Self-amplifying

Kauffman also considers that autocatalytic reactions are a necessary precondition for biogenesis processes, as they can wind themselves up via self-amplifying feedback processes until a critical boundary has been reached. The next step would then be the transition from autocatalysis to self-organisation, similar to the transition from unstructured water to convection cells (the Benard instability) (Davies, 2000). 

Kim TH, Swager TM (2003) A fluorescent self-amplifying wavelength-responsive sensory polymer for fluoride ions. Angew Chem Int Ed 42 4803 1806... 

In cells that use Ca + as second messenger, binding of an external signal to a cell membrane receptor activates phospholipase C (PLC), which, in turn, synthesizes inositol 1,4,5-trisphosphate (InsP3). This metabolite binds to an InsP3 receptor located on the membrane of internal Ca + stores (endoplasmic or sarcoplasmic reticulum) and thereby triggers the release of Ca " " into the cytoplasm of the cell [56]. A conspicuous feature of Ca release is that it is self-amplified Cytosohc Ca + triggers the release of Ca " " from intracellular stores into the cytosol, a process known as Ca +-induced Ca " " release (CICR) [57, 58]. 

Swager TM (2002) Chem Res Toxicol 15 125 Ultrasensitive sensors from self-amplifying electronic polymers... 

This example clearly demonstrates that it is possible to self-amplify one product in a DCL, namely the one that can self-complementarily direct its own formation. It was shown that the expression of the components in the library evolves along both kinetic and thermodynamic biases that both lead to the amplification of the best duplicator. Importantly, because of the double reversibility of the system (supra-molecular H-bonds and molecular imine condensation), the competition is ruled not only by the differential rates of formation of the components, but also by the possible takeover of the building blocks of the antagonistic competitors, thus leading to the decrease of their absolute concentration. Such a system illustrates the spontaneous screening and selection of the most efficient self-duplicator by the destruction of the entities which are not (or less, such as Al, Am2) able to duplicate themselves. 

The phenomenon of unstable combustion results from a self-amplifying interaction between combustion processes and the. acoustic oscillations of the gas within the rocket motor. The unexpected appearance of combustion instability in any rocket generally terminates its mission thru motor case rupture from overpressure, disruption of guidance systems by severe vibration, or thrust malalignment. Both axial mode and transverse mode instabilities are observed (Ref 45). In the case of the transverse mode the characteristic wave time is usually that required to travel radially around the proplnt cavity whereas the characteristic time for the axial mode is the time for the wave to travel from end to end in the combustion chamber. Double-base proplnts predominantly are prone to transverse wave instabilities and infrequently to those in the axial mode, while composite proplnts appear to go unstable mostly in the axial mode. In the case of transverse instability chamber pressures have been known o double whereas in axial mode instabilities artificially induced by pulsing the chamber pressure at lOOOpsi, the pressure excursion may reach 300—400psi. A review of recent theoretical combustion modeling for combustion instability has been made by Price (Ref 47)... 

The activity of one enzyme was affected by its own reaction products and by substrates and products of the other enzyme. These authors concluded that the mutual lipid-mediated interfaclal modulation between both phosphohydrolytic pathways indicated that phospholipid degradation might be self-amplified or dampened depending on subtle changes of surface pressure and composition. 

The harmonics are particularly attractive in terms of the radiation peak power. Thus, it should open the way for non-linear laser spectroscopy in the short-wavelength (10 nm) regime. A competing technology requiring much larger installations is Self Amplified Spontaneous Emission used for Free-Electron-Laser action (SASE-raL) [25,26]. 

The model based on oscillatory isozymes, which can be extended to a larger number of oscillatory units coupled in parallel, is closer to the neuronal situation than the model of fig. 3.1. Indeed, the situation of two isozymes activated by their common product is somewhat analogous to that of two ion channels carrying the same ionic species and activated in a self-amplified manner by the membrane potential. 

An important feature of the signalling system, suggested by the observations of Roos et al. (1975) and Shaffer (1975), is that the stimulation by extracellular cAMP enhances the synthesis of intracellular cAMP. This activation of adenylate cyclase, the enzyme catalysing the production of cAMP from ATP, follows the binding of extracellular cAMP to a specific receptor located on the outer face of the cell membrane (Roos Gerisch, 1976). Synthesis of cAMP in D. discoideum therefore is a self-amplifying process (fig. 5.15) the more cAMP accu-... 

The existence of the abrupt threshold for the relay response is linked to the excitable properties of the cAMP-synthesizing system. Like the oscillations, excitability is due mainly to the self-amplifying nature of cAMP production in the slime mould. As indicated by the curve yielding the saturation function of the receptor as a function of the cAMP signal in fig. 5.32, no threshold is detectable for binding of the ligand to... 

Trisporic acids are formed from -carotene (1) via retinal (20) with further loss of two carbon atoms. As these compounds induce additional carotenoid biosynthesis, biosynthesis of these compounds is self-amplifying. Yields of trisporic acids in mixed cultures (+ and —) are typically 200-1000 fxg/ml. 

---