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# John Butler <jbutler1@uiuc.edu>
# requesting 4 days, at minimum=4 days
# beamline 33BM, Ion correlations in electrostatically condensed biopolymers
# instrument 33BM-B XAFS
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# top:/home/www/beamtime-requests/req00642.txt
# UNICAT Member Beam Time Request  #642
# created Mon Aug 16 12:15:04 CDT 2004
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beamline:
	33BM

collaboration:
	No

collaborator_Jenia:
	ON

contact:
	jbutler1@uiuc.edu

days:
	4

description:
	In this continuing program of research, we will use EXAFS techniques to investigate the spatial arrangement of counterions in like-charged polyelectrolyte bundles. While it is well known that many biological polyelectrolytes condense in the presence of oppositely charged multivalent ions, the mechanism of attraction is still not well understood. By studying the inter-ion correlations of the counterions that participate in bundling at molecular length scales, we will gain a better understanding of the role the counterions play in electrostatic condensation events. We will investigate the behavior of divalent Sr and Zn ions on F-actin, and trivalent cobalt hexamine ions on DNA, by looking at the inter-ion distances as a function of global ion concentration, and counterion valence. 

The inter-ion distances on DNA can be estimated by Co-Co distances, and those on F-actin by Sr-Sr and Zn-Zn distances. Co, Sr, and Zn have core-shell levels that are accessible using EXAFS at beamline 33BM.  Data from our experiment in 6/2004 suggests an inter-ion distance of approximately six angstroms.  Additional samples need to be measured, however, to confirm that the feature in question is in fact an inter-ion distance.  Some of the samples will also be used to try to determine if we can see the correlations across different species of ions and polymers.

equipment_required:
	Standard EXAFS equipment.

experiment:
	Ion correlations in electrostatically condensed biopolymers

foreign_nationals:
	Abhijit Mishra

hazards:
	hThere are unique hazards associated with this experiment.  All materials will be in hermetically sealed quartz capillaries.

instrument:
	33BM-B XAFS

instrument_other:
	

minimumdays:
	4

name:
	John Butler

nonmembers:
	None

unacceptable_dates:
	

z34ID_details:
	


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