Tag Archives: duane loh

Diffraction before destruction

by Chun Hong Yoon, Mikhail V. Yurkov, Evgeny A. Schneidmiller, Liubov Samoylova, Alexey Buzmakov, Zoltan Jurek, Beata Ziaja, Robin Santra, N. Duane Loh, Thomas Tschentscher & Adrian P. Mancuso

Scientific Reports. 6 (2016) 24791. doi: 10.1038/srep24791.

Nanometer-sized biological molecules are difficult to resolve because they are fragile: they come apart when they are imaged with energetic x-rays or electrons. Fortunately, ultra-short x-ray laser pulses billions of times brighter than previous x-ray sources can now illuminate single biomolecules to produce faint but meaningful signals. These signals are then statistically combined to yield structural information. Because these x-ray pulses are so short, they flee from biomolecules before the latter get a chance to move or show damage. This property permits so-called “diffraction before destruction”, where scientists can image unsuspecting and unperturbed nanoscale objects in their native environment.

Hundreds of experimental parameters modify how x-ray free-electron lasers are generated, focused, made to interact with biomolecules, then detected, and analysed. The combinatorial complexity of such imaging experiments is staggering, which makes designing such experiments tricky, tedious and frustratingly uncertain. Dr Duane LOH from the Centre for Bio-imaging Sciences, together with four other groups of scientists from CFEL and the European XFEL (Hamburg, Germany), has created a comprehensive multi-physics framework that realistically simulates for the first time, how specimen damage in single-particle imaging can be mitigated by instrument and algorithm design.

Read online: Scientific Reports.

Read Diffraction before destruction: Scientists in NUS have demonstrated how x-ray lasers could help us image biological macromolecules in water from NUS Faculty of Science.


Fractal morphology: Imaging and mass spectrometry of single aerosol particles in flight

by N D Loh, C Y Hampton, M J  Bogan et al.

Nature 486 (2012)

Ultra-bright femtosecond pulses from x-ray free electron lasers (XFELs) have produced diffraction patterns of unprecedented resolution from single nanoscale objects before the onset of radiation damage.

In this work, we have developed statistical tools that probed the nanoscale heterogeneity of single soot aerosols in flight. These tools will eventually be extended to resolve high- resolution structural heterogeneity of biomolecules without the need for crystallization.

Pictured above:  Structural complexity in aerosol soot. Scale-invariant random processes drive the growth and aggregation of these aerosols, which results in fractal-like geometrical properties.

Read online: Nature.

Learn more about ND Loh’s research.

Sensing the wavefront of x-ray free-electron lasers using aerosol spheres

by N D Loh, et al

Optics Express 21(10) 12385-12394 (2013)

Hartmann sensors can determine wavefront errors in optical systems by measuring deviated optical paths from carefully positioned lenses. But what if these lenses are randomly inserted, and destroyed immediately after illumination?

Despite such randomness, we show, for the first time, that wavefront properties of the unattenuated intense focus of x- ray free-electron laser can still be computationally assembled to aid optical design.

Pictured above: X-ray pulse fluctuations deduced from diffraction data. Fluctuations in wavefront tilts and intensity of x-ray pulses shown in contour plot above.

Read online: Optics Express.

Learn more about  N D Loh’s research.