Optimization of buffer conditions for aggregation of polypeptides

• Main Author: Er, Hsian Cong
• Other Authors: Ali Gilles Tchenguise Miserez
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Materials::Biomaterials
• Online Access: https://hdl.handle.net/10356/148211
• Institution: Nanyang Technological University

Onychophorans, commonly known as velvet worms are carnivorous invertebrates that can eject slime for hunting and defence. The ejected slime can form stiff biopolymeric fibres after shearing and drying. Notably, the fibres can dissolve in water and new fibres can be drawn from the solution. The combination of its magnificent mechanical and recyclability properties pave the way for the production of recyclable biopolymers in the future. The objective of the project is to understand the conditions needed to trigger a conformational change in slime proteins by optimizing the buffer properties like pH and ionic strength for small peptides within slime proteins. Seven different peptides were obtained from the aggregation-prone region of Er_P1, coding for a key protein in Euperipatoides rowelli. The peptides were studied using change in absorbance to detect the presence of aggregation. It was determined that pH 4 citrate buffer and no salt solution added will lead to high aggregation of peptides. Nuclear Magnetic Resonance (NMR) was used to detect the structures of the aggregates that were formed for the different peptides. Circular Dichroism (CD) was used to determine the secondary structures of the proteins. Two peptides showed a propensity towards random coil structure with a certain amount of beta-sheets and beta-turns that resembles velvet worm slime fibres.