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Constant KD (constant + kd)
Selected AbstractsMicrospheres Sensor Based on Molecularly Imprinted Polymer Synthesized by Precipitation PolymerizationCHINESE JOURNAL OF CHEMISTRY, Issue 5 2003Zhang Zhao-Hui Abstract A new biomimetic bulk acoustic wave sensor based on molecularly imprinted microspheres (MIM) technique was described. The sensing materials were synthesized by precipitation polymerization. By using the Scatchard analysis, the equilibrium dissociation constant KD and the apparent maximum number Qmax of the binding sites were calculated to be 3.70 mmol·L,1 and 9.11 ,mol·g,1, respectively. The sensor exhibited a sensitive response to the template compound (dipyridamole) in liquid phase with a detection limit of 2 × 10,9 mol· L,1. The recoveries of the sensor were 95.1%-105.4%. Studies presented in this paper show that the stability of this sensor is excellent. The sensor has been applied successfully to the determination of dipyridamole in human urine. [source] Identification of calreticulin as a ligand of GABARAP by phage display screening of a peptide libraryFEBS JOURNAL, Issue 21 2007Jeannine Mohrlüder 4-Aminobutyrate type A (GABAA) receptor-associated protein (GABARAP) is a ubiquitin-like modifier implicated in the intracellular trafficking of GABAA receptors, and belongs to a family of proteins involved in intracellular vesicular transport processes, such as autophagy and intra-Golgi transport. In this article, it is demonstrated that calreticulin is a high affinity ligand of GABARAP. Calreticulin, although best known for its functions as a Ca2+ -dependent chaperone and a Ca2+ -buffering protein in the endoplasmic reticulum, is also localized to the cytosol and exerts a variety of extra-endoplasmic reticulum functions. By phage display screening of a randomized peptide library, peptides that specifically bind GABARAP were identified. Their amino acid sequences allowed us to identify calreticulin as a potential GABARAP binding protein. GABARAP binding to calreticulin was confirmed by pull-down experiments with brain lysate and colocalization studies in N2a cells. Calreticulin and GABARAP interact with a dissociation constant Kd = 64 nm and a mean lifetime of the complex of 20 min. Thus, the interaction between GABARAP and calreticulin is the strongest so far reported for each protein. [source] Deactivation of Formate Dehydrogenase (FDH) in Solution and at Gas-Liquid InterfacesBIOTECHNOLOGY PROGRESS, Issue 6 2005Andreas S. Bommarius Enzymes, increasingly important in the synthesis of fine chemicals and pharmaceutical intermediates, are often insufficiently stable under reacting conditions. We have investigated the stability, in homogeneous aqueous solution and at gas-liquid interfaces, of formate dehydrogenase (FDH), important for cofactor regeneration, from Candida boidinii and overexpressed in E. coli. When exposed to mechanical stress, residual activity, [E]t/[E]0, and residual protein were found to scale proportionally with gas-liquid surface area in the bubble column, verifying a surface-driven process, and with time and total throughput in a gear pump, but did not seem to be influenced much by shear in a Couette viscometer. All FDH variants are deactivated by chaotropes but not kosmotropes: the first-order deactivation constant kd correlates well with the Jones-Dole coefficient B but not well with the surface tension increment ,, of various concentrated ammonium salt solutions. This finding might provide guidance for focusing the search for quantitative theories of Hofmeister effects. [source] New ,-amino phenylalanine tetrazole ligand for immobilized metal affinity chromatography of proteinsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 16-17 2008Genhu Lei Abstract A new chelating compound has been developed for use in the immobilized metal affinity chromatographic (IMAC) separation of proteins. The bidentate ligand, ,-amino phenylalanine tetrazole, 4, was synthesized via a five-step synthesis from N -fluorenylmethoxycarbonyl phenylalanine and then immobilized onto silica through the epoxide coupling procedure. The binding behavior of the resulting IMAC sorbent, following chelation with Zn2+ to a density of 183 ,mol Zn2+ ions/g silica, was characterized by the retention of proteins in the pH range of 5.0,8.0, and by the adsorption behavior of lysozyme with frontal chromatography at pH 6.0 and 8.0. The prepared column showed the separation ability to four test proteins and the retention time of these proteins increased with an increase in pH. From the derived isotherms, the adsorption capacity, qm, for the binding of lysozyme to immobilized Zn2+ -,-amino phenylalanine tetrazole,silica was found to be 1.21 ,mol/g at pH 6.0 and 1.20 ,mol/g sorbent at pH 8.0, respectively, whilst the dissociation constants KD at these pH values were 5.22×10,6 and 3.49×10,6 M, respectively, indicating that the lysozyme was retained more stable under alkaline conditions, although the binding capacity in terms of micromole protein per gram sorbent remained essentially unchanged. [source] | ||||||||||