New technology will revolutionize visualization of important biomolecules such as proteins

Proteins are probably the most important and diverse biomolecules in living systems

To fully understand proteins and their myriad functions, researchers have developed sophisticated means to observe and study them through advanced microscopy, improved integration of light detection, imaging software, and advanced hardware systems

In a new study, corresponding author Shaopeng Wang and his colleagues at Arizona State University describe a new technique that promises to revolutionize the imaging of proteins and other important biomolecules, allowing these tiny entities to be captured with unprecedented clarity and simpler methods than existing methods are visualized

"The method we report in this study uses plain coverslips instead of gold-coated coverslips, which has two advantages over our previously reported label-free single-protein imaging method," Wang said

He holds joint faculty positions at the Biodesign Center for Bioelectronics and Biosensors and the School of Bio and Health Systems Engineering

The new method, called evanescent scattering microscopy (ESM), is based on an optical property called total internal reflection, which was first discovered in ancient times

When the incident light is angled away from the vertical (relative to the surface), a "critical angle" is eventually reached, causing all incident light to be reflected instead of passing through the second medium

Complete internal reflection creates a vanishing field that, when these molecules attach to the glass cover, can excite cells or molecules, such as proteins, at the glass-water interface, allowing researchers to visualize them in stunning detail

Previous methods often fluorescently label biomolecules of interest, known as fluorophores, for better imaging

Instead, this method exploits the subtle irregularities of the surface of the cover glass, which creates a very striking contrast

Samples including proteins can be probed at extremely shallow depths (typically <100 microns) using evanescent wave scattering

The new study describes the use of ESM to detect four model proteins: bovine serum albumin (BSA), mouse immunoglobulin G (IgG), human immunoglobulin A (IgA), and human immunoglobulin M (IgM)

Interactions between proteins, including the rapid association and dissociation of individual proteins, were observed in a series of experiments

Evanescent Scattering Imaging of Single Protein Binding Kinetics and DNA Conformation Changes