Article

Building bridges between the physical and biological sciences

Research School of Physical Sciences and Engineering, Australian National University, 0200 Canberra, Australia.
Cellular and molecular biology (Noisy-le-Grand, France) (Impact Factor: 1.23). 01/2006; 51(8):803-13. DOI: 10.1170/T689
Source: PubMed

ABSTRACT

This paper attempts to identify major conceptual issues that have inhibited the application of physical chemistry to problems in the biological sciences. We will trace out where theories went wrong, how to repair the present foundations, and discuss current progress toward building a better dialogue.

Download full-text

Full-text

Available from: Barry W Ninham
  • Source
    • "While we have presented only two phenomena (protein precipitation and enzyme activity) directly affected by ions, the concerns raised in this paper are applicable to all ion-specific questions previously examined using saltbased experimentation. Ninham and Boström [5] state " . . . physical chemistry and colloid and surface science today sit in splendid disjunction from modern cell and molecular biology " and express frustration regarding the " ancillary and irrelevant " role played by the physical sciences in the life sciences. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Ion-specific effects underlie a vast array of physicochemical and biological phenomena ranging from human physiology to biotechnology to ecology. These effects have traditionally been quantified by measuring the response of interest in a series of salt solutions at multiple concentrations; pH has consistently been shown to be of primary concern. However, salt-based approaches violate critical tenets of proper experimental design and introduce confounding errors that make it impossible to quantify ion-specific effects. For example, pH is a variable dependent on the type and concentration of ions in a solution, but is typically treated as an independent factor, thus confounding experiments designed to determine ion-specific effects. We examined the relevancy of ion-specific effects research in relation to these concepts and demonstrated how these ideas impact protein precipitation and enzyme activity. Based on these results, we present a conceptual and experimental framework of general applicability for proper quantification of ion-specific effects.
    Full-text · Article · May 2008 · Scholarly Research Exchange
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chemical processes at the interfaces often differ kinetically and mechanistically from the bulk counterparts, partly due to the concentration inhomogeneity of different chemicals at the interfaces. The fractionation of chemicals at the interfaces not only determines their interfacial concentrations, but also affects the physicochemical properties of the interfaces. In this thesis, three sets of chemicals/interfaces with important environmental implications are studied: (1) anion fractionation at the gas–liquid microdroplet interfaces, (2) fractionation of perfluoroalkyl surfactants and matrix components at the bubble–water interface in ultrasonically irradiated solutions, and (3) ion fractionation across the ice–water interface during the freeze–thaw cycle of electrolyte solutions. The relative anion affinity for the air–water interface, as measured by Electrospray Mass Spectrometry (ES–MS), is exponentially correlated with ionic radius. The affinities respond differently to different additives, suggesting that specific anion effects are due to different energy levels of physical interactions. Relative anion affinities at the air–methanol interfaces are almost identical to those at the air–water interface, suggesting that surface structure is not the primary driving force for interfacial anion fractionation. Perfluoroalkyl carboxylates and sulfonates can be transferred from the ocean to marine aerosols due to their high affinity for the air–water interface, but transfer to gas phase is unlikely as they remain deprotonated in aqueous phase because of their low pKa. Organic matrix components may reduce the sonochemical kinetics of Perfluorooctanesulfonate (PFOS) and Perfluorooctanoate (PFOA) by competitive adsorption onto the bubble–water interface or by lowering the interfacial temperatures. Inorganic anions, but not cations, may significantly enhance or reduce the sonochemical kinetics of PFOS and PFOA. The specific anion effects following the Hofmeister series are likely related to anions’ partitioning to and interaction with the bubble–water interface. Time–resolved confocal fluorescence microscopy of freezing electrolyte solutions reveals that the thickness of interstitial liquid films depends non–monotonically on electrolyte concentration. It also confirms that selective incorporation of cations (anions) into the ice lattice decreases (increases) the pH of the interstitial liquid films. Since the magnitude of pH change during freezing is smaller than during the subsequent thawing process, it is likely to be limited by the seepage of proton or hydroxide slowly produced via water dissociation.
    Preview · Article ·
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The biologically significant state of membranes is the fluid crystalline state. As most liquid crystal compounds, lipid membranes display a rich polymorphism. However, only few phases are biologically relevant. In this review, I give an overview of all lipid mesophases which play a role in nature and illustrate how X-ray-scattering techniques contribute to the determination of their structural as well as mechanical properties. This includes to know about lipid/water composition, monolayer thickness, interfacial area per lipid, molecular shape, membrane curvatures, and bending rigidity. Under excess water condition – as biological membranes are – only four types of stable mesophases exist, i.e., the lamellar fluid phase Lα, the bicontinuous cubic phases, the columnar inverted hexagonal phase HII, and further one micellar cubic phase. Besides these, I give a brief description of the so-called “mesh” phase, which has been recently suggested to be host for the membrane fusion stalk intermediate.
    Full-text · Article · Jan 2006 · Advances in Planar Lipid Bilayers and Liposomes
Show more