The Electric Field Gradient of 111Ag in Macrocyclic Crown Thioethers

Time differential perturbed angular correlation experiments and ab-initio density functional theory calculation were used to determine the electric field gradients of the metal centres of the macrocyclic crown thioethers Ag(15S5)[BF₄], Ag(18S6-CH₂OH)[CF₃SO₃], Ag(18S6)⁺, Ag(19S6-OH)[Tosylat] and Ag(20S6-OH)[CF₃SO₃]. The density functional theory calculations have been performed with the Amsterdam Density Functional code ADF. A “fingerprint system” is introduced, which allows to assign electric field gradients to certain Ag coordinations in these crown thioether complexes.     

Hg-coordination studies of oligopeptides containing cysteine,histidine and tyrosine by 199mHg-TDPAC

In order to study the interaction of histidine- and tyrosine-containing peptide chains with Hg(II), the nuclear quadrupole interaction (NQI) of ^199mHg in the Hg complexes of the oligopeptides Alanyl–Alanyl–Histidyl–Alanyl–Alanine-amid (AAHAA–NH₂) and Alanyl–Alanyl–Tyrosyl–Alanyl–Alanine-amid (AAYAA–NH₂) was determined by time differential perturbed angular correlation and is compared with previous data on Alanyl–Alanyl–Cysteyl–Alanyl–Alanyl (AACAA–OH). The ^199mHg–NQIs depend on the oligopeptide to Hg(II) stoichiometry and indicate that two-fold and four-fold coordinations occur for the bound Hg(II). This revised version was published online in August 2006 with corrections to the Cover Date.