Escherichia coli GroES has also been shown to bind ATP cooperatively, and with an affinity comparable to that of GroEL.

Each GroEL ring contains a central cavity, known as the `Anfinsen cage', that provides an isolated environment for protein folding.

[17] Because the rosette inhibition assay for EPF is indirect, substances that have similar effects may confound the test.

Pig semen, like EPF, has been shown to inhibit rosette formation – the rosette inhibition test was positive for one day in sows mated with a vasectomized boar, but not in sows similarly stimulated without semen exposure.

[17][27] Injecting anti-EPF antibodies into mice after mating significantly [quantify] reduced the number of successful pregnancies and number of pups;[28][29] no effect on growth was seen when mice embryos were cultured in media containing anti-EPF antibodies.

[13] Interest in EPF for this purpose has continued,[35] although current test methods have not proved sufficiently accurate for the requirements of livestock management.

[42][43][44][45] EPF may also be used to determine whether pregnancy prevention mechanism of birth control methods act before or after fertilization.

A 1982 study evaluating EPF levels in women with IUDs concluded that post-fertilization mechanisms contribute significantly[quantify] to the effectiveness of these devices.

[46] However, more recent evidence, such as tubal flushing studies indicates that IUDs work by inhibiting fertilization, acting earlier in the reproductive process than previously thought.

[47] For groups that define pregnancy as beginning with fertilization, birth control methods that have postfertilization mechanisms are regarded as abortifacient.