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Nanomechanical biosensors based on atomic force microscopy (AFM) cantilevers have garnered considerable attention. AFM cantilevers are devices that can detect a target either via a surface functionalization process based on immobilization through molecular adsorption, or through the selective chemical binding of a speci¯c molecule, transforming the device into a speci¯c biosensor. In this study, we demonstrate that functionalized AFM cantilevers could be used, in a process involving self-assembling layers, to create a homogeneous surface layer of the widely used herbicide mesotrione. Controlled experiments to evaluate its detection were performed, and binding between mesotrione and its target molecule, 4-hydroxyphenylpyruvate dioxygenase (HPPD), was evaluated using de°ection curves of functionalized cantilevers interacting with mesotrione. The cantilevers worked as nanomechanical sensors inside a°uid cell device, under di®erent ¶ Corresponding author. 1750079-1NANO: Brief Reports and Reviews Vol. 12, No. 7 (2017) concentrations of HPPD diluted in PBS. After evaluating increasing concentrations of HPPD, the de°ection curves showed a clear, dose-dependent pattern. The homogeneous dispersion of mesotrione on the cantilevers was assessed by confocal microscopy, and this corroborated the functionalization method. Thus, the results obtained by this functionalized cantilever presented a high e±ciency in detecting binding between HPPD and mesotrione molecules at concentrations as low as 17 ng mL À1 . In this way, as a preliminary step for a future environmental contaminants nanosensor development, the described detection method showed a suitable capability for molecular recognition at the nanoscale.

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A precise diagnosis for neuromyelitis optica spectrum disorders (NMOSD) is crucial to improve patients’ prognostic, which requires highly specific and sensitive tests. The cell-based assay with a sensitivity of 76% and specificity of 100% is the most recommended test to detect anti-aquaporin-4 antibodies (AQP4-Ab). Here, we tested four AQP4 external loop peptides (AQP461–70, AQP4131–140, AQP4141–150, and AQP4201–210) with an atomic force microscopy nanoimmunosensor to develop a diagnostic assay. We obtained the highest reactivity with AQP461–70-nanoimunosensor. This assay was effective in detecting AQP4-Ab in sera of NMOSD patients with 100% specificity (95% CI 63.06–100), determined by the cut-off adhesion force value of 241.3 pN. NMOSD patients were successfully discriminated from a set of healthy volunteers, patients with multiple sclerosis, and AQP4-Ab-negative patients. AQP461–70 sensitivity was 81.25% (95% CI 56.50–99.43), slightly higher than with the CBA method. The results with the AQP461–70-nanoimmunosensor indicate that the differences between NMOSD seropositive and seronegative phenotypes are related to disease-specific epitopes. The absence of AQP4-Ab in sera of NMOSD AQP4-Ab-negative patients may be interpreted by assuming the existence of another potential AQP4 peptide sequence or non-AQP4 antigens as the antibody target.

A combined molecular modeling and molecular dynamics simulation was carried out to obtain an improved description of the yeast acetohydroxyacid synthase (AHAS) in aqueous solution. After a thorough homology modeling, the AHAS catalytic dimer was subjected to a molecular dynamics (MD) simulation to analyze its behavior and optimize its geometry. The AHAS 3D molecular structure was analyzed according to the number of salt bridges and hydrogen bonds formed. During 20 ns of MD simulation, an average fluctuation of 3.9 Å was obtained. The cofactor thiamine diphosphate makes a relevant contribution to the system stability; this hypothesis was confirmed by the decrease in the average fluctuation of 0.3 Å. Moreover, the Ramachandran plot revealed no denaturation framework during the time of the simulation. ]]>

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