Most protein molecules today can only function within a limited temperature range, generally close to ambient temperature or body temperature. What is very exciting about the research in this area is that a new class of compound has been discovered in association with proteins. Specifically, they are somehow able to recognise damaged protein and to repair it. Chaperones were discovered during work with loss of protein function in Escherichia coli bacteria. E. Coli are generally harmless bacteria, which are found in the colon of humans and some other mammals and are used extensively in microbiology research.
Chaperones are themselves protein molecules and have a cylindrical shape.
What is particularly interesting is that they can somehow recognise when a protein is incorrectly folded and are able to correct this. This might explain how proteins that are structurally damaged at high temperatures can be repaired and remain functional. It has been proposed that the Archaea form a third domain of organisms together with bacteria and eukaryotes. Some ribosomal RNA sequences, or more precisely, the DNA gene sequences that code for the rRNA, are universally present in all organisms. For this reason they are the most commonly used molecules for this kind of species comparison, and are considered to give the best measure of evolutionary differentiation.