Nucleotide head group

Fibers were also found to be formed, amongst others, by amphiphile s like 99 having a phospholipid nucleotide head group [50], by porphyrin derivatives like 100 [51], and by helicene derivative 101 [52]. 

In mid-1997 an international conference took place in Santa Cruz, USA, in which, for the first time, the exclusive topic was structural aspects of RNA molecules. A report covering this meeting contains an impressive graphic which shows the RNA structures, RNA/DNA complexes, and RNA/protein complexes contained in the brookhaven database as a function of the year of their publication [29]. Between 1988 and 1993 there were just 20. However, in 1996 alone no less than 41 structures appeared. These new dimensions were headed by the crystal structural elucidation of the first larger RNA molecule since the first crystal structure of tRNA in 1973 [30], the 48 nucleotide long hammerhead ribo-zyme (HHR) [31-33]. This landmark achievement was followed by a crystal structure analysis of the P4-P6-domain of a group I intron [34-36] and, more recently, a crystal structure of the hepatitis delta virus ribozyme [37]. 

P2j Z = 2 Dx = 1.536 R = 0.065 for 1,387 intensities. The conformation of the D-ribosyl group is 2Ti (153°), the glycosyl disposition is syn (—110°), and the exocyclic C-4 -C-5 bond torsion-angle is 62°. The nucleotides are stacked in head-to-tail fashion involving the pyrimidine rings, and the sulfur atom lies over the imidazole ring. 

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