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Minimal artificial cells (MACs) are self-assembled chemical systems able to mimic the behavior of living cells at a minimal level, i.e. to exhibit self-maintenance, self-reproduction and the capability of evolution. The bottom-up approach to the construction of MACs is mainly based on the encapsulation of chemical reacting systems inside lipid vesicles, i.e. chemical systems enclosed (compartmentalized) by a double-layered lipid membrane. Several researchers are currently interested in synthesizing such simple cellular models for biotechnological purposes or for investigating origin of life scenarios. Within this context, the properties of lipid vesicles (e.g., their stability, permeability, growth dynamics, potential to host reactions or undergo division processes…) play a central role, in combination with the dynamics of the encapsulated chemical or biochemical networks. Thus, from a theoretical standpoint, it is very important to develop kinetic equations in order to explore first-and specify later-the conditions that allow the robust implementation of these complex chemically reacting systems, as well as their controlled reproduction. Due to being compartmentalized in small volumes, the population of reacting molecules can be very low in terms of the number of molecules and therefore their behavior becomes highly affected by stochastic effects both in the time course of reactions and in occupancy distribution among the vesicle population. In this short review we report our mathematical approaches to model artificial cell systems in this complex scenario by giving a summary of three recent simulations studies on the topic of primitive cell (protocell) systems. OPEN ACCESSEntropy 2014, 16 2489

Abstract1H-, 13C -NMR , IR, UV-Vis, and MS spectra of p-hydroxyphenylpyruvic acid (pH PPA) have been recorded and fully interpreted.pHPPA exists in solution as a mixture of interconverting forms: keto, hydrated keto and only one enol tautomer to which the Z configuration has been assigned according to the value (3.7 Hz) of the vicinal IH-C = C-13COOH coupling constant.In organic solvents the enol isomer is far more stable whereas in aqueous solutions the keto form predominates. The tautomeric equilibrium is pH-dependent and the anion is present as keto form not only in aqueous solution but also in H2O-DMSO mixtures with a high content of DMSO.The Z enol tautomer does form a coloured complex (λmax = 680 nm) with Fe+3 ions. The complex decomposes rapidly in all considered solvents except DMSO.In view of a possible use of H2O-DMSO mixtures for clinical analysis purpose, the enol fraction of pHPPA and the stability of the pH PPA -FeCl3 com plex in H2O-DMSÒ mixtures have been examined. Our results suggest that a solvent com position containing at least 80 vol.% in DM SO could be an appropriate solvent for pH PPA determination by FeCl3 method.

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We sought a thiocarbonyl reagent that could be introduced by simple acylation. A second consideration was that the intermediate radical species resulting from attack of tin at thione sulfur would not be stabilized at the a-carbon. Such a stabilization could allow abstraction of hydrogen from the trialkylstannane to compete effectively with alkyl carbon-oxygen bond homolysis. Dethiation (thiobenzoyl esterbenzyl ether) and collapse (dithiocarbonate esteralcohol starting material) byproducts have been observed by using the a-benzylic-and a-thiol-stabilized ~p e c i e s .~~*~~~ Treatment of thiophosgene with phenol gave phenyl chloro-thionocarb~nate.'~ Pyridine effectively catalyzed reactions of this thioacyl chloride with relatively unhindered alcohols, but 4-(dimethy1amino)pyridine was requiredl6 for smooth conversion of nucleosides to their 2'-O-phenoxythiocarbonyl derivatives.Reductive cleavage of these compounds occurred readily when tri-n-butylstannane in toluene at 75 OC with a,a'-azobisisobutyronitrile as initiator was used.17 No dethiation or alcohol byproducts were detected in cases we have examined. As seen in Table I, thioacylation (generally quantitative) and reductive cleavage (proceeds to completion in 3 h) give good overall yields of deoxygenation of isolated secondary alcohols (entries 4, 5 ) . An epoxide function is tolerated (entry 5b).Selective 3' and 5' protection was required for specific 2'deoxygenation of ribonucleosides. Multistep procedures have been required previously,' but a hindered bifunctional disiloxane reagent became available recently.18 Treatment of ribofuranosyl compounds (1) with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane in pyridine gave the cyclic 3',5'-trioxadisila derivatives (2, R = H) in over 90% yields (Scheme I). Thioacylation of 2 (R = H) gave the 2'-O-phenoxythiocarbonyl esters (2, R = CSOC6Hs). Re-

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