Reverse docking results.

The graphical output provided by IdTarget.</p

Aromatic molecules subclasses.

Aromatic molecules subclasses.</p

Results of direct docking simulation experiments.

Results of direct docking simulation experiments.</p

Direct docking simulation experiment results.

(A) The drawing shows the conformation number 97, at the top right the position of benzene in the binding site of 1GT1 structure; at bottom (left) a particular binding site highlights the residues involved in the interaction with benzene. (B) The drawing shows the conformation number 91, at top (right) the position of benzene in the binding site of 1DZK structure; at bottom (left), a particular binding site highlights the residues involved in the interaction with benzene.</p

Biphenyl competitive assay.

Figure shows the competitive assay. The competitive molecule used was biphenyl; fluorescence signal at 481 nm was unaffected.</p

The porcine odorant-binding protein as molecular probe for benzene detection

In recent years, air pollution has been a subject of great scientific and public interests for the strong impact on human health. Air pollution is due to the presence in the atmosphere of polluting substances, such as carbon monoxide, sulfur and nitrogen oxides, particulates and volatile organic compounds (VOCs), derived predominantly from various combustion processes. Benzene is a VOC belonging to group-I carcinogens with a toxicity widely demonstrated. The emission limit values and the daily exposure time to benzene (TLV-TWA) are 5μg/m3 (0.00157 ppm) and 1.6mg/m3 (0.5 ppm), respectively. Currently, expensive and time-consuming analytical methods are used for detection of benzene. These methods require to perform a few preliminary steps such as sampling, and matrices pre-treatments. In addition, it is also needed the support of specialized personnel. Recently, single-walled carbon nanotube (SWNTs) gas sensors with a limit detection (LOD) of 20 ppm were developed for benzene detection. Other innovative bioassay, called bio-report systems, were proposed. They use a whole cell (Pseudomona putida or Escherichia coli) as molecular recognition element and exhibit a LOD of about 10 μM. Here, we report on the design of a highly sensitive fluorescence assay for monitoring atmospheric level of benzene. For this purpose, we used as molecular recognition element the porcine odorant-binding protein (pOBP). 1-Aminoanthracene was selected as extrinsic fluorescence probe for designing a competitive fluorescence resonance energy transfer (FRET) assay for benzene detection. The detection limit of our assay was 3.9μg/m3, a value lower than the actual emission limit value of benzene as regulated by European law.</div

Benzene titration curve fitting.

Plot of the intensity decrease of 1-AMA fluorescence emission at 481 nm as a function of benzene concentration. In red color it is shown the fitting curve obtained by a non-linear function.</p

1-AMA titration curve fitting.

Plot of the intensity increase of 1-AMA fluorescence intensity as a function of fluorophore concentrations.</p

Fluorescence emission spectra at increasing concentrations of benzene.

Figure shows the emission fluorescence spectra of pOBP in the presence of saturating concentrations of 1-AMA. The addition of increasing amounts of benzene determines a decrease of the peak at 481 nm and an increase of the peak at 340 nm.</p

Benzene effect on pOBP structure.

Near-UV CD spectra of pOBP collected at different concentrations of benzene (0–10 μM).</p