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Guanine Ring (guanine + ring)
Selected AbstractsAssignments and hydrogen bond sensitivities of UV resonance Raman bands of the C8-deuterated guanine ringJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2002Akira Toyama Isotope-edited Raman spectroscopy, a combination of site-selective isotopic labeling and Raman difference spectroscopy, is a useful method for studying the structure and interaction of individual nucleic acid residues in oligonucleotides. To obtain basic data for applying isotope-edited Raman spectroscopy to guanine residues, we studied the vibrational modes of UV resonance Raman bands of the C8-deuterated guanine ring by examining the wavenumber shifts upon seven isotopic substitutions (2- 13C, 2- 15N, 6- 18O, 7- 15N, 8- 13C, 9- 15N and 1,- 13C). The hydrogen bond sensitivities of the Raman bands were also investigated by comparing the Raman spectra recorded in several solvents of different hydrogen bonding properties. Some of the Raman bands were found to be markers of hydrogen bonding at specific donor or acceptor sites on the guanine ring. The Raman bands, which shift on C8-deuteration, remain in the difference spectrum between the unlabeled and C8-deuterated guanine rings. Among them, a negative peak around 1525 cm,1 and a strong positive/negative peak pair around 1485/1465 cm,1 serve as markers of hydrogen bonding at N7 and C6O, respectively. Another weak positive/negative peak pair around 1025/1040 cm,1 is sensitive to hydrogen bonding at the proton donor sites (N1,H and N2,H2). The applicability of the hydrogen bond markers has been tested by using a 22-mer oligonucleotide duplex containing eight guanine residues and its analog in which a single guanine residue is C8-deuterated. The difference spectrum shows that the hydrogen bonding state of the guanine residue at the labeled position is consistent with the Watson,Crick base pair structure of DNA. Isotope-edited Raman spectroscopy is a useful tool for studying the hydrogen bonding state of selected guanine residues in oligonucleotides. Copyright © 2002 John Wiley & Sons, Ltd. [source] Structure of Staphylococcus aureus guanylate monophosphate kinaseACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2006Kamel El Omari Nucleotide monophosphate kinases (NMPKs) are potential antimicrobial drug targets owing to their role in supplying DNA and RNA precursors. The present work reports the crystal structure of Staphylococcus aureus guanylate monophosphate kinase (SaGMK) at 1.9,Å resolution. The structure shows that unlike most GMKs SaGMK is dimeric, confirming the role of the extended C-terminus in dimer formation as first observed for Escherichia coli GMK (EcGMK). One of the two SaGMK dimers within the crystal asymmetric unit has two monomers in different conformations: an open form with a bound sulfate ion (mimicking the ,-phosphate of ATP) and a closed form with bound GMP and sulfate ion. GMP-induced domain movements in SaGMK can thus be defined by comparison of these conformational states. Like other GMKs, the binding of GMP firstly triggers a partial closure of the enzyme, diminishing the distance between the GMP-binding and ATP-binding sites. In addition, the closed structure shows the presence of a potassium ion in contact with the guanine ring of GMP. The potassium ion appears to form an integral part of the GMP-binding site, as the Tyr36 side chain has significantly moved to form a metal ion,ligand coordination involving the lone pair of the side-chain O atom. The potassium-binding site might also be exploited in the design of novel inhibitors. [source] Assignments and hydrogen bond sensitivities of UV resonance Raman bands of the C8-deuterated guanine ringJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2002Akira Toyama Isotope-edited Raman spectroscopy, a combination of site-selective isotopic labeling and Raman difference spectroscopy, is a useful method for studying the structure and interaction of individual nucleic acid residues in oligonucleotides. To obtain basic data for applying isotope-edited Raman spectroscopy to guanine residues, we studied the vibrational modes of UV resonance Raman bands of the C8-deuterated guanine ring by examining the wavenumber shifts upon seven isotopic substitutions (2- 13C, 2- 15N, 6- 18O, 7- 15N, 8- 13C, 9- 15N and 1,- 13C). The hydrogen bond sensitivities of the Raman bands were also investigated by comparing the Raman spectra recorded in several solvents of different hydrogen bonding properties. Some of the Raman bands were found to be markers of hydrogen bonding at specific donor or acceptor sites on the guanine ring. The Raman bands, which shift on C8-deuteration, remain in the difference spectrum between the unlabeled and C8-deuterated guanine rings. Among them, a negative peak around 1525 cm,1 and a strong positive/negative peak pair around 1485/1465 cm,1 serve as markers of hydrogen bonding at N7 and C6O, respectively. Another weak positive/negative peak pair around 1025/1040 cm,1 is sensitive to hydrogen bonding at the proton donor sites (N1,H and N2,H2). The applicability of the hydrogen bond markers has been tested by using a 22-mer oligonucleotide duplex containing eight guanine residues and its analog in which a single guanine residue is C8-deuterated. The difference spectrum shows that the hydrogen bonding state of the guanine residue at the labeled position is consistent with the Watson,Crick base pair structure of DNA. Isotope-edited Raman spectroscopy is a useful tool for studying the hydrogen bonding state of selected guanine residues in oligonucleotides. Copyright © 2002 John Wiley & Sons, Ltd. [source] G,G Base-Pairing in Nucleobase Adducts of the Anticancer Drug cis -[PtCl2(NH3)(2-picoline)] and Its trans IsomerCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2005Geraldine McGowan Abstract cis -[PtCl2(NH3)(2-picoline)] (AMD473) is a sterically-hindered anticancer complex with a profile of chemical and biological activity that differs significantly from that of cisplatin. Adducts of AMD473 with neutral 9-ethylguanine (9-EtGH) and anionic (N1-deprotonated) 9-ethylguanine (9-EtG) as perchlorate and nitrate salts, and also a nitrate salt of the trans isomer (AMD443), were prepared and their structures determined by X-ray crystallography: cis -[Pt(NH3)(2-pic)(9-EtGH)2](ClO4)2 (1),2,H2O,Me2CO, cis -[Pt(NH3)(2-pic)(9-EtGH)2](NO3)2 (2),2,H2O, cis -[Pt(NH3)(2-pic)(9-EtGH)(9-EtG)]NO3 (3),3.5,H2O, trans -[Pt(NH3)(2-pic)(9-EtGH)(9-EtG)]NO3 (4),8,H2O. In all cases, platinum coordination is through N7 of neutral (1, 2) and anionic (3, 4) guanine. In each complex, the guanine bases are arranged in the head-to-tail conformation. In complex 1, there is an infinite array of six-molecule cycles, based on both hydrogen bonding and ,,, stacking of the 2-picoline and guanine rings. Platinum(II) coordinated at N7 acidifies the N1 proton of neutral 9-ethylguanine (pKa=9.57) to give pKa1=8.40 and pKa2=8.75 for complex 2, and pKa1=7.77 and pKa2=9.00 for complex 4. In complexes 3 and 4, three intermolecular hydrogen bonds are formed between neutral and deprotonated guanine ligands involving O6, N1 and N2 sites. Unusually, both of the platinated guanine bases of complexes 3 and 4 participate in this triple GG hydrogen bonding. This is the first report of X-ray crystal structures of nucleobase adducts of the promising anticancer drug AMD473. [source] | ||||||||||