Surface plasmon resonance study of the actin-myosin sarcomeric complex and tubulin dimers

Abstract

Biosensors based on the principle of surface plasmon resonance (SPR) detection were used to measure biomolecular interactions in sarcomeres and changes of the dielectric constant of tubulin samples with varying concentration. At SPR, photons of laser light efficiently excite surface plasmons propagating along a metal (gold) film. This resonance manifests itself as a sharp minimum in the reflection of the incident laser light and occurs at a characteristic angle.The dependence of the SPR angle on the dielectric permittivity of the sample medium adjacent to the gold film allows the monitoring of molecular interactions at the surface. We present results of measurements of cross-bridge attachment/detachment within intact mouse heart muscle sarcomeres and measurements on bovine tubulin molecules pertinent to cytoskeletal signal transduction models.

Resolving controversy of unusually high refractive index of a tubulin

“…The small discrepancies between the theory and experiment for n tub and dn/dc tub can be due to (i) the deviation of tubulin dimer shape from a spherical one assumed in the theory, (ii) small concentration uncertainties, (iii) effects of the buffer on dn/dc [25] or (iv) additional polarization effects in tubulin due to its large dipole moment [26,27]. The high-frequency polarizability (α tub ) of tubulin can [8,9] are at 760 nm and 26 • C and from Bon et al [2] for 527 nm and room temperature.…”

“…which with the calculated number density of molecules N = 8.7×10 21 molecules per m 3 at given concentration (C tub ) is equal to α tub = 1.1×10 −33 Cm 2 V −1 . What effect caused the high values of detected refractive index in the earlier experimental works [2,8,9] is unclear.…”

Microtubules as Active Tracks for Bi-Directional Cellular Traffic of Motor Proteins

“…2 The tubulin monomer contains approximately 450 amino acids comprising some 7000 atoms with a combined mass of 55 kDa. 3 (b) Tubulin's secondary structure is of crucial importance for the dynamical model applied in this article. This structure is dominated by α-helices, polypeptide wound chains of amino acids, represented by rods in Fig.…”

Towards Experimental Tests of Quantum Effects in Cytoskeletal Proteins

“…Fig. 12 shows the experimental arrangement of our custom-built SPR sensor [18,135,136]. In addition to the experimental arrangement shown, we used the commercial SPR-based BIAcore 3000 and 1000 sensors, which furnished the additional convenience of automated injection of very small volumes of analyte solutions and allowed for cross-checking of results.…”

“…Since the effective permittivities depend on the frequency of the exciting laser light, the resonance angle does too. The most convenient geometry for the development of a sensor is the Kretschmann-Raether configuration which consists of a glass prism, a metal film and the adjacent medium that is to be probed [135,136]. Fig.…”