A simple, rapid and cost effective preconcentration method is described for the determination of thallium in aqueous samples and human plasma using ion pair solvent microextraction (IP-SME) followed by flame atomic absorption spectrometry (FAAS). In trace element analysis, preconcentration and separation methods enhance the sensitivity and precision of the determination. In a preconcentartion step 10 ml of Tl solution was adjusted at pH=8 and treated with 2ml of 0.1 % 2-pyridyn mercaptan (PyM) transferred to a 15ml vial. Thallium formed a cationic complex with 2-pyridyn mercaptan. For creating ion pair and converted cationic complex to nonpolar form, 0.5 ml of 1% picric acid, as a counter ion, was added to the sample solution. The solution was stirred by a magnetic stirrer with a 6-mm bar at an optimized speed of 500 rpm. The ionpair, (Tl- PyM) + (picrate)- was formed and extracted by the acceptor phase consisting 4µl of nitrobenzene for 10 min. After extraction, the microdrop was retracted and to be measured by FAAS the drop volume was brought to 50 µl by acetone. Resulting solution directly injected into the nebulizer of AAS by a micro syringe for subsequent determination. Some effective parameters on extraction and complex formation, such as type and volume of organic solvent, pH, concentration of chelating agent and counter ion, extraction time and stirring rate were optimized. Under the optimum conditions, the enrichment factor and recovery were 188.0 and 94.0%, respectively. The calibration graph was linear in the range of 12 - 130 µg L-1 with correlation coefficient of 0.9989 under the optimum conditions of the recommended procedure. The detection limit based on the 3Sb criterion was 3.6 µg L-1 and relative standard deviation for (RSD) for ten replicate measurements of 50 µg L-1 and 100 µg L-1 lead was 4.9 and 4.7 % respectively. The results for determination of thallium in reference materials and human plasma demonstrated the accuracy, recovery and applicability of the presented method.
The Newman superposition model has been used to investigate the substitution of Mn2+ for Mg2+ site in (Mg)2SiO4 single crystals. The calculated values of zero field splitting parameter b0 2 at room temperature fit the experimental one taken from the literature with average intrinsic parameters b2 (O) = Â0.0419 c for oxygen taken t2 = 7 and t4 = 10 for Mn2+ doped in (Mg)2SiO4 single crystal. The values of b2 determined for Mn2+ doped in (Mg)2SiO4 single crystals is -0.073 cm-2. The superposition model analysis shows that for large values of b2 0, b2 2, b4 0, b4 2 and b4 4 intrinsic parameters 2 and 4 can be estimated with suitable error but for small values of these spin  Hamiltonian parameters it is very difficult to predict the correct sign and magnitude. The present study about superposition model is very useful to get information about the zero field splitting of parameters ions in some host single crystals
Microorganisms require water for their metabolic activities. Only a fraction of water in foodstuffs, the so‐called free water, is available for this purpose. The amounts of free water previously estimated by two different methods (Frosch et al. (2010), Frosch et al. (2011), and Low (1969)) are compared for aqueous solutions of four electrolytes, NaCl, NH 4 Cl, Na 2 SO 4 , (NH 4 ) 2 SO 4 : (i) vapour pressure measurements of the solutions relative to that of pure water (water activities) and (ii) low‐wavenumber Raman spectra in the R( ν )‐representation. For each electrolyte deviations were found between results from the two methods. All water molecules in the illuminated volume contribute to the Raman data. The vapor pressure measurements refer to water molecules at the water/atmosphere interface where surface tension is important. Differences in surface tension for the four electrolytes qualitatively explain deviations between the amounts of “free water” observed by the two methods.
Optical techniques of photobiostimulation, which use transducer as lasers and LEDs, have been employed in the treatment of several diseases. The laser systems usually irradiate in a reduced area of the target biological tissue, presenting high cost of acquisition. Devices with a LED of Surface Mount Device (SMD) type have high angle of light emission, implying in intense decrease of the density of optical potency. Furthermore, the use of this device requires the utilization of a cooling system, which provokes an increase in the cost of this product. In the present work, it is suggested the application of a novel opto-mechanical device constituted by usual LEDs with package dimension of 5 mm of diameter, which presents significant efficient and very low cost. The arrangement of the geometric configuration of these LEDs is elaborated in such way that all units emit photons in a unique section of an specific area. An opto-mechanical system was developed, which includes seven LEDs, being that six of these LEDs are disposed in a specific angle around a unique central LED. It is important to notice that all the opto-mechanical system with seven LEDs emit light in a unique area. Besides, a methodology was employed to allow the verification of the distribution of light intensity upon this respective area. This arrangement allows that this novel device propitiate measurements of the degree of homogeneity of the light intensity in specific areas, which are accessed by the seven light emitting units. The potency employing LEDs in the red (visible) and near infrared regions were also measured, being that the result demonstrated the capability of clinical application in optical therapy of photobiostimulation, which was also used in a pilot test of clinical application.
The interaction between bovine serum albumin (BSA) and Prodigiosin (PG) was investigated by UV-vis absorption, fluorescence, synchronous fluorescence, FT-IR and circular dichroism (CD) techniques. The data of UV-vis absorption and fluorescence spectra displayed that there existed interaction between PG and aromatic amino acid residues of BSA. The synchronous fluorescence and CD spectrum experiment both showed that the secondary structure of BSA changed with addition of PG. All these results revealed that the conformation and microenvironment of BSA were changed.
Preeclampsia is associated with increased perinatal morbidity and mortality. There have been numerous efforts to determine preeclampsia biomarkers by means of biophysical, biochemical, and spectroscopic methods. In this study, the preeclampsia and control groups were compared via band component analysis and multivariate analysis using Raman spectroscopy as an alternative technique. The Raman spectra of serum samples were taken from nine preeclamptic, ten healthy pregnant women. The Band component analysis and principal component analysis-linear discriminant analysis were applied to all spectra after a sensitive preprocess step. Using linear discriminant analysis, it was found that Raman spectroscopy has a sensitivity of 78% and a specificity of 90% for the diagnosis of preeclampsia. Via the band component analysis, a significant difference in the spectra of preeclamptic patients was observed when compared to the control group. 19 Raman bands exhibited significant differences in intensity, while 11 of them decreased and eight of them increased. This difference seen in vibrational bands may be used in further studies to clarify the pathophysiology of preeclampsia.
Based on the quenching effect of emodin on the luminol-myoglobin (Mb) reaction, a sensitive method for the determination of nanogram level emodin by flow injection chemiluminescence (FI-CL) is presented for the first time. It was found that the CL intensity from luminol-Mb system could be inhibited in the presence of emodin, and the decrement of CL intensity was linearly proportional to the logarithm of emodin concentration in the range of 0.5– (R= 0.9956) with the detection limit of (3σ). At a flow rate of , a complete determination of emodin, including sampling and washing, could be accomplished in 0.5 min with the relative standard deviations (RSDs) of less than 3.5% (n= 5). The proposed method was successfully applied to the determination of emodin in pharmaceutical preparations and human serum samples. The possible CL mechanism of luminol-Mb-emodin reaction was explained.
The binding of irbesartan to bovine hemoglobin (BHb) has been investigated for the first time by using UV-Vis absorption, fluorescence, circular dichroism (CD), and molecular docking. The binding site numbernand binding constantKwere calculated to be 1 and , respectively. The alternations of protein secondary structure in the presence of irbesartan was demonstrated using CD spectroscopy. Furthermore, molecular docking indicated that irbesartan could bind to the site 2 of BHb. The analysis of the binding site of irbesartan within the BHb molecule suggested that hydrophobic interaction, hydrogen bond formation, and electrostatic interaction could account for the binding of irbesartan. The hydrogen bond of irbesartan with His87 in the C chain of BHb has been formed. The electrostatic energy, van der Waals energy, and binding free energy were calculated to be −460.3, −224.2, and−684.5 kcal, respectively.
Fungi are considered as serious pathogens for many plants, potentially causing severe economic damage. Early detection and identification of these pathogens is crucial for their timely control. The methods available for identification of fungi are time consuming and not always very specific. In this study, the potential of FTIR-ATR spectroscopy was examined together with advanced mathematical principle component analysis (PCA) and statistical linear discriminant analysis (LDA) to differentiate among 10 isolates of Fusarium oxysporum. The results are encouraging and indicate that FTIR-ATR can successfully detect different isolates of Fusarium oxysporum. Based on PCA and LDA calculations in the region 850-1775 cm(-1) with 16 PC's, the different strains from the same fungal genus could be classified with 75.3% and 69.5% success rates using the "leave one out" method and "20-80% algorithm" respectively.
In this paper, we describe a new method to obtain D 2 O/H 2 O exchange in photosynthetic reaction centres from Rhodobacter sphaeroides . The method is characterized by: (i) a very high efficiency of the isotopic replacement; (ii) an extremely low amount of D 2 O needed; (iii) the short time required for dehydration and D 2 O rehydration; (iv) the possibility of controlling concomitantly the hydration state of the sample. The proposed method can be applied to other proteins.
We investigated distribution of phosphorus under manganese toxicity in different tissues of 10 μ m thin‐root cross‐section of Douglas fir (DF) ( Pseudotsuga menziesii ) seedlings by using synchrotron‐based Fourier transform infrared microscopy (SR‐FTIR) as a chemically sensitive imaging method. Manganese is an essential micronutrient in all organisms but may become toxic when present in excess. We found previously that DF variety glauca (DFG) and variety menziesii (DFM) differed in phosphorus uptake, subcellular localization, transport and tissue allocation, as an effect of manganese toxicity. To address the role of P in seedling tolerance under Mn toxicity, we determined P allocation in different root tissues. In DFG, but not in DFV, the P concentration was kept at a constant level even under Mn toxicity. Earlier X‐ray microanalysis showed Mn accumulation in epidermal and cortical cells of both varieties after Mn treatment, suggesting that the root endodermis was a barrier for Mn to protect the vascular system and shoot from high Mn, with possible role of P ameliorations. Here, we discuss the potential role of P in Mn compartmentalization and toxicity tolerance in two different varieties.
In our previous study thermodynamic denaturation of bovine β-lactoglobulin variant A (BLG-A), has been investigated in the presence of cetylpyridinium chloride (CPC) as a cationic surfactant. Here, the retinol binding property of BLG was determined at 298 K and pH 8.0 by spectrofluorimeter titration method, in the presence of CPC to elucidate the still unknown structure–function relationship in this protein. Comparison of the results allowed determining the binding of retinol by BLG in the presence of CPC. The two-way chemometrics method was used, to estimate the equilibrium concentration of components by analysis of fluorescence emission spectrum, in order to obtain its equilibrium concentration. The results indicate that the retinol binding properties of BLG do not show significant changes in the presence of this surfactant.
Folding dynamics for β ‐structure loss and disordered structure gain were studied in a model β ‐hairpin peptide based on Cochran’s tryptophan zipper peptide Trpzip2, but with an altered Thr‐Gly (TG) turn sequence, that is, SWTWE TG KWTWK, using laser‐induced temperature‐jump (T‐jump) kinetics with IR detection. As has been shown previously, the TG turn sequence reduces the thermodynamic β ‐hairpin stability as compared to the Asn‐Gly sequence used in Trpzip2 (TZ2‐NG). In this study, we found that the TG‐turn slows down the overall relaxation dynamics as compared to TZ2‐NG, which were studied at higher temperatures where the time constants show little difference between relaxation of the β ‐strand and the disordered conformation. These time constants become equivalent at lower temperatures for TZ2‐TG than was seen for TZ2‐NG. The correlation of thermodynamic stability and rates of relaxation suggests that the change from NG to TG turn results in a slowing of folding, lower k f , with less change of the unfolding rate, k u , assuming two state behavior at higher temperatures.
Fourier transform infrared (FT-IR) spectroscopic imaging is a highly versatile technique that can be applied to a wide range of systems. This article summarizes some of the recent efforts developing applications of FT-IR imaging for microfluidics. The main advantage of FT-IR imaging compared to traditional imaging methods is that it is a label-free imaging technique. There is no need to develop tags or labels, multiple components are simultaneously traced, and images can be taken without disturbing the sample. All of these advantages are accompanied with a near-video frame rate acquisition speed. Different approaches to obtain FT-IR images (transmission and attenuated total reflection mode) of microfluidic devices are discussed including novel ways to create microfluidic devices.
The evaluation of the electronic charge distribution in metal complexes enables more precise interpretation of mechanism by which particular metal ions affect biochemical properties of ligands [J. Inorg. Biochem. 99 (2005), 1407–1423, J. Mol. Struct. 919 (2009), 284–289]. In this paper we investigated the influence of alkali metal cations (lithium, sodium, potassium, rubidium and cesium) on the electronic structure ofp-coumaric acid (p-CA). It allowed to observe the systematic changes in the spectra of investigated complexes depending on the position of the element in the periodic table.p-Coumaric acid is a derivative of cinnamic acid that occurs in several plant species. Li, Na, K, Rb and Csp-coumarates were synthesized and the experimental and theoretical FT-IR, FT-Raman,1H and13C NMR spectra ofp-coumaric acid and its salts were registered and analyzed. The structures, atomic charges, infrared and NMR spectra ofp-coumaric acid and Li, Na, K salts were calculated by B3LYP/6-311++G**method.
Two simple, sensitive and selective spectrophotometric methods have been described for the determination of the psychoactive drug, thioridazine HCl in tablets and in biological fluids. The first method is based on the oxidation of thioridazine HCl with measured excess of KMnO4 under acidic conditions followed by the determination of unreacted oxidant using indigo carmine and methyl orange. The second method is based on the formation of ion-pair complexes with the acidic sulphophthalein dyes such as bromocresol green and bromocresol purple at pH 1.8 of KCl-HCl buffer. The formed complexes were extracted into methylene chloride and their absorbance was measured at 412 nm. Optimizations of the different experimental conditions are described for both methods. The proposed methods were successfully applied for determination of the drug in tablets and biological fluids with good accuracy and precision. Statistical comparison of the results with those obtained by an official method showed good agreement and indicated no significant difference in accuracy and precision.
Uptake of the β -blocker drug propranolol by living glial C6 cells has been observed using fluorescence lifetime imaging with two-photon excitation at 630 nm. Both uptake and release of propranolol occur within minutes and are temperature dependent, being about 5 times faster at 37°C than at 20°C. The intracellular fluorescence lifetime of propranolol is generally shorter than the value of 9.8 ns determined in dilute neutral aqueous solution, and the difference is ascribed to concentration quenching. Within the cells, propranolol is accumulated within intracellular acidic vesicles and the cytoplasm but is excluded from the cell nucleus. On incubation of cells in medium containing 100 μ M propranolol, the drug is accumulated to reach intracellular concentrations up to 10 mM in a process that is believed to be driven by protonation within acidic cellular compartments.
The aim of the present study is to evaluate the differences on FTIR spectra of the normal lung cell (noncancerous mice lung epithelial cell line e10) due to different fixation protocols for histological processing. The results shown that formalin and methacarn (normally used in fixation) did cause many changes on the FTIR spectra of mice lung cells e10, mainly in the organic compounds (800–1800 cm−1) in lipids, DNA, and proteins, and the alcohol 70% fixation protocol caused almost no changes on the FTIR spectra compared to unfixed cells spectra (in PBS). It can be concluded that histological processing with alcohol 70% fixation protocol can be used in the FTIR study of mice lung cell line e10.
This work deals with the theoretical study on the molecular structure and vibrational spectra of two well-known natural products: lupeol and lupenone. The spectra were interpreted with the aid of normal mode analysis following full-structure optimization carried out with the hybrid two-level ONIOM (B3LYP/6-31G: PM3) method. A detailed interpretation of the infrared spectra of Lupeol and Lupenone is also reported in the present work. The similarities and differences between the vibrational spectra of the two molecules studied have been highlighted. The scaled theoretical wave numbers are in perfect agreement with the experimental values. The thermodynamic calculations related to the title compounds were also performed at B3LYP/6-31G: PM3 level of theory. Quantum chemical calculations have been carried out to understand the dynamical behavior of the bioactive molecules Lupeol and Lupenone.
This work used dispersive Raman spectroscopy to evaluate acetaminophen in commercially available formulations as an analytical methodology for quality control in the pharmaceutical industry. Raman spectra were collected using a near-infrared dispersive Raman spectrometer (830 nm, 50 mW, 20 s exposure time) coupled to a fiber optic probe. Solutions of acetaminophen diluted in excipient (70 to 120% of the commercial concentration of 200 mg/mL) were used to develop a calibration model based on partial least squares (PLSs) applied to Raman spectra of solutions and, subsequently, obtain linearity, accuracy, precision (repeatability), and sensitivity of the method using the near-infrared spectroscopy (NIRS) as a gold standard method. This model was used to predict the acetaminophen concentration in commercial samples from different lots of acetaminophen formulations (200 mg/mL) with a PLS-prediction error of about 0.6%. Commercial medicines had PLS predicted concentrations errors below 2.5%, whereas NIRS had an error of about 3.7% compared to the label concentration. It has been demonstrated the applicability of Raman spectroscopy with fiber probe for quality control in pharmaceutical industry of commercial formulations.
