101
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Hack T, Abetz V, Stamm M, Schubert DW, Mortensen K, Siol W. Spinodal decomposition of a polystyrene/poly(cyclohexyl acrylate-stat-butyl methacrylate) blend. Colloid Polym Sci 1996. [DOI: 10.1007/bf00654055] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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102
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Bates FS, Maurer W, Lodge TP, Schulz MF, Matsen MW, Almdal K, Mortensen K. Isotropic Lifshitz behavior in block copolymer-homopolymer blends. Phys Rev Lett 1995; 75:4429-4432. [PMID: 10059906 DOI: 10.1103/physrevlett.75.4429] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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103
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Lemmich J, Mortensen K, Ipsen JH, Honger T, Bauer R, Mouritsen OG. Pseudocritical behavior and unbinding of phospholipid bilayers. Phys Rev Lett 1995; 75:3958-3961. [PMID: 10059774 DOI: 10.1103/physrevlett.75.3958] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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104
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Yaron U, Gammel PL, Huse DA, Kleiman RN, Oglesby CS, Bucher E, Batlogg B, Bishop DJ, Mortensen K, Clausen KN, Bolle CA. Yaron et al. reply. Phys Rev Lett 1995; 75:3373. [PMID: 10059568 DOI: 10.1103/physrevlett.75.3373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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105
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Ellouze C, Takahashi M, Wittung P, Mortensen K, Schnarr M, Nordén B. Evidence for elongation of the helical pitch of the RecA filament upon ATP and ADP binding using small-angle neutron scattering. Eur J Biochem 1995; 233:579-83. [PMID: 7588804 DOI: 10.1111/j.1432-1033.1995.579_2.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Structural changes of the RecA filament upon binding of cofactors have been investigated by small-angle neutron scattering. Both ATP and ADP increased the helical pitch of the RecA homopolymer, which is observed to be 7 nm in the absence of any cofactor. The binding of ATP altered the pitch to 9 nm, whereas the binding of ADP only produced a pitch of 8.2 nm. The pitch determined for the RecA complex with the ATP analog adenosine 5'-[gamma-thio]triphosphate was similar to that found with ATP. Thus, at least three, somewhat different. RecA helical filamentous structures may form in solution. The binding of DNA to RecA did not alter the pitch significantly, indicating that the cofactor binding is the determining factor for the size of the helical pitch of the RecA filament. We also found that elongation of the helical pitch is a necessary, but not a sufficient condition, for the coprotease activity of RecA. The presence of acetate or glutamate ions is also required. The pitch of the ADP.RecA filament is in agreement with that found in the crystal structure. This correlation indicates that this structure corresponds to that of the ADP.RecA filament in solution, although this is not the species active in recombination.
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Affiliation(s)
- C Ellouze
- Groupe d'Etude Mutagénese et Cancérogénèse, Centre National de la Recherche Scientifique Unité 1342, Orsay, France
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106
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Holmström-Ruddick B, Mortensen K. In vitro formation and survival of appressoria of a mycoherbicide agent, Colletotrichum gloeosporioides f. sp. malvae and a benomyl-resistant strain, HP4.5RR. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0953-7562(09)80779-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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107
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Schwahn D, Schmackers T, Mortensen K. Ginzburg criterion for the mean-field to three-dimensional Ising crossover in polymer blends. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 52:R1288-R1291. [PMID: 9963651 DOI: 10.1103/physreve.52.r1288] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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108
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Yaron U, Gammel PL, Huse DA, Kleiman RN, Oglesby CS, Bucher E, Batlogg B, Bishop DJ, Mortensen K, Clausen KN. Structural evidence for a two-step process in the depinning of the superconducting flux-line lattice. Nature 1995. [DOI: 10.1038/376753a0] [Citation(s) in RCA: 163] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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109
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�sterberg R, Mortensen K, Ikai A. Direct observation of humic acid clusters, a nonequilibrium system with a fractal structure. Naturwissenschaften 1995. [DOI: 10.1007/bf01177274] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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110
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Yaron U, Gammel PL, Huse DA, Kleiman RN, Oglesby CS, Bucher E, Batlogg B, Bishop DJ, Mortensen K, Clausen K, Bolle CA. Neutron diffraction studies of flowing and pinned magnetic flux lattices in 2H-NbSe2. Phys Rev Lett 1994; 73:2748-2751. [PMID: 10057182 DOI: 10.1103/physrevlett.73.2748] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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111
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Sjöberg B, Mortensen K. Interparticle interactions and structure in nonideal solutions of human serum albumin studied by small-angle neutron scattering and Monte Carlo simulation. Biophys Chem 1994; 52:131-8. [PMID: 7948715 DOI: 10.1016/0301-4622(94)00089-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Moderately or highly concentrated nonideal solutions of macromolecules are very important systems e.g. in biology and in many technical processes. In this work we have used the small-angle neutron scattering technique (SANS) to study the interactions and interparticle structure in solutions of human serum albumin (HSA) up to a concentration of 0.26 g/cm3 in 1.08 M NaCl. In order to obtain a model for the interactions we have combined the SANS data with results obtained by Monte Carlo simulations where we calculate the structure factor S(Q) and the pair correlation function g(r). The advantage of using the Monte Carlo method is that completely general models for the particle shape and the interactions can be considered. It is found that the SANS data can be explained by a model where the shape of the HSA molecule is approximated by an ellipsoid of revolution with semiaxes a = 6.8 nm and b = c = 1.9 nm. The interaction potential between the HSA molecules consists of two parts: (a) the molecules are hard and impenetrable and (b) the molecules are surrounded by a spherically symmetric repulsive potential which can be expressed by an empirical formula containing the HSA concentration and the centre-centre distances as the only variables.
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Affiliation(s)
- B Sjöberg
- Department of Medical Biochemistry, University of Göteborg, Sweden
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112
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Schwahn D, Mortensen K, Janssen S. Critical neutron scattering in a polymer blend above and below the critical point of demixing: Critical exponents and amplitude ratios. Phys Rev Lett 1994; 73:1452-1455. [PMID: 10056796 DOI: 10.1103/physrevlett.73.1452] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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113
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Osterberg R, Boive T, Wang W, Mortensen K, Saito A, Sinohara H, Ikai A. Small-angle scattering study of alpha 1 inhibitor III from rat blood plasma. Biochim Biophys Acta 1994; 1207:152-8. [PMID: 8075148 DOI: 10.1016/0167-4838(94)00064-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The alpha 1 proteinase inhibitor III from rat blood plasma, homologous to the alpha 2-macroglobulin family of proteins, has been studied in solution using small-angle scattering of X-rays and of neutrons: the radius of gyration, Rg, was found to be 4.5 nm, and the largest distance within the molecule, Dmax = 14 nm. When the inhibitor reacts with chymotrypsin or methylamine, the resulting derivatives yield slightly higher Rg-values, 4.7 and 4.85 nm, respectively. The data of the native protein are consistent with a model, the projection of which resembles the letter V and which is formed by the two identical halves of an elliptic cylinder with semi-axes of 2.1 and 5.5 nm and a length of 11 nm. This elliptic cylinder model also explained the scattering from the monomeric complement proteins C3 and C4, as well as that from the monomers of the dimeric and tetrameric alpha 2-macroglobulin family of proteins (Osterberg, R., et al. (1991), Biochemistry 30, 7873-7878). Due to the conformational change occurring when the thiol ester bond is split, the cleft in the V-form seems to be closed; and as a result, the models of the chymotrypsin and methylamine derivatives are more compact than that of the native protein.
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Affiliation(s)
- R Osterberg
- Department of Chemistry, Swedish University of Agricultural Sciences, Uppsala
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114
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Schulz MF, Bates FS, Almdal K, Mortensen K. Epitaxial relationship for hexagonal-to-cubic phase transition in a block copolymer mixture. Phys Rev Lett 1994; 73:86-89. [PMID: 10056726 DOI: 10.1103/physrevlett.73.86] [Citation(s) in RCA: 157] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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115
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Honger T, Mortensen K, Ipsen JH, Lemmich J, Bauer R, Mouritsen OG. Anomalous swelling of multilamellar lipid bilayers in the transition region by renormalization of curvature elasticity. Phys Rev Lett 1994; 72:3911-3914. [PMID: 10056328 DOI: 10.1103/physrevlett.72.3911] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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116
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Falcão AN, Pedersen JS, Mortensen K. Optimum intensity in small-angle neutron scattering. An experimental comparison between symmetric and asymmetric geometries. J Appl Crystallogr 1994. [DOI: 10.1107/s002188989301043x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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117
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Schwahn D, Meier G, Mortensen K, Janßen S. On the N-scaling of the Ginzburg number and the critical amplitudes in various compatible polymer blends. ACTA ACUST UNITED AC 1994. [DOI: 10.1051/jp2:1994168] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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118
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Førland G, Samseth J, Høiland H, Mortensen K. The Effect of Medium Chain Length Alcohols on the Micellar Properties of Sodium Dodecyl Sulfate in Sodium Chloride Solutions. J Colloid Interface Sci 1994. [DOI: 10.1006/jcis.1994.1154] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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119
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Gammel PL, Huse DA, Kleiman RN, Batlogg B, Oglesby CS, Bucher E, Bishop DJ, Mason TE, Mortensen K. Small angle neutron scattering study of the magnetic flux-line lattice in single crystal 2H-NbSe2. Phys Rev Lett 1994; 72:278-281. [PMID: 10056104 DOI: 10.1103/physrevlett.72.278] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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120
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Abstract
The growth of humic acids, prepared by a gentle method from two different kinds of soils (I and II), has been studied using small-angle neutron scattering at an acidity corresponding to pH 5.0 and 0.10 M ionic strength (NaCl). Humic acids aggregate either to large clusters with a fractal dimension of 2.3 and an average diameter of 1720 A (I) or to clusters with an average diameter of 700 A (II). After storage for 2 days at 4 degrees C, the latter aggregates (II) formed a gel. In a step toward gelation, we observed cluster-cluster interaction from the neutron-scattering data in the form of a correlation peak. These differences in size can be explained by assuming that the smaller particles (II) are trapped into a nonequilibrium state characterized by the temperature-solvent condition. The importance of a humic acid gel network for the conservation of water and nutrients in the environment is discussed.
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Affiliation(s)
- R Osterberg
- Department of Chemistry, Swedish University of Agricultural Sciences, Uppsala
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121
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122
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Cubitt R, Forgan EM, Yang G, Lee SL, Paul DM, Mook HA, Yethiraj M, Kes PH, Li TW, Menovsky AA, Tarnawski Z, Mortensen K. Direct observation of magnetic flux lattice melting and decomposition in the high-Tc superconductor Bi2.15Sr1.95CaCu2O8+x. Nature 1993. [DOI: 10.1038/365407a0] [Citation(s) in RCA: 439] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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123
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Kleiman RN, Broholm C, Aeppli G, Bucher E, Stücheli N, Bishop DJ, Clausen KN, Mortensen K, Pedersen JS, Howard B. Neutron diffraction from the vortex lattice in the heavy-fermion superconductor UPt3. Phys Rev Lett 1992; 69:3120-3123. [PMID: 10046730 DOI: 10.1103/physrevlett.69.3120] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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124
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Nordén B, Elvingson C, Kubista M, Sjöberg B, Ryberg H, Ryberg M, Mortensen K, Takahashi M. Structure of RecA-DNA complexes studied by combination of linear dichroism and small-angle neutron scattering measurements on flow-oriented samples. J Mol Biol 1992; 226:1175-91. [PMID: 1518050 DOI: 10.1016/0022-2836(92)91060-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
By combining anisotropy of small-angle neutron scattering (SANS) and optical anisotropy (linear dichroism, l.d.) on flow-oriented RecA-DNA complexes, the average DNA-base orientation has been determined in RecA complexes with double-stranded (ds) as well as single-stranded (ss) DNA. From the anisotropy of the two-dimensional SANS intensity representation, the second moment orientation function S is obtained. Knowledge of S is crucial for the interpretation of l.d. spectra in terms of orientation of the DNA bases and the aromatic amino acid residues. The DNA-base planes are essentially perpendicular to the fibre axis of the complex between RecA and dsDNA in the presence of cofactor ATP gamma S. A somewhat tilted base geometry is found for the RecA-ATP gamma S complexes with single-stranded poly(dT) and poly(d epsilon A). This behaviour contrasts the RecA-ssDNA complex formed without cofactor which displays a poor orientation of the bases. Well-ordered bases in the ssDNA-RecA complex is possibly reflecting the role of RecA in preparing a nucleotide strand for base-pairing in the search-for-homology process. While the central SANS intensity is essentially independent of the pitch of the helical complex, a secondary intensity maximum, which becomes focused upon flow orientation, is found to be a sensitive measure of the pitch. The pitch values for the complexes compare well with cryo-electron microscopy results but are slightly larger than those seen for uranyl-stained samples.
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Affiliation(s)
- B Nordén
- Department of Physical Chemistry, Chalmers University of Technology, Gothenburg, Sweden
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125
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Sjöberg B, Pap S, Mortensen K. Temperature dependence of the kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin into half-molecules. A minimum rate at 15 degrees C indicates hydrophobic interaction between the subunits. J Mol Biol 1992; 225:551-6. [PMID: 1375654 DOI: 10.1016/0022-2836(92)90939-h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin to half-molecules has been studied as a function of temperature by using small-angle scattering of X-rays and neutrons. The most striking result of the present investigation is that there is a minimum in reaction rate at about 15 degrees C, and that the rate increases when the temperature is lowered, or raised, from that value. By analyzing the first-order rate constants in terms of transition-state theory it was found that the dissociation is associated with a large and positive change in heat capacity between the activated complex and native alpha 2-macroglobulin (delta CP is in the range 5 to 6 kJ mol-1 K-1). In analogy with pure thermodynamic investigations, where a large change in heat capacity normally is interpreted as a melting of hydrophobic interaction, we therefore propose that hydrophobic interaction is involved in the so-called non-covalent interactions between the subunits of alpha 2-macroglobulin. As a result of the present investigation, it also follows that the free energy of activation delta G has a maximum at about 32 degrees C, whereas the enthalpy of activation delta H and the entropy of activation delta S are zero at about 15 degrees C and 32 degrees C, respectively. These temperatures are slightly dependent upon the concentration of urea and upon whether the reaction is run in a 1H or a 2H medium. Furthermore, from the kinetic point of view, at low temperature the reaction can be characterized as enthalpy driven, whereas at high temperature, it can be characterized as entropy driven.
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Affiliation(s)
- B Sjöberg
- Department of Medical Biochemistry, University of Göteborg, Sweden
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126
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Bauer R, Behan M, Clarke D, Hansen S, Jones G, Mortensen K, Pedersen JS. Contrast variation studies of clathrin coated vesicles by small-angle neutron scattering. Eur Biophys J 1992; 21:129-36. [PMID: 1396402 DOI: 10.1007/bf00185427] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Structural information on clathrin coated vesicles has been obtained by small angle neutron scattering using contrast variation. A characteristic peak in the neutron scattering profile, which is apparent in 75% D2O, as well as in H2O, disappears when contrast matching the protein component of the coated vesicles in 42% D2O. Neutron, as well as dynamic, light scattering give a coated vesicle size of about 900 A in H2O and D2O, but for neutron scattering the diameter decreases when matching out the protein coat of the clathrin coated vesicles. From the match point for the clathrin coated vesicles it is demonstrated that the clathrin cages do contain internal membrane. The mass of 34 MD and composition of 75% protein and 25% lipid found from the analysis of the small-angle scattering data are both in good agreement with the values reported in the literature. Electron microscopy gives an average outer diameter of 880 A for the coated vesicles and an average diameter of 460 A for the vesicle itself.
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Affiliation(s)
- R Bauer
- Royal Veterinary and Agricultural University, Department of Mathematics and Physics, Denmark
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127
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Mortensen K, Brown W, Nordén B. Inverse melting transition and evidence of three-dimensional cubatic structure in a block-copolymer micellar system. Phys Rev Lett 1992; 68:2340-2343. [PMID: 10045370 DOI: 10.1103/physrevlett.68.2340] [Citation(s) in RCA: 159] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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128
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Abstract
A case-control study was conducted to study the proposed inverse relationship between breast feeding and incidence of Type 1 diabetes mellitus. All Danish diabetic men born in Copenhagen during 1959-1964 and/or residing there for the first year of life (n = 119) were identified and a search made for their post-natal health visitor records. These include data on birth weight, birth length, immunizations, and feeding habits. A total of 77 cases were re-identified. No differences were found with respect to clinical characteristics between these cases and those not identified. For each diabetic subject, two control children with date of birth identical to the diabetic cases were drawn from health visitor records. Cases and controls did not differ with respect to maternal age, or birth weight or length. Overall, the statistical analysis failed to confirm the hypothesis of an association between duration of breast feeding and subsequent diabetes risk.
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Affiliation(s)
- K O Kyvik
- Department of Medical Genetics, Institute of Community Health, Odense University, Denmark
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129
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Green A, Andersen PK, Svendsen AJ, Mortensen K. Increasing incidence of early onset type 1 (insulin-dependent) diabetes mellitus: a study of Danish male birth cohorts. Diabetologia 1992; 35:178-82. [PMID: 1547924 DOI: 10.1007/bf00402552] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
To provide information of the incidence trends of Type 1 (insulin-dependent) diabetes mellitus we performed a cohort study of a series of Danish male birth cohorts. All male livebirths in Denmark between 1 January 1949 and 31 December 1964, were investigated regarding the development of Type 1 diabetes during the first 20 years of life using the files of the Danish Conscript Board, supplemented by a search in the Danish National Registry of Deaths. Diagnosis was verified and clinical information obtained from medical records. The material is estimated to be more than 95% complete. A total of 1705 diabetic subjects were identified of whom 23 were not representative of idiopathic Type 1 diabetes. The cumulative rate of Type 1 diabetes development during the first 20 years of life increased from 2.37 to 2.90 per 1000 for the first eight and last eight birth cohorts, respectively. A log-linear analysis of the incidence revealed significantly increasing incidence rates, independent of age effects, with a maximum in the late 1970's. About 75% of the cases presented short duration of symptoms prior to diagnosis, and only very few cases were diagnosed incidentally. Cases were diagnosed relatively less frequently during summer months than during winter months.
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Affiliation(s)
- A Green
- Institute of Clinical Genetics, Odense University, Denmark
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130
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Laalami S, Sacerdot C, Vachon G, Mortensen K, Sperling-Petersen HU, Cenatiempo Y, Grunberg-Manago M. Structural and functional domains of E coli initiation factor IF2. Biochimie 1991; 73:1557-66. [PMID: 1805969 DOI: 10.1016/0300-9084(91)90191-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Initiation of translation in prokaryotes requires the participation of at least three soluble proteins: the initiation factors IF1, IF2 and IF3. Initiation factor 2, which is one of the largest proteins involved in translation (97.3 kDa) has been shown to stimulate in vitro the binding of fMet-tRNA(fMet) to the 30S ribosomal subunit. After formation of 70S translation initiation complex, IF2 is believed to participate in GTP hydrolysis, thereby promoting its own release. Here we review evidence which indicates the functional importance of the different structural domains of IF2, emphasizing new information obtained by in vivo experiments.
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Affiliation(s)
- S Laalami
- Institut de Biologie Physico-Chimique, Paris, France
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131
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Bauer R, Behan M, Hansen S, Jones G, Mortensen K, Særmark T, Øgendal L. Small-angle scattering studies on clathrin-coated vesicles. J Appl Crystallogr 1991. [DOI: 10.1107/s0021889891001279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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132
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Osterberg R, Malmensten B, Boive T, Nilsson U, Stigbrand T, Mortensen K. Correlation between the human and porcine complement system: a small-angle scattering study of cross immunity and methylamine-induced conformational changes of porcine C3 and C4 proteins. Mol Immunol 1991; 28:959-63. [PMID: 1922110 DOI: 10.1016/0161-5890(91)90181-i] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The porcine complement proteins C3 and C4 have been isolated and then characterized using small-angle scattering methods. Within the limits of experimental errors, the porcine proteins are virtually identical with the corresponding human proteins as measured in terms of mol. wt, Mr and radius of gyration, R,: Mr(C3) = 198,000, Mr(C4) = 207,000, and R(C3) = 4.4 nm, R(C4) = 4.5 nm. The C3 and C4 proteins from pigs show cross-immunity with monoclonal antibodies (mAbs) raised against human C3 and C4, respectively. Using the Fab fragments of these mAbs as markers, it is indicated that porcine C3 and C4 undergo a conformational change after reaction with methylamine. The relatively large increase in the radius of gyration observed, delta R = 1.0-1.2 nm, going from the Fab complexes to the Fab complexes of the methylamine derivatives, is similar to that observed for human C3 under similar conditions. This may indicate that methylamine cleaves a labile thiol ester bond supposed to be present within the porcine proteins and that the epitopes interacting with the Fab fragments are very similar to those of the human proteins. Porcine C3 also resembles the human analogue by forming dimers after being subjected to methylamine and dilute lauryl sulphate: Mr = 404,000 and R = 7.9 nm.
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Affiliation(s)
- R Osterberg
- Department of Chemistry, Swedish University of Agricultural Sciences, Uppsala
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133
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Sjöberg B, Pap S, Järnberg SE, Mortensen K. Kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin as measured by small-angle neutron scattering. Biochem J 1991; 278 ( Pt 2):325-8. [PMID: 1716880 PMCID: PMC1151343 DOI: 10.1042/bj2780325] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The kinetics of the urea-induced dissociation of human plasma alpha 2-macroglobulin into two half-molecular fragments was investigated at 21.0 degrees C by using small-angle neutron scattering. The relative change in molecular mass that occurs upon dissociation was monitored by recording the forward scattering of neutrons as a function of time. All these kinetic data can be explained by a reaction that is first-order with respect to the concentration of undissociated alpha 2-macroglobulin. The velocity constant is a function of urea concentration and it varies within wide limits. For instance, the half-life of the reaction at the lowest concentration of [2H]urea studied (2.70 M) is 328 h, whereas the same value at the highest concentration of [2H]urea (6.24 M) is only 8 min. Measurements were made both with [1H]urea in 1H2O and with [2H]urea in 99% 2H2O, and it was found that there is a pronounced kinetic isotope effect, i.e. the dissociation is 4 times faster in the 1H-containing medium as compared with the 2H-containing medium at the same molar concentration of urea. From the angular dependence of the neutron scattering it can be concluded that the dissociation is associated with a drastic change in structure. This is directly shown by the radius of gyration, which increases from about 7.4 nm immediately after the addition of urea up to about 9.4 nm when the protein is fully dissociated. A structural analysis shows that the scattering curve of urea-dissociated alpha 2-macroglobulin can best be explained by that of a Gaussian coil with a radius of gyration equal to 9.44 nm. These data indicate that the so-called non-covalent interaction of alpha 2-macroglobulin probably is more complicated than just a pure hydrophobic interaction. Finally, it is also shown that the dissociation is accompanied by a loss in trypsin-binding activity, which is directly related to the fraction of dissociated protein.
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Affiliation(s)
- B Sjöberg
- Department of Medical Biochemistry, University of Göteborg, Sweden
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134
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Lederer H, Mortensen K, May RP, Baer G, Crespi HL, Dersch D, Heumann H. Spatial arrangement of sigma-factor and core enzyme of Escherichia coli RNA polymerase. A neutron solution scattering study. J Mol Biol 1991; 219:747-55. [PMID: 2056537 DOI: 10.1016/0022-2836(91)90669-w] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
By means of neutron solution scattering we determined the position and orientation of core enzyme and sigma-factor within the Escherichia coli RNA polymerase holoenzyme with the aim of improving existing models. The individual components, core enzyme (E) and sigma-factor (sigma), were highlighted by deuterium labeling and their center-to-center distances determined in the monomeric and the dimeric holoenzyme. The following distance parameters were obtained: dE1-sigma 1 = 8.6(+/- 1) nm, dE1-E2 = 11.5(+/- 1) nm, d sigma 1-sigma 2 = 12.0(+/- 0.7) nm, dE1-sigma 2 = 9(+/- 3) nm. Using a triangulation procedure the position of the sigma-factors, sigma 1 and sigma 2, were determined with respect to the mass center of the core enzyme molecules, E1 and E2, assuming a symmetrical arrangement of the holoenzyme molecules in the dimer (C2 symmetry). In addition, the orientation of the sigma-factor with respect to core enzyme was estimated by means of model calculations. The obtained model of holoenzyme depicts the sigma-factor as buried in a groove of core enzyme, probably between the large subunits beta' and beta.
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Affiliation(s)
- H Lederer
- Max-Planck-Institut für Biochemie, Martinsried, Germany
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135
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Mortensen K. Frustration in the Si(111) "pseudo 5 x 5" Cu structure directly observed by scanning tunneling microscopy. Phys Rev Lett 1991; 66:461-464. [PMID: 10043813 DOI: 10.1103/physrevlett.66.461] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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136
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Mortensen K, Chen DM, Bedrossian PJ, Golovchenko JA, Besenbacher F. Two reaction channels directly observed for atomic hydrogen on the Si(111)-7 x 7 surface. Phys Rev B Condens Matter 1991; 43:1816-1819. [PMID: 9997439 DOI: 10.1103/physrevb.43.1816] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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137
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Nordén B, Elvingson C, Eriksson T, Kubista M, Sjöberg B, Takahashi M, Mortensen K. Structure of a RecA-DNA complex from linear dichroism and small-angle neutron-scattering in flow-oriented solution. J Mol Biol 1990; 216:223-8. [PMID: 2254923 DOI: 10.1016/s0022-2836(05)80311-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Small-angle neutron-scattering (SANS) and ultraviolet linear dichroism (l.d.) were measured on identical samples of a RecA-double-stranded (ds) DNA complex, including cofactor adenosine 5'-O-thiotriphosphate, which were aligned by flow in two equivalent Couette devices made of niobium and silica, transparent to neutrons and to ultraviolet light, respectively. The SANS anisotropy indicates a modest orientation of the RecA-dsDNA fiber with the helix axis parallel to the flow field. By correlation with the corresponding l.d. of the DNA at the same orientation conditions, it is inferred that the DNA bases have a local orientation that is approximately perpendicular to the helix axis. By comparison with the worse orientation in single-stranded DNA-RecA, this conclusion suggests that the dsDNA in its complex with RecA is not strand separated, and may be accommodated as an essentially unperturbed, straight double helix running along the RecA polymer fiber. The SANS anisotropy is also found to support the assignment of a subsidiary intensity maximum as originating from the pitch of a helical fiber.
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Affiliation(s)
- B Nordén
- Department of Physical Chemistry, Chalmers University of Technology, Gothenburg, Sweden
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139
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Pap S, Sjöberg B, Mortensen K. The H(+)-induced dissociation of human plasma alpha 2-macroglobulin. An investigation using small-angle neutron scattering and test of trypsin binding activity. Eur J Biochem 1990; 191:41-5. [PMID: 1696202 DOI: 10.1111/j.1432-1033.1990.tb19091.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The dissociation of the tetrameric alpha 2-macroglobulin molecule into two half-molecular fragments, which occurs at pH less than 4.5, has been investigated using the small-angle neutron scattering method, and test of trypsin binding activity. Best fit with the relative forward scattering of neutrons is obtained for a model where the dissociation of the protein is driven by the uptake of H+ on altogether four acid-base groups, one per monomeric subunit of alpha 2-macroglobulin. These groups are not (or only slightly) accessible in the native tetramer, but become exposed to the solvent after dissociation of the protein. The H(+)-binding constant obtained for these groups, after dissociation of the protein, log K1 in the range 4.2-4.5, suggests that they are most probably carboxylate groups. From the about 10% increase in the radius of gyration, which occurs when lowering the pH from 4.5 to 2.0, we can conclude that the dissociation is associated with a change in structure of the protein. Tests of trypsin binding show that there is also an irreversible loss in trypsin binding activity, which is directly related to the fraction of dissociated protein. Thus, at pH less than 4.5, there is a transition of alpha 2-macroglobulin which results simultaneously in dissociation, disorganisation of the conformation of the subunits and loss in activity.
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Affiliation(s)
- S Pap
- Department of Medical Biochemistry, University of Göteborg, Sweden
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140
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Bedrossian P, Mortensen K, Chen DM, Golovchenko JA. Adatom registry on Si(111)-( sqrt 3 x sqrt 3 )R30 degrees-B. Phys Rev B Condens Matter 1990; 41:7545-7548. [PMID: 9993046 DOI: 10.1103/physrevb.41.7545] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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141
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Christensen K, Henriksen P, Mortensen K, Sørensen H. Metabolic tyrosine disorder in mink and PLP therapy of hereditary tyrosinemia. Amino Acids 1990. [DOI: 10.1007/978-94-011-2262-7_92] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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142
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Schouten M, Dorrepaal J, Stassen W, Vlak W, Mortensen K. Thermal stability of polystyrene-b-poly(ethylene/propylene) diblock copolymer micelles in paraffinic solvents. POLYMER 1989. [DOI: 10.1016/0032-3861(89)90291-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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143
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144
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Bedrossian P, Meade RD, Mortensen K, Chen DM, Golovchenko JA, Vanderbilt D. Surface doping and stabilization of Si(111) with boron. Phys Rev Lett 1989; 63:1257-1260. [PMID: 10040516 DOI: 10.1103/physrevlett.63.1257] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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145
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Chen DM, Golovchenko JA, Bedrossian P, Mortensen K. Tunneling images of gallium on a silicon surface: Reconstructions, superlattices, and incommensuration. Phys Rev Lett 1988; 61:2867-2870. [PMID: 10039248 DOI: 10.1103/physrevlett.61.2867] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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146
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Abstract
A novel, fully automated high-stability, high-eigenfrequency scanning tunnelling microscope (STM) has been developed. Its key design feature is the application of two piezoelectric ceramic tubes, one for the x-y-z motion of the tip and one for a linear motor ('nano-worm') used for the coarse positioning of the tip relative to the specimen. By means of the nano-worm, the tip can be advanced in steps between 16 and 0.2 nm. The walking distance is greater than 2 mm, with a maximum speed of 2000 steps/s. The nano-worm positioning implies that this STM is fully controlled by electronic means, and that no mechanical coupling is needed, which makes operation of the STM extremely convenient. The axial-symmetry construction is rigid, small and temperature-compensated, yielding reduced sensitivity to mechanical and acoustic vibrations and temperature variations. The sample is simply placed on a piece of invar which surrounds the scanner tube and the nano-worm and is held by gravity alone. This allows for easy sample mounting. The performance of the microscope has been tested in air by imaging a variety of surfaces, including graphite and biological samples.
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Affiliation(s)
- E Laegsgaard
- Institute of Physics, University of Aarhus, Denmark
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147
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Mortensen K, Pfeiffer W, Sackmann E, Knoll W. Structural properties of a phosphatidylcholine-cholesterol system as studied by small-angle neutron scattering: ripple structure and phase diagram. Biochim Biophys Acta 1988; 945:221-45. [PMID: 3191122 DOI: 10.1016/0005-2736(88)90485-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Small-angle neutron scattering has been used to study structural features of lamellar bilayer membranes of dimyristoylphosphatidylcholine (DMPC) and DMPC mixed with various amount of cholesterol. The studies were recorded at a fixed hydration level of 17% 2H2O, i.e. just below saturation. Bragg reflections gives information on the ripple structure and on the bilayer periodicity. The crystalline Lc phase, which was stabilized after long time storage at low temperature, exhibits major small angle scattering when cholesterol is mixed into the membrane. The intermediate P beta' gel-phase, which is characteristic by the rippled structure, is dramatically stabilized by the introduction of cholesterol. The ripple structure depends significantly both on the cholesterol content and on the temperature. At high temperatures, T greater than 15 degrees C, the inverse ripple periodicity varies basically linearly with cholesterol content, and approach zero (i.e. periodicity goes to infinite) at 20 mol% cholesterol, approximately. At lower temperatures the correlation is more complex. The data indicate additional phase boundaries below 2 mol% and at approx. 8 mol%. Secondary rippled structures are observed in the low temperature L beta'-phase for cholesterol content below approx. 8 mol%. The data gives detailed insight into the phosphatidylcholine cholesterol phase diagram, which is discussed on the basis of a simple model in which the cholesterol complexes are fixed to the defect stripes of the rippled structure.
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Affiliation(s)
- K Mortensen
- Physics Department, Rise National Laboratory, Riskilde, Denmark
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148
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Hosltborg L, Callesen K, Mortensen K. [An entirely different 24-hour home care than 10 years ago. Interview by Annelise Mølvig]. Sygeplejersken 1988; 88:10-2. [PMID: 3388221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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149
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Schwahn D, Mortensen K, Springer T, Yee‐Madeira H, Thomas R. Investigation of the phase diagram and critical fluctuations of the system polyvenylmethylether and d‐polystyrene with neutron small angle scattering. J Chem Phys 1987. [DOI: 10.1063/1.453482] [Citation(s) in RCA: 67] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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150
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Brereton MG, Fischer EW, Herkt‐Maetzky C, Mortensen K. Neutron scattering from a series of compatible polymer blends: Significance of the Flory χF parameter. J Chem Phys 1987. [DOI: 10.1063/1.453489] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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