Enhanced signal intensity in matrix-free laser desorption ionization mass spectrometry by chemical modification of bionanostructures from diatom cell walls.

RATIONALE: Laser desorption ionization for mass spectrometric measurements (LDI MS) is supported by nanostructured materials. This technique helps to overcome known limitations of matrix-assisted laser desorption/ionization (MALDI) and especially avoids interfering signals caused by matrix components. LDI can be supported by bionanostructures from the cell walls of diatoms. We explore how ionization efficiency can be improved by chemical modification of the cell walls. METHODS: We introduce procedures to chemically modify these nanopatterned silicate structures using perfluorooctyldimethylchlorosilane or pentafluorophenylpropyldimethylchlorosilane. Using a conventional MALDI-MS instrument we compare ionization using the novel materials with that of unmodified cell walls. The functionalized bionanomaterial is comprehensively evaluated for the use in LDI MS using a broad range of analytes and two commercial drugs. RESULTS: Chemical modifications lead to materials that support LDI significantly better than unmodified diatom cell walls. LDI signal intensity was up to 25-fold increased using the modified preparations. No interfering signals in the lower molecular weight range down to m/z 100 were observed, demonstrating the suitability of the method for small analytes. Crude solutions of commercial drugs, such as Aspirin complex(®) and IbuHEXAL(®) could be directly investigated without additional sample preparation. CONCLUSIONS: Chemically modified diatom cell walls represent a powerful tool to support ionization in LDI MS. The lack of background signals in the low molecular weight region of the mass spectra allows also the investigations of small analytes.

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection.

Molecular probes are widely used tools in chemical biology that allow tracing of bioactive metabolites and selective labeling of proteins and other biomacromolecules. A common structural motif for such probes consists of a reporter that can be attached by copper(I)-catalyzed 1,2,3-triazole formation between terminal alkynes and azides to a reactive headgroup. Here we introduce the synthesis and application of the new thiazole-based, azide-tagged reporter 4-(3-azidopropoxy)-5-(4-bromophenyl)-2-(pyridin-2-yl)thiazole for fluorescence, UV and mass spectrometry (MS) detection. This small fluorescent reporter bears a bromine functionalization facilitating the automated data mining of electrospray ionization MS runs by monitoring for its characteristic isotope signature. We demonstrate the universal utility of the reporter for the detection of an alkyne-modified small molecule by LC-MS and for the visualization of a model protein by in-gel fluorescence. The novel probe advantageously compares with commercially available azide-modified fluorophores and a brominated one. The ease of synthesis, small size, stability, and the universal detection possibilities make it an ideal reporter for activity-based protein profiling and functional metabolic profiling.

Caulerpenyne and related bis-enol esters are novel-type inhibitors of human 5-lipoxygenase.

Caulerpenyne (CYN) is a sesquiterpene from green algae with known inhibitory properties against soybean lipoxygenase. Here we introduce a detailed structure-activity study elucidating the inhibitory effects of CYN and a library of six synthetic CYN analogues on isolated human 5-lipoxygenase (5-LO) and cellular 5-LO in polymorphonuclear leukocytes. Essential structural elements are identified and a structurally simplified inhibitor is introduced. The modes of 5-LO inhibition by CYN and the synthetic inhibitors cannot be assigned to any of the known categories of lipoxygenase inhibitors. These compounds clearly interfere directly with 5-LO and represent rather small and flexible molecules, with unique structures among 5-LO inhibitors identified thus far.