Alaa Adawy

Slight modification of the molten salt synthesis of poly(triazine imide) (PTI) with introduction of copper (I) chloride yielded a novel copper modified material. Energy‐dispersive x‐ray spectroscopy together with electron microscopy confirmed homogenous distribution of the copper within PTI lattice. X‐ray photoelectron spectroscopy suggests the copper to coordinate randomly at bridging nitrogen atoms. Thus obtained material exhibited excellent sensitivity to nitrite anions together with low limits of detection. Under previously optimized experimental conditions and pH 4 of supporting electrolyte, differential pulse voltammetric detection method showed linear response in wide range from 5 to 2200 μM with detection limit of 1.3 μM. Practical applicability for the developed method was scrutinized in wastewater and pipe water samples. Developed method of metal ion intercalation open doors to widespread introduction of metal ions in the PTI structure for practical utilization.

Many structures in nature look symmetric, but this is not completely accurate, because absolute symmetry is close to death. Chirality (handedness) is one form of living asymmetry. Chirality has been extensively investigated at different levels. Many rules were coined in attempts made for many decades to have control over the selection of handedness that seems to easily occur in nature. It is certain that if good control is realized on chirality, the roads will be ultimately open towards numerous developments in pharmaceutical, technological, and industrial applications. This tutorial review presents a report on chirality from single molecules to supramolecular assemblies. The realized functions are still in their infancy and have been scarcely converted into actual applications. This review provides an overview for starters in the chirality field of research on concepts, common methodologies, and outstanding accomplishments. It starts with an introductory section on the definitions and classifications of chirality at the different levels of molecular complexity, followed by highlighting the importance of chirality in biological systems and the different means of realizing chirality and its inversion in solid and solution-based systems at molecular and supramolecular levels. Chirality-relevant important findings and (bio-)technological applications are also reported accordingly.

Biomaterials and their surfaces regulate the biological response and ultimately the quality of healing at a possible site of implantation. The physical, chemical and topographical properties of implants' surfaces play a decisive role in the biological integration process for their immediate loading and long-term success. Since at this level of biological interaction nano-dimensionality is basically entailed, bio-functional nanostructured composites either as filling/cement or coating to metallic implants are required. This study shows the possibility of synthesizing two phases of nanostructured titanium phosphate (π and ρ polymorphs) and enriching them with silver nanoparticles and strontium. More importantly, Ag-Sr-enriched nanostructured π‑titanium phosphate is induced to grow on a commercially available titanium alloy (Ti-6Al-4V), widely used in orthopedic and dental implants, under highly controlled conditions. Structural and microscopic studies, using XRD, HRTEM and SEM altogether confirm the resultant phases and their enrichment with strontium and silver nanoparticles with an average particle size around 6 nm. Using confocal laser scanning microscopy, the surface roughness was measured and is found to lay at the interface between the nanosized and microsized topologies. Ion release assessments showed that the presence of strontium controlled the release rate of silver ions and this could be beneficial in terms of decreasing the accompanied cytotoxicity that is usually encountered at high concentrations of silver release. Antimicrobial and cell proliferation assays have proved that enriching titanium phosphate with strontium and silver nanoparticles has improved their antimicrobial properties, while the cytotoxicity could be controlled.

Metal phosphates represent an important group of materials with established industrial applications that are still attracting special scientific interest, owing to their outstanding physical and chemical properties. In this review, we account on the different synthetic routes and applications of zirconium and titanium phosphates, with a special focus on their application in the medicinal field. While zirconium phosphate has been extensively studied and explored with several reported industrial and medicinal applications, especially for drug delivery applications, titanium phosphates have not yet attracted the deserved attention regarding their established applications. However, titanium phosphates have been the focus of several structural studies with their different polymorphic forms, varied chemical structures, and morphologies. These variations introduce titanium phosphates as a strong candidate for technological and, particularly, biomedical applications.

In this work, an unprecedented study exploring the role that slight changes into the Pd/Au proportion have in the electrocatalytic activity of bimetallic Pd-AuNPs toward the oxygen reduction reaction (ORR) is conducted. In particular, a careful control of the amount of Au atoms introduced in the cluster and the evaluation of the optimum Pd:Au ratio for getting the maximum catalytic activity is performed for the first time. First, PdNPs are synthesized by alcohol reduction in the presence of polyvinylpyrrolidone, and gold atoms are selectively introduced on vertex or corner positions of the cluster in different amounts following a galvanic substitution procedure. Average elemental analysis done relying on EDX spectroscopy allows to evaluate the Pd:Au ratio in the Pd-AuNPs obtained. Lineal sweep voltammetry and chronoamperometry are used for the evaluation of the Pd-AuNPs electrocatalytic activity toward ORR at a neutral pH compared to PdNPs and AuNPs alone. Our results indicate that, the synergy between both metals is strongly enhanced when the amount of gold is controlled and occupies the more reactive positions of the cluster, reaching a maximum activity for the NPs containing a 30% of gold, while an excess of this metal leads to a decrease in such activity, as a shelter of the PdNPs is achieved. Chronoamperometric analysis allows the quantification of the optimal Pd-AuNPs at over 6 × 109 NPs/mL levels. Such optimal Pd-AuNPs were used as tags, taking advantage of the bio-functionalities of gold present in the cluster, in a proof-of-concept electrochemical immunosensor for the detection of hyaluronidase wound infection biomarker, using magnetic beads as platforms. Hyaluronidase was detected at levels as low as 50 ng/mL (0.02 U/mL; 437 U/mg) with good reproducibility (RSD below 8%) and selectivity (evaluated against bovine serum albumin, immunoglobulin G and lysozyme). The low matrix effects inherent to the use of magnetic bead platforms allowed us to discriminate between wound exudates with both sterile and infected ulcers without sample pre-treatment. This novel electrocatalytic immunoassay has the advantage, over common methods for NP tags electrochemical detection, of the signal generation in the same neutral medium where the immunoassay takes place (10 mM PBS pH 7.4), avoiding the use of additional and hazardous reagents, bringing it closer to their use as point-of-care devices. Overall, our findings may be of great interest not only for biosensing, but also for applications such as energy converting on fuel cells, in which the ORR has a pivotal role.

There is an increasing demand on synthesizing pharmaceuticals and biomaterials that possess antimicrobial and/or antiviral activities. In this respective silver nanoparticles are known for their excellent antimicrobial activity. Nevertheless, their uncontrolled release in a biological medium can induce a cytotoxic effect. For this, we explored the use of nanolayered metal phosphates based on titanium and zirconium as materials that can be enriched with silver nanoparticles. Employing the hydrothermal route, crystalline α-phases of zirconium and titanium phosphates (α-ZrP, α-TiP) were synthesized and there after surface-enriched with silver nanoparticles. The structural assessment confirmed the stability of the structures and their sizes are in the nanoscale at least in one dimension. The cytocompatibility assays confirmed the biocompatibility of the pristine phases and the antimicrobial assay confirmed that both silver-enriched nanolayered structures maintain an antibacterial effect...

The aim of this study was to investigate the efficiency of removing Cr6+ from aqueous solutions using two exfoliated vermiculite: (1) heated abruptly at 1000 °C and (2) irradiated with microwave radiation. The effects investigated were contact time, adsorbate concentration and initial Cr6+ concentration. The adsorption with both exfoliated vermiculites was well described by the DKR isotherm, indicative of a cooperative process and with the pseudo second order kinetic model. The Kd value for the two exfoliated vermiculites was similar, 0.2 ·1010 μg/Kg. The maximum adsorption capacity of Cr6+ with thermo-exfoliated vermiculite, 2.81 mol/g, was much higher than with microwave irradiated vermiculite, 0.001 mol/g; both values were obtained with 0.5 g of vermiculite in contact with distilled water enriched with 1 ppm of Cr6+ for 24 h. Factors such as ion chemistry, the solution pH and ionic strength, influence the values of capacity, adsorption energy and initial adsorption rate values of...

Many structures in nature look symmetric, but this is not completely accurate, because absolute symmetry is close to death. Chirality (handedness) is one form of living asymmetry. Chirality has been extensively investigated at different levels. Many rules were coined in attempts made for many decades to have control over the selection of handedness that seems to easily occur in nature. It is certain that if good control is realized on chirality, the roads will be ultimately open towards numerous developments in pharmaceutical, technological, and industrial applications. This tutorial review presents a report on chirality from single molecules to supramolecular assemblies. The realized functions are still in their infancy and have been scarcely converted into actual applications. This review provides an overview for starters in the chirality field of research on concepts, common methodologies, and outstanding accomplishments. It starts with an introductory section on the definitions ...

Chert samples from different coastal and inland outcrops in the Eastern Asturias (Spain) were mineralogically investigated for the first time for archaeological purposes. X-ray diffraction, X-ray fluorescence, transmission electron microscopy, infrared and Raman spectroscopy and total organic carbon techniques were used. The low content of moganite, since its detection by X-ray diffraction is practically imperceptible, and the crystallite size (over 1000 A) of the quartz in these cherts would be indicative of its maturity and could potentially be used for dating chert-tools recovered from archaeological sites. Also, this information can constitute essential data to differentiate the cherts and compare them with those used in archaeological tools. However, neither composition nor crystallite size would allow distinguishing between coastal and inland chert outcrops belonging to the same geological formations.

Two commercial vermiculites from China and Libby were treated with different alcohols (methanol, ethanol, propanol and butanol) at room temperature for up to one month and afterwards irradiated with microwaves. The exfoliated and non-exfoliated particles were characterized by X-ray diffraction, high-resolution transmission microscopy, thermal gravimetric analyses and infrared spectroscopy to explain the inconsistencies in relation to potassium distribution and the exfoliation observed in previous investigations. The percentages of the exfoliated and non-exfoliated particles of the investigated vermiculites greatly varied, with no indication of a relationship between the resultant exfoliation and alcohol treatment. The crystallinity and structural order of the phases composing the particles are independent of the success of their exfoliation. The existence of a mosaic structure, the intra-particle mosaic-like intergrowth of the different mineral phases, in the treated and pristine co...

Surface properties of the nanostructured materials are essential in attaining particular functionality, which is why there are a plethora of surface modification methods applied during or past the synthesis of nanoparticular substrates. Depending on the resulting content of the surface it could be heterophase forming modifications or pristine titania modifications. In this communication, we study a novel approach to pristine titania surface alteration by controlled chemisorption of the stable water-soluble titanium complex on the nanocrystalline anatase. Following on-air calcination for removal of organic residues converts chemisorbed complexes into oxide phase increments. Such an approach retains crystallinity and specific surface with simultaneous withdrawal of surface hydroxyl groups.

ABSTRACT The incorporation of impurities during protein crystallization is one of the main obstacles that prevent the growth of high quality crystals. Mass transport has been shown to affect the incorporation of impurities. Here we used a special growth configuration which enables the simultaneous investigation of the two main means of mass transport: of hen egg-white lysozyme were crystallized using this configuration in the presence of different types of impurities at various degrees of contamination. We found that even in the presence of impurities which are not easily segregated, the diffraction quality of crystals grown under diffusion-limited conditions is better than that of those grown in the presence of natural convection. The results also reveal a significant difference in impurity uptake for the different polymorphic forms of the same protein. The combined results show that, also in the presence of large fractions of impurities, the more perfect crystals grow when the rate of accretion of molecules is slow and orderly, as accomplished under diffusion-limited conditions. diffusion and convection, under otherwise identical conditions. Two polymorphic forms

The relationship between textural parameters (specific superficial area (SBET) and porosity (Vp)) of lamellar products obtained from HNO3-activated vermiculites and their iron and water content has been established. Two commercial vermiculites, one thermoexfoliated commercial vermiculite, and one pure vermiculite were nitric-acid-treated at 4 and 8 M concentrations for 1, 3, and 7 days. Untreated and treated samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and N2 physisorption analysis. The untreated vermiculites showed a direct relationship between their iron content and the values of SBET, Vp, and pore size; an inverse relationship was observed in the case of the treated samples. The iron content may prevent further leaching of cations but not water loss, therefore forming lamellar products with lower SBET and Vp values. The SBET and Vp values of the studied thermoexfoliated sampl...

Malaria remains a major threat to human health, as strains resistant to current therapeutics are discovered. Efforts in finding new drug targets are hampered by the lack of sufficiently specific tools to provide target validation prior to initiating expensive drug discovery projects. Thus, new approaches that can rapidly enable drug target validation are of significant interest. In this manuscript we present the crystal structure of malate dehydrogenase from Plasmodium falciparum (PfMDH) at 2.4 Å resolution and structure-based mutagenic experiments interfering with the inter-oligomeric interactions of the enzyme. We report decreased thermal stability, significantly decreased specific activity and kinetic parameters of PfMDH mutants upon mutagenic disruption of either oligomeric interface. In contrast, stabilization of one of the interfaces resulted in increased thermal stability, increased substrate/cofactor affinity and hyperactivity of the enzyme towards malate production at sub-m...

Peroxisomes are a major cellular compartment of eukaryotic cells, and are involved in a variety of metabolic functions and pathways according to species, cell type and environmental conditions. Their biogenesis relies on conserved genes known as PEX genes that encode peroxin proteins. Peroxisomal membrane proteins and peroxisomal matrix proteins are generated in the cytosol and are subsequently imported into the peroxisome post-translationally. Matrix proteins containing a peroxisomal targeting signal type 1 (PTS1) are recognized by the cycling receptor Pex5p and transported to the peroxisomal lumen. Pex5p docking, release of the cargo into the lumen and recycling involve a number of peroxins, but a key player is the Pex4p-Pex22p complex described in this manuscript. Pex4p from the yeast Saccharomyces cerevisiae is a ubiquitin-conjugating enzyme that is anchored on the cytosolic side of the peroxisomal membrane through its binding partner Pex22p, which acts as both a docking site an...

Refolding of proteins derived from inclusion bodies is very promising as it can provide a reliable source of target proteins of high purity. However, inclusion body-based protein production is often limited by the lack of techniques for the detection of correctly refolded protein. Thus, the selection of the refolding conditions is mostly achieved using trial and error approaches and is thus a time-consuming process. In this study, we use the latest developments in the differential scanning fluorimetry guided refolding approach as an analytical method to detect correctly refolded protein. We describe a systematic buffer screen that contains a 96-well primary pH-refolding screen in conjunction with a secondary additive screen. Our research demonstrates that this approach could be applied for determining refolding conditions for several proteins. In addition, it revealed which "helper" molecules, such as arginine and additives are essential. Four different proteins: HA-RBD, M...

The possibility of using sub-micrometer polymeric stomatocytes is investigated to effectuate confined crystallization of inorganic compounds. These bowl-shaped polymeric compartments facilitate confined crystallization while their glassy surfaces provide their crystalline cargos with convenient shielding from the electron beam's harsh effects during transmission electron microscopy experiments. Stomatocytes host the growth of a single nanocrystal per nanocavity, and the electron diffraction experiments reveal that their glassy membranes do not interfere with the diffraction patterns obtained from their crystalline cargos. Therefore, it is expected that the encapsulation and crystallization within these compartments can be considered as a promising template (nanovials) that hold and protect nanocrystals and protein clusters from the direct radiation damage before data acquisition, while they are examined by modern crystallography methodologies such as serial femtosecond crystallo...

The most serious obstacle in the route of macromolecules' structure determination is the difficulty of growing high-­‐quality crystals, which diffract X-­‐rays to high resolution limits. Protein crystallization is a multi-­‐parametric process which is influenced by many biochemical and physicochemical parameters. Among these parameters, mass transport has heavily attracted the attention of researchers involved in protein crystallization. The control of this parameter has been shown to have the highest impact on increasing the final quality and thus the diffractivity of protein crystals. In order to control the mass transport, we have developed the ceiling crystallization method[1-­‐2], wherein the protein crystal growth is solely diffusion-­‐limited. These convection-­‐free surroundings of ceiling crystals were monitored by phase shifting interferometry measurements and validated theoretically by numerical simulations. In addition, the visual inspection of the ceiling crystals m...

ABSTRACT The incorporation of impurities during protein crystallization is one of the main obstacles that prevent the growth of high quality crystals. Mass transport has been shown to affect the incorporation of impurities. Here we used a special growth configuration which enables the simultaneous investigation of the two main means of mass transport: of hen egg-white lysozyme were crystallized using this configuration in the presence of different types of impurities at various degrees of contamination. We found that even in the presence of impurities which are not easily segregated, the diffraction quality of crystals grown under diffusion-limited conditions is better than that of those grown in the presence of natural convection. The results also reveal a significant difference in impurity uptake for the different polymorphic forms of the same protein. The combined results show that, also in the presence of large fractions of impurities, the more perfect crystals grow when the rate of accretion of molecules is slow and orderly, as accomplished under diffusion-limited conditions. diffusion and convection, under otherwise identical conditions. Two polymorphic forms

ABSTRACT The incorporation of impurities during protein crystallization is one of the main obstacles that prevent the growth of high quality crystals. Mass transport has been shown to affect the incorporation of impurities. Here we used a special growth configuration which enables the simultaneous investigation of the two main means of mass transport: of hen egg-white lysozyme were crystallized using this configuration in the presence of different types of impurities at various degrees of contamination. We found that even in the presence of impurities which are not easily segregated, the diffraction quality of crystals grown under diffusion-limited conditions is better than that of those grown in the presence of natural convection. The results also reveal a significant difference in impurity uptake for the different polymorphic forms of the same protein. The combined results show that, also in the presence of large fractions of impurities, the more perfect crystals grow when the rate of accretion of molecules is slow and orderly, as accomplished under diffusion-limited conditions. diffusion and convection, under otherwise identical conditions. Two polymorphic forms

Macromolecular crystallography is the most direct and accurate approach to determine the three-dimensional structure of biological macromolecules. The growth of high quality single crystals, yielding diffraction to the highest X-ray resolution, remains a bottleneck in this methodology. Many methods have been developed to achieve convection-free crystal growth. Unfortunately, they are either very expensive or methodologically demanding. Recently, we showed that diffusion-limited crystal growth can be effectuated in a rather cheap, simple and easily applicable method. Using this “ceiling crystallization method”, an entirely convection-free crystallization environment is achieved, which enhances the purity and crystallinity of protein crystals. The effectiveness of the ceiling method was validated by visual inspection of the morphology of the ceiling crystals as well as by diffraction experiments. We achieved record X-ray resolution for a number of proteins. In addition, the convection...

Macromolecular crystallography is the most direct and accurate approach to determine the three-dimensional functional structure of biological macromolecules. The growth of high quality single crystals, yielding the highest X-ray resolution, remains a bottleneck in this methodology. Gravity-driven convection is hold responsible for interfering with the growth of perfect crystals in all terrestrial methods, while space microgravity provides diffusive mass transport which can improve the quality of protein crystals. Here we show that through an efficient modification of the batch crystallization method, an entirely convection-free crystallization environment is achieved, which enhances the purity and crystallinity of protein crystals. In this novel method, dubbed “Ceiling Crystallization Method”, we exploit gravity to achieve diffusion-limited crystal growth in a terrestrial setting instead of eliminating it. Protein crystals grow at the “ceiling” of a growth-cell experience the same e...