In-cell NMR of a DNA G-quadruplex and ligand

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.

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Can G-quadruplexes be seen by NMR inside cells?

Yes—they form under physiological conditions and are NMR-visible.

How stable is d(TG4T)4 in oocytes?

It resists numerous enzymatic activities and behaves as a long-lived species.

What happens to the ligand-bound oligonucleotide in cells?

It can become NMR-invisible, suggesting extra partners or precipitation.

At what temperature were NMR experiments run, and why?

About 16 °C, to spare cells and still see imino signals.

What magnet was used?

An 800 MHz Bruker spectrometer with a cryogenic TXI probe.

How long could oocyte NMR acquisitions last?

Longer than 48 h.

How did in-cell linewidths compare with in vitro?

Broader: 22–40 Hz versus 16–18 Hz in vitro.

What fold does the d(TG4T)4 imino signature report?

An all-parallel four-stranded G-quadruplex.

What does the imino signature report?

The global G-quadruplex structural pattern; it is salt- and ligand-sensitive.

Which 2D experiment detected imino 1H–15N correlations?

SOFAST-HMQC.

In which living cells was the fold probed with ligands?

Xenopus laevis oocytes.