1∶1 Complex of guanine quartet with alkali metal cations detected by electrospray ionization mass spectrometry

Fukushima, K.; Iwahashi, Hideo

doi:10.1039/b002235g

Cited by 64 publications

(91 citation statements)

References 20 publications

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“…Recently, ESI-MS studies have illustrated that stoichiometrics suggestive of Gquadruplexes have been sprayed from solution and persist in the solvent-free environment of the mass spectrometer [39][40][41][42][43][44][45]. Rosuet al studied the 4-strand (dTG 4 T) 4 , the 2-strand (dG 4 T 4 G 4 ) 2 and the single-strand quadruplex dG 3 (T 2 AG 3 ) 3 [43].…”

Section: Scheme 1 (A) the Structure Of A G-quartet The Different Stmentioning

confidence: 99%

G-quadruplexes in telomeric repeats are conserved in a solvent-free environment

Baker

Bernstein

Gabelica

et al. 2006

International Journal of Mass Spectrometry

114

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The structural properties of G-quadruplex forming sequences, such as the human telomeric repeat d(T 2 AG 3 ) n , are of great interest due to their role in cancer and cellular aging. To determine if G-quadruplexes are present in a sol vent-free environment, different lengths of the telomeric repeat d(T 2 AG 3 ) n (where n= 1, 2, 4 and 6) and dTG 4 T were investigated with mass spectrometry, ion mobility and molecular dynamics calculations. Nano-ESI-MS illustrated quadruplex stoichiometries compatible with G-quadruplex structures for each sequence, with dT 2 AG 3 and dTG 4 T forming 4-strand complexes with two and three NH 4 + adducts, d(T 2 AG 3 ) 2 a 2-strand complex, and d(T 2 AG 3 ) 4 and d(T 2 AG 3 ) 6 remaining single-stranded. Experimental cross sections were obtained for all species using ion mobility methods. In all cases, these could be quantitatively matched to model cross sections with specific strand orientations (parallel/antiparallel) and structures. For each species, the solvent-free structures agreed with the solution CD measurements, but the ion mobility/modeling procedure often gave much more detailed structural information.

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Section: Scheme 1 (A) the Structure Of A G-quartet The Different Stmentioning

confidence: 99%

G-quadruplexes in telomeric repeats are conserved in a solvent-free environment

Baker

Bernstein

Gabelica

et al. 2006

International Journal of Mass Spectrometry

114

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“…This data supports the above hypothesis that serine dodecamers cationized by the larger alkali metals, e.g., (Ser 12 ϩRb) ϩ , are composed of smaller cluster units, specifically the tetramer and octamer. Regardless of how the octameric fragment seen in°Figure°8a°is°formed,°e.g.,°simple°loss°of°a°neutral°Ser 4 or with rearrangement, the data suggest that the Rbcationized serine octamer seen in the single-stage mass spectra is the same ion that originates from fragmentation of the precursor (Ser 12 ϩ . The particular formation of (Ser 4 ϩRb) ϩ fragments°seen°in°Figure°8b,°c,°confirms°the°stability°of alkali-metal-cationized serine tetramers and again suggests that they could be the building blocks of the larger serine clusters: the octamers and dodecamers.…”

Section: Ms N Experimentsmentioning

confidence: 84%

“…The corresponding protonated species were studied for comparison. Alkali-metal-cationized serine clusters are readily°formed°and°Figure°1°displays°representative sonic spray mass spectra, where clusters of the type (Ser 4 A convenient way to compare relative abundances of serine clusters formed in the presence of alkali metal ions°is°as°the°magic°number°factor° [64].°This°scaling factor represents the relative intensity of a cluster of interest compared with its neighbors. A magic number is a cluster size that is relatively stable compared with its neighboring sizes.…”

Section: Serine/alkali Metal Mixturesmentioning

confidence: 99%

“…Note that a magic number factor Ͼ1 implies that the particular cluster ion is favored over its neighbors, while a cluster of size n with magic number factor Ͻ1 is less stable. Experiments were performed to quantify, using eq 1, the magic number character of the cluster ions (Ser 4 ϩ2 , respectively. Serine forms particularly stable tetramers with potassium, rubidium, and cesium.…”

Section: Serine/alkali Metal Mixturesmentioning

confidence: 99%

“…This is also the case for the octamers cationized by the smaller alkalis but there is a strong preference for heterochirality in the octamers cationized by the larger alkali cations. Tandem mass spectrometry shows that the octamers and dodecamers cationized by K ϩ , Rb ϩ , and Cs ϩ dissociate mainly by the loss of Ser 4 units, suggesting that the neutral tetramers are the stable building blocks of the observed larger aggregates, (Ser 8 ϩC) ϩ and (Ser 12 ϩC) ϩ . Remarkably, although the Ser 4 units are formed with a strong preference for homochirality, they aggregate further regardless of their handedness and, therefore, with a preference for the nominally racemic 4D:4L structure and an overall strong heterochiral preference.…”

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confidence: 99%

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Alkali metal-cationized serine clusters studied by sonic spray ionization tandem mass spectrometry

Nanita

Sokol

Cooks

2007

J. Am. Soc. Mass Spectrom.

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, or Cs ϩ therefore represent a new type of cluster ion that is homochiral in its internal subunits, which then assemble in a random fashion to form octamers. We tentatively interpret the homochirality of these tetramers as a consequence of assembly of the serine molecules around a central metal ion. The data provide additional evidence that the neutral serine octamer is homochiral and is readily cationized by smaller ions. (J Am Soc Mass Spectrom 2007, 18, 856 -868) © 2007 American Society for Mass Spectrometry C ations of the alkali metals, especially Na ϩ and K ϩ , are involved in a wide variety of biological processes. To take just one example, they participate in the stabilization of noncovalently bound complexes of biological macromolecules in living organisms. In particular, telomeric DNA found at the ends of chromosomes is stabilized by forming multistrand complexes, known as G-quadruplexes, which are held together by hydrogen bonds and further stabilized by the incorporation of alkali metal cations into cavities in their structures [1][2][3]. Mass spectrometry [1], nuclear magnetic resonance, X-ray crystallography and other spectroscopic techniques have shown that small biomolecules can also form relatively stable clusters with alkali metal cations. Examples include nucleobases [4 -6] and nucleosides (as well as their derivatives) [7][8][9], and amino acids [10,11]. A particular feature of alkali metal adducts of small molecular clusters is that they often have a net positive charge and can be characterized by mass spectrometry, a technology that has proven to be key in many studies of clusters [11][12][13][14][15][16][17][18][19].Electrospray ionization (ESI) [20,21] is a versatile ionization technique, which allows biological macromolecules, fragile noncovalently bound complexes [22][23][24][25][26], and other fragile nonvolatile species to be easily transferred from solution into the gas-phase, where mass spectral data can be obtained on the resulting ions. Although the possibility exists of conformational rearrangement [27,28] and other structural changes during the ESI process, there is overwhelming evidence that electrospray ionization is successful in the characterization of solution-phase species via a study of the corresponding gas-phase ions [24,26]. Spray ionization methods derived from the original ESI method include sonic spray ionization (SSI) [29,30] and cold spray ionization (CSI) [31,32]. Recently, electrosonic spray ionization (ESSI) [33,34], a combination of ESI and SSI, was introduced. This particular spray ionization method is very gentle, yet readily yields fully desolvated ions [33,34]. The variant methods SSI, CSI, and ESSI are all believed to provide gentler ionization than normal electrospray, allowing labile species that exist in solution to survive the ionization process as well as being applicable to nonvolatile analytes.The droplet evaporation process in the gentle variant methods on ESI can lead to even more aggregation than occurs in ESI itself. This tendency has been fo...

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