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  • 1
    Electronic Resource
    Electronic Resource
    Digestion of biological materials for mineral analyses using a combination of wet and dry ashing (1986)
    s.l. : American Chemical Society
    Analytical chemistry 58 (1986), S. 2340-2342 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00124a049
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  • 2
    Electronic Resource
    Electronic Resource
    Synchrotron light source applied to measuring the vacuum ultraviolet circular dichroism of heparin (1985)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 107 (1985), S. 2982-2983 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00296a030
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular organization of glycophorin A: Implications for membrane interactions (1985)
    New York : Wiley-Blackwell
    Biopolymers 24 (1985), S. 2301-2332 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Physical studies and conformational analysis of human glycophorin A suggest a revised model for its molecular organization, self-association, and interactions with the erythrocyte membrane. Intrinsic viscosity has been used to study, under more physiological conditions, the monomer-dimer equilibrium demonstrated previously by polyacrylamide-SDS gel electrophoresis. The results show that the equilibrium persists in the absence of detergent and support earlier indications that the dimer is probably the physiologically relevant form and that it is promoted by salt, inhibited by conventional denaturants, and abolished by carboxymethylation.Combined application of CD, fitted to the poly-(L-lysine) model spectra of Greenfield and Fasman, and conformational prediction, by the statistical method of Chou and Fasman and the stereochemical approach of Lim, suggests five helical sequences in glycophorin A: Arg-39 to Tyr-52 (A); Gln-63 to Glu-70 (B); Glu-72 to Leu-89 (C); Ile-95 to Lys-101 (D); and Leu-118 to Asn-125 (E). Sequence A occurs only at low pH and may be stabilized by favorable noncovalent interactions of O-linked tetrasaccharide side chains. The other four helices all occur in the dimeric form of glycophorin A at physiological pH and ionic strength. Sequence D is destroyed by trypsin, and is also lost on conversion to the monomeric form of the glycoprotein at low ionic strength. Sequence E is denatured by 6M guanidine hydrochloride/4M urea. Sequences B and C, which are separated by a single proline residue, are stable under all these conditions.Dimerization of the major, hydrophobic helical sequence, (C) may be promoted and directed by an adjacent short sequence of intermolecular parallel β-sheet (Leu-90 to Tyr-93). It is proposed that these two structures span the lipid bilayer in vivo, and that helices B and D lie, respectively, along the outer and inner surfaces of the membrane. Molecular organization in the N- and C-terminal regions of the molecule is discussed in terms of evidence from the present work and from other recent investigations.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360241210
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  • 4
    Electronic Resource
    Electronic Resource
    Total optical activity of agarose: Relation to observable transitions in the vacuum ultraviolet (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 959-973 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The changes in optical activity that accompany and characterize the coil-helix and helix-coil transitions of agarose in aqueous solutions and gels have been investigated by combined quantitative analysis of data from vacuum ultraviolet circular dichroism (VUCD) and optical rotary dispersion (ORD). VUCD of agarose in the high-temperature coil state shows a single accessible Gaussian band centered at ∼183 nm. In the helix state this band is blue-shifted by ∼9 nm, and the intensity is increased by a factor of ∼2.6. Spectra at intermediate temperatures can be fitted to within experimental error by linear combination of coil and helix spectra, the relative proportions required providing an index of the extent of conformational ordering. ORD spectra throughout the conformational transition have a common form and differ only in absolute magnitude. The temperature course of conformational ordering derived from ORD intensity is in close agreement with the values obtained from VUCD. In both the coil and helix states the accessible VUCD band is positive, while the overall ORD is negative, indicating strong negative CD activity at lower wavelength. The ORD contribution corresponding to the positive VUCD band was calculated by Kronig-Kramers transform, and it was subtracted from the total ORD to give the residual ORD from all other optically active transitions of the molecule. In both the coil and helix states, this residual ORD could be fitted to within experimental error by a single Gaussian CD band at ∼149 nm. A negative band at this wavelength has been reported previously for agarose films, but the observed intensity, relative to that of the lower energy positive band, is substantially smaller than the fitted value under hydrated conditions. In both the coil and helix states the total optical activity of agarose, characterized by observed ORD spectra, can be matched to within experimental error by Kronig-Kramers transform of the 149-nm negative band and the smaller positive band at higher wavelength, with no necessary involvement of deeper-lying transitions. The significance of this conclusion for fundamental understanding of carbohydrate optical activity is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250514
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  • 5
    Electronic Resource
    Electronic Resource
    Long-term consumption of beef extended with soy protein by children, women and men: III. Iron absorption by adult men (1987)
    Springer
    Plant foods for human nutrition 37 (1987), S. 377-389 
    Details
    ISSN: 1573-9104
    Keywords: iron status ; iron nutrition ; soy protein ; iron absorption ; mineral nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Forty-nine ostensibly healthy men consumed either patties of all-beef or beef extended with soy-isolate, -concentrate or -flour as the principal protein source in 1 to 2 meals daily for 180 days. Iron status was monitored by absorption of radioiron from a reference dose of ferrous ascorbate and by serum ferritin concentration. In addition, nonheme iron absorption from a test meal of the respective beef pattie consumed for the 180 days was estimated by the extrinsic tag procedure. There was no detrimental effect on iron stores as indexed by reference ferrous ascorbate absorption or serum ferritin concentration. Absorption of nonheme iron from the test meals was low except for individuals having indices of low iron stores. When adjusted for the effect of level of iron stores the relative absorption of nonheme iron from soy-isolate and -flour containing meals was greater than from the all-beef meal, indicating marked differences in the effect on iron absorption by different soy products. Consumption of soy-extended beef should have no detrimental effect on iron status of adult men if consumed in mixed diets at the level used in this study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01092212
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamics of molecular organization in agarose sulphate (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1009-1029 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nongelling solutions of structurally regular chain segments of agarose sulphate show disorder-order and order-disorder transitions (as monitored by the temperature dependence of optical rotation) that are closely similar to the conformational changes that accompany the sol-gel and gel-sol transitions of the unsegmented polymer. The transition midpoint temperature (Tm) for formation of the ordered structure on cooling is ∼25 K lower than Tm for melting. Salt-induced conformational ordering, monitored by polarimetric stopped-flow, occurs on a millisecond time scale, and follows the dynamics expected for the process 2 coil ⇌ helix. The equilibrium constant for helix growth (s) was calculated as a function of temperature from the calorimetric enthalpy change for helix formation (ΔHcal = -3.0 ± 0.3 kJ per mole of disaccharide pairs in the ordered state), measured by differential scanning calorimetry. The temperature dependence of the nucleation rate constant (knuc), calculated from the observed second-order rate constant (kobs) by the relationship kobs = knuc(1 - 1/s) gave the following activation parameters for nucleation of the ordered structure of agarose sulphate (1 mg mL-1; 0.5M Me4NCl or KCl): ΔH* = 112 ± 5 kJ mol-1; ΔS* = 262 ± 20 J mol-1 K-1; ΔG*298 = 34 ± 6 kJ mol-1; (knuc)298 = (7.5 ± 0.5) × 106 dm3 mol-1 s-1. The endpoint of the fast relaxation process corresponds to the metastable optical rotation values observed on cooling from the fully disordered form. Subsequent slow relaxation to the true equilibrium values (i.e., coincident with those observed on heating from the fully ordered state) was monitored by conventional optical rotation measurements over several weeks and follows second-order kinetics, with rate constants of (2.25 ± 0.07) × 10-4 and (3.10 ± 0.10) × 10-4 dm3 mol-1 s-1 at 293.7 and 296.2 K, respectively. This relaxation is attributed to the sequential aggregation processes helix + helix → dimer, helix + dimer → trimer, etc., with depletion of isolated helix driving the much faster coil-helix equilibrium to completion. Light-scattering measurements above and below the temperature range of the conformational transitions indicate an average aggregate size of 2-3 helices.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250604
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