Observation of a single protein by ultrafast X-ray diffraction

The idea of using ultrashort X-ray pulses to obtain images of single proteins frozen in time has fascinated and inspired many.It was one of the arguments for building X-ray free-electron lasers.According to theory,the extremely intense pulses provide sufficient signal to dispense with using crystals as an amplifier,and the ultrashort pulse duration permits capturing the diffraction data before the sample inevitably explodes.This was first demonstrated on biological samples a decade ago on the giant mimivirus.Since then,a large collaboration has been pushing the limit of the smallest sample that can be imaged.The ability to capture snapshots on the timescale of atomic vibrations,while keeping the sample at room temperature,may allow probing the entire conformational phase space of macromolecules.Here we show the first observation of an X-ray diffraction pattern from a single protein,that of Escherichia coli GroEL which at 14 nm in diameter is the smallest biological sample ever imaged by X-rays,and demonstrate that the concept of diffraction before destruction extends to single proteins.From the pattern,it is possible to determine the approximate orientation of the protein.Our experiment demonstrates the feasibility of ultrafast imaging of single proteins,opening the way to single-molecule time-resolved studies on the femtosecond timescale.

Attosecond precision multi-kilometer laser-microwave network

Synchronous laser-microwave networks delivering attosecond timing precision are highly desirable in many advanced applications,such as geodesy,very-long-baseline interferometry,high-precision navigation and multi-telescope arrays.In particular,rapidly expanding photon-science facilities like X-ray free-electron lasers and intense laser beamlines require system-wide attosecond-level synchronization of dozens of optical and microwave signals up to kilometer distances.Once equipped with such precision,these facilities will initiate radically new science by shedding light on molecular and atomic processes happening on the attosecond timescale,such as intramolecular charge transfer,Auger processes and their impacts on X-ray imaging.Here we present for the first time a complete synchronous laser-microwave network with attosecond precision,which is achieved through new metrological devices and careful balancing of fiber nonlinearities and fundamental noise contributions.We demonstrate timing stabilization of a 4.7-km fiber network and remote optical–optical synchronization across a 3.5-km fiber link with an overall timing jitter of 580 and 680 attoseconds root-mean-square,respectively,for over 40 h.Ultimately,we realize a complete laser-microwave network with 950-attosecond timing jitter for 18 h.This work can enable nextgeneration attosecond photon-science facilities to revolutionize many research fields from structural biology to material science and chemistry to fundamental physics.