Search results for "Spectrophotometry"
showing 10 items of 644 documents
Supramolecular functionalization and concomitant enhancement in properties of Au25 clusters
2014
We present a versatile approach for tuning the surface functionality of an atomically precise 25 atom gold cluster using specific host-guest interactions between ?-cyclodextrin (CD) and the ligand anchored on the cluster. The supramolecular interaction between the Au25 cluster protected by 4-(t-butyl)benzyl mercaptan, labeled Au25SBB18, and CD yielding Au25SBB18�?�CDn (n = 1, 2, 3, and 4) has been probed experimentally using various spectroscopic techniques and was further analyzed by density functional theory calculations and molecular modeling. The viability of our method in modifying the properties of differently functionalized Au25 clusters is demonstrated. Besides modifying their optoe…
Microorganism adhesion experimental study using silicon dioxide
2018
AbstractIn this study, yeast, Gram positive and Gram negative bacteria were attached to silicon dioxide microparticles or silica in order to measure their absorbance, also known as physical absorption of light, changes using spectrophotometry. The goal of the study was to determine if spectrophotometry is an effective way to distinguish microorganisms and if microorganisms have an affinity for silicon dioxide since it is a suitable material for the production of prostheses. The experiment was done by examining the light absorption properties of yeast, Gram positive and Gram negative bacteria in a spectrophotometer with and without silicon dioxide microparticles. During the experiment there …
Exposure to patulin from consumption of apple-based products.
2007
Patulin is a mycotoxin produced by species of Penicillium, Aspergillus and Byssochylamys. Several Scientific Committees classify patulin as mutagenic, embryotoxic and immunotoxic. It has been found as a natural contaminant of processed apple products and its presence may be indicative of the quality of fruit used in production. In this work, a method for the analysis of patulin is described, based on a simple liquid-liquid extraction with acetonitrile; patulin is analyzed using liquid chromatography with UV detection. Patulin identity was confirmed by GC-MS after its reaction with N-methyl-N-(trimethylsilyl)trifluoroacetamide. Fifty-three apple-containing products were analyzed and patulin …
Assessment of quality of air in Palermo by chemical (ICP-OES) and cytological analyses on leaves of Eucalyptus camaldulensis
2013
In this work, we studied the influence of air pollution on the morpho-structural, biochemical and chemical composition of Eucalyptus camaldulensis leaves. Analyses were carried out on 22 samples collected in Palermo (Italy) area. Considering the mean concentrations (in unwashed leaves) of investigated metals, nutrient elements as Fe (214 mg kg(-1) dry weight (d.w.)), Mn (160 mg kg(-1) d.w.) and Zn (39 mg kg(-1) d.w.) were the most abundant, whereas Pb (5.6 mg kg(-1) d.w.) and Cd (0.072 mg kg(-1) d.w.) showed the lowest concentrations. The values of metal pollution index (MPI) ranged from 6.0 (station no. 15) to 25 (station no. 8) and from 4.0 (station no. 16) to 17 (stations no. 7 and no. 1…
Metabolism of chlorobenzene and hexachlorobenzene by the zebra fish, Brachydanio rerio.
1989
It is now becoming evident that in many cases metabolites have a greater toxic potential than the parent xenobiotic exposed. For this reason, the knowledge of biotransformation pathways of xenobiotics plays a substantial role in environmental monitoring programs. The zebra fish (Brachydanio rerio, Hamilton-Buchanan) has received increased attention as a model species for freshwater fish in environmental surveillance programs to evaluate potential health and impacts of anthropogenic chemicals. The metabolism of phenol and various substituted phenols in zebra fish has recently been studied. The purpose of the present study was to examine the metabolism of chlorobenzene and hexachlorobenzene (…
Speciation of methylmercury in market seafood by thermal degradation, amalgamation and atomic absorption spectroscopy
2014
Sample thermal decomposition followed by mercury amalgamation and atomic absorption has been employed for the determination of methylmercury (MeHg) in fish. The method involves HBr leaching of MeHg, extraction into toluene, and back-extraction into an aqueous l-cysteine solution. Preliminary studies were focused on the extraction efficiency, losses, contaminations, and species interconversion prevention. The limit of detection was 0.018µgg(-1) (dry weight). The intraday precision for three replicate analysis at a concentration of 4.2µgg(-1) (dry weight) was 3.5 percent, similar to the interday precision according to analysis of variance (ANOVA). The accuracy was guaranteed by the use of for…
Oxidation of melatonin by oxoferryl hemoglobin: A mechanistic study
2002
Reaction of melatonin with the hypervalent iron centre of oxoferryl hemoglobin, produced in aqueous solution from methemoglobin and H2O2, has been investigated at 37 degrees C and pH 7.4, by absorption spectroscopy. The reaction results in reduction of the oxoferryl moiety with formation of a heme-ferric containing hemoprotein. Stopped-flow spectrophotometric measurements provide evidence that the reduction of oxoferryl-Hb by melatonin is first-order in oxoferryl-Hb and first-order in melatonin. The bimolecular reaction constant at pH 7.4 and 37 degrees C is 112 +/- 1.0 M(-1) s(-1). Two major oxidation products from melatonin have been found by gas chromatography-mass spectroscopy: the cycl…
Heme symmetry, vibronic structure, and dynamics in heme proteins: ferrous nicotinate horse myoglobin and soybean leghemoglobin.
2000
We report the visible and Soret absorption bands, down to cryogenic temperatures, of the ferrous nicotinate adducts of native and deuteroheme reconstituted horse heart myoglobin in comparison with soybean leghemoglobin-a. The band profile in the visible region is analyzed in terms of vibronic coupling of the heme normal modes to the electronic transition in the framework of the Herzberg–Teller approximation. This theoretical approach makes use of the crude Born–Oppenheimer states and therefore neglects the mixing between electronic and vibrational coordinates; however, it takes into account the vibronic nature of the visible absorption bands and allows an estimate of the vibronic side bands…
Thermal broadening of the Soret band in heme complexes and in heme-proteins: role of iron dynamics
1994
We report the thermal broadening of the Soret band in heme-CO, heme-OH and protoporphyrin IX in the temperature range 300-20 K. For protoporphyrin IX the temperature dependent Gaussian line broadening follows the behavior predicted by the harmonic approximation in the entire temperature range investigated. In contrast, for heme-CO and heme-OH the harmonic behavior is obeyed only up to about 180 K and an anomalous line broadening increase is observed at higher temperatures. This effect is attributed to the onset of anharmonic motions of the iron atom with respect to the porphyrin plane. Comparison with previously reported analogous data for heme proteins enables us to suggest that the onset …
Immobilization of Hexacyanoferrate (III) for a Flow Injection-Spectrophotometric Determination of Promazine
1993
Abstract An automated flow injection method for the determination of promazine is described. The method is based on the oxidation of promazine by hexacyanoferrate (III) and spectrophotometric monitorization of oxidized drug. The chemical and FIA variables were optimized. The calibration graph was linear over the concentration range 2,5–25 ppm of promazine hydrochloride. Some interfering substances were also investigated. The method was applied for the determination of promazine in pharmaceutical formulations.