= Glucuronate
<Glucuronate> is the <conjugate base> of <glucuronic acid>, formed by losing the proton of its <carboxyl group>. In the usual D series, the free monomer has <molecular formula> $\mathrm{C_6H_9O_7^-}$, compared with $\mathrm{C_6H_{10}O_7}$ for the neutral acid. A six-membered-ring example is D-glucopyranuronate, whose official chemical record includes both alpha and beta anomers.<D-glucopyranuronate in ChEBI>[CHEBI:58720, Definition, Formula, net charge and ontology]{ref}
Protonation and anomeric configuration answer different questions. Removing a carboxyl proton changes charge; selecting alpha rather than beta specifies the arrangement at the anomeric center. Neither operation is the carbon-5 <epimerization> that distinguishes the glucuronate and <iduronate> series.
The <Henderson-Hasselbalch equation> quantifies the acid–base distinction. In an ideal dilute solution, $[\mathrm{A^-}]/[\mathrm{HA}]=10^{\mathrm{pH}-\mathrm{p}K_a}$. At a pH two units above the relevant $\mathrm{p}K_a$, the ratio is $100:1$, giving an anionic fraction $100/101\approx99\%$. This example uses an offset from the dissociation constant rather than assigning an unverified numerical value to it.
Biological names often refer to glucuronate residues inside a <polysaccharide>. Such a linked residue must be distinguished from a free monomer when counting atoms or preparing a reaction balance.
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