The active ingredient of 'Lovozal' (fenazaflor) is hydrolysed in solution to 5,6-dichloro-2-trifluoromethylbenzimidazole (DTFB). Rat liver mitochondria were uncoupled by fenazaflor after a lag phase, while uncoupling by DTFB was immediate, and a similar situation occurred with mitochondria isolated from Tetranychus telarius L. (This is the first report of isolation of mite mitochondria.) Since both compounds ultimately have the same uncoupling activity, it is likely that fenazaflor exerts its effect only after hydrolysis to DTFB. Living mites showed a stimulation of respiration of 70% on addition of either fenazaflor or DTFB before death occurred, suggesting that the acaricidal effect of fenazaflor is due to uncoupling of oxidative phosphorylation after hydrolysis to DTFB.

Top-down mass spectrometry (MS) has emerged as a powerful complement to peptide-based proteomics. Despite advancements, the field has had limited application to clinical proteomics investigations due to the complexity and poor dynamic range of chromatography used to separate intact proteins from tissue and biofluids. To address these limitations, we developed a two-dimensional (2D) chromatography platform that includes isoelectric focusing (IEF) through immobilized pH gradient and superficially porous liquid chromatography (SPLC). Analysis of standard proteins demonstrates compatibility of IEF-SPLC processing and high resolving-power MS analysis with results showing ~7.0 femtomole detection limits and linear spectral response for proteins fractionated over ~4 log sample loads. For proteins from heart myofibrils and cerebrospinal fluid (CSF), compared to one-dimensional SPLC-MS, the 2D IEF-SPLC-MS platform resulted in a 5-6× increase in the number of unique monoisotopic masses observed <30 kDa and an ~4× improved mass range enabling the observation of proteins >200 kDa. In the heart myofibrils, common protein proteoforms observed were associated with phosphorylation of contractile proteins with results showing that quantitative evaluation of their PTM stoichiometry was possible despite differentially modified forms being fractionated into separate pI compartments. In CSF, diverse protein mutations and PTM classes were also observed, including differentially glycosylated protein forms separated to different pI. Results also demonstrate that by the generation of IEF-SPLC protein libraries by fraction collection, the platform enables prospective protein identification and proteoform analysis investigations by complementary top-down and bottom-up strategies. Overall, the 2D platform presented may provide the speed, dynamic range, and detection limits necessary for routine characterization of proteoform-based biomarkers from biofluids and tissues.

Coupling immunoassays on self-assembled monolayers (SAMs) to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) provides improved assay selectivity compared with traditional photometric detection techniques. We show that thinlayer-transfer (TLT) of α-cyano-4-hydroxycinnaminic acid (CHCA) MALDI matrix via vacuum sublimation followed by organic solvent-based vapor-sorption induced co-crystallization (VIC) results in unique matrix/analyte co-crystallization tendencies that optimizes assay reproducibility and sensitivity. Unique matrix crystal morphologies resulted from VIC solvent vapors, indicating nucleation and crystal growth characteristics depend upon VIC parameters. We observed that CHCA microcrystals generated by methanol VIC resulted in 910× better sensitivity, increased analyte charging, and improved precision compared with dried droplet measurements. The uniformity of matrix/analyte co-crystallization across planar immunoassays directed at intact proteins yielded low spectral variation for single shot replicates (18.5 % relative standard deviation, RSD) and signal averaged spectra (G10 % RSD). We envision that TLT and VIC for MALDI-TOF will enable high-throughput, reproducible array-based immunoassays for protein molecular diagnostic assays in diverse biochemical and clinical applications.

Immunoassays are widely used in biochemical/clinical laboratories owing to their simplicity, speed, and sensitivity. We combined self-assembled monolayer-based immunoassays with MALDI-TOF MS to show that high-fidelity surface preparations with a novel matrix deposition/crystallization technique permits quantitative analysis of monolayer-bound antigens at picomolar detection limits. Calibration curves for intact proteins are possible over a broad concentration range and improved specificity of MS-immunoassays is highlighted by simultaneous label-free quantitation of ligand-bound protein complexes.

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