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Various biophysical techniques have been extensively employed to study protein aggregation due to its significance. Traditionally, these methods detect aggregation at micrometer length scales and micromolar concentrations. However, unlike in vitro, protein aggregation typically occurs at nanomolar concentrations in vivo. Here, using fluorescence correlation spectroscopy (FCS), we captured bromelain aggregation at concentrations as low as ~20 nM, surpassing the detection limit of traditional methods like thioflavin T fluorescence, scattering, and fluorescence microscopy by more than one order of magnitude. Moreover, using thioflavin T fluorescence‐based FCS, we have detected larger aggregates at higher bromelain concentrations, which is undetectable in FCS otherwise. Importantly, our study reveals inherent heterogeneity in bromelain aggregation, inaccessible to ensemble‐averaged techniques. The presented report may provide a platform for the characterization of premature aggregates at very low protein concentrations, which are thought to be functionally significant species in protein aggregation‐induced diseases. [ABSTRACT FROM AUTHOR]

UV light-induced photodegradation of the organic–inorganic hybrid (OIH) Ruddlesden–Popper (RP) perovskite nanoplates (NPls) is a crucial bottleneck for optoelectronic application in the future. Continuous UV exposure triggers the deprotonation of the spacer as well as the A-site cation (CH3NH3+), ultimately leading to lattice collapse. To combat this photoinstability, we introduce a surface modification of colloidal OIH RP NPls, (OAm)2(CH3NH3PbI3)2PbI4 (n = 3) (OAm stands for oleylammonium cation) by 4-fluorobenzylammonium iodide (4FBAI). In ambient conditions, conventional NPls deteriorate within 80 min of UV exposure, whereas the 4FBAI-modified NPls exhibit remarkable endurance, maintaining structural integrity for 12 h with only a 11% reduction in the initial photoluminescence (PL). Interestingly, benzylammonium iodide (BAI) and 4-methoxybenzylammonium iodide (4OBAI)-treated NPl fail to provide similar photostability, thus signifying the importance of the fluorine atom. The fluorine atom enhances the positive charge density of the ammonium ion and facilitates faster deprotonation compared to parental ammonium ions (here, OAm+ and CH3NH3+) under UV exposure. This ensures the survival of the parent nanoplate structure. Along with the photostability enhancement, the PL quantum yield of the treated NPl also increases to 50 ± 2 from 35 ± 2%. This research not only addresses the pressing photostability issue of RP NPl stability but also illuminates the pivotal role of specific chemical modifications, such as fluorine atom incorporation, for the fabrication of UV-stable perovskite devices in the future. [ABSTRACT FROM AUTHOR]

The mechanism of protein stabilization by osmolytes remains one of the most important and long-standing puzzles. The traditional explanation of osmolyte-induced stability through the preferential exclusion of osmolytes from the protein surface has been seriously challenged by the observations like the concentration-dependent reversal of osmolyte-induced stabilization/destabilization. The more modern explanation of protein stabilization/destabilization by osmolytes considers an indirect effect due to osmolyte-induced distortion of the water structure. It provides a general mechanism, but there are numerous examples of protein-specific effects, i.e., a particular osmolyte might stabilize one protein, but destabilize the other, that could not be rationalized through such an explanation. Herein, we hypothesized that osmolyte-induced modulation of associated water might be a critical factor in controlling protein stability in such a medium. Taking different osmolytes and papain as a protein, we proved that our proposal could explain protein stability in osmolyte media. Stabilizing osmolytes rigidify associated water structures around the protein, whereas destabilizing osmolytes make them flexible. The strong correlation between the stability and the associated water dynamics, and the fact that such dynamics are very much protein specific, established the importance of considering the modulation of associated water structures in explaining the osmolyte-induced stabilization/destabilization of proteins. More interestingly, we took another protein, bromelain, for which a traditionally stabilizing osmolyte, sucrose, acts as a stabilizer at higher concentrations but as a destabilizer at lower concentrations. Our proposal successfully explains such observations, which is probably impossible by any known mechanisms. We believe this report will trigger much research in this area. [ABSTRACT FROM AUTHOR]