Droplet streams for serial crystallography of proteins

Abstract

Abstract. Serial diffraction of proteins requires an injection method to deliver protein moleculespreferably uncharged, fully hydrated, spatially oriented, and with high flux -into the crossed beams of an alignment laser and a focused probe beam of electrons or X-rays of typically only a few tens of microns diameter. The aim of this work has been to examine several potential droplet sources as to their suitability for this task. We compare Rayleigh droplet sources, electrospray sources, nebulizers and aerojet-focused droplet sources using time-resolved optical images of the droplet beams. Shrinkage of droplets by evaporation as a means of removing most of the water surrounding the proteins is discussed. Experimental measurements of droplet size, conformation of proteins after passing through a Rayleigh jet, and triboelectric charging are presented and conclusions are drawn about the source configuration for serial diffraction. First experimental X-ray diffraction patterns from Rayleigh droplet beams doped with 100nm gold balls are shown.

X-ray imaging beyond the limits

“…These particles may be in a liquid droplet stream 23 ( Fig. 2), or brought into the gas phase by aerodynamically focusing an aerosol of the particles 24 .…”

Structure-factor analysis of femtosecond microdiffraction patterns from protein nanocrystals

“…Briefly, fully hydrated PSI nanocrystals [Protein Data Bank (PDB) data entry 1JB0], within their native harvesting buffer [5 mM MES, where MES is 2-(Nmorpholino)ethanesulfonic acid, pH 6.4 and 0.02% betadodecylmaltoside], were delivered to the X-ray beam via a 4 mm continuous column of liquid generated by a gas-dynamic virtual nozzle described elsewhere (DePonte et al, 2008;Weierstall et al, 2008). Elastic X-ray scattering from the liquid jet is concentrated into a streak running normal to the velocity of the liquid.…”

Windowless microfluidic platform based on capillary burst valves for high intensity x-ray measurements

“…In each of the three steps, I-line UV contact lithography is used to transfer the mask layout into an 10-m-thick UV sensitive resist layer ͑AZ4562 standard resist͒, on top of the Si wafer. The resist functions as an etch mask in the subsequent DRIE process optimized for deep etching ͓etch: SF 6 : 230 SCCM ͑SCCM denotes cubic centimeter per minute at STP͒, O 2 : 23 SCCM, rf coil: 2800 W, rf platen: 19 W, cycle time: 8 s. Passivation: C 4 F 4 : 120 SCCM, rf coil: 1000 W, rf platen: 0 W, cycle time: 5 s.͒. The window and the backside hole are fabricated in the two first masking steps, and in the case of the substrate wafer, the channel structures are subsequently fabricated in a third masking step.…”

“…Taking water ͑n = 1.33͒ as a typical example, a path length of 100 m corresponds to a time delay between the pulses slightly larger than 100 fs thus limiting the sample thickness to 50-100 m if 100 fs time resolutions is to be conserved in the case of copropagating pump and probe beams. 3 Such sample dimensions are routinely achieved in microjet systems 4,5 and droplet shooters, 6 however, the curved interfaces inherent in these systems may cause refraction effects as well as decrease the coherence properties of the x-ray beam. Free-flowing films 7 with planar interfaces perpendicular to the x-ray beam may also reach the required maximum thickness but as well as stability, lack of vacuum compatibility, and large sample volumes are known issues.…”