Biomedical subjects

R J Good

Publications and source records attributed to R J Good.

9 recordsLinked to original sources

PubMed1988

Orientation of the water molecules of hydration of human serum albumin.

Through contact-angle measurements with a number of liquids, on layers of hydrated human serum albumin (HSA), built on anisotropic ultrafilter membranes, the apolar, Lifshitz-van der Waals surface tension component, as well as the polar, electron-acceptor and electron-donor parameters of the hydrated layers could be determined. From these data, it was found that the degree of orientation of the water molecules of hydration of HSA is approximately 98% in the first layer of hydration and approximately 30% of the second layer. The water molecules of hydration are oriented with the H atoms closest to, and the O atoms farthest from, the protein surface.

Humans↗

PubMed1987

Mechanism of DNA (Southern) and protein (Western) blotting on cellulose nitrate and other membranes.

The transfer of DNA fractions from hydrophilic gels to nitrocellulose membranes (Southern blotting) which was soon followed by the description of an analogous procedure for RNA (Northern blotting), and somewhat later for proteins (Western blotting), has rapidly become an important separation and characterization method in molecular biology, genetic engineering, and immunological detection. Surface tension measurements have shown that the interfacial attraction between DNA and cellulose esters (-delta G132) in aqueous media can be considerable. The weaker binding energy of proteins to cellulose nitrate and to cellulose acetate may be compared to hydrophobic interaction chromatography, as on account of the somewhat lower [-delta G132] values, it often is necessary to "fix" them more tightly onto nitrocellulose by using high salt concentrations. The binding energy of RNA to both cellulose esters also is rather low. In addition to the effect of high ionic strength, the effect of adding methanol, and the effects of denaturation, heating and drying on the energy of attachment of the biopolymers to cellulose esters, have been studied. Cationized nylon membranes have been advocated recently, especially for electrophoretic transfer of nucleic acids (in which process high salt concentrations cannot easily be used). With positively charged nylon membranes, the attachment mainly occurs through the electrostatic attraction between the strongly negatively charged nucleic acids (or proteins) and the positively charged membrane. Also, more apolar membranes (of polyvinyl difluoride) have been proposed, which manifest a strong interfacial (hydrophobic) attraction to all the above biopolymers (regardless of their electrostatic charge). However, with these two novel membrane types it is no longer possible to exploit the large difference in binding energy between DNA and RNA, which makes cellulose nitrate membranes so uniquely suited for RNA-DNA hybridization assays.

Animals↗

PubMed1987

Monopolar surfaces.

Following the development of a methodology for determining the apolar components as well as the electron donor and the electron acceptor parameters of the surface tension of polar surfaces, surfaces of a number of quite common materials were found to manifest virtually only electron donor properties and no, or hardly, any electron acceptor properties. Such materials may be called monopolar; they can strongly interact with bipolar materials (e.g., with polar liquids such as water); but one single polar parameter of a monopolar material cannot contribute to its energy of cohesion. Monopolar materials manifesting only electron acceptor properties also may exist, but they do not appear to occur in as great an abundance. Among the electron donor monopolar materials are: polymethylmethacrylate, polyvinylalcohol, polyethyleneglycol, proteins, many polysaccharides, phospholipids, nonionic surfactants, cellulose esters, etc. Strongly monopolar materials of the same sign repel each other when immersed or dissolved in water or other polar liquids. The interfacial tension between strongly monopolar surfaces and water has a negative value. This leads to a tendency for water to penetrate between facing surfaces of a monopolar substance and hence, to repulsion between the molecules or particles of such a monopolar material, when immersed in water, and thus to pronounced solubility or dispersibility. Monopolar repulsion energies can far outweigh Lifshitz-van der Waals attractions as well as electrostatic and "steric" repulsions. In aqueous systems the commonly observed stabilization effects, which usually are ascribed to "steric" stabilization, may in many instances be attributed to monopolar repulsion between nonionic stabilizing molecules. The repulsion between monopolar molecules of the same sign can also lead to phase separation in aqueous solutions (or suspensions), where not only two, but multiple phases are possible. Negative interfacial tensions between monopolar surfactants and the brine phase can be the driving force for the formation of microemulsions; such negative interfacial tensions ultimately decay and stabilize at a value very close to zero. Strongly monopolar macromolecules or particles surrounded by oriented water molecules of hydration can still repel each other, albeit to an attenuated degree. This repulsion was earlier perceived as caused by "hydration pressure". A few of the relevant colloid and surface phenomena are reviewed and re-examined in the light of the influence of surface monopolarity on these phenomena.

Colloids↗

PubMed1986

Nature of the antigen-antibody interaction. Primary and secondary bonds: optimal conditions for association and dissociation.

All antigen-antibody (AG-AB) bonds are weak physical bonds; covalent bonds are not encountered. The main bonds involved are: (I) Coulombic bonds; (II) Ca2+-bridges; (III) hydrogen bonds; (IV) Lifshitz--van der Waals bonds. Combinations of III and IV occur as the "bonds" usually alluded to as hydrophobic (H phi) interactions. In primary bonds, mainly types I and IV occur; types II and III are quite rare. Secondary bonds, which evolve after a certain time-lapse (varying from minutes to days), mainly involve type IV bonds and H phi interactions, while hydrogen bonds sensu stricto have been known to play a role in rare instances. In affinity chromatography involving AG-AB interactions, complete elution with mild eluents usually is desirable. It would thus appear essential to let little time elapse between AG-AB complex formation and the elution step, to minimize strengthening of the AG-AB interaction by secondary bond formation. For expeditious elution, it also is important to avoid using dehydrating agents (which tend to decrease the bond distance between AG and AB and thus could strengthen the bond in a number of ways). The degree of involvement of types I and IV bonds as well as of H phi interactions varies considerably among different AG-AB systems. These components thus have to be measured separately in order to determine the optimal conditions for elution. The parameters of the liquid medium that may be modulated to influence dissociation (or association) are, for example, surface tension, pH, ionic strength, dielectric constant, temperature, admixture of dehydrating agents or of chaotropic salts. The influence of variations in each of these parameters on types I, III and IV bonds (and thus also on H phi interactions) will be delineated. Because of the misleading implications of the term "hydrophobic interactions", it seems preferable henceforth to allude to them as "interfacial forces".

Animals↗

PubMed1974