Alzheimer beta-amyloid peptide 25-35 : electrostatic interactions with phospholipid membranes

Terzi, E. and Holzemann, G. and Seelig, J.. (1994) Alzheimer beta-amyloid peptide 25-35 : electrostatic interactions with phospholipid membranes. Biochemistry, Vol. 33, H. 23. pp. 7434-7441.

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Official URL: http://edoc.unibas.ch/dok/A5257451

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The role of lipids in the aggregation of three Alzheimer model peptides was investigated with circular dichroism spectroscopy and high-sensitivity titration calorimetry under conditions of low ionic strength. In solution, the peptides beta AP(25-35)OH and beta AP(25-35Nle)NH2 exhibit a reversible random-coilbeta-sheet (or beta-structured aggregate) transition. Addition of lipid vesicles containing negatively charged lipids shifts the random-coilbeta-sheet equilibrium almost completely toward beta-sheet structure, which can be explained by the specific conditions created at the membrane surface: the cationic peptides are attracted to the negatively charged membrane, and the increase in peptide concentration together with the partial alignment of the peptide molecules then facilitates beta-sheet formation. The third peptide, beta AP-(25-35)NH2, also binds to the lipid membrane but was found to adopt an essentially random-coil structure, both with and without lipids. A quantitative characterization of the binding equilibrium was possible with high-sensitivity titration calorimetry. All three peptides exhibited exothermic binding enthalpies which varied between delta H approximately -2 kcal/mol for beta AP(25-35)OH and -8 kcal/mol for beta AP(25-35)NH2. The apparent binding constants, calculated with bulk concentrations, were large and varied between 500 and 5 x 10(4) M-1, depending on the experimental conditions. However, after correction for electrostatic charge effects using the Gouy-Chapman theory, the intrinsic binding constants were found to be constant and much smaller with K approximately 2-10 M-1.(ABSTRACT TRUNCATED AT 250 WORDS)
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Biophysical Chemistry (Seelig J)
UniBasel Contributors:Seelig, Joachim
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:19
Deposited On:22 Mar 2012 13:18

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