Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesiTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A self-resonant microhelix can make X-band electron paramagnetic resonance (EPR) measurements possible on very small protein crystals by concentrating the microwave magnetic field around the sample. In a 2019 study, researchers reported up to a 28-fold signal-to-noise improvement over commercial EPR resonators and demonstrated the setup on crystals of [FeFe]-hydrogenase and photosystem II. That figure is the study’s maximum reported gain, not a guaranteed result for other samples or instruments.
Why are tiny protein crystals difficult to measure with EPR?
EPR detects paramagnetic species—such as enzyme intermediates—by measuring their interaction with a magnetic field and microwave radiation. In a conventional arrangement, the sample sits inside a microwave resonator. When a crystal is very small, it can produce a signal too weak to measure efficiently.
Single-crystal EPR is valuable because it can reveal the orientation of a paramagnetic species’ magnetic properties within a crystal. Researchers can then relate spectroscopic information about an enzyme intermediate to structural information from crystallography. This is a complementary use of the methods, not a replacement for X-ray crystallography.
What is the self-resonant microhelix setup?
Sidabras and colleagues combined a tightly wound, self-resonant microhelix with a planar microcoupler on a printed circuit board. The microcoupler drives the helix, whose small geometry concentrates the microwave magnetic field around the crystal. This improves the resonator’s filling factor: more of the field interacts with the small sample.
#1 Best Overall
- Lab equipment & instruments
- Made in united states
- Wilmad-LabGlass is a leading manufacturer of NMR and EPR sample tubes and accessories, a diverse line of Laboratory Glassware and Scientific Equipment, as well as Precision Engineered Glass, OEM Quartz components and assemblies. Our goal has always been to provide you with superior service, support and technical know-how. In addition, we offer select glass repair services to maximize the life of your laboratory items. Limited 90-day warranty included. Scientists rely on the expertise and artistic skills of Wilmad-LabGlass' engineers and glass specialists to manufacture NMR and EPR consumables and laboratory glassware of the highest quality. Used daily in academia, healthcare and chemical, petroleum and other industrial applications, Wilmad offers 7000+ items as part of their standard catalog as well as custom fabrication for individual glassware, glass repair services and OEM glass parts.
- 90-day limited warranty
The researchers implemented the design in a commercial X-band EPR spectrometer operating at 9.5 GHz. The paper describes sensitivity for protein crystals with volumes below 27 nL. Jason Sidabras described the microhelix to Chemistry World as “a lens for magnetic flux that is designed to maximise the filling factor for very small samples.”
How much more sensitive was it?
In the authors’ reported comparison, the microhelix setup achieved up to a 28-fold improvement in signal-to-noise ratio relative to commercial EPR resonators. The result is an experimental maximum from the study, not a universal multiplier. Signal quality depends on factors including the sample, crystal orientation, temperature, resonator configuration and measurement conditions.
Sidabras also told Chemistry World that experiments that had taken weeks could be performed in days. That is his reported comparison, not a timing result established as a general performance guarantee by the paper. The primary study’s quantified comparison is the signal-to-noise improvement.
Which protein crystals did the researchers test?
[FeFe]-hydrogenase
The team measured single crystals of [FeFe]-hydrogenase from Clostridium pasteurianum (CpI), including the Hox state, and reported a proposed g-tensor orientation. The demonstrated crystal measured 0.3 × 0.1 × 0.1 mm.
Photosystem II
The researchers also reported continuous-wave EPR measurements of the YD radical in a photosystem II single crystal, recorded at two orientations and 80 K. Together, these experiments show feasibility on two protein systems; they do not establish that every crystal or EPR experiment will work equally well.
Can EPR and X-ray crystallography use the same microcrystals?
The approach is relevant to researchers seeking to connect EPR measurements with crystallographic structural information from small crystals. Stefan Stoll of the University of Washington called the work “a really nice technological improvement,” while Dimitri Svistunenko of the University of Essex described its promise for relating EPR data to X-ray crystallography data obtained on the same batch of microcrystals, as reported by Chemistry World. The study supports this as an application of the method; it does not show that EPR and crystallography are interchangeable techniques.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the study establishes—and what it does not
- Established: A self-resonant microhelix paired with a planar microcoupler can improve sensitivity for small protein crystals in the reported X-band EPR setup.
- Measured in the study: Up to a 28-fold signal-to-noise improvement compared with commercial EPR resonators.
- Demonstrated: Measurements on [FeFe]-hydrogenase and photosystem II single crystals.
- Not established: A guaranteed 28-fold gain across samples, instruments or conditions; routine adoption; or a currently available retail product or standard accessory model.
The primary paper by Sidabras and colleagues appeared in Science Advances on 4 October 2019. Its full text and methods are available through PubMed Central; PubMed lists its publication metadata. The authors state that MATLAB code and data are available through the ACT-EPR project website.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
