What is Cryo-Electron Microscopy (cryo-EM)?

U.S. researchers have developed a new cryo-EM method called MagIC (Magnetic Isolation and Concentration), allowing imaging of biological molecules at concentrations 100 times lower than before.

About Cryo-Electron Microscopy

• Cryo-electron microscopy (cryo-EM) is an advanced imaging technique used to study the detailed structure of biological molecules like proteins, viruses, or DNA at very high resolution.
• Core Principle: Biological samples are rapidly frozen in vitreous (non-crystalline) ice and then imaged using an electron beam under cryogenic conditions. 
  • This preserves their natural structure and prevents radiation damage.
• Limitation: Cryo-electron microscopy (cryo-EM) requires high concentrations of biological molecules. 
  • Rare or hard-to-isolate molecules are difficult to image due to low availability.
• National Cryo EM Facilities: The first national cryo-EM facility was established at National Centre for Biological Sciences (NCBS)in 2017 and then subsequently in IISc, Bangaluru, and RCB Faridabad, IIT Kanpur.

Key Features Of MagIC (Magnetic Isolation and Concentration)

• Magnetic Clustering: The new method works by attaching molecules of interest in a sample to 50-nm beads, then using a magnet to clump the beads together.
• Efficiency at Low Concentration: This technique allows imaging even with sample concentrations as low as 0.0005 mg/ml, significantly reducing sample requirements.
• Accelerated Microscopy: Beads are easily visible even at low magnification, enabling rapid identification of particle-rich regions and faster data acquisition.
• Noise Reduction Strategy i.e. DuSTER: Small particles often hide in background noise. 
  • To pull them out, the researchers built a computer workflow called Duplicated Selection To Exclude Rubbish (DuSTER). 
  • Two-Step Validation: The DuSTER algorithm picked each particle twice, kept those that landed in the same place after two rounds of 2D or 3D classification, and threw the rest away.
  • Even when cryo-electron microscope (cryo-EM) images are full of noise and look unusable, the DuSTER software is able to identify and extract the useful, high-quality particle images from them.

Significance of MagIC

• Scientific Advancement: Allows structural study of rare, low-concentration biomolecules.
• Sample Efficiency: Lowers the sample demand to just 5 nanograms per grid
• Data Quality: Combines magnetic targeting with computer filtering for improved accuracy.
• Speed: The scientists can quickly move the microscope to regions rich in particles, speeding up data collection.

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