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  • 1
    Electronic Resource
    Electronic Resource
    Effect of incorporation of drugs, vitamins and peptides on the structure and dynamics of lipid assemblies (1989)
    Springer
    Molecular and cellular biochemistry 91 (1989), S. 99-109 
    Details
    ISSN: 1573-4919
    Keywords: drugs ; vitamins ; hormones ; peptides ; membranes ; NMR ; ESR ; 2D-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228084
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  • 2
    Electronic Resource
    Electronic Resource
    Covalent immobilization of FAD and glucose oxidase on carbon electrodes (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 1066-1070 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effectiveness of attaching flavin adenine dinucleotide (FAD) via a C bridge to Teflon-bonded carbon black (CB), and the subsequent immobilization of glucose oxidase on the FAD-modified electrodes has been studied by cyclic voltammetry. When FAD alone is bound to the electrode, it undergoes reduction and oxidation at -0.62 and -0.5 V, respectively - values similar to those obtained with free FAD. Compared to the free enzyme, the reduction of FAD as part of the immobilized enzyme is 200 mV more cathodic, while the oxidation potential remains the same in both cases.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260260908
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  • 3
    Electronic Resource
    Electronic Resource
    Structure and function of propranolol: A β-adrenergic blocking drug (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 85-92 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In our earlier studies using quantum chemical methods we had proposed that propranolol has an extended structure. These results were confirmed using proton NMR. We have now carried out extensive magnetic resonance and model building studies to examine the interaction of this drug with model membranes. The effect of propranolol on organization of lipid bilayers has been studied using ESR spin labeling technique. Spin label Tempo and spin labeled stearic acid (5 SASL) have been used to monitor changes in the fluidity of model membranes. Presence of the drug is found to fluidize the lipids. In case of 0.2M dipalmitoyl phosphatidyl choline (DPPC), presence of drug (0.1M) is found to decrease the gel-liquid crystalline phase transition temperature by about 10°C. The order parameter measured from the spectrum of 5 SASL shows a 4% decrease on incorporation of the drug in membranes. 13C spin lattice relaxation time (T1) measurements have been carried out for different nuclear sites of the drug. The aromatic moiety shows a high degree of molecular rigidity when the drug is bound to the lipid bilayers. The oxypropanolamine group is however relatively flexible. It appears from these studies that the aromatic group binds strongly to the hydrophobic regions of the lipid bilayer, while the oxypropanolamine moiety remains relatively free and lies in the hydrophilic region. The 13C chemical shifts indicate the involvement of the β-hydroxyl group in hydrogen bonding with the lipids. The NH2+ group may be involved in electrostatic interactions with the negatively charged phosphate group of the lipid bilayers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200109
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  • 4
    Electronic Resource
    Electronic Resource
    Conformation and intermolecular interation of the antidepressant drugs nitroxazepine and imipramine in aqueous solutions and model membranes (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 905-910 
    Details
    ISSN: 0749-1581
    Keywords: Nitroxazepine ; Imipramine ; 1H NMR ; Stacking interactions ; Conformation ; Lipid bilayers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complete assignments of the proton magnetic resonance spectra of nitroxazepine and imipramine have been made using 1D and 2D techniques. The drugs are found to aggregate through stacking intereactions between the tricyclic moieties at higher concentrations in aqueous solutions. The changes in the chemical shifts with increasing concentration of the two antidepressant drugs show qualitative agreement with the stacking patterns and conformations observed in crystal structures. The conformations of the propyl moiety of the two drugs in aqueous solution and in lipid bilayers are very different. In D2O, the drugs exist in an extended chain conformation which is similar to the crystal structure. In lipid bilayers they acquire a folded structure. The folded structures probably facilitate the binding of the hydrophobic regions of the drugs to the interior of lipid bilayers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260251015
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  • 5
    Electronic Resource
    Electronic Resource
    Observation of a tight-turn conformation in a proline-containing inhibitor of renin angiotensin (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 455-459 
    Details
    ISSN: 0749-1581
    Keywords: Nuclear magnetic resonance ; Renin inhibitor peptide ; Nuclear Overhauser effect ; Correlated spectroscopy ; Mixing time ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260270507
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  • 6
    Electronic Resource
    Electronic Resource
    Occurrence of β-bends in bradykinin dissolved in DMSO-d6 (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 587-593 
    Details
    ISSN: 0749-1581
    Keywords: Nuclear magnetic resonance ; Bradykinin ; β-Bend ; Nuclear Overhauser effect ; Correlated spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of the hormone bradykinin (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) in DMSO-d6 was investigated using proton NMR spectroscopy at 500 MHz. Complete resonance assignments were made using 2D COSY and NOESY techniques. The chemical shifts, magnitudes of the 3JNH-CαH couplings, temperature coefficient data on backbone NH protons and intramolecular NOEs were used to obtain information on the conformation. The nonapeptide assumes a rigid structure in DMSO-d6. Based on the experimental results, a model is proposed using computer-aided molecular graphics.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280706
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  • 7
    Electronic Resource
    Electronic Resource
    Loss in conformational rigidity of bradykinin on replacement of the Phe-8 by tyrosine (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 333-337 
    Details
    ISSN: 0749-1581
    Keywords: Bradykinin ; [Tyr8]-bradykinin ; 1H NMR ; Conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complete resonance assignments and the conformation of the hormone [Tyr8]-bradykinin, a nonapeptide, in DMSO-d6 have been determined using 2D 1H NMR techniques. NMR parameters such as the chemical shifts, coupling constants, temperature coefficients of the backbone NH protons and NOEs have been analysed in the light of the known conformation of the native peptide. The results indicate that the peptide loses conformational rigidity on the replacement of Phe-8 by Tyr.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290409
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