Matter–wave interference and deflection of tripeptides decorated with fluorinated alkyl chains

Abstract

Studies of neutral biomolecules in the gas phase allow for the study of molecular properties in the absence of solvent and charge effects, thus complementing spectroscopic and analytical methods in solution or in ion traps. Some properties, such as the static electronic susceptibility, are best accessed in experiments that act on the motion of the neutral molecules in an electric field. Here, we screen seven peptides for their thermal stability and electron impact ionizability. We identify two tripeptides

Otto Stern’s Legacy in Quantum Optics: Matter Waves and Deflectometry

“…The feasibility of thermal peptide beams was studied using derivatives of a tryptophan-containing tripeptide. While an unprotected alanine-tryptophan-alanine (Ala-Trp-Ala) showed only fragments in the VUV-post-ionization mass spectrum (λ = 157 nm), the intact molecular ion could be observed after removing internal charges and hydrogen bond donors by acetylation and amidation of the termini and methylation of the peptidic amide protons [92,93]. The introduction of fluoroalkyl chains at the N-terminus or both termini improved the relative intensity of the molecular ion substantially despite the increase in molecular mass.…”

“…Large, electronrich π -systems are also attractive for photo-induced post-ionization [87]. Oligopeptides with tryptophan units turned out to be particularly suited for photoionization mass spectrometry because of the high absorption cross section of the indole subunit, the only group in any natural amino acid that is susceptible to single-photon ionization at 157 nm [66,93]. A high tryptophan density even permitted the VUV-ionization of a peptidic construct of more than 20 kDa, thereby exceeding the mass limit for VUVionization by one order of magnitude over the previous standard for biomolecules [65].…”

“…Thermal beams of functionalized tripeptides: Peptides are very fragile compounds-even simple dipeptides hardly survive the temperature needed to build up the vapor pressure required for molecular beam experiments. Interestingly, perfluoroalkly functionalization can facilitate the formation of thermal beams of even tripeptides [97] to a degree that matter wave interference became possible [93] (see Fig. 6e).…”

“…6 Interference-assisted deflectometry was used to elucidate the dynamic dipole moments of functionalized azobenzenes [88], b the fragmentation of a palladium catalyst precursor [105], c electron delocalization in constitutional isomers [91], and d permanent electric dipole moments in porpyhrin derivatives [104]. e Tripeptides optimized for both molecular beam formation and detection [93]. f Molecular libraries of members with well-defined molecular weight by random substitution of fluorine atoms with highly fluorinated alkyl chains [89] Permanent dipole moment: Molecules with a permanent electric dipole moment experience a shift of their fringe pattern that depends upon the orientation of the molecule.…”

Chirality: The Backbone of Chemistry as a Natural Science

“…Atoms and molecules correspond to the frontier, or boundary, of chemistry at its lower level of complexity, that is, to the emergence of the classical from the quantum physics world. This lower frontier of chemistry is well understood by physicists and chemical physicists [10,11] but is generally ignored by chemists. (ii) Application of the constraints originated by the thermodynamic principles and the description of the behaviour of chemical substances and materials as very large sets of atoms and molecules, i.e., of real chemical samples.…”