A New Technique for Molecular Dynamics Observation using Laboratory X-Ray Source

Abstract

Our laboratory has developed a single molecule observation method using X-ray which named Diffracted X-Ray Tracking (DXT). DXT monitors the information of three dimensional motions of single protein molecules by tracking diffracted spots from individual gold nanocrystals which labeled on each of the protein molecules. The accuracy of DXT reaches microsecond order of time resolution and picometer order of spatial resolution. So for, DXT has succeeded to discover dynamics of many physiological molecules such as major histocompatibility complex; MHC, Acetylcholine binding protein; AChBP, alpha-synuclein and so on. However, DXT has a weak point against a promotion of general use because DXT needs the large facility of synchrotron orbital radiation source to detect diffraction spots from single gold nanocrystals. Therefore, DXT using a small light source is very effective. When using a laboratory X-ray source, it is very clear that the signal to background ratio is better for the monochromatic X-ray diffraction than Laue diffraction using white x-rays. Furthermore, the monochromatic X-ray reduces the damage of measuring target. Recently, we developed a new technique to observe the molecular dynamics using laboratory X-ray source; Rigaku FR-D (Cu anode, 50kV, 60mA) and a small detector; PILATUS-100K. In our technique, observing and tracking single diffraction spots like DXT are no longer necessary but we could estimate the molecular dynamics from intensity or variance of the diffraction ring form multiple gold nanocrystals. Now, we try to distinguish molecular dynamics of AChBP between with or without toxin. In the meeting, we will report the details of our analytical technique.