Fig. 1

Nanosecond photochemical reaction (nsPCR). a Nanosecond photochemistry on 2-nitrobenzaldehyde (NBA) creating reactive 2-nitrosobenzoic anion (NS⁻) for the establishment of a localized micro-electric field and the labeling of primary amines in a protein. Tagging one NS⁻ results in a mass shift of 133 Da for proteins of interest. b On-demand three-stage matrix removal regulated by laser ON/OFF switch: Stage 1, laser irradiation establishing micro-electric field thermal gradient; Stage 2, molecular movement driven by localized PME and MST; Stage 3, the charged proteins stay near the center of laser spot while small matrices travel outside—they are thus separated within 3–5 ns and 20–50 μm. Furthermore, the electroneutral biomolecules tend to re-distribute along the thermal gradient upon laser irradiation. Both types of biomolecules can also be cleaned-up by a proton-matrix competition-related potential mechanism. c Schematic illustration of 2-nitrobenzaldehyde (NBA)-based nsPCR for large protein chemical labeling through nanosecond tagging surface accessible amine groups at the N termini and lysine residues