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oai:www.ideals.illinois.edu:2142/82443 2023-07-11 col_2142_5131 col_2142_11615 com_2142_5130 com_2142_9130 com_2142_8903

McHugh, A.J. Immaneni, Aravind 2015-09-25T20:44:05Z 2015-09-25T20:44:05Z 10000-01-01 1997 1997 "The third study involves the conformational and phase stability of aqueous Poly-L-Lysine solutions in shear flow. Poly-L-lysine exists as an $\alpha$-helix at high pH and a random coil at neutral pH. When the $\alpha$-helix is heated above 27$\sp\circ$C, the macromolecule undergoes a conformational transition to a $\beta$-sheet. In this study, the stability of the secondary structure of poly-L-lysine in solutions subjected to shear flow, at temperatures below the $\alpha$-helix to $\beta$-sheet transition temperature, were examined using Raman spectroscopy and circular dichroism (CD). Solutions initially in the $\alpha$-helical state showed time-dependent increases in viscosity with shearing, rising to values as much as an order of magnitude. Visual observation and turbidity measurements showed the formation of a gel like phase under flow. Laser Raman measurements demonstrated the presence of small amounts of $\beta$-sheet structure evidenced by the amide I band at 1666 cm$\sp{-1}$. CD measurements indicated that solutions of predominantly $\alpha$-helical conformation at 20$\sp\circ$C transformed into 85% $\alpha$-helix and 15% $\beta$-sheet after being sheared for 20 minutes. However, on continued shearing the content of $\beta$-sheet conformation decreased. The observed phenomena were explained in terms of a ""zipping up"" molecular model based on flow enhanced hydrophobic interactions similar to that observed in gel-forming flexible polymers. (Abstract shortened by UMI.)." Made available in DSpace on 2015-09-25T20:44:05Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 9812639.pdf: 5496219 bytes, checksum: 524b4c668b4dd7dbb527d83824b21aea (MD5) Previous issue date: 1997 Embargo set by: Seth Robbins for item 83724 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs U of I Only 140 p. Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997. http://hdl.handle.net/2142/82443 (MiAaPQ)AAI9812639 eng Engineering, Chemical Conformational and Orientational Dynamics of Semi-Rigid Macromolecules in Shear Flow text Chemical Engineering Chemical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.