Spectroscopy
In-cell NMR of a DNA G-quadruplex and ligand
Open access · cc by · source: Europe PMC
A parallel d(TG4T)4 G-quadruplex remains NMR-visible and long-lived in Xenopus oocytes, but ligand 360A can hide the complex on the NMR timescale.
Study at a glance
- Design
- Animal / in-vitro — In-cell NMR of 15N/13C-labeled d(TG4T)4 microinjected into Xenopus oocytes ± 360A ligand
- N
- Oocyte in-cell NMR — no single reported oocyte analytic N in stored summary
- Population
- Living Xenopus laevis oocytes
- Outcome
- Intracellular G-quadruplex persistence and ligand-bound NMR visibility
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
The all-parallel G-quadruplex forms in cells and survives enzymatic attack for many hours. Ligand-bound oligonucleotide appears NMR-invisible in cells, implying extra binding partners or precipitation, so in vitro ligand studies may not transfer directly.
Methodology
Authors micro-injected 15N/13C-labeled d(TG4T)4 into living Xenopus laevis oocytes and recorded 800 MHz SOFAST-HMQC imino spectra with and without the G-quadruplex ligand 360A, comparing in-cell and in vitro fingerprints.
Limitations
The study uses oocytes, not human tumor cells, and does not assign the cellular partners that silence the ligand complex.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
This library holds 9 empirical chemistry papers on spectroscopy with isolated findings, rates or spectra rather than reviews.
Evidence for the claim as stated.
A parallel d(TG4T)4 G-quadruplex remains NMR-visible and long-lived in Xenopus oocytes, but ligand 360A can hide the complex on the NMR timescale.
Evidence for the claim as stated.
Isotope-edited NMR can watch a G-quadruplex inside a cell rather than only in a buffer. ¹⁵N/¹³C-labelled d(TG4T)₄ micro-injected into Xenopus oocytes kept an all-parallel fold for hours; the same oligonucleotide plus ligand 360A became NMR-invisible in cells, implying extra partners or precipitation that in-vitro ligand studies miss.
Evidence for the claim as stated.
Solution NMR, in-cell NMR and solid-state/identity NMR are not the same experiment. Titration Kas in wet DMSO, oocyte SOFAST-HMQC of a labelled oligonucleotide, and ³¹P shifts of a diphosphene answer different questions. A student who says 'we ran NMR' without saying which nuclei and which medium cannot compare those papers.
Evidence for the claim as stated.
A missing peak can mean opposite things. In oocytes the ligand-bound G-quadruplex vanished, which the authors read as extra binding or precipitation — not as 'the complex did not form.' In cage isomer assignment, extra peaks mean a second isomer is present. Treating silence as non-binding is unsafe.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Solution NMR, in-cell NMR and solid-state/identity NMR are not the same experiment. Titration Kas in wet DMSO, oocyte SOFAST-HMQC of a labelled oligonucleotide, and ³¹P shifts of a diphosphene answer different questions. A student who says 'we ran NMR' without saying which nuclei and which medium cannot compare those papers.
A missing peak can mean opposite things. In oocytes the ligand-bound G-quadruplex vanished, which the authors read as extra binding or precipitation — not as 'the complex did not form.' In cage isomer assignment, extra peaks mean a second isomer is present. Treating silence as non-binding is unsafe.
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Same topic cluster — not a recommendation engine.