Proton transfer in histidine-tryptophan heterodimers embedded in helium droplets

TL;DR

This study investigates proton transfer mechanisms in histidine-tryptophan heterodimers embedded in helium droplets, revealing hydrogen-bonded interactions and proton transfer in a radical cationic environment using nano-scale helium reactors.

Contribution

It demonstrates the formation and ionization of amino acid heterodimers in helium droplets and uncovers proton transfer dynamics within these complexes.

Findings

Proton transfer occurs from tryptophan to histidine in radical cations.

Hydrogen bonds facilitate proton transfer in amino acid heterodimers.

Helium droplets serve as effective nano-reactors for studying molecular interactions.

Abstract

We used cold helium droplets as nano-scale reactors to form and ionize, by electron bombardment and charge transfer, aromatic amino acid heterodimers of histidine with tryptophan, methyl-tryptophan, and indole. The molecular interaction occurring through an N-H...N hydrogen bond leads to a proton transfer from the indole group of tryptophan to the imidazole group of histidine in a radical cationic environment.