Tloop

Tloop, often written as T-loop, is a term used in several disciplines, without a single universally accepted meaning. In molecular biology it is most commonly associated with a structural feature of transfer RNA. In other fields, the term can be used informally to denote a time-domain or feedback loop characterized by a period or time constant T, or simply as a label in software, branding, or literature. Because usage varies by context, the term does not have a standardized definition.

In biology, the T loop, or TψC loop, is a conserved region of tRNA located in the T arm of the cloverleaf secondary structure. It contains the TψC motif, reflecting the presence of thymidine or uridine (T/U), pseudouridine (ψ), and cytidine (C). The loop contributes to the stabilization of the tRNA’s three-dimensional L-shaped fold and participates in interactions with ribosomal RNA during translation. Modifications within the loop can influence tRNA stability, proper folding, and ribosome binding, thereby affecting translation efficiency and accuracy.

Beyond biology, the term T-loop appears in some engineering and computer science texts as an informal reference to a timing or test loop with a characteristic period or time constant T. This usage is not standardized and may vary between authors or projects. Consequently, clear definition usually requires specification of the domain and context.

See also: tRNA, TψC loop.