Inactivity of proteins behind longer shelf life when freezing

Frozen biological material, for example food, can be kept for a long time without perishing.

A study by researchers at the University of Gothenburg, Sweden, is close to providing answers as to why.

A cell's proteins are programmed to carry out various biological functions. The protein's level of activity and its ability to successfully carry out these functions is dependent on the amount of water by which it is surrounded. For example, dry proteins are completely inactive. A critical amount of water is required in order for the function to get going, after which point the protein's level of activity increases concurrently with an increase in the amount of water. Proteins achieve full biological activity when the surrounding water has approximately the same weight as the protein.

Researchers at the University of Gothenburg and Chalmers University of Technology have together with a group of American researchers used advanced experimental techniques to study how movements in the water that surrounds the protein cause movements in the protein itself. The study, which is being published in the journal PNAS, indicates that the dynamics in the surrounding water have a direct effect on the protein's dynamics, which, in turn, should affect the activity.

The results explain, for example, why biological material such as foodstuffs or research material can be stored at low temperatures for a long period of time without perishing.

"When the global movements in the surrounding water freeze, then significant movements within the protein also come to a stop. This results in the protein being preserved in a state of minimum energy and biological activity comes to a stop," says researcher Helén Jansson at the Swedish NMR Centre, University of Gothenburg, Sweden.