UV Absorption Spectrophotometry Research Articles

Design, synthesis, biological evaluation and multi spectroscopic studies of novel 2-styrylquinoline-carboxamide derivatives as potential DNA intercalating anticancer agents.

In this study, novel 2-styrylquinoline derivatives possessing a planar aromatic system and a flexible side chain with an amino substituent were designed and synthesized as DNA-intercalating antitumor agents. The cytotoxic activity of the synthesized compounds was evaluated against four cancer cell lines including MCF-7 (breast cancer cells), A549 (lung epithelial cancer cells), HCT116 (colon cancer cells) and normal cell line L929 (mouse fibroblast cell line). The results displayed that the anti-cancer activity of the target quinolines is sensitive to the lipophilic nature of the C-6 and C-7 quinoline substituents. The anticancer activity of most of the target quinolines against MCF-7 and A549 cells was more than those of HCT116. Compound 3h possessing two methyl groups at the C-6 and C-7 of quinoline ring displayed the most cytotoxicity with IC50 value of 5.7µM against A549 cancer cells. Interaction of compound 3h with calf thymus DNA (ctDNA) was investigated by means of UV absorption spectrophotometry, fluorescence spectroscopy, circular dichroism (CD), Resonance light scattering (RLS), viscos metric techniques and also by docking and molecular dynamic studies. RLS intensity, fluorescence quenching of ctDNA and fluorescence quenching EtBr-ctDNA and AO-ctDNA complexes augmented with increasing of compound 3h concentration, significant increasing in viscosity and melting point of ctDNA in the presence of compound 3h, absorbance increasing of ctDNA-compound 3h complex by increasing of NaCl and KI concentrations, higher Ksv value for dsctDNA (3.03×104 M-1) compared to ssctDNA (1.31×104 M-1), circular dichroism (CD) studies, docking and molecular dynamic studies revealed that compound 3h can interact with ctDNA through intercalation into DNA.

Study of the Photodegradation Kinetics of Fluometuron by UV Absorption Spectrophotometry and Fluorescence

In order to predict the fate of fluometuron in the aquatic environment and to assess the risk that it may pose, we studied its photolysis reaction in aqueous media. This reaction was monitored by UV absorption and fluorescence spectroscopy. UV irradiation source consisting of a 254 nm mercury lamp was used. The study showed that fluometuron is unstable under the effect of light radiation when irradiated in water. The absorption band and the emission of this product were at 244 nm and 325 nm respectively. This study also shows that the photodegradation of fluometuron in water follows first order kinetics regardless of the method followed. However, a difference was noted in the half-life times (t1/2). Indeed, these times found in UV and fluorescence are respectively 18.2 min and 6.6 min. The relatively lower value obtained in fluorescence could be explained by the fact that the latter is more sensitive to UV and fluorescence. In all cases, the half-lives found were relatively short (t1/2<1h). For more information on the photolysis of this herbicide, these two methods were combined with NMR and GC-MS to identify the different photoproducts that may be formed.

A simple and efficient method for simultaneous quantification of levodopa and carbidopa based on controlled oxidation process

Levodopa (L-dopa) and carbidopa (C-dopa) are used for the treatment of the Parkinson’s disease. In the present work, an experimental and theoretical investigation about oxidation process of these drugs was able to provide the optimal conditions of an efficient analytical method for simultaneous quantification of L-dopa and C-dopa in pharmaceutical preparations. The theoretical results, based on density functional theory (DFT), have shown good agreement with the experimental UV–Vis findings, thus providing new insights into the oxidation mechanisms of these drugs. The analytical procedure is based on the controlled oxidation of these drugs, with further quantification using UV absorption spectrophotometry. The present method has been validated, showing good linearity over the ranges of 3.88–42.68 µg mL−1 for L-dopa and 2.2–11.00 µg mL−1 for C-dopa. Precision measures were satisfactory with the relative standard deviation values lower than 2.31% in all analytical tests; accuracy was verified by recovery studies and also by method comparison, showing excellent results. Mean of recoveries was within the acceptable limits of 96.14–101.84% for both drugs. The proposed method showed to be selective at pH 13.5 allowing the determination of both drugs without interference spectral to each other or from excipients of the Parkidopa®, pharmaceutical preparation studied in this work. The present method represents an interesting, rapid, inexpensive and environmentally friendly alternative method for the quality control analysis of this pharmaceutical preparation.

Competitive Adsorption on Nanomaterials for Human Papillomavirus 16 L1 Protein Sensitive Detection

Human papillomavirus (HPV) L1 protein is a biomarker of HPV infection. The identification of HPV L1 protein provides valuable information regarding the viral infection status, reflect the status of HPV virus replication in cervical cells, and help understand cervical lesions Fade and progress. Graphene oxide is an important nanomaterial. Owing to the optical properties of graphene oxide (GO) itself and the interaction between GO and HPV16 L1 nucleic acid aptamer, we established a method for quantitative detection of HPV16 L1 protein by UV absorption spectrophotometry. The recovery rate of the method is 87%–102%, and the limit of detection is 2 pg/mL. We analyzed the HPV16 L1 protein quantitatively in clinical samples by adopting this method. The current method is simple and has promising reliability and profound sensitivity.

Low-volume PEEK gas cell for BTEX detection using portable deep-UV absorption spectrophotometry.

Monitoring of indoor air quality by detecting individual airborne pollutant is essential for maintaining a healthy indoor environment. UV absorption spectrophotometry coupled with gas chromatography offers a reliable, self-referenced and non-destructive technique for the identification and detection of gas molecules. This paper presents a deep-UV absorption spectrophotometer coupled with a micro gas-chromatography (μGC) for the detection of benzene, toluene, ethylbenzene and xylenes (BTEX). The spectrophotometer was developed using a low-volume gas cell made of PolyEther Ether Ketone (PEEK) polymer tube, connected with a portable deep-UV LED and photomultiplier tube. The performance of the detection unit was evaluated with different concentrations of toluene (5-100ppm) in nitrogen and a sensitivity of 107.1μAU/ppm with a limit of detection of 1.41ppm was obtained. The detector was incorporated into a micro gas-chromatography setup and high quality chromatograms, having all the peaks separated with good repeatability were obtained for BTEX molecules. The deep-UV absorption spectrophotometer has low-volume, low-cost, and ease of development and integration. While demonstrated for BTEX in a nitrogen carrier gas, the spectrometer has the potential to be applied to chromatographic analysis of different analytes in gas or liquid media.

Use of solid phase extraction for sample clean-up and preconcentration of vitamin B12 in multivitamin tablet before HPLC-UV, UV and atomic absorption spectrophotometry

A solid phase extraction method for sample clean-up and preconcentration of vitamin B12 in multivitamin tablet and its determination by HPLC-UV, UV and atomic absorption spectrophotometry is reported. Solid phase parameters such as maximum loading capacity and breakthrough volume were 400 μg and 1750 mL of 0.001 ppm for this vitamin respectively. A proper mobile phase used for HPLC was water/acetonitrile (75:25, v/v) with pH = 3.5 (adjusted with acetate buffer) at 25°C. Limit of detection and linear dynamic range for HPLC, UV and atomic absorption were 0.1, 0.1-25.0; 0.4, 0.4 -15.0; 2.7, 2.7-300.0 (μg/mL) respectively. Recovery of vitamin B12 was about 96%.

Assignment of complex species by affinity capillary electrophoresis: The case of Th(IV)-desferrioxamine B.

The electrophoretic mobility change of desferrioxamine B (DFO) was monitored by UV absorption spectrophotometry upon increasing the thorium(IV) concentration in the background electrolyte at two acidities ([HClO4 ]Tot = 0.0316 and 0.0100 M). These data enabled to assess the speciation model and to determine the equilibrium constant of [Th(DFO)H2 ]3+ at fixed ionic strength (I = 0.1 M (H,Na)ClO4 ). Affinity capillary electrophoresis (ACE) turned out to be most helpful in identifying the complexed species by ascertaining its charge and protonation state. The assignment of the correct stoichiometry relied on the reliable estimation of the electrophoretic mobility by assuming similar hydrodynamic radii for (DFO)H4+ and the chelate. The value of the apparent equilibrium constant (log β112 = 38.7±0.4) obtained by ACE compares favorably well with those reported in the literature for thorium and a range of other metal ions, according to a linear free-energy relationship. This method is useful for studying metal-ligand binding equilibria and provides valuable information for further modelling the behavior of tetravalent actinides under environmental conditions. Structural information about the prevalent solution species in acidic conditions was gained by DFT calculations, confirming the bishydroxamato coordination mode of Th4+ by the diprotonated ligand.

Validation of Spectrophotometric Method for Determination of Thiamazole in Liquids by Dissolution Test for the Transdermal Form

The purpose of this work was to validate the method of UV absorption spectrophotometry for the determination of thiamazole in transdermal patches during their pharmaceutical development. According to the pharmacopoeial requirements of the Republic of Kazakhstan, dissolution test was used to assess the quality of drug product. Measuring the optical density of thiamazole solutions at a wavelength of 252 nm in the range of concentrations from 0.005 to 0.04 mg/mL showed that the optimal test solution concentration is 0.005 mg/mL. The proposed method was validated through the standard and drug recovery method for linearity, range, accuracy and precision. Optimized and validated, it demonstrated high specificity and accuracy for transdermal patch with thiamazole. The obtained results proved that the method could be used for routine analysis as well as for pharmaceutical development and quality control for thiamazole patches.

Extraction, derivatization and antioxidant activity of cucumber polysaccharide

The aim of this study was to investigate the effects of derivatization on the antioxidant activity of cucumber polysaccharide. Cucumber polysaccharide was extracted with hot water, and then modified by carboxymethylation and sulfation, respectively. The structures of cucumber polysaccharide and its derivatives were characterized by FT-IR and 13C NMR. The content and substitution degree of cucumber polysaccharide and its derivatives were determined by UV absorption spectrophotometry. Antioxidant activities of cucumber polysaccharide and its derivatives were determined by hydroxyl radical scavenging ability and iron ion reducing ability. The results showed that the content of cucumber polysaccharide and its derivatives was 20.60%, 44.07% and 31.20% respectively, and the substitution degree of carboxymethylated and sulfated cucumber polysaccharide was 0.18 and 0.65, respectively. Cucumber polysaccharide itself had strong hydroxyl radical scavenging ability (80%) and reducing ability, and it had high antioxidant activity, while the carboxymethylation and sulfation modification of cucumber polysaccharide reduced its antioxidant activity.

Interaction of pesticide pyroquilon with two different cucurbit[n]uril

In this work, we report a conceptual strategy for preventing pesticide degradation using cucurbit[n]uril to encapsulate pyroquilon (Pyn). The host–guest inclusion complexes of pyroquilon (Pyn) with CB[7] and CB[8] were prepared and characterized using 1H NMR spectroscopy, quadrupole-time of flight mass spectrometry (Q-TOF), isothermal titration calorimetry (ITC) and UV absorbance spectrophotometry. The experimental results revealed that the entire Pyn molecule resides within the cavities of CB[7] and CB[8], forming 1:1 inclusion complexes between CB[n] and Pyn. Our study on the release of Pyn demonstrated that CB[n]@Pyn exhibit sustained- and slow-release properties. Moreover, CB[8] can effectively shield UV irradiation and thereby protect the Pyn from photodegradation. Therefore, CB[7]@Pyn and CB[8]@Pyn have great potential to be used as slow-release agents.

Quantitative Analysis of Ciprofloxacin in an Ophthalmic Solution Using UV Absorption Spectrophotometry and Derivative Spectrophotometry

The quantitative analysis of ciprofloxacin in an ophthalmic solution was performed by UV absorption spectrophotometry and first derivative spectrophotometry. The UV absorption spectra of standard series and samples containing ciprofloxacin were recorded. Then, the derivative of UV absorption spectra was obtained for the derivative spectrophotometric analysis of the related drug. Linear regression equations in the linear concentration range of 3.0-28.0 µg/mL for analysis of ciprofloxacin were obtained by using direct absorbance measurement at 278.9 nm and using the dA/dλ values at 283.2 nm. The recovery assay results were found between 97.8 to 102.0 %. It was observed that the limits of detection and quantification were 0.74 and 2.74 μg/mL for UV absorption spectrophotometry and 0.60 and 2.00 μg/mL for first derivative spectrophotometry, respectively. Analysis results indicated that the proposed methods were precise, accurate and reliable for the determination of ciprofloxacin in commercial samples.

Development of a Toluene Detector Based on Deep UV Absorption Spectrophotometry Using Glass and Aluminum Capillary Tube Gas Cells with a LED Source.

A simple deep-ultraviolet (UV) absorption spectrophotometer based on ultraviolet light-emitting diode (UV LED) was developed for the detection of air-borne toluene with a good sensitivity. A fiber-coupled deep UV-LED was employed as a light source, and a spectrometer was used as a detector with a gas cell in between. 3D printed opto-fluidics connectors were designed to integrate the gas flow with UV light. Two types of hollow core waveguides (HCW) were tested as gas cells: a glass capillary tube with aluminum-coated inner walls and an aluminum capillary tube. The setup was tested for different toluene concentrations (10–100 ppm), and a linear relationship was observed with sensitivities of 0.20 mA·U/ppm and 0.32 mA·U/ppm for the glass and aluminum HCWs, respectively. The corresponding limits of detection were found to be 8.1 ppm and 12.4 ppm, respectively.

Water characterization and early contamination detection in highly varying stochastic background water, based on Machine Learning methodology for processing real-time UV-Spectrophotometry

Water is a resource that affects every aspect of life. Intentional (terrorist or wartime events) or accidental water contamination events could have a tremendous impact on public health, behavior and morale. Quick detection of such events can mitigate their effects and reduce the potential damage. Continuous on-line monitoring is the first line of defense for reducing contamination associated damage. One of the available tools for such detection is the UV-absorbance spectrophotometry, where the absorbance spectra are compared against a set of normal and contaminated water fingerprints. However, as there are many factors at play that affect this comparison, it is an elusive and tedious task. Further, the comparison against a set of known fingerprints is futile when the water in the supply system are a mix, with varying proportions, of water from different sources, which differ significantly in their physicochemical characteristics. This study presents a new scheme for early detection of contamination events through UV absorbance under unknown routine conditions. The detection mechanism is based on a new affinity measure, Fitness, and a procedure similar to Gram based amplification, which result in a flexible mechanism to alert if a contamination is present. The method was shown to be most effective when applied to a set of comprehensive experiments, which examined the absorbance of various contaminants in drinking water in lab and real-life configurations. Four datasets, which contained real readings from either laboratory experiments or monitoring station of an operational water supply system were used. To extend the testbed even further, an artificial dataset, simulating a vast array of proportions between specific water sources is also presented. The results show, that for all datasets, high detection rates, while maintaining low levels of false alarms, were obtained by the algorithm.

Determination of Methimazole in Tablets Using Spectrophotometric Methods

This study describes the spectrophotometric quantification of methimazole in tablets using zero-order absorption spectrophotometry and first derivative spectrophotometry methods. In preliminary experiments, linearity range was found between 2.0-24.0 µg/mL in zero-order spectrophotometry and first-order derivative spectrophotometry. Calibration curves were obtained by measurements of the zero-order absorbances and their first derivative values at 260.0 and 269.0 nm for the zero-order spectrophotometry and first derivative spectrophotometry, respectively. The recovery and relative standard deviations were calculated as 103.3 % and 2.18 % for UV absorption spectrophotometry and 98.0% and 0.64% for first derivative spectrophotometry, respectively. The proposed techniques were used for the analysis of tablets preparations. The methods proposed in this study were verified by analyzing validation test samples containing methimazole. Determination results showed that the applied methods were found to suitable for the quantitation of the related drug.

Study the Interaction between Gold Nanoparticles and Bovine Serum Albumin: Spectroscopic Approach

Interaction between gold nanoparticles of 40 & 60 nm with BSA has been investigated using UV-absorption spectrophotometry, fluorescence spectroscopy and FT-IR spectroscopy. UV-absorption spectrophotometry showed an increase in the absorption intensity with increasing the molecular ratios of gold nanoparticles of both sizes to BSA, it is found that the value of the binding constant is estimated to be 0.888 × 104 M-1 for gold nanoparticles (40 nm)- BSA complexes, and 1.16 × 104 M-1 for gold nanoparticles (60 nm)-BSA complexes. FT-IR spectroscopy analysis showed that intensities of gold nanoparticles of both sizes-BSA complexes decrease as the concentration increased.

Accurate Quantification of Nucleic Acids Using Hypochromicity Measurements in Conjunction with UV Spectrophotometry.

UV absorbance spectrophotometry is widely used for the quantification of nucleic acids. For accurate quantification, it is important to determine the hypochromicity of the oligonucleotide or complex nucleic acid structure. The use of thermal denaturation studies in conjunction with UV spectrophotometry to determine hypochromicity requires prolonged, elevated temperatures, which may cause partial hydrolysis of RNA. In addition, dsRNA is difficult to denature even at elevated temperature, and the extinction coefficients of nucleic acids are also affected by temperature, which makes it difficult to accurately determine the nucleic acid concentration. To overcome these caveats, we have utilized the chemical denaturant dimethyl sulfoxide which, in conjunction with a short thermal denaturation, prevents renaturation of the duplex nucleic acids (dsDNA/RNA). Using this approach, we have measured the absorbance of both the unstructured and structured nucleic acids to accurately measure their hypochromicity and determine their extinction coefficients. For a range of different dsRNA, we have for the first time determined values of 46.18-47.29 μg/mL/A260 for the quantification of dsRNA using UV spectrophotometry. Moreover, this approach enables the accurate determination of the relative proportion of duplex nucleic acids in mixed ds/ss nucleic acid solutions, demonstrating significant advantages over current methods.

Ligand Exchange Reactions of a Monomeric Zirconium Carbonate Complex with Carboxylic Acids Studied by Extended X-ray Absorption Fine Structure, UV Absorption and Raman Spectrophotometry.

Ligand exchange reactions of a monomeric zirconium carbonate complex with carboxylic acids were studied by means of extended X-ray absorption fine structure (EXAFS), UV absorption spectrophotometry and Raman spectrometry. Three carboxylic acids, gluconic acid, and L-tartaric acid and citric acid, which are mono-, di- and tri-carboxylic acids, respectively, were employed in this study. These three carboxylic acids gave different spectral signatures and concentration dependences, respectively. In the gluconic acid system, the peaks on Fourier transform of EXAFS spectrum and Raman spectrum caused by carbonate ion coordinating to zirconium atom were obviously decreased with increasing gluconic acid concentration compared to the other two carboxylic acid systems. This indicates the high association ability of gluconic acid to zirconium, which was revealed by UV spectrophotometric analysis.

Supramolecular assemblies of moroxydine hydrochloride and cucurbit[7,8]uril

Complexes of moroxydine hydrochloride (ABOB) with cucurbit[n]urils (n = 7 or 8) were investigated using 1H NMR spectroscopy, Quadrupole-Time of Flight mass spectrometry (Q-TOF), UV absorbance spectrophotometry, isothermal titration calorimetry (ITC), and X-ray crystallography. Experimental results revealed that the morpholino group of ABOB resides within the cavity of Q[7] and Q[8] respectively in both aqueous solution and solid state. In aqueous solution, 1:1 inclusion complexes of ABOB and Q[7,8] are formed with moderate binding constants. In the solid state, the cavity of Q[8] encapsulates two ABOB morpholine groups to generate a novel 2ABOB@Q[8] inclusion complex.

Investigation on the Binding Mode of 3, 4-Dihydropyrano[c]Chromene Derivative with Double Strand DNA.

The study on the interaction between small molecules and DNA has been very useful for investigating the structure and physical properties of DNA, elucidating the damage mechanism of DNA and significant in the design of new drugs targeted to DNA. This article describes an interaction of native calf thymus DNA (ctDNA) with a new 3, 4-dihydropyrano[c]chromene derivative, 2-amino-4-(4- chlorophenyl)-5-oxo-4H, 5H-pyrano-[3, 2-c] chromene-3-carbonitrile (4-CC) by using spectroscopic and viscometric techniques. The interaction between 4-CC and ctDNA is realized from the UV absorption spectrophotometry, viscosimetry, circular dichroism and fluorescence spectroscopic techniques which shows that the successive interaction of 4-CC with ctDNA occurs. The experimental results revealed that 4-CC can interact with DNA through non- intercalative mode and the intrinsic binding constant (Kb) for 4-CC with DNA was estimated to 2.37 (±0.001) ×103 M-1. Methylene blue (MB) displacement studies revealed that 4-CC did not have any effect on MB bound DNA which is indicative of groove binding mode. Furthermore, 4-CC induces detectable changes in the CD spectrum of ctDNA as well as changes in its viscosity study corroborate the above experimental results. These results further advance our knowledge on the molecular aspects on the interaction of 4-CC to nucleic acids.

Studies of interaction between terbium(III)-deferasirox and double helix DNA by spectral and electrochemical methods

DNA binding studies of terbium(III)-deferasirox (Tb3+-DFX) complex were monitored to understand the reaction mechanism and introduce a new probe for the assay of DNA. In the present work, UV absorption spectrophotometry, fluorescence spectroscopy, circular dichroism (CD), cyclic voltammetry (CV) and viscosity measurement were employed to study the interactions of Tb3+-DFX with calf thymus DNA (ctDNA). The binding of Tb3+-DFX complex to ctDNA showed a hyperchromic effect in the absorption spectra and the increase in fluorescence quenching effect (amount) of Tb3+-DFX complex in the presence of ctDNA. The binding constants (Kb) for the complex with ctDNA were estimated to be 1.8×104M−1 through UV absorption spectrophotometry and fluorescence spectroscopy. Upon addition of the complex, clear decreases were observed in the viscosity of ctDNA. The CD spectra indicated that there are certain detectable conformational changes in the DNA double helix when the complex was added. The CV method showed that both anodic and cathodic peak potentials of Tb3+-DFX complex showed negative shifts on the addition of the ctDNA. Further, competitive methylene blue binding studies with fluorescence spectroscopy have shown that the complex can bind to ctDNA through nonintercalative mode. The experimental results suggest that Tb3+-DFX complex binds to DNA via groove binding and/or electrostatic binding mode.