Antiparallel

Adjacent β-strands can form hydrogen bonds in antiparallel, parallel, or mixed arrangements.

Crick's access to Franklin's progress report of late 1952 is what made Crick confident that DNA was a double helix with antiparallel chains, but there were other chains of reasoning and sources of information that also led to these conclusions.

During their model building, Crick and Watson learned that an antiparallel orientation of the two nucleotide chain backbones worked best to orient the base pairs in the centre of a double helix.

Finally, an individual strand may exhibit a mixed bonding pattern, with a parallel strand on one side and an antiparallel strand on the other.

In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand: the strands are antiparallel.

Judson describes how Watson spent a large amount of time ignoring Crick's belief (based on Franklin's determination of the space group) that the two backbone strands were antiparallel.

So two vectors : and : are equal if : Opposite, parallel, and antiparallel vectors Two vectors are opposite if they have the same magnitude but opposite direction.

So two vectors : and : are opposite if : Two vectors are parallel if they have the same direction but not necessarily the same magnitude, or antiparallel if they have opposite direction but not necessarily the same magnitude.

The N-terminal two helices are antiparallel and the longer C-terminal helix is roughly perpendicular to the axes established by the first two.

The peptide backbone dihedral angles (φ, ψ) are about (–140°, 135°) in antiparallel sheets.

The secondary structure of a β-sheet can be described roughly by giving the number of strands, their topology, and whether their hydrogen bonds are parallel or antiparallel.

The β-meander motif from the outer surface Protein A β-meander motif A simple supersecondary protein topology composed of 2 or more consecutive antiparallel β-strands linked together by hairpin loops.

Two of these dimer structures then join side by side, in an antiparallel arrangement, to form a tetramer called a protofilament.