#################################################### # Gerard Wong (PI) and John Butler # requesting 4 days, at minimum=4 days # beamline 33BM, Investigation of inter-ion correlations in condensed polyelectrolyte systems # instrument 33BM-B XAFS #################################################### # top:/home/www/beamtime-requests/req00503.txt # UNICAT Member Beam Time Request #503 # created Thu Nov 20 12:12:06 CST 2003 #################################################### beamline: 33BM collaboration: Yes contact: gclwong@uiuc.edu jbutler1@uiuc.edu days: 4 description: In this 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 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 distances. Both Co and Sr have core-shell levels that are accessible using EXAFS. equipment_required: Typical EXAFS experimental equipment. experiment: Investigation of inter-ion correlations in condensed polyelectrolyte systems foreign_nationals: hazards: Most samples will be brought to the APS in hermetically sealed quartz capillaries. However, solutions of strontium, cobalt hexamine, F-Actin, and DNA will be brought to the APS in case we need to prepare new samples. Otherwise, we do not anticipate any hazards associated with the experiment. instrument: 33BM-B XAFS instrument_other: minimumdays: 4 name: Gerard Wong (PI) and John Butler new_request: ON nonmembers: unacceptable_dates: March 21st-27th z34ID_details: #REMOTE_HOST: wong-m2.mrl.uiuc.edu #REMOTE_ADDR: 130.126.101.205 #CONTENT_LENGTH: 1736 #HTTP_REFERER: http://www.uni.aps.anl.gov/unireq.htm #HTTP_USER_AGENT: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)