Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In an accurately determined X-ray diffraction study of the thyroid hormone thyroxine (T4), the two independent conformations in the crystal lattice show significant differences in the outer phenyl ring geometry when compared with that of 3,5,3'-triiodothyronine (T3). The major differences between the T4 and T3 structures are a shortened C4'-O4' bond, contraction of the C3'-C4'-C5' angle and an increase in the C3' and C5' angles of T4. These changes can be correlated with the difference in acidity of the 4'-OH of T4 and T3 and help to explain binding affinity differences among thyroactive compounds. The hydrogen bond directionality observed in T4 and other thyroid structures offers an insight into the molecular details of the hormone-receptor site. The conformation of one T4 molecule is cisoid, that of the other transoid, the first such instance of different overall conformations to be found in the same crystal lattice. One T4 molecule has the side chain nearly coplanar with the inner ring, an unusual conformation among thyroid structures.
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PMID:Molecular conformation of thyroid hormones: structure and binding interactions of thyroxine. 51 Feb 17

In order to assist with the development of more selective and sensitive methods for thyroid hormone analysis the [M-H]- anions of the iodothyronines T4, T3, rT3, (3,5)-T2 and the non-iodinated thyronine (T0) have been generated by negative ion electrospray mass spectrometry. Tandem mass spectra of these ions were recorded on a triple-quadrupole mass spectrometer and show a strong analogy with the fragmentation pathways of the parent compound, tyrosine. All iodothyronines also show significant abundances of the iodide anion in their tandem mass spectra, which represents an attractive target for multiple reaction monitoring (MRM) analysis, given that iodothyronines are the only iodine bearing endogenous molecules. Characteristic fragments are observed at m/z 359.7 and 604.5 for rT3 but are absent in the spectrum of T3, thus differentiating the two positional isomers. The striking difference in the fragmentation patterns of these regioisomeric species is attributed to the increased acidity of the phenol moiety in rT3 compared with T3.
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PMID:Tandem mass spectrometry of deprotonated iodothyronines. 1602 13