antiparallel

1. (of vectors) Parallel but in opposite directions.
   1. not comparablebiochemistryDescribing the orientations of the two strands of DNA.

      Upon interaction with ss- nucleic acid (NA) targets (deoxyribooligonucleotides (ODNs) or ribooligonucleotides), they form very stable anti-parallel and parallel duplexes [3 ], and the melting temperatures of the antiparallel duplexes are 10 to 15°C higher than those of the parallel duplexes.

      2015 October 16, “Polyanionic Carboxyethyl Peptide Nucleic Acids ( ce -PNAs): Synthesis and DNA Binding”, in PLOS ONE, →DOI

   2. not comparablebiochemistryDescribing two beta strands comprising a protein's secondary structure that are aligned and hydrogen bonded but where the vectors describing the amino- and carboxy-terminal ends of each strand are oriented 180° relative to one another.

plural antiparallels

1. geometryA line that forms equal angles with two other lines, but in opposite directions.