An arrayed host:guest fluorescence sensor system can
discriminate
DNA G-quadruplex structures that differ only in the presence of single
oxidation or methylation modification in the guanine base. These small
modifications make subtle changes to G4 folding that are often not
detectable by CD but induce differential fluorescence responses in
the array. The sensing is functional in diluted serum and is capable
of distinguishing individual modifications in DNA mixtures, providing
a powerful method of detecting folding changes caused by DNA damage.
Flexible, water-soluble hosts are capable of selective molecular recognition in cellular environments and can detect neurotransmitters such as choline in cells. Both cationic and anionic water-soluble self-folded deep cavitands can recognize suitable styrylpyridinium dyes in cellular interiors. The dyes selectively accumulate in nucleotide-rich regions of the cell nucleus and cytoplasm. The hosts bind the dyes and promote their relocation to the outer cell membrane: the lipophilic cavitands predominantly reside in membrane environments but are still capable of binding suitable targets in other cellular organelles. Incubating the cells with structurally similar biomarkers such as choline, cholamine, betaine, or butyrylcholine illustrates the selective recognition. Choline and butyrylcholine can be bound by the hosts, but minimal binding is seen with betaine or cholamine. Varying the dye allows control of the optical detection method, and both "turn-on" sensing and "turn-off" sensing are possible.
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