THE STRUCTURE OF GELATIN GELS FROM STUDIES OF DIFFUSION<sup>1</sup>

Friedman, Leo; Kraemer, Elmer O.

doi:10.1021/ja01367a001

Cited by 55 publications

(18 citation statements)

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“…This is in accordance with the findings of Smidsrød and Skjåk-Braek (1990) concerning alginate gels. However, these observations were made by experiments conducted either with agar or alginate gels which are characterized by different microstructure, while other authors reported that diffusion of low molecular weight substances like glucose in gelatin gels was affected by varying the polymer concentration (Friedman & Kraemer, 1930;Hendrickx, Ooms, Engels, Pottelbergh, & Tobback, 1987). Theys et al (2008) also concluded that oxygen limitations (decrease in the oxygen diffusion rate) may account for the drop in μ max of S. Typhimurium.…”

Section: Effect Of Glucosementioning

confidence: 99%

Effect of the substrate's microstructure on the growth of Listeria monocytogenes

Aspridou

Moschakis

Βiliaderis

et al. 2014

Food Research International

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Section: Effect Of Glucosementioning

confidence: 99%

Effect of the substrate's microstructure on the growth of Listeria monocytogenes

Aspridou

Moschakis

Βiliaderis

et al. 2014

Food Research International

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“…Friedman and Kraemer (1930) first suggested that the reduced diffusivity in fine pores resulted from increased frictional drag on the solute as a result of the proximity of the solid walls, and for a quantitative estimate they employed the first-order solution of Ladenburg (1907) for the axial sedimentation of a hard sphere through a continuum bounded by a rigid cylinder. Pappenheimer et al (1951) combined this factor with Equation (3) for the partition coefficient.…”

Section: Background and Previous Studiesmentioning

confidence: 99%

Restricted diffusion in liquids within fine pores

1973

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The effect on the liquid-phase effective diffusivity in fine pores of the ratio of solute molecular diameter to pore diameter and of preferential solute adsorption was studied by measurements on homogeneous silicaalumina bead catalyst (pore diameter = 3.2 nm). A proposed empirical correlation is based on the investigation of a variety of binary systems of p a r f f i s and aromatic hydrocarbons and of aqueous solutions of sugars.

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“…These were measured by the method of Friedman & Kraemer (1930). I n this method a layer of agar gel is formed in a cylindrical container, and an equal volume of liquid is placed above it.…”

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confidence: 99%

A General Theory for Plate Assay of Antibiotics with some Practical Applications

Humphrey

Lightbown

1952

Journal of General Microbiology

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SUMMARY: The distribution of antibiotic (or other substance) in the agar around a container or around a hole in a punch-plate can be expressed theoretically by an equation involving: the initial quantity of antibiotic, the depth of the agar layer, the diffusion constant, the concentration a t a given distance from the container, and the time of diffusion. The validity of the equation was confirmed by measurement of the diffusion constants of penicillin, streptomycin and aureomycin, and of the critical concentration of these substances required to inhibit test organisms, followed by the use of the values so obtained to predict the sizes of the inhibition zones produced experimentally by these antibiotics after varying periods of diffusion.The theory predicts that the square of the inhibition zone diameter will be proportional to the logarithm of the antibiotic concentration. This relationship was found to hold, when accurate assays were made, for a number of antibiotics but not for penicillin when tested with Bacillus subtilis. The most important factor determining the slope of the dose-response curve under given conditions is the diffusion constant of the antibiotic. The slope can, however, be increased by prolonging the time allowed for diffiusion.Particular factors which affected both the sharpness of the zone edge and the nature of the dose-response curve were production of small amounts of penicillinase by strains of B . subtilis used for penicillin assay, and uptake of streptomycin by organisms used for streptomycin assay. Measurements of adsorption of streptomycin by B. subtilis, B. pumilus and by Staphylococcus aureus were made, and were shown to fit equations of the Freundlich isotherm type.Although very good plate assay methods are available for penicillin and streptomycin, those described for the newer antibiotics are less satisfactory owing to a tendency for the zone edges to be poorly defined and to shift their position as incubation of the plates is continued. Unless a valid theoretical treatment of the nature of diffusion of an antibiotic from the cup into the surrounding agar gel is available, attempts to investigate the factors governing the nature of the zone edge and the slope of the dose-response curve for new antibiotics will be empirical and time-consuming. The only theoretical treatment of this problem of which we were aware was that given by Cooper & Woodman (1946), who discussed diffusion of antiseptics and of penicillin from a Heatley cup into agar, and claimed good agreement between predicted zone diameters and those which they observed in practice. They used, however, a formula derived from considerations of linear, not radial, diffusion, and assumed that the concentration of antibiotic in the cup was constant during the first 8 hr. These assumptions do not hold in plate assays as often performed, and we decided therefore to investigate the theoretical treatment from first principles. With the aid of certain assumptions, which are discussed below, a theoretical expression was derived, ...

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THE STRUCTURE OF GELATIN GELS FROM STUDIES OF DIFFUSION¹

Cited by 55 publications

References 0 publications

Effect of the substrate's microstructure on the growth of Listeria monocytogenes

Effect of the substrate's microstructure on the growth of Listeria monocytogenes

Restricted diffusion in liquids within fine pores

A General Theory for Plate Assay of Antibiotics with some Practical Applications

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THE STRUCTURE OF GELATIN GELS FROM STUDIES OF DIFFUSION1

Cited by 55 publications

References 0 publications

Effect of the substrate's microstructure on the growth of Listeria monocytogenes

Effect of the substrate's microstructure on the growth of Listeria monocytogenes

Restricted diffusion in liquids within fine pores

A General Theory for Plate Assay of Antibiotics with some Practical Applications

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Product

Resources

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THE STRUCTURE OF GELATIN GELS FROM STUDIES OF DIFFUSION¹