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NTHU Research Team Explores the World of Water at Low Temperatures
If intergalactic travel by a manned spacecraft ever becomes possible, it will take hundreds of years to reach another galaxy. In light of the average human life span at present, such an undertaking will thus require the use of cryonics—freezing a living body and later reviving it. One of the major hurdles facing the development of cryonics is that frozen cells can’t fully recover their original functions. However, Prof. Chiang Yun-wei of the Department of Chemistry has used a technique known as saturation-transfer electron spin resonance (ST-ESR) to verify that there are two different liquid phases at a temperature of -93°C, constituting a major advance in the field of cryonics.
 
Together with his doctoral student Kuo Yun-hsuan, Chiang has presented his findings in a paper titled, "Slow Dynamics around a Protein and Its Coupling to Solvent," in which they unveil the mystery surrounding the interaction between water and protein. It was previously believed that water invariably controls the movement of proteins, but their study demonstrates that this is not always the case. Their paper recently appeared in the American journal ACS Central Science, and is the first full-length paper by Taiwanese researchers ever published by the journal. Their breakthrough was featured on the journal’s website under the headline "Water ‘Slaves’ Protein Motions?"
 
The Highly Complex Behavior of Simple Water Molecules
 
Water is the most important element of living organisms. All who has a grade school education knows that water exists in three different states, and most people know the boiling point and freezing point of water. But for Prof. Chiang water is anything but simple. As he puts it, "water molecules are extremely simple, but their behavior is highly complex!" For example, most people believe that there is only one kind of ice, when in fact researcher has so far identified 21 different kinds of ice crystals, and its derived thermodynamic phase diagram is unexpectedly rich and brilliant. There are still many unknowns, and the behavior of water is an important field of contemporary physical chemistry research.
 
There is only one ST-ESR system in Taiwan, costing more than NT$40 million, and by using it to measure the movement of water molecules at low temperatures Chiang’s research team has observed that a "liquid-liquid critical phenomenon" occurs at temperatures between -33°C to -93°C.
 
They also found that at temperatures below -13°C, an aqueous solution containing trace amounts of glycerin enters "liquid state one," and that at -83°C it enters "liquid state two," both of which are quite stable. However, their densities and forms of movement are different, which seems counterintuitive, since both states are liquids consisting of the same elements, yet at low temperatures these elements separate from each other and remain on the surface of the protein. Chiang explains that as soon as fruit is frozen at a low temperature the cells swell, making freezing a rather ineffective means of preservation, since it tends to cause protein damage. If one day it becomes possible for spacecraft to travel to distant galaxies over the course of many light years, any humans on board will have to be placed in a state of suspended animation using cryonic technology, which currently exists only in sci-fi novels, but Chiang’s research team has made a big step towards making it a reality.
 
Emancipated Protein Dynamics
 
Chiang’s research helps to unlock the mystery of the interaction between water and protein. It is well known that proteins must have water to function, but is water just a foil to protein? Or does it act more like a guide? This topic has been hotly debated in the scientific community for more than 20 years.
 
Chiang says that because the interaction between protein and water molecules is highly persistent and dense, it is quite difficult to clarify exactly how it works. Many researchers have attempted to do so by using low temperatures to slow down the molecular movements. Chiang's research team has also adopted this approach, but has also used ST-ESR, which has made it possible to observe slow-scale motion that had never been seen before.
 
Next, the team used site-directed mutagenesis to regulate the length of the protein side chains and to change the physical properties of their single side chains. This made it possible to clearly discern the individual movements of the protein and water molecules and to verify that many protein elements can indeed be emancipated from the control of water molecules, thereby overturning the widespread belief that water invariably dominates the movement of protein.
 
Chiang points out that the movement of protein molecules is so complex that even with the most advanced supercomputers, it is still impossible to simulate every detail of their movement. From a mathematical point of view, his study proposes 5 to 10 basic movement elements of protein. They also observed the side chain motions (large movement) of protein at a low temperature, rotamer jumps between groups (medium movement), and structural fluctuations (small movement).
 
Chiang illustrates this with the example of building a skyscraper. In contrast to an ordinary brick wall, a skyscraper requires a steel frame, the floors and walls are finished with concrete. Chiang has found that basic dynamic elements of protein are a lot like that steel frame. And observing these basic dynamic elements of protein can help scientists to better understand how proteins use these movements to change their structure and function and how they work within cells.
 
Explorations at -93℃
 
Kuo graduated from NTHU last year and is the first author of this paper. He is currently completing his alternative military service and preparing to go abroad for postdoctoral research. Chiang says that he has been very impressed by Kuo’s enthusiasm and persistence, and that he is one of only a handful of people in the world proficient in ST-ESR technology.
 
Chiang is currently planning to continue using ST-ESR technology to explore the interaction between proteins and water molecules at even lower temperatures. As he puts it, "There’s still a lot learn at temperatures below -93°C!"
 

Prof. Chiang Yun-wei of the Department of Chemistry and his research team.

Prof. Chiang Yun-wei of the Department of Chemistry and his research team.



Chiang’s breakthrough research was featured on the homepage of the ACS Central Science website.

Chiang’s breakthrough research was featured on the homepage of the ACS Central Science website.

Chiang specializes in the study of water molecules.

Chiang specializes in the study of water molecules.

 

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