Multiplexing multiple orbital angular momentum (OAM) channels enables high-capacity optical communication. However, optical scattering from ambient microparticles in the atmosphere or mode coupling in optical fibers significantly decreases the orthogonality between OAM channels for demultiplexing and eventually increases crosstalk in communication. Here, we propose a novel scattering-matrix-assisted retrieval technique (SMART) to demultiplex OAM channels from highly scattered optical fields and achieve an experimental crosstalk of –13.8 dB in the parallel sorting of 24 OAM channels after passing through a scattering medium. The SMART is implemented in a self-built data transmission system that employs a digital micromirror device to encode OAM channels and realize reference-free calibration simultaneously, thereby enabling a high tolerance to misalignment. We successfully demonstrate high-fidelity transmission of both gray and color images under scattering conditions at an error rate of <0.08%. This technique might open the door to high-performance optical communication in turbulent environments.

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Unfolding and aggregation are basic problems in protein science with serious biotechnological and medical implications. Probing the sequential events occurring during the unfolding and aggregation process and the relationship between unfolding and aggregation is of particular interest. In this study, two-dimensional infrared (2D IR) correlation spectroscopy was used to study the sequential events and starting temperature dependence of Myoglobin (Mb) thermal transitions. Though a two-state model could be obtained from traditional 1D IR spectra, subtle noncooperative conformational changes were observed at low temperatures. Formation of aggregation was observed at a temperature (50-58 degrees C) that protein was dominated by native structures and accompanied with unfolding of native helical structures when a traditional thermal denaturation condition was used. The time course NMR study of Mb incubated at 55 degrees C for 45 h confirmed that an irreversible aggregation process existed. Aggregation was also observed before fully unfolding of the Mb native structure when a relative high starting temperature was used. These findings demonstrated that 2D IR correlation spectroscopy is a powerful tool to study protein aggregation and the protein aggregation process observed depends on the different environmental conditions used.

Cells mitigate ER stress through the unfolded protein response (UPR). Here, we report formation of ER whorls as an effector mechanism of the ER stress response. We found that strong ER stress induces formation of ER whorls, which contain ER-resident proteins such as the Sec61 complex and PKR-like ER kinase (PERK). ER whorl formation is dependent on PERK kinase activity and is mediated by COPII machinery, which facilitates ER membrane budding to form tubular-vesicular ER whorl precursors. ER whorl precursors then go through Sec22b-mediated fusion to form ER whorls. We further show that ER whorls contribute to ER stress-induced translational inhibition by possibly modulating PERK activity and by sequestering translocons in a ribosome-free environment. We propose that formation of ER whorls reflects a new type of ER stress response that controls inhibition of protein translation.