Investigating structural aspects to understand the putative/claimed non-toxicity of the Hg-based Ayurvedic drug Rasasindura using XAFS.

XANES- and EXAFS-based analysis of the Ayurvedic Hg-based nano-drug Rasasindura has been performed to seek evidence of its non-toxicity. Rasasindura is determined to be composed of single-phase α-HgS nanoparticles (size ∼24 nm), free of Hg(0) or organic molecules; its structure is determined to be robust (<3% defects). The non-existence of Hg(0) implies the absence of Hg-based toxicity and establishes that chemical form, rather than content of heavy metals, is the correct parameter for evaluating the toxicity in these drugs. The stable α-HgS form (strong Hg-S covalent bond and robust particle character) ensures the integrity of the drug during delivery and prevention of its reduction to Hg(0) within the human body. Further, these comparative studies establish that structural parameters (size dispersion, coordination configuration) are better controlled in Rasasindura. This places the Ayurvedic synthesis method on par with contemporary techniques of nanoparticle synthesis.

In vivo monitoring of organ-selective distribution of CdHgTe/SiO2 nanoparticles in mouse model.

CdHgTe/SiO(2) nanoparticles were prepared by SiO(2) capping on the surface of CdHgTe QDs. The characteristics, such as optical spectra, photostability, size and cell toxicity were investigated. The dynamic distribution of CdHgTe/SiO(2) nanoparticles was in vivo monitored by near infrared fluorescence imaging system. CdHgTe/SiO(2) nanoparticles acted as a novel fluorescence probe have a maximum fluorescence emission of 785 nm and high photo-stability. The hydrodynamic diameter of CdHgTe/SiO(2) nanoparticles could be adjusted to 122.3 nm. Compared to CdHgTe QDs, inhibitory effects of CdHgTe/SiO(2) nanoparticles on proliferation of HCT116 cells decreased to a certain extent. CdHgTe/SiO(2) nanoparticles had their specific dynamic distribution behavior, which provided new perspectives for bio-distribution of nanoparticles.

Synthesis and characterization of a new metal-organic NLO material: dibromo bis(triphenylphosphine oxide) mercury(II).

A new metal-organic nonlinear optical dibromo bis(triphenylphosphine oxide) mercury(II) (HgBr(2)(TPPO)(2), TPPO=triphenylphosphine oxide) crystal has been synthesized. Single-crystal X-ray diffraction reveals that HgBr(2)(TPPO)(2) crystallizes in the orthorhombic system, space group Pna2(1), a=21.174A, b=9.1979A, c=17.468A, and Z=4. The crystal was also characterized by FTIR spectroscopy, differential scanning calorimetry (DSC), thermal gravity analysis (TGA), and UV-vis-IR spectroscopy. Thermal analyses confirmed that the crystal is stable up to 151 degrees C. The transmission spectrum of the crystal shows that the lower cut off wavelength lies at 340nm. The nonlinear optical (NLO) property of HgBr(2)(TPPO)(2) has been estimated by Kurtz-powder second harmonic generation (SHG) test.

Chiral ß-HgS quantum dots: Aqueous synthesis, optical properties and cytocompatibility.

ß-HgS quantum dots (QDs) have drawn enormous attention due to the size-tunable bandgap and the lowest quantum state in conduction band which have been applied to semiconductor transistor and photodetector. Though ß-HgS is the essential component of Tibetan medicine, the potential toxicity of ß-HgS limits its applications, especially in bio-application. Herein, chiral biomolecule enantiomers N-isobutyryl-L(D)-cysteine (L(D)-NIBC) and L(D)-cysteine (L(D)-Cys) were introduced into HgCl2 and Na2S aqueous solution to synthesize chiral ß-HgS QDs in one-pot, which significantly improved their water-solubility and cytocompatibility. Notably, all chiral ß-HgS QDs showed none cytotoxicity even at high concentration (20 mg·L-1), and the cytocompatibility of D-ß-HgS QDs was better than corresponding L-ß-HgS QDs at the concentration of 20 mg·L-1. This cytotoxicity discrimination was associated with the chirality inversion of chiral ß-HgS QDs compared with the corresponding chiral ligands. In-situ real-time circular dichroism (CD) monitoring indicated that the chirality of ß-HgS QDs originated from the asymmetrical arrangement of chiral ligands on the achiral core surface. Their chiroptical activity, near-infrared optical absorption (800 nm), fluorescence emission (900-1000 nm), high-performance photothermal conversion and good cytocompatibility, implied chiral ß-HgS QDs could be used as a candidate material for photothermal therapy or a near-infrared fluorescent probe in organism, which brings a novel insight for bio-application of ß-HgS QDs.

A ditopic colorimetric sensor for fluoride ion based on thiourea mercury complex.

A novel ditopic chromogenic receptor, N-5-(8-hydroxy)quinoline-N'-4'-nitro-phenyl thiourea (1), was synthesized. The metal complex 1-Hg(2+) showed sensitive and highly selective responses to F(-) over other anions such as CH(3)CO(2)(-), H(2)PO(4)(-), HSO(4)(-) and Cl(-). 1-Hg(2+)-F(-) complex formed, which promoted the intramolecular charge transfer and led to a dramatic spectral change. The color of 1-Hg(2+) solution changed from colorless to red upon addition of F(-). Thus, a colorimetric assay of F(-) was developed in acetonitrile by naked-eye detection. F(-) behaved linearly in the 8.0 x 10(-6) to 2.0 x 10(-5) mol L(-1) concentration range with LOD as 1.4 x 10(-6) mol L(-1).

Identification of Microalgae by Laser Desorption/Ionization Mass Spectrometry Coupled with Multiple Nanomatrices.

In this study, we demonstrate a simple method to identify microalgae by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using three different substrates: HgSe, HgTe, and HgTeSe nanostructures. The fragmentation/ionization processes of complex molecules in algae varied according to the heat absorption and transfer efficiency of the nanostructured matrices (NMs). Therefore, the mass spectra obtained for microalgae showed different patterns of m/z values for different NMs. The spectra contained both significant and nonsignificant peaks. Constructing a Venn diagram with the significant peaks obtained for algae when using HgSe, HgTe, and HgTeSe NMs in m/z ratio range 100-1000, a unique relationship among the three sets of values was obtained. This unique relationship of sets is different for each species of microalgae. Therefore, by observing the particular relationship of sets, we successfully identified different algae such as Isochrysis galbana, Emiliania huxleyi, Thalassiosira weissflogii, Nannochloris sp., Skeletonema cf. costatum, and Tetraselmis chui. This simple and cost-effective SALDI-MS analysis method coupled with multi-nanomaterials as substrates may be extended to identify other microalgae and microorganisms in real samples. Graphical Abstract Identification of microalgae by surface-assisted laser desorption/ionization mass spectrometry coupled with three different mercury-based nanosubstrates.

Synthesis and Cell Imaging of a Near-Infrared Fluorescent Magnetic "CdHgTe-Dextran-Magnetic Layered Double Hydroxide-Fluorouracil" Composite.

In this article, a water-soluble near-infrared quantum dots of CdHgTe were prepared and subsequently combined with the drug delivery system "dextran-magnetic layered double hydroxide-fluorouracil" (DMF) to build a new nanostructure platform in form of CdHgTe@DMF, in which the fluorescent probe function of quantum dots and the magnetic targeting transport and slow-release curative effect of DMF were blended availably together. The luminescent property particle size, and internal structure of the composite were characterized using fluorescence spectrophotometer, ultraviolet spectrophotometer, laser particle size distribution, TEM, X-ray diffraction, and Fourier transform infrared. The experimental study on fluorescent tags effect and magnetic targeting performance of the multifunctional platform were performed by fluorescent confocal imaging. The results showed that the CdHgTe could be grafted successfully onto the surface of DMF by electrostatic coupling. The CdHgTe@DMF composite showed super-paramagnetic and photoluminescence property in the near-infrared wavelength range of 575-780 nm. Compared with CdHgTe, the CdHgTe@DMF composite could significantly improve the cell imaging effect, the label intensity increased with the magnetic field intensity, and obeyed the linear relationship Dmean = 1.758 + 0.0075M under the conditions of magnetic field interference. It can be implied that the CdHgTe@DMF may be an effective multifunction tool applying to optical bioimaging and magnetic targeted therapy.

Photochemical reactions of divalent mercury with thioglycolic acid: formation of mercuric sulfide particles.

Mercury (Hg) is a key toxic global pollutant. Studies in aquatic environment have suggested that thiols could be important for mercury speciation. Thioglycolic acid has been detected in various natural water systems and used as a model compound to study the complicated interaction between mercury and polyfunctional dissolved organic matter (DOM). We herein presented the first evidence for mercury particle formation during kinetic and product studies on the photochemistry of divalent mercury (Hg(2+)) with thioglycolic acid at near environmental conditions. Mercuric sulfide (HgS) particles formed upon photolysis were identified by high-resolution transmission electron microscopy coupled with energy dispersive spectrometry and select area electron diffraction. Kinetic data were obtained using UV-visible spectrophotometry and cold vapour atomic fluorescent spectrometry. The apparent first-order reaction rate constant under our experimental conditions was calculated to be (2.3±0.4)×10(-5) s(-1) at T=296±2 K and pH 4.0. It was found that (89±3)% of the reactants undergo photoreduction to generate elemental mercury (Hg(0)). The effects of ionic strengths, pH and potassium ion were also investigated. The formation of HgS particles pointed to the possible involvement of heterogeneous processes. Our kinetic results indicated the importance of weak binding sites on DOM to Hg in photoreduction of Hg(2+) to Hg(0). The potential implications of our data on environmental mercury transformation were discussed.

Synthesis, spectroscopic and magnetic resonance studies of mercury (II) and methylmercury (II) complexes of azathioprine, a biologically active mercaptopurine derivative.

Synthetic and spectroscopic studies of the Hg(II) and MeHg(II) complexes of azathioprine (AZA), a biologically active 6-mercaptopurine derivative, were undertaken. The altered coordination behavior of AZA with respect to the parent mercaptopurine, with sulfur no longer being the primary donor atom, was confirmed. As concluded by the 1H NMR, 13C NMR, and IR spectroscopic data, Hg(II) binds to the N(9) position of deprotonated AZA, while in the MeHg(II) compound, coordination occurs through the N(3) and N(9) positions of the purine ring. The values of the coupling constants 2J (199Hg-1H), 1J(199Hg-13C) for the MeHg(II) compound further support complexation via nitrogen atoms of the purine. Elemental analyses confirmed the compounds to be Hg(AZA)2 (1) and [(MeHg)2(AZA)](NO3) (2); conductivity measurement values show that 1 is a nonelectrolyte and 2 is a 1:1 electrolyte. Furthermore, the FAB-MS of the compounds confirms direct binding of the metal to the ligand, and in the case of the MeHg(II) compound, the successive loss of one and two MeHg(II) moieties can be clearly observed.

Vibrational studies of the solid imidazole and pyridine adducts of metal(II) saccharinates. III. Zn(II) and Hg(II) imidazole saccharinates.

Adducts of bis(o-sulfobenzimidato)zinc(II) and mercury(II) with imidazole are synthesized for the first time and their mid-infrared vibrational spectra at ambient conditions and at 77 K are coupled with the earlier spectra-structural inferences to predict aspects of the respective solid-state structures. The spectrum of the H2O-matrix isolated OD fundamentals in the hydrated zinc compound is also investigated. The structure of the latter adduct contrasts the octahedral isostructural tetrad of mixed imidazole-saccharinates [M(H2O)2(C3H4N2)4](C7H4NO3S)2 [M = Mn(II), Fe(II), Co(II) and Ni(II)] in that it bears only a single crystallographic type of hydrogen bonded C2v water molecules and at least two structurally different o-sulfobenzimidate ligands, some of them likely utilized in a bridging fashion. The rotation and the partial ionic character of a pair of N-monodentate o-sulfobenzimidato ligands placed about 212-214 pm from the metal accommodates another pair of imidazole molecules in the tetrahedral arrangement around the metal in the neutral unhydrous mercury complex.

Synthesis of polymer-bound 6-mercuric carboxylate DOPA precursors and solid phase labelling method of 6-radioiodinated L-DOPA.

In order to avoid separating unreacted mercury precursor and other mercury-containing compounds after the halodemercuration of a 6-mercury DOPA precursor, we developed a polymer-bound mercury precursor for the preparation of 6-halogenated DOPA. In this study, polymer-bound 6-mercuric carboxylate DOPA derivatives were synthesized from ion-exchange resin and Merrifield-type resin. Iododemercuration of polymer-bound 6-mercuric carboxylate DOPA derivatives gave higher yields (49-54%) compared with monomeric 6-mercuric trifluoroacetate protected DOPA. The radioiodination of the resin with no-carrier added iodine-125 afforded protected 6-[125I]I-L-DOPA with labelling efficiency of 92-97% with both polymer-bound 6-mercuric carboxylate DOPA derivatives.

Aqueous synthesis and characterization of glutathione-stabilized ß-HgS nanocrystals with near-infrared photoluminescence.

A simple, rapid and green aqueous approach to near-infrared (NIR)-emitting ß-HgS nanocrystals (NCs) was demonstrated for the first time by using glutathione (GSH) as the stabilizer at room temperature. The resulting HgS NCs with zinc blend structure exhibited strong quantum size effect, and the emission peak could be tuned in a wide NIR region from ca. 775 to 1041 nm. As compared with early achievements, the emission intensity of GSH-stabilized HgS NCs enhanced, with the maximum quantum yield reaching ~2.8%. It was also found that the stability of the GSH-HgS NCs was improved noticeably, the PL peak red-shifting only 9 nm and 23 nm after stored at 4°C for 4 months and 25°C for 7 days, respectively. The better stability of the HgS NCs was elucidated by FT-IR due to the multiple coordination of GSH molecule to surface Hg of the NCs. The emission range of GSH-stabilized HgS NCs was located between the visible region (500-800 nm) and IR region (1000-1600 nm) of HgS NCs as reported previously, extending the emission region of HgS nanomaterial. Therefore, the continuous emission from visible to IR spectral ranges provided HgS material more potential applications.

Synthesis and characterization of self-assembled CdHgTe/gelatin nanospheres as stable near infrared fluorescent probes in vivo.

This work presented a kind of novel near infrared emitting CdHgTe/gelatin nanospheres which were synthesized with Cd(NO(3))(2), Hg(NO(3))(2), NaHTe and a thiol stabilizer in gelatin solution. The self-assembled nanospheres were megranate-like and nearly 40 nm in diameter, with CdHgTe QDs uniformly embedded in gelatin matrix. They exhibited strong fluorescence ranging from 580 to 800 nm that could be tuned by molar ratios of Hg(2+) and gelatin. The full widths at half-maximum of the emission spectra were in the range of 60-80 nm. Compared with bare CdHgTe QDs, the photostability of this compact complex nanostructure remarkably improved. Moreover, the fluorescence of CdHgTe/gelatin nanospheres was much more resistant to the interference from certain kinds of endogenous biomolecules such as HSA, transferrin and hemoglobin. Further applications of living cells and mouse imaging were demonstrated with an in vivo near infrared fluorescence imaging system. The inherent advantages of high stability as well as high fluorescence intensity make the nanospheres particular interested NIR bioprobe candidates for in vivo imaging studies.

Zinc, cadmium, and mercury 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds.

Mononuclear Zn, Cd, and Hg 1,2-benzenedithiolates with intramolecular NH...S hydrogen bonds, [M(II){1,2-S2-3,6-(RCONH)2C6H2}2](2-) (R = CH 3, t-Bu; M = Zn, Cd, Hg), were synthesized and characterized by X-ray analysis and spectral measurements. The presence of intramolecular NH...S hydrogen bonds was established by the IR spectra. (199)Hg and (113)Cd nuclear magnetic resonance showed a stabilized four-thiolate coordinated structure and suggested the influence of the NH...S hydrogen bonds to ppi(Hg)-ppi(S) interactions. The NH stretching bands show that the NH...S hydrogen bonds in Cd and Hg complexes are stronger than those in the corresponding Zn complex. These results are supported by theoretical calculations. The experimental and theoretical results suggested that the NH...S hydrogen bond influences the efficient capture of toxic Cd and Hg ions by metallothioneins.

Effects of relative humidity and CO(g) on the O3-initiated oxidation reaction of Hg0(g): kinetic & product studies.

Ozone is assumed to be the predominant tropospheric oxidant of gaseous elemental mercury (Hg0(g)), defining mercury global atmospheric lifetime. In this study we have examined the effects of two atmospherically relevant polar compounds, H2O(g) and CO(g), on the absolute rate coefficient of the O3-initiated oxidation of Hg0(g), at 296 +/- 2 K using gas chromatography coupled to mass spectrometry (GC-MS). In CO-added experiments, we observed a significant increase in the reaction rate that could be explained by pure gas-phase chemistry. In contrast, we found the apparent rate constant, k(net), varied with the surface-to-volume ratio (0.6 to 5.5 L flasks) in water-added experiments. We have observed small increases in k(net) for nonzero relative humidity, RH < 100%, but substantial increase at RH > or = 100%. Product studies were performed using mass spectrometry and high resolution transmission electron microscopy coupled to an electron dispersive spectrometer (HRTEM-EDS). Our results give evidence for enhanced chain growth of HgO(s) on a carbon grid at RH = 50%. A water/surface/ozone independent ozone oxidation rate is estimated to be (6.2 +/- (1.1; tsigma/ radicaln) x 10(-19) cm3 molecule(-1) s(-1). The total uncertainty associated with the ensemble of experiments amount to approximately < or = 20%. The atmospheric implications of our results and the effect of an added reaction partner in homogeneous and heterogeneous atmospheric chemistry will be discussed.

Self-assembly using dynamic coordination chemistry and hydrogen bonding: mercury(II) macrocycles, polymers and sheets.

The self-assembly of extended metal-containing arrays is described based on dynamic coordination chemistry at mercury(II) with bis(amidopyridyl) ligands to form macrocycles, polymers, or sheets which can be further organized by hydrogen bonding between amide substituents. The ligands 1,2-C6H4[NHC(O)-4-C5H4N]2, 1, 1,2-C(6)H(4)[C(O)NHCH(2)-4-C(5)H(4)N](2), 2, and 1,2-C(6)H(4)[CH(2)C(O)NHCH(2)-4-C(5)H(4)N]2, 3 can adopt polar conformations and so can confer helicity in their complexes. Several macrocycles of formula [(HgX(2))(2)(micro-LL)(2)] (LL = 1, 2), with tetrahedral mercury(II) centers, were prepared in which individual molecules are further self-assembled via hydrogen bonding in the solid state to form one- or two-dimensional polymers or sheets. In one case, a one-dimensional polymer [((HgX2)-(mu-3))n] was formed. It is shown that the mercury(II) centers can be six-coordinate in forming the sheet structure [((HgX2)(mu-2)2)n], in which there are particularly large pores.