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Digitale Medien

Modified Intercalation Model for the Interaction of Amino Acridines and DNA (1966)

PRITCHARD, N. J. ; BLAKE, A. ; PEACOCKE, A. R.

[s.l.] : Nature Publishing Group

Nature 212 (1966), S. 1360-1361

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ISSN: 1476-4687

Quelle: Nature Archives 1869 - 2009

Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik

Notizen: [Auszug] Fig. 1. Fig. 2. Arrangement of an acridine molecule across a base pair of DNA as proposed by Lerman6. Dotted li acridine. Fig. 3. Perspective view of the modified intercalation model showing an acridine molecule oriented between adjacent bases on a single polynucleo-tide chain; the other chain ...

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1038/2121360a0

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Digitale Medien

Constitutive equations applied to dispersed systems (1974)

Bruijne, D. W. ; Pritchard, N. J. ; Papenhuijzen, J. M. P.

Springer

Rheologica acta 13 (1974), S. 418-423

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ISSN: 1435-1528

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Summary It has been investigated whether constitutive equations, which have been proposed originally to describe the rheological behaviour of polymerlike materials, can be used to represent the rheology of dispersions. Such equations generally predict stresses that depend on both the shear (γ) and a quantity (λ $$\dot \gamma $$ ) which is the product of the shear rate ( $$\dot \gamma $$ ) and the time constant of the material (λ). The behaviour of dispersions depends in general on the concentration of the dispersed particles. The dissipative aspect of the rheological behaviour is almostNewtonian for very dilute dispersions while it becomes plastic for more densely packet dispersions. In the latter case the shear stress is practically independent of the shear rate at low shear rates. Such behaviour may be accounted for in the constitutive equations by assuming λ $$\dot \gamma $$ to be almost constant. This motivated us to choose the equation ofBogue where the relaxation time (λ) depends on the shear rate ( $$\dot \gamma $$ ), according to 1/λ = (1/λ 0) + a $$\dot \gamma $$ , where 1/λ 0 accounts for the viscous behaviour and a $$\dot \gamma $$ for the plastic behaviour. Comparing the actual rheological behaviour of dispersions of fat crystals in paraffin oil with the behaviour predicted by theBogue equation, it turns out that theBogue equation has some success in representing the stress overshoot in steady shear experiments. However, the predicted value of the normal stress for the concentrated dispersions is too low in comparison with the measured value. It is suggested that this discrepancy is due to the dilatant behaviour of these dispersions. Moreover, the values of the dynamic moduli measured in oscillatory shear are predicted incorrectly, due to considerable changes in particle network which already occur at very small deformations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01521736

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Digitale Medien

The ultrasonic degradation of biological macromolecules under conditions of stable cavitation. II. Degradation of deoxyribonucleic acidFor Part I see Pritchard et al.1 (1968)

Peacocke, A. R. ; Pritchard, N. J.

New York : Wiley-Blackwell

Biopolymers 6 (1968), S. 605-623

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Solutions of T7 bacteriophage or calf thymus DNA arc degraded in solution by ultrasonic fields of low intensity in the presence of vibrating air bubbles but are not degraded at these low intensities when such bubbles are absent. Evidence is presented for the hydrodynamic nature of the observed degradation and theoretical simulation of a plausible degradation mechanism is compared with experimental degradation studies. It is concluded that degradation of such linear macromolecules as DNA may occur as a result of stresses induced in the macromolecule; these stresses are the result of a relative movement of solvent molecules and the macromolecules in the time-independent flow of solvent near the vibrating bubbles.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.1968.360060414

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Digitale Medien

The ultrasonic degradation of biological macromolecules under conditions of stable cavitation. I. Theory, methods, and application to deoxyribonucleic acid (1966)

Pritchard, N. J. ; Hughes, D. E. ; Peacocke, A. R.

New York : Wiley-Blackwell

Biopolymers 4 (1966), S. 259-273

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Solutions of calf thymus DNA have been degraded in the presence of vibrating air bubbles in ultrasonic fields of low power which would not normally induce ultrasonic cavitation. The DNA was degraded to a limiting intrinsic viscosity, after which further irradiation by ultrasound had little or no effect. This limiting intrinsic viscosity decreased with increase in the ultrasonic intensity. Previously developed theories have-been adapted to calculate the maximum velocity gradient associated with the streaming of the solution around such vibrating air bubbles. The tensile force which is induced and which acts on the DNA has been calculated on the basis of current theories of degradation by hydrodynamic shear. These calculations indicate that the degradation of the DNA by ultrasound under conditions of “stable cavitation” is mainly the result of the shearing forces engendered in the solution around the oscillating bubbles.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.1966.360040303

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Digitale Medien

Interaction of aminoacridines with deoxyribonucleic acid: Viscosity of the complexes (1966)

Drummond, D. S. ; Pritchard, N. J. ; Simpson-Gildemeister, V. F. W. ; [weitere]

New York : Wiley-Blackwell

Biopolymers 4 (1966), S. 971-987

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The intrinsic, viscosities at zero shear rate of defined complexes of proflavine, 9-aminoacridine, and 9-amino-l,2,3,4-tetrahydroaeridine with calf thymus DNA have been determined at, various ionic strengths by means of rotating cylinder viscometers. By controlled adjustment, of the composition of the mixtures, the amount of bound acridine (r moles/g.-atom DNA phosphorus) was maintained constant at different dilutions. The intrinsic viscosities of the complexes increased with r up to r values (ca. 0.16-0.20) corresponding to the end of the process of strong binding of the acridinium cations. However, complex formation between the acridines and thermally denatured DNA caused either a marked decrease in viscosity (at the low ionic strengths of 0.0015 and 0.005) or no change at all (ionic strength 0.1). These results are discussed in the light of presently available hydrodynamic theories relating the intrinsic, viscosity of DNA to its molecular extension.

Zusätzliches Material: 5 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.1966.360040903

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