Ultrafast lasers protect a DNA building block from destruction

An international research team led by DESY researcher Francesca Calegari and with the key participation of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) has demonstrated that ultrashort laser pulses can be used to protect one of the DNA building blocks against destruction induced by vacuum ultraviolet (VUV) radiation. The research group unveiled that a second laser flash in the infrared, timed shortly (only a few millionths of billions of a second) after the first VUV flash, prevented the adenine molecule to disintegrate, therefore stabilising it. The group presents their work in the journal Communications Chemistry published by Nature publishing group.

High energy radiation can cause irreparable damage to our own biological molecules – such as DNA – leading to mutations and potentially cell death. Damage is often occurring as a consequence of the molecular ionisation, inducing the fragmentation of the DNA subunits. So far, protection against radiation damage has hardly been achieved, as the photo-induced dissociation process could not be stopped. In their ultra-short-time experiments, Francesca Calegari´s research group and collaborators have discovered that, by taking advantage of mechanisms that take place on extremely fast time scales, it is indeed possible to protect the molecule.

Read more on the DESY website

image: Artist´s impression of the ultrafast stabilisation of adenine against dissociation: When the molecule is ionised by VUV radiation it undergoes dissociation, however, by taking advantage of a charge migration mechanism and by properly timing a second infrared laser pulse it is possible to stabilise it via a second ionisation event.

Credit: U. De Giovannini MPSD

New insights into the photochemical activity of titanium dioxide

Not so many compounds are as important to industry and medicine today as titanium dioxide (TiO2). The electronic structure of transition metal oxides is an important factor determining the chemical and optical properties of materials. Specifically for metal-oxide structures, the crystal-field interaction determines the shape and occupancy of electronic orbitals. Consequently, the crystal-field splitting and resulting unoccupied state populations can be foreseen as modeling factors of the photochemical activity. The research on titanium dioxide inaugurated the presence of IFJ PAN scientists in research programs carried out at the SOLARIS synchrotron. The measurements, co-financed by the National Science Center, were carried out at the XAS beamline.

In many chemical reactions, TiO2 appears as a catalyst. As a pigment, it occurs in plastics, paints, and cosmetics, while in medical implants, it guarantees their high biocompatibility. A group of scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, led by Dr. Jakub Szlachetka, engaged in research on the oxidation processes of the outer layers of titanium samples and related changes in the electronic structure of this material. Scientists from the IFJ PAN conducted their latest measurements, co-financed by the National Science Center, at the XAS beamline. They analyzed how X-rays are absorbed by the surface layers of titanium samples previously produced at the Institute under carefully controlled conditions.

Read more on the SOLARIS website