Development of Surface Plasmon Resonance-type Quartz Crystal Microbalance and Detection of Interactions of Viomolecules

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By using a 27-MHz piezoelectric quartz oscillator connected with a vector network analyzer, we obtained resonance frequency decreases (-ΔF_<water>) and energy dissipation increases (ΔD_<water>) during binding of biotinylated BSA (bovine serum albumin), biotinylated ssDNA, biotinylated dsDNA, and biotinylated pullulan to a NeutrAvidin-immobilized 27-MHz QCM (quartz crystal microbalance) plate in aqueous solution, as well as in the wet air phase (97% humidity, -ΔF_<wet> and ΔD_<wet>) and in the dry air phase (-ΔF_<air> and ΔD_<air>). The -ΔF_<air> value indicates real mass changes due to the binding of these biomolecules. Values for polystyrene were also obtained as elastic and hydrophobic membranes. In terms of results, (-ΔF_<wet>)/(-ΔF_<air>) values indicated the binding water ratio per unit biomolecular mass were in the order of pullulan (2.1- 2.2) > DNAs = proteins (1.4- 1.6) > polystyrene (1.0). The (-ΔF_<water>)/(-ΔF_<air>) values indicated the hydrodynamic water (binding and vibrating water) ratio per unit biomolecular mass were in the order of dsDNA (6.5)> ssDNA = pullulan (3.5- 4.4) > proteins (2.4- 2.5) > polystyrene (1.0). The aforementioned values suggest that the energy dissipation of proteins was mainly caused by hydration and that proteins themselves are elastic molecules without energy dissipation in aqueous solutions. On the contrary, plots in cases of DNAs and pullulans were relatively deviant toward the large hydration and energy dissipation from the linearity observed with proteins, meaning that the large energy dissipation occurs because of viscoelastic properties of linear DNAs and pullulans in the water phase, in addition to energy dissipation due to the hydration of molecules.