Photochemical synthesis of N-adamantylhomoallylamines through addition of cyclic olefins to imines catalyzed by alumina grafted cadmium sulfide

Grafting cadmium sulfide onto alumina induces a small bandgap widening and a more significant lifetime variation of the light generated charge carriers from 0.76 microseconds measured for pristine CdS to 0.75, 0.86, and 1.20 microseconds found for CdS/Al(2)O(3) containing 30, 20, and 9% of CdS, respectively. The quasi-Fermi level of electrons of -0.42 V (NHE) is not significantly changed. These alumina grafted semiconductor photocatalysts enable the linear addition of cyclopentene, cyclohexene, and α-pinene to N-adamantylimines affording novel homoallyladamantylamines in isolated yields of 21-85% through a regioselective C-C heterocoupling of intermediate allyl and α-aminobenzyl radicals. As by-products hydrodimers of the imine are formed by C-C homocoupling of the benzylic radicals. Different from heterocoupling, the homocoupling is a stereospecific process directed by the nature of the olefin employed in the reaction.     

硫化镉纳米粒子对原核生物的毒理作用

硫化镉纳米粒子（cadmium sulfide nanoparticles,CdS NPs）是一种重要的半导体,具有突出的光电特性、可调带隙和化学稳定性,在分析化学、生物医学、荧光成像和生物传感器等方面具有潜在应用价值。生物合成CdS NPs具有可控、低成本、环境友好等优势而被广泛研究。然而CdS NPs本身兼具纳米材料毒性及重金属硫化物毒性,其对原核微生物的毒性研究受到广泛关注。本文以大肠杆菌为例,对CdS NPs在原核生物细胞内的毒性机理研究进展进行了综述,包括CdS NPs的生物合成机制、CdS NPs对大肠杆菌的毒害作用以及大肠杆菌对该毒害作用的防御机制,着重论述了细菌在合成CdS NPs过程中Cd²⁺及CdS对合成细菌本身的毒理作用及该细菌所产生的相应应激机制。本文旨在更好、更全面地评估CdS NPs的毒性,促进抗CdS NPs的原核生物在相关领域的发展和应用。     

Synthesis, thermal stability and photoluminescence of new cadmium sulfide/organic composite hollow sphere nanostructures

Novel cadmium sulfide/organic composite hollow spheres composed of sword-like nanorods were synthesized via a simple reaction between cadmium salts and thioglycolic acid (TGA) at room temperature. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SEAD) and Fourier transform infrared (FT-IR) spectra. Thermal stability of the organic composite was investigated. CdS/organic composite would decompose into pure wurtzite CdS through hydrothermal treatment. Effect of the cadmium source on the formation of the CdS/organic composite was investigated. Photoluminescence (PL) was used to study the optical properties of CdS/organic composite and pure CdS.     

Effect of CdS preparation on the photo-catalyzed decomposition of hydrogen sulfide in alkaline aqueous media

Band-gap irradiation of CdS dispersions in alkaline aqueous media (pH 14) containing 0.1 M Na₂S produces hydrogen and sulfur. The reaction is photo-decomposition of hydrogen sulfide by two quanta of visible light (λ > 400 nm). Various batches of commercially available cadmium sulfide, as well as CdS precipitated from nitrate, sulfate, and chloride solutions at neutral pH, produce different amounts of hydrogen. Electronically pure CdS (puratronic grade) generates almost no hydrogen. By contrast, CdS precipitates prepared in the presence of excess cadmium yield forty times more hydrogen than CdS prepared in the presence of excess sodium sulfide. Differences are rationalized in terms of possible surface modification and/or changes in the active sites by anions present as ‘impurities’ which could affect separation and recombination of the charge carries, e_CB⁻ and h_VB⁺, in CdS.     

Effect of nano cadmium sulfide on the electron transfer reactivity and peroxidase activity of hemoglobin

Hemoglobin (Hb) is immobilized with cadmium sulfide (CdS) nanoparticles (NPs) on pyrolytic graphite (PG) electrode to characterize the electrochemical reactivity and peroxidase activity of the protein. The result demonstrates that fine redox waves of Hb can be achieved after this protein is entrapped in CdS NPs. Meanwhile, the protein can exhibit nice catalytic activity towards hydrogen peroxide (H2O2). Linear relationship between the reductive peak current and the H2O2 concentration has been obtained from 5.0 x 10(-6) to 4.0 x 10(-4) mol/L, on the basis of which a new kind of H2O2 biosensor might be developed in the future.     

Conversion in the peptides coating cadmium:sulfide crystallites in Candida glabrata.

Cultures of Candida glabrata treated with CdCl2 form intracellular Cd(II) complexes that evolve with the time of culturing. Initially, glutathione (gamma ECG) appears to be the major buffering component. One type of Cd(II)-glutathione complex exists as a cadmium:sulfide (CdS) crystallite coated with glutathione. A time dependent change in the coating of the CdS particles occurs with a decrease in the (gamma ECG) content and a corresponding increase in the abundance of (gamma EC)nG peptides with (gamma EC)2G becoming the predominant peptide. The des-Gly variant (gamma EC)2 appears in significant concentration only in late cultures. The evolution in isopeptide coating appears to be dependent on the sulfide content of the CdS particles. Cellular conditions that enhance the generation of sulfide ions facilitate the conversion from gamma ECG to (gamma EC)2G.     

Augmented biosynthesis of cadmium sulfide nanoparticles by genetically engineered Escherichia coli

Microorganisms can complex and sequester heavy metals, rendering them promising living factories for nanoparticle production. Glutathione (GSH) is pivotal in cadmium sulfide (CdS) nanoparticle formation in yeasts and its synthesis necessitates two enzymes: γ‐glutamylcysteine synthetase (γ‐GCS) and glutathione synthetase (GS). Hereby, we constructed two recombinant E. coli ABLE C strains to over‐express either γ‐GCS or GS and found that γ‐GCS over‐expression resulted in inclusion body formation and impaired cell physiology, whereas GS over‐expression yielded abundant soluble proteins and barely impeded cell growth. Upon exposure of the recombinant cells to cadmium chloride and sodium sulfide, GS over‐expression augmented GSH synthesis and ameliorated CdS nanoparticles formation. The resultant CdS nanoparticles resembled those from the wild‐type cells in size (2–5 nm) and wurtzite structures, yet differed in dispersibility and elemental composition. The maximum particle yield attained in the recombinant E. coli was ≈2.5 times that attained in the wild‐type cells and considerably exceeded that achieved in yeasts. These data implicated the potential of genetic engineering approach to enhancing CdS nanoparticle biosynthesis in bacteria. Additionally, E. coli‐based biosynthesis offers a more energy‐efficient and eco‐friendly method as opposed to chemical processes requiring high temperature and toxic solvents. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

A new Klebsiella planticola strain (Cd-1) grows anaerobically at high cadmium concentrations and precipitates cadmium sulfide

Heavy metal resistance by bacteria is a topic of much importance to the bioremediation of contaminated soils and sediments. We report here the isolation of a highly cadmium-resistant Klebsiella planticola strain, Cd-1, from reducing salt marsh sediments. The strain grows in up to 15 mM CdCl(2) under a wide range of NaCl concentrations and at acidic or neutral pH. In growth medium amended with thiosulfate, it precipitated significant amounts of cadmium sulfide (CdS), as confirmed by x-absorption spectroscopy. In comparison with various other strains tested, Cd-1 is superior for precipitating CdS in cultures containing thiosulfate. Thus, our results suggest that Cd-1 is a good candidate for the accelerated bioremediation of systems contaminated by high levels of cadmium.     

R-phycoerythrin: a natural ligand for detoxifying cadmium ions and a tunnel matrix for synthesis of cadmium sulfide nanoparticles

As evidenced by ion-selective electrode potentiometry, the hexameric R-phycoerythrin (RPE) molecule binds 20-4000 cadmium ions (Cd2+) depending on Cd2+ concentration in the solution. Cadmium ions bound to RPE serve as nuclei of cadmium sulfide crystallization in the presence of sulfide ions. According to spectrometric, electron-microscopic and capillary electrophoresis data, the particles are heteroaggregates of 3.2 x 6 nm in size. The fact that the particle size fits the size of the central tunnel of the RPE molecule and the similarity between the electrophoretic patterns of free RPE and the RPE-CdS complex indicate that the tunnel space, limiting the crystal growth, is the most probable site of nanoparticle formation. Properties of the nanoparticles can be modified by changing temperature, pH, etc. It is concluded that RPE can be used as a reagent for detoxification of cadmium ions and a matrix for synthesis of elongated CdS nanoparticles.     

Euglena gracilis cadmium-binding protein-II contains sulfide ion

Sulfide ions are a constituent of the cadmium-binding protein-II in the alga Euglena gracilis. Their presence was demonstrated by the methylene blue assay, by acid labilization induced reductions in the Cd-S charge transfer band at 254 nm and by reactions with the thiol reagent, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). Direct reduction of DTNB by sulfide and precipitation of CdS yield a complex stoichiometry for the DTNB reaction. The S2-/Cd2+ ratios determined, 1.25 +/- 0.10 (methylene blue) and 1.37 +/- 0.16 (DTNB), are in good agreement.     

Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes

Klebsiella aerogenes forms electron-dense partieles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests that the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. acrogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electrondense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 M) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.Abbreviations EDXA Energy dispersive X-ray analysis - AAS Atomic absorption spectroscopy - TEM Transmission electron microscopy - SEM Scanning electron microscopy - ICP-MS Inductively coupled plasma mass spectrometry - ALSA Acid-labile sulfide analysis     

Studying the Structural,Morphological, Optical,and Electrical Properties of CdS/PbS Thin Films for Photovoltaic Applications

Plasmonics - The cadmium sulfide (CdS) and lead sulfide (PbS) materials have been chosen in order to boost solar energy conversion from ultraviolet region to the near-infrared (NIR) spectral...     

Biologically synthesized fluorescent CdS NPs encapsulated by PHB

Here an attempt was made to biologically synthesize fluorescent cadmium sulfide nanoparticles and to immobilize the synthesized nanoparticles in PHB nanoparticles. The present study uses Brevibacterium casei SRKP2 as a potential producer for the green synthesis of CdS nanoparticles. Biologically synthesized nanoparticles were characterized and confirmed using electron microscopy and XRD. The size distribution of the nanoparticles was found to be 10-30 nm followed by which the consequence of time, growth of the organism, pH, concentration of CdCl(2) and Na(2)S on the synthesis of nanoparticles were checked. Enhanced synthesis and fluorescence emission of CdS nanoparticles were achieved at pH 9. The synthesized CdS NPs were immobilized with PHB and were characterized. The fluorescent intensity of the CdS nanoparticles remained unaffected even after immobilization within PHB nanoparticles.     

Human sulfide:quinone oxidoreductase catalyzes the first step in hydrogen sulfide metabolism and produces a sulfane sulfur metabolite

Sulfide:quinone oxidoreductase (SQOR) is a membrane-bound enzyme that catalyzes the first step in the mitochondrial metabolism of H(2)S. Human SQOR is successfully expressed at low temperature in Escherichia coli by using an optimized synthetic gene and cold-adapted chaperonins. Recombinant SQOR contains noncovalently bound FAD and catalyzes the two-electron oxidation of H(2)S to S(0) (sulfane sulfur) using CoQ(1) as an electron acceptor. The prosthetic group is reduced upon anaerobic addition of H(2)S in a reaction that proceeds via a long-wavelength-absorbing intermediate (λ(max) = 673 nm). Cyanide, sulfite, or sulfide can act as the sulfane sulfur acceptor in reactions that (i) exhibit pH optima at 8.5, 7.5, or 7.0, respectively, and (ii) produce thiocyanate, thiosulfate, or a putative sulfur analogue of hydrogen peroxide (H(2)S(2)), respectively. Importantly, thiosulfate is a known intermediate in the oxidation of H(2)S by intact animals and the major product formed in glutathione-depleted cells or mitochondria. Oxidation of H(2)S by SQOR with sulfite as the sulfane sulfur acceptor is rapid and highly efficient at physiological pH (k(cat)/K(m,H(2)S) = 2.9 × 10(7) M(-1) s(-1)). A similar efficiency is observed with cyanide, a clearly artificial acceptor, at pH 8.5, whereas a 100-fold lower value is seen with sulfide as the acceptor at pH 7.0. The latter reaction is unlikely to occur in healthy individuals but may become significant under certain pathological conditions. We propose that sulfite is the physiological acceptor of the sulfane sulfur and that the SQOR reaction is the predominant source of the thiosulfate produced during H(2)S oxidation by mammalian tissues.     

Eukaryotic and prokaryotic contributions to colonic hydrogen sulfide synthesis

Hydrogen sulfide (H(2)S) is an important modulator of many aspects of digestive function, both in health and disease. Colonic tissue H(2)S synthesis increases markedly during injury and inflammation and appears to contribute to resolution. Some of the bacteria residing in the colon can also produce H(2)S. The extent to which bacterial H(2)S synthesis contributes to what is measured as colonic H(2)S synthesis is not clear. Using conventional and germ-free mice, we have delineated the eukaryotic vs. prokaryotic contributions to colonic H(2)S synthesis, both in healthy and colitic mice. Colonic tissue H(2)S production is entirely dependent on the presence of the cofactor pyridoxal 5'-phosphate (vitamin B(6)), while bacterial H(2)S synthesis appears to occur independent of this cofactor. As expected, approximately one-half of the H(2)S produced by feces is derived from eukaryotic cells. While colonic H(2)S synthesis is markedly increased when the tissue is inflamed, and, in proportion to the extent of inflammation, fecal H(2)S synthesis does not change and tissue granulocytes do not appear to be the source of the elevated H(2)S production. Rats fed a B vitamin-deficient diet for 6 wk exhibited significantly diminished colonic H(2)S synthesis, but fecal H(2)S synthesis was not different from that of rats on the control diet. Our results demonstrate that H(2)S production by colonic bacteria does not contribute significantly to what is measured as colonic tissue H(2)S production, using the acetate trapping assay system employed in this study.     

Aerobic sulfide production and cadmium precipitation by Escherichia coli expressing the Treponema denticola cysteine desulfhydrase gene

The cysteine desulfhydrase gene of Treponema denticola was over-expressed in Escherichia coli to produce sulfide under aerobic conditions and to precipitate metal sulfide complexes on the cell wall. When grown in a defined salts medium supplemented with cadmium and cysteine, E. coli producing cysteine desulfhydrase secreted sulfide and removed nearly all of the cadmium from solution after 48 h. A control strain produced significantly less sulfide and removed significantly less cadmium. Measurement of acid-labile sulfide and energy dispersive X-ray spectroscopy indicated that cadmium was precipitated as cadmium sulfide. Without supplemental cysteine, both the E. coli producing cysteine desulfhydrase and the control E. coli demonstrated minimal cadmium removal.     

Hydrogen sulfide induces direct radical-associated DNA damage

Hydrogen sulfide (H(2)S) is produced by indigenous sulfate-reducing bacteria in the large intestine and represents an environmental insult to the colonic epithelium. Clinical studies have linked the presence of either sulfate-reducing bacteria or H(2)S in the colon with chronic disorders such as ulcerative colitis and colorectal cancer, although at this point, the evidence is circumstantial and underlying mechanisms remain undefined. We showed previously that sulfide at concentrations similar to those found in the human colon induced genomic DNA damage in mammalian cells. The present study addressed the nature of the DNA damage by determining if sulfide is directly genotoxic or if genotoxicity requires cellular metabolism. We also questioned if sulfide genotoxicity is mediated by free radicals and if DNA base oxidation is involved. Naked nuclei from untreated Chinese hamster ovary cells were treated with sulfide; DNA damage was induced by concentrations as low as 1 micromol/L. This damage was effectively quenched by cotreatment with butylhydroxyanisole. Furthermore, sulfide treatment increased the number of oxidized bases recognized by formamidopyrimidine [fapy]-DNA glycosylase. These results confirm the genotoxicity of sulfide and strongly implicate that this genotoxicity is mediated by free radicals. These observations highlight the possible role of sulfide as an environmental insult that, given a predisposing genetic background, may lead to genomic instability or the cumulative mutations characteristic of colorectal cancer.     

CdS nanoparticles functionalized colloidal carbon particles: preparation, characterization and application for electrochemical detection of thrombin

A novel and simple method for preparing cadmium sulfide nanoparticles (CdS NPs) functionalized colloidal carbon particles (CPs) has been successfully developed by in situ growing abundant CdS NPs on the surfaces of monodisperse carbon particles (CdS/CPs). The obtained CdS/CPs conjugates as signal amplification labels were further used for the ultrasensitive determination of thrombin. The CdS/CPs conjugates were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible absorption spectrum (UV). The protein electrical detection involves a dual binding event, based on thrombin linked to the CdS/CPs tags and glass surface by the specific aptamer-protein affinity interactions and a succedent electrochemical stripping transduction. Owing to the high-content CdS NPs on carbon particles, this assay allowed a desirable detection limit of 6.0 × 10(-17)M, which was 1000 times lower than that of only using CdS NPs as labels in the control experiments. This protocol exhibited excellent selectivity against these common proteins such as bovine plasma albumin, lysozyme and hemoglobin. The signal amplification approach proposed here provides a facile, cost-effective method for the ultrasensitive determination of thrombin in the practical samples.     

Adaptation to Cadmium by Klebsiella aerogenes Growing in Continuous Culture Proceeds Mainly via Formation of Cadmium Sulfide

The adaptation of Klebsiella aerogenes to high levels of cadmium was studied in continuous culture under conditions of glucose limitation. When up to 6 × 10⁻⁴ M cadmium was added to a culture in steady state, growth ceased instantaneously but resumed within 5 h (dilution rate, 0.1 h⁻¹). When again in steady state, these adapted cells exhibited a far greater tolerance to cadmium than did unadapted cells (not previously exposed to cadmium) when tested on solid media containing different concentrations of cadmium. This relative insensitivity of adapted cells to cadmium was subsequently lost in continuous culture within 5 days after omitting cadmium from the influent medium. Thus, the phenomenon was an inducible physiological process. Adapted cells contained substantial amounts of cadmium (up to 2.4% of the bacterial dry weight). The cadmium content of the cells was dependent on growth conditions and was found to be proportional to the inorganic sulfide content of the cells in all cases. This suggested that formation of CdS is probably the most important mechanism of detoxification in this organism. The presence of large numbers of electron-dense granules on the cell surface (absent in cultures without added cadmium) provided additional support for this conclusion.     

Reactivity of hydrogen sulfide with peroxynitrite and other oxidants of biological interest

Hydrogen sulfide (H(2)S) is an endogenously generated gas that can also be administered exogenously. It modulates physiological functions and has reported cytoprotective effects. To evaluate a possible antioxidant role, we investigated the reactivity of hydrogen sulfide with several one- and two-electron oxidants. The rate constant of the direct reaction with peroxynitrite was (4.8±1.4)×10(3)M(-1) s(-1) (pH 7.4, 37°C). At low hydrogen sulfide concentrations, oxidation by peroxynitrite led to oxygen consumption, consistent with a one-electron oxidation that initiated a radical chain reaction. Accordingly, pulse radiolysis studies indicated that hydrogen sulfide reacted with nitrogen dioxide at (3.0±0.3)×10(6)M(-1) s(-1) at pH 6 and (1.2±0.1)×10(7)M(-1) s(-1) at pH 7.5 (25°C). The reactions of hydrogen sulfide with hydrogen peroxide, hypochlorite, and taurine chloramine had rate constants of 0.73±0.03, (8±3)×10(7), and 303±27M(-1) s(-1), respectively (pH 7.4, 37°C). The reactivity of hydrogen sulfide was compared to that of low-molecular-weight thiols such as cysteine and glutathione. Considering the low tissue concentrations of endogenous hydrogen sulfide, direct reactions with oxidants probably cannot completely account for its protective effects.