Long-living mesoscopic clusters of a dense protein liquid are a necessary kinetic intermediate for the formation of solid aggregates of native and misfolded protein molecules; in turn, these ...aggregates underlie physiological and pathological processes and laboratory and industrial procedures. We argue that the clusters consist of a nonequilibrium mixture of single protein molecules and long-lived complexes of proteins. The puzzling mesoscopic size of the clusters is determined by the lifetime and diffusivity of these complexes. We predict and observe a crossover of cluster dynamics to critical-like density fluctuations at high protein concentrations. We predict and experimentally confirm that cluster dynamics obey a universal, diffusion-like scaling with time and wave vector, including in the critical-like regime. Nontrivial dependencies of the cluster size and volume fraction on the protein concentration are established. Possible mechanisms of complex formation include domain swapping, hydration forces, dispersive interactions, and other, system-specific, interactions. We highlight the significance of the hydration interaction and domain swapping with regard to the ubiquity of the clusters and their sensitivity to the chemical composition of the solvent. Our findings suggest novel ways to control protein aggregation.
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•Cumene hydroperoxide (CHP) is introduced to improve the property of spiro-OMeTAD.•CHP doping causes the conductivity increase and trap-state density decline of HTL.•The doped PSC ...obtains an efficiency of 20.33%, and the undoped device gets 18.00%.
Hole transport layer is one of the primary factors that improve the optical-electric properties of perovskite solar cells. Spiro-OMeTAD is frequently utilized as hole transport materials in PSCs. However, pristine or oxygen oxidized spiro-OMeTAD has low mobility and conductivity. Herein, cumene hydroperoxide is introduced to accelerate the oxidation of spiro-OMeTAD, which improves the carrier mobility, declines the trap-state density and optimizes the energy match with perovskite layer, leading to the enhancement of the performance of device. Kelvin probe force microscopy images and Atomic force microscopy images show the improvement of interface morphology. Multiple electrochemical characterizations demonstrate the acceleration of spiro-OMeTAD oxidation, the enhancement of conductivity of the doped hole transport material, and the decline of trap-state density and carrier annihilation in hole transport layer/perovskite interface after the modification. The perovskite solar cell doped with optimal concentration acquires a power conversion efficiency of 20.33%, while the undoped device gets an efficiency of 18.00%.
The interaction mechanism and digestibility of bovine skin protein (BSP)/corn starch (CS) blend complexes prepared by single screw extrusion were investigated. The effects of temperature and BSP/CS ...ratios on the physicochemical properties of BSP/CS blend complexes were analyzed. The results showed that the BSP/CS blend complexes extruded at a ratio of 3:7 had higher bulk density, texture and RVA viscosity compared with that of 7:3 and 5:5. It was mainly because the CS improved the formation of BSP/CS gel network structure through the screw extrusion. BSP and CS achieved an optimal entanglement at this ratio, potentially making pets play longer. The interaction between the –COOH of CS and the –NH
3
of BSP during the process of extrusion was detected. The micrograph of blend system at ratio of 5:5 showed looser and special mosaic structure compared with other ratios, and further led to greater digestion rate. So we can design products with digestibility or longer play time by adjusting different proportions.
Protein gelation process is of importance in food industry. The objective of this study is to investigate the influence of salt concentration variation, which induced protein conformation change, on ...protein's intermolecular interactions and its gelation process.
Paramyosin has been separated and purified from myofibrillar protein extracted from giant squid. Then Giant squid's paramyosin molecular mass and intermolecular interactions were quantified by means of light scattering techniques. Finally, the micro-rheology study via diffusing wave spectroscopy (DWS) technique revealed that this conformation change dramatically affected myofibrillar protein gelation process.
The obtained apparent molecular weight (ca 2 × 10
g/mol) suggested that protein molecules existed as dimers, while the second virial coefficient A2 significantly reduced from -3.98456 × 10
to -5.07575 × 10
ml mol/g
when KCl concentrated from 0.15 to 1 mol/L. Light scattering data also suggest that paramyosin dimers are stiff, with a persistence length of 120 nm, almost the length of a molecule and independent of salt concentration. Mean-square displacement (MSD) of tracer particles at 5 temperatures with 4 salt concentrations displayed that this conformation change had dramatic effect. Therefore, G' and G" were remarkably altered with at least one order of magnitude difference owing to this event occurrence.
Paramyosin conformation change due to KCl concentrated enhances attractive interactions with apparent molecular mass increase, which resulted in majority paramyosin molecules (> 99%) in dimeric form and promoted aggregates formation. DWS technique revealed that the conformation change dramatic affected this process characterized by the correlation functions, MSD, and G' and G". This study brings forward data on understanding the effect of a major salt supplement, KCl, on the chemical physics of a major muscle protein.
Protein crystal nucleation processes are drawing increasing interests in both academic and industrial communities. Electric field is a promising means, due to its versatility and easy application, ...among various external fields that may lead to controllable desired protein crystal nucleation. Different from literature reported experimental and theoretical studies that examined the effects of high frequency electric fields; this work was focused on the low frequency range. For this purpose, Hen-White Lysozyme crystal nucleation from its aqueous solution was used as the model system. We found by experiments that the nucleation rate is non-monotonously dependent on electric field frequency less than 1kHz, which may be ascribed to the mutual orientation modification between neighbor protein molecules induced by the external low frequency, and is different from the case of high frequencies that influence the intermolecular interactions.
•The dependency of lysozyme crystal nucleation rate on frequency of external electric field cannot be explained by the available theories.•This nucleation rate dependency may be ascribed to the influence of electric field frequency on the protein molecule orientation distribution inside of double layer along the electrodes.•Our result indicates that the protein crystal nucleation rate should be strongly affected by the patch distribution along the protein molecule surface.
Sickle cell anemia is a debilitating genetic disease that affects hundreds of thousands of babies born each year worldwide. Its primary pathogenic event is the polymerization of a mutant, sickle ...cell, hemoglobin (HbS); and this is one of a line of diseases (Alzheimer's, Huntington's, prion, etc.) in which nucleation initiates pathophysiology. We show that the homogeneous nucleation of HbS polymers follows a two-step mechanism with metastable dense liquid clusters serving as precursor to the ordered nuclei of the HbS polymer. The evidence comes from data on the rates of fiber nucleation and growth and nucleation delay times, the interaction of fibers with polarized light, and mesoscopic metastable HbS clusters in solution. The presence of a precursor in the HbS nucleation mechanism potentially allows low-concentration solution components to strongly affect the nucleation kinetics. The variations of these concentrations in patients might account for the high variability of the disease in genetically identical patients. In addition, these components can potentially be utilized for control of HbS polymerization and treatment of the disease.
In search of novel control parameters for the polymerization of sickle cell hemoglobin (HbS), the primary pathogenic event of sickle cell anemia, we explore the role of free heme, which may be ...excessively released in sickle erythrocytes. We show that the concentration of free heme in HbS solutions typically used in the laboratory is 0.02–0.04 mole heme/mole HbS. We show that dialysis of small molecules out of HbS solutions arrests HbS polymerization. The addition of 100–260 μM of free heme to dialyzed HbS solutions leads to rates of nucleation and polymer fiber growth faster by two orders of magnitude than before dialysis. Toward an understanding of the mechanism of nucleation enhancement by heme, we show that free heme at a concentration of 66 μM increases by two orders of magnitude the volume of the metastable clusters of dense HbS liquid, the locations where HbS polymer nuclei form. These results suggest that spikes of the free heme concentration in the erythrocytes of sickle cell anemia patients may be a significant factor in the complexity of the clinical manifestations of sickle cell anemia. The prevention of free heme accumulation in the erythrocyte cytosol may be a novel avenue to sickle cell therapy.
Dense liquid phases, metastable with respect to a solid phase, form in solutions of proteins and small-molecule materials. They have been shown to serve as a prerequisite for the nucleation of ...crystals and other ordered solid phases. Here, using crystals of the protein lumazine synthase from Bacillus subtilis, which grow by the generation and spreading of layers, we demonstrate that within a range of supersaturations the only mechanism of generation of growth layers involves the association of submicrometer-size droplets of the dense liquid to the crystal surface. The dense liquid is metastable not only with respect to the crystals, but also with respect to the low-concentration solution: dynamic light scattering reveals that the droplets' lifetime is limited to several seconds, after which they decay into the low-concentration solution. The short lifetime does not allow growth to detectable dimensions so that liquid−liquid phase separation is not observed within a range of conditions broader than the one used for crystallization. If during their lifetime the droplets encounter a crystal surface, they lower their free energy not by decay, but by transformation into crystalline matter, ensuring perfect registry with the substrate. These observations illustrate two novel features of phase transformations in solutions: the existence of doubly metastable, short-lifetime dense phases and their crucial role for the growth of an ordered solid phase.
Nucleation of ordered solid phases of proteins triggers numerous phenomena in laboratory, industry, and in healthy and sick organisms. Recent simulations and experiments with protein crystals suggest ...that the formation of an ordered crystalline nucleus is preceded by a disordered high-density cluster, akin to a droplet of high-density liquid that has been observed with some proteins; this mechanism allowed a qualitative explanation of recorded complex nucleation kinetics curves. Here, we present a simple phenomenological theory that takes into account intermediate high-density metastable states in the nucleation process. Nucleation rate data at varying temperature and protein concentration are reproduced with high fidelity using literature values of the thermodynamic and kinetic parameters of the system. Our calculations show that the growth rate of the near-critical and supercritical ordered clusters within the dense intermediate is a major factor for the overall nucleation rate. This highlights the role of viscosity within the dense intermediate for the formation of the ordered nucleus. The model provides an understanding of the action of additives that delay or accelerate nucleation and presents a framework within which the nucleation of other ordered protein solid phases, e.g., the sickle cell hemoglobin polymers, can be analyzed.
Hematin crystallization is an essential element of heme detoxification of malaria parasites and its inhibition by antimalarial drugs is a common treatment avenue. We demonstrate at biomimetic ...conditions in vitro irreversible inhibition of hematin crystal growth due to distinct cooperative mechanisms that activate at high crystallization driving forces. The evolution of crystal shape after limited-time exposure to both artemisinin metabolites and quinoline-class antimalarials indicates that crystal growth remains suppressed after the artemisinin metabolites and the drugs are purged from the solution. Treating malaria parasites with the same agents reveals that three- and six-hour inhibitor pulses inhibit parasite growth with efficacy comparable to that of inhibitor exposure during the entire parasite lifetime. Time-resolved in situ atomic force microscopy (AFM), complemented by light scattering, reveals two molecular-level mechanisms of inhibitor action that prevent β-hematin growth recovery. Hematin adducts of artemisinins incite copious nucleation of nonextendable nanocrystals, which incorporate into larger growing crystals, whereas pyronaridine, a quinoline-class drug, promotes step bunches, which evolve to engender abundant dislocations. Both incorporated crystals and dislocations are known to induce lattice strain, which persists and permanently impedes crystal growth. Nucleation, step bunching, and other cooperative behaviors can be amplified or curtailed as means to control crystal sizes, size distributions, aspect ratios, and other properties essential for numerous fields that rely on crystalline materials.
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