well known electronic and optical properties of bithiophene.