-Photo-leucine acquires its function after being exposed to UV light. This causes diazirine ring of -photo-leucine to lose its nitrogen atoms in form of nitrogen gas, leaving its carbon atom as a reactive free radical. The bonds established between this carbon, belonging to one protein (A), and atoms belonging to another protein (B) are responsible for the cross-linking properties of -photo-leucine, which allow it to attach these two peptide chains into a single complex (AB).
The appropriate wavelength to activate the -photo-leucine molecule ranges from 320 to 370 nanometers. Lamps with higher power are more effective in accomplishing this objective and do so in less time. The ideal wavelength for the activation of the photo-leucine amino acid is of 345 nm.
To increase efficiency, a shallow and uncovered plate must be used. Also, rotation of the samples located under the UV right may be necessary to make sure they receive even UV irradiation, and thus to, yet again, improve the cross-linking efficiency. If the cross-linking is done in vivo, within living cells, these must be exposed to the UV radiation during a period of 15 minutes or less.