Novel molecular recognition films were prepared from modified polysulfone having perillaldehyde moiety as a side group. The molecular recognition films were obtained from perillaldehyde polysulfone by adopting 9-ethyladenine as a print molecule. The molecular recognition phenomena were studied by surface plasmon resonance (SPR) spectroscopy. Adsorption of adenosine (As) and guanosine (Gs) in the molecularly imprinted film was studied. Dual adsorption isotherms were observed for As in 9-EA imprinted films, while nonspecific adsorption isotherms for Gs in those films. This revealed that the molecular recognition sites toward As were constructed in the films thus prepared. The apparent affinity constant toward As determined by using apparent adsorption isotherms ranged from 7.90 x 10(3) to 3.31 X 10(4) mol(-1) dm(3). (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2826-2832, 2008