摘要:

The physicochemical surface characteristics of a Tn-5 induced hydrophobic mutant (CE3003) ofRhizobium etliCE3 were investigated. The wild type CE3 was very hydrophilic with low contact angles for polar liquids, while the Tn-5 induced mutant had a surface that was moderately hydrophobic, with polar liquid contact angles in the 50–60° range. As a result, the polar surface free energy components (γ+and γ-) that constitute the acid-base component (γAB) of surface tension, were greatly reduced on THE surface of the hydrophobic mutant. This decreased electron donicity of the mutant' surface caused an almost five fold increase in the magnitude of the acid-base component of the interfacial interaction free energy between the mutant and hexadecane. The increased adhesion to hexadecane reported earlier is probably attributable to this interaction free energy change and not to any alteration in zeta potential, which was similar for CE3 and CE3003 at pH 7. X-ray photoelectron spectroscopy showed CE3OO3 to have less surface carbon and nitrogen and more surface oxygen than CE3 with alterations in the (C-C,H) and (C-O,N) components being observed.

ISSN:0193-2691    

DOI:10.1080/01932699808913230

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Bioremediation is a common treatment technology considered for the remediation of many toxic and hazardous waste sites. In order for this technology to be successfully implemented, the mobility and adhesion characteristics of the microorganisms must be understood. This study explored the surface and adhesion characteristics of two pseudomonads:Pseudomonas aeruginosaOlin andP. fluorescens rib:lux. In general, the Lewis acid/base character of these microorganisms dominated surface thermodynamics. In both cases partitioning to dolomite, a common mineral, was predicted to be greatest in the stationary phase. In the log growth and decay phases, the Lewis acid/base interaction energy was repulsive for both organisms. The stationary phase for both microbes exhibited a reversal of the Lewis acid/base energy to attractive. Although the magnitude of the various surface energy components differed between the microorganism, it is remarkable that the Lewis acid/base energy exhibited similar behavior.

ISSN:0193-2691    

DOI:10.1080/01932699808913231

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Surfaces coated with poly(ethylene oxide) containing nonionic polymers are of interest in medical applications due to, among other things, the low adsorption of proteins on such surfaces. In this paper we have studied the interfacial properties of surfaces coated with PEO by measuring the forces acting between two such surfaces in water and across a protein solution as well as between one such surface and a surface carrying adsorbed proteins. One type of surface coating was a graft copolymer of poly(ethylene imine) and poly(ethylene oxide) where the cationic poly(ethylene imine) group anchored the polymer to negatively charged mica surfaces. Three different ways to prepare this coating was used and compared. It was found that this coating was not stable in the presence of lysozyme, a small positively charged protein, when the PEO graft density was low. The other type of coating was obtained by adsorbing ethyl(hydroxyethyl)-cellulose onto hydrophobised mica surfaces. The driving force for adsorption is in this case the hydrophobic interaction between nonpolar segments of the polymer and the surface. The EHEC coating was stable in the presence of lysozyme and the interactions between adsorbed layers of lysozyme and EHEC coated surfaces are purely repulsive due to long-range steric forces.

ISSN:0193-2691    

DOI:10.1080/01932699808913232

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The major cause of fouling of processing equipment in the Dairy Industry used for the pasteurization of milk and whey resides in particle formation in the bulk of the dairy fluid. As a result of processing at elevated temperatures, the heat sensitive whey proteins aggregate and calcium phosphate becomes insoluble and precipitates. Hence, the process of fouling can be understood as a subsequent deposition of these particles onto the heating surface.

ISSN:0193-2691    

DOI:10.1080/01932699808913233

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The thermodynamic conditions for the engulfment of one set of particles by another has been given in terms of interfacial energies. Experimentally, it has been shown that a polymer with a high glass transition temperature can be engulfed by a particle of low glass transition temperature; also, that Inorganic particles can be engulfed by polymer particles. As a precursor to the engulfment stage heterocoagulation can be used for bringing the particles together in a ‘sticking’ mode. This appears to be a general process which is applicable to a number of scientific areas, e.g. in biology, phagocytosis, and in material science for the preparation of composite particles.

ISSN:0193-2691    

DOI:10.1080/01932699808913234

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The dependence of cell or bacteria adhesion and growth on the polarity of a polymer substrate, as controlled by the composition of a HEMA-EMA copolymer, has been studied by contact angle measurements. These have been analyzed by the acid/base hydrogen bonding methodology of van Oss, et al. It was found that adhesion and growth of mouse 3T3 cells occurred on surfaces for which the acidic parameter, γ⊕S, was negligibly small. This was the case above 50% EMA, for which γpwas zero, and both attachment and growth occurred. The γ⊕parameter was appreciable, but approximately constant, independent of composition of the copolymer. The acid/base theory thus supplants the simple polar-nonpolar (γpandγd) hypothesisin regard to cell adhesion. A new 3-dimensional representation of hydrophilic/hydrophobic behavior is suggested, to implement the acid/base description.

ISSN:0193-2691    

DOI:10.1080/01932699808913235

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We sought to determine the influence of the growth temperature on the surface physicochemical properties and adhesion of Bacillus cereus and Bacillus subtilis. Growth temperature did not affect the surface characteristics of Bacillus cereus. With respect to the surface characteristics of the bacteria, water contact angle values indicated a hydrophilic nature for the vegetative forms of Bacillus subtilis with the exception of vegetative form cultured at 44°C which, like the sporulated forms of the two species, was more hydrophobia When Bacillus subtilis was cultured at a temperature other than the optimum growth temperature, its global charge was increased; the more distant the culture temperature from the optimum temperature (30°C), the higher the negative charge. Furthermore, using a tensiometric method, we demonstrated a production of surfactant by Bacillus subtilis. The rate of production rose the closer the growth temperature was to the optimum temperature. In line with the forecasts made on the basis of bacterial energy characteristics and those of a polyurethane surface, the growth and adhesion temperature only had a slight influence on the number of adherent cells.

ISSN:0193-2691    

DOI:10.1080/01932699808913236

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Most antigenic sites of proteins, known as discontinuous epitopes, are made up of residues on different loops that are brought together by the folding of the polypeptide chain. The individual loops are sometimes able, on their own, to bind to the antibody and they are then known as continuous epitopes. The binding sites of antibodies, known as paratopes, are built up from residues on six hypervariable loops known as complementarity determining regions (CDRs). Peptides corresponding to individual CDR loops are often able to bind the antigen and such peptides may be viewed as continuous paratopes. Using random combinatorial peptide libraries, it is possible to obtain peptides that bind to an antiprotein antibody without showing any sequence similarity with any part of the protein. Such epitope mimics are called mimotopes provided they are able also to elicit antibodies that react with the original antigen. The binding activity of mimotopes may partly be due to the phenomenon of hydropathic complementarity between epitope and paratope peptides. Although these concepts are vague in their structural connotation, they are useful for describing the immunological activity of linear peptides.

ISSN:0193-2691    

DOI:10.1080/01932699808913237

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

From surface tensions of liquids and Lifshitz-van der Waals (LW) and Lewis acid-base (AB) surface tension components and the AB electron-acceptor γ+and electron-donor γ˙parameters determined by contact angle (θ) measurements (using the Young-Dupré equation for polar systems), the interfacial work of salvation (Wst) between various contact angle liquids (L) and a moderately polar solid (S), such as polymethylmethacrylate (PMMA) could be determined. From these WSL-values the maximum values of the equilibrium association constant, Ka, are obtained for the adsorption of molecules of liquids, L, onto a solid substratum, S. From the Ka-values and the vapor pressures of the various liquids, the maximum number of liquid molecules adsorbed from the gaseous phase onto the solid surface can be determined, at 20°C and 76cm Hg ambient atmospheric pressure. This yields the maximum value for the fraction, ϕ, of the surface area of the solid that will be covered by molecules of the liquid, L, emanating from the liquid drop, via the gaseous state. From these ϕ-values, using Cassie's approach, the maximum amount, Δθ, can be determined by which the observed contact angle is lower than the ideal contact angle, as a consequence of the coverage of the solid substratum by adsorbed molecules originating from the contact angle liquid.

ISSN:0193-2691    

DOI:10.1080/01932699808913238

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor