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Formation of Two Different Types of Oligomers in the Early Phase of pH-Induced Aggregation of the Alzheimer A beta(12-28) Peptide
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
2012 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 41, 12389-12397 p.Article in journal (Refereed) Published
Abstract [en]

The early phase in the aggregation process of the Alzheimer's peptide A beta(12-28) with both protected and unprotected ends was studied by time-resolved infrared spectroscopy and circular dichroism spectroscopy. Aggregation in the time-resolved experiments was initiated by a rapid pH drop caused by the photolysis of 1-(2-nitrophenyl)ethyl sulfate (caged sulfate). The infrared spectra indicate two different types of aggregates from both versions of the A beta(12-28) peptide. One type has small and/or twisted beta sheets with a beta-sheet band at 1627 cm(-1), They form fast (within 60 ms), presumably from initial aggregates, and their spectral signature is consistent with a beta-barrel structure. The other type arises relatively slowly from unstructured monomers on the seconds-to-minutes time scale and forms at lower pH than the first type. These beta sheets are antiparallel, planar, and large and show an absorption band at 1622 cm(-1) that shifts to 1617 cm(-1) in 12 min with most of the shift occurring in 10 s.

Place, publisher, year, edition, pages
2012. Vol. 116, no 41, 12389-12397 p.
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-83008DOI: 10.1021/jp305015gISI: 000309902400002OAI: oai:DiVA.org:su-83008DiVA: diva2:574515
Note

AuthorCount:3;

Available from: 2012-12-05 Created: 2012-12-03 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Infrared spectroscopic studies: from small molecules to large
Open this publication in new window or tab >>Infrared spectroscopic studies: from small molecules to large
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Infrared light (IR) was first discovered by Friedrich Wilhelm Herschel in 1800. However, until 1940’s, molecular IR studies involved only water and small organic molecules, because of the long measurement times. Development Fourier transform infrared spectroscopy (FTIR) has minimized the time required to obtain data, making it possible to investigate bigger biological systems, e.g. proteins and nucleic acids.This thesis concentrates on the applications of different IR spectroscopic techniques to a variety of biological systems and development of new approaches to study complicated biological events.

The first paper in this work concerns using so-called caged compounds to study the aggregation of Alzheimer’s Aβ-peptide which is linked to the formation of neurotoxic fibrils in the brain. By adding caged-sulfate to the Aβ samples we were able to change the pH of the sample, while recording IR data and study fibril formation in a time-resolved manner. Then we used caged–ADP to study the production of ATP and creatine, mediated by creatine kinase (CK). Using CK as a helper enzyme we studied the effects of the phosphate binding on the secondary structure of SR Ca2+ATPse and determined the structural differences between two similar states Ca2E1ADP and Ca2E1ATP.

In the second part of the thesis we used ATR-FTIR spectroscopy and a specially designed dialysis setup, to develop a general method to detect ligand binding events by observing the IR absorbance changes in the water hydration shell around the molecules. The same method was used to determine the binding of DNA to the transcription factors of the E2F family. E2F proteins play main part in the gene regulatory networks that control cell development. However how they recognize their DNA-binding sites and the mechanism of binding is not well understood. By using ATR-FTIR, we observed the changes in the secondary structure of the proteins, as well as the distortions to the DNA upon E2F-DNA complex formation.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2014. 59 p.
Keyword
Infrared spectroscopy, transcription factors, DNA, creatine kinase, CaATPase, water, ligand binding
National Category
Biophysics
Research subject
Biopharmaceutics
Identifiers
urn:nbn:se:su:diva-101077 (URN)978-91-7447-876-1 (ISBN)
Public defence
2014-03-28, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Available from: 2014-03-06 Created: 2014-02-24 Last updated: 2014-02-26Bibliographically approved

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