The structural parameters of the adsorbed protein layers maybe obtained by using intrinsic fluorescence spectroscopy on chromatographic supports
(Oroszlan et al. 1990), on silica and chemically modified silica slides (Buijs and Hlady 1997; Iwamoto et al. 1985). Furthermore, fluorescence polarisation measurements enable the study of the orientation and the rotational mobility of adsorbed proteins (Bos and Kleijn 1995; Tronin et al. 2002). Side-on or end-on orientations of lysozyme on hydrophobic and hydrophilic surfaces were deduced from kinetic measurements using FTIR (Wertz and Santore 2002). In some cases, polarised ATR measurements may allow the determination of the interfacial orientation of the protein in the adsorbed layer and have been mainly used to analyse the predominantly helical proteins inserted in lipid films (Frey and Tamm 1991; Houbiers et al. 2001; Martin et al. 2003). The molecular order of the whole protein is generally inferred from the measured dichroic ratios obtained for the stereoregular a-helical domains of the protein (Martin et al. 2003; Methot et al. 1996). On solid support, the molecular orientation of an a-helical peptide could be determined thanks to the specific hydrophobic interaction between the amphipathic peptide with the CH3-terminated SAM (Noinville et al. 2003). The interpretation of polarised infrared data seems to be more difficult for the ^-sheeted structure (Chittur 1998).
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