Biophysical and biochemical characterization of the intrinsic fluorescence from neurofibrillary tangles.
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.
Bing
Guoying
G
Department of Anatomy and Neurobiology, University of Kentucky, Lexington, KY 40536-0098, USA. gbing@uky.edu
Nguyen
Xuan V
XV
Liu
Mei
M
Markesbery
William R
WR
Sun
Anyang
A
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000473:pathology*; D005453:Fluorescence; D019791:Guanidine / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence / Q000379:methods; D009419:Nerve Tissue Proteins / Q000172:deficiency; D016874:Neurofibrillary Tangles / Q000187:drug effects / Q000473:pathology*; D015513:Oncogene Proteins / Q000172:deficiency; D010766:Phosphorylation; D010777:Photochemistry; D011180:Postmortem Changes; D013050:Spectrometry, Fluorescence / Q000379:methods; D013997:Time Factors; D014357:Trypsin / Q000494:pharmacology
C428027:NREP protein, human; D009419:Nerve Tissue Proteins; D015513:Oncogene Proteins; D014357:Trypsin; D019791:Guanidine