title: Tetramolecular G-quadruplex formation pathways studied by electrospray mass spectrometry.
abstract: Electrospray mass spectrometry was used to investigate the mechanism of tetramolecular G-quadruplex formation by the DNA oligonucleotide dTG(5)T, in ammonium acetate. The intermediates and products were separated according to their mass (number of strands and inner cations) and quantified. The study of the temporal evolution of each species allows us to propose the following formation mechanism. (i) Monomers, dimers and trimers are present at equilibrium already in the absence of ammonium acetate. (ii) The addition of cations promotes the formation of tetramers and pentamers that incorporate ammonium ions and therefore presumably have stacked guanine quartets in their structure. (iii) The pentamers eventually disappear and tetramers become predominant. However, these tetramers do not have their four strands perfectly aligned to give five G-quartets: the structures contain one ammonium ion too few, and ion mobility spectrometry shows that their conformation is more extended. (iv) At 4 degrees C, the rearrangement of the kinetically trapped tetramers with presumably slipped strand(s) into the perfect G-quadruplex structure is extremely slow (not complete after 4 months). We also show that the addition of methanol to the monomer solution significantly accelerates the cation-induced G-quadruplex assembly.
authors.affiliation: Department of Chemistry B6c, University of Liège, Liège, Belgium. f.rosu@ulg.ac.be
authors.forename: Frédéric
authors.initials: F
authors.lastname: Rosu
authors.forename: Valérie
authors.initials: V
authors.lastname: Gabelica
authors.forename: Harmonie
authors.initials: H
authors.lastname: Poncelet
authors.forename: Edwin
authors.initials: E
authors.lastname: De Pauw
mesh_terms: D054856:G-Quadruplexes; D007700:Kinetics; D000432:Methanol / Q000737:chemistry; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D009838:Oligodeoxyribonucleotides; D000432:Methanol
references.citation: Biochemistry. 1996 Jun 18;35(24):8002-8
references.pmid: 8672504
references.citation: Biopolymers. 2000-2001;56(3):147-94
references.pmid: 11745110
references.citation: Chem Rev. 2001 Feb;101(2):377-90
references.pmid: 11712252
references.citation: Anal Chem. 2009 Aug 15;81(16):6708-15
references.pmid: 19601639
references.citation: Proc Natl Acad Sci U S A. 2005 Jan 18;102(3):634-9
references.pmid: 15637158
references.citation: Biophys J. 2003 Sep;85(3):1787-804
references.pmid: 12944293
references.citation: Nucleic Acids Res. 2008 Feb;36(2):477-88
references.pmid: 18045788
references.citation: J Mol Biol. 1999 Jan 8;285(1):233-43
references.pmid: 9878402
references.citation: Angew Chem Int Ed Engl. 2004 Jan 30;43(6):668-98
references.pmid: 14755695
references.citation: Rapid Commun Mass Spectrom. 2004;18(20):2401-14
references.pmid: 15386629
references.citation: Biochimie. 2008 Aug;90(8):1149-71
references.pmid: 18355457
references.citation: Trends Biochem Sci. 2005 May;30(5):231-4
references.pmid: 15896739
references.citation: Nucleic Acids Res. 2005 Jun 28;33(11):3691-7
references.pmid: 15985684
references.citation: Biochemistry. 1997 Dec 9;36(49):15428-50
references.pmid: 9398273
references.citation: Nano Lett. 2007 Apr;7(4):981-6
references.pmid: 17352504
references.citation: Chem Soc Rev. 2007 Feb;36(2):296-313
references.pmid: 17264931
references.citation: Curr Opin Struct Biol. 2009 Jun;19(3):239-50
references.pmid: 19487118
references.citation: Nucleic Acids Res. 2008 Oct;36(17):5482-515
references.pmid: 18718931
references.citation: Bioconjug Chem. 2008 Mar;19(3):607-16
references.pmid: 18254584
references.citation: Nucleic Acids Res. 2005 Jan 07;33(1):81-94
references.pmid: 15642696
references.citation: Exp Mol Pathol. 2009 Jun;86(3):151-64
references.pmid: 19454272
references.citation: Chemistry. 2009 Aug 10;15(32):7792-806
references.pmid: 19421976
references.citation: J Am Soc Mass Spectrom. 2008 Apr;19(4):550-9
references.pmid: 18313939
references.citation: Curr Opin Struct Biol. 2006 Jun;16(3):288-98
references.pmid: 16714104
references.citation: Mass Spectrom Rev. 2001 Mar-Apr;20(2):61-87
references.pmid: 11455562
references.citation: Rapid Commun Mass Spectrom. 2002;16(18):1729-36
references.pmid: 12207360
references.citation: J Am Chem Soc. 2008 Oct 29;130(43):14161-9
references.pmid: 18826223
references.citation: Biochimie. 2008 Jul;90(7):1074-87
references.pmid: 18261993
references.citation: Org Biomol Chem. 2006 Sep 21;4(18):3383-91
references.pmid: 17036128
references.citation: Science. 2008 Sep 26;321(5897):1795-9
references.pmid: 18818351
references.citation: Nucleic Acids Res. 2007;35(22):7429-55
references.pmid: 17913750
references.citation: J Am Chem Soc. 2008 Aug 6;130(31):10208-16
references.pmid: 18627159
references.citation: Nucleic Acids Res. 2007;35(9):3064-75
references.pmid: 17452368