A recent publication by Sarah Perry’s Research Group in the Chemical Engineering Department was just highlighted in Chemistry World, published by the Royal Society of Chemistry, and will also be spotlighted in the next annual report for the Advanced Photon Source. Lab on a Chip, with an impact factor of 6.115, originally posted the Perry Group’s article, entitled “Graphene-based microfluidics for serial crystallography,” on May 24, 2016. Perry’s paper was also published as part of a special issue of Lab on a Chip that highlights “Emerging Investigators”. Read Chemistry World highlight.
As writer Hannah Dunckley explained in the Chemistry World highlight (posted on June 13), “Introducing graphene into microfluidic devices can make it easier to study proteins at an atomic level, scientists in the US have shown. Devices that are thinner and interfere less with the measurements allow larger and more intricate protein structures to be resolved using techniques that rely on probing thousands of microcrystals.”
Dunckley added that a thin graphene layer improves the crystallography signal-to-noise ratio and acts as a barrier, protecting the protein crystals from dehydrating.
“Understanding the structure of proteins on the atomic level is crucial, particularly when it comes to designing drugs,” Dunckley wrote. “Traditional x-ray crystallography techniques rely on large crystals, which are difficult to grow for complex proteins and susceptible to radiation damage. More recently, serial crystallography using x-rays has become a leading method. This involves firing a beam of radiation from a synchrotron source at thousands of tiny crystals – around 1–10μm in size – to form a cumulative overview of the protein’s structure.”
But sometimes transferring the microcrystals from their growth medium to the sample chamber can cause damage, according to Dunckley in her Chemistry World highlight. To address this, microfluidic techniques are used to allow the crystals to be grown directly on-chip with minimal intervention. But doing this introduces fresh challenges.
“The current microfluidic technology tends to be limited by the thickness of the device and the amount of noise that you would get when you try and do on-chip analysis,’ Perry explained to Chemistry World. Perry’s group has addressed this issue by incorporating a large-area single-layer graphene film into the device.
In the Chemistry World highlight, John Helliwell, an expert in crystallography at the University of Manchester in the UK, described the use of graphene as “a beautiful and totally elegant way” of minimizing background scattering, enabling analysis of ever more complex protein structures.
Perry’s group is now focusing on shrinking down the dimensions and increasing the complexity of the device. A major goal is to develop an integrated microfluidic valving strategy that is compatible with the graphene-based chip architecture. With these more advanced microfluidic devices, the Perry lab is hoping to enable time-resolved protein structure determination for novel proteins such as caspases, a family of proteins involved in programmed cell death studied by Professor Jeanne Hardy’s lab in the Department of Chemistry at UMass Amherst.
In general, research in the Perry laboratory utilizes self-assembly, molecular design, and microfluidic technologies to generate biomimetic microenvironments to study and enable the implementation of biomolecules to address real-world challenges.
The original Lab on a Chip article was authored by Shuo Sui, Yuxi Wang, Kristopher W. Kolewe, Vukica Srajer, Robert Henning, Jessica D. Schiffman, Christos Dimitrakopoulos, and Perry. Read Lab on a Chip article: http://dx.doi.org/10.1039/C6LC00451B.
As the abstract from that Lab on a Chip article stated: “Microfluidic strategies to enable the growth and subsequent serial crystallographic analysis of micro-crystals have the potential to facilitate both structural characterization and dynamic structural studies of protein targets that have been resistant to single-crystal strategies. However, adapting microfluidic crystallization platforms for micro-crystallography requires a dramatic decrease in the overall device thickness. We report a robust strategy for the straightforward incorporation of single-layer graphene into ultra-thin microfluidic devices. This architecture allows for a total material thickness of only ∼1 μm, facilitating on-chip X-ray diffraction analysis while creating a sample environment that is stable against significant water loss over several weeks. We demonstrate excellent signal-to-noise in our X-ray diffraction measurements using a 1.5 μs polychromatic X-ray exposure, and validate our approach via on-chip structure determination using hen egg white lysozyme (HEWL) as a model system. Although this work is focused on the use of graphene for protein crystallography, we anticipate that this technology should find utility in a wide range of both X-ray and other lab on a chip applications.” (June 2016)