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Updated: Aug 8, 2026
Simple Elimination of Background Fluorescence in Formalin-Fixed Human Brain Tissue for Immunofluorescence Microscopy
Published on: September 3, 2017
Biophysical and biochemical characterization of the intrinsic fluorescence from neurofibrillary tangles
Guoying Bing1, Xuan V Nguyen, Mei Liu
1Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY 40536-0098, USA. gbing@uky.edu
Insights
Researchers developed a novel intrinsic fluorescence induction method for visualizing neurofibrillary pathology. This red fluorescence method shows unique properties, potentially linked to tau hyperphosphorylation in Alzheimer's disease.
Area of Science:
- Neuroscience
- Biochemistry
- Pathology
Background:
- Neurofibrillary pathology is a hallmark of Alzheimer's disease.
- Current visualization methods often require exogenous stains.
- Intrinsic fluorescence induction offers a novel, stain-free approach.
Purpose of the Study:
- To characterize the biophysical, biochemical, and neuropathological properties of intrinsic fluorescence in neurofibrillary tangles.
- To elucidate the chemical basis and generation mechanism of this novel red fluorescence.
Main Methods:
- In vitro spectrofluorometry and in situ emission scans.
- Biochemical treatments: dephosphorylation, denaturation, and chemical modification.
- Neuropathological analysis of Alzheimer's disease brain sections.
Main Results:
- Intrinsic fluorescence of neurofibrillary tangles exhibits a red emission peak at 620 nm with a 70 nm Stoke's shift.
- Fluorescence intensity is reduced by serine modification but largely unaffected by dephosphorylation or denaturation.
- Complete fluorescence elimination observed with hydrofluoric or formic acid treatment.
Conclusions:
- The induced fluorophore possesses unique properties, suggesting a specific conformational dependence.
- Generation of this fluorescence is likely linked to the conformation of paired helical filaments.
- Tau hyperphosphorylation may play a crucial role in the formation of this intrinsic fluorophore.
Abstract:
Recently, we developed a novel fluorescent method named intrinsic fluorescence induction that allows direct visualization of neurofibrillary pathology without introducing exogenous chromogens. In the present study, we further characterized the properties of this novel red fluorescence biophysically, biochemically, and neuropathologically. In vitro spectrofluorometry and in situ emission scan show that the intrinsic fluorescence of neurofibrillary tangles has a long emission wavelength peak at 620 nm and a large Stoke's shift of 70 nm. Dephosphorylation of Alzheimer's disease brain sections with alkaline phosphatase or denaturation with guanidine only causes a subtle reduction in the induced fluorescence of neurofibrillary tangles, while hydrofluoric acid or formic acid completely eliminates the fluorescence. Chemical modification of residue serine, but not tyrosine or tryptophan, reduced the intensity of induced fluorescence significantly. The induced fluorophore, thus, has unique properties, and its generation likely depends on the particular conformation of paired helical filaments, which may in turn depend on tau hyperphosphorylation.
