1c4l: Difference between revisions

[[Image:1c4l.gif|left|200px]]

'''SOLUTION STRUCTURE OF AN RNA DUPLEX INCLUDING A C-U BASE-PAIR'''

The formation of the C-U base pair in a duplex was observed in solution by means of the temperature profile of (15)N chemical shifts, and the precise geometry of the C-U base pair was also determined by NOE-based structure calculation. From the solution structure of the RNA oligomer, r[CGACUCAGG].r[CCUGCGUCG], it was found that a single C-U mismatch preferred being stacked in the duplex rather than being flipped-out even in solution. Moreover, it adopts an irregular geometry, where the amino nitrogen (N4) of the cytidine and keto-oxygen (O4) of the uridine are within hydrogen-bonding distance, as seen in crystals. To further prove the presence of a hydrogen bond in the C-U pair, we employed a point-labeled cytidine at the exocyclic amino nitrogen of the cytidine in the C-U pair. The temperature profile of its (15)N chemical shift showed a sigmoidal transition curve, indicating the presence of a hydrogen bond in the C-U pair in the duplex.

Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1C4L OCA].  

''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May  2 12:19:17 2008''