Dirk Badura | PubMed Health

PubMed2002

Pyrazolylborate-zinc-nucleobase-complexes, 3:(1) base pairing studies.

In solution, the pyrazolylborate-zinc-nucleobase complexes show self-association and base pairing with external nucleobases. The self-association was studied quantitatively for Tp(Cum,Me)Zn-hypoxanthinate and Tp(Cum,Me)Zn-thyminate; the dimerization constants K(D) are 63 +/- 8 and 0.2 +/- 0.1 M(-1), respectively. Of the external nucleobases, 9-ethyladenine forms stable base pairs with the thyminate, uracilate, and xanthinate complexes, 9-isobutylguanine only with the cytosinate complex, 1-methylthymine with the adeninate and diaminopurinate complexes, and 1-methyluracil with the diaminopurinate complex. The association constant for the base pair Tp(Cum,Me)Zn-thyminate:9-ethyladenine was determined by NMR methods as K = 66 +/- 10 M(-1). Structure determinations of the crystalline adducts have confirmed the base pairing for Tp(Cum,Me)Zn-thyminate:9-ethyladenine, Tp(Cum,Me)Zn-cytosinate:9-isobutylguanine, and Tp(Cum,Me)Zn-xanthinate:9-ethyladenine. Both Watson-Crick and Hoogsteen base pairs have been observed. In the solid state, extended base pairing leads to quartet and polymer arrangements.

Journal Article↗

PubMed2002

Pyrazolylborate-zinc-nucleobase-complexes, 2:(1) preparations and structures of Tp(Cum,Me)Zn and Tp(Ph,Me)Zn complexes.

The interactions of the nine most significant nucleobases (thymine, uracil, dihydrouracil, cytosine, adenine, guanine, diaminopurine, xanthine, hypoxanthine, in their deprotonated forms) with zinc and with themselves in pyrazolylborate zinc complexes Tp(Cum,Me)Zn-base and Tp(Ph,Me)Zn-base are described. Except for guanine, the complexes Tp*Zn-base could be isolated in all cases. Structure determinations could be performed for seven of the eight product types. Except for dihydrouracil and xanthine, the zinc ion is attached to that nitrogen of the base which in nucleosides bears the sugar moiety. In the solid state, all zinc-bound nucleobases are involved in hydrogen bonding interactions. Except for xanthine, this includes homo base pairing across a crystallographic inversion center.

Adenine↗