Nader Yourdshahi | Payam Nour University (original) (raw)

Papers by Nader Yourdshahi

Electroanalysis, Jan 1, 2007

Page 1. Review Stripping Chronopotentiometry in Environmental Analysis Núria Serrano, José Manuel... more Page 1. Review Stripping Chronopotentiometry in Environmental Analysis Núria Serrano, José Manuel Díaz-Cruz,* Cristina Arino, Miquel Esteban Departament de Química Analítica, Facultat de Química, Universitat de Barcelona ...

Reactive and Functional …, Jan 1, 1995

In the present study, Fluorescence Resonance Energy Transfer (FRET) has been used to monitor the ... more In the present study, Fluorescence Resonance Energy Transfer (FRET) has been used to monitor the folding of a 31-mer cytosine rich DNA segment, from the promoter region of the human c-myc oncogene. Spectroscopic FRET data recorded along experiments carried out at different pH and ionic strength conditions were individual and simultaneously analyzed by Multivariate Curve Resolution (MCR) (1). The simultaneous analysis of several data matrices allowed the resolution of the system, removing most of the ambiguities related to factor analysis. From the results obtained, we report the evidence of the formation of a highly ordered structure (a quadruplex known as i-motif) in acidic and neutral pH values.

Microchemical …, Jan 1, 2006

The determination of the contents of therapeutic drugs, metabolites and other important biomedica... more The determination of the contents of therapeutic drugs, metabolites and other important biomedical analytes in biological samples is usually performed by using high-performance liquid chromatography (HPLC). Modern multivariate calibration methods constitute an attractive alternative, even when they are applied to intrinsically unselective spectroscopic or electrochemical signals. First-order (i.e., vectorized) data are conveniently analyzed with classical chemometric tools such as partial

Analytica chimica acta, Jan 1, 2007

The interaction of quercetin-Cu(II) complex with calf thymus DNA was investigated with the use of... more The interaction of quercetin-Cu(II) complex with calf thymus DNA was investigated with the use of Neutral Red (NR) dye as a spectral probe by the application of UV-vis spectrophotometry, cyclic voltammetry and synchronous fluorescence spectroscopy. The results showed that both quercetin-Cu(II) complex and the NR molecule can intercalate into the double helix of the DNA. The 2:1 quercetin:Cu(II) complex (estimated binding constant = 2.85 × 10 9 ) is stabilized by intercalation in the DNA (binding constant, K [quercetin-Cu(II)-DNA] = (1.82 ± 0.20) × 10 5 M −1 ), and displaces the NR dye from the NR-DNA complex in a competitive reaction. Cyclic voltammetry studies confirm the intercalation reaction and show that the ratio (K R /K O ) of binding constants for the reduced and oxidized forms of the metal complex is 2.05. Furthermore, the alternative least squares (ALS) method was applied to resolve a complex two-way array of the absorption spectra data. This yielded the equilibrium concentration profiles of each component in the reaction (NR, NR-DNA and quercetin-Cu(II)) as well as the corresponding pure spectra. The extracted profiles showed that at equilibrium the [NR-DNA] and [NR] trends decreased and increased symmetrically, respectively, with approximately linear behaviour being observed below 10 × 10 −6 mol L −1 of the added quercetin-Cu 2+ complex. Thereafter, these trends converged asymptotically. The free [quercetin-Cu(II)] trend-line at equilibrium was linear over the whole range of the complex added. It was possible to estimate the approximate value of the equilibrium constant of the exchange process (approximately 5 × 10 −1 ) involving the intercalation of the quercetin-Cu(II) complex. It was also found that about 35% of the bound complex was unaccounted by the intercalation reaction, presumably being stabilized at an alternative site.

Contributions to Science, Jan 1, 2004

igitur-archive.library.uu.nl

The physicochemical processes that occur during the preparation of CoMo-Al 2 O 3 hydrodesulphuriz... more The physicochemical processes that occur during the preparation of CoMo-Al 2 O 3 hydrodesulphurization catalyst bodies have been investigated. To this end, the distribution of Mo(VI)-and Co(II)-complexes, after impregnation of γ-Al 2 O 3 pellets with different CoMo(P)solutions, was monitored using Raman and UV-Vis-NIR micro-spectroscopy. From the speciation of the different complexes over the catalyst bodies, insight was obtained into the interaction of the different components in the impregnation solution with the Al 2 O 3 surface. It was shown that, after impregnation with a solution containing H 2 PMo 11 CoO 40 5-, the reaction of phosphate with the Al 2 O 3 leads to the disintegration of this complex. The consecutive independent transport of Co(II)-complexes (fast) and Mo(VI)-complexes (slow) through the pores of the Al 2 O 3 was envisaged. By the addition of extra phosphate and citrate to the impregnation solution, the formation of the desired heteropolyanion could be achieved inside the pellets. Ultimately, the H 2 PMo 11 CoO 40 5distribution could be applied by varying the aging time, that was applied after impregnation. The power of a combination of Raman and UV-Vis-NIR micro-spectroscopy in order to monitor the preparation of CoMo/Al 2 O 3 catalyst bodies is illustrated.

International Journal of Environment …, Jan 1, 2008

Biosorption is a process of metabolism-independent, passive, physico-chemical binding of metal io... more Biosorption is a process of metabolism-independent, passive, physico-chemical binding of metal ions involving non-living biomass, which offers advantages over conventional methods because of cost-effectiveness, especially for dilute metal solutions, and minimal environmental impact. This paper reviews heavy metal biosorption using silvichemical-based biomass materials. It discusses the use of a wide range of silvichemical biomasses and their derivatives for heavy metal removal from single and multi-metal systems. The structures and properties of silvichemical biomasses as well as methods of biosorbent pretreatment and immobilisation are evaluated. Metal biosorption mechanisms and binding sites, selective biosorption and biosorbent reuse and regeneration are also addressed.

... aptamers. 47 54 In addition to Metal ComplexDNA Interactions Edited by Nick Hadjiliadis an... more ... aptamers. 47 54 In addition to Metal ComplexDNA Interactions Edited by Nick Hadjiliadis and Einar Sletten © 2009 Blackwell Publishing Ltd. ISBN: 978-1-405-17629-3 Page 2. 56 Metal Ion Coordination in G-Quadruplexes ...

… at the beginning of the 21st …, Jan 1, 2004

... In this article, a general overview of the application of the soft-modelling technique design... more ... In this article, a general overview of the application of the soft-modelling technique designated Multivariate Curve Resolution by Alternating Least Squares to voltammetric data from metal complex system is presented. KEYWORDS ...

Applied spectroscopy, Jan 1, 2003

Journal of Chromatography A, Jan 1, 2006

Multivariate curve resolution-alternating least squares (MCR-ALS) is applied to solve coelution p... more Multivariate curve resolution-alternating least squares (MCR-ALS) is applied to solve coelution problems in liquid chromatograpy with diode array detection (DAD) and mass spectrometry (MS). Fusion of DAD and MS detector signals improved results versus those obtained using only one of the two detector signals. Application of wavelet transform to MS data before its fusion with DAD data, further help to facilitate the resolution and quantitation of the coeluted compounds under study, besides a decrease of time of analysis. Mixtures of biocide compounds in standard mixtures and in environmental samples (sediment and wastewater samples) were analyzed with estimated quantitation errors below 12%.

Analytical and bioanalytical chemistry, Jan 1, 2008

Analytica chimica …, Jan 1, 2001

In this study, a straightforward approach is proposed for determining the figures of merit in mul... more In this study, a straightforward approach is proposed for determining the figures of merit in multivariate curve resolution. The method is based on the recovery of the pure response profiles of the analytes after a curve resolution procedure. Figures of merit such as limit of detection, sensitivity, precision and accuracy are estimated from these pure analyte responses using univariate statistics directly from a calibration graph, as usual in univariate calibration. Examples of the calculation of the figures of merit in the determination of triphenyltin in synthetic and natural sea water samples by using excitation-emission matrix fluorescence are given.

Analytica chimica acta, Jan 1, 2001