The molecular mechanism of ethylenediaminetetraacetic acid (EDTA)-induced membrane destabilization has been studied using a combination of four biophysical techniques on artificial lipid membranes. Data from Langmuir film balance and epifluorescence microscopy revealed the fluidization and expansion effect of EDTA on phase behavior of monolayers of either 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or mixtures of DPPC and metal-chelating lipids, such as N(alpha),N(alpha)-Bis[carboxymethyl]-N(epsilon)-[(dioctadecylamino)succinyl]-L-lysine or 1,2-dioleoyl-sn-glycero-3-[N-(5-amino-1-carboxypentyl iminodiacetic acid) succinyl]. A plausible explanation could be drawn from the electrostatic interaction between negatively charged groups of EDTA and the positively charged choline head group of DPPC. Intercalation of EDTA into the lipid membrane induced membrane curvature as elucidated by atomic force microscopy. Growth in size and shape of the membrane protrusion was found to be time-dependent upon exposure to EDTA. Further loss of material from the lipid membrane surface was monitored in real time using a quartz crystal microbalance. This indicates membrane restabilization by exclusion of the protrusions from the surface. Loss of lipid components facilitates membrane instability, leading to membrane permeabilization and lysis.

In the present study, spectroscopic determinations of copper ions using chimeric metal-binding green fluorescent protein (His6GFP) as an active indicator have been explored. Supplementation of copper ions to the GFP solution led to a remarkable decrease of fluorescent intensity corresponding to metal concentrations. For circumstances, rapid declining of fluorescence up to 60% was detected in the presence of 500 microM copper. This is in contrast to those observed in the case of zinc and calcium ions, in which approximately 10-20% of fluorescence was affected. Recovery of its original fluorescence up to 80% was mediated by the addition of ethylenediamine tetraacetic acid. More importantly, in the presence of metal ions, the emission wavelength maximum remains unchanged while reduction of the optical density of the absorption spectrum has been observed. This indicates that the chromophore's ground state was possibly affected by the static quenching process. Results from circular dichroism measurements revealed that the overall patterns of circular dichroism spectra after exposure to copper ions were not significantly different from that of the control, where the majority of sharp positive band around 195-196 nm in combination with a broad negative deflection around 215-216 nm was obtained. Taken together, it can be presumed that copper ions exerted their static quenching on the fluorescence rather than structural or conformational alteration. However, notification has to be made that some peptide rearrangements may also occur in the presence of metal ions. Further studies were conducted to investigate the feasibility of using the His6GFP as a sensing unit for copper ions. The His6GFP was encapsulated in Sol-gel and immobilized onto the optical fiber connected with a fluorescence detecting device. The Sol-gel was doped into the metal solution where the quenching of fluorescence could be monitored in real time. The sensing unit provided a high sensitivity of detection in the range of 0.5 microM to 50 mM with high selectivity for copper ions. All these findings open up a high potential to apply the fluorescent protein-based bioanalytical tool for copper determination in the future.

The fight against the emergence of mutant influenza strains has led to the screening of an increasing number of compounds for inhibitory activity against influenza neuraminidase. This study explores the chemical space of neuraminidase inhibitors (NAIs), which provides an opportunity to obtain further molecular insights regarding the underlying basis of their bioactivity. In particular, a large set of 347 and 175 NAIs against influenza A and B, respectively, was compiled from the literature. Molecular and quantum chemical descriptors were obtained from low-energy conformational structures geometrically optimized at the PM6 level. The bioactivities of NAIs were classified as active or inactive according to their half maximum inhibitory concentration (IC50) value in which IC50 < 1µM and ≥ 10µM were defined as active and inactive compounds, respectively. Interpretable decision rules were derived from a quantitative structure–activity relationship (QSAR) model established using a set of substructure descriptors via decision tree analysis. Univariate analysis, feature importance analysis from decision tree modeling and molecular scaffold analysis were performed on both data sets for discriminating important structural features amongst active and inactive NAIs. Good predictive performance was achieved as deduced from accuracy and Matthews correlation coefficient values in excess of 81% and 0.58, respectively, for both influenza A and B NAIs. Furthermore, molecular docking was employed to investigate the binding modes and their moiety preferences of active NAIs against both influenza A and B neuraminidases. Moreover, novel NAIs with robust binding fitness towards influenza A and B neuraminidase were generated via combinatorial library enumeration and their binding fitness was on par or better than FDA-approved drugs. The results from this study are anticipated to be beneficial for guiding the rational drug design of novel NAIs for treating influenza infections.

This study compiles a large, non-redundant set of compounds tested for ERα inhibitory activity and applies QSAR modeling for unveiling the privileged substructures governing the activity.