Multiple pH Regime Molecular Dynamics Simulation for pK Calculations

Ionisation equilibria in proteins are influenced by conformational flexibility, which can in principle be accounted for by molecular dynamics simulation. One problem in this method is the bias arising from the fixed protonation state during the simulation. Its effect is mostly exhibited when the ionisation behaviour of the titratable groups is extrapolated to pH regions where the predetermined protonation state of the protein may not be statistically relevant, leading to conformational sampling that is not representative of the true state. In this work we consider a simple approach which can essentially reduce this problem. Three molecular dynamics structure sets are generated, each with a different protonation state of the protein molecule expected to be relevant at three pH regions, and pK calculations from the three sets are combined to predict pK over the entire pH range of interest. This multiple pH molecular dynamics approach was tested on the GCN4 leucine zipper, a protein for which a full data set of experimental data is available. The pK values were predicted with a mean deviation from the experimental data of 0.29 pH units, and with a precision of 0.13 pH units, evaluated on the basis of equivalent sites in the dimeric GCN4 leucine zipper

NeGeV: next generation energy efficient ventilation system using phase change materials

Abstract Product development in the HVAC business segment are continually showing disturbingly slow annual increases in product performance, gradually reducing profitability in the market. Cooling and heating technologies applied in the HVAC industry range from simple natural cooling to more advanced active solutions based on conventional compression technology, but the performance increase is fundamentally incremental. This paper presents the NeGeV project which will provide an innovative solution demonstrating a leap in ventilation systems performance through the use of phase change materials for active heat recovery during periods of cooling needs. The project will develop, design and produce a prototype system and document its performance through certified tests. Through development of intelligent controls for the system, the project will demonstrate the potential for system integration into a smart grid application of load shifting and optimal operation control. In addition, the technical and economic feasibility of the prototype will be evaluated considering an office-space case study