The publication of a review on the foundations of a new scientific discipline that pursues to control the movement of electrons in molecules using attosecond methodologies (see Chem. Rev., 2017, 117 (16), pp 10760–10825, DOI: 10.1021/acs.chemrev.6b00453), has appeared, among others, in the following media:
Several european researchers have been able to induce and observe the ultrafast motion of electrons in a biomolecule (the aminoacid phenylalanine) on an attosecond timescale.
Charge migration in molecules precedes structural rearrangements which are the basis of many biological processes. According to the results presented, charge migration from one end of the phenylalanine molecule to the other takes around 3-4 femtoseconds (one femtosecond = 1.000 attoseconds). This is the fastest process ever observed in a biological structure.
The numerical simulations carried out allowed those researchers to identify, unambiguously, that this fast charge migration is solely due to the electronic motion of the electrons induced by the attosecond pulse, rather than to structural changes. The ability to provoke and observe purely electronic dynamics in biomolecules is crucial for future applications in attosecond science. This charge migration may, as an example, initiate a chemical reaction.
The work, published in Science on October 17th, results from a theoretical/experimental collaboration among researchers involved in the ERC funded projects XCHEM (Universidad Autónoma de Madrid) and ELYCHE (Politecnico di Milano), and from the Ultrafast group at Queen’s University of Belfast, the Theoretical Chemistry group at the Università di Trieste and the Attosecond Physics Group at the Institute of Photonics and Nanotechnologies IFN-CNR of Milano and Padova.
Several european researchers have been able to induce and measure an ultrafast charge migration in a complex molecule. This phenomenon precede any structural rearrangement of molecules and is the basis of many biological processes. The work has been published in the journal Science.
Figure: Snapshots of charge distribution on the most abundant conformer of the aminoacid phenylalanine. The charge density can take negative and positive values (yellow) or (purple). The charge migration from one end of the molecule to the other takes no more than three or four femtoseconds.
The work arises from a cooperation among several European researchers (among them the PI’s of two ERC AdG projects, ELYCHE project, with GA nº 227355 and XCHEM project, with GA nº 290853). A clear experimental evidence of ultrafast charge dynamics in the phenylalanine amino acid, after prompt ionization induced by attosecond pulses, has been found. Charge migration shows up as oscillations in the yield of a doubly-charged molecular fragment produced from ionization of a second electron by a probe pulse as a function of its delay time. Two main frequencies were measured: 0.24 PHz (corresponding to a period of 4.2 fs) and 0.36 PHz (period of 2.8 fs), thus confirming the electronic origin of the measured dynamics. Numerical simulations of the temporal evolution of the electronic wave packet created by the attosecond pulse strongly support the interpretation of the experimental data in terms of charge migration.
The ability to initiate and observe purely electronic dynamics in the building blocks of life represents a crucial step forward in attosecond science, which is progressively moving towards the investigation of more and more complex systems and can be considered as a first contribution towards attobiology.
Direct measurement of the ultrafast charge dynamics in an amino acid, initiated by attosecond pulses, represents a crucial benchmark for the extension of attosecond methodology to biology. In the same way in which femtosecond pulses have contributed (and still contribute) to the investigation and understanding of important biological processes, attosecond science offers the possibility to elucidate, on a temporal scale preceding nuclear motion, subtle processes ultimately triggering and determining the response of biomolecules. For instance, how the ultrafast motion of a hole in DNA created by a high-energy particle might initiate cell necrosis or mutation. The results obtained in the case of phenylalanine can be seen as the first experimental confirmation that attosecond pulses and techniques will be essential tools for understanding of dynamical processes on a temporal scale that is relevant for the evolution of crucial microscopic events at the heart of the macroscopic biological response of molecular complexes.
The picture shows XChem researchers directly involved in this work
 Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses
F. Calegari, D. Ayuso, A. Trabattoni, L. Belshaw, S. De Camillis, S. Anumula, F. Frassetto, A. Palacios, P. Decleva, J. B. Greenwood, F. Martín, M. Nisoli Science346, 336-339 (2014). DOI:10.1126/science.1254061
Supplementary material: Watching phenylalanine change one quintillionth of a second at a time