Insights from Austin

Structure-based drug design uses the three-dimensional structure of a target protein to identify functional binding sites and design drug molecules that complement their shape, size, and electrostatic properties. This approach has enabled major advances in medicine, including HIV protease inhibitors, antibiotics, and targeted cancer therapies such as imatinib.

A high-resolution cryo-EM map can still leave important regions unresolved. Here's what missing density may and may not tell you about protein structure, flexibility, and conformational heterogeneity.

Electron paramagnetic resonance (EPR) spectroscopy is one of the most effective methods for studying membrane protein structure and dynamics. Unlike X-ray crystallography and cryo-electron microscopy, which provide static structural snapshots, EPR measures conformational ensembles and molecular motions under native-like conditions. This makes it particularly valuable for investigating GPCRs, ion channels, and membrane transporters involved in drug discovery.

The Rocky Mountain Conference on Magnetic Resonance remains one of the premier gatherings for the EPR community. This year, High Q Technologies will share new advances in automated EPR spectroscopy with the FATHOM system, highlighting improved sensitivity, phase stability, and applications in structural biology and challenging membrane protein research.

As structural biology/drug discovery moves toward ensemble-based views of proteins, Electron Paramagnetic Resonance (EPR) spectroscopy is becoming one of the most important techniques for studying biomolecular dynamics. EPR studies are increasingly being used to complement existing structural data from techniques like Cryo-EM, NMR, or X-ray Crystallography, providing dynamic information that can be difficult to obtain otherwise. In this post, we will take a look at Electron Paramagnetic Resonance spectroscopy (EPR), and why it keeps showing up in protein dynamics studies.

Techniques like Nuclear Magnetic Resonance (NMR) spectroscopy have long been a cornerstone of structural biology, providing atomic-level insight into protein structure and dynamics in solution. NMR remains one of the most powerful tools for studying folded protein domains, as well as local, site-specific dynamics in partially disordered and flexible regions.

As the Biophysical Society Annual Meeting approaches, it is a good time to reflect on the progress the community has made in the field in years past as well as aspire to continue pushing boundaries as we look toward the future.

Drug discovery cannot happen in a vacuum – it requires a constant influx of new ideas, information, and technology to advance. During my recent attendance at Discovery on Target, there was a consistent underlying message that despite the proprietary nature of an organization’s approach, drug discovery is a group effort. With collaboration a key theme throughout the conference, I want to expand on some of the more salient talking points, and how I believe High Q and the EPR community can contribute to the conversation.

Advancements in science are often spurred by the ‘new.’ Be it new technology, new techniques, or new ideas, novel abilities will beget novel outcomes. The field of EPR has seen this effect throughout its history – beginning with the discovery of the phenomenon itself, and driven forward by breakthroughs such as the development of site-directed spin labeling and distance measurement techniques that enable structural studies on biomolecules; membrane mimetics and in-cell/in-vivo methods to capture physiologically relevant data; in-silico modeling, simulation, and analyses packages; and improvements in hardware, resonators, and pulse-shaping. It is a never-ending upward spiral of new discoveries prompting more questions, requiring new tools to investigate. During my recent visit to the Rocky Mountain Conference on Magnetic Resonance in Denver, several talks emphasized just how far this field has come, how it has benefitted from such advancements, and what new tools could push it even further.

Previously I provided a high-level view of the fundamentals of EPR-based distance measurements. Today, and in future iterations, I will dig deeper into those distance methods, focusing on specific techniques, their strengths, drawbacks, and considerations. Each instance produces similar results – a distance distribution between two unpaired electron spins – but differ in implementation and optimization. Understanding the various factors at play within these methods is crucial to pair the optimal experiment with a given sample and environment.

Many biomolecules of interest lack inherent paramagnetic sites and are thus natively invisible to EPR. To make such systems EPR-detectable, there have been significant and concentrated efforts to develop means by which to incorporate paramagnetic species, either stable organic radicals or paramagnetic metal ions, site-specifically into proteins and nucleic acids. While spin labeling is a nuanced field, I will be introducing the basics of the technique and the three main classes of labels employed today: nitroxides, metal ions, and trityls.

In my first Insights post, wherein I reflected on the Biophysical Society Meeting, I aimed to raise EPR into the common scientific vernacular akin to techniques like CryoEM, which have seen monumental growth and adoption in recent years. I look forward to a time when EPR discussions needn’t start with, ‘Do you know what EPR is?’ However, until that day comes, it may behoove me to introduce you to the technique, providing valuable context and frame of reference for any past and future entries in this series. And so, in this post I will provide a brief overview of EPR, and more specifically, EPR-based distance measurements.