Think of looking at cells in vitro (the biologists way of saying the cells are in a Petri dish or a test tube – ‘in glass’) as watching animals in a zoo. It looks relatively natural, but it isn’t. There could be differences, perhaps important differences between the way a cell behaves in vitro and what it does in vivo (in life, or as biologists sometimes say, ‘in the wild’). These differences may also exist for the behavior of proteins within cells – their constant folding and unfolding – but until recently, nobody had seen this activity in vivo. It required some new methods by a team of scientists at the University of Illinois (USA).

To be able to see the protein folding in a live cell, they used a process that they called ‘Fast Relaxation Imaging.’ This combined fluorescence microscopy, a specially designed microscope that uses ultraviolet light (UV) to make prepared fluorescent molecules glow and visually easy to see; and programmed laser pulses to rapidly heat, stabilize, then cool a cell while it is being observed (usually video recorded). This happens in a span of a few milliseconds, in an instant a cell is warmed – like a mild fever – to accelerate the activity of proteins, which are fluorescing (usually one color) and easy to follow.

As the corresponding author of the paper, Martin Gruebele (James R. Eiszner Professor of Chemistry, University of Illinois) explains it:

“We haven’t really been able to study dynamics, to see if a chemical reaction like protein folding varies inside of a living cell,” he said. “With temperature jumps and pressure jumps, you can do those experiments very quickly, but you don’t get any imagery that lets you see if proteins fold faster in one region and slower in another,” Gruebele said.

On the other hand, fluorescence microscopy allows researchers to see inside of cells, but it precludes them from studying cell dynamics and kinetics.

“With fluorescence microscopy, we’re able to take images of cells and see inside them, but we can’t observe how anything rapidly changes or adapts with time, so you can’t look at any but the slowest dynamics. This experiment puts those two aspects together,” he said.

[Source: EurekAlert]

Looking at the protein activity inside a living cell added at least one new dimension to the studies – time. The researcher’s could observe the folding and unfolding of proteins over time (not as in the usual ‘snapshot’ of time). They discovered that the processes were slower in vivo than they are in vitro. In short, they were more stable than thought and there wasn’t a lot of difference in the rate of activity in different parts of the cell. They speculated that within the confines of a living cell, there are a lot of cell components (‘furniture’) in the way of protein movement, which slows them down.

By adding the dimension of time to the study of protein configuration, the scientists hope to observe the processes of diseased proteins – for example, the prions and proteins associated with Alzheimer’s or Creutzfeld-Jakob disease. They hope to be able to spot behavior that differentiates normal from diseased proteins.

As is ever the hope, more knowledge about the pathways and processes may lead to treatments.