Fluorescence-detected magnetic circular dichroism of fluorescent and nonfluorescent molecules

Advantages of a synchrotron light source for fluorescence-detected linear dichroism

Fluorescence-detected linear dichroism (FD-LD) enables one to collect linear dichroism spectra for oriented fluorophores in the presence of other absorbing species and light scattering. The experiment proceeds by scanning the excitation wavelength and using a filter to collect only emitted photons from the fluorophore. Thus, it has the potential to give data with enhanced selectivity and quality. By using a synchrotron radiation light source and fluorescence-detection, we show data for a range of fluorophores in different orienting environments. Film and flow-oriented FD-LD spectra were collected down to 170 nm. Even for flow-oriented liposomes, we have data collected down to 210 nm. For strongly scattering samples, for example, liposomes, FD-LD has the clear advantage that scattering is absent for the longer wavelength fluorescence photons. The collimated and smaller beam size of the synchrotron radiation also gives rise to sharper and more well-defined features in the spectra.

Correlation of infrared spectroscopy with platelet morphology in blood compatibility studies of polydimethylsiloxane membranes

Oxygenator membranes, polydimethylsiloxane elastomer, exposed to flowing heparinized canine blood in a perfusion system have been studied with respect to the platelet activation and the morphology of the membranes. Utilizing Fourier transform infrared spectroscopy couple with attenuated total reflection technique (ATR) and laser Raman spectroscopy, no obvious differences in morphology and composition of the membranes have been detected while electron microscopic study shows difference in platelet aggregation.

Circular dichroism of hapten--antibody complexes: characterization of the combining sites of native and reformed MOPC-315 protein, its isolated subunits, and its Fv fragment

Extrinsic Cotton effects generated by binding haptens to native and reformed MOPC-315 protein, its subunits, and its Fv fragment have been examined. The identity of the combining sites of native and reassociated proteins and Fv-315 was demonstrated by the identity of their circular dichroism (CD) difference spectra. The spectrum of TNP-aminocaproate complexed with L chains differed in maxima and minima and cross-over points and lacked the 495-nm CD peak of TNP-aminocaproate-MOPC-315 protein and Nalpha-TNP-tryptophan spectra. A negative 293-nm tryptophanyl CD band, present in spectra of MOPC-315 protins and Fv-315 but absent from spectra of L and H chains, was blue-shifted by haptens and may represent electronic interactions occurring within the MOPC-315 combining site between tryptophanyl and chromophoric residues of different subunits. This conclusion is supported by molecular models of the MOPC-315 combining site.