Abstracts

M. F. Chaplin, (2019) Structure and properties of water in its various states, Encyclopedia of Water: Science, Technology, and Society, Ed. P. A. Maurice, Wiley, DOI: 10.1002/9781119300762.wsts0002. Water is a unique substance with properties that are not predictable from those of other materials. It has a complex phase space where all of its physical and structural forms possess unexpected properties. Mostly, these are consequences of the ability of the water molecule to form strongly hydrogen-bonded intricate structures. The extensive hydrogen bonding provides water with the ability to transfer protons and electrons rapidly between the water molecules and to produce positively charged hydrogen ions and negatively charged hydroxide ions. Each water molecule forms exactly four hydrogen bonds in a tetrahedral arrangement with two hydrogen atoms near each oxygen atom. This arrangement is also present, if much more loosely, in liquid water, where the overall structuring is far more complex. Such liquid water behaves as though it is a mixture of two liquids that change relative composition with variations in temperature and pressure. The properties of liquid water are particularly affected at low temperatures when supercooled and at very low temperatures when water forms glasses. Even gaseous water is affected by this hydrogen bonding. [Back]

M. F. Chaplin, Interfacial osmotic pressure, Aqua Incognita: why ice floats on water and Galileo 400 years on, Ed. P. Lo Nostro and B. Ninham, ISBN: 9781925138214 (Connor Court, Ballarat, 2014), pp 329-340. The generally accepted view of osmotic pressure is that it is a colligative property, along with freezing point depression, boiling point elevation and vapor pressure lowering. These properties ideally depend on the concentration of dissolved solute molecules. Osmotic pressure, however, is also generated, without any solute, at hydrophilic surfaces and water-gas interfaces. This pressure may oppose gas exit from nanobubbles and so stabilze them. Here is presented a rationale and explanation for these phenomena. [Back]

M. F. Chaplin, What is liquid water, Science in Society, 58 (2013) 41-45, Everyone knows some of the properties of liquid water. Often they think of these properties as typical of liquids in general; for example, most people believe all liquids dissolve gases less well at higher temperatures. This is a mistake as the opposite is true. Liquid water only behaves like most other liquids at very high temperatures (i.e., when superheated) but is strange and atypical at low temperatures. Overall, liquid water can be considered an intimate mixture of two miscible phases, one predominant at lower temperatures and the other predominant at higher temperatures. hydrogen-bonding is generally said to be the cause of these phenomena but confusion still exists over what ‘hydrogen-bonding’ in water entails. No longer should we describe (or model) liquid water in terms of individual water (H₂O) molecules or describe water’s hydrogen bond as simple electrostatic interactions between discrete molecules. We must consider both proton quantum effects and extensive electron delocalization within the network(s) of water molecules (i.e., neither the protons nor electrons are pinned to individual molecules). [Back]

Martin Chaplin, Self-generation of colligative properties at hydrophilic surfaces, arxiv.org:1203.0206 [cond-mat.soft] (2012), The generally accepted view of osmotic pressure is that it is a colligative property, along with the freezing point depression, boiling point elevation and vapor pressure lowering. These properties ideally depend on the concentration of dissolved solute molecules. Osmotic pressure, however, is also generated, without any solute, at hydrophilic surfaces. Here is presented a rationale and explanation for this phenomenon. [Back]

Martin Chaplin, Theory vs experiment: What is the surface charge of water? Water, 1 (2009) 1-28, There is considerable disagreement over whether the gas/liquid surface of the water is positive due to the presence of surface-active hydrogen ions or negative due to the presence of surface-active hydroxyl ions. Much has been written and many experimental and simulation studies have been undertaken. We critically analyze these studies to establish what is known unambiguously and what assumptions underlie these opposite views. The conclusion reached after this examination is that there is much misunderstanding over the strength of the evidence for hydrogen ions being surface active and less support for the positive surface than generally regarded. The surface of neutral water has a negative charge. [Back]

Martin Chaplin, The memory of water; an overview, Homeopathy, 96 (2007) 143-150. The ‘memory of water’ is a concept by which the properties of an aqueous preparation are held to depend on the previous history of the sample. Although associated with the mechanism of homeopathy, this association may mislead. There is strong evidence concerning many ways in which the mechanism of this ‘memory’ may be apparent. There are also mechanisms by which such solutions may possess effects on biological systems which substantially differ from plain water. This paper examines the evidence. [Back]

Martin Chaplin, Opinion: Do we underestimate the importance of water in cell biology?Nature, Reviews Molecular Cell Biology, 7 (11) (2006) 861-866. Liquid water is a highly versatile material. Although it forms from the tiniest of molecules, it can shape and control biomolecules. The hydrogen-bonding properties of water are crucial to this versatility, as they allow water to execute an intricate three-dimensional 'ballet', exchanging partners while retaining complex order and enduring effects. Water can generate small active clusters and macroscopic assemblies, which can both transmit information on different scales. [Back]

Chaplin, M. F., Information Exchange within intracellular water, In, Water and the Cell, Ed. G. H. Pollack, I. L. Cameron and D. N. Wheatley, Springer, (2006) pp. 113-123. A linkage between intracellular phenomena, involving the structuring of water, is described which associates the polarized multilayer theory with gel-sol transitions. Intracellular K⁺ ions are revealed to form ion pairs with acid-rich domains on static proteins, particularly F-actin. Such structures then create low-density water clustering by a cooperative process that influences other sites and so transfer information within the cell. [Back]

M. F. Chaplin. Water structuring at colloidal surfaces, In. Surface Chemistry in Biomedical and Environmental Science, Ed. J. Blitz and V. Gun’ko, NATO Security Through Science, Series, Springer (2006) pp. 1-10. Colloids in contact with water exert control over the arrangement of the first shell of the surrounding water using polar, dispersion and directed hydrogen-bonding effects. The preferred orientations of this first shell water are affected by the favored orientations of the second and more distant aqueous shells. If the colloid surface is flexible, it enables greater freedom of movement within the surface water molecules whereas if the surface is fixed, the adjacent water is more static and more extensively structured. The surface structuring of water is affected by, and will affect, the thermodynamics and kinetics for the binding of other molecules to the surface. In this paper, examples of the organization of water at colloidal surfaces are described and general conclusions are drawn. These examples include (C₆₀-Ih)[5,6] fullerene, β-helix antifreeze proteins, and oxomolybdate clusters. [Back]

M. F. Chaplin. Water's hydrogen bond strength, In: Water and Life, ed. R. M. Lynden-Bell, S. Conway Morris, J. D. Barrow, J. L. Finney and C. L. Harper, Jr. (CRC Press, Boca Raton, 2010) pp. 69-86. Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen-bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low-density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperatures. The quantitative and qualitative consequences of strengthening or weakening of the hydrogen bond in water are considered in this paper. It is found that if the hydrogen bond strength was slightly different from its natural value then there may be considerable consequences for life. At the extremes water would not be liquid on the surface of Earth at its average temperature if the hydrogen bonds were 7% stronger or 29% weaker. The temperature of maximum density naturally occurring at about 4 °C would disappear if the hydrogen bonds were just 2% weaker. Major consequences for life are found if the hydrogen bonds did not have their natural strength. Even very slight strengthening of the hydrogen bonds may have substantial effects on normal metabolism. Water ionization becomes much less evident if the hydrogen bonds are just a few percent stronger but pure water contains considerably more H+ ions if they are few percent weaker. The important alkali metal ions Na⁺ and K⁺ lose their distinctive properties if the hydrogen bonds are 11% stronger or 11% weaker respectively. Hydration of proteins and nucleic acids depends importantly on the relative strength of the biomolecule-water interactions as compared with the water-water hydrogen bond interactions. Stronger water hydrogen-bonding leads to water molecules clustering together and so not being available for biomolecular hydration. Generally, the extended denatured forms of proteins become more soluble in water if the hydrogen bonds become substantially stronger or weaker. If the changes in this bonding are sufficient, present natural globular proteins cannot exist in liquid water. The overall conclusion of this investigation is that water's hydrogen bond strength is poised centrally within a narrow window of its suitability for life. [Back]

Chaplin, M. F., The structure of Plantago ovata arabinoxylan, Gums and Stabilisers for the Food Industry, Ed P. A. Williams and G. O. Phillips, Royal Society of Chemistry, 12 (2004) 509-516. The unusual physicochemical and physiological properties of P. ovata arabinoxylan may be explained directly from the polysaccharide structure. The structural entity involving a β-(1-3)-linked xylose disaccharide attached at the 2-position to the xylan backbone has been found to interact strongly with neighboring arabinose residues and so introduce a conformational lock (or 'kink') into the structure which may be released with a rise temperature. In addition it offers protection to the arabinoxylan chain against enzymatic attack. [Back]

Chaplin, M. F., (2003) Fibre and water binding. Proceedings of the Nutrition Society, 62, 223-227. The range of interactions between fibre and water and the consequential properties of the bound water are modeled and examined. Dietary fibre may interact with water by means of polar and hydrophobic interactions, hydrogen-bonding and enclosure. The results of these interactions vary with the flexibility of the fibre surface. When the fibre is insoluble or junction zones are formed, this may result in profound changes in the surrounding water. Such interactions are capable of affecting the structuring and solvation properties of water well away from the immediate surfaces involved. In particular, the specific properties of water enclosed by dietary fibre are examined, an area of investigation previously receiving scant attention. The way this enclosure may affect the properties of water is exemplified by modeling the colon to show how fibre may exert a beneficial action by the preferential partitioning of hydrophobic carcinogens. Unfermented dietary fibre has a tendency to form low-density expanded water that acts as a preferential solvent for hydrophobic molecules when compared with the less-structured denser water within the much more hydrophilic mucus layer. [Back]

Edwards, S., Chaplin, M. F., Blackwood, A. D. and Dettmar, P. W. (2003) Primary structure of arabinoxylans of ispaghula husk and wheat bran, Proceedings of the Nutrition Society, 62, 217-222. The primary structures of ispaghula husk and wheat bran were investigated in order to determine how and why these fibres are among the most beneficial dietary fibres. To this end, the polysaccharide preparations have been subjected to enzymic hydrolysis and methylation analysis. The results have shown ispaghula husk and wheat bran to be very-highly-branched arabinoxylans consisting of linear β-D-(14)-linked xylopyranose (Xylp) backbones to which α-L-arabinofuranose (Araf) units are attached as side residues via α-(13) and α-(12) linkages. Other substituents identified as present in wheat bran include β-D-glucuronic acid attached via the C(O)-2 position, and arabinose oligomers, consisting of two or more arabinofuranosyl residues linked via 1-2, 1-3, and 1-4 linkages. Ispaghula-husk arabinoxylan is more complex having additional side residues which include α-D-glucuronopyranose (GalAp)-(12)-linked- -L-rhamnopyranose-(14)-β-D-Xylp, α-D-GalAp-(13)-linked-α-L-Araf-(14)-β-D-Xylp, and α-L- Araf-(13)-linked-β-D-Xylp-(14)-β-D-Xylp. The beneficial effects of increased fecal bulk and water-holding capacity are undoubtedly related to the structures of the arabinoxylans, with differences in their efficacy to treat various functional bowel disorders due to their specific structural features. [Back]

Chaplin, M. F., (2001) Water; its importance to life. Biochemistry and Molecular Biology Education, 29 (2), 54-59. Textbooks increasingly include material concerning the importance of water but this topic is often treated over-simplistically with insufficient attention being given to the central position of water in life processes. In this article, modern views of the fundamental role that water plays in biochemical function and process are summarized. The importance of water in the structures of nucleic acids and proteins is explained. [Back]

Chaplin, M. F., (2000) A proposal for the structuring of water. Biophysical Chemistry, 83 (3), 211-221. In spite of much work, many of the properties of water remain puzzling. A fluctuating network of water molecules, with localized icosahedral symmetry, is proposed to exist derived from clusters containing, if complete, 280 fully hydrogen-bonded molecules. These are formed by the regular arrangement of identical units of 14 water molecules that can tessellate locally, by changing centers, in three-dimensions and interconvert between lower and higher density forms. The structure allows explanation of many of the anomalous properties of water including its temperature-density and pressure-viscosity behavior, the radial distribution pattern, the presence of both pentamers and hexamers, the change in properties and `two-state' model on supercooling and the solvation properties of ions, hydrophobic molecules, carbohydrates and macromolecules. The model described here offers a structure on to which large molecules can be mapped in order to offer insights into their interactions. [Back]

Blackwood, A. D., Salter, J, Dettmar, P. W. and Chaplin, M. F., (2000) Dietary fibre, physicochemical properties and their relationship to health. Journal of the Royal Society of Health, 120 (4), 242-247. Dietary carbohydrates that escape digestion and absorption in the small intestine include non-digestible oligosaccharides (carbohydrates with a degree of polymerization between 3 and 10), resistant starch and non-starch polysaccharides. The physiological effects of this heterogeneous mixture of substrates are partly predictable on the basis of their physicochemical properties. Monosaccharide composition and chain conformation influence the rate and extent of fermentation. Water holding capacity affects stool weight and intestinal transit time. Viscous polysaccharides can cause delayed gastric emptying and slower transit through the small bowel, resulting in the reduced rate of nutrient absorption. Polysaccharides with large hydrophobic surface areas have potentially important roles in the binding of bile acids, carcinogens and mutagens. Ispaghula is capable of binding bile acids through a large number of weak binding sites on the polysaccharide structure, and having greatest effect on the potentially more harmful secondary bile acids deoxycholic acid and lithocholic acid. [Back]

Chaplin, M. F., Chaudhury, S., Dettmar, P. W., Sykes, J., Shaw, A. D. and Davies, G. J., (2000) Effect of ispaghula husk on the faecal output of bile acids in healthy volunteers. Journal of Steroid Biochemistry and Molecular Biology, 83 (5), 283-292. Fecal bile acids are associated with both colorectal cancer and serum cholesterol levels. We investigate whether dosing with ispaghula husk affects the fecal bile acid weights and concentrations in healthy adults. Sixteen healthy volunteers consumed 7.0 g/day ispaghula husk, containing 5.88 g/day Englyst-determinable dietary fibre, for the middle 8 weeks of a 12-week period. Stool samples were collected, analyzed for fecal bile acids and their form and dry weight determined. Correlations between the fecal bile acids, the stool parameters and the dietary intake were tested. Ispaghula husk treatment significantly lowers fecal lithocholic and isolithocholic acids and the weighted ratio of lithocholic acids to deoxycholic acid. These effects revert towards their initial states at the end of the treatment period. These changes in the fecal bile acid profiles indicate a reduction in the hydrophobicity of the bile acids in the enterohepatic circulation. [Back]

Manos, G., Dunne, L. J., Chaplin, M. F. and Du, Z., (2001) Comparative study of Monte Carlo simulations and exact statistical mechanical lattice model of commensurate transitions of alkanes adsorbed in zeolites. Chemical Physics Letters, 335, 77-84. A study of commensurate transitions in a lattice model of adsorbed straight chain alkanes (ethane, hexane and heptane) in the zeolite Silicilate is presented, and a comparison made of the calculated isotherms with those from experiments and Monte Carlo simulations. The unusual isotherm shapes predicted by the model are in broad agreement with those from Monte Carlo simulations and experiments; thereby supporting the interpretation of such inflections in isotherms first put forward by Smit and Maeson. [Back]

Du, Z. M., Dunne, L. J., Manos, G. J. N. and Chaplin, M. F., (2000) Exact statistical mechanical treatment of benzene adsorption in a zeolite twin-pore one-dimensional lattice model. Chemical Physics Letters, 318, 319-324. An exact matrix calculation of the statistical mechanics of a lattice model of benzene adsorption in silicalite modeled as two types of quasi one-dimensional pores is presented. The calculation reproduces the experimentally observed two steps in the level of adsorption with rising pressure and also satisfactorily gives the essential features of the loading dependence of the heat of adsorption. [Back]

Blackwood, A. D. and Chaplin, M. F., (2000) Disaccharide, Oligosaccharide and Polysaccharide Analysis. In Encyclopedia of Analytical Chemistry, R. A. Meyers (Ed.) John Wiley & Sons Ltd, Chichester, pp. 741-765. Disaccharides, oligosaccharides and polysaccharides form a very diverse and complex family of biologically important macromolecules. In order to discover their structure it is necessary to determine not only monosaccharides present and their linkage positions and sequence, but also the anomeric configuration of linkages, the ring size (furanose or pyranose), the absolute configuration (D or L) and identify any other substituents present. There is no one method that can be used to determine their fine structure; instead we must use a combination of analytical methods to gain as much information as we can. For analysis of disaccharide and oligosaccharide mixtures, separation and quantification techniques such as colorimetric and enzymatic assays, thin-layer chromatography or high performance anion exchange chromatography may be applied. For polysaccharide analysis separation and extraction techniques, component analysis, methylation analysis, glycosidic hydrolysis, mass spectrometry methods, and nuclear magnetic resonance spectroscopy are required to determine the fine structure and size exclusion chromatography coupled with light scattering detectors to determine the molecular size distribution. [Back]

Poltorak, O. M., Chukhrai, E. S., Kozlenkov, A. A., Chaplin, M. F. and Trevan, M. D., (1999) The putative common mechanism for inactivation of alkaline phosphatase isoenzymes. Journal of Molecular Catalysis B-Enz., 7 (1-4), 157-163. Alkaline phosphatase (E.C. 3.1.3.1) is a family of dimeric metalloenzymes with a complex inactivation mechanism that still remains to be elucidated. We have put forward a novel mechanism of Escherichia coli alkaline phosphatase inactivation, based on experimental as well as structural data for this isoenzyme. It suggests several stages of disruption of the intersubunit contact before the loss of enzyme activity. Here we present initial evidence that the mechanism could also be valid for mammalian isoenzymes. The evidence includes thermal inactivation kinetics and the structural similarity of different alkaline phosphatases inferred from the alignment of their amino acid sequences. The suggested inactivation mechanism of alkaline phosphatases is supported by recent experimental data showing an important role of three intersubunit contact areas in determining the stability of alkaline phosphatase isoenzymes. [Back]

Poltorak, O. M., Chukhray, E. S., Torshin, I. Y., Atyaksheva, L. F., Trevan, M. D., and Chaplin, M. F., (1999) Catalytic properties, stability and the structure of the conformational lock in the alkaline phosphatase from Escherichia coli. Journal of Molecular Catalysis B-Enzmatic, 7 (1-4), 165-172. The activity of oligomeric enzymes is sensitive to the formation and dissociation of the interprotein contacts that make up the conformational lock. The mechanism for this is discussed in this article concerning the alkaline phosphatase (AP) from Escherichia coli. Study of the AP from various source shows that the thermoinactivation curves, obtained under various conditions, have induction periods that may be ascribed to latent structural changes in the conformational lock. The analysis of kinetic curves has allowed us to calculate the minimum number of denaturation stages in the conformational lock (n=3), that is, the stable dimer becomes labile and capable of dissociation by the sequential dissociation of two of the three contacts which take part in the conformational lock. Three-dimensional structural analysis of AP from E. coli established that the structure of intersubunit contact is formed by three sites: two identical peripheral sites, formed by loop 1-29 and helix 29-34 (H 29-34) of each subunit and one, located near to the active centers of two subunits. Destruction of two contacts does not effect the catalytic activity but opening the third results in the dissociation of dimers into monomers and loss of catalytic activity. Thus, kinetic calculation is correlated with the results of structural analysis. Oligomers with decreased activity and increased stability were found in solutions of E. coli AP. The structural possibilities for tetramer formation, based on packing of molecules in protein crystals, are discussed. [Back]

Du, Z. M., Dunne, L. J., Chaplin, M. F. and Manos, G. J. N. (1999) Comparative study of mean-field theory and Monte Carlo simulation of supercritical methane adsorption in zeolites. Chemical Physics Letters, 307 (5-6), 413-418. A comparison of mean-field theory and Monte Carlo simulations, supplemented by molecular modeling, of adsorption of methane in the zeolite silicalite at supercritical conditions is presented. It is found that for the `hot' supercritical temperature regime, adsorption isotherms predicted by mean-field theory are virtually indistinguishable from those of Monte Carlo simulations thereby providing a straightforward route for the prediction of supercritical adsorption isotherms for this system. [Back]

Chaudhury, S. and Chaplin, M. F. (1999) Determination of bile acids in human faecal samples using supercritical fluid extraction and high-performance liquid chromatography, Journal of Chromatography B, 726 (1-2), 71-78. A supercritical fluid extraction (SFE) method for the extraction of bile acids from feces is described. HPLC with pulsed amperometric detection was used to examine and confirm the recovery of bile acids. The analytes were extracted within a period of 75 min using supercritical carbon dioxide at a pressure of 34.5 MPa and a temperature of 90 °C. In developing this method the following parameters were investigated: temperature, pressure, and extraction time. Two alternative methods of sample preparation were also investigated with a view to reducing the overall analysis time. The method was validated for the major primary and secondary bile acids found in feces. It was found that the overall mean±SD recoveries were 102.1±7.92%, 111.6±9.91%, 112.1±9.92% and 113.7±9.92% for dry samples and 108.5±15.77%, 110.0±7.22%, 115.9±11.11% and 106.6±9.16% for wet samples with respect to cholic, deoxycholic, chenodeoxycholic and lithocholic acid. The SFE is an alternative to the traditional methods available. The extraction is relatively easy to conduct and does not utilize as much glassware, solvents or time. [Back]

Chaplin, M. F. (1999) Structure-activity relationships in complex carbohydrates. In; The right fibre for the right disease, Ed. M. Hill. International Congress Symposium Series. 256, Royal Society of Medicine Press, 11-16. The structural characteristics of dietary carbohydrates affect fermentation and intestinal transit time. The availability of carbohydrates for digestion and gel formation is also dependent on their interaction with water. The water-holding capacity of complex carbohydrates has an effect on their viscosity and bile acid binding properties. Water appears to be the most important entity in determining the properties of fibre; the fibre directs the action of the water and the water directs the action of other factors. [Back]

Foster, L. H., Chaplin, M. F. and Sumar, S. (1998) The effect of heat treatment on intrinsic and fortified selenium levels in cow's milk. Food Chemistry, 62 (1), 21-25. The effects of two heat processing methods (pasteurization and spray drying) routinely used in the processing of cow's milk and the production of infant formula powder on the selenium (Se) content of liquid milk, milk fortified with sodium selenite and sodium selenate were studied. Pasteurization reduced intrinsic Se and selenate levels by 7.9% and 6.2% at p < 0.05 level and selenite levels by 7.0% at p > 0.05 level. Se losses following spray drying were 44.8% (p < 0.001), 11.4% (p < 0.01) and 10.0% (p < 0.01) for intrinsic selenium, selenite and selenate fortified milk, respectively. Total Se losses from unprocessed milk following processing (pasteurization and spray drying) were 49.2% (p < 0.001), 17.6% (p < 0.001) and 15.6% (p < 0.001) for intrinsic selenium, selenite and selenate fortified milk, respectively. [Back]

Chaplin, M. F., (1998) Bile acids, fibre and colon cancer: the story unfolds.Journal of the Royal Society of Health, 118 (1), 53-61. Are the changes in fecal bile acid concentrations the cause of colorectal cancer or one of its effects? This is an area of controversy mainly due to the lack of a clear explanation as to how the bile acid concentrations are controlled under different circumstances. This review presents an outline of the evidence that bile acids are both a causal factor in colorectal cancer and that their concentrations are affected by it in a synergistic manner. It also offers an explanation of how some dietary fibre protects against colorectal cancer. [Back]