Selective photodissociation of tailored molecular tags as a tool for quantum optics

Abstract

Recent progress in synthetic chemistry and molecular quantum optics has enabled demonstrations of the quantum mechanical wave–particle duality for complex particles, with masses exceeding 10 kDa. Future experiments with even larger objects will require new optical preparation and manipulation methods that shall profit from the possibility to cleave a well-defined molecular tag from a larger parent molecule. Here we present the design and synthesis of two model compounds as well as evidence for the photoinduced beam depletion in high vacuum in one case.

Neutralization of insulin by photocleavage under high vacuum

“…[12][13][14] Signal depletion of laser desorbed, non-peptidic model compounds was observed after irradiation. 15 Similar observations were made with peptides, launched by ESI where additionally clean cleavage was confirmed. 16 Here we introduce photocleavable tags with charge-decorated leaving groups for peptides and proteins.…”

“…16 In our present work, fluorinated phenols with either a positive tetraalkylammonium (posLG + ) or a negative sulfonate (negLG À ) group are explored as leaving group motifs. 15,16 They are bound to a set of tri-and nonapeptides 1 and 2 (sequences: KAL and KALGALGAL, respectively) shown in Scheme 1, which contain only non-aromatic amino acids to minimize absorption.…”

Tailored photocleavable peptides: fragmentation and neutralization pathways in high vacuum

“…The photocleavage of o -nitrobenzylethers and related nitroaryls in solution is well documented in the literature. 40 , 41 Since cleavage of the 2-phenoxy-methyl-nitrobenzene can already be realized with electrons and atoms of the photolinker, that is without the involvement of solvent molecules, site-specific dissociation should also be possible in the gas phase, 33 as seen in our experiments. To decipher the role of the nitro group, isomers of the tripeptide 1a and the nonapeptide 3a , ( p - 1a , p - 3a ) were synthesized with the nitro-group in the para -position of the benzylic ether function ( Fig.…”

“…Here, we study tailored oligopeptides with a photocleavable tag in an electrospray mass spectrometer, 32 aiming at the controlled charge removal from singly charged anions by photodissociation (PD) at a tailored cleavage point. 33 For that purpose, we have synthesized non-aromatic oligopeptides containing between three and twelve amino acids ( 1–4 ), and a covalently attached photocleavable tag (PCT) with a leaving group that is supposed to split off upon absorption of one or several UV photons ( Scheme 1 and ESI † ). We have synthesized the four different LGs ( a–d ) to investigate their influence on the cleaving efficiency and in all cases the aromatic PCT is designed to be the dominant UV absorber in the tagged peptide.…”

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

“…Our study also shows that future experiments would benefit from cold sources for improved molecule stability and laser ionization detection for improved detection efficiency. Recent progress in ultrafast laser desorption and vacuum ultraviolet photoionization of tryptophan‐rich polypeptides, 22 as well as progress in the neutralization of biomolecular beams prepared by electrospray ionization and photo‐cleavage neutralization, 34,35 are expected to enable research with a wide range of large peptides 23 …”