Mohammed Meetani - Academia.edu (original) (raw)

Papers by Mohammed Meetani

Chemosphere, Jun 1, 2010

The photolytic degradation of the diazo dye, Amido Black, using UV/H(2)O(2) has been carried out ... more The photolytic degradation of the diazo dye, Amido Black, using UV/H(2)O(2) has been carried out experimentally and parameters for most efficient dye degradation have been determined. The degradation of the dye was followed by UV-Vis spectroscopy, HPLC, and LC-MS and is proposed to be initiated by ()OH radicals formed by the photolysis of H(2)O(2). A detailed study was also carried out using LC-MS and LC-MS/MS to determine the degradation pathway of the dye as well as to identify some of the intermediate products formed. Our results suggest that Amido Black degradation occurs preferentially by ()OH radical attack at the more electron rich diazo functionality of the molecule. Furthermore, evidence is presented that subsequent steps in this diazo dye degradation pathway include radical denitration, radical desulfonation and radical diazotization. This report is one of the very few studies that have proposed possible mechanistic pathways for the degradation pathways of a diazo compound.

Peptides, Oct 1, 2009

Taxonomic revisions within the anuran family Ranidae have established the genus Lithobates that c... more Taxonomic revisions within the anuran family Ranidae have established the genus Lithobates that currently comprises 49 species of frogs from the New World. Peptidomic analysis, using reversed-phase HPLC with on-line detection by electrospray mass spectrometry, has led to the identification of multiple antimicrobial peptides in norepinephrine-stimulated skin secretions of the North American frog Lithobates capito and the Central American frog Lithobates warszewitschii. Structural characterization of the peptides demonstrated that the L. capito secretions contained brevinin-1 (1), esculentin-1 (1), esculentin-2 (1), ranatuerin-2 (3), and temporin (2) peptides. L. warszewitschii secretions contained brevinin-1 (1), esculentin-2 (1), ranatuerin-2 (2), and temporin (1) peptides. Values in parentheses indicate number of peptides in each family. Temporin-CPa from L. capito, with the atypical structure IPPFIKKVLTTVF.NH(2), also showed atypical growth-inhibitory activity having greater potency against Escherichia coli (MIC=25 microM) and Candida albicans (MIC=25 microM) than against Staphylococcus aureus (MIC=50 microM). Phylogenetic analysis based upon the amino acid sequences of 37 ranatuerin-2 peptides from 17 species belonging to the genus Lithobates provides support for currently accepted taxonomic relationships. L. capito is sister-group to Lithobates sevosus in a clade that also contains Lithobates areolatus, and Lithobates palustris. L. warszewitschii is most closely related to the Central American species Lithobates tarahumarae and Lithobates vaillanti.

World Journal of Chemical Education

Frontiers in Chemistry

Sensitive spectrofluorometric and liquid chromatography with fluorescence detection methods have ... more Sensitive spectrofluorometric and liquid chromatography with fluorescence detection methods have been developed for detection and determination of naproxen drug in the presence of cucurbit7uril (CB7). Fluorescence signals have been improved with the addition of CB7 to the drug aqueous solution. Fluorescence spectroscopy, mass spectrometry, 1H-NMR, and liquid chromatography with fluorescence detection were used to investigate the guest-host interaction of naproxen drug and cucurbiturils. Naproxen was found to form a supramolecular complex with CB7 that had a high formation constant. The optimal conditions for the interaction were discovered using spectroflurometry to be 0.2 mg/ml of CB7, 2.4 μg/ml of naproxen drug, and pH10. A 1:1 complex between naproxen and CB7 is revealed by proton NMR and tandem mass spectrometry. Using the standard addition calibration method, an HPLC with a fluorescence detector was used to detect naproxen in influent and effluent wastewater samples. Finally, i...

IOP Conference Series: Earth and Environmental Science, 2020

Limited work has been done to assess the types and levels of PACs in domestic and treated wastewa... more Limited work has been done to assess the types and levels of PACs in domestic and treated wastewater in arid and semi-arid countries. In these countries, reuse or artificial recharge of treated sewage effluent is commonly practiced. Thus, the objectives of this study were to quantify the levels of selected PACs in domestic wastewater in the United Arab Emirates (UAE) and to assess the effectiveness of domestic wastewater treatment plants in their removal. An analytical protocol was developed for the analysis of 15 PACs using a UPLC-MS/MS system. Four batches of water and sludge samples were collected from different locations at Al Saad Wastewater Treatment Plant in Al Ain, UAE. Aliquots of each sample were enriched by solid phase extraction. Results show that phenylephrine, dapsone, noscapine, propyl gallate, genistein, and ketoconazole were present in the raw wastewater at low levels (<0.1 μg/L), while acetaminophen and caffeine were present at high levels (>10 μg/L). The ove...

Desalination and Water Treatment, 2015

Cellulose is one of the most abundant natural polymers. Combined with its unique properties, cell... more Cellulose is one of the most abundant natural polymers. Combined with its unique properties, cellulose nanofibers, therefore, have potential applications in industry. Electrospinning is a convenient technique that is widely used to make nanofibers. This process, however, needs optimization in order to fine tune the produced nanofibers. The current study investigates the effects of varying the different electrospinning parameters on the quality and monodispersity of the produced nanofibers. Cellulose acetate (CA), a cellulose precursor, is used in this regard. Solutions containing different concentrations of CA, up to 20% by weight, were electrospun into micro-nanofibers. The produced nanofibers were characterized by SEM, DSC, and IR techniques. Results showed the crucial dependence of the nanofibers monodispersity on the CA solution concentration, the applied voltage, the flow rate, the spinning distance, and the nature of atmosphere surrounding the electrospinning setup. Optimally prepared CA membranes as well as two commercially available filtering membranes were utilized in the removal of tiny solid particulates from drinking water media.

Applied Catalysis A: General, 2015

Graphical asbtract Research Highlights  Facile and simple microwave-assisted synthesis of In3+ d... more Graphical asbtract Research Highlights  Facile and simple microwave-assisted synthesis of In3+ doped SnS2 as visible-lightdriven photocatalyst  3D flow-like In-SnS2 with high photocatalytic reduction kinetics of Cr(VI)  Formic acid as hole scavenger, positively affect reduction of Cr(VI)

TrAC Trends in Analytical Chemistry, 2013

Advanced oxidation processes (AOPs) are commonly used for degrading dyes in effluents. Valuable i... more Advanced oxidation processes (AOPs) are commonly used for degrading dyes in effluents. Valuable information regarding AOP-mediated formation of intermediates and degradation products can be obtained by using liquid chromatography coupled to mass spectrometry as an analytical technique. We review the recent outcomes on this subject with respect to analytical procedures, literature citations and the proposed reaction mechanisms.

Journal of Chemical Research, 2010

Upon reaction with an excess of 2,2-dimethylpropane-1,3-diol (neopentyl glycol, NPG) under acid c... more Upon reaction with an excess of 2,2-dimethylpropane-1,3-diol (neopentyl glycol, NPG) under acid catalysis, indanones and tetralones yield indenes and dihydronaphthalenes, respectively. The reaction can also be carried out with butane-1,3-diol.

Bulletin of the Chemical Society of Japan, 1977

Journal of Chromatographic Science, 2019

A sensitive and selective method for detection and quantitation of the enantiomers of 18 syntheti... more A sensitive and selective method for detection and quantitation of the enantiomers of 18 synthetic cathinones with tertiary amine structure using HPLC-UV-VIS has been developed. Two chiral columns, Astec Cellulose DMP and Amylose-based Chiralpak ASH , have been examined separately. Mobile phase composed of hexane, isopropanol and triethylamine (99.0:1.0:0.1) was used under an isocratic elution mode. Three of these compounds were separated simultaneously after being spiked into urine and plasma samples. 2,3-Methylenedioxy pyrovalerone was used as an internal standard for the purpose of quantitation. The analytical method has been validated in terms of linearity, limits of detection (LOD), limits of quantitation (LOQ), recoveries and reproducibilities in urine and plasma matrices. The calibration curves exhibited correlation coefficients better than 0.99. It was found that the LODs of these cathinone derivatives in urine were in the range of 1.00-1.47 ppm; while in plasma, the LODs were in the range of 0.14-0.67 ppm. The LOQs in urine were in the range of 3.03-4.46 ppm and in plasma they were in the range of 0.42-2.04 ppm. The method recoveries in terms of percent error averaged 2.4% and 3.2% for the spiked plasma and urine samples, respectively; while interday and intraday reproducibilities reported at three different levels, 5, 100 and 200 ppm, in terms of coefficient of variance were in the range of (0.27-5.39)% in plasma and (0.47-3.12)% in urine which lies in the acceptable range.

RSC Advances, 2011

ABSTRACT Photocatalytic degradation of Orange G dye was carried out with UV light in the presence... more ABSTRACT Photocatalytic degradation of Orange G dye was carried out with UV light in the presence of TiO2 mixed with 20% chromium oxide as a catalyst. The conditions for maximum dyedegradation were optimized in terms of catalyst amount, dye concentration, pH and time. The dyedegradation followed pseudo first-order kinetics. LC-MS/MS was used to track the numerous intermediate products formed during the course of dyedegradation. Major intermediate products confirmed were substituted phenols, aromatic hydroxyl amine, nitrosohydroxylaromatic amines and dicarboxylaromatic compounds. These intermediates along with some minor products were correlated to suggest a possible degradation pathway of Orange G. The dyedegradation occurred mainly by three pathways, namely the hydroxylation of the aromatic ring, desulfonation and oxidative cleavage of the azo bond.

Peptides, 2011

Using a combination of reversed-phase HPLC and electrospray mass spectrometry, peptidomic analysi... more Using a combination of reversed-phase HPLC and electrospray mass spectrometry, peptidomic analysis of norepinephrine-stimulated skin secretions of the American bullfrog Lithobates catesbeianus Shaw, 1802 led to the identification and characterization of five newly described peptides (ranatuerin-1CBb, ranatuerin-2CBc, and -CBd, palustrin-2CBa, and temporin-CBf) together with seven peptides previously isolated on the basis of their antimicrobial activity (ranatuerin-1CBa, ranatuerin-2CBa, brevinin-1CBa, and -1CBb, temporin-CBa, -CBb, and -CBd). The abilities of the most abundant of the purified peptides to stimulate the release of insulin from the rat BRIN-BD11 clonal β cell line were evaluated. Ranatuerin-2CBd (GFLDIIKNLGKTFAGHMLDKIRCTIGTCPPSP) was the most potent peptide producing a significant stimulation of insulin release (119% of basal rate, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.01) from BRIN-BD11 cells at a concentration of 30nM, with a maximum response (236% of basal rate, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) at a concentration of 3μM. Ranatuerin-2CBd did not stimulate release of the cytosolic enzyme, lactate dehydrogenase at concentrations up to 3μM, indicating that the integrity of the plasma membrane had been preserved. Brevinin-1CBb (FLPFIARLAAKVFPSIICSVTKKC) produced the maximum stimulation of insulin release (285% of basal rate, P&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001 at 3μM) but the peptide was cytotoxic at this concentration.

Peptides, 2013

A comparison of host-defense peptides in skin secretions of female Xenopus laevis × Xenopus borea... more A comparison of host-defense peptides in skin secretions of female Xenopus laevis × Xenopus borealis and X. borealis × X. laevis F1 hybrids

Journal of Fluorescence, 2011

Salicylaldehyde was found to have a high selectivity for zinc ions with simultaneous enhancement ... more Salicylaldehyde was found to have a high selectivity for zinc ions with simultaneous enhancement of fluorescence in aqueous buffer solution at optimum pH 8.5. The stoichiometry of the complex was determined to be 1:1 with a K(a) value of 3.4 × 10(4) M(-1) at 298 K. The fluorescence of the complex is not affected by common anions and Zn(2+) binds preferentially to salicylaldehyde in the presence of alkali, alkaline earth and heavy metal cations (Hg(2+), Cd(2+), Cr(3+) and Ni(2+)). This property is not observed with related phenolic compounds bearing a carbonyl group such as esters, amides, carboxylic acids and ketones.

Journal of Chemical Ecology, 2013

Population declines due to amphibian chytridiomycosis among selected species of ranid frogs from ... more Population declines due to amphibian chytridiomycosis among selected species of ranid frogs from western North America have been severe, but there is evidence that the Oregon spotted frog, Rana pretiosa Baird and Girard, 1853, displays resistance to the disease. Norepinephrine-stimulated skin secretions were collected from a non-declining population of R. pretiosa that had been exposed to the causative agent Batrachochytrium dendrobatidis. Peptidomic analysis led to identification and isolation, in pure form, of a total of 18 hostdefense peptides that were characterized structurally. Brevinin-1PRa,-1PRb,-1PRc, and-1PRd, esculentin-2PRa and-PRb, ranatuerin-2PRa,-2PRb,-2PRc, and-2PRe, temporin-PRb and-PRc were identified in an earlier study of skin secretions of frogs from a different population of R. pretiosa known to be declining. Ranatuerin-2PRf,-2PRg,-2PRh, temporin-PRd,-PRe, and-PRf were not identified in skin secretions from frogs from the declining population, whereas temporin-PRa and ranatuerin-2PRd, present in skin secretions from the declining population, were not detected in the current study. All purified peptides inhibited the growth of B. dendrobatidis zoospores. Peptides of the brevinin-1 and esculentin-2 families displayed the highest potency (minimum inhibitory concentration = 6.25-12.5 μM). The study provides support for the hypothesis that the multiplicity and diversity of the antimicrobial peptide repertoire in R. pretiosa and the high growth-inhibitory potency of certain peptides against B. dendrobatidis are important in conferring a measure of resistance to fatal chytridiomycosis.

Comparative Biochemistry and Physiology Part D: Genomics and Proteomics, 2012

Peptidomic analysis was used to compare the distribution of host-defense peptides in norepinephri... more Peptidomic analysis was used to compare the distribution of host-defense peptides in norepinephrine-stimulated skin secretions from laboratory-generated female F1 hybrids of the common clawed frog Xenopus laevis (Daudin, 1802) and Mueller's clawed frog Xenopus muelleri (Peters, 1844) with the corresponding distribution in skin secretions from the parent species. A total of 18 peptides were identified in secretions from the hybrid frogs. Eleven peptides (magainin-1, magainin-2, CPF-1, CPF-3, CPF-4, CPF-5, CPF-6, CPF-7, XPF-1, XPF-2, and PGLa) were identified in secretions of both the hybrids and X. laevis. Four peptides (magainin-M1, XPF-M1, CPF-M1, and tigerinin-M1) were previously found in skin secretions of X. muelleri but magainin-M2 and CPF-M2 from X. muelleri were not detected. Three previously undescribed peptides (magainin-LM1, PGLa-LM1, and CPF-LM1) were purified from the secretions of the hybrid frogs that were not detected in secretions from either X. laevis or X. muelleri. Magainin-LM1 differs from magainin-2 from X. laevis by a single amino acid substitution (Gly 13 → Ala) but PGLa-LM1 and CPF-LM1 differ appreciably in structure from orthologs in the parent species. CPF-LM1 shows potent, broad-spectrum antimicrobial activity and is hemolytic. The data indicate that hybridization increases the multiplicity of skin host-defense peptides in skin secretions. As the female F1 hybrids are fertile, hybridization may represent an adaptive strategy among Xenopus species to increase protection against pathogenic microorganisms in the environment.

Journal of Fluorescence, 1998

It is shown that the relative intensity of the twisted intramolecular charge transfer (TICT) band... more It is shown that the relative intensity of the twisted intramolecular charge transfer (TICT) band of ester and benzonitrile derivatives of dialkylaniline in polymethylmethacrylate polymer matrices of different molecular weights (MW) to increase with increasing MW of the polymer. Our results emphasis the role of local free volumes (mobility in the matrix cage) and focus attention on the role of the MW of the polymer on the fluorescence of various TICT probes. These observations are confirmed by the red edge effect and fluorescence decay results.

Sensors and Actuators B: Chemical, 2015

Mercury ion (Hg 2+) sensors based on graphene and gold nanoclusters are presented in this work. T... more Mercury ion (Hg 2+) sensors based on graphene and gold nanoclusters are presented in this work. The sensors follow the structure of field-effect transistor (FET), and their sensing mechanism rely on the change in conductance of graphene and gold nanocluster percolating film. Each sensor was fabricated by deposition of interdigitated metal electrodes on the surface of graphene by thermal evaporation through a shadow mask. Next, gold nanoclusters are generated by magnetron discharge sputtering and inert-gas condensation inside an ultra-high compatible system, and they are self-assembled on the surface of graphene. The sensitivity and selectivity of graphene to Hg 2+ are vastly enhanced by incorporating the nanoclusters on its surface. The detection limit of the present sensors is below the safe concentration of Hg 2+ in drinking water set by different universal agencies. In addition, those sensors are practical and easy to operate in field for real life applications.