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Huddinge, Sweden

Gustafsson S.S.,Uppsala University | Vrang L.,Medivir | Terelius Y.,Medivir | Danielson U.H.,Uppsala University
Analytical Biochemistry | Year: 2011

To develop efficient and reliable methods for prediction of serum protein binding of drug leads, the kinetic characteristics for the interactions between selected compounds and human serum albumin and α 1-acid glycoprotein have been explored using a surface plasmon resonance biosensor. Conventional methods for quantification of interactions (i.e., using rate constants or affinities determined on the basis of a reasonable mechanistic model) were applicable for only a few of the compounds. The affinity of a primary interaction and the contribution of lower affinity secondary interactions could be estimated for some compounds, but the affinity of many compounds could not be quantified by either of these methods. To have a quantification method that could be used for all compounds, independent of affinity and complexity of interaction mechanisms, the concept of "binding efficiency," analogous to "catalytic efficiency" used for enzymes, was developed. It allowed the quantification of the binding of compounds interacting with weak affinity and for which saturation is not reached within a concentration range where the compound is soluble or when the influence of interactions with secondary sites makes interpretations difficult. In addition, compounds with large fractional binding can be identified by this strategy and simply quantified relative to reference compounds. This approach will enable ranking and identification of structure-activity relationships of compounds with respect to their serum protein binding profile. © 2010 Elsevier Inc. All rights reserved.

Christopeit T.,Uppsala University | Stenberg G.,Uppsala University | Gossas T.,Uppsala University | Nystrom S.,Medivir | And 3 more authors.
Analytical Biochemistry | Year: 2011

A surface plasmon resonance (SPR) biosensor-based assay for membrane-embedded full-length BACE1 (β-site amyloid precursor protein cleaving enzyme 1), a drug target for Alzheimer's disease, has been developed. It allows the analysis of interactions with the protein in its natural lipid membrane environment. The enzyme was captured via an antibody recognizing a C-terminal His6 tag, after which a lipid membrane was reconstituted on the chip using a brain lipid extract. The interaction between the enzyme and several inhibitors confirmed that the surface was functional. It had slightly different interaction characteristics as compared with a reference surface with immobilized ectodomain BACE1 but had the same inhibitor characteristic pH effect. The possibility of studying interactions with BACE1 under more physiological conditions than assays using truncated enzyme or conditions dictated by high enzyme activity is expected to increase our understanding of the role of BACE1 in Alzheimer's disease and contribute to the discovery of clinically efficient BACE1 inhibitors. The strategy exploited in the current study can be adapted to other membrane-bound drug targets by selecting suitable capture antibodies and lipid mixtures for membrane reconstitution. © 2011 Elsevier Inc. All rights reserved.

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