Abstract

A three-dimensional X-ray analysis of guanosine hydrobromide hemihydrate was undertaken in order to study the effect of N(7) protonation on the molecular conformation of guanosine. The crystals are monoclinic, space group P21, with cell dimensions: a = 6.29, b = 15.42, c = 14.96 A; β = 102°; Z = 4. 2500 observed reflexions were collected by the multiple-film equi-inclination Weissenberg technique, and measured manually with a microdensitometer. The structure was solved by the heavy-atom method. The atomic parameters of the guanosine hydrobromide hemihydrate structure were refined by least-squares calculations to an R index of 0.058 for 2500 observed reflexions. There are two bromine atoms, two guanosine molecules and one water molecule in the asymmetric unit. The two guanosine molecules are in anti conformations with χcn equal to − 1.8 and 31.2°. The sugar conformations are C(3′)endo-C(4′)exo, and C(3′)endo-C(2′)exo respectively. The conformations of C(5′)-O(5′) bonds are gauche-gauche in the two cases. Associations are formed between the bromine ions and the pyrimidine part of the purines, while protonation occurs on the N(7) of the imidazole rings.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.