| 1. |
- Flyborg, Lena, et al.
(författare)
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A PLS model for predicting rejection of trace organic compounds by nanofiltration using treated wastewater as feed
- 2017
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Ingår i: Separation and Purification Technology. - : Elsevier. - 1383-5866 .- 1873-3794. ; 174, s. 212-221
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Tidskriftsartikel (refereegranskat)abstract
- In this study a Partial Least Squares Projection of Latent Structures (PLS) model has been developed for predicting the rejection of pharmaceutical residuals by nanofiltration (NF) using treated municipal wastewater as feed. The objective was to provide a practical tool for wastewater reuse facilities for estimating the rejection of emerging organic contaminants based on their physiochemical characteristics. The model was developed by identifying the important physiochemical properties of pharmaceutical residuals for rejection by NF. The investigated pharmaceuticals were those present in the effluent from Henriksdal wastewater treatment plant (WWTP), Sweden. The rejection, at volume reduction factors (VRF) ranging from 2 to 20, was examined in a NF pilot plant at two occasions. The important variables for rejection by NF were, in descending order: polarizability, globularity, ratio hydrophobic to polar water accessible surface area and compound charge. Two studies were performed with a time interval of about a year with different wastewater matrices and age of membranes. For different VRFs, but in the same study, the model produced consistent predicted rejections. For the same VRF, but in the different studies, the regression lines were almost parallel, but with a deviation of about 7% for the predicted values. Most of the compounds were within the 95% prediction interval. The model also proved to be able to predict rejection using data from the literature. This confirms that the predictive PLS model can estimate the rejection albeit, with limitations. Generally the proposed predictive rejection model is most likely valid but the model coefficients need to be determined for each individual WWTP or wastewater reuse facility.
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| 2. |
- Wallqvist, A., et al.
(författare)
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A simplified amino acid potential for use in structure predictions of proteins
- 1994
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Ingår i: Proteins: Structure, Function and Bioinformatics. - : Wiley. - 0887-3585 .- 1097-0134. ; 18:3, s. 267-280
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Tidskriftsartikel (refereegranskat)abstract
- A simplified description and a corresponding force field for polypeptides is introduced. Each amino acid residue is reduced to one interaction site, representing the backbone, and one or two side chain sites depending on its size and complexity. Site–site interactions are parameterized after a hydrophobicity criterium. The treatment of backbone sites is in addition designed to reproduce typical polypeptide hydrogen bonding patterns, as well as yielding conformations in accord with the allowed ϕ and ψ angles through an effective angle potential. There are no explicit charges in the model. The derived energy functions, which are based on thermodynamic data and sterical consideration of allowed backbone conformations, correspond to the introduction of an effective potential. The model is tested on two small proteins, avian pancreatic polypeptide and a parathyroid hormone‐related protein, by simulating folding from an initially extended state using Monte Carlo methods. The reduced amino acid description is able to satisfactorily reproduce the experimentally determined native structures.
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| 3. |
- Walse, B, et al.
(författare)
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Structure of a cyclic peptide with a catalytic triad, determined by computer simulation and NMR spectroscopy
- 1996
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Ingår i: Journal of Computer-Aided Molecular Design. - 0920-654X. ; 10:1, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- We report the design of a cyclic, eight-residue peptide that possesses the catalytic triad residues of the serine proteases. A manually built model has been relaxed by 0.3 ns of molecular dynamics simulation at room temperature, during which no major changes occurred in the peptide. The molecule has been synthesised and purified. Two-dimensional NMR spectroscopy provided 35 distance and 7 torsion angle constraints, which were used to determine the three-dimensional structure. The experimental conformation agrees with the predicted one at the beta-turn, but deviates in the arrangement of the disulphide bridge that closes the backbone to a ring. A 1.2 ns simulation at 600 K provided extended sampling of conformation space. The disulphide bridge reoriented into the experimental arrangement, producing a minimum backbone rmsd from the experimental conformation of 0.8 A. At a later stage in the simulation, a transition at Ser3 produced more pronounced high-temperature behaviour. The peptide hydrolyses p-nitrophenyl acetate about nine times faster than free histidine.
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