Berkeley Lab scientists observed phosphorylation in living PC12 cells stimulated by nerve growth factor as they differentiated and sent out neuron-like neurites. The researchers imaged individual cells and simultaneously obtained absorption spectra using synchrotron radiation from the Advanced Light Source. Cells not stimulated with nerve growth factor did not differentiate and showed different infrared absorption spectra.
Knowing how a living cell works means knowing how the chemistry inside the cell changes as the functions of the cell change. Protein phosphorylation, for example, controls everything from cell proliferation to differentiation to metabolism to signaling, and even programmed cell death (apoptosis), in cells from bacteria to humans. It’s a chemical process that has long been intensively studied, not least in hopes of treating or eliminating a wide range of diseases. But until now the close-up view – watching phosphorylation work at the molecular level as individual cells change over time – has been impossible without damaging the cells or interfering with the very processes that are being examined.
“To look into phosphorylation, researchers have labeled specific phosphorylated proteins with antibodies that carry fluorescent dyes,” says Hoi-Ying Holman of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). “That gives you a great image, but you have to know exactly what to label before you can even begin.”
Holman and her coworkers worked with colleagues from the San Diego and Berkeley campuses of the University of California to develop a new technique for monitoring protein phosphorylation inside single living cells, tracking them over a week’s time as they underwent a series of major changes.
“Now we can follow cellular chemical changes without preconceived notions of what they might be,” says Holman, a pioneer in infrared (IR) studies of living cells who is director of the Berkeley Synchrotron Infrared Structural Biology program at Berkeley Lab’s Advanced Light Source (ALS) and head of the Chemical Ecology Research group in the Earth Sciences Division . “We’ve monitored unlabeled living cells by studying the nonperturbing absorption of a wide spectrum of bright synchrotron infrared radiation from the ALS.”
The researchers report their results in the American Chemical Society journal Analytical Chemistry.
Most analytical techniques can provide a snapshot of the average behavior of a group of cells. For example, scientists grind cells and measure levels of gene transcripts to monitor how cellular circuits turn on and off, or they use mass spectrometry to identify natural products in a bacterial colony. But these average snapshots can miss rare cells—those few that behave differently from the rest, according to Hoi-Ying N. Holman, a staff scientist at Lawrence Berkeley National Laboratory (LBNL). Details about these cells often fail to rise above the noise of the majority, but studying them could help researchers understand how cells respond differently to changes in their environment.
Now, spectroscopists can break through that noise, focus on the unique cell, and study it in real time by using a technique that combines conventional infrared spectroscopy with the extraordinarily bright light produced by a synchrotron—best known as a source of X-rays for crystallography. At last month’s 6th International Chemical Congress of Pacific Basin Societies, or Pacifichem, held in Honolulu, Holman and others described what they are learning from the method, as well as recent advances that are expanding the technique’s usefulness.
“We’re finding that when you zoom down to individual cells, they actually respond differently,” said Michael Martin, a staff scientist at LBNL’s Advanced Light Source.
Two Berkeley Lab researchers received this year’s Presidential Early Career Award for Scientists and Engineers (PECASE): Christian Bauer (not shown, Physics Division) and Feng Wang of the Materials Sciences Division. Wang is an ALS user on Beamline 1.4 (see ALS Science Highlight Bilayer Graphene Gets a Bandgap and this month's Berkeley Lab News Center article A Whole New Light on Graphene Metamaterials). Wang is cited for “pioneering research on ultrafast optical characterization of carbon nanostructures that has advanced the fundamental understanding of the electronic structure of graphene and is expected to enable the development of advanced-energy-relevant technologies.” PECASE awards are the U.S. government’s highest honors to outstanding scientists and engineers, early in their independent research careers.
IR Spectrum Song
Help figure out what your IR spectrum means with the Infrared Spectrum Song!
Two Berkeley Lab researchers received this year’s Presidential Early Career Award for Scientists and Engineers (PECASE): Christian Bauer (not shown, Physics Division) and Feng Wang of the Materials Sciences Division. Wang is an ALS user on Beamline 1.4 (see ALS Science Highlight 
