FemtoSecD: Femtosecond Desorption of Large Polypeptides

Large neutral polypeptides, as required for quantum interference experiments, pose grand challenges to modern molecular beam research. Because of their high mass, we need to deposit high energy very locally. Because of their many peptide bonds, the risk of fragmentation is very high.

While established experiments in mass spectrometry and matrix assisted laser desorption (ionization) are routinely working with laser intensities of the order of 106-107 W/cm2 we find that we can softly transfer isolated large peptides into the gas phase by using 1012 W/cm2 of laser intensity. The big molecules are than carried away by a cold carrier gas.

In collaboration with our colleagues around Marcel Mayor and Valentin Köhler at the University of Basel, we are exploring the mass and complexity limit of desorpbing neutral polypeptides and proteins in high vacuum. The verification of intact volatilization is based on VUV postionization and other means mass spectrometry.

We find that efficient ionization is still possible for peptides as massive as 20 kDa, if they contain a very high content of tryptophan molecules.

References: 

• J. Schätti, P. Rieser, U. Sezer, G. Richter, P. Geyer, G.G. Rondina, D. Häussinger, M. Mayor, A. Shayeghi, V. Köhler, M. Arndt,
  Pushing the mass limit for intact launch and photoionization of large neutral biopolymers, Communications Chemistry, 1, 93 (2018).