The low-energy single-particle excitations of highly ordered C 60 chains adsorbed on a vicinal copper sub-strate are investigated by angle-resolved photoemission spectroscopy. The interface state previously identified on C 60 / Cu111 shows a one-dimensional dispersion on Cu553. In contrast, no significant momentum de-pendence is detected for emission from the lowest unoccupied molecular orbital LUMO. The LUMO displays similar phonon features as in C 60 / Cu111 but it does not peak toward the Fermi level for all considered potassium dopings and its photoemission lineshape is broader than in any other monolayer system investigated so far. This behavior is not easily reconciled with existing theory and indicates that the one-dimensional character of the chains affects the electronic structure of the monolayer in an intricate way.