pH-dependent optical transitions in anionic pentameric oligothiophenes
2014 (English)Manuscript (preprint) (Other academic)
Understanding the photo-physical processes in fluorescent probes are essential as such dyes are widely utilized in molecular biology. Here we report the pH-dependent optical transitions of a library of anionic pentameric luminescent conjugated oligothiophenes (LCOs) that have been used for fluorescent identification of protein aggregates, the pathological hallmark of many devastating diseases. Absorption-, excitation- and emission spectra were recorded for all LCOs in different buffers with a pH range from 3.5 to 7. p-FTAA, a LCO having a central core consisting of a trimeric thiophene building block with head-to-head acetic acid functionalization as well as terminal carboxyl groups extending the pentameric thiophene backbone, displayed pH/dependent optical characteristics correlating to a non-planar to planar transition of the conjugated backbone as well as aggregation between adjacent thiophene chain upon protonation of the acetic acid side chains. In contrast, chemically related analogues to p-FTAA lacking the terminal carboxyl groups extending the pentameric thiophene backbone or the conformational ability to undergo a non/planar to planar transition of the conjugated backbone, displayed different optical characteristics compared to p-FTAA. Overall these studies highlighted that minor chemical alteration of LCOs can result in major difference in the optical characteristics obtained from the dyes and the results might aid in designing novel LCOs that have superior optical performance as amyloid ligands.
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IdentifiersURN: urn:nbn:se:liu:diva-111656OAI: oai:DiVA.org:liu-111656DiVA: diva2:758686