TIME-RESOLVED FLUORESCENT X-RAY INTERFERENCE

A fluorescent X-ray interference method can effectively measure nanome ter-level conformational changes for non-crystallized molecules and pr oteins in aqueous conditions. The time-resolved technique can be used to obtain information about the dynamics of molecules and proteins. In strumentation for time-resolved fluorescent X-ray interference has bee n designed. A typical interference-fringe pattern was observed with ap proximately 3s of X-ray exposure time from K-fluorescent X-rays emitte d from a Zn monoatomic layer on an Rh substrate. The primary X-ray bea m was polychromed with a mirror for total external reflection of X-ray s and was tuned to an energy level at which only Zn K radiation became optimally excited. The glancing angle of the primary X-ray beam was f ixed at a glancing angle at which the total intensity of K-fluorescent X-rays emitted from Zn atoms corresponded to the maximum value. The f luorescent X-ray interference fringes were monitored with an imaging p late (IP) as a non-energy-dispersive two-dimensional detector. The exp osed interference fringes on the IP were integrated along the directio n of the fringes. The integrated fringes were in close agreement with a theoretical estimate based on the interference among transmitted and reflected waves at interfaces in the sample.