Unconjugated

Unconjugated is an adjective used across disciplines to describe something that has not been joined, linked, or transformed by a particular process. The exact meaning depends on context, but the core idea is the absence of a specified form of combination or modification.

In linguistics, an unconjugated verb form refers to a base form that has not been inflected for person, number, tense, mood, or aspect. In many languages, verbs are conjugated to reflect grammatical features, and the unconjugated form often corresponds to the infinitive or lemma, which serves as a citation form in dictionaries. For example, the English base form "walk" is unconjugated before it is conjugated to "walks," "walking," or "walked."

In chemistry, unconjugated describes a molecule in which p-orbitals do not participate in a conjugated system of alternating double and single bonds across adjacent atoms. Electrons are not delocalized over a chain, which affects properties such as stability, color, and reactivity. This contrasts with conjugated systems, where continuous overlap of p-orbitals allows electron delocalization. Unconjugated motifs often show different reactivity patterns than their conjugated counterparts.

In medicine and biochemistry, unconjugated commonly refers to a form that has not undergone a conjugation reaction. A notable example is unconjugated bilirubin, the bilirubin that has not been glucuronidated in the liver. It is fat-soluble and not readily excreted in urine or bile, and high levels can be clinically significant, particularly in newborns, where they can lead to jaundice or, in severe cases, neurotoxicity. Conjugated bilirubin, in contrast, is water-soluble after glucuronidation and is excreted more readily.