Synchrotron IR Tracks Phosphorylation

Infrared radiation from a synchrotron light source has illuminated protein phosphorylation as single cells develop into nerve cells (Anal. Chem., DOI: 10.1021/ac300308x). Existing techniques for studying this process require researchers to put chemical tags on proteins of interest. IR spectroscopy can measure phosphorylation without labeling, but most instruments don’t use light bright enough to detect the weak signals from single cells. Hoi-Ying N. Holman of Lawrence Berkeley National Laboratory and her colleagues used a synchrotron IR method, which provides up to 1,000 times better signal-to-noise ratio than a standard IR instrument, to watch what happens inside individual rat cells as they differentiated into nerve cells. Previous studies have shown that phosphorylation increases during this transition. Holman’s team triggered differentiation in cell culture and then focused the light beam on one cell at a time, collecting data at set times over seven days. Holman was surprised at how quickly phosphorylation levels changed: Levels spiked in just five minutes, she says, then came in waves correlating with the stages of differentiation. Since IR spectroscopy can track many types of molecules, Holman plans to try monitoring other chemical transformations, such as methylation or changes in carbohydrate composition.