Question

Explain how you could determine if alpha or beta d-ribose would be produced by the N-methyl nucleotides catalyzed reaction of 7-methylxanthosine to 7-methylxanthine.

Answer 1

Ans is HPLC

Classical methods for the determination of sugar anomers are based on the measurement of the specific rotation and nuclear magnetic resonance (NMR) (Angyal, 1968; Angyal & Dawes, 1968; Angyal, 1984, Angyal, 1991), but the NMR is expensive and difficult to work with. Moreover polarimetry is a non-specific method and the proportion of the furanose forms cannot be determined in this way. Anomers may be also analysed by gas chromatography.The chromatographic system consisted of Shimadzu LC9A pump, rheodyne injector with a 20 ~1 loop, a Shimadzu RID-6A differential refractometric detector and a Shimadzu C-R4AX integrator. The analytical column (200 x 4.0 mm I.D.) used throughout was packed with 5 pm particle diameter P-cyclodextrin bonded silica gel.Methanol/water and acetonitrile/water mixtures are not suitable for the separation of the anomers. However the use of the relatively non-polar ethyl acetate at a concentration of about 70% results in a separation of the anomeric forms of D-glucose. Retention time and spreading of the HPLC peaks increase with ethyl acetate concentration.