Solute-solute interactions in aqueous solutions of nonelectrolytes are interpreted using both lattice and distribution function theories of the dissolved state. Experimental activity data of high precision can be obtained from the literature for aqueous solutions of many nonelectrolytes. If the logarithm of the solvent activity coefficient (γ1) is expressed as a power series in the mole fraction of the solute (x2), lnγ1 = Bx22 + Cx23 + ···, then the coefficients B and C can be determined analytically from the experimental measurements. Values of B were obtained for 52 aqueous mixtures; values of C were obtained for 39 of these mixtures. The solutes considered include aliphatic alcohols, amines, amides, ketones, fatty acids, amino acids, and sugars. In some cases, experimental data were available from which the temperature dependence of the quantities B and C could also be determined. The effect of solute size on the coefficients B and C was investigated using the lattice theories of Flory, Huggins, and Guggenheim and McGlashan. More detailed conclusions concerning solute-solute interactions can be drawn by using experimental activity data in conjunction with the McMillan-Mayer theory of solutions. The minimum attractive contributions to the second virial coefficient of the osmotic pressure were estimated for most of the systems studied in this paper. Pairwise attractions seem to increase with (1) increasing aliphatic chain length (from the temperature dependence of the coefficient B it is also found that pairwise association due to aliphatic chains increases with increasing temperature); (2) an increase in the number of solute functional groups capable of participating in hydrogen-bond formation; (3) increasing dipole moment of the solute molecule for a series of amino acids and peptides. The minimum attractive contributions to the third virial coefficient were determined and interpreted for 12 of the systems. Finally, the relative importance of pairwise versus triplet interactions in aqueous solution was investigated.
Both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) male-specific phages, with an F-specific host range, inhibited the bacterial mating process of Escherichia coli. DNA phages prevented the formation of mating pairs but had no effect on mating pairs once they were formed. A step in RNA phage infection, prior to RNA penetration, prevented the formation of mating pairs and, in addition, prevented a fraction of existing mating pairs from completing the mating process. These findings are compatible with the hypothesis that donor cells have a single surface structure involved in both conjugation and male-phage adsorption and that this element is the F pilus.
The extent of removal at various blending speeds (blending spectrum) and the kinetics of reappearance after blending of the ability of male Escherichia coli bacteria to form mating pairs, to adsorb and be infected by ribonucleic acid male phage, and to adsorb and be infected by deoxyribonucleic male phage were identical to the blending spectrum and reappearance kinetics of microscopically visible F pili. The same results were obtained with an Hfr (high-frequency recombinant), F', or resistance transfer factor (RTF) fi+ mating system. Blending did not affect the viability, growth rate, ability to adsorb T4 phage, or ability to produce new F pili at any of the speeds used. It can be concluded that microscopically visible F pili are an absolute requirement for all three functions. Three classes of F pili have been found in bacterial cultures: attached, adsorbed, and free. Bacteria with adsorbed F pili in addition to attached ones were proportionately more susceptible to male phage infection, suggesting that adsorbed F pili may be at least partially functional. Free F pili did not compete with bacteria for phage. Some implications of the viruslike nature of F-pilus outgrowth for the mechanisms of mating and male phage infection are discussed.
In radial partition immunoassay, radial chromatography is used for performing an immunoassay. We describe the application of this technology to the measurement of digoxin in serum by enzyme immunoassay, with the entire testing procedure carried out on glass-fiber filter paper. A sample is applied to a small central area of the filter paper, where it reacts with the antibody to digoxin immobilized there. Subsequently, enzyme-labeled digoxin is applied to react with remaining antibody sites. After incubation, substrate for the enzyme is applied to the center of the reaction area and washes out any unbound label to the periphery of the paper. This step also initiates the enzyme reaction, which is quantified by front-surface fluorescence. A microprocessor-controlled automated instrument has been developed to process the filter paper matrix through the above sequence, and calculate the final result. Total testing time for digoxin is less than 7 min.
Bacteriophage T4 is neutralized by univalent antibody fragment Fab′ with apparent two-target neutralization kinetics. By the use of conditional lethal (amber) T4 mutants, it was shown that partially neutralized preparations of phages adsorb to bacteria with kinetics suggesting a mixture of fast and slow adsorbers; the ratio of fast to slow phages fits well that predicted by Poisson distribution of phages with, respectively, no (zero hit) and one (one hit) Fab′ complexed. A portion of the infectivity of one-hit phages seems due to phage–Fab′ dissociation, but the larger portion (80%) of the infectivity is due to weak adsorption of phages complexed still with one Fab′. It was shown that antibody to tail fiber is responsible for this effect. Phage adsorption heterogeneity was a possible explanation of kinetics obtained using phages which had not been treated with Fab′.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.