Abstract: A new class of molecular probes is provided for real, efficient, stable, and selective capture of protein-nucleic acid complexes inside cells. The molecular probes have a nucleic acid-binding functional group and a photo-reactive diazirine based functional group, separated by a linker of a selected length or with a multi-arm core, thereby generating a photocrosslink between nucleic acids and proteins in close proximity. This is useful in various chromatin research, including the study of interactions between transcription factors and DNA.

Abstract: A method to induce photo-chemical reactions in a nanoscale space is provided. The method includes fixing cells and incubating the cells with a probe containing a tag for a click reaction. The probe is a psoralen probe that includes an alkyne tag. The method further includes illuminating the cells with UV light on a cell nucleus in a selected region, incubating the cells with a click reaction mix that includes rhodamine-azide, clicking the azide to the psoralen probe through its terminal alkyne, removing excess rhodamine, and viewing the cells with a fluorescence microscope.