What does G4s stand for?

The abbreviation G4s stands for G-quadruplexes in nucleic-acid research. Here the lowercase s marks the plural of G4. These folded structures involve stacked groups of four guanine bases, called G-tetrads. This notation is different from the uppercase peptide-linker code G4S.

Look first for the molecule and the level being described. In a DNA paper, G denotes guanine, a nucleic-acid base; in the peptide motif G4S, G denotes glycine, an amino acid. The same letter therefore needs its scientific context. The structure abbreviation also separates a tetrad from a whole folded quadruplex and from an assembly of several quadruplex units. The four-stranded description does not always mean four separate DNA molecules. The deposited record 143D describes one twenty-two-residue DNA chain folding intramolecularly with three stacked G-tetrads under its stated conditions. This is a DNA example; it does not specify every DNA or RNA quadruplex topology. That particular record is a useful counterexample to counting molecules from the name alone, rather than a template for every possible structure. In our fictional reading note, an author describes a single G4 with three tetrads. A draft calls that three G4 molecules. The draft has counted the stacked planes as complete folded units; the note should keep the one unit and its three tetrads separate. A second invented caption names a G4 dimer. It counts two quadruplex units, while the number of tetrads inside either unit needs its own description. The exercise below follows these explicitly supplied levels. It predicts no folding from a pasted sequence and draws no biological or clinical conclusion from a structure label.

Rosi et al.: Connecting Structure, Conformation and Energetics of Human Telomere G-quadruplex Multimers ↗