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.

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.

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 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.

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).

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.

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.

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.