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# Hacene Boukari <boukarih@mail.nih.gov>
# requesting 3 days, at minimum=2 days
# beamline 33ID, "X-ray induced bubbles"
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# top:/home/www/beamtime-requests/req00323.txt
# UNICAT Member Beam Time Request  #323
# created Mon Dec 09 14:04:50 CST 2002
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beamline:
	33ID

collaboration:
	Yes

collaborator+Pete:
	on

contact:
	boukarih@mail.nih.gov

days:
	3

description:
	Our recent experiments, performed at 33ID UNICAT beamline, showed, convincingly and surprisingly, that the intense X-ray source induces the formation of gas bubbles in various solutions: distilled water, protein (tubulin, albumin) in different buffers, and buffers alone.   As far as we know, this effect -the X-ray induced bubbles- is poorly understood and has become a major issue in pursuing our original objectives, mainly the structural characterization of several protein aggregates in solution under various conditions.  Indeed, the interpretation of our USAXS measurements (and potentially other X-ray measurements) is hindered and complicated significantly by this effect although we varied several factors (X-ray intensity, concentration of proteins, X-ray windows) to control and reduce its impact on the measurements.   In the present proposed experiments we plan to investigate in a systematic and quantitative way several aspects of the effect in an attempt to shed light into its physical and chemical mechanisms.  Here, we propose to combine laser-turbidity (transmission) measurements, laser-scattering measurements, and video recordings with USAXS measurements to elucidate the stages of the formation of the bubbles in pure water (distilled and degassed), salted water, and protein solutions as a function of X-ray intensity, salt and/or protein concentration, and pH buffers.  In principle, the turbidity and light-scattering measurements, which will be collected using a low-intensity laser beam (~mW), are very sensitive in probing the initial stage of the bubble formation immediately following the application of the X-ray beam.  Video recordings will be used to monitor the kinetics of the bubbles as they become sizeable (submillimeter to millimeter) for visual observations.  USAXS will be complementary and useful to probe and characterize existing and/or X-ray induced structures (submicron to micron size) in the solution.  We hope that the experimental results of this proposal would put a basis for developing a model that could explain this unsettling though physically interesting phenomenon.

equipment+required:
	Video Recorder

experiment:
	X-ray induced bubbles

foreign+nationals:
	

hazards:
	None

minimumdays:
	2

name:
	Hacene Boukari

new+request:
	on

nonmembers:
	Ralph J. Nossal
	Dan L. Sackett
	Susan Krueger

unacceptable+dates:
	January 29 to March 12, 2002.


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