The galvanization of biology: a growing appreciation for the roles of zinc

Zinc Finger Proteins in the Human Fungal Pathogen Cryptococcus neoformans

Zinc is one of the essential trace elements in eukaryotes and it is a critical structural component of a large number of proteins. Zinc finger proteins (ZNFs) are zinc-finger domain-containing proteins stabilized by bound zinc ions and they form the most abundant proteins, serving extraordinarily diverse biological functions. In recent years, many ZNFs have been identified and characterized in the human fungal pathogen Cryptococcus neoformans, a fungal pathogen causing fatal meningitis mainly in immunocompromised individuals. It has been shown that ZNFs play important roles in the morphological development, differentiation, and virulence of C. neoformans. In this review, we, first, briefly introduce the ZNFs and their classification. Then, we explain the identification and classification of the ZNFs in C. neoformans. Next, we focus on the biological role of the ZNFs functionally characterized so far in the sexual reproduction, virulence factor production, ion homeostasis, pathogenesis, and stress resistance in C. neoformans. We also discuss the perspectives on future function studies of ZNFs in C. neoformans.

A 4-N,N-dimethylaminoaniline salicylaldehyde Schiff-base solution-solid dual emissive fluorophore: An aggregation-induced turquoise emission characteristics in liquid as a fluorescent probe for Zn2+ response; a strong near-infrared emission in solid state and application for optical data storage

A new Schiff-base 1 based on 4-N,N-dimethylaminoaniline salicylaldehyde is developed. It possesses unique solution-solid dual emission behaviour with emission color: an aggregation-induced bright turquoise emission in liquid and strong near-infrared emission in the solid state. Interestingly, on the one hand, compound 1 is promising a ratiometric fluorescent probe for Zn²⁺ ions detection in the aqueous solution with high sensitivity, selectivity, and relatively low detection limit. On the other hand, based on its inner stimuli-responsive nature, outstanding thermostability and photostability, 1 should be a very promising candidate for the write-once read-many optical data storage medium.

C-Terminal Domain of the Human Zinc Transporter hZnT8 Is Structurally Indistinguishable from Its Disease Risk Variant (R325W)

The human zinc transporter 8 (hZnT8) plays important roles in the storage of insulin in the secretory vesicles of pancreatic β cells. hZnT8 consists of a transmembrane domain, with its N- and C-termini protruding into the cytoplasm. Interestingly, the exchange of arginine to tryptophan at position 325 in the C-terminal domain (CTD) increases the risk of developing type 2 diabetes mellitus (T2D). In the present study, the CTDs of hZnT8 (the wild-type (WT) and its disease risk variant (R325W)) were expressed, purified, and characterized in their native forms by biophysical techniques. The data reveal that the CTDs form tetramers which are stabilized by zinc binding, and exhibit negligible differences in their secondary structure content and zinc-binding affinities in solution. These findings provide the basis for conducting further structural studies aimed at unravelling the molecular mechanism underlying the increased susceptibility to develop T2D, which is modulated by the disease risk variant.

Hepatitis E Virus Cysteine Protease Has Papain Like Properties Validated by in silico Modeling and Cell-Free Inhibition Assays

Hepatitis E virus (HEV) has emerged as a global health concern during the last decade. In spite of a high mortality rate in pregnant women with fulminant hepatitis, no antiviral drugs or licensed vaccine is available in India. HEV-protease is a pivotal enzyme responsible for ORF1 polyprotein processing leading to cleavage of the non-structural enzymes involved in virus replication. HEV-protease region encoding 432–592 amino acids of Genotype-1 was amplified, expressed in Sf21 cells and purified in its native form. The recombinant enzyme was biochemically characterized using SDS-PAGE, Western blotting and Immunofluorescence. The enzyme activity and the inhibition studies were conducted using Zymography, FTC-casein based protease assay and ORF1 polyprotein digestion. To conduct ORF1 digestion assay, the polyprotein, natural substrate of HEV-protease, was expressed in E. coli and purified. Cleavage of 186 kDa ORF1 polyprotein by the recombinant HEV-protease lead to appearance of non-structural proteins viz. Methyltransferase, Protease, Helicase and RNA dependent RNA polymerase which were confirmed through immunoblotting using antibodies generated against specific epitopes of the enzymes. FTC-casein substrate was used for kinetic studies to determine Km and Vmax of the enzyme and also the effect of different metal ions and other protease inhibitors. A 95% inhibition was observed with E-64 which was validated through in silico analysis. The correlation coefficient between inhibition and docking score of Inhibitors was found to have a significant value of r² = 0.75. The predicted 3D model showed two domain architecture structures similar to Papain like cysteine protease though they differed in arrangements of alpha helices and beta sheets. Hence, we propose that HEV-protease has characteristics of “Papain-like cysteine protease,” as determined through structural homology, active site residues and class-specific inhibition. However, conclusive nature of the enzyme remains to be established.

Solid-State Emissive Metallo-Supramolecular Assemblies of Quinoline-Based Acyl Hydrazone

Development of fluorescence-based sensory materials for metal elements is currently in the mainstream of research due to the simplicity and usability of fluorescence as a method of detection. Herein, we report a novel "bis"-quinoline-based acyl hydrazone-named bQH that could be synthesized by a facile, low-cost method through simple condensation of hydrazide with an aldehyde. This acyl hydrazone showed emissive properties through Zn selective binding, especially in its solid-state, as shown by experiments such as UV-Vis, photoluminescence (PL), nuclear magnetic resonance (NMR), and inductively-coupled plasma-optical emission spectroscopies (ICP-OES), and energy-dispersive X-ray spectroscopy (EDS) mapping. The binding modes in which bQH coordinates to Zn2+ was proved to consist of two modes, 1:1 and 1:2 (bQH:Zn2+), where the binding mode was controlled by the Zn2+ ion content. Under the 1:1 binding mode, bQH-Zn2+ complexes formed a polymeric array through the metallo-supramolecular assembly. The resulting bQH-Zn2+ complex maintained its fluorescence in solid-state and exhibited excellent fluorescence intensity as compared to the previously reported quinoline-based acyl hydrazone derivative (mQH).

Identification of CCCH Zinc Finger Proteins Family in Moso Bamboo (Phyllostachys edulis), and PeC3H74 Confers Drought Tolerance to Transgenic Plants

CCCH zinc finger proteins are a class of important zinc-finger transcription factors and have functions in various plant growth and stress responses, but their functions in moso bamboo (Phyllostachys edulis) are unclear. In this current study, we main investigated the structures, phylogenetic relationships, promoter elements and microsynteny of PeC3Hs. In this research, 119 CCCH zinc finger proteins (PeC3H1-119) identified genes in moso bamboo were divided into 13 subfamilies (A-M) based on phylogenetic analysis. Meanwhile, moso bamboo were treated with abscisic acid (ABA), methyl jasmonate (Me-JA) and gibberellic acid (GA) and 12 CCCH genes expression levels were assayed using qRT-PCR. In the three hormone treatments, 12 genes were up-regulated or down-regulated, respectively. In addition, PeC3H74 was localized on the cytomembrane, and it had self-activation activities. Phenotypic and physiological analysis showed that PeC3H74 (PeC3H74-OE) conferred drought tolerance of transgenic Arabidopsis, including H₂O₂ content, survival rate, electrolyte leakage as well as malondialdehyde content. Additionally, compared with wild-type plants, transgenic Arabidopsis thaliana seedling roots growth developed better under 10 μM ABA; Moreover, the stomatal of over-expressing PeC3H74 in Arabidopsis changed significantly under ABA treatment. The above results suggest that PeC3H74 was quickly screened by bioinformatics, and it may enhanced drought tolerance in plants through the ABA-dependent signaling pathway.

A fluorescent sensor for intracellular Zn2+ based on cylindrical molecular brushes of poly(2-oxazoline) through ion-induced emission

Poly(2-oxazoline) molecular brushes bearing enaminitrile receptors in the side chain ends exhibit good biocompatibility, excellent fluorescent selectivity for Zn²⁺, and possibility in detecting intracellular Zn²⁺.

A novel study on curcumin metal complexes: solubility improvement, bioactivity, and trial burn wound treatment in rats

This paper describes a new technique to enhance the solubility of metal curcumin complexes.

Sensing of zinc ions and sulfide using a highly practical and water-soluble fluorescent sensor: applications in test kits and zebrafish

A practical fluorescent sensor was synthesized for recognition of Zn²⁺ and S²⁻ and applied in various applications such as in live zebrafish.

The oxidative dehydrogenation of a coumarinyl scaffold with copper ion and metal ion detection in human liver cancer cells (HepG2)

An unsymmetrical o-phenylenediamine derivative, L (7-hydroxy-4-methyl-8-(1-(phenyl- (pyridin-2-yl)methyl)-1H-benzo[d]imidazol-2-yl)-2H-chromen-2-one), has been synthesized from (E)-N¹-(phenyl(pyridine-2-yl)methylene)benzene-1,2-diamine with 7-hydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde and characterized by X-ray, IR, ¹H NMR and ESI-MS spectral analyses. The X-ray structure shows L as a cyclic benzimidazole derivative, but it undergoes ring-opening upon reaction with transition metal ions. L is non-emissive in 9 : 1 (v/v) EtOH/H₂O (HEPES buffer, pH 7.4) but becomes highly fluorescent upon Zn²⁺ coordination, and the emissive Zn(ii) complex undergoes transmetallation in the presence of Cu²⁺ ions specifically, followed by amine to imine oxidation, i.e. an oxidative dehydrogenation (OD) reaction -(2e + 2H⁺) occurs. The transmetallation of Zn²⁺ from the complex by Cu²⁺ (CuCl₂) separated the non-emissive X-ray diffractable crystal of [Cu(L'')Cl] (L'' = amine oxidized form of L). A square pyramidal [Cu(L'')][ClO₄] complex was also isolated from the reaction of L with Cu(CH₃CN)₄(ClO₄) in the presence of air, and in this complex the amine is also oxidized to the imine. Here, copper ions in the presence of air play an important role in the OD reaction of L as determined by EPR and cyclic voltammetry studies. The ligand, L, is used for Zn²⁺ ion recovery from a municipally supplied water sample. A paper strip detection kit for Zn²⁺ and Cu²⁺ is designed using L. The ligand is also used for intracellular Zn²⁺ detection in a human liver cancer cell line (HepG2).

Conditional nutrition (I): concerning zinc as a beneficial but variable regulator of inflammation and experimental arthritis

This article extends the concept of conditional pharmacology (Whitehouse and Vernon-Roberts 1991; Whitehouse 1995) that considers how both internal factors/disease and external/environmental factors may alter the availability or efficacy of exogenous drugs. The same and other conditioning factors may also affect the utility and value of many nutriceuticals that may be clearly beneficial in the context of inflammation but sometimes showing quite variable pharmaco-activity. This is illustrated by considering some factors affecting the bioavailability and pharmaco-efficacy of dietary ionic zinc, Zn (II) an essential trace metal and a critical regulator of inflammation and tissue repair. With chronic zinc deficiency (zincopenia) due to diet, drugs and/or disease, we can usually survive-but may not necessarily thrive. Some strategies to minimise zincopenia are considered, based upon finding efficient means for (1) preventing its cause and/or (2) using parenteral delivery of zinc supplements to circumvent dietary and enteric impediments to zinc bio-availability.

Genome-wide identification of C2H2 zinc-finger genes and their expression patterns under heat stress in tomato (Solanum lycopersicum L.)

The C2H2 zinc finger protein (C2H2-ZFP) transcription factor family regulates the expression of a wide variety of genes in response to various developmental processes or abiotic stresses; however, these proteins have not yet been comprehensively analyzed in tomato (Solanum lycopersicum). In this study, a total of 104 C2H2-ZFs were identified in an uneven distribution across the entire tomato genome, and include seven segmental duplication events. Based on their phylogenetic relationships, these genes were clustered into nine distinct categories analogous to those in Arabidopsis thaliana. High similarities were found between the exon–intron structures and conserved motifs of the genes within each group. Correspondingly, the expression patterns of the C2H2-ZF genes indicated that they function in different tissues and at different developmental stages. Additionally, quantitative real-time PCR (qRT-PCR) results demonstrated that the expression levels of 34 selected C2H2-ZFs are changed dramatically among the roots, stems, and leaves at different time points of a heat stress treatment, suggesting that the C2H2-ZFPs are extensively involved in the heat stress response but have potentially varying roles. These results form the basis for the further molecular and functional analysis of the C2H2-ZFPs, especially for those members that significantly varied under heat treatment, which may be targeted to improve the heat tolerance of tomato and other Solanaceae species.

Functional analysis of SlNCED1 in pistil development and fruit set in tomato (Solanum lycopersicum L.)

Abscisic acid (ABA) is an important regulator of many plant developmental processes, although its regulation in the pistil during anthesis is unclear. We investigated the role of 9-cis-epoxycarotenoid dioxygenase (SlNCED1), a key ABA biosynthesis enzyme, through overexpression and transcriptome analysis in the tomato pistil. During pistil development, ABA accumulates and SlNCED1 expression increases continually, peaking one day before full bloom, when the maximum amount of ethylene is released in the pistil. ABA accumulation and SlNCED1 expression in the ovary remained high for three days before and after full bloom, but then both declined rapidly four days after full bloom following senescence and petal abscission and expansion of the young fruits. Overexpression of SlNCED1 significantly increased ABA levels and also up-regulated SlPP2C5 expression, which reduced ABA signaling activity. Overexpression of SlNCED1 caused up-regulation of pistil-specific Zinc finger transcription factor genes SlC3H29, SlC3H66, and SlC3HC4, which may have affected the expression of SlNCED1-mediated pistil development-related genes, causing major changes in ovary development. Increased ABA levels are due to SlNCED1 overexpresson which caused a hormonal imbalance resulting in the growth of parthenocarpic fruit. Our results indicate that SlNCED1 plays a crucial role in the regulation of ovary/pistil development and fruit set.

An antipyrine based fluorescence "turn-on" dual sensor for Zn2+ and Al3+ and its selective fluorescence "turn-off" sensing towards 2,4,6-trinitrophenol (TNP) in the aggregated state

A 2,6-diformyl-p-cresol (DFC)-4-amino antipyrine (AP) based dual signaling fluorescent Schiff base ligand (DFCAP) is found to exhibit colorimetric and fluorescence turn on selective sensing towards metal ions, Zn2+ and Al3+. It also exhibits a significant aggregation induced emission (AIE) phenomenon by controlling the water-THF solvent ratio which provides robust green emissive fluorogenic aggregates with well-defined morphologies. Turn-on fluorescence enhancements as high as 195 fold and 168 fold in methanol for Al3+ and Zn2+ at 480 nm and 508 nm, respectively, were noticed. The binding constants and stoichiometry determined from the fluorescence titration data are K = 7.63 × 104 M-1 and 3.42 × 104 M-1 and 1 : 1 complexation for both Al3+ and Zn2+ respectively, supported by Job's method. DFCAP shows high sensitivity towards the detection of Zn2+ and Al3+ ions with very low detection limit values of ca. ∼21 nM and 30 nM respectively. Besides by applying its attractive AIE feature, the green emissive hydrosol functions as a good chemosensor with high sensitivity for a selected explosive TNP through ground state complexation with a LOD value of ca. ∼1.74 μM and especially a high Stern-Volmer quenching constant of ca. ∼4.14 × 105 M-1. For instant 'naked eye' response for the trace detection of TNP in the solution state, we fabricated a simple paper strip that could detect TNP on-site in a fast, inexpensive and simple way.

Cytokinin-dependent regulatory module underlies the maintenance of zinc nutrition in rice

Zinc (Zn) deficiency is a critical problem in human nutrition. Rice is the main source of calories for nearly half the world's population but has the shortcoming, from a nutritional perspective, of being low in Zn and other essential nutrients. Here we performed analyses with cytokinin-related mutants and transgenic lines to provide unequivocal evidence that cytokinins have a key role in controlling Zn status in plants. Transporters responsible for Zn uptake and chelators for the internal transport of Zn were strictly controlled by cytokinins. Moreover, cytokinin metabolism was regulated in a highly dynamic way in response to Zn status, which allows rice to adapt to heterogeneous Zn availability. Subsequently, fine-tuning of cytokinin metabolism by root-specific expression of a cytokinin degradation enzyme was able to improve both Zn nutrient and yield traits. Importantly, X-ray fluorescence imaging revealed that the increased Zn was broadly distributed from the aleurone layer to the inner endosperm. These findings show that metabolic control of cytokinin could provide the key to breeding Zn-enriched rice.

Role of Zinc in Immune System and Anti-Cancer Defense Mechanisms

The human body cannot store zinc reserves, so a deficiency can arise relatively quickly, e.g., through an improper diet. Severe zinc deficiency is rare, but mild deficiencies are common around the world. Many epidemiological studies have shown a relationship between the zinc content in the diet and the risk of cancer. The anti-cancer effect of zinc is most often associated with its antioxidant properties. However, this is just one of many possibilities, including the influence of zinc on the immune system, transcription factors, cell differentiation and proliferation, DNA and RNA synthesis and repair, enzyme activation or inhibition, the regulation of cellular signaling, and the stabilization of the cell structure and membranes. This study presents selected issues regarding the current knowledge of anti-cancer mechanisms involving this element.

Elevated zinc transporter ZnT3 in the dentate gyrus of mast cell-deficient mice

Zinc is important in neurogenesis, but excessive levels can cause apoptosis and other pathologies leading to cognitive impairments. Mast cells are present in many brain regions including the hippocampus, an area rich in vesicular zinc. Mast cells contain zinc-rich granules and a well-developed mechanism for uptake of zinc ions; both features point to the potential for a role in zinc homeostasis. Prior work using the Timm stain supported this hypothesis, as increased labile zinc was detected in the hippocampus of mast cell-deficient mice compared to wild-type mice while no differences in total zinc were found between the two genotypes in the whole brain or other tissues. The current report further examines differences in zinc homeostasis between wild-type and mast cell-deficient mice by exploring the zinc transporter ZnT3, which transports labile zinc into synaptic vesicles. The first study used immunocytochemistry to localize ZnT3 within the mossy fibre layer of the hippocampus to determine whether there was differential expression of ZnT3 in wild-type versus mast cell-deficient mice. The second study used inductively coupled plasma mass spectrometry (ICP-MS) to determine total zinc content in the whole dentate gyrus of the two genotypes. The immunocytochemical results indicate that there are higher levels of ZnT3 localized to the mossy fibre layer of the dentate gyrus of mast cell-deficient mice than in wild-type mice. The ICP-MS data reveal no differences in total zinc in dentate gyrus as a whole. The results are consistent with the hypothesis that mast cells participate in zinc homeostasis at the level of synaptic vesicles.

Phenothiazine-rhodamine-based colorimetric and fluorogenic 'turn-on' sensor for Zn2+ and bioimaging studies in live cells

A phenothiazine-rhodamine (PTRH) fluorescent dyad was synthesized and its ability to selectively sense Zn²⁺ ions in solution and in in vitro cell lines was tested using various techniques. When compared with other competing metal ions, the PTRH probe showed the high selectivity for Zn²⁺ ions that was supported by electronic and emission spectral analyses. The emission band at 528 nm for the PTRH probe indicated the ring closed form of PTRH, as for Zn²⁺ ion binding to PTRH, the λ_em get shift to 608 nm was accompanied by a pale yellow to pink colour (under visible light) and green to pinkish red fluorescence emission (under UV light) due to ring opening of the spirolactam moiety in the PTRH ligand. Spectral overlap of the donor emission band and the absorption band of the ring opened form of the acceptor moiety contributed towards the fluorescence resonance energy transfer ON mechanism for Zn²⁺ ion detection. The PTRH sensor had the lowest detection limit for Zn²⁺ , found to be 2.89 × 10^-8  M. The sensor also demonstrated good sensing application with minimum toxicity for in vitro analyses using HeLa cells.

The First-Row Transition Metals in the Periodic Table of Medicine

In this manuscript, we describe medical applications of each first-row transition metal including nutritional, pharmaceutical, and diagnostic applications. The 10 first-row transition metals in particular are found to have many applications since there five essential elements among them. We summarize the aqueous chemistry of each element to illustrate that these fundamental properties are linked to medical applications and will dictate some of nature’s solutions to the needs of cells. The five essential trace elements—iron, copper, zinc, manganese, and cobalt—represent four redox active elements and one redox inactive element. Since electron transfer is a critical process that must happen for life, it is therefore not surprising that four of the essential trace elements are involved in such processes, whereas the one non-redox active element is found to have important roles as a secondary messenger.. Perhaps surprising is the fact that scandium, titanium, vanadium, chromium, and nickel have many applications, covering the entire range of benefits including controlling pathogen growth, pharmaceutical and diagnostic applications, including benefits such as nutritional additives and hardware production of key medical devices. Some patterns emerge in the summary of biological function andmedical roles that can be attributed to small differences in the first-row transition metals.

Metallome of cerebrovascular endothelial cells infected with Toxoplasma gondii using μ-XRF imaging and inductively coupled plasma mass spectrometry

In this study, we measured the levels of elements in human brain microvascular endothelial cells (ECs) infected with T. gondii. ECs were infected with tachyzoites of the RH strain, and at 6, 24, and 48 hours post infection (hpi), the intracellular concentrations of elements were determined using a synchrotron-microfocus X-ray fluorescence microscopy (μ-XRF) system. This method enabled the quantification of the concentrations of Zn and Ca in infected and uninfected (control) ECs at sub-micron spatial resolution. T. gondii-hosting ECs contained less Zn than uninfected cells only at 48 hpi (p < 0.01). The level of Ca was not significantly different between infected and control cells (p > 0.05). Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis revealed infection-specific metallome profiles characterized by significant increases in the intracellular levels of Zn, Fe, Mn and Cu at 48 hpi (p < 0.01), and significant reductions in the extracellular concentrations of Co, Cu, Mo, V, and Ag at 24 hpi (p < 0.05) compared with control cells. Zn constituted the largest part (74%) of the total metal composition (metallome) of the parasite. Gene expression analysis showed infection-specific upregulation in the expression of five genes, MT1JP, MT1M, MT1E, MT1F, and MT1X, belonging to the metallothionein gene family. These results point to a possible correlation between T. gondii infection and increased expression of MT1 isoforms and altered intracellular levels of elements, especially Zn and Fe. Taken together, a combined μ-XRF and ICP-MS approach is promising for studies of the role of elements in mediating host-parasite interaction.

Inhibition of ZIP4 reverses epithelial-to-mesenchymal transition and enhances the radiosensitivity in human nasopharyngeal carcinoma cells

ZIP4 is a zinc transporter involved in epithelial cell morphology and migration in various cancers. In the epithelial-to-mesenchymal transition (EMT), epithelial cells transition into mesenchymal cells. The EMT plays a crucial role in invasiveness and metastasis during tumorigenesis. The aim of this study was to investigate the role of ZIP4 in the invasiveness and radiosensitivity of human nasopharyngeal carcinoma (NPC). In this study, results from 99 human patients with NPC showed that ZIP4 expression levels significantly correlated with a higher TN (tumor, lymph node) classification, as well as shorter overall survival (OS), recurrence-free survival (RFS), and distant metastasis-free survival (DMFS). Forced overexpression of ZIP4 promoted the migration and invasion of C666-1 cells through regulation of the EMT process. In contrast, ZIP4 silencing by lentivirus-mediated shRNA inhibited the EMT and metastasis of C666-1 cells in vitro and in vivo. Importantly, protein microarray analyses showed that downregulation of ZIP4 in C666-1 cells resulted in the decreased abundance of phosphoinositide 3-kinase (PI3K) p85 (Tyr607), phosphorylated (p)-Akt (Ser473), phosphorylated (p)-Akt (Thr308), and phosphorylated glycogen synthase kinase 3β (pGSK3β; Ser9). These data suggest that ZIP4 induces the EMT and promotes migration and invasion via the PI3K/Akt signaling pathway in NPC. Moreover, ZIP4 silencing significantly enhanced radiation-induced apoptosis and growth inhibition of human C666-1 cells in vitro and enhanced the antitumor activity of ionizing radiation (IR), leading to tumor growth inhibition in vivo. These results demonstrate that ZIP4 is a novel prognostic factor for malignant NPC progression. More importantly, targeting ZIP4, along with radiotherapy, may be an effective new treatment for NPC.

Fast and Reversible "Turn on" Fluorescent Sensors Based on Bisphenol-a for Zn2+ in Aqueous Solution

Two novel bisphenol-A derivatives (R1 and R2) linked pyrene and napthylthiazole moieties were synthesized via condensation reaction, and positively applied for the selective recognition of Zn²⁺ ion in EtOH/H₂O. Their optical properties were observed by using UV-vis and fluorescence measurements. R1 and R2 exhibited high selectivity and sensitivity towards Zn²⁺ over other metal ions. This fluorescence selectivity may be owing to inhibited excited-state intramolecular proton transfer (ESIPT) and photoinduced electron transfer (PET). The fluorescence titration analysis indicated detection limits of R1 and R2 for Zn²⁺ at 17.5 nM and 0.94 μM, respectively. Moreover, R1 and R2 were successfully applied to the detection of Zn²⁺ with different concentrations in water samples.

Full-color emission of a Eu3+-based mesoporous hybrid material modulated by Zn2+ ions: emission color changes for Zn2+ sensing via an ion exchange approach

We reported on the fabrication of a multicolor fluorescent sensor for Zn2+ ions based on the Eu complex functionalized mesoporous hybrid material Eu(TTA-MSN)2L (TTA: 2-thenoyltrifluoroacetone, HL: 4'-(4-carboxy-methyleneoxyphenyl)-2,2':6',2''-terpyridinel). The material was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and N2 adsorption measurements. The results revealed that the material preserves mesoscopically ordered structures and exhibited highly uniform pore size distributions. Spectroscopic analyses showed that the mesoporous hybrid material Eu(TTA-MSN)2L exhibited the characteristic emission of Eu3+ ions, reasonably long lifetimes (0.62 ms), and high quantum yields (18.4%). Moreover, the material displayed a highly selective and sensitive function toward Zn2+ ions in aqueous solutions. This sensing function could be attributed to the cation exchange of Eu3+ in the parent material Eu(TTA-MSN)2L with Zn2+. More importantly, by only modulating the concentration of Zn2+ ions in the water solution of Eu(TTA-MSN)2L, a tunable full-color emission (including white-light emission) can be generated under single-wavelength excitation. To our knowledge, this effort is the first example of a multicolor emissive sensor for Zn2+ ions in water solutions based on lanthanide mesoporous hybrid material.

Structured zinc oxide dressing for secondary intention wounds

OBJECTIVE

Inexpensive methods for more rapid healing of secondary intention wounds are sought. This pilot study measured the wound healing rate for a new zinc oxide structured dressing technique.

METHOD

In this study, we included the three patients with the largest wounds with onset during a one month period. A 3-ply gauze was cut and placed in the centre of each wound, leaving a 3-5mm rim of the wound exposed to the zinc gauze. The central gauze was soaked with 0.9% saline solution and the entire wound area was covered with 3 layers of Unna zinc oxide dressing. The central gauze size was modified to fit as the wound healed and the size changed. The wound was photographed at each visit and wound areas were obtained using best-fit ellipses.

RESULTS

The average wound closure rate is reported in the three wounds as 21.73mm² per day. The scalp wound healed at a rate of 21.45mm² per day.; the spider bite wound healed at a rate of 28.92mm² per day; and the thigh wound healed at a rate of 14.81mm² per day.

CONCLUSION

Healing rates for the zinc gauze method exceed those previously reported for full-thickness wounds healing by secondary intention. Additional study of the new technique with more patients is needed before conclusions relevant to clinical practice can be made.

Aggregation-Induced Emission-Based Sensing Platform for Selective Detection of Zn2+ : Experimental and Theoretical Investigations

Fluorescent chemosensors with aggregation induced emission enhancement (AIEE) emerge as promising tools in the field of sensing materials. Herein, we report the design, synthesis and applicability of a Schiff base chemosensor 1-(benzo[1,3]dioxol-4-ylmethylene-hydrazonomethyl)-naphthalen-2-ol (Hbdhn) of AIE characteristics that exhibits highly effective and selective response towards Zn²⁺ . The sensing effect of Hbdhn was evaluated by means of absorption/emission spectra and corresponding underlying photophysical mechanisms were proposed based on extensive quantum-chemical (TD)DFT calculations. The aggregated states in different DMSO/H₂ O ratios and in a presence of Zn²⁺ were examined by fluorescence lifetime measurements, dynamic light scattering and scanning electron microscopy studies. The bioimaging abilities of Hbdhn were evaluated for Zn²⁺ in HepG2 cancer cells. The results demonstrate instant, stable in time and reproducible, colorimetric turn-on response with superb selectivity and sensitivity of Hbdhn towards Zn²⁺ , based on chelation enhanced fluorescence mechanism. AIEE improves further Hbdhn properties, leading to strong, long-lived fluorescence, with appearance of rod-like particles, in 90 % of water in DMSO and only 10 % of water in DMSO in the presence of Zn²⁺ . All these features combined with successful biomaging studies make Hbdhn one of the most promising candidate for practical applications among recently proposed related systems.

High Energy Resolution-X-ray Absorption Near Edge Structure Spectroscopy Reveals Zn Ligation in Whole Cell Bacteria

Identifying the zinc (Zn) ligation and coordination environment in complex biological and environmental systems is crucial to understand the role of Zn as a biologically essential but sometimes toxic metal. Most studies on Zn coordination in biological or environmental samples rely on the extended X-ray absorption fine structure (EXAFS) region of a Zn K-edge X-ray absorption spectroscopy (XAS) spectrum. However, EXAFS analysis cannot identify unique nearest neighbors with similar atomic number (i.e., O versus N) and provides little information on Zn ligation. Herein, we demonstrate that high energy resolution-X-ray absorption near edge structure (HR-XANES) spectroscopy enables the direct determination of Zn ligation in whole cell bacteria, providing additional insights lost from EXAFS analysis at a fraction of the scan time and Zn concentration. HR-XANES is a relatively new technique that has improved our understanding of trace metals (e.g., Hg, Cu, and Ce) in dilute systems. This study is the first to show that HR-XANES can unambiguously detect Zn coordination to carboxyl, phosphoryl, imidazole, and/or thiol moieties in model microorganisms.

Effect of charge transfer and structural rigidity on divergent luminescence response of a metal organic framework towards different metal ions: luminescence lifetime decay experiments and DFT calculations

We have thoroughly studied the luminescence behaviour of a cadmium based MOF, [Cd(C12N2H8)(C7N1O4H3)] {C12N2H8 = 1,10-phenanthroline, C7N1O4H3 = 2,5-pyridine dicarboxylate}, 1. Both steady-state and time-resolved luminescence spectroscopic experiments were performed to understand the dissimilar responses of compound 1 towards different metal ions in aqueous medium. Upon excitation at 280 nm, compound 1 showed a luminescence spectrum centered at 365 nm, which exhibited a three-fold turn-on in the presence of a trace amount of Zn2+ in aqueous solution, whereas in the presence of Co2+, Hg2+, Ni2+, Fe2+ and Cu2+ the luminescence of compound 1 got largely quenched. Compound 1 did not show any response in the presence of other common metal ions such as K+, Mg2+, Na+, Mn2+, and Cr3+. By analysing all the experimental results, we successfully explained the versatile luminescence behaviour of compound 1. The turn-on of luminescence in the presence of Zn2+ ions was due to coordination bond formation and enhancement of the rigidity of compound 1 which resulted in the reduction of non-radiative decay processes to a large extent. The quenching of luminescence in the presence of transition metal ions was found to be static in nature, and was due to the possibility of ligand to metal charge transfer using the vacant d-orbital of the metal ions. In the case of Hg2+ which is a closed cell heavy metal ion, the quenching of luminescence was also static in nature and was due to a two-way charge transfer mechanism. We have also performed density functional theory calculations and obtained supportive results for the proposed mechanisms of luminescence turn-on and quenching. Moreover, compound 1 could be established as a selective and efficient sensor of Zn2+ in aqueous solution even in the presence of Cd2+ and other metal ions.

The redox biology of redox-inert zinc ions

Zinc(II) ions are redox-inert in biology. Yet, their interaction with sulfur of cysteine in cellular proteins can confer ligand-centered redox activity on zinc coordination sites, control protein functions, and generate signalling zinc ions as potent effectors of many cellular processes. The specificity and relative high affinity of binding sites for zinc allow regulation in redox biology, free radical biology, and the biology of reactive species. Understanding the role of zinc in these areas of biology requires an understanding of how cellular Zn²⁺ is homeostatically controlled and can serve as a regulatory ion in addition to Ca²⁺, albeit at much lower concentrations. A rather complex system of dozens of transporters and metallothioneins buffer the relatively high (hundreds of micromolar) total cellular zinc concentrations in such a way that the available zinc ion concentrations are only picomolar but can fluctuate in signalling. The proteins targeted by Zn²⁺ transients include enzymes controlling phosphorylation and redox signalling pathways. Networks of regulatory functions of zinc integrate gene expression and metabolic and signalling pathways at several hierarchical levels. They affect enzymatic catalysis, protein structure and protein-protein/biomolecular interactions and add to the already impressive number of catalytic and structural functions of zinc in an estimated three thousand human zinc proteins. The effects of zinc on redox biology have adduced evidence that zinc is an antioxidant. Without further qualifications, this notion is misleading and prevents a true understanding of the roles of zinc in biology. Its antioxidant-like effects are indirect and expressed only in certain conditions because a lack of zinc and too much zinc have pro-oxidant effects. Teasing apart these functions based on quantitative considerations of homeostatic control of cellular zinc is critical because opposite consequences are observed depending on the concentrations of zinc: pro- or anti-apoptotic, pro- or anti-inflammatory and cytoprotective or cytotoxic. The article provides a biochemical basis for the links between redox and zinc biology and discusses why zinc has pleiotropic functions. Perturbation of zinc metabolism is a consequence of conditions of redox stress. Zinc deficiency, either nutritional or conditioned, and cellular zinc overload cause oxidative stress. Thus, there is causation in the relationship between zinc metabolism and the many diseases associated with oxidative stress.

The role of C2H2 zinc finger proteins in plant responses to abiotic stresses

Abiotic stresses are important factors affecting plant growth and development and limiting agricultural production worldwide. Plants have evolved complex regulatory mechanisms to respond and adapt to constantly changing environmental conditions. C2H2 zinc finger proteins form a relatively large family of transcriptional regulators in plants. Recent studies have revealed that C2H2 zinc finger proteins function as key transcriptional regulators in plant responses to a wide spectrum of stress conditions, including extreme temperatures, salinity, drought, oxidative stress, excessive light and silique shattering. Here, we summarize recent functional analysis on C2H2 zinc finger proteins in plant responses to abiotic stresses and discuss their roles as part of a large regulatory network in the perception and responses by plants to different environmental stimuli.

Targeting the Zinc Transporter ZIP7 in the Treatment of Insulin Resistance and Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a disease associated with dysfunctional metabolic processes that lead to abnormally high levels of blood glucose. Preceding the development of T2DM is insulin resistance (IR), a disorder associated with suppressed or delayed responses to insulin. The effects of this response are predominately mediated through aberrant cell signalling processes and compromised glucose uptake into peripheral tissue including adipose, liver and skeletal muscle. Moreover, a major factor considered to be the cause of IR is endoplasmic reticulum (ER) stress. This subcellular organelle plays a pivotal role in protein folding and processes that increase ER stress, leads to maladaptive responses that result in cell death. Recently, zinc and the proteins that transport this metal ion have been implicated in the ER stress response. Specifically, the ER-specific zinc transporter ZIP7, coined the "gate-keeper" of zinc release from the ER into the cytosol, was shown to be essential for maintaining ER homeostasis in intestinal epithelium and myeloid leukaemia cells. Moreover, ZIP7 controls essential cell signalling pathways similar to insulin and activates glucose uptake in skeletal muscle. Accordingly, ZIP7 may be essential for the control of ER localized zinc and mechanisms that disrupt this process may lead to ER-stress and contribute to IR. Accordingly, understanding the mechanisms of ZIP7 action in the context of IR may provide opportunities to develop novel therapeutic options to target this transporter in the treatment of IR and subsequent T2DM.

Sequential displacement strategy for selective and highly sensitive detection of Zn2+, Hg2+ and S2- ions: An approach toward a molecular keypad lock

A thiocarbonohydrazone locked salicylidene based macrocycle ligand L has been synthesized and its ion sensing properties were examined by UV-visible and fluorescence spectroscopy. The macrocycle serves as a highly selective colorimetric sensor for Hg²⁺ ions while it acts as an excellent fluorescent sensor for Zn²⁺ ions by exhibiting a green fluorescence at 498 nm even in the presence of interfering ions. A detailed analysis of binding characteristics such as complex stoichiometry, association constant and detection limits of L toward Hg²⁺ and Zn²⁺ ions were evaluated by UV-visible and fluorescence experiments which revealed a stronger binding affinity and higher detection limit of L toward the mercury ions. Further, the sequential displacement strategy for the chromofluorogenic detection of Zn²⁺, Hg²⁺ and S^2- ions by ligand L, has been studied comprehensively. Finally, the ion-responsive fluorescence output signal of L were employed to design a molecular keypad lock which could be accessible by two users having two different set of chemical passwords (inputs) through distinguishable optical trajectories.

ZnII Complexes for Bioimaging and Correlated Applications

Zinc is a biocompatible element that exists as the second most abundant transition metal ion and an indispensable trace element in the human body. Compared to traditional metal-organic complexes systems, d¹⁰ metal Zn^II complexes not only exhibit a large Stokes shift and good photon stability but also possess strong emission and low cytotoxicity with a relatively small molecular weight. The use of Zn^II complexes has emerged in the last decade as a versatile and convenient tool for numerous biological applications, including bioimaging, molecular and protein recognition, as well as photodynamic therapy. Herein, we review recent developments involving Zn^II metal complexes applied as specific subcellular compartment imaging probes and their correlated utilizations.

A coumarin based highly sensitive fluorescent chemosensor for selective detection of zinc ion

A very effective and highly sensitive fluorescent chemosensor, based on 4-hydroxycoumarin skeleton substituted by benzothiazole moiety was synthesized and investigated for the detection of zinc ion. This chemosensor displays highly selective and sensitive fluorescence enhancement to Zn²⁺ over other metal ions examined in solution and in biological systems. The detection limit for the fluorescent chemosensor 1 toward Zn²⁺ was 3.58 × 10^-8 M. A simple and efficient approach was improved for the synthesis of chemosensor 1 starting from 4-hydroxycoumarin.

Ultra-fast zinc ion detection in living cells and zebrafish by a light-up fluorescent probe

As the second most abundant transition metal after iron in biological systems, Zn²⁺ takes part in various fundamental life processes such as cellular metabolism and apoptosis, neurotransmission. Thus, the development of analytical methods for fast detection of Zn²⁺ in biology and medicine has been attracting much attention but still remains a huge challenge. In this report, we develop a novel Zn²⁺-specific light-up fluorescent probe based on intramolecular charge transfer combined with chelation enhanced fluorescence induced by structural transformation. Addition of Zn²⁺ in vitro can induce a remarkable color change from colorless to green and a strong fluorescence enhancement with a red shift of 43 nm. Moreover, the probe shows an extremely low detection limit of 13 nM and ultra-fast response time of less than 1 s. The Zn²⁺ sensing mechanism was fully supported by TDDFT calculations as well as HRMS and ¹H NMR titrations. The recognition of Zn²⁺ in living Hela cells as well as the MTT assay demonstrate that the probe can rapidly light-up detect Zn²⁺ in vivo with low cytotoxicity and good cell-permeability. Furthermore, the probe can also be successfully applied to bioimaging Zn²⁺ in living zebrafish.

Calixarene-based alkynyl-bridged gold(i) isocyanide and phosphine complexes as building motifs for the construction of chemosensors and supramolecular architectures

A calixarene-based alkynyl-bridged Au(i) isocyanide complex with a triazolyl group as a receptor site has been synthesized and demonstrated to be a selective chemosensor for Zn²⁺ based on Au(i)⋯Au(i) interactions.