Bruce H. Weber

Evolution in thermodynamic perspective: An ecological approach

Recognition that biological systems are stabilized far from equilibrium by self-organizing, informed, autocatalytic cycles and structures that dissipate unusable energy and matter has led to recent attempts to reformulate evolutionary theory. We hold that such insights are consistent with the broad development of the Darwinian Tradition and with the concept of natural selection. Biological systems are selected that re not only more efficient than competitors but also enhance the integrity of the web of energetic relations in which they are embedded. But the expansion of the informational phase space, upon which selection acts, is also guaranteed by the properties of open informational-energetic systems. This provides a directionality and irreversibility to evolutionary processes that are not reflected in current theory.For this thermodynamically-based program to progress, we believe that biological information should not be treated in isolation from energy flows, and that the ecological perspective must be given descriptive and explanatory primacy. Levels of the ecological hierarchy are relational parts of ecological systems in which there are stable, informed patterns of energy flow and entropic dissipation. Isomorphies between developmental patterns and ecological succession are revealing because they suggest that much of the encoded metabolic information in biological systems is internalized ecological information. The geneological hierarchy, to the extent that its information content reflects internalized ecological information, can therefore be redescribed as an ecological hierarchy.This thermodynamic approach to evolution frees evolutionary theory from dependence on a crypto-Newtonian language more appropriate to closed equilibrial systems than to biological systems. It grounds biology non-reductively in physical law, and drives a conceptual wedge between functions of artifacts and functions of natural systems. This countenances legitimate use of teleology grounded in natural, teleomatic laws.

Hazards in the use of Cibacron Blue F3GA in studies of proteins.

Abstract Cibacron Blue F3GA from several commercial sources is shown to be heterogeneous. This crude dye inactivates both phosphoglycerate kinase and isoleucyl-tRNA synthetase. Purification of Cibacron Blue F3GA to homogeneity results in a dramatic decrease in inactivation of these enzymes. The inactivation is shown to be due to covalent modification of phosphoglycerate kinase and probably isoleucyl-tRNA synthetase by a minor component present in crude Cibacron Blue F3GA.

Natural selection and self-organization

The Darwinian concept of natural selection was conceived within a set of Newtonian background assumptions about systems dynamics. Mendelian genetics at first did not sit well with the gradualist assumptions of the Darwinian theory. Eventually, however, Mendelism and Darwinism were fused by reformulating natural selection in statistical terms. This reflected a shift to a more probabilistic set of background assumptions based upon Boltzmannian systems dynamics. Recent developments in molecular genetics and paleontology have put pressure on Darwinism once again. Current work on self-organizing systems may provide a stimulus not only for increased problem solving within the Darwinian tradition, especially with respect to origins of life, developmental genetics, phylogenetic pattern, and energy-flow ecology, but for deeper understanding of the very phenomenon of natural selection itself. Since self-organizational phenomena depend deeply on stochastic processes, self-organizational systems dynamics advance the probability revolution. In our view, natural selection is an emergent phenomenon of physical and chemical selection. These developments suggest that natural selection may be grounded in physical law more deeply than is allowed by advocates of the autonomy of biology, while still making it possible to deny, with autonomists, that evolutionary explanations can be modeled in terms of a deductive relationship between laws and cases. We explore the relationship between, chance, self-organization, and selection as sources of order in biological systems in order to make these points.

On the validity of Shannon-information calculations for molecular biological sequences*

The usefulness of information-theoretic measures of the Shannon-Weaver type, when applied to molecular biological systems such as DNA or protein sequences, has been critically evaluated. It is shown that entropy can be re-expressed in dimensionless terms, thereby making it commensurate with information. Further, we have identified processes in which entropy S and information H change in opposite directions. These processes of opposing signs for delta S and delta H demonstrate that while the Second Law of Thermodynamics mandates that entropy always increases, it places no such restrictions on changes in information. Additionally, we have developed equations permitting information calculations, incorporating conditional occurrence probabilities, on DNA and protein sequences. When the results of such calculations are compared for sequences of various general types, there are no informational content patterns. We conclude that information-theoretic calculations of the present level of sophistication do not provide any useful insights into molecular biological sequences.

Emergence of Life and Biological Selection from the Perspective of Complex Systems Dynamics

All cultures, including the scientific, have creation stories. These reflect the knowledge and values of the tellers of such narratives. Until relatively recently, most such scenarios posited a divine creator or engineer-like god responsible for the creation of the cosmos and the origin of life.

Glynn and the Conceptual Development of the Chemiosmotic Theory: A Retrospective and Prospective View

The origin and evolution of the chemiosmotic theory is described particularly in relation to Peter Mitchells application of it to model oxidative phosphorylation. Much of the deployment, development and evaluation of the theory occurred at the independent laboratory of the Glynn Research Foundation; the value and future of such an institution is discussed. The role of models mediating between theories and phenomena is analyzed with regard to the growth of knowledge of chemiosmotic systems.

Closure in the Emergence and Evolution of Life: Multiple Discourses or One?

Abstract: Evolutionary theory formulated in terms of complex systems dynamics shows interesting convergences with the approaches of developmental systems theory and biosemiotics, especially when applied to the problem of the origin of life. Although starting from difference conceptual assumptions, all three approaches agree on the importance of closure in the form of semi‐permeable chemical and informational boundaries and a more circumscribed role for DNA.

What is Life? Defining Life in the Context of Emergent Complexity

Erwin Schrödinger defined life not only as a “self-reproducing” aperiodic crystal of DNA coding for proteins but within the context of living entities increasing their order by dissipating matter/energy gradients to maintain themselves away from equilibirium. Since then most definitions of life have focused on the former. But living cells do more than replicate their DNA. Cells also have membrane barriers across which metabolites must move, via which energy transduction as well as information processing occurs, and within which metabolic transformation occurs. An approach of complex systems dynamics, including nonequilibrium thermodynamics, may provide a more robust approach for defining life than a “naked replicator” at the origin of life. The crucial issue becomes the process of emergence of life from pre-biotic chemistry, concomitant with the emergence of function, information, and semiosis. Living entities can be viewed as bounded, informed autocatalytic cycles feeding off matter/energy gradients, exhibiting agency, capable of growth, reproduction, and evolution. Understanding how life might have emerged should sharpen our definition of what life is.

On the Emergence of Living Systems

If the problem of the origin of life is conceptualized as a process of emergence of biochemistry from proto-biochemistry, which in turn emerged from the organic chemistry and geochemistry of primitive earth, then the resources of the new sciences of complex systems dynamics can provide a more robust conceptual framework within which to explore the possible pathways of chemical complexification leading to living systems and biosemiosis. In such a view the emergence of life, and concomitantly of natural selection and biosemiosis, is the result of deep natural laws (the outlines of which we are only beginning to perceive) and reflects a degree of holism in those systems that led to life. Further, such an approach may lead to the development of a more general theory of biology and of natural organization, one informed by semiotic concepts.

Evidence for an essential role for arginyl residues for yeast phosphoglycerate kinase.

Abstract Reaction of yeast phosphoglycerate kinase with either butanedione or cyclohexanedione can result in modification of up to all 13 arginyl residues with total loss of activity; however, extrapolation to zero activity for partially modified preparations indicates that up to 7 arginyls are essential. Whereas 20 m m 3-phosphoglycerate affords partial protection of activity toward both reagents, 20 m m MgATP affords complete protection of activity and protects 2 arginyls against modification by butanedione and 1 arginyl against modification by cyclohexanedione. With butanedione the modification could be reversed with total recovery of activity, suggesting that only arginyl groups were modified, which is consistent with the amino acid analysis of the modified protein. Only at high cyclohexanedione concentrations or long reaction times was a yellow product obtained that showed loss of lysyl residues. Circular dichroism spectra show that even when all the arginyls are modified by butanedione or up to 10 modified by cyclohexanedione there is no change observed in the far or near ultraviolet, indicating that there is no detectable conformational change concomitant with modification, which is confirmed by hydrodynamic studies. It is concluded that at least one, possibly two, arginyls of yeast phosphoglycerate kinase are essential for its action on ATP.