Polarization parameters contain rich information on the micro- and macro-structure of scattering media. However, many of these parameters are sensitive to the spatial orientation of anisotropic media, and may not effectively reveal the microstructural information. In this paper, we take polarization images of different textile samples at different azimuth angles. The results demonstrate that the rotation insensitive polarization parameters from rotating linear polarization imaging and Mueller matrix transformation methods can be used to distinguish the characteristic features of different textile samples. Further examinations using both experiments and Monte Carlo simulations reveal that the residue rotation dependence in these polarization parameters is due to the oblique incidence illumination. This study shows that such rotation independent parameters are potentially capable of quantitatively classifying anisotropic samples, such as textiles or biological tissues.

Alzheimer’s disease (AD) is primarily caused by overproduction/deposition of β-amyloid (Aβ) in the brain. Dysregulation of iron in the brain also contributes to AD. Although iron affects β-amyloid precursor protein (APP) expression and Aβ deposition, detailed role of iron in AD requires further elucidation. Aβ is produced by sequential proteolytic cleavages of APP by β-secretase and γ-secretase. The γ-secretase complex comprises presenilins (PS1 or PS2), Nicastrin, APH-1, and PEN-2. Herein, we find that PEN-2 can interact with ferritin light chain (FTL), an important component of the iron storage protein ferritin. In addition, we show that overexpression of FTL increases the protein levels of PEN-2 and PS1 amino-terminal fragment (NTF) and promotes γ-secretase activity for more production of Aβ and Notch intracellular domain (NICD). Furthermore, iron treatments increase the levels of FTL, PEN-2 and PS1 NTF and promote γ-secretase-mediated NICD production. Moreover, downregulation of FTL decreases the levels of PEN-2 and PS1 NTF. Together, our results suggest that iron can increase γ-secretase activity through promoting the level of FTL that interacts with and stabilizes PEN-2, providing a new molecular link between iron, PEN-2/γ-secretase and Aβ generation in AD.

SUMMARYAmong the current five Variants of Concern, infections caused by the SARS-CoV-2 B.1.617.2 (Delta) variant are often associated with the greatest severity. Despite recent advances on the molecular basis of elevated pathogenicity using recombinant proteins, architecture of intact Delta virions remains veiled. Moreover, the detailed mechanism of S-mediated membrane fusion remains elusive. Here we report the molecular assembly and fusion snapshots of the authentic Delta variant. Envelope invagination and fusion events were frequently observed. Native structures of pre- and postfusion S were determined up to 4.1-Å resolution. Site-specific glycan analysis revealed increased oligomannose-type glycosylation of native Delta S over that of the Wuhan-Hu-1 S. Based on these findings, we proposed a model for S-mediated membrane fusion and a model for the invagination formation.In BriefCryo-ET of intact SARS-CoV-2 Delta variant revealed its unique architecture and captured snapshots of its membrane fusion in action.