Scholars and scientists gathered in the Srinivasa Auditorium at Sri Venkateshwara University, Tirupati on Tuesday afternoon at the 104th Indian Science congress 2017. They were here to listen to Professor W. Moerner who shared the Nobel Prize for chemistry in 2014 for his discovery of single molecule fluorescence microscopy.
His lecture entitled- Science and Single Molecules, was a story of physical chemistry, ultrasensitive detection, and industrial basic research having unexpected effects. He ventured into a field that once seemed mission impossible- detecting and viewing single molecules of the size of a few nanometers- many folds smaller than the thickness of a human hair. His research had begun at IBM, San Jose, California in early 1980s where he could measure the optical absorbance of single molecules.
The first question that boggles our mind is as to why should one measure a single molecule in the first place, why is it so important? Professor Moerner comes to our rescue and elaborates it with an analogy. He refers to it as the “Baseball analogy”. While the overall batting score of a baseball team may be very good, there could be players in the team who do not bat at all; they could just be good bowlers. Similarly, in the absence of super resolution imaging we observe an overall or ensemble effect of all the molecules; the behavior or dynamics of individual molecules could be totally different. Hence, super resolution imaging could be of immense importance in studying single molecules like DNA.
It is known since long that a molecule exhibits Brownian or random zigzag motion in space, in other words, it resonates. With some colorful visuals, he shows us that molecules at low or room temperatures move in and out of resonance dynamically. A dramatic improvement in super resolution imaging came by coupling this technology with fluorescent molecules. These molecules absorb or get excited by light of one wavelength and emit another wavelength that enables their detection in the colored spectrum of light. You can view fluorescent molecules as yellow, or green under an optical microscope. This could help detect dynamic movement of molecules in living cells, their localization and even interaction with other molecules.
Improvements in imaging single molecules also came with studies on yellow fluorescent protein where the molecules seem to blink at room temperature. This happens because the molecules go into a different dark state that resumes to fluorescence when the molecule is exposed to blue light. This provides for what he calls, active control of emitting concentration where not all the molecules in a living cell will emit fluorescence. We could turn on the fluorescence of some molecules via a switch and turn them off too. Images from two such time points could be combined to achieve super resolution.
The other strategy spreads a single image over many pixels during acquisition and then combines data from individual pixels to reconstruct a high-resolution image. The two methods combined together enable images that have at least five orders of improved resolution and helps biologists and chemists fetch deeper understanding of cell biology and materials sciences.
On a lighter note, Professor W. Moerner also tells us a method to predict Nobel Prize winners. He directs audience’s attention to a cartoon of Homer Simpson from the famous TV show “The Simpsons” where the family members have listed their bets for the next Nobel Prize. “For you to have a Nobel, you must be picked up by Millhouse, the Simpsons”, he jokes.
He talks about how his discovery has caused a paradigm shift in microscopy that provided blurry images due to constrained resolution earlier. Conventional microscopy required high sensitivity, specificity, spatial resolution, and the ease of working in living cells- all of which can now be achieved with single cell super resolution microscopy!
No comments:
Post a Comment