Molecular and supramolecular chirality: R2PI spectroscopy as a tool for the gas‐phase recognition of chiral systems of biological interest

Abstract

Dedicated to Professor Domenico Misiti on the occasion of his 75th birthday. ABSTRACTIn life sciences, diastereomeric chiral molecule/chiral receptor complexes are held together by a different combination of intermolecular forces and are therefore endowed with different stability and reactivity. Determination of these forces, which are normally affected in the condensed phase by solvent and supramolecular interactions, can be accomplished through the generation of diastereomeric complexes in the isolated state and their spectroscopic investigation. This review presents a detailed discussion of the mass resolved Resonant Two Photon Ionization (R2PI-TOF) technique in supersonic beams and introduces an overview of various other technologies currently available for the spectroscopic study of gas phase chiral molecules and supramolecular systems. It reports case studies primarily from our recent work using R2PI-TOF methodology for chiral recognition in clusters containing molecules of biological interest. The measurement of absorption spectra, ionization and fragmentation thresholds of diastereomeric clusters by this technique allow the determination of the nature of the intrinsic interactions, which control their formation and which affect their stability and reactivity.

Multiphoton Ionization and Circular Dichroism: New Experimental Approach and Application to Natural Products

“…High-repetition lasers therefore are particularly useful for CD-LAMS. A further measure is to increase the laser pulse energies in addition to an increase of laser-beam width in such a way that the laser power density (energy per second and cm 2 ) is kept constant. This results in a larger volume of overlap between laser beam and molecular beam and therefore gives rise to larger ion numbers per laser pulse.…”

“…On the other hand, the investigation of electronic properties and conformation of chiral molecules is of fundamental importance for the understanding of these enantio-specific natural processes and the development of methods of asymmetric synthesis, in particular of catalytically enhanced ones. In this context, chiral recognition in the gas phase [1][2][3][4] is of special interest. One very useful tool for analysis as well as for scientific investigation of chiral molecular systems in the condensed or in the gas phase is circular dichroism spectroscopy.…”

Probing chirality recognition of protonated glutamic acid dimers by gas-phase vibrational spectroscopy and first-principles simulations

“…Therefore, sensitive gas-phase experiments are suitable for their detection in isolated tailor-made molecular clusters. 26,29,30 For example, mass spectrometry revealed the extraordinary self-organization of homochiral protonated serine (Ser) tetramers 4 and octamers, [31][32][33] that were hereupon presented as a possible origin for biomolecular homochirality. 34 A recent gasphase vibrational spectroscopy study revealed an asymmetric, yet highly H-bonded structure for the Ser 8 H + magic number cluster.…”

Unraveling non-covalent interactions within flexible biomolecules: from electron density topology to gas phase spectroscopy

“…21,[37][38][39][40] In the same context, a change of chirality of a residue within one peptide chain, or of one of the complexation partners within a complex of chiral molecules, results in a structural change, which is easily evidenced from spectroscopy. 22,[41][42][43][44][45][46][47][48] The nature of the change ranges from subtle differences in dispersion forces between the homochiral and heterochiral complexes 49,50 to a drastic rearrangement of the binding pattern (OHÁ Á ÁO vs. OHÁ Á ÁN interaction, or hydrogen bond vs. dispersion). [51][52][53] In many cases, the difference between two diastereomeric interacting pairs rests on delicate interactions like CHÁ Á Áp or CHÁ Á ÁO interactions, which are much weaker than the main interactions ensuring the stability of the complex.…”