COLUMBUS , Ohio -- No one has ever seen exactly how water molecules interact with proteins even though water is the essential element for life . . . that is, not until now.
Researchers led by Ohio State University physicist Dongping Zhong revealed these interactions for the first time, and report the results in the current issue of the Proceedings of the National Academy of Sciences.
Proteins are complex molecules that form the main support structure for plant and animal cells, and they also regulate biochemical reactions.
Zhong's project aims eventually to explain how water helps enable life-supporting biological functions such as protein folding or enzyme catalysis. But for now, this early result ends decades of controversy on what happens in the microscopic realm where water and proteins meet.
The controversy, Zhong explained, stemmed from the fact that researchers across different disciplines used different methods to study the problem. Because of that, they got different answers on the speed with which these essential biochemical reactions take place.
"A biologist will tell you that water and proteins must interact on a nanosecond [one billionth of a second] time scale, because that's how fast proteins move," he said. "And a physicist will tell you that the interaction would happen much faster -- on the picosecond [one trillionth of a second] time scale -- because that's how fast water molecules move. And someone who uses X-rays will give you a different answer than someone who uses nuclear magnetic resonance and so on."
"My feeling is that there is no real controversy -- everybody is just looking at the same answer from different angles," he added.
The answer, revealed in Zhong's lab: water molecules do move fast on their own, but they slow down -- to a speed midway between the nanosecond and picosecond scale -- to connect with proteins.