Dinucleoside monophosphate complexes

Receptor models 71a and 71b for dinucleotides (dinucleoside monophosphates) have been developed out of 69 by replacing the naphthoyl residue, which is not involved in any host-guest interactions in the complexes, by a second carbazolyl cleft. The adenine selectivity of the two pincers was reflected in single extraction experiments dissolved in CH2CI2,71a removes one full equivalent of both adenylyl(3 -+ 5 )adenosine (ApA) and 2 -deoxyadenylyl(3 ->5 )-2 -deoxyadenosine [d(ApA)] 72 out of aqueous solutions of guest (8-fold excess) but only half the amount of d(ApG) [103]. 

Figure 2. Stereoscopic illustration of the ethidium/dinucleoside monophosphate (CpG) crystalline complex (18) in the stick model mode. There are 130 atoms in...

The gg conformation about the P—O bonds is as stated above the one predicted as the most stable for the free molecules of the type of dimethylphosphate or disugar phosphate or dinucleoside monophosphate or the polar head of phospholipids by refined quantum-mechanical procedures. It is also the one observed predominantly for this types of compound in X-ray crystallographic studies, where the values spread generally between 60°-90° or 270°300° (for a review see [30]). The problem may, however, be raised as concerns the situation in solution for which less precise knowledge is available. As it is practically impossible, because of the complexity of the situation, to construct conformational energy maps for the hydrated species which would indicate the conformational possibilities as a function of the continuous rotation about the two P—0 bonds, for different degrees of hydration, we have computed the essential features of the hydration schemes of the gt and tt forms and compared them with those of the gg form. In this way conclusions may be drawn at least about the effect of hydration on the relative stabilization or destabilization of these three typical forms. 

Sobell and his coworkers (Tsai et. al., 1975 Jain et. al., 1977) utilized our initial experiments with ethidium bromide as guidance in selecting to cocrystallize ethidium with the ribodinucleoside monophosphates. The pyrimidine-purine sequence dinucleosides UpA and CpG were easily cocrystallized with ethidium and formed 2 2 complexes. 

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