Bacterial bioluminescence-identification of fatty acid as product, its quantum yield and a suggested mechanism

By using radioactive decanal the direct transformation of this aldehyde to decanoic acid, with a quantum yield of 0.13, has been demonstrated. A mechanism analogous to that of other better understood bioluminescent reactions is proposed, leading to a product, as yet unisolated from the enzymic reaction, whose fluorescence spectrum is an excellent match for that of the $\text{in vivo}$ luminescence.The extensive examination^1,2,3 of the isolated bacterial luminescence system has resulted in the accepted outline shown. We wish to modify it, in accordance with the previous evidence, by suggesting that ’intermediates I and II‘ in Hastings' terminology² are the same enzyme bound FMNH₂ moiety.

$\text{FMN}{}_2\text{enzyme}\text{?}\text{enzyme FMNH}{}_2$

$\text{enzyme FMNH}{}_2\text{RCHO}\text{?}\text{covalent complex}$

$\text{covalent complex O}{}_2\text{→}\text{P}{}^1\text{RCO}{}_2\text{H}$

A lively controversy has surrounded the attempts to determine whether aldehyde exerts a purely catalytic role² or is transformed in the reaction.⁴ If the aldehyde reacts, then the simplest product is the corresponding carboxylic acid, perhaps formed via the peracid. The most likely alternative reaction would involve enolistation and oxidation at the α-methylene group. We examined the second alternative fairly carefully, and found no evidence for it. We do not wish to report these results in detail at present, since we have now established that the acid corresponding to that formed in a normal autoxidation of the aldehyde is the product. Some indication of the nature of the products of the reaction is available.⁵Since the amount of product in the reaction is restricted to a very low level by the concentrations required, we labelled decanal with tritium at C-2 and thus were able to record the yield with some precision. Although recent work⁶ strongly implies that acid is formed stoichiometrically, the direct measurement of the quantum yield with respect to acid formation is necessary before a mechanism can be written. We have suggested a mechanism compatible with observations in this system, analogous to all cases of bioluminescence for which a mechanism is reasonably well established. This mechanism also leads to a product excited state with excellent agreement around pH7 in fluorescence wavelength to that of the $\text{in vivo}$ luminescence.     

Homogeneous enzyme immunoassay of chenodeoxycholate conjugates in serum.

It is shown that biased answers are given by the mathematical method used by Stein and his colleagues (Hankin B. L. Hankin, W. R. Lieb, and W. D. Stein (1972)Biochim. Biophys. Acta288, 114–126) to calculate $\text{K}{}_{21}{}^{\mathrm{<mtext>ic</mtext>}}$, the half-saturation concentration for the entry of glucose into erythrocytes in infinite-cis conditions. A method for calculating $\text{K}{}_{21}{}^{\mathrm{<mtext>ic</mtext>}}$ accurately is described and tested. The published estimates of $\text{K}{}_{21}{}^{\mathrm{<mtext>ic</mtext>}}$ are low; nevertheless, even when they are revised upwards, the asymmetrical carrier model of glucose transport still fails to satisfy the “rejection criteria” of Hankin et al. (1972).     

A stable traveling-wave solution of a model of cellular control processes with positive feedback

Edelstein's model

$\text{?E}\text{?τ}\text{=F(M, E)}$

,

$\text{?M}\text{?τ}\text{=G(M, E)+D}\text{?}{}^2\text{M}\text{?s}{}^2$

,

$\text{M(s,0)=?(s)}$

,

$\text{E(s,0)=ψ(s)}$

, where τ ? 0 and ?∞<s<∞, $\text{F(M, E>) = (K}{}_1\text{+M}{}^{\mathrm{m}}\text{)}\text{(K}{}_2\text{+M}{}^{\mathrm{m}}\text{)?k}{}_1\text{E, G(M, E)}\text{= k}{}_1\text{E ? k}{}_2\text{M,}$ m ? 2, describes the behavior of two basic chemical species during the cellular differentiation in a linear ensemble of the same cell type. We prove the existence and uniqueness of a travelling-wavefront solution. We also demonstrate one kind of stability for this solution.