Probing the dynamics of a confined enzyme by surface plasmon resonance

Despite sustained theoretical and experimental efforts during the last decades, the question of the role of protein dynamics (slow modes) on their function still awaits some answers. We propose in this paper a dynamical description of an immobilized layer of enzymes which aims at characterizing their low frequency conformational dynamics. The dynamical response of a single layer of phosphoglycerate kinases (PGK, a glycolytic enzyme) in the presence of its substrates (3PG, ATP, ADP) is recorded through the shift of the surface plasmon resonance (SPR) minimum. The comparison of these signals with those obtained without the enzyme provides evidence for the enhancement of the temporal fluctuations in the presence of the protein and therefore a signature of its conformational and/or positional fluctuations. These observations suggest that the SPR technique may be used as a very sensitive tool for probing the dynamics of fluid layers.