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

Experimental mini-accelerator achieves record energy

Coupled terahertz device significantly improves electron beam quality

Scientists at DESY have achieved a new world record for an experimental type of miniature particle accelerator: For the first time, a terahertz powered accelerator more than doubled the energy of the injected electrons. At the same time, the setup significantly improved the electron beam quality compared to earlier experiments with the technique, as Dongfang Zhang and his colleagues from the Center for Free-Electron Laser Science (CFEL) at DESY report in the journal Optica. “We have achieved the best beam parameters yet for terahertz accelerators,” said Zhang. “This result represents a critical step forward for the practical implementation of terahertz-powered accelerators,” emphasized Franz Kärtner, who heads the ultrafast optics and X-rays group at DESY.
Terahertz radiation lies between infrared and microwave frequencies in the electromagnetic spectrum and promises a new generation of compact particle accelerators. “The wavelength of terahertz radiation is about a hundred times shorter than the radio waves currently used to accelerate particles,” explained Kärtner. “This means that the components of the accelerator can also be built to be around a hundred times smaller.” The terahertz approach promises lab-sized accelerators that will enable completely new applications for instance as compact X-ray sources for materials science and maybe even for medical imaging. The technology is currently under development.

> Read more on the DESY website

Image: The two-stage miniature accelerator is operated with terahertz radiation (shown here in red). In a first step (left) the electron bunches (shown in blue) are compressed, in a second step (right) they are accelerated. The two individual elements are each about two centimetres wide. Credit: DESY, Gesine Born