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Clustering of nucleosides in the presence of alkali metals: Biologically relevant quartets of guanosine, deoxyguanosine and uridine observed by ESI‐MS/MS
Author(s) -
Aggerholm Tenna,
Nanita Sergio C.,
Koch Kim J.,
Cooks R. Graham
Publication year - 2003
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.405
Subject(s) - chemistry , guanosine , alkali metal , guanine , nucleobase , cytidine , deoxyguanosine , deoxyribose , glycosidic bond , uracil , electrospray ionization , uridine , covalent bond , thymine , hydrogen bond , nucleic acid , stereochemistry , dna , rna , adduct , nucleotide , molecule , organic chemistry , ion , biochemistry , gene , enzyme
Abstract Electrospray ionization (ESI) mass spectra of nucleosides, recorded in the presence of alkali metals, display alkali metal ion‐bound quartets and other clusters that may have implications for understanding non‐covalent interactions in DNA and RNA. The tetramers of guanosine and deoxyguanosine and also their metaclusters (clusters of clusters), cationized by alkali metals, were observed as unusually abundant magic number clusters. The observation of these species in the gas phase parallels previous condensed‐phase studies, which show that guanine derivatives can form quartets and metaclusters of quartets in solution in the presence of metal cations. This parallel behavior and also internal evidence suggest that bonding in the guanosine tetramers involves the bases rather than the sugar units. The nucleobases thymine and uracil are known to form magic number pentameric adducts with K + , Cs + and NH 4 + in the gas phase. In sharp contrast, we now show that the nucleosides uridine and deoxythymidine do not form the pentameric clusters characteristic of the corresponding bases. More subtle effects of the sugars are evident in the fact that adenosine and cytidine form numerous higher order clusters with alkali metals, whereas deoxyadenosine and deoxycytidine show no clustering. It is suggested that hydrogen bonding between the bases in the tetramers of dG and rG are the dominant interactions in the clusters, hence changing the ribose group to deoxyribose (and vice versa) generally has little effect. However, the additional hydroxyl group of RNA nucleosides enhances the non‐selective formation of higher‐order aggregates for adenosine and cytidine and results in the lack of highly stable magic number clusters. Some clusters are the result of aggregation in the course of ionization (ESI) whereas others appear to be intrinsic to the solution being examined. Copyright © 2003 John Wiley & Sons, Ltd.