Christian Blum

Intrinsic conformer jumps observed by single molecule spectroscopy in real time

Abstract Single molecule spectral dynamics originate from changes (1) within the chromophore and (2) in the chromophoric environment, hence are intrinsic and extrinsic. To interpret spectral phenomena of intrinsic origin, assignment of fluorescence behaviour to distinct molecular states is required. We realized this by means of a perylene based chromophore with an amino substituent. The fluorescence spectrum of this dye depends strongly on the amino group conformation relative to the chromophore. Thus different conformers of the chromophore can be distinguished. Here we evidence the occurrence of spectrally defined conformers and report transitions between them, revealed by single molecule spectroscopy.

Single molecule fluorescence spectroscopy of mutants of the Discosoma red fluorescent protein DsRed

We studied the emission of mutants of the red fluorescent protein DsRed by room temperature single molecule fluorescence spectroscopy. Bulk samples of the DsRed variant E8 show mixed green and red fluorescence of equivalent intensities individually spectrally similar to arrested green and mature red fluorescent forms of DsRed. Investigations at the single molecule level indicate that, like DsRed, E8 is not monomeric at single molecule concentrations. The entities visualized are composed of green and red emitting proteins without a fixed ratio of green to red fluorescing units. We find indications for only weak, if any, fluorescence resonance energy transfer (FRET) between red and green chromophores within one E8 entity.