Ultra-high sensitivity proteomics on the timsTOF SCP

Significance of the topic

The ability to detect and quantify proteins from minute sample amounts, down to single cells, is transforming proteomic research. Enhanced sensitivity in mass spectrometry enables profiling of cellular heterogeneity, biomarker discovery, and insights into low-abundance proteins that remain inaccessible by conventional workflows. The timsTOF SCP platform offers a substantial increase in ion detection efficiency, paving the way for routine ultra-sensitive proteomic analyses.

Objectives and overview of the study

This work evaluates the performance of the newly developed timsTOF SCP mass spectrometer, combined with low-flow liquid chromatography, for analyses of sub-nanogram peptide loads. The aim is to demonstrate robust quantification of protein groups from picogram to nanogram samples, thereby validating a workflow suitable for unbiased single cell proteomics in routine applications.

Methodology

A dilution series of K562 cell digest, spanning 200 pg to 25.6 ng peptide loads, was analyzed using an Evosep One system with the Whisper 40 samples/hour method (28 min gradient at 100 nL/min). Data were acquired in data-independent acquisition mode (dia-PASEF) with a 0.7 s cycle time covering the 400–1000 m/z range. Spectronaut v14 with default hybrid library settings was used for data processing.

Instrumentation used

• Bruker timsTOF SCP mass spectrometer with enhanced ion optic design (additional ion funnel, orthogonal beam turns, widened capillary).
• Evosep One nanoLC system operated in low-flow Whisper 40SPD mode.
• Evotips for sample loading (Promega K562 peptides).
• Spectronaut software version 14 for data analysis.

Main results and discussion

From 200 pg peptide loads, approximately 1200 protein groups were quantified per injection. At 6.4 ng, coverage exceeded 4000 protein groups. Loads of 250 pg and 500 pg—approximating single-cell peptide yields—yielded on average 1542 and 2146 quantified protein groups, respectively. The improvements stem from a 4–5× increase in ion current due to optimized ion optics and enhanced electrospray efficiency at nanoflow rates. These results underscore the capability of the timsTOF SCP workflow to achieve deep proteome coverage from extremely limited material.

Benefits and practical applications of the method

• Routine quantification of thousands of protein groups from sub-nanogram inputs.
• Robust performance enabling high run-to-run reproducibility.
• Compatibility with standard sample preparation workflows, including single cell digest protocols.
• Suitable for studies of cellular heterogeneity, rare cell populations, and low-abundance targets.

Future trends and possibilities for application

Further enhancements may include integration of multiplexed labeling strategies to increase throughput, advanced ion mobility separation schemes for improved peak capacity, and machine-learning-driven data analysis pipelines for deeper proteome coverage. The approach holds promise for clinical proteomics, spatial proteome mapping, and real-time single cell analyses.

Conclusion

The timsTOF SCP platform, when coupled with low-flow Whisper chromatography, provides an ultra-sensitive and robust workflow for proteomic profiling of samples down to single cell levels. This opens new avenues for exploring cellular microheterogeneity and low-abundance proteomes in research and industrial settings.

References

• Li ZY et al. Anal. Chem. (2018).
• Meier F et al. Mol. Cell. Proteomics (2018).
• Yu et al. doi:10.1101/2020.12.22.423933 (2020).
• Yu et al. doi:10.1101/2021.01.25.427969 (2021).