Protonados

Protonados are chemical species that have gained a proton, H+. The protonated form may be neutral or carry a charge; the most common example in analytical chemistry is the positively charged [M+H]+ ion observed in mass spectrometry. In some non-English literature, protonado or protonados are used to denote protonated species, corresponding to the English term protonated.

Formation occurs via transfer of a proton from a donor acid to a base. In solution, protonation depends on pH and the molecule’s pKa; when the pH is below the compound’s pKa, a larger fraction of molecules becomes protonated. In gas phase or during ionization techniques like electrospray, protonation can be induced by proton donors such as hydronium ions or other reagents.

Applications and implications include mass spectrometry, where protonados appear as [M+H]+ ions with m/z equal to the molecular weight plus one and are central to many ionization methods such as electrospray (ESI) and nanoESI. The extent and site of protonation affect fragmentation patterns and detection sensitivity. In biochemistry and pharmacology, the protonation states of functional groups on amino acids and small molecules influence charge, conformation, solubility, and interactions, thereby affecting enzyme activity, binding affinities, and solubility across different pH conditions. Protonation states are thus a key factor in structure, reactivity, and analytical detection of many compounds.