id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-349839-s32d3di2	Westhof, Eric	RNA pseudoknots	1992-06-30		.txt	text/plain	3427	185	59	In the folding of a single-stranded RNA molecule, there are only three ways in which two base-paired segments can be related to each other: two consecutive hairpins; two helices separated by an internal bulge; and, pseudoknots [1]. The first two motifs can be represented as two-dimensional graphs without self-intersections whereas pseudoknots cannot, as they are fundamentally three-dimensional structures in which the four base-paired strands alternate along the sequence of the RNA molecule. The three types of 'classic' pseudoknots with co-axial stacking of the two base-paired helices and with single-stranded segments crossing the RNA grooves. The third pseudoknot involves the 530 stem-loop structure [19] , which is known to be important for the binding of tRNA to the ribosomal A site [20] , and was recently shown to be essential for ribosomal function [21.o] .	./cache/cord-349839-s32d3di2.txt	./txt/cord-349839-s32d3di2.txt