Storing proteins can be a difficult process. They are prone to breaking down when you take them out of their native environments, which calls for measures to preserve them. However, proteins vary in behavior. The storage method that works for one protein will not necessarily work for another.
The shelf life of a protein varies based on the protein itself and the condition in which you store it. Each protein will have its own optimal storage process, which can also vary depending on the length of time you need to store it. There are some basic guidelines for protein storage you can follow for accurate protein analysis techniques.
Temperature Ranges
Lowering the temperature is the best and most common method of storing proteins. The temperature you choose for storage will depend on the characteristics of the protein itself, and how long you wish to keep the protein stored. The longer you need to store it, the colder the optimal temperature.
- If you only need to store your proteins for 24 hours or less, you can generally keep your proteins at 4° Celsius. This way, the water will not freeze, and you can use the samples with a minimum of preparation.
- If you wish to store proteins for longer than 24 hours, but do not wish to freeze them, you will need to add a chemical agent to prevent bacterial growth. However, not all proteins can remain stable at 4° Celsius for long periods. Depending on the protein, you may need to freeze them for longer storage times.
- If you want to store proteins for more than a week, you will have to freeze them. Freeze them quickly to avoid denaturation of the protein. You will need to add some other agents as well.
- If your storage is going to last for several months, you will need to take the temperature down to -20° Celsius.
Additives
Additives will usually be necessary to stabilize your stored proteins. If you are freezing the proteins but not drying them, the ice crystals that form will harm the proteins. Adding up to 50% glycerol will keep the solution from freezing and therefore protect the integrity of the proteins. Protease inhibitors will prevent the cleaving of the protein and anti-microbial agents will keep the batch sterilized.
Lyophilization
Lyophilization is also known as freeze-drying. This is the most effective method of protein storage. Generally, researchers freeze the sample while removing the water from it. They can do this by introducing the sample into a frozen container and generating a vacuum. In the vacuum, the water sublimates or changes states from solid to gas. The gas then crystallizes on the walls of the chamber and the proteins remain, desiccated.
Though it is a sound method of storage, researchers will need to reconstitute freeze-dried proteins when it comes time to thaw them. This process of reintroducing water into the proteins can damage them. Sometimes researchers prefer simply to freeze the samples for this reason.
Improper protein storage can ruin months of work. Though the process of protein storage can be delicate, there are basic guidelines that can help you. When it comes time to store an actual protein, you will need to know the guidelines for that specific protein for best results.
SOURCES:
- https://www.biocompare.com/Bench-Tips/180878-Keeping-Your-Cool-When-Storing-Purified-Protein/
- https://www.embl.de/pepcore/pepcore_services/protein_purification/storage_purified_proteins/
- http://wolfson.huji.ac.il/purification/PDF/StorageProteins/PIERCE_ProteinStorage.pdf
- http://elte.prompt.hu/sites/default/files/tananyagok/IntroductionToPracticalBiochemistry/ch01s11.html
