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.

Membrane destabilization by monomeric hIAPP observed at the single molecule level by Imaging Fluorescence Correlation Spectroscopy

by Nirmalya Bag, Ashraf Ali, Virander Singh Chauhan, Thorsten Wohland and Aseem Mishra

Chem Commun 2013, 49, 9155–9157

Monomeric hIAPP significantly destabilizes both model and live cell membranes by increasing membrane fluidity. This interaction with membranes happens via carpet formation followed by lipid extraction in a concentration dependent manner and thus we propose that hIAPP aggregation prior to membrane interaction may not be necessary for its cytotoxicity.

‘FCS movie’ of live cell membranes upon exposure to the membrane-active peptide amylin

The lateral diffusion of the cell membrane is mapped by imaging fluorescence correlation spectroscopy (Imaging FCS) with 240 nm spatial resolution and 1 ms temporal resolution over a large membrane area (5´5 mm2). We created a 60-minute FCS time lapse movie to follow membrane dynamics upon interaction with amylin (hIAPP), a peptide involved in insulin secretion. The movie shows how the peptide interacts with the bilayer and changes diffusion patterns with time (blue areas forming with advancing time).

Read online: Royal Society Chemistry.

Learn more about Thorsten Wohland’s research.

Calcium oscillations-coupled conversion of actin travelling waves to standing oscillations

by Wu M, Wu X, De Camilli P

Proc Natl Acad Sci USA  2013 Jan 22;110(4):1339-44

Dynamic spatial patterns of signaling factors or macromolecular assemblies in the form of oscillations or traveling waves have emerged as important themes in cell physiology. Feedback mechanisms underlying these processes and their modulation by signaling events and reciprocal cross-talks remain poorly understood. In this work we show that antigen stimulation of mast cells triggers cyclic recruitment of curvature-generating protein FBP17 and actin regulatory factors that can be manifested in either spatial pattern. Further mechanistic studies revealed an unexpected pattern-rendering mechanism.

Read online: PNAS.

Learn more about Wu Min’s research.