Atomic Force Microscopy Study of Fibril Formation of Lysozyme

摘要

Lysozyme, known as N-acetylmuramide glycanhydrolase, is a powerful enzyme of bi-ological significance found in abundance in tears, saliva, and human milk. Lysozyme damages bacterial cell walls by catalyzing hydrolysis of 1,4-beta-linkages between N-acytylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins. Lysozyme misfolding is involved in amyloidosis, along with other proteins, and contributes to neuronal cell death as associated with neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's diseases.;In this research, lysozyme protein from hen egg-white was stored in buffer solution at pH 2 and pH 2.7 at a temperature of 60°C, to see how the acidic buffer solution and the ele-vated temperature affect the lysozyme fibril formation. The highest concentration of the solu-tion had a tendency to form fibrils fastest; the lowest concentration of lysozyme needed longer time to form fibrils. Lysozyme structures before and after forming the fibrils were imaged on a mica substrate using tapping mode atomic force microscopy (AMF). Also the fi-bril formation of lysozyme was analyzed using fluorescence spectroscopy to see the change of the primary and secondary structure of hen egg white lysozyme. In this technique, the amino acid tryptophan (Trp) was observed, which has a maximum absorbance near 350 nm, before growing the fibrils. The maximum emission changed after the fibril formation occurred as detected near 340 nm.