UV-vis Fluorescence Research Articles

Toxicity assessment of carmine and its interaction with calf thymus DNA

Carmine (CRM) is a colouring agent, extensively used in a variety of foods, beverages, cosmetics and pharmaceuticals. A battery of in vitro toxicity tests and chemical interaction studies of CRM with calf thymus DNA (ctDNA) have been conducted. Hemolysis assay clearly revealed the cytotoxic potential of CRM while Allium cepa and seed germination tests for phytotoxicity of CRM were also positive. DNA binding studies withplasmid nicking assay, clearly affirmed the genotoxic potential of CRM. The formation of CRM–ctDNA complex was suggested by UV-visible absorption and fluorescence spectra. The binding constant of CRM–ctDNA complex determined by ITC was found to be 1.72 x 106 M −1. It also revealed the negative ΔH and ΔS values, indicating the role of hydrogen bonds and Van der Waals interactions in the formation of CRM–ctDNA complex. A remarkable (43.4%) displacement of Hoechst as compared to acridine orange (100%) suggests probable disruption of groove which might be possible due to the large size of CRM. Intercalatory mode of CRM binding was further confirmed by significant increase in double helix melting temperature of ctDNA and changes it's in circular dichroism spectra. Molecular docking also supported the notion that DNA binding involved both modes i.e. intercalatory as well as groove binding; moreover, it is consistent with the binding energies determined from ITC. In a nutshell, CRM is significantly cytotoxic to human and plant systems with its remarkable genotoxic potential too, wherein it targets DNA as a partial intercalator and ultimately break its backbone. Communicated by Ramaswamy H. Sarma

Synthesis of zinc oxide nanostructures using orange peel oil for fabricating chitosan-zinc oxide composite films and their antibacterial activity

There is growing need for environmentally friendly plastics to tackle problems of waste disposal. This makes it important to explore options to make biodegradable materials for packaging and coating applications. In this study we have leveraged the inherent anti-bacterial, biodegradable properties of chitosan (CS) and anti-bacterial and UV-absorbing properties of Zinc Oxide (ZnO) to develop CS-ZnO composite films. ZnO nanostructures (ZnO NS) were synthesized using orange peel oil (OP) by green chemical reduction method. ZnO incorporated films of chitosan were evaluated for their physicochemical properties. Presence of ZnO NS was confirmed using its characteristic signatures in UV-Visible spectrum, fluorescence measurement and FT-IR spectrum. The ZnO NS gave absorption and fluorescence maxima at 379 nm and 465 nm respectively. FT-IR spectra confirmed the vibration of the Zn-O at ~470 cm−1. The composite films prevented moisture permeability as compared to plain chitosan films. Chitosan-ZnO composite films showed higher tensile strength than plain chitosan films and also selectively blocked radiations in UV region due to UV-absorbing property of ZnO. The composite films also demonstrated good adhesion on glass and polystyrene substrates, enhanced tensile strength and anti-bacterial activity against E.Coli, compared to CS films, suggesting the potential of the developed films as a biodegradable, coating and packaging material.

Variation in spectral characteristics of dissolved organic matter derived from rape straw of plants grown in Se-amended soil

Straw return is an effective management practice. It not only utilizes agricultural waste but also introduces dissolved organic matter (DOM) into the soil. Selenium (Se) is an essential trace element in the human diet and contributes to the popularity of Se-enriched agricultural products in the Chinese market. Moreover, there are still some Se-enriched agricultural products that have yet to be utilized. This study investigated whether Se addition in soil caused component changes in the DOM extracted from rape straw. DOM extracted from rape straw grown in soil with four Se levels (0, 0.1, 0.5 and 1.0 mg Se kg−1 soil) was characterized by UV-Visible spectroscopy, fluorescence spectroscopy and FTIR spectroscopy. The UV-visible spectra revealed that 0.1 mg Se kg−1 soil reduced the molecular weight of DOM and caused the presence of more irreplaceable aromatic structures in the substituent groups of the DOM, while 0.5 and 1.0 mg Se kg−1 soil only reduced the DOM molecular weight. Fluorescence spectroscopy indicated that Se improved the humification degree but reduced the aromaticity of DOM. FTIR spectra proved that Se altered the contents of carboxylic acids, amino acids, alcohols and aromatic heterocycles in DOM, which were maximized in the 0.5 and 1.0 mg Se kg−1 treatment groups. We concluded that Se application could change the composition of DOM extracted from rape straw, potentially impacting the nutrient bioavailability in soil. This study provides basic data on Se-enriched rape straw utilization for eco-agriculture.

Distribution Characteristics and Influencing Factors of Chromophoric Dissolved Organic Matter in a Northern-Side River of the Qinling Mountains in Summer

UV-visible absorption spectroscopy, fluorescence spectroscopy, and parallel factor analysis were used to analyze the composition of chromophoric dissolved organic matter (CDOM) in the waters of the Wangchuan River in summer, and the source of this CDOM was explored. The redundant analysis method and Pearson correlation were used to analyze the correlation between optical parameters and water quality parameters. The results showed that the CDOM of the Wangchuan River is composed of the tryptophan-like component C1 (245, 300/335 nm), the short-wave humus component C2 (240, 320-340/405 nm), and the long-wave humus component C3 (270, 350-370/470 nm), in which components C1 and C2 have some homology (r=0.859, P<0.001). CDOM absorption coefficient α(355) indicates that the CDOM concentration in the water body of the Wangchuan River is at a low level, and the correlation between α(355) and DOC concentration is significant (r=0.850, P<0.001), which is conducive to the establishment of a DOC inversion model. Water fluorescence index FI (2.36±0.20), HIX (3.66±2.47), BIX (1.56±0.82), and freshness index (β:α) (1.33±0.62), and the spectral slope ratio SR (0.76±0.25) indicate that the CDOM of the Wangchuan River has strong self-generated characteristics, weak humification characteristics, and more new CDOM. Redundancy analysis showed that the humic components (C2, C3) are affected by algae metabolism and microbial action, while tryptophan-like components (C1) are related to land-based input, and negatively correlated with dissolved total nitrogen. The humic components C2 and C3 are positively correlated with total phosphorus, dissolved total phosphorus, and dissolved organic carbon. This paper clarifies the characteristics and influencing factors of CDOM in the Qinling valley, and provides a theoretical basis for water body management in the Qinling valley.

Simple and fast diagnosis of osteoporosis based on UV-visible hair fluorescence spectroscopy

The aim of this work is to propose a new analytical technique based on UV-visible fluorescence as an alternative to x-ray absorptiometry for diagnosing osteoporosis, as well as its early stage by identifying osteopenia. The equipment used consists of very cheap equipment compared to x-ray scanners with an LED as the excitation source. In this work, we analyzed 90 hair samples taken from volunteers of different ages at Habib Thameur Hospital in Tunis. These samples were previously analyzed by bone mineral density (BMD) and correspond to people suffering from osteoporosis and osteopenia, as well as healthy people. The main idea of this study is to show the correlation between the deficiency of bone density given by BMD and the variations of the relative concentrations of molecules present in the hair causing the changes observed in the fluorescence spectra. The results extracted from the spectra show a clear discrimination between healthy and sick patients and a very good correlation, in a Spearman sense, between the spectral measurements and the BMD's data for the patients with osteoporosis. In addition, we have isolated the main spectral region responsible for this correlation, which facilitates the identification of the molecule concentrations related to the decrease in BMD.

Fluorescent ZnO Quantum Dot Probe to Study Glucose–Glucose Oxidase Interaction via Fluorescence Resonance Energy Transfer

In this work, emphasis is to utilize FRET method to analyze GOx and glucose interaction using fluorescent ZnO QDs as the probes. Fluorescent ZnO and ZnOext QDs were synthesized using sol– gel technique and green synthesis method as donor and acceptor nanoprobes. Structural, optical and morphological characterization of QDS were carried out using UV-visible absorption, fluorescence, FTIR, XRD and field emission scanning electron microscopy. Band gap estimated from Tauc plot is 3.49 and 3.35 eV for ZnO and ZnOext QDs and XRD reveal Wurtzite structure of grown crystals. Systematic absorption study for ZnO–GOx and ZnOext–GOx reveal association constant of –8.3361 M–1 and –2.57646 M –1 for ZnO and ZnOext using Benesi-Hildebrand plot. The binding constant obtained from Stern-Volmer equation is 1.0466 μM –1 and 1.97 μM –1 for ZnO/ZnOext–GOx conjugate and suggest static quenching in the system. CD spectroscopy reveal native state of protein in conjugate sytem. Constant Förster radius (Ro) in ZnOext–GOx system suggest the average 〈κ2〉 as 2/3 and is independent of donor–acceptor distance as normally assumed in FRET system varies from ∼4.5% in ZnO–GOx and ∼5% in ZnOext–GOx system. It indicate better energy transferrin earlier system than formal. The physiological range of glucose from 60 mg–440 mg/dl using this technique in which ZnOext–GOx as donor probe exhibit better response towards glucose than ZnO–GOx system and correlated to the presence of phyotochemicals on the QD surface.

A novel coumarin-derived acylhydrazone Schiff base gelator for synthesis of organogels and identification of Fe3.

A novel coumarin-derived acylhydrazone Schiff base fluorescent organogel (G1) was designed and synthesized. Gelator G1 can form stable organogels in isopropanol, tert-amyl alcohol, n-butanol and phenylamine. The organogel could be converted to solution by heating and the solution could be restored to gel state by cooling. The self-assemble mechanism of G1 was investigated by XRD, FT-IR and SEM techniques. The results indicated the intermolecular hydrogen bonding, Van der Waals interaction and π-π stacking are the forces for the self-assembly of the gelator to form the organogel. The optical properties of the compound were studied by UV-visible spectroscopy and fluorescence spectra. Further study presented that gelator G1 could selectively and sensitively response to Fe3+ only among tested cations. Beside the above functions, the organic gel factor G1 could also response to irradiation, heating and shaking, thus endowing the organogel with multi stimulus responsive properties.

Interaction between the Antimalarial Drug Dispiro-Tetraoxanes and Human Serum Albumin: A Combined Study with Spectroscopic Methods and Computational Studies.

Dispiro-tetraoxanes, a class of fully synthetic peroxides which can be used as an antiplasmodial remedy for multiple drug-resistant strains of Plasmodium falciparum, were selected for the interaction study with human serum albumin (HSA). The insight into the interaction of the two chemically synthesized, most potent antimalarial tetraoxane analogues (TO1 and TO2) and HSA has been scrutinized using distinct spectroscopic techniques such as. UV–visible absorption, fluorescence, time-resolved fluorescence, and circular dichroism (CD). Fluorescence quenching experiments divulged the static mode of quenching and binding constants obtained (∼104) indicated the moderate affinity of the analogues to HSA. CD confirmed the conformational changes in the serum albumin upon interaction with these analogues. Molecular docking validated the empirical results as these two analogues bind through hydrophobic interactions and hydrogen bonding with HSA. Present work first defined the binding mechanism of dispiro-tetraoxanes with HSA and thus provides a fresh insight into the drug transportation and metabolism. The present study could direct toward designing more potent tetraoxane analogues for their use in the biomedical field.

Spatiotemporal variations of DOM components in the Kushiro River impacted by a wetland.

Dissolved organic matter (DOM) has been recognized as a serious water quality problem in natural water bodies receiving pollution loads from point and nonpoint sources. The present study investigates the spatiotemporal variability of DOM composition in the Kushiro River and its tributaries (Eastern Hokkaido, Japan) impacted by the Kushiro wetland. Water samples were collected in the wet and dry seasons from several locations of the river and analyzed for DOM characteristics by UV-visible and excitation-emission matrix fluorescence spectroscopy techniques and by developing water quality index. Rather than the spatial effect, significant seasonal impacts on DOM pollution in the Kushiro River were observed. Overall concentrations of DOM decreased during the dry season. The increase of specific ultraviolet absorbance in the dry season indicated an increasing trend of humification, aromaticity and molecular weight of DOM. Five fluorescent peaks, including peaks A, C, M, B, and T were predicted by EEM spectra. Peaks A and C were found to be the most dominating peaks in both the seasons and indicated enrichment of humic-like matters in river water. The intensities of poly-aromatic humic substances as well as DOM components of microbial origin increase in the wet season and proteins like autochthonous DOM increase during the dry season. The study recognized the contribution of freshly produced DOM component by the decomposition of wetland plants in wet season and effect of snowfall in the dry season. Analysis of three fluorescence indices revealed that the river water primarily contains terrestrially dominated DOM. A significant impact of the adjacent WWTPs and wetland to the river water DOM were also observed. The water quality index of river water DOM showed low to medium levels of DOM pollution in the Kushiro River.

Effects of multiwalled carbon nanotubes on the dissolved organic matter released by Prorocentrum donghaiense: Results of spectroscopic studies.

Many reports have investigated the effects of carbon nanotubes (CNTs) on the properties of terrestrial dissolved organic matter (DOM), which could significantly altered its binding affinity for contaminants. However, the effects of CNTs on algogenic DOM are largely unknown. To address this issue, the properties of algogenic DOM released by Prorocentrum donghaiense (P. donghaiense-DOM) under the stress from 0.1 to 10.0mg/L graphitized multiwalled CNTs were nondestructively characterized by the use of UV-visible absorption and fluorescence excitation-emission matrices with parallel factor analysis. The results showed that the changes in the properties of P. donghaiense-DOM were highly dependent on the CNTs concentration. The properties of P. donghaiense-DOM under 0.1mg/L CNTs treatment showed no obvious differences compared to the control. The addition of 0.5-10.0mg/L CNTs changed the release pathways of P. donghaiense-DOM, resulting in significant alterations to the properties of P. donghaiense-DOM. The aromaticity, molecular weight, protein-like and humic-like components were enhanced under stress from 0.5 to 1.0mg/L CNTs on day 4, which can be ascribed to the overproduction of extracellular DOM (EDOM) that occurred in response to the significant increase in intracellular ROS levels. CNTs at 5.0 and 10.0mg/L significantly induced membrane damage to P. donghaiense on day 4, which led to the leakage of intracellular DOM (IDOM) and then increased the molecular weight and protein-like components but decreased the aromaticity and humic-like components. After the P. donghaiense recovered to its normal growth under 0.5-10.0mg/L CNTs treatments, the changes in the properties of P. donghaiense-DOM were attributed to the release pathways of P. donghaiense-DOM that were governed by the production of EDOM and the leakage of IDOM in the stationary and declining phases, respectively.

Protein binding and antioxidant studies of diimine based emissive surfactant–ruthenium(II) complexes

Biophysical interaction of amphiphilic fluorescent surfactant–ruthenium(II) complexes and its precursor ruthenium(II) complexes with drug carrying proteins such as bovine and human serum albumins (BSA and HSA) have been studied through the UV-visible absorption, fluorescence and circular dichroism spectroscopic techniques to correlate the impact of head and tail groups of the metallosurfactants towards the designing of metallodrugs for the biomedical applications. The obtained results showed that both precursor– and surfactant–ruthenium(II) complexes interact with BSA/HSA via ground state protein–complex formation and their quenching follows the static mechanism. The extent of protein quenching and binding parameters resulted that the surfactant–ruthenium(II) complexes effectively interact with protein compared to their precursor–ruthenium(II) complexes, and also those interaction have greatly influenced by the change in the head group size compared to change in the tail group length. Interestingly on increasing the temperature, the protein–complex binding strength was decreased for the precursor–ruthenium(II) complexes, those increased for the surfactant–ruthenium(II) complexes, probably due to the respective involvement of electrostatic and hydrophobic interactions as supported by the thermodynamics of protein–complex interaction. Moreover, the results from UV–visible, synchronous and circular dichroism studies confirmed the occurrence of conformational and micro environmental changes in BSA/HSA upon binding with these complexes. It is also noted that HSA has more binding affinity with surfactant–ruthenium(II) complexes compared to BSA. The free radical scavenging ability against DPPH, ABTS, NO and superoxide free radical assays suggested that surfactant–ruthenium(II) complexes have better free radical scavenging ability compared to precursor–ruthenium(II) complexes. Communicated by Ramaswamy H. Sarma.

Synthesis of Newer Mercury(II) Complexes of Meso-Tetraaryl-21,23-Dithiaporphyrins

Due to the larger size of hetero atom and poor binding with metals, N2X2 type of core modified porphyrins show lesser tendency to form metal complexes. Mercury(II) complexes of symmetrical and unsymmetrical meso-tetraaryl-21,23-dithiaporphyrins are synthesized and characterized by the reaction of corresponding meso-tetraaryl-21,23-dithiaporphyrins with mercuric acetate in chloroform/methanol. These mercury complexes are well characterized by their UV-Visible spectra, fluorescence spectra, 1H NMR, 13C NMR and elemental analysis. Soret bands of mercury complex of unsymmetrical 5,20-bis-(4′-methoxyphenyl)-10,15-bisphenyl-21,23-dithiaporphyrin appeared at 442 nm and 462 nm whereas Q band appeared at 516 nm, 560 nm, 620 nm and 714 nm. Appearance of four Q bands is characteristic for this mercury complex of N2X2 type of core modified porphyrins. Mercury complex of unsymmetrical 5,20-bis-(4′-methoxyphenyl)-10,15-bisphenyl-21,23dithiaporphyrin is an excellent fluorescent molecule and showed fluorescence spectrum at 722 nm. These core modified porphyrin complexes provides a good coordination examples of mercury complexes of 21,23-dithiaporphyrins that can be used in sensing applications.

Initiated Chemical Vapor Deposition of Crosslinked Organic Coatings for Controlling Gentamicin Delivery.

A coating consisting of a copolymer of methacrylic acid and ethylene glycol dimethacrylate was deposited over a gentamicin film by initiated chemical vapor deposition with the aim of controlling the drug release. Gentamicin release in water was monitored by means of conductance measurements and of UV-vis Fluorescence Spectroscopy. The influence of the polymer chemical composition, specifically of its crosslinking density, has been investigated as a tool to control the swelling behavior of the initiated chemical vapor deposition (iCVD) coating in water, and therefore its ability to release the drug. Agar diffusion test and microbroth dilution assays against Staphylococcus aureus and Pseudomonas aeruginosa on cellulose coated substrates confirmed that the antibacterial activity of the drug released by the coating was retained, though the release of gentamicin was not complete.

New cyclotriphosphazene ligand containing imidazole rings and its one-dimensional copper(II) coordination polymer

An imidazole and biphenyl-appended cyclotriphosphazene (2, L) and its 1D copper(II) coordination polymer (3) which formulated as [L2(CuCl2)]n were synthesized. The structure of 2 was determined by elemental analysis and different spectroscopic tecqniques. The crystal structures of 2 and 3 were defined by single-crystal X-ray crystallography. The copper atom in complex 3 was in a slightly distorted octahedral geometry which coordinated by four monodentate imidazole nitrogen and two chlorine atoms. The magnetic properties of 3 was discussed via ESR spectroscopy. The thermal properties of 2 and 3 were investigated by thermogravimetric analysis (TGA). The photophysical and electrochemical properties of 2 and 3 were evaluated by UV–Vis-fluorescence spectroscopies and cyclic (CV)-square wave (SWV) voltammetric techniques. In addition, HOMO-LUMO energy levels were calculated according to UV–Vis absorption and CV measurements.

Characterization of Libyan Cobra (Naja haje) Venom using Fluorescence and UV-Visible Spectroscopy

Snake venoms act as a preparative to defend animals against predators and helps in immobilizing and digestion of prey. Venoms consist of a combination of enzymes and toxins, such as metalloproteases, phospholipase A2, L-amino acid oxidase and toxins, including cytotoxins and neurotoxins. In addition to their toxicity, venom components exhibit several pharmacological activities and can be used as templates for drug design. The Libyan cobra venom was studied using UV-visible and fluorescence spectroscopic techniques. The cobra protein main chain absorbs light in the region of 240-340nm. The aromatic side-chains of cobra venom contain tyrosine, tryptophan and phenylalanine which are responsible for the absorbance in this region. Cobra venom provides intrinsic fluorescence emissions due to excitation of tryptophan residues, with some contribution from phenylalanine and tyrosine emissions. In addition, disulphide bridges contribute considerable absorption in this wavelength range. The main fluorescence obtained is due to tryptophan which has a wavelength of maximum absorption at 280 nm and an emission peak ranging from 310 to 350 nm. UV-visible absorption and fluorescence spectroscopic techniques are sensitive and rapid to study cobra venom in order to better comprehend the performance of this venom.

Investigating the mechanism of binding of nalidixic acid with deoxyribonucleic acid and serum albumin: a biophysical and molecular docking approaches

Nalidixic acid is a bacterial DNA gyrase inhibitor and the first member of the synthetic quinolone antibiotics. It is used in the treatment of various infectious diseases like urinary tract infections, respiratory infections, sexually transmitted diseases, acute bronchitis, and sinusitis. Interactions studies are of great significance as it will be beneficial for designing new therapeutic molecules with preferable plasma solubility and its efficacy. In this paper, we have aim to ascertain the binding mode of nalidixic acid with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) through various biophysical and in silico method. UV-visible absorption and fluorescence spectroscopic experiments confirmed the formation of a complex between nalidixic acid with ct-DNA. The binding constant is in the range of 103 M−1, indicating the groove binding mode between ct-DNA and nalidixic acid. Groove binding mode was also validated by competitive displacement assay, potassium iodide quenching experiment, circular dichroism, DNA melting studies. In the case of BSA, UV-visible absorption and fluorescence spectroscopic experiments confirmed the formation of a complex between nalidixic acid with BSA. The value of a binding constant in the case of BSA was found to be 1.517 × 105 M−1. The site marker displacement experiment revealed the binding location of nalidixic acid to a site I in BSA. Secondary structural and microenvironmental changes also studied through circular dichroism and three-dimensional fluorescence. Furthermore, the synchronous fluorescence spectra of BSA with nalidixic acid showed that there were changes in the microenvironment around tryptophan residues. In silico molecular docking further confirmed the binding of nalidixic acid to site I in BSA and the minor groove of DNA.Communicated by Ramaswamy H. Sarma

Interaction of carbon nanotubes with curcumin: Effect of temperature and pH on simultaneous static and dynamic fluorescence quenching of curcumin using carbon nanotubes.

Curcumin (Cur) has medicinal properties, undergoes hydrolysis, and has low water solubility that limits its bioavailability and industrial usage. Different host molecules such as carbon nanotubes (CNT) can be useful in improving solubility and stabilizing Cur, therefore understanding the interaction of Cur with host molecules such as CNT is crucial. In this study, UV-visible light absorption and fluorescence spectroscopic techniques have been applied to reveal the interaction of Cur with CNT. Visible light absorption of Cur increases with CNT concentration, whereas fluorescence intensity of Cur is quenched in the presence of CNT. The obtained results confirm that fluorescence reduction is due to both static and dynamic quenching and is a result of the ground state and excited-state complex formation. The pH environment influences the quenching rate due to deprotonation of Cur at higher pH; excess OH- ion concentration in the solution further discourages electrostatic interaction between the deprotonated form of Cur with CNT. It is found that at lower temperatures (<35°C) dynamic quenching is much more dominant and at higher temperatures (45°C) static quenching is more dominant. The interaction is further supported using X-ray diffraction patterns and Fourier transform infrared spectra in the solid state, and suggests encapsulation of curcumin within the CNT. It is further evident that fluorescence quenching of Cur using CNT is further enhanced in the presence of several salts, as increase in ionic strength of the solution pushes the hydrophobic Cur molecule towards the CNT core by increasing the proximity between them.

Synthesis, crystal structures, photophysical, electrochemical studies, DFT and TD-DFT calculations and Hirshfeld analysis of new 2,2′:6′,2′′-terpyridine ligands with pendant 4′-(trimethoxyphenyl) groups and their homoleptic ruthenium complexes

[Ru(L1)2](PF6)2 (1) and [Ru(L2)2](PF6)2 (2): X-ray structures, CH⋯F/O, OH⋯F/N, CH⋯O/π, π⋯π interactions, absorption and emission spectra, DFT/TD-DFT, Hirshfeld analysis.

Performance Comparison of Cost Efficient Natural Dye Sensitized Solar Cell

Dye-sensitized solar cells (DSSCs) enticed the attention in photovoltaic design due to their unique features of ease of fabrication, low-cost materials, tunable color, and flexibility. In this work, we studied the performance of a low cost dye-sensitized solar cell structure with several natural dyes as a sensitizer. Titanium dioxide (TiO2) was used as the semiconducting layer. The TiO2 film was fabricated on Florine doped Tin Oxide (FTO) glass plate and was annealed and sintered for an hour at 450°C temperature to create a mesoporous layer. To reduce the manufacturing cost, we used Carbon black instead of Platinum (Pt) as a counter electrode. Carbon black provides excellent stability and shows high catalytic ability along with its low cost as the counter electrode in the DSSCs. Eight different dyes have been extracted and purified by Silica gel column chromatography to use in the DSSCs. UV-Visible absorption spectroscopy and fluorescence spectroscopy has been done to measure the absorbance coefficient and fluorescence coefficient of each of the cells. The cells with an additional peak in the fluorescence spectra showed much better electrical performance compared with others. Among the fabricated DSSCs, the Curcuma longa based DSSC gives the highest open-circuit voltage of 0.5959 V and short circuit current density of 1.06 mA/cm2. The study also indicates that the dyes with a peak at 380 nm to 400 nm wavelength at fluorescence spectrum has better photovoltaic performance rather with a moderate absorbance spectrum.

Spectroscopic Studies on the Conformational Stability of Hemocyanin of Pila virens (Lamarck, 1822) in the Presence of Temperature and Detergents

Gastropods are endowed with a soluble copper containing, blue coloured respiratory protein known as hemocyanin. In the present study, for the first time, hemocyanin from Pila virens, a fresh water gastropod endemic to Indian sub-continent was studied for its conformational stability in the presence of temperature and various detergents by different spectroscopic techniques viz. UV–Vis, fluorescence and circular dichroism spectroscopy. Results from UV–Vis spectroscopy revealed that, absorbance corresponding to active site moieties were decreased with increase in temperature from 30 to 70 °C. Whereas ‘thermal reversibility’ studies showed the increase in absorbance of active site with decrease in temperature from 70 to 20 °C (is an indicative of the characteristic feature of hemocyanins—that oxygen is reversibly bound to the copper in the active site). Results from CD spectroscopy revealed that the temperature-induced conformational changes on the secondary structure of hemocyanin was reversible up to 70 °C. Beyond 80 °C, the protein was completely denatured and assumed an increased random coil conformation. Hemocyanin in the presence of high concentration of detergents lost its structure as evident from UV–Vis fluorescence (evident from the red shifts in the emission maxima accompanied by quenching in emission intensities) and CD spectroscopy. Stability of active site moieties in the presence of different detergents was also studied by UV–Vis spectroscopy. The biophysical techniques gave insights into the varied effects of each of the different denaturants on the conformational stability of hemocyanin from Pila virens.