Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

The antiparallel side-to-side association of spectrin alpha and beta monomers is a two-step process which occurs in seconds even at 0 degrees C and at low concentrations. Assembly involves initial contact of complementary nucleation sites on each subunit, which are located near the actin binding end of the long, flexible heterodimer rod. The minimum nucleation sites are comprised of approximately four contiguous 106-residue homologous segments or repeats. Three repeats in the nucleation site contain an 8-residue insertion and have the highest homology to the four spectrin-like repeats in alpha-actinin. The adjacent actin binding domain on the beta subunit and the adjacent EF hand motifs on the alpha subunit are not required for heterodimer assembly. The nucleation sites probably have a specific lock and key structure which defines the unique side-to-side pairing of the many homologous segments in both subunits. Assembly of spectrin heterodimers is probably most analogous to a zipper. After initial nucleation site binding, the remainder of the subunits quickly associate along their full lengths to reconstitute a normal dimer by supercoiling around each other to form a rope-like, flexible rod. Assembly is terminated if either polypeptide is interrupted by a protease cleavage. Heterozygotic mutations involving either nucleation site are predicted to affect allele incorporation into the mature membrane skeleton.
Alpha-spectrin and beta-spectrin subunits form parallel or antiparallel heterodimers?

Sidi Barrani (Egyptian Arabic: pronounced (sidi bni)) is a town in Egypt, near the Mediterranean Sea, about 95 km (59 mi) east of the border with Libya, and around 240 km (150 mi) from Tobruk, Libya.
By which body of water is Sidi Barrani located?

Claire Ridgway (born 1971) is a British writer of history books about the Tudor dynasty, with a particular focus on the life of the Boleyn family.

When was the birth of Claire Ridgway?