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Luisi P.L.,University of Rome3
Origins of Life and Evolution of Biospheres | Year: 2014

It is argued that closed, cell-like compartments, may have existed in prebiotic time, showing a simplified metabolism which was bringing about a primitive form of stationary state- a kind of homeostasis. The autopoietic primitive cell can be taken as an example and there are preliminary experimental data supporting the possible existence of this primitive form of cell activity. The genetic code permits, among other things, the continuous self-reproduction of proteins; enzymic proteins permit the synthesis of nucleic acids, and in this way there is a perfect recycling between the two most important classes of biopolymers in our life. On the other hand, the genetic code is a complex machinery, which cannot be posed at the very early time of the origin of life. And the question then arises, whether some form of alternative beginning, prior to the genetic code, would have been possible: and this is the core of the question asked. Is something with the flavor of early life conceivable, prior to the genetic code? My answer is positive, although I am too well aware that the term “conceivable” does not mean that this something is easily to be performed experimentally. To illustrate my answer, I would first go back to the operational description of cellular life as given by the theory of autopoiesis. Accordingly, a living cell is an open system capable of self-maintenance, due to a process of internal self-regeneration of the components, all within a boundary which is itself product from within. This is a universal code, valid not only for a cell, but for any living macroscopic entity, as no living system exists on Earth which does not obey this principle. In this definition (or better operational description) there is no mention of DNA or genetic code. I added in that definition the term “open system”-which is not present in the primary literature (Varela, et al., 1974) to make clear that every living system is indeed an open system-without this addition, it may seem that with autopoiesis we are dealing with a perpetuum mobile, against the second principle of thermodynamics. Now consider the following figure (Fig. 1). It represents in a very schematic form a cell, as an open system, with a semipermeable membrane constituted by the chemical S, which permits the entrance of the nutrient A and the elimination of the decay product P. A is transformed inside the cell into S by a chemical reaction characterized by kgen, and S can be transformed into P by the reaction kdec. The two reactions actually may represent two entire families of reaction, in the sense that one can envisage several A and several S and several P. © 2015, Springer Science+Business Media Dordrecht. Source

Luisi P.L.,University of Rome3
Origins of Life and Evolution of Biospheres | Year: 2014

It is pointed out that one of the main reasons of lack of real conceptual progress in the field may lie in the fact that questions concerning the biogenesis of macromolecules have never been asked or addressed in a proper way. We should start again research on the origin of life starting from “ground zero” and focusing on the prebiotic synthesis of ordered sequences of proteins and nucleic acids. © 2015, Springer Science+Business Media Dordrecht. Source

De Lieto Vollaro R.,University of Rome3 | Botta F.,University of Rome3 | De Lieto Vollaro A.,University of Rome La Sapienza | Galli G.,University of Rome La Sapienza
Energy and Buildings | Year: 2014

In the last 50 years the thermal solar panels have been developed mainly for the production of sanitary hot water, but also as an additional source for heating plants. Actually, during the summer season, there is a surplus of thermal energy which can be used as an interesting solution to produce cold by using a simple adsorption system; this can contribute to the air cooling problem with low COP values. The most beneficial adsorbent both for its thermal/physical and low cost is the silica gel, a polymer of silicon dioxide, commonly used for its dehydrating properties, especially in the preservation of electronic material. In this study, a performance thermodynamic balance of a small size system has been made (about 2 kW), adequate to cool an apartment of 70-80 m2 and a TRNSYS simulation has been made to assess in what conformation (surface, storage volume, etc.). A new generation solar power plant is able to guarantee a continuous operation during the summer period. The use of an adsorption system would be favored further in climates in which the solar energy is available, for example in the Arab countries and in some Central Africa countries. © 2014 Elsevier B.V. Source

Luisi P.L.,University of Rome3 | Stano P.,University of Rome3 | de Souza T.,University of Rome3
Origins of Life and Evolution of Biospheres | Year: 2014

We emphasize here that, in considering the initial prebiotic reactions, it is fundamental to take into consideration the critical threshold concentration, in particular when talking about self-replication and initial metabolism. It is also shown that the in situ formation of vesicles in a solution containing macromolecular solutes, permits to obtain filled vesicles which are overcrowded of those solutes and therefore viable for complex biochemical reactions. © 2015, Springer Science+Business Media Dordrecht. Source

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