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Structure and properties of the hydrogel-forming tripeptide glycyl-histidyl-glycine with varying sample composition
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Structure and properties of the hydrogel-forming tripeptide glycyl-histidyl-glycine with varying sample composition

Morgan Leigh Hesser
Master of Science (M.S.), Drexel University
Sep 2020
DOI:
https://doi.org/10.17918/00000946
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Abstract

Colloids Peptides
Peptide gelators are currently a field of interest in biomedical, biomaterial, and biophysical research. They provide good candidates for drug delivery as they are biodegradable and are based on physiological molecules, which can be easily tested for safe use in medical applications. Many known peptide hydrogelators require longer lengths (increasing cost) or a non-aqueous co-solvent (potentially increasing toxicity). Many short self-assembling peptides include strongly aromatic components such as phenylalanine or a capping group. Glycyl-histidyl-glycine (GHG) is an exception to this expectation. It is able to form hydrogels comprised of fibrils on the sub-millimeter scale. We first focused on identification of gel phase properties by investigating a sample with 175 mM concentration at pH/D 6.4. Rheology data indicate the gel strength to be on the order of 104 Pa. Vibrational circular dichroism (VCD) and infrared (IR) spectra indicate that the fibrillar network observed via microscopy are comprised of twisted [beta]-sheet tapes. We then explored the impact of altering the concentration and pH/D on the gel properties. We found that the strength of the gel can be optimized by altering the peptide concentration or by increasing the pH/pD at a given concentration. Increasing the pD at a given concentration also increases the fraction of fibrils comprising the gel as measured by the combined fractional intensity of the IR bands assigned to the gel phase.

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