All-optical attoclock: accessing exahertz dynamics of optical tunnelling through terahertz emission

The debate regarding attosecond dynamics of optical tunneling has so far been focused on time delays associated with electron motion through the potential barrier created by intense ionizing laser fields and the atomic core. Compelling theoretical and experimental arguments have been put forward to advocate the polar opposite views, confirming or refuting the presence of tunnelling time delays. Yet, such delay, whether present or ot, is but a single quantity characterizing the tunnelling wavepacket; the underlying dynamics are richer. Here we propose to complement photo-electron detection with detecting light, focusing on the so-called Brunel adiation -- the near-instantaneous nonlinear optical response triggered by the tunnelling event. Using the combination of single-color and two-color driving fields, we determine not only the ionization delays, but also the re-shaping of the tunnelling wavepacket as it emerges from the classically forbidden region. Our work introduces a new type of attoclock for optical tunnelling, one that is based on measuring light rather than photo-electrons. All-optical detection paves the way to time-resolving multiphoton transitions across bandgaps in solids, on the attosecond time-scale

Stiff‐Stilbene Ligands Target G‐Quadruplex DNA and Exhibit Selective Anticancer and Antiparasitic Activity

G-quadruplex nucleic acid structures have long been studied as anticancer targets whilst their potential in antiparasitic therapy has only recently been recognized and barely explored. Herein, we report the synthesis, biophysical characterization, and in vitro screening of a series of stiff-stilbene G4 binding ligands featuring different electronics, side-chain chemistries, and molecular geometries. The ligands display selectivity for G4 DNA over duplex DNA and exhibit nanomolar toxicity against Trypasanoma brucei and HeLa cancer cells whilst remaining up to two orders of magnitude less toxic to non-tumoral mammalian cell line MRC-5. Our study demonstrates that stiff-stilbenes show exciting potential as the basis of selective anticancer and antiparasitic therapies. To achieve the most efficient G4 recognition the scaffold must possess the optimal electronics, substitution pattern and correct molecular configuration.M.P.O. thanks the Bristol Chemical Synthesis Centre for Doctoral Training, funded by EPSRC (EP/L015366/1) and the University of Bristol for a PhD studentship. J.C.M./P.P. thank Spanish Ministerio de Ciencia Innovación y Universidades (Grants CTQ2015- 64275-P and RTI2018-099036-B-I00). M.C.G. thanks the European Research Council (ERC-COG: 648239