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The aggregation of variably charged nanoparticles is usually induced by the changes in internal and external conditions, such as solution temperature, pH, particle size, van der Waals force, and electrostatic repulsion among particles. In order to explore the effect of pH on the aggregation of variable charge nanoparticles, this paper proposed an extended model based on the 3D on-lattice Cluster–Cluster Aggregation (CCA) model. The extended model successfully established the relationship between pH and sticking probability, and used Smoluchowski theory to calculate the aggregation rate of nanoparticles. The simulation results showed that: (1) the change of the aggregation rate of the variable charge nanoparticles with pH conforms to the Gaussian distribution, (2) the initial particle concentration has a significant effect on the aggregation rate of the nanoparticles, and (3) pH can affect the competition between van der Waals force and electrostatic repulsion between particles, thereby affecting the degree of openness of clusters. The research demonstrated the extended CCA model is valuable in studying the aggregation of the variably charged nanoparticles via transforming the corresponding influence factors into the influence on the sticking probability.

Al2O3 particles with different sizes were dispersed into an epoxy precursor to improve the thermal conductivity (TC) of the epoxy coating. Al2O3 particles tend to aggregate in epoxy, and the aggregation becomes more apparent (formation of micropapillae when the particle size is larger than 1 μm) with the increase of particle size. The calculated fast aggregation rates of various-size Al2O3 particles in epoxy showed that the fast aggregation rate increased to a maximum rate of 6.37 × 10–20 m3·s–1 at a particle size of 200 nm and then decreased to a plateau value with the increase of particle size. The high fast aggregation rate caused the aggregation and the formation of nano- and micropapillae, causing the heterogeneous distribution of Al2O3 particles. These micropapillae were separated by epoxy, which made formation of continuous pathways fail, causing the reduction of TC and heterogeneous heat distribution. The highest thermal conductivity of 2.52 W/m·K and uniform heat distribution were observed at the optimum filler size of 30 nm. The research findings provide the knowledge of optimizing particle size on constructing a thermally conductive polymer composite.

Alzheimer's disease is a progressive fatal neurodegenerative disease with no cure or effective treatments. The hallmarks of disease include extracellular plaques and intracellular tangles of aggregated protein. The intracellular tangles consist of the microtubule associated protein tau. Preventing the pathological aggregation of tau may be an important therapeutic approach to treat disease. In this study we show that small heat shock protein 22 kDa (Hsp22) can prevent the aggregation of tau in vitro. Additionally, tau can undergo liquid–liquid phase separation (LLPS) in the presence of crowding reagents which causes it to have an increased aggregation rate. We show that Hsp22 can modulate both the aggregation and LLPS behavior of tau in vitro.

There is a great demand for numerically simulating the layering granulation of iron ore, in which multiple fine ore particles adhere simultaneously to the surface of a single coarse ore particle. This paper presents such a simulation method by coupling a discrete element method (DEM) and a population balance model (PBM). To calculate the high aggregation rate between coarse and fine particles in the layering granulation process, we here developed a hybrid aggregation model combining the one-to-one and one-to-multiple particle aggregations. A two-way DEM–PBM coupling simulation with the hybrid aggregation model was then performed. The calculation results were in good agreement with the results of an experiment conducted on iron ore granulation in a rotating drum in terms of the granular flow and particle growth rate. Thus, we demonstrated that the proposed simulation method can be effective for simulating the layering granulation process.

Apigenin is a type of flavonols that exhibits anti-caries properties. Bacterial adherence is the initial step in the forming of a stable biofilm that leads to caries. Bacterial adherence is affected by surface characteristics, including hydrophobicity and bacterial aggregation. However, the effect of apigenin on surface characteristics of cariogenic bacteria has not been reported. We aimed to examine the effects of apigenin on adherence and biofilm formation of Streptococcus mutans UA159. Hydrophobicity and bacterial aggregation, pac and gbpC gene expressions, and cytotoxicity on human dental pulp cells were also determined. Apigenin significantly inhibited the adherence and biofilm formation of S. mutans. Hydrophobicity decreased, whereas the aggregation rate was significantly increased compared with the control. Apigenin significantly suppressed pac and gbpC gene expressions. Apigenin exhibited acceptable biocompatibility on hDPCs. Thus, apigeinin may affect adherence and biofilm formation by altering the surface properties of S. mutans without obvious adverse effect on hDPCs.

Intraneuronal aggregation of the intrinsically disordered protein α-synuclein is at the core of Parkinson's disease and related neurodegenerative disorders. Several reports show that the concentration of salts in the medium heavily affects its aggregation rate and fibril morphology, but a characterization of the individual monomeric conformations underlying these effects is still lacking. In this work, we have applied our α-synuclein-optimized coarse-grained molecular dynamics approach to decipher the structural features of the protein monomer under a range of NaCl concentrations (0.0-1.0 M). The results show that key intramolecular contacts between the terminal domains are lost at intermediate concentrations (leading to extended conformations likely to fibrillate), but recovered at high concentrations (leading to compact conformations likely to evolve toward amorphous aggregates). The pattern of direct interactions of the terminal α-synuclein domains with Na+ and Cl- ions plays a key role in explaining this effect. Our results are consistent with a recent study reporting a fibrillation enhancement at moderate NaCl concentrations but an inhibition at higher concentrations. The present work will contribute to improving our understanding of the structural features of monomeric α-synuclein, determining its NaCl-induced fibrillation propensity and the molecular basis of synucleinopathies, necessary for the future development of disease-halting therapies.

Neptunea cumingii is an important nutrition-rich economic species in China. Juveniles of N. cumingii suffer from high mortality at low temperatures, which has proved a limiting factor in raising seedlings in artificial habitats. Previous research has shown that N. cumingii displays aggregation behavior in response to adverse environmental changes. Therefore, we determined the effects of temperature, food, size of juvenile snails, substratum type, and density of juvenile snails on the aggregation behavior of N. cumingii. Results show that, at a low (4°C) or a high (22°C) temperature, juvenile snails adjusted to the inhospitable environment by exhibiting increased aggregation behavior. However, their aggregation behaviors differed at these two temperatures. There was no significant difference in the aggregation rate, but the typical aggregation size was larger at 4°C than at 22°C. At 10°C or 16°C, aggregation behavior of juvenile snails reduced. Aggregation increased in the satiation treatment at 10°C and 16°C. Small-sized juveniles tended to have higher aggregation rates (92.22%) and a larger typical aggregation size. More juveniles were distributed in the bottom of shaded substrata. A larger typical aggregation size or higher density significantly reduced the mortality of juvenile snails at a low temperature (4°C). These results broaden our understanding of gastropod aggregation behavior and can be used to develop and improve commercial breeding strategies and resource recovery for N. cumingii.

The effects of model proteins (OVA: ovalbumin and BSA: bovine serum albumin) on the colloidal stability of graphene oxide (GO) with different lateral sizes (around 1000, 500, 350 and 200 nm, respectively) were investigated. At low salt concentrations, the aggregation rate (k) of GO displayed a parabolic relationship: it increased until kfast (regime I), remained at kfast (regime II), and then decreased gradually to zero (regime III), with the increase of protein concentrations at environmental pH (4, 6 and 9). Compared to BSA, much higher concentrations of OVA were needed to achieve similar effects on GO stability induced by BSA, since OVA has a smaller molecular size and fewer positively charged groups. In regime I, the k of GO increased with the increase of lateral size at the same concentration of proteins, and a higher dosage of proteins was needed to drive k to kfast for smaller sized GO. However, there was no such lateral size dependent effect in regime III, which was attributed to the predominance of steric repulsion caused by the large amount of proteins. In regime I, GO displayed higher stability at higher pH, and thus more proteins were required to drive k to kfast. In regime III, the proteins were more effective in stabilizing GO under higher pH conditions due to the enhanced electrostatic and steric repulsion. This study highlights the crucial effects of the GO lateral size, protein properties and concentrations, as well as solution chemistry, on GO stability in aquatic environments.

Despite years of intensive research, little is known about oligomeric structures present during Alzheimer's disease (AD). Excess of amyloid beta (Aβ) peptides and their aggregation are the basis of the amyloid cascade hypothesis, which attempts to explain the causes of AD. Because of the intrinsically disordered nature of Aβ monomers and the high aggregation rate of oligomers, their structures are almost impossible to resolve using experimental methods. For this reason, we used a physics-based coarse-grained force field to extensively search for the conformational space of the Aβ42 tetramer, which is believed to be the smallest stable Aβ oligomer and the most toxic one. The resulting structures were subsequently optimized, tested for stability, and compared with the proposed experimental fibril models, using molecular dynamics simulations in two popular all-atom force fields. Our results show that the Aβ42 tetramer can form polymorphic stable structures, which may explain different pathways of Aβ aggregation. The models obtained comprise the outer and core chains and, therefore, are significantly different from the structure of mature fibrils. We found that interaction with water is the reason why the tetramer is more compact and less dry inside than fibrils. Physicochemical properties of the proposed all-atom structures are consistent with the available experimental observations and theoretical expectations. Therefore, we provide possible models for further study and design of higher order oligomers.

Nanoparticles, especially natural nanoparticles, are closely related to many environmental processes. In this study, the aggregation kinetics of goethite nanoparticles (GNPs) in the presence of Mg(NO3)2, Ca(NO3)2 and Cu(NO3)2 were investigated by dynamic light scattering. The specific cation effects of Cu2+, Ca2+ and Mg2+ on the aggregation of the positively charged GNPs were observed. The results showed that: (1) the mean aggregation rate followed the order of Cu2+

The aggregation of amyloid-𝛽 (A𝛽) proteins through their self-assembly into oligomers, fibrils, or senile plaques is advocated as a key process of Alzheimer's disease. Recent studies have revealed that metal ions play an essential role in modulating the aggregation rate of amyloid-𝛽 (A𝛽) into senile plaques because of high binding affinity between A𝛽 proteins and metal ions. In this paper, we proposed a mathematical model as a set of coupled kinetic equations that models the self-assembly of amyloid-𝛽 (A𝛽) proteins in the presence of metal ions. The numerical simulations capture four timescales in the A𝛽 dynamics associated with three important events which include the formation of the amyloid-metal complex, the homogeneous aggregation of the amyloid-metal complexes, and the non-homogeneous aggregation of the amyloid-metal complexes. The method of singular perturbation is used to identify these timescales in the framework of slow-fast systems.

This article investigates solar photovoltaic deployment through community choice aggregation programs. A case study of a solar energy program facilitated through a public energy council in Southeastern Ohio is highlighted, which used a ‘carbon fee’ model to collect a 0.2 cents per kilowatt hour incremental fee above the standard aggregation rate. This premium funds the development of behind-the-meter solar installations, and may serve as an exemplary approach for other aggregation programs to deploy solar.

Soil degradation is a global issue, as the demand for food and feed consumption is growing rapidly every day, and agricultural land needed for their production is declining rapidly. The UN reports that 24 billion tons of fertile land are lost every year. One of the most important parameters causing and maintaining soil fertility is the presence of water-stable macroaggregates (> 0.25 mm) with a developed porous structure. In natural soil, aggregate formation occurs under the following main processes – coagulation with polyvalent cations, “glueing”/cementation under the action of mineral amorphous "glues" (silica, metal oxides/ hydroxides) and organic amphiphilic substances (microbial exopolymers and humic substances). In this research work we estimated the impact of bio-nanocomposite and its individual constituents with structure forming ability on the remediation efficacy of a degraded soil model sample.The bio-nanocomposite was synthesised from active sludge. The composition of the bio-nanocomposite includes mineral matter – 36 %, organic matter – 64 %, humic acids, fulvic acids, ammonifying bacteria, nitrate-assimilating bacteria, actinomycetes, fungi, and metal nanoparticles in form of insoluble or sparingly soluble salts. To assess the effect of the concentration of bio-nanocomposite on the aggregation of soil colloids, the nanocomposites were added to the model soil system in concentrations of 1%, 2.5%, 5%, 10%, 20% and 50%, and compared with control unenriched soil. The dynamics of soil colloids aggregation was assessed by the value of the optical density of aqueous suspensions at four months. The results indicate a correlation between the concentration of the introduced bio-nanocomposite and the degree of soil colloids aggregation – up to 70% after 2 months of incubation and up to 80% after 4 months. Analysis of the impact on the structure-forming processes of individual constituents of the bio-nanocomposite showed that nanoparticles of polyvalent metals made the most significant contribution (82 %), humic and fulvic acids had slightly less influence (80% and 78%, respectively). Exopolymers had the weakest effect on aggregation processes. Since exopolymers act as natural flocculants, their flocculating properties are highly dependent on the concentration, and at high concentrations they can stabilize colloidal particles.

Protein aggregation is a topic of immense interest to the scientific community due to its role in several neurodegenerative diseases/disorders and industrial importance. Several in silico techniques, tools, and algorithms have been developed to predict aggregation in proteins and understand the aggregation mechanisms. This review attempts to provide an essence of the vast developments in in silico approaches, resources available, and future perspectives. It reviews aggregation-related databases, mechanistic models (aggregation-prone region and aggregation propensity prediction), kinetic models (aggregation rate prediction), and molecular dynamics studies related to aggregation. With a multitude of prediction models related to aggregation already available to the scientific community, the field of protein aggregation is rapidly maturing to tackle new applications.

The propensity for intrinsically disordered proteins to aggregate is heavily influenced by their surrounding environment. Here, we show that the mobility of the surrounding water molecules directly influences the aggregation rate of α-synuclein (aSyn), a protein associated with Parkinson’s disease. We observe that the addition of NaCl reduces the mobility of water, while addition of CsI increases the mobility of water. In turn, this reduces and increases the mobility of aSyn, respectively, given the change in strength and lifetime of the intermolecular forces. The reduction of aSyn mobility in the presence of NaCl ions leads to increased aggregation rates, which may be due to aggregation-competent conformations being stable for longer, thereby increasing the likelihood of establishing interactions between two adjacent monomers. In contrast, aSyn is more mobile when CsI is dissolved in the aqueous phase which leads to a reduction of successful monomeric interactions. We thus highlight the importance of the surrounding environment and describe how ion content can influence water mobility and the misfolding rate of amyloidogenic proteins, such as aSyn. By modulating the cellular environment to increase water mobility or finding small molecules to increase protein dynamics, new therapeutic targets may be found.

More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and pH all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks.

A comprehensive green worker ants control method that can be used to replace traditional chemical synthetic insecticides. In this study, the leaves and stems of Gelsemium elegans were extracted with water as the solvent, and the bioactivity of G. elegans against worker ants was determined by the “water tube” method. The bioassay results of insecticidal activity showed that when the time was extended to the 10th day, the mortality of worker ants treated with G. elegans extract reached 55.00% (1/20 leaf extract), 46.67% (1/20 stem extract) and 45.00% (1 mg/kg koumine). And the behavioral impact test results showed that the aggregation rate was reduced to 56.67% (1/100 leaf extract), 60.00% (1/100 stem extract) and 60.00% (0.5 mg/kg koumine); the climbing rate was reduced to 60.00 % (1/100 leaf extract), 58.33% (1/100 stem extract) and 58.33% (0.5 mg/kg koumine). The effect on the walking ability of worker ants is obvious. The walking rate drops to 1.53cm/s (1/100 leaf extract), 1.60cm/s (1/100 stem extract) and 1.47cm/s (0.5 mg/kg koumine). Therefore, we conclude that the water extract of G. elegans can be used for long-term continuous control of worker ants, which can be used to replace traditional chemical synthetic insecticides.

China has experienced severe hazes with high concentrations of particulate matter in recent years. The understanding of the size spectrum evolution of submicron particulate matter is critical to making efficient remediation policies to minimize the regional and global environmental impacts from hazes. During a time period of about one month, we monitored five severe haze episodes in Xi’an and four severe haze episodes in Beijing, which were characterized by two distinct kinds of aerosol mass concentration growth processes: accumulative-rise and abrupt-rise. A new method was developed to quantitatively evaluate the physical and chemical contributions to growth processes by analysing the size spectrum evolution data. The results showed that the accumulative-rise processes are governed by primary emissions and the abrupt-rise processes are governed by secondary chemical reactions. The population balance equations (PBE) were used to describe the variation of size spectrum of fine particulate matter, and the respective contributions of the physical aggregation rate and the chemical growth rate. The PBE model is solved using the adjustable direct quadrature method of moments (ADQMOM) to simulate the abrupt-rise process of haze development and to calibrate the contribution of the physical and chemical effects on the size spectrum of aerosol particles.

The effect of Ca2+ and alginate on the stability of CeO2 nanoparticles (NPs) was investigated using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA); the two methods were then compared. DLS showed rapid aggregation of CeO2 NPs in 8 mM Ca2+ solution; however, NTA showed that some primary aggregates (200–400 nm) still remained—a result that was obscured in DLS measurements. Aggregation of alginate molecules was also studied using DLS and NTA, where NTA particle concentration and video provided additional information on the alginate aggregation progress. Finally, DLS showed that in the presence of alginate, the aggregation rate and size of CeO2 NPs increased. NTA intensity measurements provided insight into a heteroaggregation and bridging mechanism. NTA particle concentration and video also showed CeO2 NPs were linked by alginate gel in high Ca2+ concentration (>4 mM). the DLS and NTA had different advantages in measuring particle size. DLS could better study the initial aggregation stage and large aggregates, while NTA could better detect small aggregates. NTA also measured particle number concentration, individual intensity, and particle motion video, which provided additional insight. Combining these two methods could help us to better understand the behavior and fate of NPs in water.

Controlling particle size is important in powder technology. Here we report a scalable production process of mesoporous calcium carbonate with a controllable particle size. We focus on the effect of the aggregation rate on the obtained particles. In this study, we change the particle concentration (1.2–12 mass%) to control the aggregation rate and then obtained particles with relatively narrow range of particle size (310 ± 30–560 ± 100 nm) and nearly identical specific surface areas and particle structures by template-free method. We proposed the aggregation model to describe the formation of meso-porous calcium carbonate.

The purpose of the study is to identify the peculiarities of the functioning of the vascular-thrombocyte linkage of hemostasis in the experimental periodontitis. Material and methods. Experimental manipulations were performed on white nonlinear male rats weighing 260.0 ± 30.0 g, in which experimental periodontitis was induced. Determination of total, free and bound oxyproline in urine was carried out using the method of P. N. Sharaev. Analysis of the aggregation curve included the definition of such indicators: 1) the degree of aggregation — the maximum% of light transmission of the plasma; 2) time to achieve maximum aggregation rate — time to achieve maximum% light transmission; 3) the rate of aggregation, which was calculated 30 seconds after the beginning of platelet aggregation. Results. Studying the functional activity of platelets in rats with experimental periodontitis revealed signs of changes in the functions of the platelet linkage hemostasis. In periodontitis in connective tissue periodontium and thrombocyte hemostasis, metabolic disorders of the connective tissue were revealed, which is the level of oxyproline in the urine of animals. Conclusions. In the experimental periodontitis, clear changes in the functional activity of the platelets were detected. In parallel with the decrease in the functional activity of platelets in the periodontitis, the level of urine in all three oxyproline fractions is reduced. The obtained results testify to the commonality of processes occurring in the blood and connective tissue and associated with metabolic disorders in it, decrease in the synthesis and collagen collapse.

To gain insight into the colloidal stability in the presence of proteins, we measured the electrophoretic mobility and aggregation rate constant of silica particles coated with lysozymes, and the adsorbed amount of lysozymes on the silica. We also examined model analyses, which are based on the Derjaguin, Landau, Verwey, and Overbeek theory with the effect of charge heterogeneity, to discuss the aggregation of lysozyme-coated silica. Our results show that lysozymes enhance the aggregation of silica when the lysozyme-coated silica is near the isoelectric point. When the adsorbed amount of lysozyme is low, the effect of charge-patch attractive force promotes the aggregation of silica. The effect of charge heterogeneity weakens with the increase of adsorbed amount of lysozyme. Our model which takes account of the effect of charge heterogeneity can capture the trend of the aggregation of silica in the presence of lysozyme qualitatively, but there are also large quantitative discrepancies between the theoretical prediction and experimental results. Further improvement is required to describe realistic charge heterogeneity and the effect of the surface coverage of lysozyme on the silica.

Protein aggregation has two aspects, namely, mechanistic and kinetics. Understanding protein aggregation kinetics is critical for prediction of progression of diseases caused by amyloidosis, accumulation of aggregates in biotherapeutics during storage and engineering commercial nano-biomaterials. In this work, we have collected experimentally determined absolute protein aggregation rates and developed an SVM based regression model to predict absolute rates of protein and peptide aggregation near-physiological conditions. The regression model achieved a correlation coefficient of 0.72 with MAE of 0.91 (natural log of kapp, where kapp is in hour-1) using leave-one-out cross-validation on a dataset of 82 non-redundant proteins/peptides. The model accounts for the experimental conditions (such as temperature, pH, ionic and protein concentration) and sequence-based properties. The amino acid sequence features revealed by this model as being important for aggregation kinetics, are also associated with the aggregation mechanism. In particular, inherent aggregation propensity of the protein/peptide sequence and number of aggregation prone regions (APRs) unpunctuated by the gatekeeping residues, were found to play important roles in the prediction of the absolute aggregation rates. This analysis shows that mechanism and kinetics of protein aggregation are coupled via common sequence attributes. The aggregation kinetic prediction method developed in this work is available at https://web.iitm.ac.in/bioinfo2/absolurate-pred/index.html.

Selecting optimal formulation conditions for monoclonal antibodies for first time in human clinical trials is challenging due to short timelines and reliance on predictive assays to ensure product quality and adequate long-term stability. Accelerated stability studies are considered to be the gold standard for excipient screening, but they are relatively low throughput and time consuming. High throughput screening (HTS) techniques allow for large amounts of data to be collected quickly and easily, and can be used to screen solution conditions for early formulation development. The utility of using accelerated stability compared to HTS techniques (differential scanning light scattering and differential scanning fluorescence) for early formulation screening was evaluated along with the impact of excipients of various types on aggregation of monoclonal antibodies from multiple IgG subtypes. The excipient rank order using quantitative HTS measures was found to correlate with accelerated stability aggregation rate ranking for only 33% (by differential scanning fluorescence) to 42% (by differential scanning light scattering) of the antibodies tested, due to the high intrinsic stability and minimal impact of excipients on aggregation rates and HTS data. Also explored was a case study of employing a platform formulation instead of broader formulation screening for early formulation development.

We studied dynamic scaling law for the early stage domain growth in the micelle aggregation process of dispersed surfactant molecules in water for zwitterionic dodecyldimethylamine oxide (DDAO) and...

The dynamics of molecules or nanoparticles (NPs) at solid-liquid interfaces plays an important role in many natural and industrial processes. However, the effects of a solid-liquid interface on NP motion and on the interactions between these NPs is still not well understood. Here, using in situ liquid cell transmission electron microscopy (TEM), we directly observed the movement of gold NPs and their aggregation dynamics at solid-liquid interfaces. We found that the solid surfaces transiently pin the NPs during their aggregation, dampening their translational and rotational movements. This surface pinning reduces both the movement of NPs and their aggregation rate as the aggregates grow by attachment. However, the pinning of the NP aggregates affects their translational and rotational motions differently. Initially, with increasing aggregate size, the aggregate's translational motion dampens more than its rotational motion. Consequently, the initial aggregation stages are driven by both the translational and rotational motions, whereas the rotational motion dominates the later aggregation stages. Our results provide insight into the movements of NPs and their aggregates at solid-liquid interfaces, which may assist in the future design and control of NP assemblies at interfaces.