According to a new study, researchers have found a new way to see and measure protein assembly in real time and with unprecedented detail. This is revealed by using a new mode of atomic force microscopy, Proteins and molecules assemble and disassemble naturally as part of many essential biological processes. It is very difficult to observe these mechanisms, which are often complex and take place at the nanometer scale, far smaller than the normal visible range. The study was published in Nature Nanotechnology.
Researchers invented and applied a technique that allows these mechanisms to be examined with unprecedented precision. Nanometric structures can only be seen with specialty microscopes, such as atomic force microscopes, which were invented in the mid-1980s. These instruments create an image by physically "feeling" the topography of the sample with an atomically sharp tip at the end of a tiny cantilever.
The sample is then scanned point by point to create an image. As this takes time, only static samples can be imaged with conventional atomic force microscopes. However, this is of no use when scientists want to look at minute samples that change over time, such as protein assemblies.
To observe processes on a sample that changes over time, the scanning speed has to be increased. However, in traditional fast atomic microscopes, the forces exerted by the measurement can interfere with the molecular assembly process, especially since protein assemblies are often very fragile.
The EPFL researchers found a method that solved the problem, by controlling the physical interaction of the sharp tip very precisely using pulsed laser light. This dramatically increased the scanning speed while preserving the gentle but extremely precise scanning motion.
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The researchers tested this new technology to analyze the dynamics of SAS-6 protein ring formation. This protein family plays a key role in the assembly of centrioles, which are minute organelles conserved from algae to men, fundamental for cell motility and division. The new instrument allowed the researchers for the first time to visualize the various stages of the ring assembly of SAS-6 proteins in real time.
Now they finally have a method to directly observe how this critical cellular component is assembled into a ring like a polymer. This research is the result of a collaboration between two EPFL entities: the Laboratory for Bio- and Nano- Instrumentation (LBNI) and Professor Pierre Gönczy's Laboratory within the Swiss Institute for Experimental Cancer Research (ISREC) in the School of Life Sciences.