NMR
MicroED: From Powder to Structure in a Half-Hour
Posted on by Dr. Francis Collins
Credit: Adapted from Jones et al. ChemRxiv.org
Over the past few years, there’s been a great deal of excitement about the power of cryo-electron microscopy (cryo-EM) for mapping the structures of large biological molecules like proteins and nucleic acids. Now comes word of another absolutely incredible use of cryo-EM: determining with great ease and exquisite precision the structure of the smaller organic chemical compounds, or “small molecules,” that play such key roles in biological exploration and drug development.
The new advance involves a cryo-EM technique called microcrystal-electron diffraction (MicroED). As detailed in a preprint on ChemRxiv.org [1] and the journal Angewandte Chemie [2], MicroED has enabled researchers to take the powdered form of commercially available small molecules and generate high-resolution data on their chemical structures in less than a half-hour—dramatically faster than with traditional methods!
Got It Down Cold: Cryo-Electron Microscopy Named Method of the Year
Posted on by Dr. Francis Collins
Caption: Composite image of beta-galactosidase showing how cryo-EM’s resolution has improved dramatically in recent years. Older images to the left, more recent to the right.
Credit: Veronica Falconieri, Subramaniam Lab, National Cancer Institute
In the quest to find faster, better ways of mapping the structure of proteins and other key biological molecules, a growing number of researchers are turning to an innovative method that pushes the idea of a freeze frame to a whole new level: cryo-electron microscopy (cryo-EM). The technique, which involves flash-freezing molecules in liquid nitrogen and bombarding them with electrons to capture their images with a special camera, has advanced dramatically since its inception thanks to the efforts of many creative minds. In fact, cryo-EM has improved so much that its mapping performance now rivals that of X-ray crystallography [1], the long-time workhorse of drug developers and structural biologists.
To get an idea of just how far cryo-EM has come over the last decade, take a look at the composite image above, which shows a bacterial enzyme (beta-galactosidase) bound to a drug-like molecule (phenylethyl beta-D-thiogalactopyranoside). To the left, you see a blob-like area generated by cryo-EM methods that would have been considered state-of-the-art just a few years ago. To the right, there’s an exquisitely detailed structure, which was produced at more than 10-times greater resolution using the latest advances in cryo-EM. In fact, today’s cryo-EM is so powerful that researchers can almost make out individual atoms! Very impressive, and just one of the many reasons why the journal Nature Methods recently named cryo-EM its “Method of the Year” for 2015 [2].
