Crystalline Aggregates Research Articles

Artificial Water Channels—Progress Innovations and Prospects

Artificial Water Channels—Progress Innovations and Prospects

Nanofiber Concrete: Multi-Level Reinforcement

Concrete is the most commonly used building material worldwide. One of its main disadvantages is the fragility of fracture and low crack resistance. The use of dispersed reinforcement of concrete composites is a promising direction in solving this type of problem. Dispersed fibers, evenly distributed over the entire volume of the material, create a spatial frame and contribute to the inhibition of developing cracks under the action of destructive forces. In order to increase the fracture toughness of concrete, dispersed fiber reinforcement is increasingly used in practice. The beginning of crack nucleation occurs at the nanoscale in the cement matrix. Thus, the use of nano-reinforcement with dispersed nanofibers can have a positive effect on the crack resistance of the cement composite. It is proposed to consider carbon nanotubes as such nanofibers. The presence of carbon nanofibers changes the microstructure and nanostructure of cement modified with carbon nanotubes. The result of the processes occurring in capillaries and cracks are deformations in the intergranular matrix, the free flow of which is prevented by rigid clinker grains and nanocarbon tubes, which creates a certain stress intensity at the tips of the separation cracks. The working hypothesis is confirmed that the required fracture toughness of structural concrete is provided by multi-level reinforcement: at the level of the crystalline aggregate of cement stone – carbon nanotubes, and at the level of fine-grained concrete – various macro-sized fibers (steel, polymer). Reinforcement of a crystalline joint with carbon nanotubes leads to an increase in the fracture toughness of the matrix (cement stone) by 20 %, compressive strength by 12 %, and tensile strength in bending by 20 %. When reinforcing at the level of fine-grained concrete, we obtain a composite – nanofibre-reinforced concrete with fracture toughness.

Biominerals in the Cacteae tribe: Chemical-morphological characterization, distribution and systematic perspectives

• The occurrence of silica bodies in the hypodermis of cacti are diagnostic for all the species of Echinocactus , and the exclusion of E. grusonii of this genus is supported by the lack of silica bodies as well as the occurrence of calcium oxalate druses. • Six biomineral habits were found in the Cacteae species studies, being spherulites and prisms the most common. • Extracellular sandstones occur in six species of Mammillaria , commonly in the outer periclinal wall of the epidermis. • For the first time the structure of the biominerals of seven genera ( Cumarinia, Echinomastus, Escobaria, Obregonia, Sclerocactus , Stenocactus) of Cacteae are characterized. Biominerals precipitate by biological activity and are found in various organisms. In the Cactaceae family, biominerals have been described for numerous genera and species and their contribution to systematics has recently been demonstrated. The aims of this study are to characterize the biominerals in the stem of members of Cacteae by describing their shape, position and mineral composition. Twenty-eight genera and 149 species of Cacteae were studied by bright-field and polarized microscopy. The composition of biominerals was analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy in 34 species representing the Cacteae clades. The biominerals of seven genera out of 28 are described for the first time. Only six species of Mammillaria have extracellular biominerals. Sixteen genera and 91 species possess intracellular biominerals in hypodermis, where species of Echinocactus and Ferocactus showed silica bodies. Spherulites, prisms and druses are present in 28 genera, and are distributed in the cortex of 141 species and in the pith of 94 species. Statistical analysis revealed differences between genera for the maximum length of biominerals in the hypodermis and cortex. Notably, Kadenicarpus possesses the smallest biominerals in the cortex and pith (< 35 µm in mean) and the largest mean in the pith for Astrophytum (212 µm). In the Cacteae, calcium oxalates were the most predominant biominerals. Other elements such as magnesium, manganese, and aluminum were also identified. Lophophora is characterized by crystalline aggregates in the cortex of both species with calcium oxalate and traces of silicon and iron, which are not found in other crystalline aggregates of other taxa. We detected a unique combination of biominerals that allowed for us to distinguish the species of some genera, such as Astrophytum and Echinocactus . In conclusion, the occurrence, structure and size of biominerals provide valuable information for systematics at the generic level in Cacteae.

Building hybrid luminescent materials: Understanding stacking modes in aggregate structure to emission modulation

Two charge transfer (CT) complexes A1 and A2 with tunable emissions were explored by diluting anthracene functionalized stilbene as donors with 1,2,4,5-tetracyanobenzene (TCNB) as the acceptor unit. The effect of substituent tailoring on the supramolecular packing and optical properties of the two CT products was accomplished by various solid-state characterization and theoretical calculations. It was found that these binary CT cocrystals exhibit two types of alternatively sandwiched face-to-face patterns (A1 (DADA), A2 (DAD··DAD), and red-shifted emissions relative to their monomers through π-π interactions accompanied by hydrogen bonds as indicated by the structural analysis. The two crystalline aggregates feature molar ratios of 1:1 or 1:2 and molecular packing-dependent emissions, induced by different dihedral angles attributed to the substituent effect, thereby leading to diverse π-π interactions and charge transfer effects respectively, which further results in tunable photophysical properties. These results suggest that the marriage of substituent engineering and cocrystal engineering is a promising molecular design strategy that will help to understand the relationship between emission property and molecular packing with the aim to guide further the development of novel organic solid luminescent materials.

Turn-on fluorescence of davydov-split aggregate particles for protein detection

The turn-on fluorescence of supramolecular aggregates of organic dyes through the interaction with specific proteins is highly desirable for the development of a high signal-to-noise fluorescence probe for biomedical applications. In this paper, we use the self-assembly of 3,3′-ditetradecyloxacarbocyanine (DiOC14(3)) in the methanol/water mixture with/without NaOH to form Davydov-split aggregate particles. We show that the crystalline Davydov-split aggregate particles formed in the presence of NaOH failed to respond to bovine serum albumin (BSA). While the non-crystalline Davydov-split aggregate particles formed in the absence of NaOH gradually disassembled through the interaction with BSA. The disassembled DiOC14(3) molecules complex with BSA in the monomer and twisted H-dimer forms, consequently turning on fluorescence. The turn-on fluorescence is highly specific to BSA and linearly increases with the increase of BSA concentrations. Furthermore, we show that the turn-on fluorescence behavior of non-crystalline Davydov-split aggregate particles by BSA can also be achieved in synthetic urine, which highlights their potential for the detection of urinary albumin.

Combination of Lanosterol and Nilvadipine Nanosuspensions Rescues Lens Opacification in Selenite-Induced Cataractic Rats.

It has recently been reported that lanosterol (LAN) plays a preventive role against lens opacification through the reversal of crystalline aggregation. However, the effect of LAN is not sufficient to restore lens transparency. In this study, we designed ophthalmic nanosuspensions (LAN-ONSs and NIL-ONSs) based on LAN and nilvadipine (NIL), which can counteract cataract-related factors (e.g., enhanced Ca2+ and calpain levels), and investigated whether the combination of LAN-ONSs and NIL-ONSs can restore the nuclear lens opacity in sodium-selenite-induced cataractic rats (cataractic rats). The mean particle sizes of the LAN-ONSs and NIL-ONSs were 108.8 nm and 89.0 nm, respectively. The instillation of the LAN-ONSs or NIL-ONSs successfully delivered the drugs (LAN or NIL) into the lenses of the rats, although the instillation of LAN-ONSs or NIL-ONSs alone did not increase lens transparency in the cataractic rats. On the other hand, the cataract-related factors (enhanced Ca2+ and calpain levels) were significantly alleviated by the combination of LAN-ONSs and NIL-ONSs; furthermore, the perinuclear refractile ring in the lens nucleus and enhanced number of swollen fibers were attenuated by the LAN-ONS and NIL-ONS combination. Moreover, the opacity levels in the cataractic rats were reduced after treatment with the combination of LAN-ONSs and NIL-ONSs. It is possible that the combination of LAN and NIL will be useful for the treatment of lens opacification in the future.

On the provenance of GEMS, a quarter century post discovery

The provenance of GEMS (glass with embedded metal and sulfides) in cometary type interplanetary dust particles is investigated using analytical scanning transmission electron microscopy and secondary ion mass spectrometry. We review the current state of knowledge and closely examine the densities, elemental compositions and distributions, iron oxidation states, and isotopic compositions of a subset of GEMS in chondritic porous interplanetary dust. We find that GEMS are underdense with estimated densities that are 35–65% of compositionally equivalent crystalline aggregates. GEMS low densities result in a lower contribution to the bulk compositions of IDPs than has been assumed based on their volume fraction. We also find that element/Si ratios, assumed to be primary (indigenous), are instead perturbed by contamination and secondary alteration, including pulse heating during atmospheric entry. Fe in pyrrhotite inclusions was oxidized and Mg, S, Ca, and Fe were depleted relative to lithophile Al and Si, resulting in reduction in element/Si ratios. Because they trap outgassing elements, Fe-rich oxide rims that formed on the surface of GEMS are serendipitous “witness plates” to the changes in composition that accompany atmospheric entry. As a result of alteration, GEMS elemental compositions cannot reliably inform about their provenance. Except for highly anomalous oxygen isotope ratios measured in some large GEMS grains that indicate a contribution from circumstellar dust, oxygen isotope compositions are generally poor indicators of provenance. Prior work indicates that most GEMS fall close to the terrestrial oxygen isotope composition, which, however, does not exclude a presolar interstellar origin. Nitrogen isotopic compositions are more diagnostic. Elevated 15N/14N ratios indicate that GEMS accreted in conjunction with formation of organic matter by ion–molecule reactions in a cold (<50 K) presolar environment like the extreme outer nebula or interstellar medium. Considering all observations, we conclude that GEMS are most likely processed interstellar silicates.

Origin of Nonmonotonical Variation of Luminescence Efficiency under Pressure in Organic Molecule.

The nonmonotonical variation of luminescence efficiency under extra pressure occurs frequently in organic molecules; however, the mechanism behind this is still elusive. Using a theoretical protocol combining thermal vibration function rate formalism coupled quantum mechanics/molecular mechanics models, we explored the relationship between extra pressure, molecular packing, and fluorescent quantum efficiency (FQE) of the representative 1,2,3,4-tetraphenyl-1,3-cyclopentadiene (TPC). It is found that the first increase and then decrease of FQE in TPC crystalline aggregates upon pressurization is cooperatively attributed to the continuous reduction of the radiative decay rate constant and nonmonotonical change of the nonradiative decay rate constant (kic). The initial decrease of kic originates from the effective suppression of electron-vibration coupling and the Duschinsky rotation effect by extra pressure, whereas the following increase of kic comes from the surge of nonadiabatic electronic coupling and the reduction of adiabatic excitation energy upon further compression. This study can provide a theoretical basis for the rational design and performance control of the piezochromic luminescent materials.

A native chemical chaperone in the human eye lens.

Cataract is one of the most prevalent protein aggregation disorders and still the most common cause of vision loss worldwide. The metabolically quiescent core region of the human lens lacks cellular or protein turnover; it has therefore evolved remarkable mechanisms to resist light-scattering protein aggregation for a lifetime. We now report that one such mechanism involves an unusually abundant lens metabolite, myo-inositol, suppressing aggregation of lens crystallins. We quantified aggregation suppression using our previously well-characterized in vitro aggregation assays of oxidation-mimicking human γD-crystallin variants and investigated myo-inositol's molecular mechanism of action using solution NMR, negative-stain TEM, differential scanning fluorometry, thermal scanning Raman spectroscopy, turbidimetry in redox buffers, and free thiol quantitation. Unlike many known chemical chaperones, myo-inositol's primary target was not the native, unfolded, or final aggregated states of the protein; rather, we propose that it was the rate-limiting bimolecular step on the aggregation pathway. Given recent metabolomic evidence that it is severely depleted in human cataractous lenses compared to age-matched controls, we suggest that maintaining or restoring healthy levels of myo-inositol in the lens may be a simple, safe, and globally accessible strategy to prevent or delay lens opacification due to age-onset cataract.

Inside Front Cover: Heating‐induced aggregation control for efficient sequential‐cast organic solar cells

In this work, Wang and coauthors demonstrated a heating induced aggregation strategy to manipulate the aggregation behavior of non-fullerene acceptors (NFAs) during the sequential-casting process, with the large crystalline aggregates of NFAs effectively suppressed to allow diffusion to form pseudo-bulk heterojunction OSCs with efficient exciton dissociation and charge transport characteristics, consequently receiving significantly enhanced device efficiency.

Crystal Structure and Twisted Aggregates of Oxcarbazepine Form III.

Polymorphism and crystal habit play vital roles in dictating the properties of crystalline materials. Here, the structure and properties of oxcarbazepine (OXCBZ) form III are reported along with the occurrence of twisted crystalline aggregates of this metastable polymorph. OXCBZ III can be produced by crystallization from the vapor phase and by recrystallization from solution. The crystallization process used to obtain OXCBZ III is found to affect the pitch, with the most prominent effect observed from the sublimation-grown OXCBZ III material where the pitch increases as the length of aggregates increases. Sublimation-grown OXCBZ III follows an unconventional mechanism of formation with condensed droplet formation and coalescence preceding nucleation and growth of aggregates. A crystal structure determination of OXCBZ III from powder X-ray diffraction methods, assisted by crystal structure prediction (CSP), reveals that OXCBZ III, similar to carbamazepine form II, contains void channels in its structure with the channels, aligned along the c crystallographic axis, oriented parallel to the twist axis of the aggregates. The likely role of structural misalignment at the lattice or nanoscale is explored by considering the role of molecular and closely related structural impurities informed by crystal structure prediction.

Mixed-dust pneumoconiosis in a dental technician: a multidisciplinary diagnosis case report

BackgroundIn dental laboratories, exposure to crystalline silica can occur during procedures that generate suspended mineral dusts, e.g. dispersion of mixing powders, removal of castings from molds grinding, polishing of castings and porcelain, and use of silica sand for blasting. There is also a large list of toxic agents (acrylic resins, polymeric materials, etc.) used to produce removable and fixed prostheses, but also impression materials and more. Using personal protective equipment and other aids reduces the exposure to these potentially harmful agents.Case presentationWe report the case of a 42-year-old male dental technician who began to suffer from a dry cough and exertional dyspnea after approximately 15 years of work. The operations he conducted for his job resulted in the generation of crystalline silica, aluminum, chromium and titanium dust. The worker did not regularly wear personal protective equipment and some of the above operations were not carried out in closed circuit systems. The Chest X-ray showed diffused micronodules in the pulmonary interstitium of the upper-middle lobes, bilaterally, and a modest left basal pleural effusion. Simple spirometry showed small airway obstruction in its initial stage. High Resolution Computerized Tomography of the chest showed bilateral micronodulation of a miliariform type, with greater profusion to the upper lobes, also present in the visceral pleura, bilaterally. Histological examination showed aggregates of pigment-laden macrophages forming perivascular macules or arranged in a radial pattern around a core of sclerohyalinosis. Scanning Electron Microscopy and Energy Dispersive Spectrometry revealed several mineral particles, typically characterized by the presence of crystalline silica and metal aggregates. The environmental concentrations of total dust and its respirable fraction were all lower than the relative TLV-TWA—ACGIH, yet not negligible.ConclusionsThe above findings and a multidisciplinary assessment led to the diagnosis of mixed dust pneumoconiosis s/q with 2/2 profusion of occupational origin. This diagnosis in a dental technician was supported for the first time in literature by environmental exposure analysis.

Deamidation of the human eye lens protein γS-crystallin accelerates oxidative aging

Cataract, a clouding of the eye lens from protein precipitation, affects millions of people every year. The lens proteins, the crystallins, show extensive post-translational modifications (PTMs) in cataractous lenses. The most common PTMs, deamidation and oxidation, promote crystallin aggregation; however, it is not clear precisely how these PTMs contribute to crystallin insolubilization. Here, we report six crystal structures of the lens protein γS-crystallin (γS): one of the wild-type and five of deamidated γS variants, from three to nine deamidation sites, after sample aging. The deamidation mutations do not change the overall fold of γS; however, increasing deamidation leads to accelerated disulfide-bond formation. Addition of deamidated sites progressively destabilized protein structure, and the deamidated variants display an increased propensity for aggregation. These results suggest that the deamidated variants are useful as models for accelerated aging; the structural changes observed provide support for redox activity of γS-crystallin in the lens.

Thermodynamic properties of temozolomide in crystalline and gaseous aggregate states

Temozolomide (4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo[4,3,0]nona-2,7,9-triene-9-carboxamide) is an active component of antitumor immunosuppressive alkylating drugs, and it used largely for the treatment of various types of malignant tumors, including malignant gliomas that are difficult to treat by surgery (glioblastoma multiforme and anaplastic astrocytoma). Wide field of temozolomide application dictates the need for its comprehensive thermodynamic study. In this work temperature dependance of the temozolomide heat capacity was obtained using the adiabatic calorimetry method and the standard thermodynamic functions of crystalline temozolomide were calculated in the temperature range 80–370 K. Standard thermodynamic functions of the temozolomide in the ideal gas state were calculated using the statistical thermodynamics approach in the temperature range 0–1000 K. To obtain the standard internal energy and enthalpies of combustion and formation of crystalline temozolomide at T = 298.15 K the combustion bomb calorimetry was used. Standard enthalpy of formation of the gaseous temozolomide was calculated in the framework of the isodesmic reactions method using quantum chemical computing. To calculate standard sublimation enthalpy of temozolomide the electrostatic potential model was applied. The results obtained can find application in solving problems of optimisation of temozolomide production processes and to validate experimentally obtained values of thermodynamic properties of the temozolomide.

Insights into the binding of morin to human γD-crystallin.

Crystallin aggregation in the eye lens is one of the leading causes of cataract formation. The increase in the human γD-crystallin (HγDC) aggregation propensity has been associated with the oligomerization of its partially folded and fully unfolded structure. A recent study demonstrated that the binding of flavonoid morin (MOR) to HγDC inhibits the fibrillation of this protein. In this work, we carry out an exhaustive search for the possible binding site of MOR on HγDC by combining an ensemble docking approach with the Wrap 'N' Shake protocol. In agreement with previous results, we found a potential MOR-binding site in the cleft formed between the N-terminal and C-terminal domains of HγDC. MOR preference for the cleft residues was observed even with the interface-opened intermediate conformers of HγDC. In addition, metadynamics simulations were carried out to corroborate the stabilizing activity of MOR on HγDC structure and to identify the structural regions implicated during the unfolding inhibition. Overall, this study provides relevant insights into the identification of new HγDC aggregation inhibitors.

Vibronic States and Edge-On Oriented π-Stacking in Poly(3-alkylthiophene) Thin Films

The influence of alkyl side-chain length [CnH2n+1 (A), where n = 6 (hexyl), 8 (octyl), 12 (dodecyl)] and thermal annealing (TA) and the definite roles of these in the quantity and quality of π-stacked crystallinity and edge-on orientated (EO) ordering of spin-coated poly(3-alkylthiophene) [P3AT] thin films, which are of massive significance in their optoelectronic properties, were investigated using complementary optical absorption spectroscopy and X-ray reflectivity (XR) techniques. The energy-band diagram, corresponding to the vibronic levels, obtained from the optical absorption spectrum provides information about the percentage, planarity, local order, and average conjugation length of the crystalline aggregates, while the electron density profile obtained from the XR provides unique information about the EO ordering and its variation along the depth. A prominent EO ordering near the substrate with a gradually decreased ordering toward the top surface is observed in each film. An as-cast P3HT film of shorter side-chain (having a natural nucleation tendency and rigidity) shows a slightly higher crystallinity and weaker excitonic coupling, while as-cast P3DDT film (having longer side-chain flexibility) shows a slightly better EO ordering. After the TA, the planarity of the unfolded backbone improves in each film; however, the effect is maximum in the P3DDT film. The EO ordering also improves throughout the film (by a thermal energy-induced reorientation of crystallites) but more toward the top surface (by increasing the decay length), preserving the exponential decay nature. The P3HT film (with the better initial crystallinity and planarity) shows an appreciable improvement, while the P3DDT film (where the crystallinity increases and crystallites have a better reorientational ability) shows the maximum improvement in the EO ordering. The improvement of the crystallinity (in quantity and quality) and the EO ordering of P3AT in thin films (as active layers), especially near the film–substrate interfaces, are of immense importance for their better in-plane charge carrier mobility in a thin-film transistor.

Effect of Sorbitol on Alpha-Crystallin Structure and Function.

Loss of eye lens transparency due to cataract is the leading cause of blindness all over the world. While aggregation of lens crystallins is the most common endpoint in various types of cataracts, chaperone-like activity (CLA) of α-crystallin preventing protein aggregation is considered to be important for maintaining the eye lens transparency. Osmotic stress due to increased accumulation of sorbitol under hyperglycemic conditions is believed to be one of the mechanisms for diabetic cataract. In addition, compromised CLA of α-crystallin in diabetic cataract has been reported. However, the effect of sorbitol on the structure and function of α-crystallin has not been elucidated yet. Hence, in the present exploratory study, we described the effect of varying concentrations of sorbitol on the structure and function of α-crystallin. Alpha-crystallin purified from the rat lens was incubated with varying concentrations of sorbitol in the dark under sterile conditions for up to 5 days. At the end of incubation, structural properties and CLA were evaluated by spectroscopic methods. Interestingly, different concentrations of sorbitol showed contrasting results: at lower concentrations (5 and 50 mM) there was a decrease in CLA and subtle alterations in secondary and tertiary structure but not at higher concentrations (500 mM). Though, these results shed a light on the effect of sorbitol on α-crystallin structure-function, further studies are required to understand the mechanism of the observed effects and their implication to cataractogenesis.

Spectroscopic techniques to evaluate the unfolding and aggregation of the HβB2 crystallin due to the effect of UVB radiation: implications for cataract formation

The aggregation of βγ-crystallins is the main cause of the formation of cataracts. Type B ultraviolet (UVB) radiation is an important risk factor in the formation of cataracts, which is the leading cause of blindness in the world. Human βB2 crystallin (HβB2) is found in high concentrations in the lens and has been associated with the development of cataracts. Taking into consideration that the formation of cataracts is a slow, kinetic process, in which the damage suffered by proteins accumulates little by little, in this work we study the effect of exposure to UVB radiation for short periods time on the unfolding and aggregation of HβB2.

Accelerated oxidative aging in deamidated variants of the human eye lens protein γ(S)-crystallin

Cataract disease causes clouding of the eye lens due to precipitation of lens proteins, known as crystallins. In aged and cataractous lenses, crystallins have been shown to accumulate post-translational modifications (PTMs), with deamidation and oxidation among the most commonly reported PTMs. Both deamidation and oxidation appear to promote crystallin aggregation; however, the relationship between these two modifications and their role in crystallin insolubility is not clear. We determined six novel crystal structures of a major human lens protein, γS-crystallin (γS): one of the wild-type in a monomeric state, and five of deamidated γS variants, ranging from three to nine deamidation sites, after varying degrees of sample aging.

UV-light-driven cadmium sulphide (CdS) nanocatalysts: synthesis, characterization, therapeutic and environmental applications; kinetics and thermodynamic study of photocatalytic degradation of Eosin B and Methyl Green dyes.

Cadmium sulphide (CdS) nanoparticles (NPs) were synthesized through hydrothermal route and characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), Energy dispersive X-ray analysis, Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and Thermo gravimetric analysis (TGA).The band gap of CdS nanoparticles was found to be 2.38 eV. CdS NPs are crystalline aggregates with hexagonal structure as shown by SEM and XRD analysis. TGA study revealed that the synthesized nanomaterials were very stable to temperature and only 6.54% total loss occurred during heating range (25 °C-600 °C).The CdS NPs were used for the first time against the degradation of Eosin B (EB) and Methyl green (MG) dyes in aqueous solution.The degradation of EB and MG over CdS nanocatalysts followed second order kinetics. The predicted activation energies for both the dyes' reactions were 61.1 kJ/mol and 32.11 kJ/mol, respectively. About 95% and 90% dye degradation was observed at the time interval of 160 minutes for EB and MG, respectively. High percent degradation of EB was observed at high pH (pH 0) while at low pH (pH 4) high percent degradation was found for MG dye. Maximum dye degradation was found at the optimal dose (0.03 g/L) of the catalyst and at low dye concentration. The rate of EB and MG dye degradation was found to increase with increase in temperature up to 45 °C. The recyclability study showed that CdS nanoparticles could be reused for the degradation of the given dyes. Good antibacterial activity against Staphylococcus aureus was shown by CdS NPs. From the biocompatibility it was confirmed that CdS NPS are bioincompatible compatible.