Internal loop
Internal-loops in RNA are found where the double stranded RNA separates due to no Watson-Crick base pairing between the nucleotides. Internal-loops differ from Stem-loops as they occur in middle of a stretch of double stranded RNA. The non-canonicoal residues result in the double helix becoming distorted due to unwinding, unstacking and kinking.
Internal-loops can be classified as either symmetrical or asymmetrical, with some asymmetrical internal-loops, also known as bulges. Many important structural motifs are composed of internal loops such as
the C-loop,
the docking-elbow,
kink-turns,
the right-angle,
the sarcin/ricin loops,
the twist-up motif
and the UAA/GAN internal loop motif.
