Reduced susceptibility of cells or disease to a chemotherapy regimen. Survival can reflect pre-existing resistant states, induced changes or genetic evolution.

A therapeutic antibody directed against CTLA-4, used as an immune checkpoint inhibitor in defined clinical contexts.

A range of exposures giving useful benefit while keeping adverse effects acceptable. Biochemical target inhibition alone does not establish this range.

Evidence that an intervention interacts with its intended molecular target in the biological setting being tested. A downstream phenotype alone is insufficient.

Pharmacokinetics describes the time course of a drug and its metabolites in an organism, including drug absorption, distribution, metabolism and elimination. A concentration-time curve helps distinguish exposure from response: equal administered amounts can produce different concentrations at the target.

A growth-inhibition assay in which a compound diffuses from a disc into a lawn of biological cells. Halo size combines susceptibility with molecular diffusion and growth conditions and is not directly a molecular binding affinity.

An increased response to a drug relative to a specified control. Cellular hypersensitivity does not uniquely imply higher molecular affinity for the intended target.

A drug effect mediated through an interaction other than the intended target. A residual phenotype after verified protection of the intended target is a useful candidate, but requires independent causal validation.

An organic peroxide that can initiate radical polymerization by O–O bond homolysis. Benzoyloxy radicals, and radicals formed by their further reaction, can initiate monomer addition.

Summing only paths that reflect at one shunt, with all previous shunts crossed once in each direction, gives a geometric series with ratio $t^2{e}^{2ikL}$. This is not the full multiple-reflection solution: it excludes paths that bounce between distinct shunts. For a semi-infinite array the exact amplitude instead obeys $R=r+t^2{e}^{2ikL}R/(1-r{e}^{2ikL}R)$. Near coherent reflection peaks the omitted paths need not be small, even if each shunt is weak.

Interconversion of a conjugated pi system and a ring by formation or cleavage of one sigma bond at the pi-system termini, accompanied by pi-bond redistribution. Terminal rotation connects starting geometry with product stereochemistry.

Orbital-symmetry rules associated with Robert Burns Woodward and Roald Hoffmann for concerted reactions. Ground-state and photochemically excited occupations can have different allowed stereochemical modes; an allowed mode does not determine every kinetic detail or guarantee a large reaction rate.

The reverse of a cycloaddition, splitting a ring into unsaturated fragments.

A pericyclic reaction that relocates a sigma bond while reorganizing an adjacent pi system.

A reaction using the same face of a participating orbital array at both reacting termini.

A tripeptide contains three amino acid residues linked by peptide bonds. Even three residues have an order: Gly-Ala-Ser and Ser-Ala-Gly have the same residue composition but different sequences and terminal environments. Short length does not imply biological inactivity, since small peptides can participate in signalling or chemical protection. Covalent modifications and nonstandard linkages require specification beyond the simple residue count. ^[ref]