Photophysical properties of fluorescently-labeled peptoids

Abstract

Fluorescently-labeled biomolecules are often utilized in biochemical or cellular experiments without further detailed spectroscopical characterization. This report is intended to narrow this gap and therefore presents the photophysical investigation of a library of 17 fluorescently-labeled molecules, namely peptoid transporters. First, one peptoid structure is labeled with seven different fluorophores and the spectroscopical properties are examined. Absorption and fluorescence maxima are almost identical for free dyes and conjugated dyes, suggesting free choice of a spectrally suitable fluorophore for different applications. Otherwise, extinction coefficients and quantum yields, and therefore the brightness of all seven dyes are strongly influenced. For the fluorophores, e.g. rhodamine B, the extent of this influence depends on the peptoid itself. This is shown by comparing different structures in the second part of this report. Especially the side chain functionalities influence the brightness. And finally, peptoids having two identical fluorescent labels are presented, which show decreased quantum yields. Possible reasons for the observed photophysical properties are discussed.