Teobald Kupka

Determination of penicillin complexation sites in the presence of Zn(II) ions by AM1 and PM3 methods

Abstract In this study we have carried out semiempirical AM1 and PM3 calculations on a simplified penicillin molecule (i.e. methylpenicillin) in the presence of the Zn(II) ion to assess the probable complex structures and to gain additional information on the mechanism of the metal-ion promoted hydrolysis of penicillins. Theoretical investigations based on calculated heats of formation Δ H f predict formation of two complexes of comparable thermochemical stability in aqueous solutions of methylpenicillin in the presence of Zn(II): by the COO − group alone and by the COO − group and β-lactam ring nitrogen atom. The former structure, with four watermolecules, is slightly favoured Δ H f lower by 6.5 kcal mol −1 (AM1)and 10.7kcal mol −1 (PM3)). A complex involving binding to the C6 substituent described in some earlier works was not found. The calculated lengthening of the ligand C7-N4 bond upon coordination suggests easier Nu − attack at the β-lactam carbon atom, which facilitates the degradation of penicillin. The results also indicate that both methods can be applied to calculations on penicillins. Generally, the PM3 bond lengths are longer than the AM1 values; however, the former reproduces better the first coordination sphere of the Zn(II) ion.

Copper-d-penicillamine complex as potential contrast agent for MRI

In vitro and in vivo proton T1 data are reported that demonstrate that the paramagnetic copper-D-penicillamine complex can be applied as a potential contrast agent to magnetic resonance imaging.

Simple, rapid and non-destructive detection and determination of phosphines and phosphine oxides in solution by 1H and 31P NMR

SummaryA simple, rapid and non-destructive method for the detection and determination of phosphines and phosphine oxides in solution by 1H and 31P NMR spectroscopy is proposed. Diphenylphosphine (DPP) and diphenylphosphine oxide (DPPO) mixtures in C6D6 chosen as model system were studied in wide ranges of concentration (10−2 to 4 mol/l). The detection of DPP and DPPO in solution by 1H NMR was based on the presence of two doublets (hydrogen directly bonded to phosphorus, HP) originating from P-H and P(O)H groups with one bond coupling constant 1JPH of 216.08 and 476.12 Hz. 31P NMR signals at −40.07 and +18.26 ppm additionally proved the presence of DPP and DPPO in solution. A linear dependence of the measured HP and ortho-proton integral intensity on the concentration of DPP and DPPO was found. The content of DPP and DPPO evaluated by 31P without adding Cr(acac)3 and by 1H NMR agreed with the quoted amounts within 1 to 3%.

Penicillin Action and Metal Ions. IR Studies and Model Semi Empirical Calculations

Azetidin-2-one (four membered β-lactam ring) is the main structural feature of penicillin and cephalosporin antibiotics [1].

Sulfur Ligands. from β-Lactam Antibiotics to Contrast Agents for MRI

Abstract NMR, IR and semi empirical Molecular Orbital PM3 studies on selected β-lactam antibiotics are reported. The role of sulfur in β-lactam antibiotics is discussed.

HR NMR and Semiempirical Calculations on Penicillin and Penicillin — Metal Ion Interaction in Solution

It is believed that the main role played by the β-lactam antibiotics is to disrupt bacterial wall synthesis by inhibiting transpeptydase enzyme (the last stage of the wall synthesis). On the other hand, these antibiotics are easily degraded [1] to inactive penicilloic acid in the presence of β-lactamase enzymes in resistant strains of bacteria or in the presence of traces of divalent metal ions in solution (Zn(II), Cu(II) or Mn(II)). Zinc(II) is also cofactor of the β-lactamase II action [2].