Ab initio molecular dynamics simulation of a medium-sized water cluster anion: from an interior to a surface-located excess electron via a delocalized state

We present a computational study of the structure and dynamics of an excess electron in a medium-sized water cluster aimed at addressing the question of interior vs exterior solvation. Ab initio Born-Oppenheimer molecular dynamics simulations were performed within the DFT framework, employing a hybrid Gaussian and plane-wave formalism together with the PBE exchange-correlation functional and norm-conserving pseudopotentials. Analysis of a 15-ps trajectory allowed us to reach the following conclusions: (i) the excess electron is predominantly located at the cluster surface (even if it is initially placed in the interior), (ii) the computed electron binding energies correlate with the electron localization rather than with its bulk vs surface location, and (iii) a dynamical interconversion between two different H-bond patterns around the electron occurs. The computed electron binding energies and the most relevant features of the IR spectrum are in a very good agreement with results of previous experimental studies.     

Site-specific labeling of DNA-protein conjugates by means of expressed protein ligation

Site-specific bioconjugation of protein thioesters with a DNA oligonucleotide was achieved by Expressed Protein Ligation (EPL) and the new thiol group formed upon EPL in the conjugate was selectively coupled with small molecule labels using maleimide chemistry.