Proton- and deuteron spin targets in bioligical structure research

Stuhrmann, H. B.; Burkhardt, Nils; Dietrich, G.; Jünemann, Ralf; Meerwinck, W.; Schmitt, Matthias; Wadzack, Jörg; Willumeit‐Römer, Regine; Zhao, Jinkui; Nierhaus, Knud H.

doi:10.1016/0168-9002(94)01461-2

Cited by 82 publications

(115 citation statements)

References 19 publications

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“…SANS experiments were performed using the SANS-1 instrument at the GKSS research center in Geesthacht, Germany. 40 Several sample-to-detector distances (from 0.7 to 9.7 m) and a wavelength of 8.1 Å were employed to cover the range of scattering vector q from 0.005 to 0.3 Å -1 . The wavelength resolution of the SANS-1 is 10% (full width at half-maximum).…”

Section: Methodsmentioning

confidence: 99%

Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gemini Surfactants and a Conjugated Polyanion: Experimental and Molecular Modeling Studies

et al. 2007

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Understanding factors responsible for the fluorescence behavior of conjugated polyelectrolytes and modulation of their behavior are important for their application as functional materials. The interaction between the anionic poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}copolymer (PBS-PFP) and cationic gemini surfactants R,ω-(C m H 2m+1 N + (CH 3 ) 2 ) 2 (CH 2 ) s (Br -) 2 (m-s-m; m ) 12, s ) 2, 3, 5, 6, 10, and 12) has been studied experimentally in aqueous solution. These surfactants are chosen to see whether molecular recognition and self-assembly occurs between the oppositely charged conjugated polyelectrolyte and gemini surfactant when the spacer length on the surfactant is similar to the intercharge separation on the polymer. Without surfactants, PBS-PFP exists as aggregates. These are broken up upon addition of gemini surfactants. However, as anticipated, the behavior strongly depends upon spacer length (s). Fluorescence measurements show three surfactant concentration regimes: At low concentrations (<2 × 10 -6 M) quenching occurs and is most marked with the small spacer 12-2-12; at intermediate concentrations (∼2 × 10 -6 -10 -3 M), fluorescence intensity is constant, with a 12-carbon spacer 12-12-12 showing the strongest fluorescence; above the critical micelle concentration (CMC; ∼10 -3 M) increases in emission intensity are seen in all cases and are largest with the intermediate spacers 12-5-12 and 12-6-12, where the spacer length most closely matches the distance between monomer units on the polymer. With longer spacer length surfactants, surface tension measurements for concentrations below the CMC reveal the presence of polymer-surfactant aggregates at the air-water interface, possibly reflecting increased hydrophobicity. Above the CMC, small-angle neutron scattering experiments for the 12-6-12 system show the presence of spherical aggregates, both for the pure surfactant and for polyelectrolyte/gemini mixtures. Molecular dynamics simulations help rationalize these observations and show that there is a very fine balance between electrostatic and hydrophobic interactions. With the shortest spacer 12-2-12, Coulombic interactions are dominant, while for the longest spacer 12-12-12 the driving force involves hydrophobic interactions. Qualitatively, with the intermediate 12-5-12 and 12-6-12 systems, the optimum balance is observed between Coulombic and hydrophobic interactions, explaining their strong fluorescence enhancement.

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Section: Methodsmentioning

confidence: 99%

Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gemini Surfactants and a Conjugated Polyanion: Experimental and Molecular Modeling Studies

et al. 2007

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“…40 Several sample-to-detector distances (from 0.7 to 9.7 m) and wavelengths (from 5.7 to 11.4 Å) were employed to cover the range of the magnitude of scattering vectors q from 0.005 to 0.3 Å -1 . The wavelength resolution of the Yellow Submarine is 20% (fullwidth at half-maximum) while that of the SANS-1 is 10%.…”

Section: Chart 1: Chemical Structure Of the Pbs-pfp Copolymermentioning

confidence: 99%

Solubilization of Polyelectrolytic Hairy-Rod Polyfluorene in Aqueous Solutions of Nonionic Surfactant

Knaapila¹,

Garamus²,

Pearson³

et al. 2006

J. Phys. Chem. B

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We report on the solubilization, phase behavior, and self-organized colloidal structure of a ternary waterpolyfluorene-surfactant (amphiphile) system comprised of polyelectrolytic poly{1,4-phenylene[9,9-bis(4-phenoxybutylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) in nonionic pentaethylene glycol monododecyl ether (C 12 E 5 ) at 20°C. We show in particular how a high amount (milligrams per milliliter) of polyfluorene can be solubilized by aqueous C 12 E 5 via aggregate formation. The PBS-PFP and C 12 E 5 concentrations of 0.31 × 10 -4 -5 × 10 -4 M and 2.5 × 10 -4 -75 × 10 -4 M, respectively, were used. Under the studied conditions, the photoluminescence (PL), surface tension, static contact angle, and (π-A) isotherm measurements imply that D 2 O-PBS-PFP(C 12 E 5 ) x realizes three phase regimes with an increasing molar ratio of surfactant over monomer unit (x). First, for x e 0.5, the mixture is cloudy. In this regime polymer is only partially dissolved. Second, for 1 e x e 2, the solution is homogeneous. In this regime polymer is dissolved down to the colloidal level. Small-angle neutron scattering (SANS) patterns indicate rigid elongated (polymer-surfactant) aggregates with a diameter of 30 Å and mean length of ∼900 Å. The ratio between contour length and persistence length is less than 3. Third, for x g 4, the solution is homogeneous and there is cooperative binding between polymer and surfactant. Surface tension, contact angle, and surface pressure remain essentially constant with increasing x. A PL spectrum characteristic of single separated polyfluorene molecules is observed. SANS curves show an interference maximum at q ∼ 0.015 Å -1 , indicating an ordered phase. This ordering is suggested to be due to the electrostatic repulsion between polymer molecules adsorbed on or incorporated into the C 12 E 5 aggregates (micelles). On dilution the distance between micelles increases via 3-dimensional packing. In this regime the polymer is potentially dissolved down to the molecular level. We show further that the aggregates (x ) 2) form a floating layer at the air-water interface and can be transferred onto hydrophilic substrates.

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“…10 Small-angle neutron scattering experiments have been carried out at the SANS1 instrument at the FRG1 research reactor at GKSS Research Centre, Geestacht, Germany. 21 The measurements have been performed with a neutron wavelength of λ ) 0.81 nm and a wavelength resolution of (∆λ/λ) ) 10%. A range of scattering vectors of 0.05 < q < 2.5 nm -1 was obtained.…”

Section: Methodsmentioning

confidence: 99%

Hyperbranched Polymers: Structure of Hyperbranched Polyglycerol and Amphiphilic Poly(glycerol ester)s in Dilute Aqueous and Nonaqueous Solution

et al. 2004

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The solution structure of hyperbranched macromolecules was investigated by means of smallangle neutron scattering (SANS). Hyperbranched polyglycerols of different molecular weight were investigated in D2O and CD3OD, and very similar molar masses and radii of gyration were obtained in both solvents. Kratky plots of the scattering intensity revealed a compact structure of the hyperbranched polyglycerols. A power law scaling relation of the radius of gyration with molar mass was observed, from which a dimension of three was obtained. These observations indicate that the hyperbranched structure prevents strong irregular association despite the high functionality of hydroxyl groups that could lead to aggregation in those solvents. Amphiphilic derivatives of the hyperbranched polyglycerols have been studied in the nonpolar solvent C 6D6. Again, molecularly dispersed polymers were found provided the degree of esterification was sufficiently high. A low degree of derivatization of only 22% was not sufficient to prevent aggregation in C 6D6. The macromolecules become more compact when the degree of esterification increases.

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Proton- and deuteron spin targets in bioligical structure research

Cited by 82 publications

References 19 publications

Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gemini Surfactants and a Conjugated Polyanion: Experimental and Molecular Modeling Studies

Interplay of Electrostatic and Hydrophobic Effects with Binding of Cationic Gemini Surfactants and a Conjugated Polyanion: Experimental and Molecular Modeling Studies

Solubilization of Polyelectrolytic Hairy-Rod Polyfluorene in Aqueous Solutions of Nonionic Surfactant

Hyperbranched Polymers: Structure of Hyperbranched Polyglycerol and Amphiphilic Poly(glycerol ester)s in Dilute Aqueous and Nonaqueous Solution

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