Myosin is a family of actin-associated motor proteins that couple ATP hydrolysis to mechanical work. Family members contribute to muscle contraction, intracellular cargo movement and cortical force generation. Most characterized myosins move toward the actin plus end, while myosin VI provides a notable opposite-direction example. Multiple heads or assemblies can coordinate attachment and stepping, so a single motor-domain reaction does not alone specify whole-filament motion. ^[ref][ref]

An electron carrier protein in the mitochondrial respiratory chain.

It carries electrons between respiratory complexes through reversible changes in its heme iron. Its release from the mitochondrial intermembrane space also contributes to apoptosis in many animal cells, illustrating distinct functions determined by location. ^[ref]

Aprotinin is a small disulfide-stabilized protein that inhibits selected serine proteases, including trypsin-like enzymes. It illustrates a protein inhibitor that blocks access or productive interaction at a protease active site rather than being a general inhibitor of all proteolysis. Its compact, crosslinked structure also makes it a useful model for studying folding and molecular stability. ^[ref]

A peptide comprises amino acid residues joined through peptide bonds.

Ovalbumin is a major protein of chicken egg white with a storage role. It is distinct from serum albumin despite the related names. Its solubility and abundance make it a convenient experimentally recognized protein, including the historical binding comparison discussed under Papain digestion of IgG. ^[ref]

A globin is a member of a protein family with a characteristic fold commonly supporting a heme group. Hemoglobin and myoglobin provide familiar examples involved in oxygen transport and storage. Similar folds can support different physiological roles, so identifying a globin sequence does not by itself specify an oxygen-transport function. Heme coordination and the surrounding protein environment jointly shape ligand binding. ^[ref]

A whey protein used as a model solute in studies of protein association and transport. Its effective electric charge, association state and hydrodynamic radius depend on solution conditions. In a specified spherical-particle model, its electrophoretic mobility and sedimentation speed depend on its charge and buoyant mass through the same Stokes drag law.

Polymer physics connects the conformations and motion of long molecules to the properties of a material. A polymer can change shape through many segment rotations while its chemical backbone remains intact. This makes the competition between flow and relaxation important: the same chain can behave as a coil in one experiment and an extended object in another. Soft matter includes both these flexible structures and liquid crystals, whose orientational order produces a different route to strong mechanical and optical response.

Polyethylene glycol is a water-soluble polymer with repeating ethylene oxide units. Nonadsorbing dissolved chains can cause a depletion force between larger colloids. Chains attached to a surface can instead give steric stabilization. Which effect occurs depends on surface affinity, chain size and concentration.

A cross-link connects different segments of a polymer network and restricts their independent motion. Permanent chemical cross-links commonly use covalent bonds; physical associations can instead have finite lifetimes. A connected permanent network can sustain long-time shear stress, whereas an uncrosslinked melt eventually flows. Cross-link density and network structure influence elastomer stiffness.

An elastomer is a polymeric material capable of large substantially recoverable deformation. Flexible chain segments supply configurational entropy, while a network of permanent or sufficiently long-lived cross-links prevents unrestricted macroscopic flow on the observation time scale. Its dynamic modulus depends on whether segmental relaxation can follow the imposed deformation. The rubbery plateau and high-frequency glassy response refer to different accessible relaxation regimes.

A biopolymer is a polymer produced by a living system, including proteins, nucleic acids and polysaccharides. Local chemical structure, sequence and interactions can give it stiffness or preferred conformations beyond those of an ideal chain. Biopolymer mechanics uses models such as the worm-like chain and the helix-coil transition model to represent those features.

A polymer with repeat-unit composition ${\mathrm{C}}_5{\mathrm{H}}_8$. Its cis-rich form is the main polymer component of natural rubber.

A silicone is a polymeric material with a silicon-oxygen backbone bearing organic substituents, commonly methyl groups. Polydimethylsiloxane is a familiar example.

Backbone flexibility, side groups, chain length, and crosslinking determine whether the material behaves as a fluid, gel, or elastic solid. Silicone is a polymer family and should be distinguished from elemental silicon and inorganic silicon dioxide.

Collective electric charge rearrangement modifies particle interactions in a plasma. In stellar nuclear fusion, this response can alter the Coulomb barrier used to infer a thermonuclear reaction rate.

A plasmon is a quantum of a collective oscillation of electric charge density in a plasma or conducting material. Long-range Coulomb interaction can give its long-wavelength longitudinal mode a nonzero frequency.

On spatial scales much larger than the Debye length, a plasma may have nearly cancelling positive and negative electric charge densities while still carrying an electric current and having a nonzero electric field. Quasineutrality is an approximation on appropriate slow macroscopic scales, not an assertion that each fluid element has exactly zero charge or that charge separation can be ignored at every boundary.

Endocrinology studies hormones, their production and their effects on target tissues. Feedback, transport, receptor signaling and removal connect gland activity to measured concentrations. A hormone concentration therefore cannot alone reveal every aspect of secretion or tissue responsiveness.

The circulatory system transports blood through the heart and vessels, connecting exchange surfaces with tissues. In humans, pulmonary and systemic pathways operate in series. Pressure gradients drive flow, while the distribution of resistance helps determine how total output is divided among organs.

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