Jens Josephsen

Simulation of laboratory assignments to support students’ learning of introductory inorganic chemistry

The goal of this investigation was to elucidate undergraduate chemistry students’ response to the SimuLab computer-based learning environment, which simulates a 20 hours laboratory assignment. The SimuLab is a cognitive tool designed to help students to acquire experimental and analytical skills on the basis of a classical qualitative and quantitative analysis scheme and to develop their ability to interpret experimental results. Consistent with the intentions behind the design, students seemed to acknowledge the learning potential of the simulation program. They found it motivating and creating attention towards the practical application of declarative knowledge. We also found SimuLab to support students in the accomplishment of cognitive tasks and to enhance their skills in the context of the investigation. [Chem. Educ. Res. Pract., 2006, 7 (4), 266-279]

Phosphate buffer and salt medium concentrations affect the inactivation of t4 phage by platinum(ii) complexes

The initial rate of inactivation of T4 phage by solutions of [Pt(NH3)2Cl2], [PtenCl2] and [Pten(H2O)2] (NO3)2 at fixed values of pH is strongly reduced by phosphate buffer, slightly reduced by acetate buffer and apparently not influenced by bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane (BIS-Tris) buffer and HEPES buffer. The phosphate abolishes the antiphage activity of the platinum complexes probably by some sort of complex formation. This together with dimerization reactions qualitatively explains the tailing off of the phage inactivation rate. High concentrations of NaNO3 as the salt medium give increased phage inactivation rates, which are also strongly pH-dependent.

Platinum(II) complexes block the entry of T4 phage DNA into the host cells

The efficiency of multiplicity reactivation of T4 particles inactivated by platinum(II) complexes is very low. The same is true for marker rescue and functional survival of genes. This can be at least partly explained by the inability of most inactivated virus particles to introduce their DNA into the host cells as demonstrated by electron microscopy. Conformational changes in the DNA, formation of DNA-DNA and DNA-protein cross-links and the damage of proteins participating in the injection process could be responsible for the phenomenon observed.

Hydrolysis of cis-dichlorobis(bipyridyl)-cobalt(III) and -chromium(III) ions, and of their phenanthroline analogues with and without a catalyst

Hydrolysis of the dichlorobis(bipyridyl)-cobalt(III) and -chromium(III) ions and their phenanthroline analogues is slow without a catalyst, but is fast in the presence of the corresponding metal(II) complexes: for the metal(III) complexes the hydrolysis is also base-catalysed, even though a conjugate base mechanism is not possible.