Stephen C. Chmely and Kevin M. Williams
The reaction of L-selenomethionine (SeMet) with several platinum complexes has been studied using 1H and 195Pt NMR spectroscopy. When SeMet is reacted with [Pt(dien)Cl]Cl, [Pt(dien)(SeMet-Se)]2+ is the expected product; however, two signals that correspond to the methyl group of SeMet are observed, suggesting slow exchange between two chiralities at the Se atom. One 195Pt NMR resonance was observed; to our knowledge, this is the first reported 195Pt NMR shift of a molecule containing a Pt-Se bond. Reaction of SeMet with [Pt(Me4en)(D2O)2]2+ results in two signals which are thought to correspond to [Pt(Me4en)(SeMet-Se,N)]+ products. When [Pt(dien)Cl]Cl is reacted with a mixture of methionine (Met) and SeMet, reaction with SeMet is kinetically favored. After several days, a mixture of [Pt(dien)(SeMet-Se)]2+ and [Pt(dien)(Met-S)]2+ is observed, indicating that Met can displace SeMet.Thus, although only a subset of proteins have selenium-containing amino acids, platinum complexes could target them kinetically.