Photoactivated Biosensing Process for Dictated ATP Detection in Single Living Cells.

The subcellular distribution of adenosine 5'-triphosphate (ATP) and the concentration of ATP in living cells dynamically fluctuate with time during different cell cycles. The dictated activation of the biosensing process in living cells enables the spatiotemporal target detection in single living cells. Herein, a kind of o-nitrobenzylphosphate ester hairpin nucleic acid was introduced as a photoresponsive DNA probe for light-activated ATP detection in single living cells. Two methods to spatiotemporally activate the probe in single living cells were discussed. One method was the usage of the micrometer-sized optical fiber (about 5 µm) to guide the UV light (λ = 365 nm) to selectively activate the photoresponsive DNA probe in single living cells. The second method involved a two-photon laser confocal scanning microscope to selectively irradiate the photoresponsive DNA probes confined in single living cells via two-photon irradiation (λ = 740 nm). ATP aptamer integrated in the activated DNA probes selectively interacted with the target ATP, resulting in dictated signal generation. Furthermore, the photoactivated biosensing process enables dictated dual-model ATP detection in single living cells with "Signal-ON" fluorescence signal and "Signal-OFF" electrochemical signal outputs. The developed photoactivated biosensor for dictated ATP detection with high spatiotemporal resolution in single living cells at a desired time and desired place suggests the possibility to monitor biomarkers during different cell cycles.

Effects of the hydroxyl group on phenyl based ligand/ERRγ protein binding.

Bisphenol-A (4,4'-dihydroxy-2,2-diphenylpropane, BPA, or BPA-A) and its derivatives, when exposed to humans, may affect functions of multiple organs by specific binding to the human estrogen-related receptor γ (ERRγ). We carried out atomistic molecular dynamics (MD) simulations of three ligand compounds including BPA-A, 4-α-cumylphenol (BPA-C), and 2,2-diphenylpropane (BPA-D) binding to the ligand binding domain (LBD) of a human ERRγ to study the structures and energies associated with the binding. We used the implicit Molecular Mechanics/Poisson-Boltzmann Surface Area (MM/PBSA) method to estimate the free energies of binding for the phenyl based compound/ERRγ systems. The addition of hydroxyl groups to the aromatic ring had only a minor effect on binding structures and a significant effect on ligand/protein binding energy in an aqueous solution. Free binding energies of BPA-D to the ERRγ were found to be considerably less than those of BPA-A and BPA-C to the ERRγ. These results are well correlated with those from experiments where no binding affinities were determined in the BPA-D/ERRγ complex. No conformational change was observed for the helix 12 (H-12) of ERRγ upon binding of these compounds preserving an active transcriptional conformation state.