SPR sensors

Surface plasmon resonance boundary Coupling layer Metal layer 

FIGURE 1.2 Schematic drawing showing SPR sensor with different configurations  

Surface immobilization of the capture molecules follows standard procedures that are commonly practiced in many biosensor applications and some are discussed in the previous section. Layers of carboxymethyl dextran. Protein A or Protein G, streptavidin-coated surface, or EDC [N-ethyl-N-(diethylaminopropyl) carbidimide]/NHS (N-hydroxysuccmimide)-based amine coupling through amide bond are used for protein (antibody, receptor, etc.) cross-linking. 

Instrument, Dallas, TX), SPR spectroscope (Multiscop , Optrel GbR, Germany), Reichert SR7000 (Reichert Analytical Instruments, Depew, NY), and resonant mirror based lAsys (Thermo Labsystems, Cambridge, UK). 

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Fig. 13a-e. The increase of the signal intensities by the addition of the dendritic complexes composed of IgGs and protein A. The hapten was immobilized to the surface of the SPR sensor chip. The increase of the signal intensities on the complex formation of hapten with the antibodies were monitored. The addition of mouse IgG specific for hapten (Abl) (a), the complex of the Abl with protein A (b), one to one complex of Abl with anti-mouse IgG (Fc) antibody (Ab2) (c), two to one complex of Abl with Ab2 (d), and two to one complex of Abl with Ab2 in the presence of protein A (e)... 

Bardin F., Kasik I., Trouillet A. et.al., SPR sensor using an optical fiber with IGI profile, Appl. Opt. 2002 41 2514-2520. 

Large analytes targeted by affinity biosensor technology include bacterial pathogens such as Escherichia coli, Salmonella enteritidis, and Listeria monocytogenes. Salmonella enteritidis and Listeria monocytogenes were detected by an SPR sensor at concentrations down to 106 cfu/ml27. 

As well as fluorescence-based assays, artificial membranes on the surface of biosensors offered new tools for the study of lipopeptides. In a commercial BIA-core system [231] a hydrophobic SPR sensor with an alkane thiol surface was incubated with vesicles of defined size distribution generating a hybrid membrane by fusion of the lipid vesicles with the alkane thiol layer [232]. If the vesicles contain biotinylated lipopeptides their membrane anchoring can be analyzed by incubation with streptavidine. Accordingly, experiments with lipopeptides representing the C-terminal sequence of N-Ras show clear differences between single and double hydrophobic modified peptides in their ability to persist in the lipid layer [233]. 

Thus lipoproteins could be injected over the surface of a lipid covered SPR sensor in a detergent free buffer solution, and showed spontaneous insertion into the artificial membrane [234]. Again, two hydrophobic modifications are... 

In the simplest case a 1 1 complex is formed between the host in solution and the guest immobilized on the surface. The response of the SPR sensor, R, is proportional to the concentration of the complex formed, and thus pseudo-first-order rate equations can be used to analyze the data.73 If no host is initially bound the function for R... 

Fig. 9.10 The calculated angular reflection spectra for an SPR sensor with and without a 2 nm thick film on the gold surface. The assumed film index is n 1.5. The diagram at right shows the schematic prism coupling geometry for measuring the SPR reflectivity angle dependence...

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. 

Thus, lipoproteins could be injected over the surface of a lipid covered SPR sensor in a detergent free buffer solution and showed spontaneous insertion into the artificial membrane.171 Again two hydro-phobic modifications are necessary for stable insertion into the lipid layer, whereas lipoproteins with a farnesyl group only dissociate significantly faster out of the membrane. Therefore the isoprenylation of a protein is sufficient to allow interaction with membraneous structures, while trapping of the molecule at a particular location requires a second hydrophobic anchor. Interaction between the Ras protein and its effector Raf-kinase depends on complex formation of Ras with GTP (instead of the Ras GDP complex, present in the resting cell). If a synthetically modified Ras protein with a palmi-... 

Figure 5. SPR sensor based on ATR method and angular modulations (upper) and corresponding reflectivity calculated for two different refractive indices of sample (lower). Sensor configuration SF14 glass prism, 50 nm thick gold layer, sample, wavelength - 682 nm.

Figure 9. SPR sensor with four parallel sensing channels (provided hy S. Lolas, Biacore AB.)...

Fig. In prism-based SPR sensors with wavelength modulation and...

Direct detection of Staphylococcal enterotoxins B (SEB) is illustrated in Fig. 14 which shows binding of SEB to the wavelength-modulated SPR sensor surface coated with respective antibodies for five different SEB concentrations". Figure 15 shows the sensor response to binding after 30-minute SEB incubation and initial binding rate as a function of SEB... 

Figure 14. SPR sensor-based detection of Staphylococcal enterotoxin B (SEB) ...

Figure 3. Portable SPR sensor prototype system including sensor, optics, electronics and flow delivery system.

Figure 7. Comparison of the normalized signal of the MOSPR and the SPR sensors due to refractive index changes and evaluation their sensitivity.

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