A Monte Carlo Simulation of Polyethylene Chain

297-30

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

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

Synthesis and LB film formation of fatty acid- fad complex

Flavin adenine dinucleotide can exist in two oxidation states. Switching from one state to the other can be achieved chemically or electrically. The flavin undergoes reduction reversibly by two one electron steps or one two electron step, changing the chemistry of the enediamine subfunction of the isoalloxazine moiety. The adenine moiety is not involved in the catalysis, but helps in anchoring the coenzyme at the active site. The hydrophilicity of FAD has been changed by chemically attaching hydrocarbon chains to the noncatalytic adenine moiety. The modified coenzyme has been verified to retain the electro chemical, optical and the biochemical properties. The amphiphilic molecules can form monolayers at the air-water interface. A film of desired thickness can be formed on a solid support by means of monomolecular deposition using LB film technique. The characterization of the film has been done using spectrophotometric and electrochemical methods

Mechanism of action of L-arginine on the vitality of spermatozoa is primarily through increased biosynthesis of nitric oxide

The ability of sperm to fertilize the egg is primarily dependent on sperm motility and membrane integrity. Nitric oxide (NO) plays a decisive role in regulating multiple functions within the male reproductive system. The aim of the present study is to determine the mechanism by which L-arginine confers a protective action on spermatozoa obtained from the goat epididymis. NO is synthesized from L-arginine by the enzyme nitric oxide-synthase (NOS) present in spermatozoa. A possible participation of NO and NOS in arginine action has been suggested

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

LOCALIZATION AND ORIENTATION OF METHOXY FLAVONOIDS IN DPPC BILAYERS: EFFECT ON THEIR ANTI-PROLIFERATIVE ACTIVITY

Objective: Flavones and flavonols are an important class of naturally occurring flavonoids. They are well known for their pharmacological activity. This activity is associated with the ability of flavones and flavonols to influence membrane–dependent processes. In this paper, we have reported localization, orientation and interaction, of four synthesized flavone/flavonols with 1, 2–dipalmitoyl–sn–glycero–3–phosphocholine (DPPC) bilayers. These are compared with standard flavone; chrysin (CHY) and flavonol Quercetin (QUE).Methods: The molecules studied are 4ʹ–methoxy flavone (MF), 3ʹ,4ʹ–dimethoxyflavone (DMF), 4ʹ–methoxyflavonol (MF–ol) and 3ʹ,4ʹ–dimethoxyflavonol (DMF–ol). The techniques used are Differential Scanning Calorimetry (DSC) and multi–nuclear NMR.Results: Highest binding to lipid bilayers is shown by DMF, followed by QUE. Based on DSC studies it is seen, that maximum interaction of MF and DMF, takes place with the hydrophobic core of lipid bilayers. DMF–ol shows formation of a heterogeneous system at higher concentrations. The 1H NMR spectra of unilamellar vesicles of DPPC, incorporated with MF, DMF and MF–ol shows significant interaction of these compounds with the alkyl chain of the hydrophobic core. MF, DMF and MF–ol acquire parallel orientation in bilayers with the B–ring pointing towards hydrophobic core, while DMF–ol acquire mixed orientation. This may be ascribed to the presence of two methoxy and one hydroxyl group on the B–ring of DMF–ol which hinders its partitioning inside the hydrophobic core of lipid bilayer. Multi–lamellar vesicles (MLV) of DPPC incorporated with flavones, show maximum increase in Chemical Shift Anisotropy in 31P spectrum of DMF. This is followed by MF. DSC.Conclusion: NMR and binding studies indicate that DMF is partitioned deeply inside the hydrophobic core, while MF, MF–ol and DMF–ol are mostly located in the vicinity of sn–glycero region. Therefore, we conclude that DMF which penetrates deepest inside the hydrophobic core also shows the highest anti–proliferative activity against K562 and MCF–7 cancer cell lines. Its activity is also better than CHY

EFFECT OF METHYL SUBSTITUTION IN FLAVONES ON ITS LOCALIZATION AND INTERACTION WITH DPPC MODEL MEMBRANE: IMPLICATIONS FOR ANTI-PROLIFERATIVE ACTIVITY

Objective: Flavones are an important class of naturally occurring molecules possessing multiple pharmacological activities. The anti-proliferative activity is associated with the ability of flavones to influence membrane–dependent processes. We have investigated the localization and interaction of the synthesized flavones: 4΄–methylflavone (4MF) and 4΄–methyl–7–hydroxy flavone (4M7HF) with 1,2–dipalmitoyl–sn–glycero–3–phosphocholine (DPPC) model membrane. Methods: Diferential Scanning Calorimetry (DSC) and multi nuclear NMR were used to study the interactions with DPPC model membrane. The extent of interaction of these compounds has been compared with the parent molecules: flavone (FLV) and 7–hydroxy flavone (7HF). Results: Results of DSC and NMR indicate that FLV partitions deepest inside the hydrophobic core and 7HF is localized mostly at the lipid/water interface. 4MF and 4M7HF lying in between the hydrophilic and hydrophobic core. All four molecules assume a mixed orientation with respect to the bilayer normal as indicated by chemical shifts of the lipid protons in NMR. Interaction with the membrane follows the order FLV>4MF>4M7HF>7HF. Radical scavenging activity parallels the presence of hydroxyl groups. Although FLV interacts highest with the membrane, it does not show highest antiproliferative activity. Interaction of the compounds with protons 3, 5a and 7 of DPPC is improved by the methyl substitution on the B-ring, so is the antiproliferative activity. Conclusion: That's antiproliferative activity of the compounds is at least partially related to the interaction of these molecules with the lipid water interface region

A tracked approach for automated NMR assignments in proteins (TATAPRO)

A novel automated approach for the sequence specific NMR assignments of 1HN, 13Cα, 13Cβ, 13C'/1Hα and 15N spins in proteins, using triple resonance experimental data, is presented. The algorithm, TATAPRO (Tracked AuTomated Assignments in Proteins) utilizes the protein primary sequence and peak lists from a set of triple resonance spectra which correlate 1HN and 15N chemical shifts with those of 13Cα, 13Cβ and 13C'/1Hα. The information derived from such correlations is used to create a 'master list' consisting of all possible sets of 1HN i, 15Ni, 13Cα i, 13Cβ i, 13C'i/1Hα i, 13Cα i-1, 13Cβ i-1 and 13C'i-1/ 1Hα i-1 chemical shifts. On the basis of an extensive statistical analysis of 13Cα and 13Cβ chemical shift data of proteins derived from the BioMagResBank (BMRB), it is shown that the 20 amino acid residues can be grouped into eight distinct categories, each of which is assigned a unique two-digit code. Such a code is used to tag individual sets of chemical shifts in the master list and also to translate the protein primary sequence into an array called pps array. The program then uses the master list to search for neighbouring partners of a given amino acid residue along the polypeptide chain and sequentially assigns a maximum possible stretch of residues on either side. While doing so, each assigned residue is tracked in an array called assig array, with the two-digit code assigned earlier. The assig_array is then mapped onto the pps array for sequence specific resonance assignment. The program has been tested using experimental data on a calcium binding protein from Entamoeba histolytica (Eh-CaBP, 15 kDa) having substantial internal sequence homology and using published data on four other proteins in the molecular weight range of 18-42 kDa. In all the cases, nearly complete sequence specific resonance assignments (> 95%) are obtained. Furthermore, the reliability of the program has been tested by deleting sets of chemical shifts randomly from the master list created for the test proteins

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