Where does insulator collide?

In molecular biology an insulator is a DNA boundary element with two activities: placed between an enhancer and a promoter it blocks their communication, and flanking a gene it shields it from the spread of repressive or activating chromatin from its neighbours. Kellum and Schedl devised a position-effect assay that defined such boundaries of higher-order chromosomal domains. The referent is a regulatory DNA sequence, which shares only the word with a ceramic that stops current or a quantum phase of matter.[1]

Unit

Not applicable

Recovery means

Not applicable

Measured by

Demonstrated by enhancer-blocking and position-effect assays showing a boundary to chromatin influence

A topological insulator is a quantum phase of matter that behaves as an ordinary insulator in its interior but carries symmetry-protected conducting states on its surface or edges. The distinction comes from the topology of the material's electronic band structure rather than from any local order parameter, so the edge conduction is robust against disorder and does not vanish under moderate perturbation. Hasan and Kane's colloquium set out the theory and experiments. The referent is a bulk-insulating, edge-conducting solid, distinct from a classical insulator and from a DNA boundary.[2]

Unit

The bulk energy gap and the protected surface or edge conductance

Recovery means

Not applicable

Measured by

Probed by angle-resolved photoemission of surface states and transport showing a conducting edge over an insulating bulk