betasheets

Betasheets are a type of protein secondary structure composed of beta strands aligned side by side to form a sheet, stabilized by hydrogen bonds between the backbone atoms. Beta strands are extended polypeptide chains that adopt dihedral angles characteristic of the beta conformation. These strands can align in parallel (N-terminus to N-terminus) or antiparallel (N- to C-terminus) fashions, producing sheets that are flat or slightly twisted.

In antiparallel sheets, hydrogen bonds between adjacent strands are nearly linear, while parallel sheets feature angled hydrogen bonds. The orientation affects local geometry and stability but both forms create a shared backbone hydrogen-bonding network that holds the sheet together. Beta sheets can be found in many protein folds, ranging from compact globular domains to larger fibrous or membrane-associated structures. They may form versatile motifs such as beta barrels in membrane proteins or contribute to mixed alpha/beta domains.

Short loops, known as beta turns or hairpins, connect consecutive strands and enable tight, irregular packing. Hydrophobic residues often face the interior of a sheet, supporting a hydrophobic core, while polar residues may participate in surface interactions or hydrogen bonding.

Beta-sheet-rich regions are also associated with aggregation in disease. Extensive cross-beta structures are characteristic of amyloid fibrils implicated in conditions such as Alzheimer’s disease and other neurodegenerative disorders. Studying beta sheets involves techniques such as X-ray crystallography, nuclear magnetic resonance, and circular dichroism, as well as computational prediction and modeling.