ABSTRACT
The aggregation promoter heparin is commonly used to study the aggregation kinetics and biophysical properties of protein amyloids. However, the underlying mechanism for amyloid promotion by heparin remains poorly understood. In the case of the neuropeptide ß-endorphin that can reversibly adopt a functional amyloid form in nature, aggregation in the presence of heparin leads to a loss of function. Applying correlative optical super-resolution microscopy methods, we show that heparin incorporates into emerging ß-endorphin fibrils forming an integral component and is essential for amyloid templating. This will have direct implications on ß-endorphin's normal physiological function and raises concerns on the biological relevance of heparin-promoted amyloid models.
Subject(s)
Amyloid beta-Peptides/chemistry , Amyloid/chemistry , Heparin/chemistry , Protein Aggregates , Protein Aggregation, Pathological , beta-Endorphin/chemistry , MicroscopyABSTRACT
We study both experimentally and theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in standard birefringent optical fibers. The ability to produce a range of two-photon spectral states, from highly correlated (entangled) to completely factorable, by means of cross-polarized birefringent phase matching, is explored. A simple model is developed to predict the spectral state of the photon pair which shows how this can be adjusted by choosing the appropriate pump bandwidth, fiber length and birefringence. Spontaneous Raman scattering is modeled to determine the tradeoff between SFWM and background Raman noise, and the predicted results are shown to agree with experimental data.
