Artificial metalloenzymes result from anchoring an active catalyst within a protein environment. Towards this goal, various localization strategies have been pursued: covalent-, supramolecular-or dative anchoring. Herein we show that introduction of a suitably positioned histidine residue contributes to firmly anchor via a dative bond a biotinylated rhodium pianostool complex within streptavidin. The in-silico design of the artificial metalloenzyme was confirmed by X-ray crystallography. The resulting artificial metalloenzyme displays significantly improved catalytic performance, both in terms of activity and selectivity in the transfer hydrogenation of imines. Depending on the position of the histidine residue, both enantiomers of the salsolidine product can be obtained.

Efficient calculation of the properties of metal-containing complexes relevant to catalysis is of major interest for better characterizing and optimizing the catalysts. For this, a new force field, called VALBOND-TRANS here, is proposed. It is based on the existing VALBOND force field of Landis and co-workers, extended by adding terms that account for electronic effects such as the trans influence of ligands on bond lengths and relative energies. Parameters and results for model octahedral complexes of Ru, Os, Rh, and Ir are determined and discussed. The model is then applied to the study of reactive intermediates involved in asymmetric hydrogenation catalyzed by iridium complexes with chiral phosphinooxazolines (PHOX) ligands. The new force field explores and capitalizes on the separation of electronic and steric effects on the stability of different diastereomers and reproduces DFT results which are consistent with experimental observations.

Arylsulfonamide derivatives are widely studied high affinity inhibitors of the isozyme human carbonic anhydrase II (hCA II). From molecular dynamics simulations and MM-GBSA calculations, reliable (R ¼ 0.89) relative binding free energies are determined for 17 previously experimentally characterized protein-ligand complexes. Decomposition of these energies led to the identification of critical amino acid residues with a significant contribution to the affinity towards the ligands. In particular, Leu198 was predicted as a key residue and was subjected to computational mutagenesis. This prediction was verified experimentally by producing hCA II mutants L198A, L198F and L198Q and determining the resulting affinities towards inhibitor 1. The computed vs. experimental energies are in good agreement thus suggesting that the force field parameters reported herein are useful for the in silico design of a wider range of carbonic anhydrase inhibitors.

Among natural metalloenzymes, the facial two-histidines one-carboxylate binding motif (FTM) is a widely represented first coordination sphere motif present in the active site of a variety of metalloenzymes. A PDB search revealed a total of 1685 structures bearing such FTMs bound to a metal. Sixty statistically representative FTMs were selected and used as template for the identification of structurally characterized proteins bearing these three amino acids in a propitious environment for binding to a transition metal. This geometrical superposition search, carried out using the STAMPS software, returned 2320 hits. While most consisted of either apo-FTMs or bore strong sequence homology to known FTMs, seven such structures lying within a cavity were identified as novel and viable scaffolds for the creation of artificial metalloenzymes bearing an FTM.

The implementation, validation, and application of the multi-state VALBOND method for transition-metal-containing and hypervalent molecules are presented. This approach is particularly suited for molecules with unusual shapes and systems that need to be described by a superposition of resonance structures, each of which satisfies the octet rule. The implementation is based on the original VALBOND force field and allows us to smoothly switch between resonance structures, each of which can be characterized by its own force field, including varying charge distributions and coupling terms between the states. The implementation conserves total energy for simulations in the gas phase and in solution and is applied to a number of topical systems. For the small hypervalent molecule ClF, the barrier for pseudorotation is found to be 4.3 kcal/mol, which compares favorably with the experimentally measured value of 4.8 kcal/mol. A transition-metal-containing complex, cisplatin, is characterized by six resonance states, for which the vibrational spectrum is found to be in good agreement with experiment. Finally, umbrella sampling simulations of the S2 reaction BrMe + Cl → Br + MeCl in solution yield a barrier height of 24.6 kcal/mol, in good agreement with experiment (24.7 kcal/mol).