Where does restriction collide?

In molecular biology, restriction is the cell's cutting of foreign DNA by enzymes that recognise a specific short sequence and cleave the double helix there, the bacterial defence that early workers saw as the host 'restricting' the growth of invading phage. Smith and Wilcox's 1970 A restriction enzyme from Hemophilus influenzae. I. Purification and general properties isolated the first such sequence-specific endonuclease and so turned the phenomenon into a tool. The referent is sequence-specific DNA cleavage, measured by the recognition site and cut pattern an enzyme produces, and it has nothing to do with a T cell reading self-markers or a bound on a Fourier transform beyond the shared image of narrowing what is allowed.[1]

Unit

The recognition sequence and cleavage position of an endonuclease

Recovery means

Not applicable

Measured by

Characterised by the recognition-site sequence, cut position, and the restriction-fragment pattern on a gel

In immunology, restriction (MHC restriction) is the rule that a T cell recognises a foreign peptide only when it is displayed on the particular self major-histocompatibility molecules the T cell matured with, so recognition is 'restricted' to self-MHC rather than being free for any antigen. Zinkernagel and Doherty's 1974 Restriction of in vitro T cell-mediated cytotoxicity in lymphocytic choriomeningitis within a syngeneic or semiallogeneic system showed that killer T cells lysed infected target cells only when the targets shared MHC type, which established the dual recognition of antigen plus self. The referent is this constraint on T-cell recognition, and it is a different construct from an enzyme that cuts DNA or a theorem about Fourier transforms, joined only by the meaning of being hemmed in.[2]

Unit

The self-MHC allele required for a T cell to recognise its antigen

Recovery means

Not applicable

Measured by

Demonstrated by matched-versus-mismatched target killing or response assays across MHC types

In harmonic analysis, restriction is the operation of limiting a function's Fourier transform to a lower-dimensional set such as a sphere, and the surprising fact that this makes sense at all for suitable functions despite the transform being defined only almost everywhere. Tomas's 1975 A restriction theorem for the Fourier transform proved one of the first such estimates, bounding the restricted transform on a sphere and opening the restriction problem that drives much modern analysis. The referent is this restriction operator and the inequalities that control it, a purely mathematical construct unrelated to a DNA-cutting enzyme or a T cell's self-marker rule, sharing only the everyday meaning of confining something to a smaller domain.[3]

Unit

The exponents for which a transform restricts boundedly to a surface

Recovery means

Not applicable

Measured by

Expressed through L^p to L^q restriction estimates and the admissible exponent range