A PVC plasticized membrane sensor for nickel ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w=w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 10 1– 5.0 10 6M (limit of detection is 1.8 10 6 M) with a slope of 29.5 1.0mV per decade of activity. It has a fast response time of<20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2–7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples – wastewater samples from electroplating industries and Indian chocolates.

A PVC Plasticized Membrane Sensor for Nickel Ions

A new PVC membrane sensor, which is highly selective towards Ni (II) ions, has been developed using a thiophene-derivative Schiff base as the ionophore. The best performance was exhibited by the membrane having the composition percentage ratio of 5:3:61:31 (ionophore:NaTPB:DBP:PVC) (w=w), where NaTPB is the anion excluder, sodium tetraphenylborate and DBP is the plasticizing agent (dibutyl phthalate). The membrane exhibited a good Nernstian response for nickel ions over the concentration range of 1.0 10 1– 5.0 10 6M (limit of detection is 1.8 10 6 M) with a slope of 29.5 1.0mV per decade of activity. It has a fast response time of<20 s and can be used for a period of 4 months with good reproducibility. The sensor is suitable for use in aqueous solutions of a wide pH range of 3.2–7.9. The sensor shows high selectivity to nickel ions over a large number of mono-, bi- and trivalent cations. It has been successfully used as an indicator electrode in the potentiometric titration of nickel ions against EDTA and also for direct determination of nickel content in real samples – wastewater samples from electroplating industries and Indian chocolates.

Biochemical Investigations on the Stability of Biological Membranes

In this project, an attempt has been made to study the stability of erythrocyte and lysosomal membranes biochemically. Erythrocytes were chosen for the study because of their ready availability and relative simplicity. Biological membranes forming closed boundaries between compartments of varying composition consist mainly of proteins and lipids. They are asymmetric, fluid structures that are thermodynamically stable and metabolically active. Normal cellular function begins with normal membrane structure and any variation in it may upset the normal functions. The degree of fluidity of a membrane depends on the chain length of its lipids and degree of unsaturation of constituent fatty acids. In response to environmental changes, many cells can regulate composition of their membranes to maintain the overall semi fluid environment necessary for many membrane associated functions. The assembly and Maintenance of membrane structures in cells is a dynamic process. The components are not only synthesized and inserted into a growing membrane but are also continuously degraded at a slower rate. This turnover process varies with each individual molecule.Lysosomes are important in the catabolic processes occurring in the cell. Lysosomes contain hydrolytic enzymes and are stable under normal conditions. In certain pathological conditions, the lysosomal membrane may rupture, releasing the hydrolytic enzymes into the cell and digestion of cell takes place as a whole. This is very dangerous. In normal life processes of multi cellular organisms, lysosomes rupture following the death of a cell and it may have some value as a built in mechanism for selfremoval of dead cells.An attempt has also been made in this project towards developing lysosome membrane stability as an index of fish spoilage during storage. Different membranes within the cell and between cells have different compositions as reflected in the ratio of protein to lipid. The difference is not surprising given the very different functions of membranes

PVC Supported Liquid Membrane and Carbon Paste Potentiometric Sensors Incorporating a Mn(III)-Porphyrin for the Direct Determination of Undissociated Paracetamol

PVC supported liquid membrane and carbon paste potentiometric sensors incorporating an Mn(III)-porphyrin complex as a neutral host molecule were developed for the determination of paracetamol. The measurements were carried out in solution at pH 5.5. Under such conditions paracetamol exists as a neutral molecule. The mechanism of molecular recognition between the Mn(III)-porphyrin and paracetamol, leading to potentiometric signal generation, is discussed.The sensitivity and selectivity toward paracetamol of carbon paste and polymeric liquid membrane electrodes incorporating an Mn(III)-porphyrin host were compared. The applicability of these sensors to the direct determination of paracetamol was checked by performing a recovery test in human plasma.

STUDIES ON HAEMOLYMPH CONSTITUENTS OF PILA VIRENS (LAMARCK) AND THE EFFECTS OF PESTICIDES ON THE ACTIVITY PATTERN OF SELECTED ENZYMES

The present study is an attempt to understand the physiological responses of a freshwater gastropod, in terms of haematological parameters, in normal conditions as well as in various natural and man made altered conditions of the environment.Pila virens, a freshwater prosobranch,commonly found in paddy fields, ponds, and streams of Kerala is selected as the test animal for the present investigation. Various haemolymph constituents such as total carbohydrate, glycogen, total protein, total lipid, urea,ammonia,sodium,potasium, calcium, and chloride which are directly involved in the control and maintenance of different physiological systems, were analysed in the present study. Selected haematological parameters like total haemocyte number, and packed cell volume were also determined. Besides , the activity pattern of selected haemolymph enzymes such as acid phosphatase (ACP), alkaline phosphatase (ALP),Glutamate-oxaloacetate transaminase (GOT), and glutamate-pyruvate transaminase (GPT), all having diagnostic value in terms of internal defence system and metabolism of the organism, were also studied.

Acid activated montmorillonite: an efficient immobilization support for improving reusability, storage stability and operational stability of enzymes

Three enzymes, α-amylase, glucoamylase and invertase, were immobilized on acid activated montmorillonite K 10 via two independent techniques, adsorption and covalent binding. The immobilized enzymes were characterized by XRD, N2 adsorption measurements and 27Al MAS-NMR spectroscopy. The XRD patterns showed that all enzymes were intercalated into the clay inter-layer space. The entire protein backbone was situated at the periphery of the clay matrix. Intercalation occurred through the side chains of the amino acid residues. A decrease in surface area and pore volume upon immobilization supported this observation. The extent of intercalation was greater for the covalently bound systems. NMR data showed that tetrahedral Al species were involved during enzyme adsorption whereas octahedral Al was involved during covalent binding. The immobilized enzymes demonstrated enhanced storage stability. While the free enzymes lost all activity within a period of 10 days, the immobilized forms retained appreciable activity even after 30 days of storage. Reusability also improved upon immobilization. Here again, covalently bound enzymes exhibited better characteristics than their adsorbed counterparts. The immobilized enzymes could be successfully used continuously in the packed bed reactor for about 96 hours without much loss in activity. Immobilized glucoamylase demonstrated the best results.

Biochemical Studies on the Protective Effect of Taurine on Experimentally Induced Myocardial infarction in Rats

The present study indicate that prior administration of taurine is effective in minimizing all the deleterious effects induced by isoproterenol, thereby justifying its use as a potent cytoprotective agent. The overall cardioprotective effect of taurine is probably related to its antioxidant property evidenced by its ability to reduce lipid peroxidation and to maintain the activities of free radical enzymes and nonenzymatic antioxidants, its membrane stabilizing action and to its hypolipidemic property.

A study on the Immobilizaton of Enzymes on Polymeric Supports

This work was focused to study the immobilization of enzymes on polymers. A large range of polymer matrices have been employed as supports for enzyme immobilization. Here polyaniline (PAN!) and poly(0~toluidine) (POT) were used as supports. PANI and POT provides an excellent support for enzyme immobilization by virtue of its facile synthesis, superior chemical and physical stabilities, and large retention capacity. We selected industrially important starch hydrolyzing enzymes a-amylase and glucoamylase for the study. In this work the selected enzymes were immobilized via adsorption and covalent bonding methods.To optimize the catalytic efficiency and stability of the resulting biocatalysts, the attempt was made to understand the immobilization effects on enzymatic properties. The effect of pH of the immobilization medium, time of immobilization on the immobilization efficiency was observed. The starch hydrolyzing activity of free 0:-amylase and glucoamylase were compared with immobilized forms. Immobilization on solid supports changes the microenvironment of the enzyme there by influences the pH and temperature relationship on the enzymatic activity. Hence these parameters also optimized. The reusability and storage stability of immobilized enzymes an important aspect from an application standpoint, especially in industrial applications. Taking in to consideration of this, the reusability and the long tenn storage stability of the immobilized enzyme investigated.

Aqueous Sol-gel Process for Nanocrystalline Photocatalytic Titania, Transparent Functional Coatings and Ceramic Membrane

The present thesis develops from the point of view of titania sol-gel chemistry and an attempt is made to address the modification of the process for better photoactive titania by selective doping and also demonstration of utilization of the process for the preparation of supported membranes and self cleaning films.A general introduction to nanomaterials, nanocrystalline titania and sol-gel chemistry are presented in the first chapter. A brief and updated literature review on sol-gel titania, with special emphasis on catalytic and photocatalytic properties and anatase to rutile transformation are covered. Based on critical assessment of the reported information the present research problem has been defined.The second chapter describes a new aqueous sol-gel method for the preparation of nanocrystalline titania using titanyl sulphate as precursor. This approach is novel since no earlier work has been reported in the same lines proposed here. The sol-gel process has been followed at each step using particle size, zeta potential measurements on the sol and thermal analysis of the resultant gel. The prepared powders were then characterized using X-ray diffraction, FTIR, BET surface area analysis and transmission electron microscopy.The third chapter presents a detailed discussion on the physico-chemical characterization of the aqueous sol-gel derived doped titania. The effect of dopants such as tantalum, gadolinium and ytterbium on the anatase to rutile phase transformation, surface area as well as their influence on photoactivity is also included. The fourth chapter demonstrates application of the aqueous sol-gel method in developing titania coatings on porous alumina substrates for controlling the poresize for use as membrane elements in ultrafiltration. Thin coatings having ~50 nm thickness and transparency of ~90% developed on glass surface were tested successfully for self cleaning applications.

The influence of organophosphorus pesticide-methylparathion on protein, lipid metabolism and detoxifying enzymes in rohu (Labeo rohita)

Methylparathion (MP) is an organophosphorus insecticide used world wide in agriculture due to its high activity against a broad spectrum of insect pests. The aim of the study is to understand the effect of methylparathion on the lipid peroxidation, detoxifying and antioxidant enzymes namely catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione Stransferase (GST), total reduced glutathione (GSH), lipid peroxidation (LPO), acetylcholinesterase (AChE) and disease diagnostic marker enzymes in liver, sarcoplasmic (SP) and myofirbirllar (MF) proteins in muscles, lipids and histopathlogical changes in various organs of Labeo rohita of size 75 i 6g at lethal and sublethal level of exposure. The probit analysis showed that the lethal concentration (LC 50%) for 24, 48, 72 and 96h were 15.5mg/L, 12.3mg/L, 11.4mg/L and 10.2mg/L respectively which is much higher compared to the LC50 for juvenile fish. The LPO level and GST activity increased five folds and two folds respectively on exposure to methylparathion at 10.2 mg/L and the level of the enzymes increased, on sub lethal exposure beyond 0.25mg/L. AChE activity was inhibited by 74% at a concentration of 1.8mg/L and 90% at 5.4mg/L. The disease diagnostic marker enzymes AST, ALT, ALP and LDH increased by about 2, 3 ,3 and 2 folds respectively at pesticide concentration of 10.2mg/L when compared to control. On sub lethal exposure, however the enzymes did not show any significant changes up to 0.5mg/L. At a concentration of 10.2 mg/L, there was a three fold increase in myofibrillar proteins while the increase in sarcoplasmic protein was above 1.5 fold. On sub lethal exposure, significant alteration was noticed up to 30 days up to 1mg/L of methylparathion concentration. Further exposure up to 45 days increased sarcoplasmic proteins (upto 0.5mg/L). ln the case of myofibrillar proteins, noticeable changes were observed at 1mg/L concentration right from 15th day. The cholesterol content in brain tissues increased by about 27% at methylparathion concentration of 5.4 mglL. However at 0.25mg/L sub lethal concentration, no significant alteration was observed in enzyme activity, muscle proteins, lipids and histopathology of the tissues. The results suggest that methylparathion has the potential to induce oxidative stress in fish, and that liver, muscle and brains are more sensitive organs of Labeo rohita, with poor antioxidant potentials at higher concentrations of the pesticide. The various parameters studied in this investigation can also be used as biomarkers of methylparathion exposure.

Physicochemical and Biochemical Characterization of Enzymes Immobilized on lnorganic Matrices

Biotechnology is currently considered as a useful altemative to conventional process technology in industrial and catalytic fields. The increasing awareness of the need to create green and sustainable production processes in all fields of chemistry has stimulated materials scientists to search for innovative catalysts supports. lmmobilization of enzymes in inorganic matrices is very useful in practical applications due to the preserved stability and catalytic activity of the immobilized enzymes under extreme conditions. Nanostructured inorganic, organic or hybrid organic-inorganic nanocomposites present paramount advantages to facilitate integration and miniaturization of the devices (nanotechnologies), thus affording a direct connection between the inorganic, organic and biological worlds. These properties, combined with good chemical stability, make them competent candidates for designed biocatalysts, protein-separation devices, drug delivery systems, and biosensors Aluininosilicate clays and layered double hydroxides, displaying, respectively, cation and anion exchange properties, were found to be attractive materials for immobilization because of their hydrophilic, swelling and porosity properties, as well as their mechanical and thermal stability.The aim of this study is the replacement of inorganic catalysts by immobilized lipases to obtain purer and healthier products.Mesocellular silica foams were synthesized by oil-in-water microemulsion templating route and were functionalized with silane and glutaraldehyde. " The experimental results from IR spectroscopy and elemental analysis demonstrated the presence of immobilized lipase and also functionalisation with silane and glutaraldehyde on the supports.The present work is a comprehensive study on enzymatic synthesis of butyl isobutyrate through esterification reaction using lipase immobilized onto mesocellular siliceous foams and montmorillonite K-10 via adsorption and covalent binding. Moreover, the irnrnobil-ization does not modify the nature of the kinetic mechanism proposed which is of the Bi-Bi Ping—Pong type with inhibition by n-butanol. The immobilized biocatalyst can be commercially exploited for the synthesis of other short chain flavor esters. Mesocellular silica foams (MCF) were synthesized by microemusion templating method via two different routes (hydrothermal and room temperature). and were functionalized with silane and glutaraldehyde. Candida rugosa lipase was adsorbed onto MCF silica and clay using heptane as the coupling medium for reactions in non-aqueous media. I From XRD results, a slight broadening and lowering of d spacing values after immobilization and modification was observed in the case of MCF 160 and MCF35 but there was no change in the d-spacing in the case of K-10 which showed that the enzymes are adsorbed only on the external surface. This was further confirmed from the nitrogen adsorption measurements

Glycogen degrading enzymes and their regulation in benthic animals and estuarine fish

Alpha glucan phosphorylase plays a very significant role in glycolysis. The inhibition and activation of this enzyme have significant effect on the rate of glycolysis. The rate of glycolysis is also determined by the interconversion between the active 3 and inactive Q forms of phosphorylase by two specific enzymes called phosphorylase phosphatase and phosphorylase kinase. The allosteric properties and interconversion mechanism reported for well—studied animal muscle phosphorylases do not fall under a general pattern. Studies using purified phosphorylase from marine sources are scanty. Detailed studies using specialised tissues from more marine animals are necessary to find the factors that control the properties and activities of the enzyme. This thesis is an attempt in this direction. The thesis deals with a detailed study of the control of the phosphorylase by both allosterism and interconversion between the g and b forms from four different aquatic animals of different habitat. Phosphorylase frm the four different animal muscles were purified either partially or completely and the kinetic and control properties were studied.

Studies on the digestive enzymes of the cultivable grey mullet liza parsia (hamilton buchanan, 1822)

Culturing of fish in captivity demands a detailed knowledge on well balanced diet and adequate feeding. Formulation and production of nutritionally balanced diets for fish require research, quality control and biological evaluation. It is often assuemed that what is ingested is also digested, but this is not always be the case. Digestion depends upon both the physical state of the food and the kind and quantity of enzymes in the digestive tract. The ability of fish to digest a particular component of diet can be ascertained by investigating the complement of digestive enzymes present along the digestive tract. Investigations on the basic digestive physiology will not only enhance our present knowledge on nutrition and feed development, but will also contribute in understanding the digestive functions of lower vertebrates. It is against this background that the present topic of investigation "Studies on the digestive enzymes of the cultivable grey mullet Liza parsia Hamilton Buchanan, l822" has been selected. The thesis is arranged and presented in eight chapters.

Studies on the digestive enzymes of the Indian white prawn Penaeus indicus H. Milne Edwards

The efficiency of a diet not only depends on its nutrient composition and nutrient balance but also on the effective utilization by the animal. In the utilization of dietary nutrients, the digestive enzymes play the crucial role of catalysing the hydrolytic reactions, splitting the macromolecules into simple absorbable molecules. The activity of these biocatalysts is regulated by alterations in pH, temperature, substrate type and concentrations, and also by the presence of activators and inhibitors. Thus any shift from the optimum conditions necessary for these enzymes may affect their activity, thereby correspondingly modify the digestibility of the nutrients supplied to the animals. Thus, investigations on the important digestive enzymes and their preferential conditions of activity are essential, so that the results obtained could be used in rationally adjusting the quality and quantity of feed supplied to the different stages of prawns In India, directed research on nutritional physiology and biochemical approaches to digestion in commercially important prawns is taken up_ only recently, and the field is still in an infant stage. In view of its emerging importance it is identified as an area of priority and the present investigation has been carried out on the Indian white prawn Penaeus indicus