A Proposal for a Force Essential to Biological Organization

A PROPOSAL FOR A FORCE ESSENTIAL TO BIOLOGICAL ORGANIZATION A. S. IBERALL* A recent monograph on the kinetics of the liquid state as applied to transport [1] and an application of that monograph to hydrodynamic and diffuse flow in small channels (down to 15 Â) [2] have led my colleagues and me to some new ideas on the nature ofthe forces organizing the living state. In this highly speculative note, we would like to outline our view of the total reach of these ideas. While the outline may be wrong in some of its details, we believe the theme rich enough to deserve a hearing. Thesis 1.—There are three simple well-known states of matter and a number of complex correlated states. The three simple states are the gaseous, liquid, and solid states. The complex states may be the vitreous, the living, the geochemical, and the plastic-elastic state. We wish to focus on the living state, which we believe to be a complex liquid-plastic state. Thesis 2.—Within a current outlook, interaction in physics is limited to not more than four basic forces: the gravitational, electromagnetic, strong nuclear, and weak. Of these, possibly only two, the gravitational and electromagnetic, may be fundamental. A fundamental question of concern to the origin and character of life is whether these forces are sufficient to account for life and its self-organizing capability or whether new themes must be developed to deal with that state. We opt for the beliefthat life processes can be described by the known forces of physics and propose now to give that belief particular form. Thesis 3.—Both the deviations from the ideal gas state (that is, descriptions that are immediately true for all real gases) and the transport properties of fluids are intimately tied up with the nature and spatial range of intermolecular forces. The forces are fairly well known (electrostatic and quantum mechanical exchange), being repulsive at a few tenths to 1 Â and attractive at levels greater than 1 Â. Nuclear forces, not interactive with intermolecular chemical forces, are expressed as ?General Technical Services, Inc., Upper Darby, Pennsylvania 19082. While this effort is the continued inertia) reaction to earlier ONR, NASA, and U.S. Army studies, I acknowledge fiscal support from no agency of government or industry, only to those friends whose intellectual support and interest make this continued effort worthwhile. For in science, we are a community. Perspectives in Biology and Medicine · Spring 1975 | 399 form—they keep electrons and nuclei organized as discrete, slightly deformable bodies. Chemically, these intermolecular forces relate to ionic and valence force bindings. They have the competence to organize structures as complex as organic biochemical molecules, for example, proteins and polynucleotides. But physically, what are the forces that lead to biological organization? Can one travel the chain that bridges nonideal gas laws of state, to transport coefficients, to dynamic chemical moieties, to biological system dynamics? Thesis 4.—Flow processes in liquids must be developed on an enriched kinetic base beyond gas kinetic theory [I]. We have proposed such a basis for processes of the order of a few atomic diameters (not one, but perhaps three diameters). Because of high-bulk modulus (low compressibility , e.g., [dp/d In u]r= 15,000 atm), a molecule in the liquid phase is surrounded by a cage of about 20 neighbors. The escape of a molecule from that cage is somewhat more difficult than has heretofore been depicted. Loosely speaking, fluctuational interaction with all of its neighbors has to occur before an "escape" exchange can take place. But conversely, when that exchange does take place (i.e., as a Stokes-Einstein diffusional step), the ensemble process is near equilibrium. Thus, spacewise, a 3x3x3 molecular array is near enough to thermodynamic equilibrium to be describable as a continuum hydrodynamic field. Timewise, near-equilibrium equations of state and of change will hold for macroscopic processes longer than these 20-odd fluctuations. Thesis 5.—But there is a dilemma in describing flow boundary conditions at solid walls. It is already encountered in gas flow. In gases, Knudsen proved that boundary conditions required "slip" at the wall in a flow field rather than a vanishing relative velocity...