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- Wirtschaftsingenieurwesen (25) (entfernen)
Bone morphogenetic protein 2 (BMP21) is a highly interesting therapeutic growth factor due to its strong osteogenic/osteoinductive potential. However, its pronounced aggregation tendency renders recombinant and soluble production troublesome and complex. While prokaryotic expression systems can provide BMP2 in large amounts, the typically insoluble protein requires complex denaturation-renaturation procedures with medically hazardous reagents to obtain natively folded homodimeric BMP2. Based on a detailed aggregation analysis of wildtype BMP2, we designed a hydrophilic variant of BMP2 additionally containing an improved heparin binding site (BMP2-2Hep-7M). Consecutive optimization of BMP2-2Hep-7M expression and purification enabled production of soluble dimeric BMP2-2Hep-7M in high yield in E. coli. This was achieved by a) increasing protein hydrophilicity via introducing seven point mutations within aggregation hot spots of wildtype BMP2 and a longer N-terminus resulting in higher affinity for heparin, b) by employing E. coli strain SHuffle® T7, which enables the structurally essential disulfide-bond formation in BMP2 in the cytoplasm, c) by using BMP2 variant characteristic soluble expression conditions and application of L-arginine as solubility enhancer. The BMP2 variant BMP2-2Hep-7M shows strongly attenuated although not completely eliminated aggregation tendency.
The adsorption and reaction of the amino acid glycine (NH2-CH2-COOH) are studied experimentally on the polar single crystal surface of zinc oxide, ZnO(000-1), by X-ray photoelectron spectroscopy (XPS) under UV light in presence and absence of molecular O2. Deposition at 350 K mainly resulted in a largely deprotonatedmonolayer (NH2-CH2-COO−(a)+OH(s); where O is surface oxygen,(a)is for adsorbed and(s)is for surface species) identified by its XPS C1s binding energy at 289.3 eV (-COO), 286.7 eV (-CH2-) and XPS O1s at 531.8 eV(-COO). A decrease in the signals of all functional groups of the adsorbed glycine (monitored by their C1s, O1s,and N1s lines) is seen upon UV excitation in the absence and presence of O2pressures up to 5 × 10−6 mbar. The photoreaction cross sections extracted from the decrease in the C1s peaks were found to be =2.6 × 10−18(COO(a)) and 1.4 × 10−18(-CH2-)cm^2. The photoactivity of the ZnO(000-1) surface under UHV-conditions is found to be comparable to that seen in direct photolysis of amino acids in solution.
Preparation, catalytical activity and crystal structure of a heptanuclear zinc acetate cluster
(2017)
The one-phonon inelastic low energy helium atom scattering theory is adapted to cases where the target monolayer is a p(1x1) commensurate square lattice. Experimental data for para-H2/NaCl(001) are re-analyzed and the relative intensities of energy loss peaks in the range 6 to 9 meV are determined. The case of the H2/NaCl(001) monolayer for 26 meV scattering energy is computationally challenging and difficult because it has a much more corrugated surface than those in the previous applications for triangular lattices. This requires a large number of coupled channels for convergence in the wave-packet-scattering calculation and a long series of Fourier amplitudes to represent the helium-target potential energy surface. A modified series is constructed in which a truncated Fourier expansion of the potential is constrained to give the exact value of the potential at some key points and which mimics the potential with fewer Fourier amplitudes. The shear horizontal phonon mode is again accessed by the helium scattering for small misalignment of the scattering plane relative to symmetry axes of the monolayer. For 1° misalignment, the calculated intensity of the longitudinal acoustic phonon mode frequently is higher than that of the shear horizontal phonon mode in contrast to what was found at scattering energies near 10 meV for triangular lattices of Ar, Kr, and Xe on Pt(111).