Ultrafast Hydrogen Migration in Photoionized Glycine

Abstract

Hydrogen migration in the glycine cation has been investigated using a combination of a short train of attosecond extreme ultraviolet pulses with few-optical-cycle near-infrared pulses. The yield of the photofragments produced has been measured as a function of pump-probe delay. These time-dependent measurements reveal the presence of a hydrogen migration process occurring in 48 fs. Previous mass spectrometric experiments and theoretical calculations have allowed us to identify the conformations and cation states involved in the process induced by the broad band extreme ultraviolet radiation. TOC:The study of isolated amino-acids in the gas phase allows for complex processes to be probed down to their fundamental molecular properties. Most amino acids present a high degree of conformational flexibility associated with their backbone and side chains, with many local minima in the torsional potential-energy surface. The resulting conformational variety determines the three-dimensional structure of a protein and thus its functionalities. 1

Direct Radiation Effects on the Structure and Stability of Collagen and Other Proteins

“…In particular, little is known about charge transfer and fragmentation dynamics triggered by ionization, but this gap shouldb ef illed by pump-probe experiments at the femto-or attosecond timescales, thanks to free-electron lasers operating in the X-ray energy range. [106] Charge dynamics within amino acids, [107,108] as well as DNA nucleobases and nucleosides, [109] have already recently been measured. Another effect deserving future attention is the fate of ap rotein after al ocalized ionization event.…”

Ultrafast Proton Transfer Dynamics on the Repulsive Potential of the Ethanol Dication: Roaming-Mediated Isomerization versus Coulomb Explosion

“…Recently, it was found for amino acids that the intramolecular PT from the carboxyl (−COOH) group to the amino (−NH 2 ) group will reduce the molecule’s total energy in aqueous solution or in crystals and form a so-called “zwitterion” . As being the lightest element, hydrogen exhibits ultrafast dynamics whether in classical migration , or being subject to nuclear quantum effects. ,− For example, in ionized glycine, the timescale of PT was determined to be less than 50 fs . In a recent work, Richter et al showed that intermolecular PT is fast enough to influence the electronic decay due to the coupling of the electron and nuclear dynamics in water clusters .…”

“Smart Decomposition” of Cyclic Alanine-Alanine Dipeptide by VUV Radiation: A Seed for the Synthesis of Biologically Relevant Species

“…Other potential mechanisms behind the surface-catalyzed reaction imply the formation of a zwitterionic form after proton migration . Ultrafast hydrogen migration has also been observed in ionized gas-phase amino acids, both in isolated molecules − and in a cluster environment. , …”