Inductively Coupled Plasma Optical Emission Spectrophotometry Research Articles

Metal variability of the shrimp Palaemon elegans across coastal zones: anthropogenic and geological impacts.

This study focused on 120 specimens of the shrimp Palaemon elegans collected in intertidal zones in eight selected areas. This study aimed to assess the suitability of P. elegans as a bioindicator of natural and anthropogenic marine pollution. Metal concentrations of aluminum (Al), cadmium (Cd), copper (Cu), iron (Fe), lead (Pb), and zinc (Zn) were measured in shrimp collected from various sites in the Canary Islands, including areas affected by volcanic activity, industrial activity, and control zones. The determination of metal concentrations was conducted using inductively coupled plasma optical emission spectrophotometry (ICP-OES). The results showed significant differences in metal concentrations across the studied sites, with the highest levels of Al, Cu, Fe, Pb, and Zn observed in areas impacted by the Tajogaite volcanic eruption and harbor activity. Sites near old landfills and sewage pipes also exhibited elevated levels of Cd, Cu, and Pb, indicating strong anthropogenic influence. Al was found in the highest concentration in Harbour, reaching 25.7 ± 6.2mg/kg, while the lowest concentration was observed in Control Lp at 11.5 ± 0.69mg/kg. Conversely, lower metal concentrations were detected in control zones and areas with high dinoflagellate presence, suggesting a potential role of bioremediation by marine phytoplankton. The ability of P. elegans to accumulate metals in its tissues, particularly in areas of high pollution, highlights its potential as a bioindicator species. This study underscores the importance of P. elegans in monitoring marine pollution and provides insights into the environmental impact of both natural and human-induced contamination on coastal ecosystems.

Metal variability in small pelagic fish Scomber colias as influenced by volcanic events in the Canary Islands.

Offshore volcanic activity occurs when an underwater volcano erupts. These volcanoes can be located underwater or on land and can be very dangerous to marine life. The aim of this study is to examine whether the influence of two volcanoes has an effect on the concentrations of metals and trace elements in the Atlantic mackerel Scomber colias in the Canary Islands. For the study, ten specimens of S. colias were obtained from each sampling area in March 2022. Metal concentrations were determined by inductively coupled plasma optical emission spectrophotometry (ICP-OES). The specimens of Scomber colias from the area affected by the Tajogaite volcano (La Palma) showed higher concentrations of all metals and trace elements analyzed than those from the other study areas. The specimens from the area of influence of the Tagoro Volcano (El Hierro) showed the second highest concentration of the elements studied, although this volcanic process is in a state of degassing.

Antimicrobial and Cytotoxic Effect of Positively Charged Nanosilver-Coated Silk Sutures.

Sutures are a crucial component of surgical procedures, serving to close and stabilize wound margins to promote healing. However, microbial contamination of sutures can increase the risk of surgical site infections (SSI) due to colonization by pathogens. This study aimed to tackle SSI by synthesizing positively charged silver nanoparticles (P-AgNPs) and using them to produce antimicrobial sutures. The P-AgNPs were reduced and stabilized using polyethylenimine (PEI), a cationic branched polymer. The physiochemical characteristics of P-AgNPs were confirmed from the surface plasmon resonance (SPR) peak at 419 nm, spherical morphology with a particle size range of 8-10 nm, PEI functional groups on NPs, a hydrodynamic diameter of 12.3 ± 2.4 nm, and a zeta potential of 31.3 ± 6 mV. Subsequently, the surfaces of silk sutures were impregnated with P-AgNPs at different time intervals (24, 48, and 96 h) using an ex situ method. Scanning electron microscopy (SEM) and tensile strength studies were conducted to determine the coating and durability of the NP-coated sutures. The NPs were quantified on sutures using inductively coupled plasma optical emission spectrophotometry (ICP-OES), which was in the range of 1-5 μg. Primarily, antimicrobial activity was studied using three microorganisms (Candida albicans, Streptococcus mutans, and Staphylococcus aureus) for both P-AgNPs and suture-coated P-AgNPs using the agar diffusion method. The results showed that only the NPs and NP-coated sutures exhibited enhanced antimicrobial effects against bacteria and fungi. Finally, the cytotoxicity of the sutures was investigated using stem cells from the apical papilla (SCAPs) for 24 h, which exhibited more than 75% cell viability. Overall, the results indicate that NP-coated sutures can potentially be used as antimicrobial sutures to diminish or inhibit SSI in postoperative or general surgery patients.

The size of iron oxide nanoparticles determines their translocation and effects on iron and mineral nutrition of pumpkin (Cucurbita maxima L.)

The ability of nanoparticles (NPs) to migrate in the plant body is an important issue to ensure that the NPs reach the desired tissue and to be able to select the most efficient NPs for agricultural applications. In this study, the size impact of four different iron oxide NPs (8–10, 18–20, 20–40, and 30–50 nm referred as NP10, NP20, NP30, and NP40, respectively) on their translocation in pumpkin was elucidated. To assess the root-to-shoot translocation, phloem sap was examined under transmission electron microscope (TEM). In addition, vibrating sample magnetometer (VSM) and inductively coupled plasma optical emission spectrophotometry (ICP-OES) analyses of stem and leaf tissues were performed to confirm size-dependent translocation. TEM and VSM analyses verified root-to-stem translocation of all tested NPs. The NPs treatment significantly altered the abundances of Mn, Cu, K, P, Al, Mg, and Na in tissues. The iron (Fe) content was abundant in plants treated with NP30 and NP20, and the lowest in plants treated with NP10 and NP40. Together with, only NP30 was found to be significantly translocated to the leaves, where it was 393 mg/kg in DW, about 2.3 times that of control. These findings pointed out the size-dependent translocation of NPs. It seems that biological barriers in the vascular bundle appear to restrict the migration, especially for NPs with an average size of 40 nm and above in pumpkins. These findings are important for selecting the most suitable size of iron oxide NPs for use in agricultural practices.

Pharmaceutical standardization and physicochemical characterization of traditional ayurvedic mineral drug red ochre roasted in cow‘s ghee (Shuddha Gairik)

Rasashastra is a pharmaceutics branch of Ayurveda describing scientific methods to convert metals and minerals into bio-compatible formulations that are used individually or plant admixed to enhance their bioavailability and efficacy. In the present study, red ochre (Gairik) powder was processed in cow’s ghee by textual method of roasting. The steps of preparation and changes in the properties therein were documented and validated in triplicate batches to develop a monograph. Ayurvedic and basic tests were performed to determine the properties of Shuddha Gairik. The physical characterization included Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infra-red (FT-IR), Dynamic Light Scattering (DLS) and Thermo-gravimetric Analysis (TGA). Elemental composition was estimated by titration and gravimetric analysis while heavy metal limits were assessed using Inductively Coupled Plasma Optical Emission Spectrophotometry (ICPOES). This study depicted that crude red ochre, containing Kaolinite with high iron percentage, on roasting in cow’s ghee led to the formation of fatty acids adsorbed red ochre particles. The developed monograph will be a guideline to the Ayurvedic industry for precise formulation of Shuddha Gairik. This will help researchers for better understanding the importance of Ayurvedic methods of pharmaceutical preparations and carry out their mechanistic studies in various diseases.

Utilization of PCB-contaminated Hudson River sediment by thermal processing and phytoremediation

The need to dispose of dredged sediments and development of appropriate technology for their safe utilization has become a growing problem in recent years. It has been proposed that dredged, fresh sediments can be utilized in agriculture or environment; however there is also growing interest in the use of thermally-treated sediments. Hence, the aim of this study was threefold: 1) to evaluate the effect of two incineration temperatures (300 °C and 600 °C) on the chemical and ecotoxicological properties of sediment; 2) select the appropriate treatment for further phytoremediation experiments with zucchini; and 3) assess the impact of sediment admixture on the physico-chemical parameters of soil, based on the responses of Aliivibrio fischeri and growth of zucchini (Cucurbita pepo L. cv ‘Black Beauty’). A range of chemical (inductively-coupled plasma optical emission spectrophotometry for macro- and trace elements; gas chromatography for polychlorinated biphenyls (PCBs)), ecotoxicological (Microtox assay), and plant morphology (biomass measurement) as well as physiological analyses (spectrophotometry for chlorophyll) were applied. River sediments incinerated at 600 °C resulted in better chemical and ecotoxicological properties than incinerated at 300 °C or no incinerated. Incineration at 600 °C removed PCBs from sediment. In culture experiments conducted with zucchini, sediment treated at 300 °C demonstrated a 51–81% reduction in PCB concentrations compared to untreated sediment. After four weeks of growth, the raw sediment showed a significant increase in K, Fe, Cr, Pb, Zn concentrations, whereas the thermally-processed sediment showed a decrease in Ca, Na, P, Cd, Cu, Ni, and Zn concentrations. Both the fresh and thermally-treated sediment types influenced plant growth positively: they demonstrated higher biomass production than plants grown in control soil; however, plants grown on soil with thermally-processed sediment demonstrated lower biomass than those grown in raw sediment. Chlorophyll content was affected negatively by admixtures of soil with treated or untreated sediment, while a lower chlorophyll a/b ratio was observed in plants grown on an admixture of thermally-treated sediment with soil. Our findings suggest that the use of sediments as a growth medium component may be a promising way for their utilization and transformation from waste material to a valuable resource enhancing the benefits to the environment.

PENGARUH LARUTAN EKSTRAK DAUN SIRIH (Piper betle L.) 50% TERHADAP PELEPASAN ION METAL (Ni, Cr dan Fe) PADA BREKET ORTODONTIK

Background: Orthodontic bracket is one of the components in a fixed orthodontic treatment. The influence of the oral cavity of an orthodontic bracket is a type IV hypersensitivity reaction due to corrosion on the bracket. The solution of extracts of betel leaf (Piper betle L.) of 50% which could affect corrosion. This study aimed to know the effect of betel leaf extract solution (piper betle L.) 50% against metal ion release.Method: The research method was “The Post Test Control Group Desain”, consists of four large groups respectively soaked with 6 units of brackets, consisting of a solution of betel leaf extract (piper betle L.) 50% (treatment), aquabidest (negative control), artificial saliva (negative control) and Naf (positive control) incubated for 7 days with a temperature of 370 C. Then ion measurement using the tool inductively coupled plasma – optical emission spectrophotometry (ICP-OES).Results: this study showed that the average release of ion the largest was on the solution of betel leaf extract (0.157167) then aquabides (0.086967), artificial saliva (0,08833) and sodium flouride (0.005533). Test results of Mann-Withney showed the presence of significant difference (p<0.05) release of ion Ni, Cr and Fe on four groups except among artificial saliva groups and sodium fluoride but the group that was soaked in a solution of betel leaf extract (piper betle L.) 50% occured a release of ion Ni, Cr and Fe higher. This is because the samples werestored in solution of betel leaf extract (Piper betle L.) of 50% which is a liquid electrolyte that can cause ion release.Conclusion: Betel leaf extract (piper betle L.) 50% is not effective to be used as an alternative to slow corrosive to metal ion (Ni, Cr and Fe) on a metal bracket.

Thermodynamic properties of phosphate members of the meta-autunite group: A high-temperature calorimetric study

Samples of synthetic analogs of uranyl phosphate minerals have been prepared at room temperature by slow mixing of reactants by a diffusion method. Reaction products were analyzed using powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), inductively coupled plasma optical emission spectrophotometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICP-MS). Calorimetric measurements have been performed in a Calvet-type twin calorimeter using sodium molybdate (3Na2O-4MoO3) solvent at 976K as a flux. The enthalpy of formation from the binary oxides, ΔHf-ox, at 298K was calculated for each compound from the respective drop solution enthalpies, ΔHds. Calculated standard enthalpies of formation from the elements, ΔH0f, at 298K are −3425±9kJ/mol for meta-ankoleite (KUP), −6233±17kJ/mol for meta-autunite (CaUP), −6921±13kJ/mol for meta-torbernite (CuUP), −7254±17kJ/mol for meta-saléeite (MgUP), −3264±12kJ/mol for Rb-meta-autunite (RbUP), −3580±7kJ/mol for meta-natro-autunite (NaUP), −3692±11kJ/mol for Li-meta-autunite (LiUP), −6402±5kJ/mol for meta-uranocircite (BaUP), −3277±6kJ/mol for Cs-meta-autunite (CsUP), and −7109±19kJ/mol for Co-meta-autunite (CoUP). The results exhibit trends of the thermodynamic stability of these compounds. The normalized charge deficiency per anion (NCDA) approach relates the thermodynamic stability of these compounds to their crystal structures. The thermodynamic stability of uranyl phosphate minerals is important for understanding their formation in Nature, as well as their fate in a geological repository for nuclear waste, and their existence in the subsurface of anthropogenically contaminated environments.

Chemical analysis of resin fraction of Nigerian bitumen for organic and trace metal compositions

ABSTRACTStudies of organics and trace metals of the resin fraction of Nigerian bitumen were carried out with an opinion to establish the environmental consequences of the fossil fuel and as well as characterize them. Bitumen samples were extracted from oil sands via Soxhlet extraction procedure using toluene as the extracting solvent. The bitumen samples were deasphaltened to obtain maltene by dissolving the samples in n-pentane (1:40). Column chromatography was used to fractionate the maltene into its components (saturates, aromatics, and resin) using silica gel as adsorbent and dissimilar solvents of varying polarity (n-hexane for saturates, toluene for aromatics, and methanol for resins). The organic compounds of the resin fraction were examined using Fourier Transform Infrared Spectrophometry (FTIR) and the elemental concentrations were determined using Inductively Coupled Plasma Optical Emission Spectrophotometry (ICP-OES). The infrared spectra of all the resin samples presented distinctive bands including expected polar functional groups which confirmed that the resin was cleanly eluted from the bitumen samples. The concentrations of the analyzed trace metals in the resin fraction were found to be high compared to other fractions and this was confirmed by their T-test values. Fe had the highest average concentration of 34.81 ± 14.37 mg/kg and a range of 19.35–47.48 mg/kg, while Mn had the least mean concentration of 0.94 ± 0.71 mg/kg and a range of 0.35–1.88 mg/kg. The result of cross-plot analysis revealed that resin fraction has strong and positive inter elemental correlation with the NSO and asphaltene fraction of the same bitumen samples. The overall results indicated that processing of the bitumen and/or its resin may cause catalyst poisoning and fouling, corrosion of equipment and pipelines, and particulate emissions into the environment and therefore adequate demetalisation of the fossil fuel must be done before processing.

Effect of split fuel injection and EGR on NOx and PM emission reduction in a low temperature combustion (LTC) mode diesel engine

In this study, an advanced combustion concept ‘premixed charge compression ignition’ (PCCI) has been explored for application in diesel engines. PCCI combustion is a single-stage combustion process, in which a large fraction of fuel burns in premixed combustion phase resulting in relatively lower in-cylinder temperatures compared to compression ignition (CI) combustion. However at high loads, PCCI combustion results in severe knocking and higher oxides of nitrogen (NOx) emissions. This limits the applicability of this combustion concept up to medium engine loads. This limitation of PCCI combustion can be resolved by altering in-cylinder pressure-temperature history at the time of fuel injection. This can also be resolved by deploying suitable split fuel injection strategy and exhaust gas recirculation (EGR), which control combustion events such as start of combustion (SoC) and combustion phasing, leading to lower knocking and NOx emissions. To investigate the effects of various split injection strategies and EGR on PCCI combustion, engine experiments were conducted at different start of main injection (SoMI) timings (12, 16, 20 and 24° bTDC), start of pilot injection (SoPI) timings (30, 35 and 40° bTDC) and EGR rates (0, 15 and 30%). This study also included detailed particulate characterization such as particulate number-size distribution using an engine exhaust particle sizer (EEPS) and particulate bound trace metal analysis by inductively coupled plasma-optical emission spectrophotometry (ICP-OES). PCCI combustion was found to be superior at 35° bTDC SoPI timing and 15% EGR. At retarded SoPI timing (30° bTDC), PCCI combustion resulted in slightly higher NOx and particulate emissions, however at too advanced SoPI timing (40° bTDC), PCCI combustion showed relatively inferior engine performance. Application of EGR improved PCCI combustion and emission characteristics, however at high EGR, PCCI combustion resulted in inferior engine performance due to reduction in bulk in-cylinder temperatures. Overall, this study showed that PCCI combustion stability, knocking and NOx emissions can be optimized by selecting suitable combination of SoMI and SoPI timings, and EGR rate.

Determination of macro, essential trace elements, toxic heavy metal concentrations, crude oil extracts and ash composition from Saudi Arabian fruits and vegetables having medicinal values

The concentrations of essential elements (Mg, Ca, Na, K, Fe, Zn, Se, Al, Ni, and Cu) and toxic heavy metals (Pb, As, Cr, Cd, and Cr) from Saudi Arabian fruits and vegetables were determined by inductively coupled plasma optical emission spectrophotometry (ICP/OES). Two types of butters, Caralluma munbayana and Caralluma hesperidum, Vigna (Vigna unguiculata), common fig (Ficus carica), Annona seeds (Annonaceae seeds), Annona fruits (Annonaceae fruits), Fennel (Foeniculum vulgare), and Fennel flowers (Nigella sativa) were investigated, because they are used by indigenous groups as traditional medicines with Soxhlet-extraction and dry-ashing protocol. The estimated daily dietary element intake in food samples was further calculated in order to evaluate the element dietary intake and fruit and vegetable consumption pattern of the indigenes of Saudi Arabia. The crude oil and ash compositions varied widely, but suggested that most of the foods were good sources of oils and minerals. The figures-of-merit of the ICP-OES calibration curves were excellent with good linearity (R2>0.9921). The use of ICP-OES in this study allowed the accurate analysis and the detection of the elements at low levels. Essential elements (K, Ca, Na, and Mg) had the highest concentrations while toxic heavy metals (As, Pb, and Cd) had the lowest in the foods. Essential element pairs (Mg-Na, Mg-Ca, Fe-Al) were highly correlated, suggesting that these foods are sources of multiple nutrients. Toxic element pairs (Pb-Cd, Pb-As, and Cd-As), however, were poorly correlated in the foods, suggesting that these elements do not have a common source in these foods. Average consumption of these foods should provide the recommended daily allowances of essential elements, but will not expose consumers to toxic heavy metals. The ICP-OES method was validated by determining method detection limits and percent recoveries of laboratory-fortified blanks, which were generally 90–100%.

Determination of total and bioavailable heavy and trace metals in South African commercial herbal concoctions using ICP-OES

In South Africa, the use of commercial herbal concoctions is becoming very popular. However, due to lack of Good Manufacturing Practices there is a possibility of heavy metal contamination in these commercial herbal concoctions. The aim of this investigation was to screen for heavy metal and trace elements in commercial herbal concoctions used in traditional medicine to treat various kinds of ailments in South Africa. This is the first investigation in which metal concentrations in commercial herbal concoctions was measured. Fourteen herbal concoctions were obtained from traditional herbal (muthi) shops and were subjected to analysis for total and bioavailable metal concentrations using Inductively Coupled Plasma-Optical Emission Spectrophotometry (ICP-OES). Of all the concoctions tested only Vusa umzimba and Sejeso herbal mixture contained high amounts of Cd (2.2 and 0.6mg/kg) respectively, exceeding the safety limit of 0.3mg/kg (WHO, 1998). Vusa umzimba also exhibited high amounts of bioavailable Cd (1.2mg/kg) thereby making it unsafe for human consumption. Surprisingly very high amounts of Hg were detected in Ingwe muthi mixture and Sejeso herbal mixture (14.9 and 12.3mg/kg) respectively. These by far exceeds the weekly allowance limit of 2μg/kg given by WHO/UN committee (2007). Relatively high amounts of Pb were found in Sejeso herbal mixture. The levels of bioavailable metals detected in this study raise concerns, not only for consumer safety, but also the quality of herbal concoctions available as part of the traditional medicinal practice in South Africa.

Cadmium determination in phosphate fertiliser using a PAN-Nafion® modified glassy carbon electrode by stripping voltammetry

A simple method for the determination of trace cadmium (Cd) (II), using a disposable 1-(2-pyridylazo)-2-naphthol [PAN]-Nafion®-coated glassy carbon electrode, has been developed. The modified electrode exhibited a significant improvement on both sensitivity and selectivity for Cd (II) determination, compared with a bare glassy carbon electrode (GCE), a PAN-coated GCE (PAN-GCE), and a Nafion®-coated GCE (Nafion® GCE). Differential pulse anodic stripping voltammetry (DPASV) was performed, in 0.05 M potassium hydrogen phthalate (KHP) buffer medium, after Cd (II) ion accumulation. The Cd(II) ion accumulated on the PAN-Nafion® surface of the glassy carbon working electrode through the formation of a chemical complex at an open circuit. The modified GCE with Cd (II) complex was then transferred to a 0.1 M KI solution and subjected to an electrochemical stripping procedure. Cyclic voltammetry (CV) was employed to confirm the successful stepwise assembly procedure for the modified electrode. The structure of PAN-Nafion® on the surface-modified electrode was characterised by scanning electron microscopy (SEM). System variables were optimised to yield the most suitable conditions, including the pH and concentration of the accumulation medium, deposition potential, deposition time, and amount of coated PAN-Nafion®. The quantitative analysis of contaminated cadmium in phosphate fertiliser samples was performed. The results obtained from the proposed method agree well with those obtained by inductively coupled plasma-optical emission spectrophotometry (ICP-OES).

Biomolecule-assisted hydrothermal synthesis of silver bismuth sulfide with nanostructures

Silver bismuth sulfide (AgBiS2) nanostructures were successfully prepared via a simple biomolecule-assisted hydrothermal synthesis at 200°C for 12–72h. Silver nitrate, bismuth nitrate and l-cysteine were used as starting materials. Here, the biomolecule, l-cysteine, was served as the sulfide source and a complexing agent. The products, characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), were cubic AgBiS2 nanoparticles with a diameter range of about 20–75nm. It was found that their crystallinity and particle size increased with increasing reaction time. The energy dispersive X-ray spectroscopy (EDX) and inductively coupled plasma optical emission spectrophotometry (ICP-OES) analyses were used to confirm the stoichiometry of AgBiS2. The optical band gap of the AgBiS2 nanoparticles, calculated from UV–vis spectra, was 3.0eV which indicated a strong blue shift because of the quantum confinement effect. A possible formation mechanism of the AgBiS2 nanoparticles was also discussed.

Enhanced Photocatalytic Activity by Silver Metal Ion Exchanged NaY Zeolite Photocatalysts for the Degradation of Organic Contaminants and Dyes in Aqueous Medium

Zeolite-based photocatalyst have been prepared using TiO2-coated NaY zeolite by post-synthesis modification with silver metal ion exchange. The characterization of the catalysts was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), Inductively coupled plasma-optical emission spectrophotometry (ICP), Diffuse reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), and N2 adsorption techniques. The presence of metal ions and TiO2 on zeolite surface was observed by UV-visible diffuse reflectance spectroscopy. It was found that the structure of the support materials is retained after the silver metal ion exchange. The photocatalytic activity of the catalysts was studied by degradation of aqueous nitrobenzene, acetophenone, methylene blue, and malachite green in the presence of UV light. The highest photocatalytic activity was obtained for silver metal ion exchanged photocatalysts coated with TiO2 (2%, w/w) as compared to other silver exchanged NaY zeolite catal...

Semi-quantitative analysis for selecting Fe- and Zn-dense genotypes of staple food crops

Four semi-quantitative screening methods were developed for plant breeding purposes to identify iron (Fe) and zinc (Zn)-dense genotypes in germplasm, elite lines and early generation progeny. Methods include colour image analysis for Fe and Zn in wheat and rice grains, and spectrophotometric analysis of Fe and Zn in ground flour of rice, wheat, potato, sweet potato and cassava. Staining with 71 mM Perl's Prussian blue solution (PPB) and subsequent image analysis with Adobe Photoshop ® to determine pixel numbers in the stained regions lead to the quantification of Fe. Due to differences in grain size between the genotypes evaluated, correlations between inductively coupled plasma-optical emission spectrophotometry (ICP-OES) Fe and PPB derived Fe were improved by standardizing according to grain weight. The ratio of total blue pixel number (TPN)/total grain weight (TGW) of 21 rice lines correlated ( r=0.84, p<0.001) with the Fe concentration derived by ICP-OES. Similarly, a colorimetric method was developed for Zn analysis using 1.56 mM Dithizone (DTZ) solution and subsequent quantification by image analysis with Adobe Photoshop ®. As with the Fe analysis, the ratio of TPN/TGW of 70 wheat lines correlated better with ICP-OES Zn analysis ( r=0.82, p<0.001) and successfully separated low and high Zn grain germplasm. Ground polished rice and wheat flour were spectrophotometrically analysed after simple extraction in 0.5 M HCl solution using a modified 2,2′-dipyridyl method for Fe, and a modified Zincon ® method for Zn. These two methods show good correlations with ICP analyses ( r=0.93 and 0.92 for Fe and Zn, respectively) and thus can be used for semi-quantitative screening to discriminate between genotypes that are either high or low in Fe or Zn. The more precise ICP-OES and AAS methods could then be used to quantify actual amounts of Fe and Zn in those genotypes identified as Fe- and Zn-dense from the initial screening.

The hammerhead, hairpin and VS ribozymes are catalytically proficient in monovalent cations alone

Background: The catalytic activity of RNA enzymes is thought to require divalent metal ions, which are believed to facilitate RNA folding and to play a direct chemical role in the reaction. Results: We have found that the hammerhead, hairpin and VS ribozymes do not require divalent metal ions, their mimics such as [Co(NH 3) 6] 3+, or even monovalent metal ions for efficient self-cleavage. The HDV ribozyme, however, does appear to require divalent metal ions for self-cleavage. For the hammerhead, hairpin and VS ribozymes, very high concentrations of monovalent cations support RNA-cleavage rates similar to or exceeding those observed in standard concentrations of Mg 2+. Analysis of all reaction components by inductively coupled plasma-optical emission spectrophotometry (ICPOES) and the use of a variety of chelating agents effectively eliminate the possibility of contaminating divalent and trivalent metal ions in the reactions. For the hairpin ribozyme, fluorescence resonance energy transfer experiments demonstrate that high concentrations of monovalent cations support folding into the catalytically proficient tertiary structure. Conclusions: These results directly demonstrate that metal ions are not obligatory chemical participants in the reactions catalysed by the hammerhead, hairpin, and VS ribozymes. They permit us to suggest that the folded structure of the RNA itself contributes more to the catalytic function than was previously recognised, and that the presence of a relatively dense positive charge, rather than divalent metal ions, is the general fundamental requirement. Whether this charge is required for catalysis per se or simply for RNA folding remains to be determined.