Identifying apoptotic cells with the 3-hydroxyflavone derivative F2N12S, a ratiometric fluorescent small molecule probe selective for plasma membranes: a possible general mechanism for selective uptake into apoptotic cells.

The mechanism of selective targeting of the plasma membrane of apoptotic cells by F2N12S, a recently reported ratiometric, fluorescent small molecule probe, was analyzed using decision-rule QSAR models. Selectivity was determined by a combination of the probe's weak amphiphilicity and slow flip-flop with the increased plasma membrane fluidity of apoptotic cells. The probable chemical features required for such probes may be defined in terms of numerical structural parameters as: 3.5 < AI < ∼ 5.5; log P < 5.0; HGS > 400 (where AI, log P and HGS parameters model amphiphilicity, lipophilicity and headgroup size, respectively). When HGS is <400, compounds are initially membrane selective, but subsequently are internalized.