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Title: Design and characterisation of functionalised self-assembled peptide nanostructures
Author: Maude, Steven
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2010
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This work develops the Pl1 peptide family as new materials, utilising a strategy of mod- ifying existing peptides to tune them to specific end uses. Several peptides, based on the self-assembling, ,B-sheet forming Pl1-2 sequence, were screened as potential tissue engineering materials. This was accomplished by studying the effect of net peptide charge on aggregation and secondary structure in physiological conditions, applying both proton NMR and IR spectroscopies. Single increments of net peptide charge produce large increases in critical aggregation concentration and decreases in peptide aggregate fraction at fixed concentration. No self-assembly was detected for peptides with net charges > 3, even at high mM concentration. At least a small net charge is required for solubility. Based on these studies, a peptide with a -2 charge, Pn-4, was selected for further study. The remainder of the studies explore the use of P n-4 as a scaffold for small (peptide) and large (protein) groups. Using TEM and AFM, the self-assembly of Pn-4 has been compared to Pn-4 functionalised with bioactive RGD peptides. Two modified Pn-4 peptides (LR66 and LR46) self-assembled to some extent. Two others (LR56 and LR44) did not appear to display Pn-4-type self-assembly, though, on their inclusion in mixtures with Pn-4, the resulting structures appeared more like those of unmodified Pn-4. Finally, an amphiphilic fusion protein, KSI-(Pn-4h-His6, comprised of ketosteroid isomerase, a trimeric Pn-4 and a hexahistidine tag was investigated. KSI-(Pn-4h-His6 was sparingly soluble in H20 near neutral pH, but more soluble at low and high pH. AFM and TEM studies indicated KSI-(Pn-4h-His6 in H20 is in the form ofround particles. No Pn-4-like aggregates were observed, implying the attached protein disrupts self-assembly. Tensiometer studies at the air-water interface demonstrate that KSI-(Pn-4h-His6 is a promising protein surfactant, with surface tension reductions - at concentrations up to 1 mg ml-1 - bettering or closely matching that of the model ,B-Iactoglobulin.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available