Application of Functional Amyloids in Morphological Control and in Self-assembled Composites

Amyloids are self-assembled protein materials containing beta-sheets. While most studies focus on amyloids as the pathogen in neurodegenerative disease, there are instances of "functional" amyloids used to preserve life. Functional amyloids serve as an inspiration in materials design. In this study, it is shown that wheat gluten (WG) and gliadin:myoglobin (Gd:My) amyloid morphology can be varied from predominantly fibrillar at low polypeptide concentration to predominantly globular at high polypeptide concentration as measured at the nanometer scale using atomic force microscopy (AFM). The ability to control the morphology of a material allows control of its properties. Fourier transform infrared (FTIR) spectroscopy shows that at low concentration, fibrils require interdigitation of methyl groups on alanine (A), isoleucine (I), leucine (L), and valine (V). At higher concentration, globules do not have the same interdigitation of methyl groups but more random hydrophobic interactions. The concentration dependence of the morphology is shown as a kinetic effect where many polypeptides aggregate very quickly through hydrophobic interactions to produce globules while smaller populations of polypeptides aggregate slowly through well-defined hydrophobic interactions to form fibrils. Functional amyloids also provide a means of creating a low energy process for composites. Poor fiber/matrix bonding and processing degradation have been observed in previous WG based composites. This study aims to improve upon these flaws by implementing a self-assembly process to fabricate self-reinforced wheat gluten composites. These composites are processed in aqueous solution at neutral pH by allowing the fibers to form in a matrix of unassembled peptides. The fiber and the matrix are formed from the same solution, thus the two components create a compatible system with ideal interfacial interaction for a composite. The fibers in the composite are about 10 microns in diameter and can be several millimeters long. It has been observed that the number of fibers present along the fracture surface influences the modulus of the composite. In this study, self-assembled wheat gluten composites are formed and then characterized with 3-point bend (3PB) mechanical testing, scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biological Systems Engineering

Department dc:contributor.department

Biological Systems Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2013

Author dc:creator

• Claunch, Elizabeth Carson

Chair dc:contributor.committeechair

• Barone, Justin R.

Committee members dc:contributor.committeemember

• Renneckar, Scott Harold
• Senger, Ryan S.

• amyloid
• self-assembly
• morphology
• composite
• Fourier transform infrared spectroscopy
• atomic force microscopy

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

vt_gsexam:998

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/23209