antiparallel

Antiparallel describes a relationship in which components are oriented in opposite directions along a common axis. The term is used across science to denote opposite alignment of molecular segments, magnetic moments, or polymer chains.

In the genetic material, the two strands of the DNA double helix are antiparallel; one runs 5' to 3' while the other runs 3' to 5'. This orientation allows complementary base pairing and is essential for replication and transcription, aligning enzymes with the correct template strand.

In protein structure, antiparallel beta sheets consist of adjacent polypeptide strands running in opposite N- to C- termini. The hydrogen bonds between aligned residues are nearly linear, contributing to stability. This arrangement contrasts with parallel beta sheets, where strands run in the same direction.

In magnetism and materials science, antiparallel alignment describes neighboring magnetic moments pointing in opposite directions. In antiferromagnets, this cancels net magnetization; in multilayer devices and spintronics, antiparallel alignment between layers can determine electrical resistance and switching behavior.

Other contexts: The concept also appears in polymers and crystalline materials where chains or dipoles are oriented opposite along a given axis, influencing mechanical, dielectric, or optical properties.

Overall, antiparallel conveys opposite orientation along a shared axis, with field-dependent implications depending on the material system being described.

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