Abstract The wide application of protein fibrils as functional materials has been restricted by the limited scalability of fibrillation methods, slow kinetics, and use of expensive purified proteins. Herein, inspired by the biological cooperativity of proteins in macro-molecularly crowded environments, these restrictions have been overcome. Using ionic liquid cholinium tosylate that acts as a fibrillation agent, instantaneous production of protein fibrils is shown directly from a real and low-cost matrix, i.e. egg white. The fibrillation of egg white proteome is confirmed by microscopy, whereas the fibrillation kinetics is monitored by fluorescence changes of the thioflavin T dye and secondary structural transitions. Spectroscopic and molecular docking studies are used to identify the proteins involved and to appraise the molecular-level mechanisms ruling the proteins structural changes upon fibrillation. The obtained fibrils have enhanced mechanical stiffness and cytocompatibility, demonstrating their potential to act as improved enzyme supports.
Ionic liquid (IL) surfactant choline dioctylsulfosuccinate, [Cho][AOT], formed polydispersed vesicular structures in the IL, ethylmethylimidazolium ethylsulfate, [C2mim][C2OSO3]. Cytochrome c dissolved in such a colloidal medium has shown very high peroxidase activity (∼2 times to that in neat IL and ∼4 times to that in an aqueous buffer). Significantly, the enzyme retained both structural stability and functional activity in IL colloidal solutions up to 180 °C, demonstrating the suitability of the system as a high temperature bio-catalytic reactor.
Amyloid-like fibrils are garnering keen interest in biotechnology as supramolecular nanofunctional units to be used as biomimetic platforms to control cell behavior. Recent insights into fibril functionality have highlighted their importance in tissue structure, mechanical properties, and improved cell adhesion, emphasizing the need for scalable and high-kinetics fibril synthesis. In this study, we present the instantaneous and bulk formation of amyloid-like nanofibrils from human platelet lysate (PL) using the ionic liquid cholinium tosylate as a fibrillating agent. The instant fibrillation of PL proteins upon supramolecular protein–ionic liquid interactions was confirmed from the protein conformational transition toward cross-β-sheet-rich structures. These nanofibrils were utilized as building blocks for the formation of thin and flexible free-standing membranes via solvent casting to support cell self-aggregation. These PL-derived fibril membranes reveal a nanotopographically rough surface and high stability over 14 days under cell culture conditions. The culture of mesenchymal stem cells or tumor cells on the top of the membrane demonstrated that cells are able to adhere and self-organize in a three-dimensional (3D) spheroid-like microtissue while tightly folding the fibril membrane. Results suggest that nanofibril membrane incorporation in cell aggregates can improve cell viability and metabolic activity, recreating native tissues' organization. Altogether, these PL-derived nanofibril membranes are suitable bioactive platforms to generate 3D cell-guided microtissues, which can be explored as bottom-up strategies to faithfully emulate native tissues in a fully human microenvironment.
The conventional sodium dodecylbenzenesulfonate (NaDBS) has been converted into an efficient and nontoxic anionic surface-active ionic liquid, cholinium dodecylbenzenesulfonate (Cho[DBS]). We have investigated its self-assembling behavior, interaction with the enzyme cellulase, and ecotoxicity. The surface-active properties at the air-liquid interface and the aggregation behavior of Cho[DBS] in water have been determined using tensiometry, isothermal titration calorimetry (ITC), conductometry, and dynamic light scattering (DLS). The enzyme activity was observed using dinitro salicylic acid analysis. The enhanced enzyme activity was explained through active-site exfoliation and structural constancy of cellulase in the micellar medium using the results from fluorescence, circular dichroism, DLS, and ITC. The nontoxic nature was confirmed by toxicity analysis on the freshwater microalgae Scenedesmus sp.
The growth and stability of salt–water clusters have been experimentally studied in aqueous solutions of NaCl, KCl, and NH₄Cl from dilute to near-saturation conditions employing dynamic light scattering and zeta potential measurements. In order to examine cluster stability, the changes in the cluster sizes were monitored as a function of temperature. Compared to the other cases, the average size of NaCl–water clusters remained almost constant over the studied temperature range of 20–70 °C. Information obtained from the temperature-dependent solution compressibility (determined from speed of sound and density measurements), multinuclear NMR (¹H, ¹⁷O, ³⁵Cl NMR), and FTIR were utilized to explain the cluster behavior. Comparison of NMR chemical shifts of saturated salt solutions with solid-state NMR data of pure salts, and evaluation of spectral modifications in the OH stretch region of saturated salt solutions as compared to that of pure water, provided important clues on ion pair–water interactions and water structure in the clusters. The high stability and temperature independence of the cluster sizes in aqueous NaCl shed light on the temperature invariance of its solubility.
Dual, aqueous solubility behavior of Na₂SO₄ as a function of temperatures is still a natural enigma lying unresolved in the literature. The solubility of Na₂SO₄ increases up to 32.38 °C and decreases slightly thereafter at higher temperatures. We have thrown light on this phenomenon by analyzing the Na₂SO₄–water clusters (growth and stability) detected from temperature-dependent dynamic light scattering experiments, solution compressibility changes derived from the density and speed of sound measurements, and water structural changes/Na₂SO₄ (ion pair)–water interactions observed from the FT-IR and 2D DOSY ¹H NMR spectroscopic investigations. It has been observed that Na₂SO₄–water clusters grow with an increase in Na₂SO₄ concentration (until the solubility transition temperature) and then start decreasing afterward. An unusual decrease in cluster size and solution compressibility has been observed with the rise in temperature for the Na₂SO₄ saturated solutions below the solubility transition temperature, whereas an inverse pattern is followed thereafter. DOSY experiments have indicated different types of water cluster species in saturated solutions at different temperatures with varying self-diffusion coefficients. The effect of NaCl (5–15 wt %) on the solubility behavior of Na₂SO₄ at different temperatures has also been examined. The studies are important from both fundamental and industrial application points of view, for example, toward the clean separation of NaCl and Na₂SO₄ from the effluent streams of textile and tannery industries.
Triplet-triplet annihilation photon upconversion (TTA-UC) is a process where two low-energy photons are converted into one higher-energy photon. A crucial component for an efficient upconversion process is the statistical probability factor (f), defined as the probability of the formation of a high-energy singlet state upon coupling of two low-energy triplet states. Theoretically, f depends on the energy level distribution, molecular orientation, inter-triplet exchange coupling of triplet dyads, and spin-mixing of resulting spin states (singlet, triplet, and quintet). However, experimental values of f for acene-based annihilators have been subject to large variations due to many factors that have resulted in the reporting of different f values for the same molecule. In this work, we discuss these factors by studying perylene as a case study annihilator, for which by far the largest variation in f = 16 to 100% has been reported. We systematically investigated the TTA-UC of PdTPBP:perylene, as a sensitizer-annihilator pair and obtained the experimental f = 17.9 ± 2.1% for perylene in THF solution. This limits the maximum TTA-UC quantum yield to 9.0% (out of 50%) for this annihilator. We found that such a low f value for perylene is largely governed by the energy-gap law where higher non-radiative losses due to the small energy gap between 2 × T1 and T2 affect the probability of singlet formation. Interestingly, we found this observation true for other acene-based annihilators whose emission ranges from the UV to the yellow region, thus providing a blueprint for future design of efficient TTA-UC systems.
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