Fine tuning of CdxZn1-xS for photo-depolymerization of alkaline lignin into vanillin.

Lignin is abundant and contains a large number of aromatic groups. Herein, CdxZn1-xS photocatalyst with tunable band gap energy was successfully synthesized by using 3-mercaptopropionic acid as a structure tuning additive. CdxZn1-xS can depolymerize alkaline lignin to vanillin by the photocatalytic process. Each gram of alkaline lignin can produce 46.5 mg of vanillin. 2-Phenoxy-1-phenylethanol (PP-ol) and other model compounds were used to understand the depolymerizing process of lignin. Fine tuned CdxZn1-xS can effectively cleave the Cß-O-4 bond existed in PP-ol under simulated sunlight. The highest conversion of PP-ol was 89.5% with phenol and acetophenone yields of 66.2% and 33.5%, respectively. The mechanism studies confirm that the Cα-H in PP-ol and lignin is firstly dehydrogenated to form Cα radical intermediates, and then the photogenerated electrons break the adjacent Cß-O bond. This research provides a new strategy to prepare valuable chemicals by virtue of renewable biomass and simulated sunlight.

Sunlight Photocatalytic Performance of ZnO Nanoparticles Synthesized by Green Chemistry Using Different Botanical Extracts and Zinc Acetate as a Precursor.

In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14-32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.

Detection of a pheomelanin-like pigment by EPR spectroscopy in the mycelium of Plenodomus biglobosus.

Melanin occurrence in Plenodomus biglobosus was investigated using electron paramagnetic (spin) resonance (EPR, ESR) spectroscopy. The fungus was isolated from living and dead leaves of European ash (Fraxinus excelsior L.). Dark pigmentation of P. biglobosus mycelium in vitro, especially on the reverse, was observed. The black coloration intensified with the age of the culture and inspired us to check if the analyzed fungus species synthesizes melanin. Melanin contains unpaired electrons, thus, EPR spectroscopy was applied, as a specific technique, to verify its presence in P. biglobosus. The EPR spectrum of the mycelium showed a very strong melanin signal, revealing pheomelanin-like features. Thus, the black pigment of P. biglobosus was clearly identified as melanin. However, no melanin was detected in the apparently dark culture medium even when zinc (II) acetate was added to increase the sensitivity of detection. Pheomelanin has many unusual biological functions but it is not commonly found in fungi. Detection of this type of melanin in P. biglobosus, which can be both endophytic or pathogenic, suggests a closer examination of the potential role of this melanin in host-parasite interaction.

Comparison of different zinc precursors for the construction of zeolitic imidazolate framework-8 artificial shells on living cells.

The robust cell-in-shell structure is highly desirable for endowing living cells with an artificial exoskeleton to defend them from many environmental factors such as osmotic pressure, shear force, heat, UV radiation, and enzymes. Cell encapsulation has shown potential applications in many fields and attracted increasing interest. However, the influences of the precursors on the cell viability during the shell formation process are not clear and seldom investigated. Here, zinc nitrite, zinc acetate and zinc sulfate were applied individually to synthesize zeolitic imidazolate framework-8 (ZIF-8) shells on living cells. All the zinc salt precursors could convert to a ZIF-8 layer on the living cell surface. The zinc salts and organic ligand did not exhibit obvious toxicity to yeast cells when applied individually. However, dead cells were observed during the living cell encapsulation process using different zinc precursors. Compared with zinc nitrate and zinc acetate, ZIF-8 formed by zinc sulfate led to a higher percentage of cell death, especially under high concentrations of zinc sulfate. Cell division was suppressed by the ZIF-8 shell but restored fully upon shell removal by EDTA solution or pH 4.0 buffer. Escherichia coli (E. coli) cells showed a lower percentage of cell death, indicating excellent tolerance to the ZIF-8 encapsulation process. This work illustrates the cell toxicity during the formation of ZIF-8 cell shells by different zinc salts and engineering of the cell growth by MOF coating, which could provide a foundation for further quantitative analysis and potential applications in biomedicine and bioengineering.

Application of Acyzol in the Context of Zinc Deficiency and Perspectives.

Zinc is one of the most important essential trace elements. It is involved in more than 300 enzyme systems and is an indispensable participant in many biochemical processes. Zinc deficiency causes a number of disorders in the human body, the main ones being the delay of growth and puberty, immune disorders, and cognitive dysfunctions. There are over two billion people in the world suffering from zinc deficiency conditions. Acyzol, a zinc-containing medicine, developed as an antidote against carbon monoxide poisoning, demonstrates a wide range of pharmacological activities: Anti-inflammatory, reparative, detoxifying, immunomodulatory, bacteriostatic, hepatoprotective, adaptogenic, antioxidant, antihypoxic, and cardioprotective. The presence of zinc in the composition of Acyzol suggests the potential of the drug in the treatment and prevention of zinc deficiency conditions, such as Prasad's disease, immune system pathology, alopecia, allergodermatoses, prostate dysfunction, psoriasis, stomatitis, periodontitis, and delayed mental and physical development in children. Currently, the efficiency of Acyzol in the cases of zinc deficiency is shown in a large number of experimental studies. So, Acyzol can be used as a highly effective drug for pharmacologic therapy of a wide range of diseases and conditions and it opens up new perspectives in the treatment and prevention of zinc deficiency conditions.

Disassociation of glutamate from γ-aminobutyric acid by zinc acetate-assisted differential precipitation/dissolution: Application to the quantification of γ-aminobutyric acid.

γ-aminobutyric acid (GABA) is a key physiologically active molecule in organisms. Separation of glutamate from its decarboxylated product GABA has been vigorously pursued. The interaction between these two compounds severely hindered their disassociation. Herein, we present a new strategy, termed zinc acetate-assisted differential precipitation/dissolution (ZA-DPD), for the removal of glutamate by step by step recovering pure GABA solution and discarding pure glutamate pellet, essentially attributed to the use of two core reagents (zinc acetate-assisted glutamate-precipitating reagent, and glutamate-rejecting reagent). In each precipitation, the zinc acetate-assisted glutamate-precipitating reagent guaranteed most GABA still soluble although the rest co-precipitated with glutamate; in the coupled dissolution, the co-precipitated GABA was fully dissolved with or without (in the case of glutamate-rejecting reagent used in the final dissolution) co-dissolution of glutamate. The process was repeated twice until glutamate was thoroughly removed. An accurate quantitative method coupling ZA-DPD with colorimetry was thereafter established for the determination of GABA. This study may facilitate the areas associated with GABA or glutamate.

Long-Acting Release Microspheres Containing Novel GLP-1 Analog as an Antidiabetic System.

Glucagon-like peptide 1 (GLP-1) has recently received significant attention as an efficacious way to treat diabetes mellitus. However, the short half-life of the peptide limits its clinical application in diabetes. In our previous study, a novel GLP-1 analog (PGLP-1) with a longer half-life was synthesized and evaluated. Herein, we prepared the PGLP-1-loaded poly(d,l-lactide- co-glycolide) microspheres to achieve long-term effects on blood glucose control. The incorporation of zinc ion into the formulation can effectively decrease the initial burst release, and a uniform drug distribution was obtained, in contrast to native PGLP-1 encapsulated microspheres. We demonstrated that the solubility of the drug encapsulated in microspheres played an important role in in vitro release behavior and drug distribution inside the microspheres. The Zn-PGLP-1 microspheres had a prominent acute glucose reduction effect in the healthy mice. A hypoglycemic effect was observed in the streptozotocin (STZ) induced diabetic mice through a 6-week treatment of Zn-PGLP-1-loaded microspheres. Meanwhile, the administration of Zn-PGLP-1 microspheres led to the ß-cell protection and stimulation of insulin secretion. The novel GLP-1 analog-loaded sustained microspheres may greatly improve patient compliance along with a desirable safety feature.

Enhanced antibacterial nanocomposite mats by coaxial electrospinning of polycaprolactone fibers loaded with Zn-based nanoparticles.

ZnO and Zn acetate nanoparticles were embedded in polycaprolactone coaxial-fibers and uniaxial-fibers matrices to develop potential antibacterial nanocomposite wound dressings (mats). Morphology, composition, wettability, crystallinity and fiber structure of mats were characterized. Antibacterial properties of mats were tested against E. coli and S. aureus by turbidity and MTT assays. The effect of UVA illumination (prior to bacteria inoculation) on mats' antibacterial activity was also studied. Results showed that a coaxial-fibers design maintained nanoparticles distributed in the outer-shell of fibers and, in general, enhanced the antibacterial effect of the mats, in comparison to conventional uniaxial-fibers mats. Results indicated that mats simultaneously inhibited planktonic and biofilm bacterial growth by, probably, two main antibacterial mechanisms; 1) release of Zn2+ ions (mainly from Zn acetate nanoparticles) and 2) photocatalytic oxidative processes exerted by ZnO nanoparticles. Antibacterial properties of mats were significantly improved by coaxial-fibers design and exposure to UVA-light prior to bacteria inoculation.

Influence of Aspartate Moieties on the Self-Healing Behavior of Histidine-Rich Supramolecular Polymers.

Aspartate incorporated into the protein structure of mussel byssal threads is believed to play an important role, besides the reversible histidine-zinc interactions, in the self-healing behavior of mussel byssal threads. Therefore, copolymers containing both aspartate and histidine moieties are synthesized in order to investigate the influence of aspartate on the complexation of zinc(II) as well as on the self-healing behavior and the mechanical properties of the resulting supramolecular networks. For this purpose, isothermal titration calorimetry measurements of a model aspartate compound as well as of these copolymers are performed and the thermodynamic parameters are utilized for the design of self-healing copolymers. For this purpose, n-lauryl methacrylate-based copolymers containing histidine and aspartate are synthesized and crosslinked with zinc(II) acetate. The self-healing behavior of the supramolecular networks is investigated using scratch healing tests and the mechanical properties by nanoindentation.

Zn(OAc)2-Catalyzing Ring-Opening Polymerization of N-Carboxyanhydrides for the Synthesis of Well-Defined Polypeptides.

Despite notable progress, the fabrication of well-defined polypeptides via controlled ring-opening polymerization (ROP) of α-amino acid N-carboxyanhydrides (NCAs) using convenient catalysts under mild conditions in a relatively short polymerization time is still challenging. Herein, an easily obtained catalyst system composed of zinc acetate and aniline was explored to mediate the fast ROP of γ-benzyl-l-glutamate-N-carboxyanhydride (BLG-NCA) monomer, to produce poly(γ-benzyl-l-glutamates) (PBLGs) with controllable molecular weights and narrow dispersity. Considering the excellent cooperative action of zinc acetate and a broad scope of aniline derivatives with different functional groups to control ROP of BLG-NCA, this method may offer a useful platform enabling the rapid generation of end-functionalized PBLG and block copolymers for numerous biomedical applications.

Rapid, controllable, one-pot and room-temperature aqueous synthesis of ZnO:Cu nanoparticles by pulsed UV laser and its application for photocatalytic degradation of methyl orange.

Zinc oxide (ZnO) and ZnO:Cu nanoparticles (NPs) were synthesized using a rapid, controllable, one-pot and room-temperature pulsed UV-laser assisted method. UV-laser irradiation was used as an effective energy source in order to gain better control over the NPs size and morphology in aqueous media. Parameters effective in laser assisted synthesis of NPs such as irradiation time and laser shot repetition rate were optimized. Photoluminescence (PL) spectra of ZnO NPs showed a broad emission with two trap state peaks located at 442 and 485 nm related to electronic transition from zinc interstitial level (IZn ) to zinc vacancy level (VZn ) and electronic transition from conduction band to the oxygen vacancy level (VO ), respectively. For ZnO:Cu NPs, trap state emissions disappeared completely and a copper (Cu)-related emission appeared. PL intensity of Cu-related emission increased with the increase in concentration of Cu2+ , so that for molar ratio of Cu:Zn 2%, optimal value of PL intensity was obtained. The photocatalytic activity of Cu-doped ZnO revealed 50 and 100% increasement than that of undoped NPs under UV and visible irradiation, respectively. The enhanced photocatalytic activity could be attributed to smaller crystal size, as well as creation of impurity acceptor levels (T2 ) inside the ZnO energy band gap.

[Secondary Structure of Aß(1-16) Complexes with Zinc: A Study in the Gas Phase Using Deuterium/Hydrogen Exchange and Ultra-High-Resolution Mass Spectrometry].

Complexes of peptide fragment 1-16 of beta-amyloid with transition metals play an important role in the development of a broad class of neurodegenerative diseases, which determines the interest in investigating the structures of these complexes. In this work, we have applied the method of the deuterium/hydrogen exchange in combination with ultra-high-resolution mass spectrometry to study conformational changes in (1-16) beta-amyloid peptide induced by binding of zinc(II) atoms. The efficiency of the deuterium/hydrogen exchange depended on the number of zinc atoms bound to the peptide and on the temperature of the ionization source region. Deuterium/hydrogen exchange reactions have been performed directly in the ionization source. The number of exchanges decreased considerably with an increasing numbers of zinc atoms. The relationship has been described with a damped exponential curve, which indicated that the binding of zinc atoms altered the conformation of the peptide ion by making it less open, which limits the access to inner areas of the molecule.

Photometric Determination of Ammonium and Phosphate in Seawater Medium Using a Microplate Reader.

To more efficiently process the large sample numbers for quantitative determination of ammonium (NH4+) and phosphate (orthophosphate, PO43-) generated during comprehensive growth experiments with the marine Roseobacter group member Phaeobacter inhibens DSM 17395, specific colorimetric assays employing a microplate reader (MPR) were established. The NH4+ assay is based on the reaction of NH4+ with hypochlorite and salicylate, yielding a limit of detection of 14 µM, a limit of quantitation of 36 µM, and a linear range for quantitative determination up to 200 µM. The PO43-assay is based on the complex formation of PO43- with ammonium molybdate in the presence of ascorbate and zinc acetate, yielding a limit of detection of 13 µM, a limit of quantitation of 50 µM, and a linear range for quantitative determination up to 1 mM. Both MPR-based assays allowed for fast (significantly lower than 1 h) analysis of 21 samples plus standards for calibration (all measured in triplicates) and showed only low variation across a large collection of biological samples.

Effects of Acyzol on Zinc Content in Rat Brain and Blood Plasma.

Zinc level in the blood plasma and brain of rats was studied by inductively coupled plasma mass spectrometry. Maximum amount of zinc was observed in the cerebellum (15.0±5.5 µg/mg wet tissue). Single intraperitoneal administration of a zinc donor acyzol (24 mg/kg) did not change the content of this element in the tissues. Repeated injections of acyzol (7 injections over 14 days) significantly increased zinc level in rat plasma and brain. This elevation was most pronounced in the forebrain (cortex and subcortical structures). The rise in zinc concentration in blood plasma correlated with its level in the brain.

The Cysteine S-Alkylation Reaction as a Synthetic Method to Covalently Modify Peptide Sequences.

Synthetic methodologies to chemically modify peptide molecules have long been investigated for their impact in the field of chemical biology. They allow the introduction of biochemical probes useful for studying protein functions, for manipulating peptides with therapeutic potential, and for structure-activity relationship investigations. The commonly used approach was the derivatization of an amino acid side chain. In this regard, the cysteine, for its unique reactivity, has been widely employed as the substrate for such modifications. Herein, we report on methodologies developed to modify the cysteine thiol group through the S-alkylation reaction. Some procedures perform the alkylation of cysteine derivatives, in order to prepare building blocks to be used during the peptide synthesis, whilst some others selectively modify peptide sequences containing a cysteine residue with a free thiol group, both in solution and in the solid phase.

Bio-medically active zinc oxide nanoparticles synthesized by using extremophilic actinobacterium, Streptomyces sp. (MA30) and its characterization.

The present study describes the synthesis of zinc oxide nanoparticles (ZnO-NPs) using an extremophilic actinobacterial cell-free extract, supplied with aqueous zinc acetate solution. Crystalline nature, morphological features, and polydispersed nanoparticles size (15-30 nm) were identified by X-ray diffraction (XRD), atomic force and electron microscopic analysis with dynamic light scattering (DLS) study. The interaction between biomolecules and ZnO-NPs was analyzed using Fourier transform infra-red spectroscopy (FT-IR). Furthermore antibacterial, antioxidant activities, and cell viability test of ZnO-NPs were systematically evaluated. The present study opens a new avenue for the actinobacterial synthesis of oxide nanoparticles.

Performance of ZnO synthesized by sol-gel as photocatalyst in the photooxidation reaction of NO.

ZnO samples were prepared by sol-gel method applying a factorial design in order to improve the photocatalytic properties of the semiconductor oxide in the NO photooxidation reaction. The concentrations of zinc acetate and ammonium hydroxide were selected as critical variables in the synthesis of ZnO. Nine samples of ZnO were obtained as product of the factorial design and were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, diffuse reflectance spectroscopy, and N2 adsorption-desorption isotherms. The photocatalytic activity of ZnO samples was associated with the physical properties developed by each sample according to its respective conditions of synthesis. Some photocatalytic reaction parameters, such as mass of photocatalyst, irradiance, and relative humidity, were modified in order to evaluate its effect in the photocatalytic conversion of NO. As a relevant point, the relative humidity played an important role in the increase of the selectivity of the NO photooxidation reaction to innocuous nitrate ions when ZnO was used as photocatalyst.

Rapid Isolation and Determination of Flavones in Biological Samples Using Zinc Complexation Coupled with High-Performance Liquid Chromatography.

Chlorophyll-type contaminants are commonly encountered in the isolation and determination of flavones of plant aerial plant parts. Heme is also a difficult background substance in whole blood analysis. Both chlorophyll and heme are porphyrin type compounds. In this study, a rapid method for isolating flavones with 5-hydroxyl or ortho-hydroxyl groups from biological samples was developed based on the different solubilities of porphyrin-metal and flavone-metal complexes. It is important that other background substances, e.g., proteins and lipids, are also removed from flavones without an additional processing. The recoveries of scutellarin, baicalin, baicalein, wogonoside and wogonin, which are the primary constituents of Scutellaria baicalensis (skullcaps) were 99.65% ± 1.02%, 98.98% ± 0.73%, 99.65% ± 0.03%, 97.59% ± 0.09% and 95.19% ± 0.47%, respectively. As a sample pretreatment procedure, this method was coupled to high-performance liquid chromatography (HPLC) with good separation, sensitivity and linearity and was applied to determine the flavone content in different aerial parts of S. baicalensis and in dried blood spot samples.

Enhancement of site specific delivery of diloxanide furoate as an antiamoebic drug.

The basic aim of the present research work is to deliver the diloxanide furoate (DF) at specific area using pectin microspheres. The microspheres were prepared by spray drying method and cross-linked by zinc acetate. Different concentrations of polymer (pectin 0.5-3%) and cross-linking agent (0-3% w/v in a mixture of ethanol:water) are taken to optimize the entrapment efficiency, swelling behavior, size and first 6h in-vitro release in simulated gastric fluids. Optimized formulation was characterized in the terms of in-vitro release, in-vivo drug disposition in various organs and in the blood of Sprague-Dawley albino rats and in-vivo gastrointestinal tract transit behavior using X-ray imaging method on albino rabbits. Findings suggested that microspheres containing a concentration of polymer (2% w/v) have average size of 100-500 µm, entrapment efficiency 85.82 ± 0.5 with swelling index 18.77 ± 5.21. In-vitro results and in-vivo gastric transit behavior (using X-ray imaging) have shown no release in first 3-6h that proved the colon specific delivery of DF. The results also suggested that the above approach have not only site specific delivery, but it improves the conversion of active drug by increasing the enzyme mediated hydrolytic degradation of DF due to the presence of polysaccharide polymer:water gel complex.

Dual mode ratiometric recognition of zinc acetate: nanomolar detection with in vitro tracking of endophytic bacteria in rice root tissue.

Several naphthalene-based aldazine derivatives were developed as efficient colorimetric and fluorescence probes for selective ratiometric recognition of traces of zinc acetate. The derivative structures were characterized by single-crystal X-ray diffraction. The probes were used for in vitro tracking of zinc acetate in endophytic bacteria within rice root tissue and to image zinc acetate in human breast cancer cells (MCF7) by normal and fluorescence microscopy. Density functional theoretical studies were in close agreement with the experimental findings.