Tautomer, purine

Fig. 5. Computed polarization directions of the longest 77—77- absorption band in the four purine tautomers.

Dipole Moments (Debye Units) in Purine Tautomers... 

Fig. 6. Relative magnitudes and the directions of the dipole moments in the four purine tautomers (PPPCI method).

Fig. 7. Net electronic charges in purine tautomers evaluated by the CNDO/2 method. Upper numbers a charges lower numbers tt charges.

The investigation of the chemical and physicochemical properties of purine tautomers, as well as their possible biological role, is still in a primitive form. Further developments are desirable and may have far reaching consequences for our understanding of the mechanism of life processes. 

Calculated NMR shifts can be used to explore the composition of a fast-exchange system (tautomerism, protonation). The theoretically calculated NMR chemical shifts of the N -H and N -H purine tautomers have been used to analyze the experimentally observed chemical shifts and to calculate the tautomeric ratio. ... 

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