Total internal reflectance fluorescence polarization

Recently, a formalism has been developed to determine the second and the fourth order parameters of films using polarized total internal reflection fluorescence (TIRF) [71]. Similarly to IR-ATR spectroscopy (Section 4), the experiment makes use of p- and s-polarized excitation, but the fluorescence emission (analyzed either in p- or s-direction) is detected normal to the substrate. Two approaches are developed based on the measurements of two intensity ratios. In the first one, the S angle has to be known experimentally or theoretically, and the order parameters (P2) and (P4) can be determined. In the second one, the order parameter (R ) is obtained by another technique, for instance IR-ATR spectroscopy, which allows deducing the order parameter (P4) and (cos2<5). 

Among the other spectroscopies, either in the direct or reflection mode, fluorescence spectroscopy may be mentioned. A promising variant is Total Internal Reflection Fluorescence spectroscopy (TIRF). The decay rate of an excited fluorescing probe is usually Interpreted in terms of the local fluidity and polarity. The technique has been used to estimate the extent of ordering inside adsorbed surfactant layers, but this is not an absolute method because a fluorescent probe has to be inserted, and such probes themselves affect the local fluidity. More rigorous are fluorescence experiments with molecules that possess such a probe as an intrinsic part of their structure, such as tryptophans in... 

In general, a vast number of optical transduction techniques can be used for biosensor development. These may employ linear optical phenomenon (e.g. adsorption, fluorescence, phosphorescence, and polarization) or nonlinear phenomena (e.g. second harmonic generation). The choice of a particular optical method depends on the analyte and the sensitivity needed. Total internal reflection fluorescence (TIRF) has been used with planar and fibre-optic wave-guides as signal transducers in a number of biosensors. 

Oreopoulos, J., Epand, R. E, Epand, R. M., and Yip, C. M. 2010. Peptide-induced domain formation in supported lipid bilayers Direct evidence by combined atomic force and polarized total internal reflection fluorescence microscopy, Biophys J 98,815-823. 

Sund, S.E., Swanson, J.A., Axelrod, D. Cell membrane orientation visualized by polarized total internal reflection fluorescence. Biophys. J. 77, 2266-2283 (1999)... 

Further structural information has been derived from the recent use of optical spectroscopy as a probe of structure at the L-L interface the two general approaches pursued are (i) total internal reflectance (TIR) fluorescence spectroscopy of adsorbed solute species and (ii) nonlinear spectroscopic methods to generate interface-sensitive spectra of the solvent molecules in the interfacial region. The former approach uses the polarization of the emitted signal, from an s-polarized excitation, to determine the effective dimensionality of the interface. The anisotropy of the fluorescent response from an interface that is flat on the length-scale of the adsorbed probe ( lnm) is [33]... 

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