Surface Plasmon Studies

101 and 102. Inset projected band structure and surface states A and B of the unreconstructed Au(lOO). After Ref. 86. 

The transverse electric fields inside ( - ) and outside (+) the solid, which are coupled to the charge density perturbation, are described by (we define the outer normal as the -1-z-direction)  

FIGURE 37. Normal-incidence ER effect monitoring the transition (5 x 20) (1 x 1) of Au(lOO) 

The dispersion relation for surface plasmons is derived from the usual boundary conditions as  

FIGURE 38. Surface plasmon dispersion curve (o(k ). k Wave vector due to roughness. The experimental arrangements due to Otto and Kretschmann for surface plasmon excitation in ATR are also shown. 

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P. Braun. Surf. Sci. 126,714,1983. VEELS study of bulk and surface plasmon energies across Al—Mg alloy phase diagram. 

Homola, J., "Thin Films Study by Means of Optically Excited Surface Plasmons, Nano 94—International Coirference on Nanometrology Scanning Probe Microscopy and Related Techniques, Proceedings, Nano 94, Bmo, Czech Rep., 1994, pp. 84-87. 

The affinity (interaction strength), multiple interactions, and the changes in concentration can be also monitored from those studies. To deliver data in real time, the natural phenomenon of surface plasmon resonance (SPR) is employed. Since the refractive index (r ) at the interface changes as molecules are immobilized on the sensor surface, instant measure of r provides real-time assessment. The Tlcxchip platform exploits grating-coupled SPR (GC-SPR) for this purpose. 

Hirata I, Hioki Y, Toda M, Kitazawa T, Murakami Y, Kitano E, Kitamura H, Ikada Y, Iwata H (2003) Deposition of complement protein C3b on mixed self-assembled monolayers carrying surface hydroxyl and methyl groups studied by surface plasmon resonance. J Biomed Mater Res 66A 669-676... 

Brockman JM, Fmtos AG, Com RM (1999) A multistep chemical modification procedure to create DNA arrays on gold surfaces for the study of protein-DNA interactions with surface plasmon resonance imaging. J Am Chem Soc 121 8044-8051... 

Wegner GJ, Lee NJ, Marriott G, Com RM (2003) Fabrication of histidine-tagged fusion protein arrays for surface plasmon resonance imaging studies of protein-protein and protein-DNA interactions. Anal Chem 75 4740-4746... 

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. 

L. Haussling, H. Ringsdorf, F.J. Schimitt, and W. Knoll, Biotin-functionalized self-assembled monolayers on gold-surface-plasmon optical studies of specific recognition reactions. Langmuir 7, 1837-184 (1991). 

Q. Hong, J.-L. Popot, J. H. Lakey (2003) Stabilising a membrane protein with amphipols for surface plasmon resonance ligand binding studies. In preparation... 

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. 

Surface plasmon resonance studies were employed to measure the equilibrium constants and association and dissociation rate constants of bisnaphthalimide derivatives (20, 21) with hairpin DNA immobilized on the metal surface.123 The equilibrium constants were higher and the dynamics slower for compounds 20 and 21 when compared to the equilibrium constants and dynamics of the model monomer (19). The values for ka and kd were determined from the change in the surface plasmon resonance signal when, respectively, the ligand solution was flowed over the... 

The effect of structural modification to 22 on the binding efficiency and binding dynamics of hairpin DNA immobilized on metal surfaces were studied using surface plasmon resonance.124,125 The association and dissociation kinetics were analyzed using a sequential model for the binding of the imidazole containing polyamides... 

The results summarized above were obtained by using fluorescence based assays employing phospholipid vesicles and fluorescent labeled lipopeptides. Recently, surface plasmon resonance (SPR) was developed as new a technique for the study of membrane association of lipidated peptides. Thus, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In SPR (surface plasmon resonance) systemsI713bl changes of the refractive index (RI) in the proximity of the sensor layer are monitored. In a commercial BIAcore system1341 the resonance signal is proportional to the mass of macromolecules bound to the membrane and allows analysis with a time resolution of seconds. Vesicles of defined size distribution were prepared from mixtures of lipids and biotinylated lipopeptides by extruder technique and fused with a alkane thiol surface of a hydrophobic SPR sensor. 

Lomakin et al., 1996). Surface plasmon resonance studies of the A/ (l—40) /1-amyloid peptide (Cannon et al., 2004) provide even more details of the multiple kinetic steps, and suggest that fibril formation proceeds by reversible addition of a monomer to the tip of the formed fibril, followed by a postbinding, transitional event. 

In transmission studies of small aluminum spheres, Batson (22) has shown details of the generation of surface plasmons in the aluminum and in the thin coating oxide layer. Marks (23) and Cowley (24) have examined the surface plasmons and surface state excitations of small MgO smoke crystals. It is clearly evident that these excitations may be produced by electron beams passing the crystal in the vacuum, 3 nm or more away from the surface. 

Surface-enhanced Raman scattering (SERS) has emerged as a powerful technique for studying species adsorbed on metal films, colloidal dispersions, and working electrodes. SERS occurs when molecules are adsorbed on certain metal surfaces, where Raman intensity enhancements of ca. 105-106 may be observed. The enhancement is primarily due to plasmon excitation at the metal surface, thus the effect is limited to Cu, Ag, and Au, and a few other metals for which surface plasmons are excited by visible radiation. 

The molecular interaction of cytochrome c and cardiolipin has been extensively studied. A mode of the interaction has been confirmed to be both electrostatic and hydrophobic, by using infrared spectroscopy (Choi and Swanson, 1995), fluorescence resonance energy transfer method (Rytdmaa and Kinnunen, 1994), protease digestion (de Jongh et al., 1995), cyclic voltammetry (Salamon and ToUin, 1997), deuterium and phosphorus NMR measurements (Spooner et al., 1993), and surface plasmon resonance spectroscopy (Salamon and Tollin, 1996). 

Rytdmaa, M., and Kinnunen, P.K.J., 1995, ReversibUity of the binding of cytochrome c to Uposomes. Implications for lipid-protein interactions./. B/oZ. Chem., 270 3197-3202 Salamon, Z., and ToUin, G., 1996, Surface plasmon resonance studies of complex formation between cytochrome c and bovine cytochrome c oxidase incorporated into a supported planar Upid bUayer. II. Binding of cytochrome c to oxidase-containing cardiohpin /phosphatidylcholine membranes. Biophys. J., 71 858-867 Salamon, Z., and ToUin, G., 1997, Interaction ofhorse heart cytochrome c with Upid bilayer membranes effects on redox potentials. J. Bioenerg. Biomembr. 29 211-221 Scarlett, J.L., and Murphy, M.P., 1997, Release of apoptogenic proteins from the... 

Finally, a recent paper by Gunther et aL shows that SEK uniquely binds to the T-cell receptor (human V/35.1) through a 15 amino-acid loop (q 3-/38) not evident in other superantigens, except for those in the same toxin grouping (e.g., SET). Surface plasmon resonance studies reveal a 6 (tmol binding affinity of SEK for V/35.1, which fits the range for other SEs when used in this technique. 

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