Single-cell proteomics: what is realistic today

Where the field is

Mass-spectrometry single-cell proteomics quantifies, in favourable systems, on the order of one to a few thousand protein groups from a single mammalian cell, using ultra-low-flow chromatography and the most sensitive current analysers (Brunner et al., Mol Syst Biol 2022). Depth depends strongly on cell size and type: a large cultured cell yields far more than a small primary lymphocyte.

What determines success

• Sample preparation in nanolitre volumes. Losses to surfaces dominate at this scale. Dedicated low-binding consumables and minimal transfer steps matter more than any instrument setting.
• Cell isolation and quality. FACS or dispensing with imaging confirmation; dead or doublet cells ruin a run that costs an hour of instrument time.
• Chromatography. Very low flow rates and short, high-efficiency gradients; the column is as important as the mass spectrometer.
• Acquisition. DIA on high-sensitivity analysers (Astral-class or Tribrid) is the current standard for label-free single cells; multiplexed carrier approaches trade some accuracy for throughput.
• Statistics. Hundreds of cells are needed for population-level conclusions; missing values are structural and must be modelled, not imputed away.

Depth has continued to improve: narrow-window DIA on the Orbitrap Astral analyser reports several thousand protein groups from low-nanogram inputs in short gradients (Guzman et al., Nat Biotechnol 2024). Equally important for anyone publishing single-cell data are the community recommendations for performing, benchmarking and reporting such experiments (Gatto et al., Nat Methods 2023), which set out what controls and metadata a reviewer will expect.

Questions it answers well, and badly

Heterogeneity within a population, rare-cell states, and trajectories in differentiation or treatment response are well suited. Absolute quantification of low-copy signalling proteins, deep PTM analysis and small differences between similar cells are not yet. A bulk proteome of sorted sub-populations often answers the biological question at a fraction of the cost and should be considered first.

If a single-cell study is the right tool, the practical route is a pilot of a few dozen cells to measure depth and reproducibility on your cell type before scaling. Low-input desalting formats such as single-cell grade SPE tips and acquisition on the Ascend or Astral platforms are how we approach it.

References

1. Brunner AD et al. Ultra-high sensitivity mass spectrometry quantifies single-cell proteome changes upon perturbation. Mol Syst Biol 2022;18:e10798. Open access PubMed · DOI · Full text (PMC)
2. Guzman et al. Ultra-fast label-free quantification and comprehensive proteome coverage with narrow-window data-independent acquisition. Nat Biotechnol 2024. Open access PubMed · DOI · Full text (PMC)
3. Gatto et al. Initial recommendations for performing, benchmarking and reporting single-cell proteomics experiments. Nat Methods 2023. Open access PubMed · DOI · Full text (PMC)

Citations verified against PubMed records; “Open access” marks papers whose full text is freely available via PubMed Central or the journal.

Written by the omicslink proteomics team. Reviewed November 2026.