Structural organization of guanosine derivatives in dilute solutions: small angle neutron scattering analysis

Carsughi, F.; Ceretti, Monica; Mariani, Paolo

doi:10.1007/bf00185430

Cited by 30 publications

(28 citation statements)

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“…This result, together with sizes estimated from neutron small angle scattering in the isotropic phase (69.2 8, at 1 wt% and 71.2 A at 1-5 wt%) [25] indicates that cylinders are growing along the N* phase.…”

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Structural study of the aggregates formed by the dinucleoside phosphate G2 in aqueous solution

et al. 1992

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X-ray diffraction results in magnetically oriented samples of aqueous solutions of the sodium salt of the dinucleoside phosphate G2 in the cholesteric N* phase are presented. The symmetry of the diffraction confirms a model of stacking of tetrameric disks forming cylindrical aggregates in the N* phase. A weak band at 7 A not previously observed gives further information on the inner structure of the cylindrical aggregates. Analysis of the diffraction peak position in low angle evidences a change in functional behaviour of the distance a between cylinder axes as a function of the volume concentration c, of G2. In the H phase, accc;'/' as it should for infinite cylinders; in the N* phase, ~c c c ; ' /~, typical of finite cylinders. The cross-over of functional behaviour occurs at the N*-H phase transition. There is therefore cylinder growth along the N* phase. IntroductionAmong the nucleosides commonly found in DNA and RNA, only guanosine (and some derivatives) is able to self-associate in water solution to form stable structures (reviewed in [l] and [2]): highly ordered gels, fibres and other macroaggregates have been in fact extensively investigated [3-61. The common structural unit has been found to be a planar disc-shaped aggregate formed by four guanosine residues, hydrogen bonded in a Hoogsteen mode [7]. Furthermore, NMR investigations of 5'-guanosine monophosphate aqueous solutions showed that the self-aggregation process can also take place in very dilute solutions, via stacking of planar tetramers [S-101. The biological relevance of this very special feature is not yet defined on the one hand this could have had prebiotic significance in the origin of the genetic code [9-lo]. On the other hand telomers and related guanine-rich sequences can form higher-order structures (quadriplexes) formed by guanine-quartet (see in particular [ 111): it has been then proposed, for example, that the quadriplex formation might provide a means for homologous chromosome alignment at meiosis [12] or provide a general mechanism for aligning and pairing two duplexes for recombination ([13], see also [l 13).Recently, the aqueous solution of the dinuceoside phosphate 2'-deoxyguanylyl-(3'-5')-2'-deoxyguanosine (d(GpG) or G2) has been studied [14,15]. In particular, the sodium salt of G2 forms cholesteric and hexagonal liquid-crystalline phases on decreasing water content. From the analysis of the measured X-ray diffraction peaks

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Section: Resultsmentioning

confidence: 50%

Structural study of the aggregates formed by the dinucleoside phosphate G2 in aqueous solution

et al. 1992

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“…We also analyzed the ln(dZ/dSZ(Q) Q ) vs. Q 2 plots [6] in which a linear behavior in the low Q range is expected in the presence of needle-like scattering particles 181 [lo]. However, the result obtained were not unambiguous, so that it was not possible to determine the radius of the cylindrical aggregate cross section.…”

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“…According to previous SANS measurements in deoxyguanosine systems [6], the basic structure of the scattering particles existing in isotropic solution is assumed to be similar to the one determined for the columns forming the hexagonal and cholesteric phases. A similar hypothesis seems reasonable also in the case of folates: accordingly, the experimental gyration radius could be compared to that of a rod-shaped model: with reference to the structure of the columns, as determined in the mesophases [4] [5], the radius R of the scattering cylindrical particle corresponds to the radius of the tetrameric disk.…”

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“…If the Guinier law is satisfied (Q,,, R , < 1.5), the gyration radius R, and the dZ/dQ(O) value can be obtained by a linear fit of the experimental SANS data in the so-called Guinier plot [9] [l I] In(dZ/dQ (Q)) vs. Q2. Likewise, in the case of needle-like particles, from the Guinier plot In(dZ/dQ(Q) Q) vs. Q2, the cross-sectional intensity scattered at zero angle and the gyration radius of the cross section of the scattering particle R, can be determined [6] [8] [9]. Circular Dichroism.…”

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The Self‐Recognition and Self‐Assembly of Folic Acid Salts in Isotropic Water Solution

Gottarelli

Mezzina

Spada

et al. 1996

Helvetica Chimica Acta

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The self-assembly of alkaline folates in isotropic water solutions, with or without added salts, has been investigated by small-angle neutron-scattering, circular-dichroism, and NMR techniques. The assembled species are chiral, cylindrical aggregates of finite length, composed of stacked tetramers; each tetramer is formed by Hoogsteen-bonded folate residues. The assembly process is more efficient in the presence of an excess of Na-I ions, leading to longer aggregates with stronger tetramer-tetramer interaction. In pure water, the rods are shorter and the tetramer-tetramer interaction weaker. Association between folates can be detected by circular-dichroism spectroscopy starting from a concentration of 6.10(-4) mol l(-1), well below the critical concentration for the formation of the cholesteric mesophase (ca. 0.5 mol l(-1))

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“…The columns, which have structural features similar to those of the four-stranded helix of poly(G), are already assembled in isotropic water solutions. 8 The mesophases are formed after a critical concentration is reached, the value of which depends on the oligonucleotide sequence and on the nature and concentration of the positive ions present in the solution.…”

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Self-assembly of dideoxyguanosine (3?,3?) and (5?,5?)-monophosphates

et al. 1998

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The title compounds show a pronounced cation‐directed ability to self‐assemble in water and to gives columnar structures similar to four‐stranded helices; for compound (5′→5′)‐d(GpG), this leads to the formation of cholesteric and hexagonal liquid crystalline phases. Both phases are columnar and the cholesteric phase is left‐handed. This behaviour is a further confirmation of the tendency of guanine derivatives to self‐assemble to give stacked columnar structures whenever not impossible for structural reasons. The CD spectra of the aggregates in isotropic solutions are dominated by a negative exciton couplet centred around 250 nm associated to a left‐handed columnar chirality. The shapes of the profiles, in the 220–300‐nm region, for (5′→5′)‐d(GpG) (in water or in saline solutions) and for (3′→3′)‐d(GpG) (in KCl solution) are quasi‐mirror images of those of poly(G) and (3′→5′)‐d(GpG). The appearance of relatively intense CD signals around 280–300 nm in solution of (3′→3′)‐d(GpG) in the presence of NaCl resembles that of (3′→5′)‐d(GpG) in the presence of Rb+ or Na+. In the compounds investigated in this work, which present two equivalent ends, one observes the two CD features that have been associated, in the current literature, with the signature of four‐stranded parallel and antiparallel structures: hence the origin of these CD bands cannot be found in the polarity of the strands. Self‐assembly is favoured by the addition of extra salt and the stabilising effect of K+ is greater than that of Na+, in the case of (3′→3′)‐d(GpG), an assembled species could be detected by CD only in the presence of extra salt. Chirality 10:734–741, 1998. © 1998 Wiley‐Liss, Inc.

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Structural organization of guanosine derivatives in dilute solutions: small angle neutron scattering analysis

Cited by 30 publications

References 13 publications

Structural study of the aggregates formed by the dinucleoside phosphate G2 in aqueous solution

Structural study of the aggregates formed by the dinucleoside phosphate G2 in aqueous solution

The Self‐Recognition and Self‐Assembly of Folic Acid Salts in Isotropic Water Solution

Self-assembly of dideoxyguanosine (3?,3?) and (5?,5?)-monophosphates

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