Surface plasmon resonance techniques

Apart from optical microscopy, there are some other optical techniques which are truly surface sensitive and have found widespread use. Examples are ellipsometry (see Section 9.4.1), total internal reflection fluorescence (TIRF) [316], and surface plasmon resonance techniques [348],... 

Zhang, W.-W., Y.-C. Chen, Z.-F. Luo, et al. 2007. Analysis of 17[beta]-estradiol from sewage in coastal marine environment by surface plasmon resonance technique. Chem. Res. Chinese Univers. 23 404-407. 

The attachment of protein to the transducer surface for immunoassay is a difficult problem, since it must be achieved without interfering with the active site. If an unlabeled assay is to be performed it must also be such that subsequent non specific interaction with the surface can be inhibited. This requirement is often contrary to those for effective antibody-antigen complex formation. A surface close packed with antibody will be sterically hindered and its reaction with antigen inhibited. On the other hand, a suitably spaced packing allows non-specific interactions to occur and large false positive signals to be recorded. As mentioned earlier, this was demonstrated by Cullen and Lowe who used the surface plasmon resonance technique to probe specific and non-specific protein interactions at metal surfaces. (23). 

Li B, Che J, Long M (2008) Measuring binding kinetics of surface-bound molecules using the surface plasmon resonance technique. Anal Biochem 377 195-201... 

Figure 4.17. Schematic diagrams illustrating the basis of the surface plasmon resonance technique. Top A beam of radiation striking the back surface of a glass prism coated with a metal film usually evaporated silver). The reflected intensity and angle of reflection are extremely sensitive to variations in the dielectric on the metal surface. Bottom Shift in the R vs. 0 plot when the organic film is exposed to a gas.

Once chemoenzymatically produced, these unnatural sialosides have demonstrated utility in a variety of biological applications. A sialoside consisting of 9-0-acetylated sialyl Tn antigen (sTn) was produced by one-pot synthesis and conjugated to human serum albumin to be used to evaluate the role of acetylation in carbohydrate-protein interactions. Para-nitrophenol-tagged sialosides can be used in a colorimetric assay to evaluate sialidase specificity. Biotin-tagged sialosides have been immobilized on a streptavidin-coated surface to study protein-carbohydrate interactions with surface plasmon resonance techniques. Size-defined... 

THE USE OF THE SURFACE PLASMON RESONANCE TECHNIQUE IN NON-LINEAR OPTICS.605... 

The Surface Plasmon Resonance technique has proved to be very versatile, finding a number of applications where small changes in the properties of a material characterise a physical change in the vicinity of the measurement [2]. As a technique for investigating the linear and non-linear bulk optical properties of novel materials in thin film form, the SPR method is both accurate and sensitive [3]. For non-linear organic materials, particularly in LB film form, information on film thickness, refractive index and electro-optic coefficient may be straightforwardly obtained by computer analysis, even for a molecular monolayer with thiclmess of the order of only 3 nm or less. 

Arya SK et al (2006) Application of octadecanethiol self-assembled monolayer to cholesterol biosensor based on surface plasmon resonance technique. Talanta 69(4) 918-926... 

Arya SK et al (2007) Poly-(3-hexylthiophene) self-assembled monolayer based cholesterol biosensor using surface plasmon resonance technique. Biosens Bioelectron 22(ll) 2516-2524... 

Figure 3.13 Electro-optic measurements using the surface plasmon resonance technique indicating (a) the experimental configuration and (b) an experimental differential reflectivity plot indicating a high second-order nonlinear effect.

There are a few other surface-sensitive characterization techniques that also rely on the use of lasers. For instance surface-plasmon resonance (SPR) measurements have been used to follow changes in surface optical properties as a fiinction of time as the sample is modified by, for instance, adsorption processes [ ]. SPR has proven usefiil to image adsorption patterns on surfaces as well [59]. 

There are several other techniques Uke the fluorescent dye displacement assays, footprinting, Fourier transform infrared spectroscopy. X-ray crystallography, electron microscopy, confocal microscopy, atomic force microscopy, surface plasmon resonance etc used for hgand-DNA interactions that are not discussed here. 

The techniques developed to study protein interactions can be divided into a number of major categories (Table 31.1), including bioconjugation, protein interaction mapping, affinity capture, two-hybrid techniques, protein probing, and instrumental analysis (i.e., NMR, crystallography, mass spectrometry, and surface plasmon resonance). Many of these methods are dependent on the use of an initial bioconjugation step to discern key information on protein interaction partners. 

The dynamics of intercalation of small molecules with DNA, groove binding and binding to specific sites, such as base pair mismatches have been studied by stopped-flow,23,80 108 temperature jump experiments,26,27,94 109 120 surface plasmon resonance,121 129 NMR,86,130 135 flash photolysis,136 138 and fluorescence correlation spectroscopy.64 The application of the various techniques to study the binding dynamics of small molecules will be analyzed for specific examples of each type of binding. 

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