Definitions

from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Of or relating to two adjacent molecules whose sequences of atoms or other elements run in opposite directions.

from The Century Dictionary.

  • Running parallel but in a contrary direction.
  • noun In geometry, one of two or more lines which make equal angles with two other lines, but in contrary order.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective Running in a contrary direction.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective mathematics of vectors, parallel but of opposite direction
  • adjective biochemistry describing the orientations of the two strands of DNA
  • adjective biochemistry describing two beta strands comprising a protein's secondary structure that are aligned and hydrogen bonded but the vector describing the amino- and carboxy-terminal ends of each strand are oriented 180° relative to one another.
  • noun geometry A line that forms equal angles with two other lines, but in opposite directions.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective (especially of vectors) parallel but oppositely directed

Etymologies

from Wiktionary, Creative Commons Attribution/Share-Alike License

anti- +‎ parallel

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Examples

  • In most organisms, DNA is formed as a very long and very narrow double-helix formation of two DNA strands coiled around each other in a head-to-toe "antiparallel" orientation.

    Citizendium, the Citizens' Compendium - Recent changes [en] 2009

  • In most organisms, DNA is formed as a very long and very narrow double-helix formation of two DNA strands coiled around each other in a head-to-toe "antiparallel" orientation.

    Citizendium, the Citizens' Compendium - Recent changes [en] 2009

  • July 30, 2009 at 8:39 am the kittehs reminds me two electrons with all quantum numbers same except the spin parallel and antiparallel

    MIRROR KITTEH - Lolcats 'n' Funny Pictures of Cats - I Can Has Cheezburger? 2009

  • For example, noting that in Watson-Crick base pairing the paired bases have the same face-orientation in forming the antiparallel double helix tells us much of what we need to know to build the correct structure.

    Irwin Rose - Autobiography 2005

  • The model predicts that these electrons are close enough together that the unpaired electron spin states can undergo transition, at some frequency, from antiparallel to parallel spin states (singlet-triplet intersystem crossing).

    PLoS Biology: New Articles 2009

  • Therefore, the nuclear spin magnetic moment vector is either parallel or antiparallel to the nuclear spin angular momentum vector.

    Citizendium, the Citizens' Compendium - Recent changes [en] 2009

  • In one aspect the method involves: (a) determining a first nucleotide sequence of a first nucleic acid coding for the biosynthesis of at least a portion of the original peptide or protein; (b) ascertaining a second nucleotide sequence of a second nucleic acid which base-pairs with the first nucleotide sequence of the first nucleic acid, the first and second nucleic acids pairing in antiparallel directions; and

    California Literary Review 2009

  • Therefore, the nuclear spin magnetic moment vector is either parallel or antiparallel to the nuclear spin angular momentum vector.

    Citizendium, the Citizens' Compendium - Recent changes [en] 2009

  • Xu et al. expressed Cre-fragments fused to antiparallel leucine-zipper peptides in the pancreas using the same Pdx1-promoter for both fragments

    PLoS ONE Alerts: New Articles 2009

  • E1 and E2 are thought to be class II fusion proteins because the putative fusion peptide is supposedly localized in an internal sequence linked by antiparallel β-sheets

    PLoS ONE Alerts: New Articles 2009

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