Resonance angle shift

All proteins, independent on their aminoadd con odtion, aher the refi active index of water by a dmilar amount per unit mass, and thus there is a linear correlation between the surfiice concentration of protein and the resonance angle shift. 1000 resonance units (RU) corre ond to a 0.1° shift in the SPR angle and this is equivalent to a surfiice concentration change of about 1 ng mmr. ... 

Figure 2. Resonant angle shift due to a change in the outer refractive index.

As a quantitative measure of the far-held performance, two quantities may be introduced. First of all, sensitivity enhancement factor (SEF), a ratio of resonance angle shift due to target analyte binding on a nanowire-based biosensor to that of a conventional SPR structure using a thin gold him with equal thickness, is defined as... 

FIGURE 4.2.7 Relationship between gel layer thickness and maximum resonance angle shift of IgG-immobilized gel... 

FIGURE 4.2.10 Resonance angle shift of (a) ConA-imprinted hydrogel layer chip (solid line) and (b) nonimprinted hydrogel layer chip (dashed line) in PBS containing 1 xM ConA as an analyte. Reproduced from Ref. [201 with permission from Chemical Society of Japan, Copyright (2014). 

The reflectivity curve obtained for the film was shifted to higher angle as the number of layer increases around 42-45°. The thickness of the films was calculated from the resonance angle shift by a modified Fresnel equation. The calculated average thickness of self-assembled Zr EPPI film was 13.1 A and this value was similar to ellipsometric results. 

Fig. 10. A SPR Detection realized in a BIAcore system. A fan of polarized light passes a prism and is focused at the interface to an aqueous phase under conditions of total reflection. An evanescent wave enters the solvent phase. If the prism is coated with a thin gold layer at the interface the free electrons in the metal absorb energy from the evanescent wave for a distinct angle, depending on the refractive index of the solvent near the interface. B The gold layer can be modified with, e.g., a carboxydextrane matrix, where catcher molecules can be immobilized by standard chemistry. If a ligand is applied with the aqueous phase it may interact with the catcher and accumulate in the matrix, causing a shift in the resonance angle. If no specific binding occurs the refractive index in proximity of the sensor is less affected...

Fig. 8.28 (a) Resonance spectra for three different fluidic refractive indices and (b) resonant wavelength shift as a function of liquid refractive index change in the microtube at the incident angle of 37.5°. Reprinted from Ref. 68 with permission. 2008 Optical Society of America... 

Surface plasmon resonance (SPR) technique had become popular in interaction studies between biological molecules (1). It is an optical biosensor, and the interactions can be detected by SPR angle shift or reflection light intensity. In typical SPR measurement, one of pair interacting biomolecules was immobilized on a gold chip, and another was flowed over the chip as its solution. There are two major advantages in SPR assay (a) real time evaluations on kinetics studies and (b) label-free measurements. 

Nelson, B. P., Frutos, A. G., Brockman, J. M. and Corn, R. M. (1999) Near-infrared surface plasmon resonance measurements of ultrathin films. 1. Angle shift and SPR imaging experiments. Anal. Chem. 71, 3928-3934. 

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