Direct analysis of in-gel proteins by carbon nanotubes-modified paper spray ambient mass spectrometry

Abstract

The in situ and direct extraction, desorption and ionization of in-gel intact proteins after electrophoresis has been achieved by carbon nanotubes (CNTs)-modified paper spray mass spectrometry at ambient conditions. Characteristics of CNTs (including larger surface area, smaller pore diameter and enhanced conductivity) were endowed to the porous filter paper substrate by uniformly dispersing the CNTs on the filter paper. Upon applying electric potential to the CNTs-modified paper, the in-gel proteins were extracted from the gel and subsequently migrated to the tip of the filter paper by electrophoresis-like behavior for paper spray ionization, which was monitored by extracted ion chronograms. The characterizations of modified filter papers and CNTs nanoparticles further confirmed the role of CNTs in in-gel protein extraction, protein migration as well as spray ionization at the paper tip. Under optimized conditions, a mixture of cytochrome c, lysozyme and myoglobin was successfully separated by native electrophoresis and subsequently analysed by the present method, showing a limit of detection of 10 ng per gel band. The present strategy offers a new pathway for the direct detection of in-gel intact proteins at ambient conditions without any pre-treatment (e.g. digestion, chemical extraction and desalting), which exhibits potential applications in top-down proteomics.

Analysis of Biofluids by Paper Spray MS: Advances and Challenges

“…The nanoscale features at the CNT paper surface were confirmed to be responsible for the high electric fields at paper tip. CNTs-modified paper has also been used for the intact proteins after separation on a polyacrylamide gel [29].…”

“…Cytochrome C, lysozyme and myoglobin were analyzed directly from polyacrylamide gel utilizing paper modified with carbon nanotubes [29]. Non-covalent protein complexes were detected using paper spray and ion mobility MS/MS [30].…”

Facile preparation of paper substrates coated with different materials and their applications in paper spray mass spectrometry

“…But the efficiency of the subsequent analysis shows a very weak signal resulting from sides of commercially available filter paper with blood spots containing 1000 mg mL À1 methylene blue. To reduce this interaction, CNT modied paper was used for direct analysis of in-gel intact proteins by Han et al 15 Herein in addition to binding irregular silica particles on a paper surface as above, the present introduced vacuum ltration method shows the capacities for coating other commercially available well-dened materials such as silica based materials, metal oxides and polymers (Fig. 3 (a) Tandem mass spectrum of 1.0 mg mL À1 verapamil in the dried blood spot and (b) effect of silica coated amount on the ionization efficiency of paper spray.…”

Paper cone spray ionization mass spectrometry (PCSI MS) for simple and rapid analysis of raw solid samples

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We developed a modified paper spray ionization (PSI) platform, named as paper cone spray ionization (PCSI), for direct mass spectrometric analysis of raw solid samples. 13 PSI MS has been employed in various applications. This three-dimensional paper cone serves as a sample container, an in situ solid-liquid extraction chamber, an analyte transport channel, as well as an electrospray tip.

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