Christian Frech

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A large number of different stationary phases for ion-exchange chromatography (IEC) from different manufacturers are available, which vary significantly in a number of chemical and physical properties. As a consequence, binding mechanisms may be different as well. In the work reported here, the retention data of model proteins (alpha-lactalbumin,(More)
A novel cation-exchange resin, Eshmuno™ S, was compared to Fractogel® SO3(-) (M) and Toyopearl GigaCap S-650M. The stationary phases have different base matrices, and carry specific types of polymeric surface modifications. Three monoclonal antibodies (mAbs) were used as model proteins to characterize these chromatographic resins. Results from gradient(More)
The mobile phase pH is a key parameter of every ion exchange chromatography process. However, mechanistic insights into the pH influence on the ion exchange chromatography equilibrium are rare. This work describes a mechanistic model capturing salt and pH influence in ion exchange chromatography. The pH dependence of the characteristic protein charge and(More)
Ion-exchange chromatography is used in biopharmaceutical downstream processes to reduce product-related impurity levels. Because protein aggregate levels can be considered as a critical quality attribute, the removal of aggregated protein species is of primary importance. The addition of polyethylene glycol (PEG) to the mobile phase in ion-exchange(More)
The separation of proteins by internally and externally generated pH gradients in chromatofocusing on ion-exchange columns is a well-established analytical method with a large number of applications. In this work, a stoichiometric displacement model was used to describe the retention behavior of lysozyme on SP Sepharose FF and a monoclonal antibody on(More)
A large number of different stationary phases for ion-exchange chromatography from different manufacturers are available, which vary significantly in a number of chemical and physical properties. As a consequence, binding mechanisms may be different as well. In the work reported here, the retention data of model proteins (lysozyme, cytochrome c and two(More)
Dichloro[bis{1-(dicyclohexylphosphanyl)piperidine}]palladium [(P{(NC(5)H(10))(C(6)H(11))(2)})(2)PdCl(2)] (1) is a highly active and generally applicable C-C cross-coupling catalyst. Apart from its high catalytic activity in Suzuki, Heck, and Negishi reactions, compound 1 also efficiently converted various electronically activated, nonactivated, and(More)
[Pd(Cl)(2){P(NC(5)H(10))(C(6)H(11))(2)}(2)] (1) has been prepared in quantitative yield by reacting commercially available [Pd(cod)(Cl)(2)] (cod=cyclooctadiene) with readily prepared 1-(dicyclohexylphosphanyl)piperidine in toluene under N(2) within a few minutes at room temperature. Complex 1 has proved to be an excellent Negishi catalyst, capable of(More)
Humans have the highest level of adenosine-to-inosine (A-to-I) editing amongst primates, yet the reasons for this difference remain unclear. Sequence analysis of the Alu Sg elements (A-to-I RNA substrates) corresponding to the Nup50 gene in human, chimp, and rhesus reveals subtle sequence variations surrounding the edit sites. We have developed three(More)