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Spectroscopic characterization of diverse amyloid fibrils in vitro by the fluorescent dye Nile red
Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Protein Science. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
2011 (English)In: MOLECULAR BIOSYSTEMS, ISSN 1742-206X, Vol. 7, no 4, 1232-1240 p.Article in journal (Refereed) Published
Abstract [en]

The fluorescence of Nile red (9-diethylamino-5H-benzophenoxazine-5-one) is quenched in aqueous solutions but shows augmented fluorescence in hydrophobic environments. Nile red fluorescence was blue shifted and strongly augmented in the presence of various amyloid fibrils assayed under acidic as well as neutral pH conditions. Fibrils grown from lysozyme and insulin (at pH 1.6 and 65 degrees C), transthyretin (TTR) fibrils grown from the acid unfolded monomer (pH 2.0, 21 degrees C) or from the dissociated tetramer starting from native protein under less acidic conditions (pH 4.4, 37 degrees C) were detected. Nile red was also successfully employed in detecting A beta 1-42 and human prion protein (PrP90-231) amyloid fibrils grown at neutral pH. Nile red was amyloid fibril specific and did not fluoresce appreciably in the presence of the monomeric precursor proteins. Stokes shifts of the wavelength maximum of Nile red bound to various fibrils were different (ranging from 615 nm to 638 nm) indicating sensitivity to the tertiary structure in its respective binding sites of different amyloid proteins. A polarity assay using ethanol-water mixtures and pure octanol ranging from dielectric constants between 10 and 70 showed a linear correlation of Nile red Stokes shift and allowed assignment of amyloid fibril binding site polarity. Fluorescence resonance energy transfer between Thioflavin T (ThT) and Nile red was proven to be efficient and co-staining was employed to discriminate between conformational isoforms of A beta 1-42 amyloid fibrils grown under agitated and quiescent conditions. This paper demonstrates the complementary use of this fluorometric method for conformational typing of amyloid structures.

Place, publisher, year, edition, pages
Royal Society of Chemistry , 2011. Vol. 7, no 4, 1232-1240 p.
National Category
Engineering and Technology
URN: urn:nbn:se:liu:diva-67157DOI: 10.1039/c0mb00236dISI: 000288329300031OAI: diva2:407803
Available from: 2011-04-01 Created: 2011-04-01 Last updated: 2015-05-28
In thesis
1. Luminescent molecular recognition of pathognomonic and aging associated protein aggregates
Open this publication in new window or tab >>Luminescent molecular recognition of pathognomonic and aging associated protein aggregates
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Various protein inclusions have been recognized to be associated with aging and pathogenic conditions, such as in Alzheimer’s disease, Parkinson’s disease, Type 2 diabetes, and the prionoses Creutzfeldt-Jakob disease, Chronic wasting disease (CWD), and Mad cow disease. The causative transition of protein aggregation is the alteration in the conformation of the protein that renders the protein susceptible towards self-assembly. Variations in the physico-chemical ultrastructure of the protein deposit, i.e. the conformation and the chemical nature of the fibril constituent protein monomers, translate into specific structure-property phenotype, hence clinicopathology. Upon transmission and/or propagation this phenomenon gives rise to specific protein aggregate strains. Today most potential treatments of the protein conformational diseases have been a huge failure, effectively due to late diagnosis and subsequent therapeutic intervention. An imperative for efficient treatment is early detection and accurate identification for proper clinical diagnosis.

The purpose of the studies in this thesis was to develop highly sensitive methods for detection and discrimination of age- and disease associated protein deposits both for in vitro and ex vivo utilization.

Herein we have shown that, for in vitro usage, Nile red will bind to amyloid-like protein aggregates derived from a plethora of precursor proteins. It was also found that the fluorescence was insensitive to acidic assay conditions in contrast to the standard in vitro dye Thioflavin T (ThT). Further, Nile red was shown to discriminate between conformational isoforms thus enabling conformational typing of amyloid structures.

For the development of ex vivo detection methods we employed luminescent conjugated oligothiophenes (LCOs) and utilized the structure-conformation induced optical properties of this class of protein aggregate ligands. The heptameric oligothiophene h-FTAA was successfully used to detect, with high sensitivity, protein deposits from various systemic amyloidoses (ATTR, AA, AL-λ/κ, and the local amyloidosis AIAPP) derived from biopsy specimens. Also aging-associated protein deposits were detected which was found promising for early detection of potentially pathogenic protein inclusions. Further, LCO staining of tissue sections was found compatible with immunolabeling enabling subtyping of involved proteins. Early detection of amyloidosis also requires relatively non-invasive methods, why h-FTAA staining was directed towards fine-needle-aspirated (FNA) abdominal fat tissue smears. Staining of protein deposits and detection with high sensitivity was also found in the fat tissue smears.

In addition to the relatively rare prionoses it has lately been shown that Alzheimer’s, Parkinson’s diseases share similar properties as the prion pathologies. Hence the urgent need for ligands that will recognize specific disease specific strain aggregates. Using an established murine model for prion strain propagation we were able to discriminate two different prion strains, murine adapted Sheep Scrapie (mSS) and murine adapted Chronic wasting disease (mCWD) from each other by using multimodal fluorescence microscopy entailing emission/excitation spectral imaging and fluorescent lifetime imaging (FLIM).

In conclusion we have shown that the LCOs will recognize protein aggregates with high sensitivity and selectivity. In addition we have shown that the LCOs detect protein aggregates that Congo red failed to recognize thus allowing potentially early diagnosis. Last, we show that the LCOs will recognize and discriminate between different protein aggregate strains which potentially will allow disease specific therapeutic targeting.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 77 p.
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1596
National Category
Chemical Sciences Natural Sciences
urn:nbn:se:liu:diva-106878 (URN)978-91-7519-334-2 (print) (ISBN)
Public defence
2014-06-11, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 14:15 (Swedish)
Available from: 2014-05-23 Created: 2014-05-23 Last updated: 2014-05-23Bibliographically approved

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Mishra, RajeshSjölander, DanielHammarström, Per
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