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Live cell biology is challenging. Samples that are fluorescently labeled can be altered. Research in real time—in drug detection, for example—is necessary, but difficult. A major problem in imaging is, how do you see what’s there that may not be visible under standard microscopy without changing it? It is amazing to be able to see single molecules in real time. But science is based on measurements and early cameras were not able to capture them.
One solution is electron multiplying (EMCCD) cameras which enable researchers to detect things in a more realistic and native form in live cell research, says Dr. Deepak Sharma, Senior Product Manager of Photometrics (Tucson, Ariz.). “And if you did use alternative detection methods, they weren’t as efficient at gathering the light. You didn’t have the same dynamic range, which means you couldn’t see bright things and dim things at the same time. So the previous technologies had all these little negative aspects to them, which electron multiplying technology overcomes and provides the researcher a way to detect things and see things which were hard to see before.”
The EMCCD works similarly to a standard CCD, where incoming photons generate photoelectrons, which then are shifted through the pixels. Each pixel is sequentially measured as it is read out. In that reading-out process, however, there’s an uncertainty—noise. “What happens with really low light level signals is that you have this read noise, which actually is higher than the signal itself, so all of a sudden you’re not able to detect a signal because the actual noise is higher,” Sharma says. “It would be like watching white noise on a screen, or just a gray background in the camera. It happens in live cell biology
and microscopy, especially because people are looking at tiny samples…and live cells, often with things like green fluorescent proteins inside the cell that emit light.”
To compensate, scientists would often add more of the green fluorescent probe into the cell, but too much changes the nature of the experiment. The key is to put very little in and see what actually happens to the cells.