8 research outputs found
Enzyme activity and dynamics in near-anhydrous conditions
Water is widely assumed to be essential for life 1, although the exact molecular basis of this requirement is unclear 2-4. Water facilitates protein motions 5-9 and although enzyme activity has been demonstrated at low hydrations in organic solvents 10-13, such non-aqueous solvents may allow the necessary motions for catalysis. To examine enzyme function in the absence of solvation and bypass diffusional constraints we have tested the ability of an esterase to catalyse alcoholysis as an anhydrous powder, using a closed reaction system in which the substrates and products of the enzyme reaction are gaseous 14-15, and where the water content can be well defined 16. At hydrations equivalent to 3 (±2) molecules of water per molecule of enzyme, activity is observed that is several orders of magnitude greater than non-enzymatic catalysis. Neutron spectroscopy indicates that the fast (≤nanosecond) global anharmonic dynamics of the anhydrous functional enzyme are heavily suppressed. The results indicate that neither hydration water nor the solvent-activated fast anharmonic dynamics are required for enzyme function. An implication of these results is that one of the essential requirements of water for life may lie with its role as a diffusion medium rather than any of its more specific properties
Population Transfer to a Predissociating Target State Using Pulsed Coherent Excitation: Sensitivity to Coupling to Background States †
Sensitivity of the Extended STIRAP Method of Selective Population Transfer to Coupling to Background States †
Low frequency enzyme dynamics as a function of temperature and hydration: A neutron scattering study
The effect of hydration and temperature on the low-frequency dynamics of the enzyme Pig liver esterase has been investigated with incoherent neutron scattering experiments. The results suggest that at low temperature, increasing hydration results in lower flexibility of the protein. At higher temperatures, systems containing sufficient number of water molecules interacting with the protein exhibit increased flexibility. The environmental force constants indicate that the environment of the protein is more rigid below than it is above the dynamical transition temperature
REACH Coarse-Grained Normal Mode Analysis of Protein Dimer Interaction Dynamics
The REACH (realistic extension algorithm via covariance Hessian) coarse-grained biomolecular simulation method is a self-consistent multiscale approach directly mapping atomistic molecular dynamics simulation results onto a residue-scale model. Here, REACH is applied to calculate the dynamics of protein-protein interactions. The intra- and intermolecular fluctuations and the intermolecular vibrational densities of states derived from atomistic molecular dynamics are well reproduced by the REACH normal modes. The phonon dispersion relations derived from the REACH lattice dynamics model of crystalline ribonuclease A are also in satisfactory agreement with the corresponding all-atom results. The REACH model demonstrates that increasing dimer interaction strength decreases the translational and rotational intermolecular vibrational amplitudes, while their vibrational frequencies are relatively unaffected. A comparative study of functionally interacting biological dimers with crystal dimers, which are formed artificially via crystallization, reveals a relation between their static structures and the interprotein dynamics: i.e., the consequence of the extensive interfaces of biological dimers is reduction of the intermonomer translational and rotational amplitudes, but not the frequencies
Activity and Dynamics of an Enzyme, Pig Liver Esterase, in Near-Anhydrous Conditions
Water is widely assumed to be essential for life, although the exact molecular basis of this requirement is unclear. Water facilitates protein motions, and although enzyme activity has been demonstrated at low hydrations in organic solvents, such nonaqueous solvents may allow the necessary motions for catalysis. To examine enzyme function in the absence of solvation and bypass diffusional constraints we have tested the ability of an enzyme, pig liver esterase, to catalyze alcoholysis as an anhydrous powder, in a reaction system of defined water content and where the substrates and products are gaseous. At hydrations of 3 (±2) molecules of water per molecule of enzyme, activity is several orders-of-magnitude greater than nonenzymatic catalysis. Neutron spectroscopy indicates that the fast (≤nanosecond) global anharmonic dynamics of the anhydrous functional enzyme are suppressed. This indicates that neither hydration water nor fast anharmonic dynamics are required for catalysis by this enzyme, implying that one of the biological requirements of water may lie with its role as a diffusion medium rather than any of its more specific properties