betastrands

Betastrands are linear segments of polypeptide chains that adopt a beta-strand conformation, one of the canonical protein secondary structures. When multiple beta-strands align, they form beta sheets stabilized by inter-strand hydrogen bonds between backbone amide and carbonyl groups.

In terms of geometry, beta-strands have backbone dihedral angles typically in the range of phi around -120 degrees and psi around 120 degrees, with side chains alternating above and below the sheet. They can be arranged in parallel or antiparallel orientations; antiparallel sheets have more linear hydrogen bonds, whereas parallel sheets have slightly angled bonds. Short motifs such as beta-hairpins connect adjacent strands via tight turns; longer motifs form extensive beta-sheets and can fold into beta-barrels or warped surfaces.

Betastrands occur throughout globular, membrane, and fibrous proteins. Their presence is inferred from sequence-derived secondary structure predictions and confirmed by structural methods such as X-ray crystallography, nuclear magnetic resonance, and cryo-electron microscopy. In protein folding, beta-strands contribute to the cooperative formation of native structures and can influence stability and aggregation propensity.

In biology and materials science, beta-strand architecture underpins many functional domains and contributes to mechanical properties in fibrous proteins like silk. Misfolding or overextension of beta-strands can lead to amyloid aggregates associated with neurodegenerative diseases. Understanding betastrand formation aids protein design, drug discovery, and the development of beta-sheet–based biomaterials.