Permeability of Lipid Membranes for Atomic Tritium or Atom “Slipping” Effect and Its Role in Tritium Planigraphy

The depth of penetration of tritium atoms capable of isotope substitution, generated by thermal dissociation on a tungsten wire (thermal activation of tritium), into a solid target is considered. On the basis of calculations used in the theory of recoil atom stopping, with a lipid bilayer as example, the possibility of penetration of reactive atoms to a depth of up to 5 nm was demonstrated. This result is nicely consistent with the available experimental data. The possibility of “slipping” of atomic tritium, without loss of its reactivity, into cavities with a decreased electron density was suggested. This phenomenon should be taken into account when interpreting the results of studying biological macromolecules and their complexes by tritium planigraphy.