Conformations in crystals and solutions of d(CACGTG), d(CCGCGG) and d(GGCGCC) studied by vibrational spectroscopy

Crystals of self camplementary DMA hexamers dCCACGTG>, dCCCGCGG> and d were grown bf vapour dlffuslon technlque and studled by mlcroRaman and mlcroiR spectroscop es. The ollgonucleotldes were studled ln parallel ln solutlon by vlbratlonal spectroscopy. A B->Z transltlon was detected by Raman spectroscopy cl.lrlng the crystalllzatlon procese for dCCACGTG>. Vlbratlonal spectroscopy shows that the dCGGCGCC> crystals adopt a B geametry. On the contrary the d sequence whlch ls shown to be able to undergo ln solutlon or ln fllms qulte easlly the B->Z transltlon, remalns trapped ln crystals ln a geametry whlch may correspond to an lntermedlate conformatlon often proposed ln modele of the B->Z transltlon. The crystals used ln thls study were characterlzed by X-ray dlffractlon. The unlt cell and space group have been determlned

Structure of d(CACGTG), a Z-DNA hexamer containing AT base pairs.

The left-handed Z-DNA conformation has been observed in crystals made from the self-complementary DNA hexamer d(CACGTG). This is the first time that a non disordered Z form is found in the crystal structure of an alternating sequence containing AT base pairs without methylated or brominated cytosines. The structure has been determined and refined to an agreement factor R = 22.9% using 746 reflections in the resolution in the resolution shell 7 to 2.5 A. The overall shape of the molecule is very similar to the Z-structure of the related hexamer d(CG)3 confirming the rigidity of the Z form. No solvent molecules were detected in the minor groove of the helix near the A bases. The disruption of the spine of hydration in the AT step appears to be a general fact in the Z form in contrast with the B form. The biological relevance of the structure in relation to the CA genome repeats is discussed

Analogues structuraux de la serotonine comme marqueurs d'affinite des recepteurs serotoninergiques

International audienceDerivatives of serotonine and bufotenine are synthesized as potential electrophilic or photoactivable labels for the serotoninergic sites. The most promising compound is the azidoethyl-3 indole derivative 13 which presents a high affinity for the site; the corresponding binding appears specific and irreversible after photoactivation