It appears also from (II) that the null-lines whose distance from the central axis is r are tangent lines to a system of helices of slope tan 1(r/k); and it is to be noticed that these helices are left-handed if the given wrench is righthanded, and vice versa.
As illustrative examples of the form of wings alluded to, those of the beetle, bee and fly may be cited - the pinions in those insects acting as helices, or twisted levers, and ' Revue des tours scientifiques de la France et del' Etranger, 1869.
Such a mutation could for example be in one of the DNA-binding helices introducing a kink in a normally straight and rigid helical conformation.
The positions of the transmembrane helices of the core dimer are based on Fig.
helical bundle composed by two pairs of antiparallel helices.