Where does filament collide?

A long, thin protein polymer that forms part of the internal scaffolding of a cell or a muscle fibre, such as an actin filament or an intermediate filament. Huxley's 1957 The double array of filaments in cross-striated muscle resolved muscle into interleaved thick and thin protein filaments that slide past one another, and Ishikawa, Bischoff, and Holtzer's 1968 study named the intermediate-sized filaments, a third class between the actin and myosin threads. The referent is a molecular assembly built from repeating protein subunits, measured in nanometres of diameter under the electron microscope, and it is unrelated to the stalk of a flower's stamen or a thread of galaxies in space.[1][2]

Unit

One protein polymer, scaled by its diameter in nanometres and its length

Recovery means

Filaments assemble and disassemble as subunits add or drop off, so the polymer can regrow after it shortens

Measured by

Imaged by electron microscopy and fluorescence, and classed by diameter into actin, intermediate, and thick filaments

One of the vast, thread-like concentrations of galaxies, gas, and dark matter that link clusters across the largest structures in the universe, the cosmic web. Bond, Kofman, and Pogosyan's 1996 How filaments of galaxies are woven into the cosmic web described how gravity draws matter out of expanding voids into sheets and then into these dense filaments, extending the earlier picture of gravitational collapse from Zeldovich. The referent is a structure that can stretch hundreds of millions of light-years, mapped from the positions of galaxies, and it bears no relation to a stamen's stalk in a flower or a protein thread inside a cell.[3]

Unit

One filament of the cosmic web, scaled by its length in millions of light-years

Recovery means

Not applicable

Measured by

Traced from the three-dimensional positions of galaxies in redshift surveys and in cosmological simulations