Search for: All records

Abstract Amyloid‐beta (Aβ) peptides, primarily Aβ40 and Aβ42, are central to the formation of amyloid plaques, a pathological hallmark of Alzheimer's disease (AD). These peptides, derived from the amyloid precursor protein (APP), are aggregation prone and neurotoxic. Experimental studies aimed at understanding Aβ aggregation and interaction require pure, monomeric peptides with the native sequences, including the absence of an N‐terminal methionine. We present an optimized protocol for producing recombinant human Aβ40 and Aβ42 using a SUMO fusion system inEscherichia coli. Cleavage of the SUMO tag enables recovery of native‐sequence peptides, producing physiologically relevant monomers with high yield and purity. This method eliminates the need for chemical synthesis and offers a reliable and cost‐effective approach to producing recombinant Aβ suitable for aggregation studies, structural analyses, and interaction assays. The resulting peptides closely mimic endogenous Aβ, facilitating accurate models of Alzheimer's disease pathogenesis and supporting future therapeutics development. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Expression and purification of Aβ40 and Aβ42 fromEscherichia coli 

Abstract Chaidez and Edtmair have recently found the first examples of dynamically convex domains in $$\mathbb{R}^{4}$$ that are not symplectomorphic to convex domains, answering a long-standing open question. In this paper, we discover new examples of such domains without referring to Chaidez–Edtmair’s methods. We show a stronger result: that these domains are arbitrarily far from the set of convex domains in $$\mathbb{R}^{4}$$ with respect to the coarse symplectic Banach–Mazur distance. 

Abstract Cyclostrophic rotation in the core region of tropical cyclones (TCs) imprints a distinct signature upon their turbulence structure. Its intensity is characterized by the radius of maximum wind, , and the azimuthal wind velocity at that radius, . The corresponding cyclostrophic Coriolis parameter, /, far exceeds its planetary counterpart, , for all storms; its impact increases with storm intensity. The vortex can be thought of as a system undergoing a superposition of planetary and cyclostrophic rotations represented by the effective Coriolis parameter, . On the vortex periphery, merges with . In the classical Rankine vortex model, the inner region undergoes solid‐body rotation rendering constant. In a more realistic representation, is not constant, and the ensuing cyclostrophic ‐effect sustains vortex Rossby waves. Horizontal turbulence in such a system can be quantified by a two‐dimensional anisotropic spectrum. An alternative description is provided by one‐dimensional, longitudinal, and transverse spectra computed along the radial direction. For rotating turbulence with vortex Rossby waves, the spectra divulge a coexistence of three ranges: Kolmogorov, peristrophic (spectral amplitudes are proportional to ), and zonostrophic (transverse spectrum amplitude is proportional to ). A comprehensive database of TC winds collected by reconnaissance airplanes reveals that with increasing storm intensity, their cyclostrophic turbulence evolves from purely peristrophic to mixed peristrophic‐zonostrophic to predominantly zonostrophic. The latter is akin to the flow regime harboring zonal jets on fast rotating giant planets. The eyewall of TCs is an equivalent of an eastward zonal jet. 

Abstract Initially a Category 3 storm, Hurricane Ian (2022) rapidly intensified on the West Florida Shelf reaching Category 5 over the course of about 12 hr. Intensification occurred despite inhibiting factors such as high axial tilt, high vertical wind shear, low atmospheric moisture, and transit over a relatively shallow continental shelf. Using a high‐resolution simulation of Hurricane Ian from the Hurricane Weather Research Forecasting (HWRF) model, we examine the factors that both hindered and supported rapid intensification (RI) by blending various methods. We show that an increase in diabatic heating in the eyewall led to an inward radial advection of momentum, seen in both the absolute angular momentum budget and in the azimuthal wind budget. Analysis of the moist static energy budget indicates that the substantial latent heat flux from the surface was enough to balance heat losses through storm outflow. For instance, surface latent heat fluxes exceeded 1,500 W m⁻²on the West Florida Continental Shelf. As suggested by actual ocean temperature observations that substantially exceeded those in the HWRF simulation, the latent heating may have even been larger. Physical explanations for discrepancies between the simulated Hurricane Ian and observations are provided, particularly those pertaining to the coastal ocean at the time of Ian's passage. This research provides a comprehensive explanation of the RI of a hurricane using momentum budget analyses as part of a coupled air‐sea analysis. Our findings demonstrate the importance of in situ oceanic air‐sea measurements in evaluating the performance of coupled models, especially for hurricanes.