Relationship between air-water interfacial dilational viscoelasticity and foam property in aqueous solutions of sodium alkylsulfates with different hydrocarbon chains

This paper describes observations on monomolecular surface films of the long chain amines, C n H 2n+1 NH 2 , on aqueous solutions of different acidities. The lengths of the hydrocarbon chains were varied from 14 to 20 carbon atoms, five members of the series (with 14, 16, 17, 18 and 20 carbons) being used. The acidity of the solutions was varied from N/10 alkali to N/10 acid, using buffered solutions for most of the intermediate acidities. The dilution of the buffer solutions was also varied in some instances. The results indicate that the acidity of the solution is by no means the only factor affecting the structure of the films, and indeed the P H of the solution, on the acid side of neutrality, seems to be of little importance ; but the structure of the films depends very much indeed on the nature of the anions present in the buffer solutions. Entirely different results are obtained on phthalate and acetate buffers, and there is little doubt that the films measured on solutions on the acid side of neutrality are not those of the amines at all, but of their salts with whatever acid radicals are present in the water.

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Conductometric study of hydrophobic interactions in aqueous solutions of double long-chain electrolytes

Australian Journal of Chemistry ◽

10.1071/ch9732649 ◽

1973 ◽

Vol 26 (12) ◽

pp. 2649 ◽

Cited By ~ 11

Author(s):

DG Oakenfull ◽

DE Fenwick

Keyword(s):

Aqueous Solutions ◽

Chain Length ◽

Hydrophobic Interaction ◽

Hydrophobic Interactions ◽

Ion Pairs ◽

Hydrocarbon Chain ◽

Hydrocarbon Chain Length ◽

Hydrocarbon Chains ◽

Methylene Groups ◽

Conductometric Study

We report measurements of the equivalent conductance (Λ) of aqueous solutions of a series of decyl- and hexadecyl-trimethylammonium carboxylates (acetate to undecanoate). In the decyl series, measurements were made on both sides of the critical micelle concentration (CMC). The CMC decreased when the hydrocarbon chain length of the carboxylate ion increased. In the hexadecyl series, measurements were confined to micellar solutions. �� The results obtained below the CMC suggest that hydrophobic interaction between the hydrocarbon chains of decyltrimethylammonium undecanoate, decanoate, and nonanoate leads to the formation of ion- pairs. There was no evidence, however, for formation of ion-pairs by the shorter carboxylates. �� By assuming that micellar ions obey the Onsager equation, we have derived a theoretical relationship between Λ and concentration above the CMC. An excellent fit of theoretical curve to experimental points can be obtained by adjusting the value of a single parameter. This parameter is {(m+1)/n}Kmic (where Kmic is the association constant for binding the carboxylate ion to the micelle and m/n is the ratio of tetra-alkylammonium ions to carboxylate ions in the micelle). �� Plots of -RT ln[{(m+1)/n}Kmic] against the number of methylene groups on the carboxylate ion are linear for both series, which suggests that m/n is independent of the chain length of the carboxylate ion. Both lines have a slope equal to N�methy and Scheraga's estimate of the free energy of hydrophobic interaction between two methylene groups (-1.40 kJ/mol).

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Ultrathin frozen sections of yeast without aldehyde prefixation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081152 ◽

1978 ◽

Vol 36 (2) ◽

pp. 58-59

Author(s):

K. J. Böhm ◽

a. E. Unger

Keyword(s):

Aqueous Solutions ◽

Biological Material ◽

Yeast Cells ◽

Frozen Sections ◽

Good Preservation ◽

Ultrathin Frozen Sections

During the last years it was shown that also by means of cryo-ultra-microtomy a good preservation of substructural details of biological material was possible. However the specimen generally was prefixed in these cases with aldehydes.Preparing ultrathin frozen sections of chemically non-prefixed material commonly was linked up to considerable technical and manual expense and the results were not always satisfying. Furthermore, it seems to be impossible to carry out cytochemical investigations by means of treating sections of unfixed biological material with aqueous solutions.We therefore tried to overcome these difficulties by preparing yeast cells (S. cerevisiae) in the following manner:

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Direct visualization of phase-separated domains in lipid membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100082315 ◽

1978 ◽

Vol 36 (2) ◽

pp. 290-291

Author(s):

S. W. Hui ◽

T. P. Stewart

Keyword(s):

Lipid Membranes ◽

Structural Information ◽

Freeze Fracture ◽

Biological Molecules ◽

Vacuum Drying ◽

Direct Visualization ◽

X Ray Diffraction ◽

Electron Microscopic ◽

X Ray ◽

Hydrocarbon Chains

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.

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Imaging polymers, proteins and dna in aqueous solutions with the atomic force microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152136 ◽

1989 ◽

Vol 47 ◽

pp. 32-33

Author(s):

S.A.C. Gould ◽

B. Drake ◽

C.B. Prater ◽

A.L. Weisenhorn ◽

S.M. Lindsay ◽

...

Keyword(s):

Amino Acids ◽

Dna Sequencing ◽

Aqueous Solutions ◽

Atomic Force Microscope ◽

Piezoelectric Crystal ◽

Atomic Force ◽

Structure Of Molecules ◽

Optical Lever

The atomic force microscope (AFM) is an instrument that can be used to image many samples of interest in biology and medicine. Images of polymerized amino acids, polyalanine and polyphenylalanine demonstrate the potential of the AFM for revealing the structure of molecules. Images of the protein fibrinogen which agree with TEM images demonstrate that the AFM can provide topographical data on larger molecules. Finally, images of DNA suggest the AFM may soon provide an easier and faster technique for DNA sequencing.The AFM consists of a microfabricated SiO2 triangular shaped cantilever with a diamond tip affixed at the elbow to act as a probe. The sample is mounted on a electronically driven piezoelectric crystal. It is then placed in contact with the tip and scanned. The topography of the surface causes minute deflections in the 100 μm long cantilever which are detected using an optical lever.

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