Conformational and Orientational Dynamics of Semi-Rigid Macromolecules in Shear Flow

"The third study involves the conformational and phase stability of aqueous Poly-L-Lysine solutions in shear flow. Poly-L-lysine exists as an α-helix at high pH and a random coil at neutral pH. When the α-helix is heated above 27$\sp\circ$C, the macromolecule undergoes a conformational transition to a β-sheet. In this study, the stability of the secondary structure of poly-L-lysine in solutions subjected to shear flow, at temperatures below the α-helix to β-sheet transition temperature, were examined using Raman spectroscopy and circular dichroism (CD). Solutions initially in the α-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 β-sheet structure evidenced by the amide I band at 1666 cm$\sp{-1}$. CD measurements indicated that solutions of predominantly α-helical conformation at 20$\sp\circ$C transformed into 85% α-helix and 15% β-sheet after being sheared for 20 minutes. However, on continued shearing the content of β-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.)."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Immaneni, Aravind

Contributors dc:contributor

• McHugh, A.J.

• Engineering, Chemical

Language dc:language

eng

Identifier

(MiAaPQ)AAI9812639

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/82443