PubMed · 5589915
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J Schormüller. 1967-08-12. [Cold biochemistry].. https://pubmed.ncbi.nlm.nih.gov/5589915/
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We study a general class of nonlinear macroscopic evolution equations with "transport" and "reaction" terms which describe the dynamics of a species of moving individuals (atoms, molecules, quasiparticles, organisms, etc.). We consider that two types of individuals exist, "not marked" and "marked," respectively. We assume that the concentrations of both types of individuals are measurable and that they obey a neutrality condition, that is, the kinetic and transport properties of the "not marked" and "marked" individuals are identical. We suggest a response experiment, which consists in varying the fraction of "marked" individuals with the preservation of total fluxes, and show that the response of the system can be represented by a linear superposition law even though the underlying dynamics of the system is in general highly nonlinear. The linear response law is valid even for large perturbations and is not the result of a linearization procedure but rather a necessary consequence of the neutrality condition. First, we apply the response theorem to chemical kinetics, where the "marked species" is a molecule labeled with a radioactive isotope and there is no kinetic isotope effect. The susceptibility function of the response law can be related to the reaction mechanism of the process. Secondly we study the geographical distribution of the nonrecurrent, nonreversible neutral mutations of the nonrecombining portion of the Y chromosome from human populations and show that the fraction of mutants at a given point in space and time obeys a linear response law of the type introduced in this paper. The theory may be used for evaluating the geographic position and the moment in time where and when a mutation originated.
The Human Genome Project, DNA microarrays, proteome chips and metabolic profiles, among others, are generating unprecedented amounts of valuable information about the genetic and metabolic responses of organisms to stimuli. This wealth of information poses a great scientific challenge, namely the development of novel, effective methods for functional analysis and interpretation. It is proposed here that biomathematical systems models must accompany data generation and management. A particularly effective framework for this purpose is canonical modeling based on Biochemical Systems Theory. The key concept of this theory is the formulation of biological phenomena as systems of differential equations, in which all processes are represented as products of power-law functions.
Biomineralization of the ferritin iron core involves a complex series of events in which H(2)O(2) is produced during iron oxidation by O(2) at a dinuclear centre, the 'ferroxidase site', located on the H-subunit of mammalian proteins. Rapid-freeze quench Mössbauer spectroscopy was used to probe the early events of iron oxidation and mineralization in recombinant human ferritin containing 24 H-subunits. The spectra reveal that a mu-1,2-peroxodiFe(III) intermediate (species P) with Mössbauer parameters delta (isomer shift)=0.58 mm/s and DeltaE(Q) (quadrupole splitting)=1.07 mm/s at 4.2 K is formed within 50 ms of mixing Fe(II) with the apoprotein. This intermediate accounts for almost all of the iron in the sample at 160 ms. It subsequently decays within 10 s to form a mu-oxodiFe(III)-protein complex (species D), which partially vacates the ferroxidase sites of the protein to generate Fe(III) clusters (species C) at a reaction time of 10 min. The intermediate peroxodiFe(III) complex does not decay under O(2)-limiting conditions, an observation suggesting inhibition of decay by unreacted Fe(II), or a possible role for O(2) in ferritin biomineralization in addition to that of direct oxidation of iron(II).