[Preoperative accuracy of selective laser sintering (SLS) in craniofacial 3D modeling: comparison with patient CT data]. / Präoperative Genauigkeit von kraniofazialen, in selektiver Lasersinterung-Technik gefertigten 3-D-Modellen, im Vergleich zum primären CT-Datensatz.

PURPOSE: To evaluate the accuracy of craniofacial 3D models produced in the standardized selective laser sintering (SLS) technique from multislice computed tomography (MSCT) data sets in comparison with patient data and to investigate the effect of potential causes of inaccuracies. MATERIALS AND METHODS: 19 models were considered and examined by MSCT. The patient CT data used for 3D modeling was analyzed and compared to the 3D model data. 15 anatomical landmarks were defined and 20 distances were digitally measured. The digital measurements of both CT data sets were compared to manually measured distances of the SLS model. RESULTS: There was not a statistically significant difference (p < 0.05) between the measurements of the distances concerning all three groups (patient CT data, model CT data, manual measurement of the model). The mean values of the differences were between 0.5455 and -0.3214 mm. CONCLUSION: We found a high accuracy of SLS 3D models, which is due to a high precision in the modeling process and to the small voxel size of patient CT data achieved by MSCT. Anatomical landmarks in patient and model CT data sets and on the 3D model were able to be accurately reproduced, which is important for preoperative planning.

Model-based characterization of an amino acid racemase from Pseudomonas putida DSM 3263 for application in medium-constrained continuous processes.

The amino acid racemase with broad substrate specificity from Pseudomonas putida DSM 3263 was overproduced and characterized with respect to application in an integrated multi-step process (e.g., dynamic kinetic resolution) that--theoretically--would allow for 100% chemical yield and 100% enantiomeric excess. Overexpression of the racemase gene in Escherichia coli delivered cell free extract with easily sufficient activity (20-50 U mg(-1) total protein) for application in an enzyme membrane reactor (EMR) setting. Model-based experimental analysis of a set of enzyme assays clearly indicated that racemization of the model substrates D- or L-methionine could be accurately described by reversible Michaelis-Menten kinetics. The corresponding kinetic parameters were determined from progress curves for the entire suitable set of aqueous-organic mixtures (up to 60% methanol and 40% acetonitrile) that are eligible for an integrated process scheme. The resulting kinetic expression could be successfully applied to describe enzyme membrane reactor performance under a large variety of settings. Model-based calculations suggested that a methanol content of 10% and an acetonitrile content of 20% provide maximum productivity in EMR operations. However product concentrations were decreased in comparison to purely aqueous operation due to decreasing solubility of methionine with increasing organic solvent content. Finally, biocatalyst stability was investigated in different solvent compositions following a model-based approach. Buffer without organic content provided excellent stability at moderate temperatures (20-35 degrees C) while addition of 20% acetonitrile or methanol drastically reduced the half-life of the racemase.