A study in this week's Proceedings of the National Academy of Sciences provides the strongest evidence yet that proteins--the large and complex molecules that fold into particular shapes to enable biological reactions--can't fold themselves.
"We believe we now have strong direct evidence that on ultrafast time scales (picoseconds, or trillionths of a second), water modulates protein fluctuations,"
Water molecules typically flow around each other at picosecond speeds, while proteins fold at nanosecond speeds--1,000 times slower. .. water molecules slow down when they encounter a protein. Water molecules are still moving 100 times faster than a protein when they connect with it, however.
In the new study, the researchers were able to determine that the water molecules directly touched the protein's "side chains," the portions of the protein molecule that bind and unbind with each other to enable folding and function. The researchers were also able to note the timing of movement in the molecules.
"Here, we've shown that the final shape of a protein depends on two things: water and the amino acids themselves. We can now say that, on ultrafast time scales, the protein surface fluctuations are controlled by water fluctuations. Water molecules work together like a big network to drive the movement of proteins."