Formation Of Clusters Research Articles

Dynamics and thermochemistry of the negatively charged clusters in a 2-hydroxyethylhydrazinium nitrate ionic liquid system.

The formation and fragmentation of negatively charged 2-hydroxyethylhydrazinium nitrate ([HOCH2CH2NH2NH2]+NO3-, HEHN) ionic liquid clusters were examined using a guided-ion beam tandem mass spectrometer furnished with collision-induced dissociation of selected ions with Xe atoms. Measurements included the compositions of cluster ions formed in the ionization source, and the dissociation products, cross sections, and 0 K threshold energies for individually selected cluster ions. To identify the structures of the main cluster ion series [(HEHN)n(HNO3)0-1NO3]- formed, molecular dynamics simulations were employed to create initial geometry guesses, followed by optimization at the ωB97XD/6-31+G(d,p) level of theory, from which global minimum structures were identified for reaction thermodynamics analyses. A comparison was made between the cluster formation and fragmentation in the negatively charged 2-hydroxyethylhydrazinium nitrate with those in the positive mode (reported by W. Zhou et al., Phys. Chem. Chem. Phys., 2023, 25, 17370). In both modes, the cluster ions were predominantly composed of m/z below 350; loss of a neutral 2-hydroxyethylhydrazinium nitrate ion pair represents the most important cluster fragmentation pathway, followed by intra-ion pair proton transfer-mediated 2-hydroxyethylhydrazine and HNO3 elimination; and all clusters started to dissociate at threshold energies less than 1.5 eV. The overwhelming similarities in the formation and fragmentation chemistry of positively vs. negatively charged 2-hydroxyethylhydrazinium nitrate clusters may be attributed to their inherent ionic nature and high electric conductivities.

The sunflower jacalin Helja: biological and structural insights of its antifungal activity against Candida albicans.

The limited availability of efficient treatments for Candida infections and the increased emergence of antifungal-resistant strains stimulates the search for new antifungal agents. We have previously isolated a sunflower mannose-binding lectin (Helja) with antifungal activity against Candida albicans, capable of binding mannose-bearing oligosaccharides exposed on the cell surface. This work aimed to investigate the biological and biophysical basis of Helja's binding to C. albicans cell wall mannans and its influence on the fungicidal activity of the lectin. We evaluated the interaction of Helja with the cell wall mannans extracted from the isogenic parental strain (WT) and a glycosylation-defective C. albicans with altered cell wall phosphomannosylation (mnn4∆ null mutants) and investigated its antifungal effect. Helja exhibited stronger antifungal activity on the mutant strain, showing greater inhibition of fungal growth, loss of cell viability, morphological alteration, and formation of clusters with agglutinated cells. This differential biological activity of Helja was correlated with the biophysical parameters determined by solid phase assays and isothermal titration calorimetry, which demonstrated that the lectin established stronger interactions with the cell wall of the mnn4∆ null mutant than with the WT strain. In conclusion, our results provide new evidence on the nature of the Helja molecular interactions with cell wall components, i.e. phosphomannan, and its impact on the antifungal activity. This study highlights the relevance of plant lectins in the design of effective antifungal therapies.

Lack of knowledge about the human papillomavirus vaccine among Brazilian adolescents: A cross-sectional study.

To analyze the distribution and factors associated with lack of knowledge about the human papillomavirus (HPV) vaccine among Brazilian adolescents.Cross-sectional study using the 2019 National School Health Survey among 17,805 Brazilian students of public and private schools, aged 13-17 years. The outcome variable was "lack of knowledge about the HPV vaccine" and the explanatory variables were sociodemographic, behaviors, knowledge, and health conditions. Logistic regression model was used to calculate Odds Ratio (OR) and 95% confidence intervals (95%CI). Spatial analysis techniques were used to determine the formation of clusters in the federated units with similar proportions of adolescents who were unaware of the vaccine. The lack of knowledge about the HPV vaccine was reported by 45.54% of Brazilian students. There was a higher chance of lack of knowledge having had sexual intercourse (OR 1.43; 95% CI 1.20-1.70); attending public school (OR 1.72; 95%CI 1.47-2.02) and located in the Northeast Region (OR 1.35; 95%CI 1.08-1.69). The lower chance of lack of knowledge were female gender (OR 0.41; 95% CI 0.35-0.48), higher maternal education (OR 0.62; 95% CI 0.50-0.77) self-rated health as Poor/very poor (OR 0.64; 95% CI 0.49-0.86) and receiving contraceptive counseling (OR 0.77; 95% CI 0.65-0.91). The proportion of lack of knowledge about the HPV vaccine was higher with the formation of High-High spatial clusters in the states of Maranhão, Piauí, and Pernambuco. Sociodemographic, health, and behavioral conditions and knowledge of students, as well as school characteristics, were associated with lack of knowledge about the HPV vaccine. A higher frequency of lack of knowledge about the HPV vaccine among adolescents was found in the states of the Northeastern Region.

Zinc phosphate glass microspheres promoted mineralization and expression of BMP2 in MC3T3-E1 cells.

Degradable phosphate glasses have shown favorable properties for tissue engineering. By changing the composition of the glasses, the degradation rate, and ion release are controllable. Zinc oxide can function as a glass network modifier and has been shown to play a positive role in bone formation. Also, phosphate glasses can easily be processed into microspheres, which can be used as microcarriers. This study aims to develop zinc phosphate glasses microspheres and explore the optimized size and composition for applications in bone tissue engineering. Zinc-titanium-calcium-sodium phosphate glasses with 0, 1, 3, 5, or 10 mol % zinc oxide were prepared and processed into microspheres. The smaller microspheres ranged in size from 50 to 106 μm, while the larger ones ranged from 106 to 150 μm. The characteristics of glasses were examined. The osteoblastic cell line MC3T3-E1 was cultured on the surface of microspheres and the cell viability was examined. To evaluate osteogenic differentiation, Alizarin Red S staining, quantitative reverse transcription polymerase chain reaction, and western blot analysis were performed after 14 days. Different sizes of zinc phosphate glass microspheres were successfully made. The glass microspheres with <10 mol % zinc oxide were able to support the adhesion and proliferation of MC3T3-E1 cell lines. The relative gene expression of BMP2 was significantly upregulated in the smaller glass microspheres containing 3 mol % zinc oxide (26-fold, p < .001) and both sizes of microspheres containing 5 mol % zinc oxide (smaller: 27-fold, p < .001; larger: 35-fold, p < .001). Additionally, cluster formation was observed in glass microspheres after 14 days, and the mineralization of MC3T3-E1 cell lines was promoted. Based on these findings, the glass microspheres containing 3-5 mol % of zinc oxide can promote osteogenic differentiation for MC3T3-E1 cells.

Three-Dimensional Integrated Synaptic Devices Based on a Silver-Cluster Conduction Mechanism with High Thermostability.

During the operation of synaptic devices based on traditional conductive filament (CF) models, the formation and dissolution of CFs are usually uncertain. Moreover, when the device is operated for a long time, the CFs may dissolve due to both the Joule heat generated by the device itself and the thermal coupling between the devices. These problems seriously reduce the reliability and stability of the synaptic device. Here, an artificial synapse device based on polyimide-molybdenum disulfide quantum dot (MoS2 QD) nanocomposites is presented. Research has shown that MoS2 QDs doped into the active layer can effectively induce the reduction of Ag ions into Ag atoms, leading to the formation of Ag clusters and thereby achieving control over the growth of the CFs. Therefore, the device is capable of stably realizing various basic synaptic functions. Moreover, the long-term potentiation/long-term depression (LTP/LTD) of this device shows good linearity. In addition, due to the change in the shape of the CFs, the highly integrated devices with a three-dimensional (3D) stacked structure can operate normally even in a high-temperature environment of 110 °C. Finally, the synaptic characteristics of the devices on learning and inference tests show that their recognition rates are approximately 90.75% (room temperature) and 90.63% (110 °C).

Reciprocal regulation of T follicular helper cells and dendritic cells drives colitis development.

The immunological mechanisms underlying chronic colitis are poorly understood. T follicular helper (TFH) cells are critical in helping B cells during germinal center reactions. In a T cell transfer colitis model, a lymphoid structure composed of mature dendritic cells (DCs) and TFH cells was found within T cell zones of colonic lymphoid follicles. TFH cells were required for mature DC accumulation, the formation of DC-T cell clusters and colitis development. Moreover, DCs promoted TFH cell differentiation, contributing to colitis development. A lineage-tracing analysis showed that, following migration to the lamina propria, TFH cells transdifferentiated into long-lived pathogenic TH1 cells, promoting colitis development. Our findings have therefore demonstrated the reciprocal regulation of TFH cells and DCs in colonic lymphoid follicles, which is critical in chronic colitis pathogenesis.

Strategies for the Co-Delivery of Osteoclasts and MSCs in 3D-Printable Osteochondral Scaffolds.

Osteochondral defects, characterized by structural compromises to articular cartilage and subchondral bone, can cause pain and lead to progressive cartilage damage and eventual osteoarthritis. Unfortunately, repairing these defects remains difficult due to the poor regenerative properties of cartilage and complex mechanical demands of the joint. As such, the field of tissue engineering aims to develop multiphasic implants that replace pathological cartilage and bone tissue and restore mechanical functionality to the joint. Recent bone physiology investigations have demonstrated that osteoclast lineage cells are inextricably involved in osteoblastic bone formation through an extensive network of anabolic signaling pathways, and so the co-delivery osteoclast and osteoblast lineage cells within scaffolds is being actively explored for bone tissue engineering purposes. However, it remains unclear how these cells can be incorporated into the design of multiphasic osteochondral scaffolds to potentially enhance subchondral bone formation and subsequent implant osseointegration. To explore this question, we examined direct surface seeding and hydrogel encapsulation as potential scaffold cellularization strategies. First, we examined how osteoclast precursor cells (OCps) and peripheral blood monocytes (PBMCs) influence early-stage bone matrix development and osteogenesis in 2D co-culture. Then, we evaluated the osteogenic potential of mesenchymal stem cells (MSCs) and PBMCs co-cultures encapsulated within a gelatin methacrylate (GelMA) hydrogel system. Our findings demonstrate that co-culturing PBMCs with MSCs in 2D cultures significantly enhanced cell proliferation, early bone matrix deposition, and the formation of cell clusters by Day 28. However, we observed no significant difference in Type I collagen (COLI) deposition between GelMA hydrogel scaffolds cultured in basal and OC conditions during the same period. Additionally, we found that the GelMA hydrogel system with MSC/PBMC co-cultures in OC conditions exhibited decreased osteogenic activity by Day 28. Collectively, our findings support the osteogenic potential of osteoclast-lineage cells in 2D culture conditions, and the potential benefits of surface-seeding for the co-delivery of osteoclast-lineage cells and MSCs in osteo-scaffolds for enhanced osteochondral regeneration and broader bone tissue engineering purposes.

Ab initio study of helium behavior near stacking faults in 3C-SiC

First-principles calculations are used to investigate the effects of stacking faults (SFs) on helium trapping and diffusion in cubic silicon carbon (3C-SiC). Both extrinsic and intrinsic SFs in 3C-SiC create a hexagonal stacking sequence. The hexagonal structure is found to be a strong sink of a helium interstitial. Compared to perfect 3C-SiC, the energy barriers for helium migration near the SFs increase significantly, leading to predominant helium diffusion between the SFs in two dimensions. This facilitates the migration of helium towards interface traps, as confirmed by previous experimental reports on the nanocrystalline 3C-SiC containing a high density of SFs. This study also reveals that the formation of helium interstitial clusters near the SFs is not energetically favored. The findings from this study enhance our comprehension of helium behavior in faulted 3C-SiC, offering valuable insights for the design of helium-tolerant SiC materials intended for reactor applications.

A Unique Wide‐Spacing Fence‐Type Superstructure for Robust High‐Voltage O3‐Type Sodium Layered Cathode

AbstractEnhancing the energy density of layered oxide cathode materials is of great significance for realizing high‐performance sodium‐ion batteries and promoting their commercial application. Lattice oxygen redox at high voltage usually enables a high capacity and energy density. But the structural degradation, severe voltage decay, and the resultant poor cycling performance caused by irreversible oxygen release seriously restrict the practical application. Herein we introduce a novel fence‐type superstructure (2a×3a type supercell) into O3‐type layered cathode material Na0.9Li0.1Ni0.3Mn0.3Ti0.3O2 and achieve a stable cycling performance at a high voltage of 4.4 V. The fence‐type superstructure effectively inhibits the formation of the vacancy clusters resulting from out‐of‐plane Li migration and in‐plane transition metal migration at high voltage due to the wide d‐spacing, thereby significantly reducing the irreversible release of lattice oxygen and greatly stabilizing the crystal structure. The cathode exhibits a high energy density of 545 Wh kg−1, a high rate capability (112.8 mAh g−1 at 5 C) and a high cycling stability (85.8 %@200 cycles with a high initial capacity of 148.6 mAh g−1 at 1 C) accompanied by negligible voltage attenuation (98.5 %@200 cycles). This strategy provides a distinct spacing effect of superstructure to design stable high‐voltage layered cathode materials for Na‐ion batteries.

Overlooked Impacts of Alcohols in Electro-H2O2 and Fenton Chemistry.

Alcohols are promising fuels for direct alcohol fuel cells and are common scavengers to identify reactive oxygen species (ROS) in electro-Fenton (EF) systems. However, the side impacts of alcohols on oxygen reduction reactions and ROS generation are controversial due to the complex interactions between electrodes and alcohol-containing electrolytes. Herein, we employed synchrotron-Fourier-transform infrared spectroscopy and electron paramagnetic resonance technologies to directly observe the changes of chemical species and electrochemical properties on the electrode surface. Our studies suggested that alcohols exhibited different limiting degrees on proton (H+) mass transfer toward the catalytic surface, following an order of methanol < ethanol < isopropanol < tert-butyl alcohol (TBA). In addition, the formation of hydrophobic TBA clusters at high concentrations (>400 mM) resulted in a significant reduction in ionic conductivity and an elevation in charge transfer resistance, which impedes H+ mass transfer and raises the energy barrier for 2e- oxygen reduction reaction processes. Moreover, the organic radical •CH2(CH3)2CH2OH produced by the interaction of Fe3+ and •OH with the alcohol in the EF system serves as a crucial intermediate in facilitating H2O2 regeneration, which complicates the quenching effect of alcohols on •OH identification. Therefore, it is recommended that methanol should be used as the scavenger instead of TBA and the concentration should be less than 400 mM in EF systems.

Formation of low-coordination Pt clusters on Al vacancy-induced CoAl layered double hydroxides-derived oxides enhances low-temperature oxidation performance of HCHO

Noble metal loading and oxygen vacancy construction are prevalent strategies to enhance catalyst performance in HCHO catalytic oxidation. For noble metal systems, most cutting-edge research focuses on single atoms, including the exploration of coexistence between single atoms and clusters, yet there are few reports on the impact of noble metal clusters with different coordinations on catalyst performance. Additionally, investigations into metal vacancies, as opposed to oxygen vacancies, are also scarce. In this work, we used CoAl layered double hydroxides (LDHs) as a precursor, which, after calcination and etching, yielded derived oxides with Al vacancies (LDO5). Pt was then loaded onto the surface of these oxides via impregnation (Pt/LDO5). Activity tests demonstrated that Pt/LDO5 exhibited superior HCHO oxidation activity, especially at low temperatures, compared to Pt/LDO. Utilizing high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS), we discovered that, in contrast to the “standard” Pt clusters on the LDO surface, Pt primarily existed as low-coordination clusters on the LDO5 surface, even with a higher Pt loading. Moreover, the coexistence of Al vacancies and low-coordination Pt clusters effectively enhanced the spin state of Co species in the support and altered the direction of electron transfer between Pt and the support.

Analysis of Normal Plasma Cell Distribution Across Distinct Age Cohorts Reveals Age-Dependent Changes.

Hematopoietic and stromal cells within the bone marrow (BM) provide membrane-bound and/or soluble factors that are vital for the survival of plasma cells (PCs). Recent reports in murine BM demonstrated the dynamic formation and dispersion of PC clusters. To date, PC clustering in normal human BM has yet to be thoroughly examined. The goal of this study was to determine whether PC clusters are present in human BM and whether clustering changes as a function of age. Quantification of PCs and clustering in BM sections across six different age groups revealed that fewer PCs and PC clusters were observed in the youngest and oldest age groups. PC clustering increased with age until the sixth decade and then began to decrease. A positive correlation between the number of PCs and PC clusters was observed across all age groups. PC clusters were typically heterogeneous for immunoglobulin heavy- and light-chain expression. Taken together, these data demonstrate that PC clusters are present in human BM and that PC clustering increases until middle adulthood and then begins to diminish. These results suggest the spatial distribution of BM PC-supportive stromal cells changes with age.

Cation valency in water-in-salt electrolytes alters the short- and long-range structure of the electrical double layer

Highly concentrated aqueous electrolytes (termed water-in-salt electrolytes, WiSEs) at solid-liquid interfaces are ubiquitous in myriad applications including biological signaling, electrosynthesis, and energy storage. This interface, known as the electrical double layer (EDL), has a different structure in WiSEs than in dilute electrolytes. Here, we investigate how divalent salts [zinc bis(trifluoromethylsulfonyl)imide, Zn(TFSI)2], as well as mixtures of mono- and divalent salts [lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) mixed with Zn(TFSI)2], affect the short- and long-range structure of the EDL under confinement using a multimodal combination of scattering, spectroscopy, and surface forces measurements. Raman spectroscopy of bulk electrolytes suggests that the cation is closely associated with the anion regardless of valency. Wide-angle X-ray scattering reveals that all bulk electrolytes form ion clusters; however, the clusters are suppressed with increasing concentration of the divalent ion. To probe the EDL under confinement, we use a Surface Forces Apparatus and demonstrate that the thickness of the adsorbed layer of ions at the interface grows with increasing divalent ion concentration. Multiple interfacial layers form following this adlayer; their thicknesses appear dependent on anion size, rather than cation. Importantly, all electrolytes exhibit very long electrostatic decay lengths that are insensitive to valency. It is likely that in the WiSE regime, electrostatic screening is mediated by the formation of ion clusters rather than individual well-solvated ions. This work contributes to understanding the structure and charge-neutralization mechanism in this class of electrolytes and the interfacial behavior of mixed-electrolyte systems encountered in electrochemistry and biology.

Computational modeling of cell motility and clusters formation in enzyme-sensitive hydrogels

AbstractIn this paper, we propose an extension of a previous model of cell motility in tissue engineering applications recently developed by the authors. Achieving large-scale production of neo-tissue through biofabrication technologies remains challenging owing to the need of thoroughly optimizing all the relevant process variables, a task hardly attainable through solely trial and error approaches. Therefore, the present work is intended to provide a valid and effective computational-based support for neo-tissue formation, with a specific focus on the preliminary phase of such process, in which cells move through a polymeric scaffold (hydrogel) and then compact into clusters. Cell motility is modeled by resorting to the phase-field method, and by incorporating diffusion of nutrients from the external culture bath as well as the expression by cells of chemoattractant substances that bias the random path they otherwise would follow. The previous model has been enriched by additionally encompassing the secretion of enzymes by cells that cleave the crosslinks between the hydrogel polymer chains. As such, in the present model hydrogel degradation exhibits spatio-temporal variations in its chemo-physical properties related to the local amount of enzymes, which deeply affects cell motility. Numerical results showcase the pivotal importance of the cells micro-environment properties for their crawling in hydrogel scaffolds, opening towards the development of a predictive computational-aided optimization tool for neo-tissue growth in bioprinted scaffolds.

Synthesis of Dual-Responsive Amphiphilic Glycomacromolecules: Controlled Release of Glycan Ligands via pH and UV Stimuli.

This work presents a versatile strategy for the synthesis of dual stimuli-responsive amphiphilic glycomacromolecules with tailored release properties. Amphiphilic precision glycomacromolecules (APGs) derived from tailor-made building blocks using solid phase polymer synthesis form glycofunctionalized micelles, a versatile class of materials with applications in drug delivery, as antiinfection agents as well as simple cell mimetics. In this work, this concept is extended by integrating cleavable building blocks into APGs now allowing stimuli-responsive release of glycan ligands or destruction of the micelles. This study incorporates a newly designed acid-labile building block, 4-(4-(((((9H-fluoren-9-yl)methoxy)carbonyl)amino)methyl)-1,3-dioxolan-2-yl)benzoic acid (DBA), suitable also for other types of solid phase or amide chemistry, and an established UV-cleavable 2-nitrobenzyl linker (PL). The results demonstrate that both linkers can be cleaved independently and thus allow dual stimuli-responsive release from the APG micelles. By choosing the APG design e.g., placing the cleavable linkers between glycomacromolecular blocks presenting different types of carbohydrates, they can tune APG and micellar stability as well as the interaction and cluster formation with a carbohydrate-recognizing lectin. Such dual-responsive glycofunctionalized micelles have wide potential for use in drug delivery applications or for the development as anti-adhesion agents in antiviral and antibacterial treatments.

Synthesis and Characterization of Alkali Metal Hypersilyl Borates

AbstractThis study focuses on the synthesis of H‐ and MeO‐ functionalized alkali metal hypersilyl borates. Consequently, two distinct silanides were used as polysilane frameworks for our chemical manipulations. Tris(silyl)silanide (1) and tris(trimethoxysilyl)silanide (2) react in the same manner with the BH3 ⋅ SMe2 complex to obtain two new alkali metal hypersilyl borates [(R3Si)3SiBH3M (M=alkali metal; R=H, (3), R=MeO, (4 a–c))] in good to excellent yields. NMR spectroscopy for all compounds and single‐crystal X‐ray crystallography for 3 and 4 a, b enabled a clear structural characterization. Single crystal X‐ray analysis of 3 showed a dimeric structure, where two THF‐molecules and three hydrides from the BH3‐group contribute to the coordination sphere of the lithium atom. Interestingly, crystals suitable for X‐ray analysis of 4 a and 4 b showed a solvent‐free cluster formation, due to the coordination of the MeO groups. Both species form coordination polymers with different coordination modes depending on the nature of the alkali metal. Attempted hydride abstraction reactions of 3 and 4 with various reagents under the formation of the free boranes proceeded unselectively.

Single-Atom Alloy Formation via Reaction-Driven Catalyst Restructuring.

We demonstrate that single-atom alloy catalysts can be made by exposing physical mixtures of monometallic supported Cu and Pd catalysts to vinyl acetate (VA) synthesis reaction conditions. This reaction induces the formation of mobile clusters of metal diacetate species that drive extensive metal nanoparticle restructuring, leading to atomic dispersion of the precious metal, smaller nanoparticle sizes than the parent catalysts, and high activity and selectivity for both VA synthesis and ethanol dehydrogenation reactions. This approach is scalable and appears to be generalizable to other alloy catalysts.

Spin-Glass States Generated in a van der Waals Magnet by Alkali-Ion Intercalation.

Tuning magnetic properties in layered van der Waals (vdW) materials has captured significant attention due to the efficient control of ground states by heterostructuring and external stimuli. Electron doping by electrostatic gating, interfacial charge transfer, and intercalation is particularly effective in manipulating the exchange and spin-orbit properties, resulting in a control of Curie temperature (TC) and magnetic anisotropy. Here, an uncharted role of intercalation is discovered to generate magnetic frustration. As a model study, Na atoms are intercalated into the vdW gaps of pristine Cr2Ge2Te6 (CGT) where generated magnetic frustration leads to emerging spin-glass states coexisting with a ferromagnetic order. A series of dynamic magnetic susceptibility measurements/analysis confirms the formation of magnetic clusters representing slow dynamics with a distribution of relaxation times. The intercalation also modifies other macroscopic physical parameters including the significant enhancement of TC from 66 to 240K and the switching of magnetic easy-hard axis direction. This study identifies intercalation as a unique route to generate emerging frustrated spin states in simple vdW crystals.

Pyridazine-Promoted Construction of Vinylene-Linked Covalent Organic Frameworks with Exceptional Capability of Stepwise Water Harvesting.

In this study, we successfully developed two novel vinylene-linked covalent organic frameworks (COFs) using 2-connected 3,6-dimethylpyridazine through Knoevenagel condensation. These COFs featured finely tailored micro-/nano-scale pore sizes, high surface areas and stable non-polar vinylene linkages. Finely resolved powder X-ray diffraction patterns demonstrated highly crystalline structures with a hexagonal lattice in the AA layer stacking. The resulting one-dimensional channels possess strong hydrogen-bond accepting sites arising from the decorated cis-azo/azine units with two pairs of fully exposed lone pair electrons, endowing the as-prepared COFs with exceptional water absorption properties. The g-DZPH-COF exhibited successive steep water uptake steps starting from low relative pressures (P/PSTA=0.1), with the remarkable water uptake capacity of 0.26 g/g at P/PSTA=0.2 (25 °C), which is the optimal value recorded among the reported COFs. Dynamic vapour sorption measurements revealed the fast kinetics of these COFs, even in the cluster formation process. Water uptake and release cycling tests demonstrated their outstanding hydrolytic stability, durability, and adsorption-desorption retention ability.

Polyamines putrescine and spermidine as modulators of protein aggregation rate: The effect on DTT-induced aggregation of α-lactalbumin

Protein aggregation is undesirable for cells due to its possible toxicity, and is also undesirable in biotechnology and pharmaceuticals. Polyamines are known to be capable of both suppressing and stimulating protein aggregation. In the present work polyamines (spermidine, putrescine) have been shown to alter the pathway of α-lactalbumin aggregation induced by dithiothreitol, leading to the formation of larger protein particles during the initial stages of aggregation and promoting the later stage of sticking of aggregates. According to the aggregation kinetics data, polyamines accelerate protein aggregation in a concentration-dependent manner, with a maximum at 50 mM spermidine and 100 mM putrescine. With a further increase in polyamines concentration the effect of aggregation acceleration decreased, thus, the modulation of the aggregation rate by polyamines was shown. A comparison of the aggregation kinetics and hydrodynamic radii growth data registered by dynamic light scattering with the data obtained by asymmetric flow field-flow fractionation and analytical ultracentrifugation allowed us to describe the early stages of aggregation and formation of initial α-lactalbumin clusters. Our results provide a deeper insight into the mechanism of amorphous aggregation of α-lactalbumin and polyamines action on protein aggregation and protein-protein interaction in general.