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Most well-known oscillatory chemical reactions (B-Z-reactions) are of limited relevance to biochemistry because the reagents used and the reaction conditions are not characteristic for living systems. We have found that well expressed and sustained oscillatory behavior of chemiluminescence (CL) can be observed in solutions of the most common bio-molecules under rather mild conditions.

Aqueous alkaline solutions of D-glucose (Glc) or D-ribose(Rib) were heated to 92 C for 5 min, rapidly cooled and supplemented with the equal volumes of cold aqueous alkaline solutions of glycin (Gly). In some cases either copper (II), or iron salts ((II/III)), or ascorbic acid were added to the reaction mixtures. CL in non-stirred mixtures was registered using single photon counters at room temperature with high temporal resolution and for extended periods of time.

It is well known that in aqueous alkaline solutions of amino acids and activated reducing sugars the so called Maillard reaction takes place. It starts with Schiff base formation and then a number of low- and high molecular weight metastable products emerge. Among them colored, fluorescent compounds are present. Some of the products can reduce oxygen by two-electron or one-electron reactions. The first path leads to dioxethans, and the second - to free radical generation. CL is thought to arise from the relaxation of electron excited products of the reactions of these active oxygen spesies. In fact we have shown that concomitantly to the elevation of CL intensity concentration of H₂O₂ was increasing up to stationary levels of dozens of micromoles. If additional H₂O₂was added to the solution it was consumed until the preceding stationary level was attained. These data argue in favor of self-regulation of ROS levels in the reaction process studied here.

Oscillations of CL in Rib/Gly mixtures were observed very early after the reaction mixture preparation. With the reaction development the gradual elevation of their amplitude that eventually reached 20-30% of the mean was observed. Approximately 24 hr after the initiation of the reaction oscillations suddenly ended off and CL intensity started gradually to decrease. Most prominent oscillation periods were about 20-40 min, and higher frequency oscillations had much lower spectral densities. Comparison of oscillation patterns in the samples prepared identically but on different days revealed a great similarity in the «images» of oscillations in them, especially in the period preceding oscillations end off. The frequency parameters of oscillations in such samples could be significantly different (Fig. 1).

In Glc/Gly solutions oscillations of CL unlike Rib/Gly solutions were observed only when copper ( 0,1 mkM) or iron ( 10 mkM) salts, or ascorbic acid ( 10 mkM) were added to the reaction mixtures; in the presence of much higher GLC than Rib concentrations, and they disappeared much earlier than in Rib/Gly solutions. At the concentration of 1 mM ascorbic acid inhibited CL intensity growth for about 5 hr, though later it started to elevate very rapidly and in a highly pronounced oscillatory manner (Fig. 2).

Figure 1

Figure 2

These data allow to suggest that 1) a chain reaction with delayed branching is developing in aqueous solutions of activated reducing monosaccarides and glycin in which reactive oxygen species play a key role; 2) substances capable to cyclic one-electron oxidation-reduction (transition metals, ascorbate) induce self-organization in this reaction system 3) self-organization emerging in a solution of common bio-molecules is exposed as a complex temporarily structured non-linear dynamic process and it is provided by a continuous electron excited states generation.
 

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