Investigating the effect of membrane anchoring on photoinduced electron transfer pyrazoline based fluorescent probes
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Fluorescence microscopy is a powerful analytical tool for visualizing biological processes at the subcellular level. In this regard, 1,3,5-triarylpyrazoline based fluorescent probes which act as "turn-on" probes, have been extensively researched. These probes achieve their fluorescence "turn-on" response by inhibition of fluorescence quenching by acceptor-excited photoinduced electron transfer upon binding of an analyte. It has been recently shown that some fluorescent probes used in biological research form colloids composed of nanoparticles, due to their hydrophobic character. This hydrophobic character can also lead to partitioning of the probe into cellular membranes. Colloid formation and membrane partitioning may affect the probes' photophysical properties such as absorption and emission wavelength and quantum yields. Recently, a series of 1,3,5-triarylpyrazolines synthesized in our group by M. T. Morgan, showed no formation of aggregates in aqueous buffer. Surprisingly, these probes increased their fluorescence intensity in the presence of liposomes. The photoinduced electron transfer process is greatly affected by the polarity of the medium in which the probe is used. In this study, the effect of membrane proximity on the photoinduced electron transfer process for pyrazoline based "turn-on" probes has been investigated. A series of water soluble 1,3,5-triarylpyrazolines have been synthesized in which a N,N-dialkylaniline moiety acts as an electron donor and a proton acceptor and an alkylated sulfonamide moiety acts as a molecular anchor for interaction with neutral and anionic liposomes.