Molecular interactions fluorescence studies

Fluorescence polarization is also well suited to equilibrium binding studies when the free and bound species involved in the equilibrium have different rotational rates (Scheme 5.1). Most molecular interactions can be analyzed by this method. It should be emphasized that, in contrast to other methods using tracers, fluorescence polarization provides a direct measurement of the ratio of bound and free tracer without prior physical separation of these species. Moreover, measure-... 

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). 

The possibility to carry out conformational studies of peptides at low concentrations and in the presence of complex biological systems represents a major advantage of fluorescence spectroscopy over other techniques. Fluorescence quantum yield or lifetime determinations, anisotropy measurements and singlet-singlet resonance energy transfer experiments can be used to study the interaction of peptides with lipid micelles, membranes, proteins, or receptors. These fluorescence techniques can be used to determine binding parameters and to elucidate conformational aspects of the interaction of the peptide with a particular macro-molecular system. The limited scope of this chapter does not permit a comprehensive review of the numerous studies of this kind that have been carried and only a few general aspects are briefly discussed here. Fluorescence studies of peptide interactions with macromolecular systems published prior to 1984 have been reviewed. 

In 1962, Olson and Romano isolated and purified a water-soluble BChl a-protein from green bacteria. Soon afterwards, the crystalline form of the protein was also obtained . It was in fact the first photosynthetic pigment-protein to be crystallized. Chemical studies showed the BChl a-protein to have a molecular weight of 150 kDa and to contain 21 BChl a molecules. It has a major absorption band in the far-red at 809 nm, which is ascribed to the Qy transition of BChl a, and a corresponding fluorescence band at 818 nm. Its circular-dichroism spectrum in the far-red absorption-band region shows multiple components which can be interpreted in terms ofexciton interactions between the BChl a molecules " . Fluorescence studies of the BChl a-protein in situ indicate that it functions as an intermediate in exd-tation-energy transfer from BChl c in chlorosomes to the BChl-dimer reaction center, P840 ... 

Applications of these tunable VUV sources continue to be mostly in the detection of atoms and small molecules by laser-induced fluorescence in molecular beam scattering studies. Of particular importance has been the improved intensities available from Mg vapor, so that it will be possible, for example, to study the internal energy distributions in CO molecules following scattering from surfaces. This capability for both very sensitive and state-selective detection of small molecules will lead to important advances in our understanding of molecular interactions at surfaces. 

The molecular interactions between bis [4-(dimethylamino)phenyl]-squaraine 3 and polyvinylbutyral have been studied by fluorescence spectroscopy... 

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