Exposing living tissue to subfreezing tempera...

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Exposing living tissue to subfreezing temperatures for long can cause permanent damage. Microscopic ice crystals (结晶体) cut cells and seize moisture (潮气), making donor organs unsuitable for transplantation. Thus, organs can be made cold for only a few hours ahead of a procedure. But a set of lasting new antifreeze compounds (化合物)—similar to those found in particularly hardy (耐寒的) animals—could lengthen organs’ shelf life.

Scientists at the University of Warwick in England were inspired by proteins in some species of Arctic fish, wood frogs and other organisms that prevent blood from freezing, allowing them to flourish in extreme cold. Previous research had shown these natural antifreeze molecules (分子) could preserve rat hearts at -1.3 degrees Celsius for up to 24 hours. But these proteins are expensive to extract (提取) and highly poisonous to some species. “For a long time everyone assumed you had to make synthetic (人造的) alternatives that looked exactly like antifreeze proteins to solve this problem, ”says Matthew Gibson, a chemist at Warwick who co-authored the new research. “But we found that you can design new molecules that function like antifreeze proteins but do not necessarily look like them. ”

Most natural antifreeze molecules have a mixture of regions that either attract or repel water. Scientists do not know exactly how this process prevents ice crystal formation, but Gibson thinks it might throw water molecules into push-pull chaos that prevents them from tuning into ice. To copy this mechanism, he and his colleagues synthesized spiral-shaped molecules that were mostly water-repellent—but had iron atoms at their centers that made them hydrophilic, or water-loving. The resulting compounds were surprisingly effective at stopping ice crystals from forming. Some were also harmless to the roundworm Caenorhabditis elegans, indicating they might be safe for other animals.

“These compounds are really cool because they are not proteins—they are other types of molecules that nonetheless can do at least part of what natural antifreeze proteins do, ”says Clara do Amaral, a biologist at Mount St. Joseph University, who was not involved in the research. Gibson’s antifreeze compounds will still need to be tested in humans, however, and may be only part of a solution. “We don’t have the whole picture yet, ”do Amaral adds. “It’s not just one magical compound that helps freeze-tolerant organisms survive. It’s a whole suite of adaptations.

1.What will happen if organs are kept for a long time in temperatures below zero?

A.They will have ice crystal formation inside.

B.They will not suffer permanent damage.

C.They will have longer shelf life.

D.They will be fit for transplantation.

2.What can we learn about natural antifreeze proteins?

A.They look like Gibson’s antifreeze compounds.

B.They are composed of antifreeze molecules harmless to other species.

C.They are spiral-shaped and have iron atoms at their centers.

D.They can be found in organisms living in freezing cold weather.

3.How are antifreeze molecules prevented from ice crystals?

A.By creating compounds both water-repellent and water-loving.

B.By extracting the proteins from some hardy animals.

C.By making synthetic alternatives like antifreeze proteins.

D.By copying spiral-shaped molecules mostly water-resistant.

4.What’s the main idea of the passage?

A.Push-pull chaos might prevent water molecules from turning into ice.

B.The final solution to preserving donor organs has been found recently.

C.Chemicals inspired by Arctic animals could lengthen organs’ shelf life.

D.Gibson’s antifreeze compounds can do what natural antifreeze proteins do.

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