Immobilization of glucose oxidase with polyurethane on carbon support

Glucose oxidase (GOD) has been immobilized by physical entrapment on polyurethane PU-6 matrix. It has been found that the enzyme acquires greater thermal stability on immobilization. Oxygen acts as a co-substrate for the redox reaction. However, maintaining oxygen concentration constant throughout the experiment is a difficult task. To overcome this we have coimmobilized ferrocene, which can act as an electron acceptor. 31P NMR results indicate that ferrocene is located in the close proximity of the active site of GOD. Moreover, simultaneous use of mediators such as ferricyanide, phenazine methosulphate or flavine mononucleotide have been found to facilitate electron transfer. Platinum, apart from being an expensive metal, is likely to exhibit adverse toxic effects during prolonged 'in-vivo' applications. Electrodes prepared using carbon in the place of platinum, show comparably good response. This opens a new possibility for making cheaper and biocompatible sensors

Magnetic resonance methods for studying intact spermatozoa

Motility is used as a routine parameter for assessing spermatozoa activity. The quality rating techniques adopted are based on electron or optical microscopy. However, these methods depend on gross structural and dynamical features of sperm cells and do not provide information on metabolic activity of intact cells. Lately, biochemical assays have become popular. Such methods are cumbersome and destroy the samples. Magnetic resonance methods offer a non-invasive method for studies on intact sperms. We have investigated respiration, maturation andin vitro capacitation of sperms from human ejaculates and sperms extracted from goat reproductive organ using electron spin resonance spin labelling and [31P] nuclear magnetic resonance methods. These studies clearly establish the advantages of magnetic resonance in studies related to metabolic activity of sperms

Peptide induced polymorphism in model membranes

Lipids in biological membranes generally adopt bilayer structures. However, incorporation of peptides may induce alterations in such structures. We have studied the influence of tryptophan, leucine, Trp-Leu, luteinizing hormone releasing hormone and renin inhibitor peptide on lipid organisation in liposomes. It has been observed that the effect is specific to the peptide molecule as-a whole and does not have direct correlation to the constituent amino acids or the conformation of the molecule

Studies on Some New Ru(III) Complexes Using aryl-azo Pentane- 2,4-dione and 2,6-bis (2'-Benzimidazolyl) Pyridine as Ligands: Synthesis, Spectroscopic, Luminescent, Electrochemical and Biological Activities

Some ruthenium(III) complexes with aryl-azo 2,4-pentanedione as co-ligands (L1H - L3H2) have been synthesized and characterized spectroscopically IR, 1H NMR, UV/Vis, ESR, conductimetric) along with elemental analysis and FAB-mass data. Their luminescent and redox properties have been studied. The antibacterial, anti-HIV and antitmnour activities have also been reported

Towards biochemical fuel cells

A biochemical fuel cell is a device which converts chemical energy into electrical power. The catalysts used in this process can be either inorganic or organic type giving rise to 'inorganic fuel cells' or 'biochemical fuel cells', respectively. Biochemical fuel cells use either micro-organism or enzymes as active components to carry out electrochemical reactions. The efficiency of such a device theoretically can be as high as 90%. The difficulty in attaining these values arises due to sluggishness of electron transfer from active site to conducting electrode. This can be overcome by using mediators or by immobilizing active components on conducting electrode. We have immobilizedfad-glucose oxidase on a graphite electrode using a semiconducting chain as a bridge. At the present stage of development, such a device tacks high current densities, which is essential for commercial power generation but can be used in applications such as pacemakers and glucose sensors

Conducting polymers in the fabrication of efficient biosensors

561-564Fabrication of efficient biosensors for industrial and medical applications is a challenging problem. Several polymers have been used for interfacing a biological component to the electrode surface in order to attain higher performance efficiency and faster electron transfer processes between the enzyme and the electrode. In this mini review, some of the successful matrices used in biosensor fabrication have been discussed

Observation of a tight-turn conformation in a proline-containing inhibitor of renin angiotensin

The solution conformation of renin inhibitor peptide, Pro-His-Pro-Phe-His-Phe-Phe-Val-Tyr-Lys, was established using proton magnetic resonance techniques. As a first step a complete resonance assignment was made in DMSO-d6 using 2D NMR techniques. Some of the backbone NH protons show a very low temperature coefficient, indicating their involvement in intramolecular hydrogen bonding. The 3J(NH-Cα, H) values the inter-residue NOEs, the temperature coefficient of the backbone NH protons and the chemical shift positions indicate the presence of a tight turn in the molecule. A model is proposed, using computer graphics, based on the experimental results

Effect of incorporation of drugs, vitamins and peptides on the structure and dynamics of lipid assemblies

The characteristics of vesicles formed from Dipalmitoyl Phosphatidyl Choline (DPPC) are sensitive to the presence of perturbing molecules such as drugs, peptides, hormones and vitamins. We have used ESR spin labeling and NMR techniques for studying interaction of such molecules with lipid bilayers. ESR spin labeling has been used to monitor thermotropic behaviour of model membranes. Different NMR probes such as1H,31P,13C have been used to gather information regarding the mode of interaction. It has been observed that the model membrane systems respond differently depending upon the localization of the perturbing molecules in the lipid bilayer. Small molecules such as neurotransmitters epinephrine and norepinephrine decrease gel to liquid crystalline phase transition temperature significantly even when present in small amounts. Vitamine E acetate having a hydrophobic hydrocarbon tail orients parallel to the lipid molecule and thereby exhibits dynamics similar to palmitate chain. When the acetate group is replaced by hydroxyl group (α-tocopherol), the phase transition becomes broad and the lipid molecules loose freedom of lateral diffusion. This can be attributed to formation of hydrogen bond between the hydroxyl group of α-tocopherol and phosphate moiety of lipid. The conformation of antidepressants nitroxazepine and imipramine is significantly altered when embedded in lipid bilayer. Anaesthetic etomidate not only modifies thermotropic characteristics but also induces polymorphism. The normal bilayer arrangement of lipids gets transformed into hexagonal packing. Amino acid tryptophan induces cubic phases in the normal bilayer arrangement of DPPC dispersions. Peptide gonadoliberin shows a reduced internal motion due to the lipid peptide interaction. The major consequences of binding of lipids with externally added molecules are changes in the fluidity and permeability properties of membranes. It has been shown that permeability is effected by the presence of molecules such as propranolol, α-tocopherol and its analogue, neurotransmitters, etc. The magnetic resonance methods have thus evolved as power techniques in the study of membrane structure and function

An approach to biomolecular electronics and bioengineering based on coenzymes chained to solid supports

The possibility of attaching coenzymes to graphite surfaces through molecular wires in a manner such that an efficient electron transport chain is established between the bioactive molecule and the solid support has been considered. The covalent link used in these studies prevents the active molecules from diffusing away in the aqueous environment and improves their stablity and efficiency. This opens the way to employing the molecules gainfully in biomolecular electronics and bioengineering. Through the use of Molecular Orbital methods, the optimum designs for immobilisation of NAD, FAD and Cyt-c have been considered, with a view to achieving efficient electron transport. These coenzymes span the complete range of energy-transduction processes in living cells. Each of these molecules exists in two states, a reduced and an oxidised state, which can be monitored by simple spectroscopic methods. Based on the predictions of the Molecular Orbital approach, the coenzymes have been attached to graphite surfaces through polyacetylene chains. In two cases, FAD and Cyt-c, the immobilised coenzyme retained both its electrochemical and biological activity. In the case of NAD, the preparation of active surfaces with covalently attached coenzyme has so far failed. Potential applications of the chained coenzyme systems could arise in the field of biosensors, biobatteries, synthesis of value-added compounds and biomolecular electronics

Electron delocalization during the oxidation-reduction cycle of FAD and NAD: a quantum chemical approach to the design of coenzyme-immobilized bioanode for biochemical fuel cells

A biochemical fuel cell (BFC) is an electrochemical power-generating device which converts the chemical energy of a hydrogen-rich fuel (alcohol, glucose, hydrocarbons, or hydrogen itself) into electrical energy through enzyme-catalyzed oxidation-reduction reactions. The major bottleneck in the design of such systems is the slow electron transport from the substrate to the electrode. Biochemical systems that use coenzymes such as flavin adenine dinucleotide (FAD) or nicotinamide adenine dinucleotide (NAD) seem to be promising in circumventing these difficulties. We have made systematic molecular orbital calculations at the indo level on the electron flow diagrams of flavin and nicotinamide rings during their oxidation-reduction cycle. We observe from such calculations that it is possible to obtain very efficient electron transport from the coenzyme to the electrode surface by immobilizing FAD or NAD through semiconducting side chains at certain selected positions to the electrodes such as graphite. The theoretical studies have helped in the design of coenzyme-immobilized anodes which show the expected redox cycles in cyclic voltammetric studies