Transfer RNAs, which are RNAs that participate in translation, contain the greatest number of modifications of any type of RNA, with up to one-fourth of the nucleosides in these molecules containing some sort of modification in eukaryotes. There are several known reasons for the wide variety of modifications found in tRNA. First of all, such modifications allow for easier differentiation between different tRNA molecules, such as separating the initiator tRNA from elongator tRNA. Moreover, they increase overall tRNA stability. Some studies have shown that the modifications of tRNA can be dynamic and adaptive to the changes of the environment. Examples include methylation of cytosine groups by tRNA methyltransferase (Trm4) in response to the depletion of nutrients in the body. The tRNA's cruciform structure is incredibly important to its overall function and such a complicated structure is maintained by post-transcriptional modifications. A primary example of this is the methylation of guanosine at junctions within the tRNA structure. These methylguanosine impact the overall tertiary structure by disrupting any potential canonical hydrogen bonding (hydrogen bonds that are conventional Watson-Crick base pairs), thus creating a loop at the core of the tRNA. Other modifications are integral for creating and maintaining the extreme bends in the structure.