scissions

Scission is the act of cutting or breaking a chemical bond or structural linkage, resulting in fragmentation of a molecule, polymer, or larger assembly. In scientific usage, scission denotes bond cleavage rather than complete dissolution, and the term is common across chemistry, materials science, biology, and physics.

In chemistry and materials science, bond scission can be homolytic, yielding two radicals with one electron from the broken bond, or heterolytic, yielding charged species. Scission can be initiated thermally, photochemically, electrochemically, or enzymatically. In polymers, chain scission reduces molecular weight and can be a mechanism of degradation; crosslink scission can alter mechanical properties. Depolymerization often proceeds through selective scission at specific bonds (e.g., glycosidic or carbon–carbon bonds).

In biochemistry, scission describes cleavage within biomolecules. Proteolytic scission refers to the enzymatic cleavage of peptide bonds by proteases. Other examples include glycosidic bond scission in polysaccharides, and nucleotide bond cleavage in nucleic acids under certain conditions. In cell biology, the term is sometimes used to describe the division or separation of cellular components, such as mitochondrial division (scission) or cytokinesis in cell division, though more precise terms may be used depending on context.

In nuclear physics, scission commonly refers to the point at which a heavy nucleus splits (fission), producing two fragments and energy release. The scission configuration affects fragment masses and kinetic energies and is a subject of theoretical modeling and experimental study.

Across disciplines, scission thus denotes the breakdown of bonds or connections that yields smaller units from larger structures.