Experimental investigation of jet-induced wall pressure fluctuations over a tangential flat plate at two Reynolds numbers.

The wall pressure fluctuations induced by a subsonic circular jet on a rigid flat plate have been investigated considering two jets with different exit section diameters at the same Mach number. The analysis is aimed at completing the series of papers presented by the authors on the interaction between a subsonic jet and infinite tangential flat plate where the exit Mach number was the only parameter of the jet flow that was varied. In order to analyse other effects out of the Mach number, two configurations with different nozzle exhaust diameters were explored with the objective of isolating the Reynolds number effect keeping fixed the exit Mach number.

Functional composition and diversity of leaf traits in subalpine versus alpine vegetation in the Apennines.

Mediterranean high mountain grasslands are shaped by climatic stress and understanding their functional adaptations can contribute to better understanding ecosystems' response to global change. The present work analyses the plant functional traits of high-elevation grasslands growing in Mediterranean limestone mountains to explore, at the community level, the presence of different plant strategies for resource use (conservative vs. acquisitive) and functional diversity syndromes (convergent or divergent).

Synthetic biology of minimal living cells: primitive cell models and semi-synthetic cells.

This article summarizes a contribution presented at the ESF 2009 Synthetic Biology focused on the concept of the minimal requirement for life and on the issue of constructive (synthetic) approaches in biological research. The attempts to define minimal life within the framework of autopoietic theory are firstly described, and a short report on the development of autopoietic chemical systems based on fatty acid vesicles, which are relevant as primitive cell models is given. These studies can be used as a starting point for the construction of more complex systems, firstly being inspired by possible origins of life scenarioes (and therefore by considering primitive functions), then by considering an approach based on modern biomacromolecular-encoded functions.

Achievements and open questions in the self-reproduction of vesicles and synthetic minimal cells.

Supramolecular chemistry was enriched, about twenty years ago, by the discovery of the self-reproduction of micelles and vesicles. The dynamic aspects and complexity of these systems makes them good models for biological compartments. For example, the self-reproduction of vesicles suggests that the growth in size and number of a vesicle population resembles the pattern of living cells in several aspects, but it take place solely due to physical forces.

Reactivity and fusion between cationic vesicles and fatty acid anionic vesicles.

The fusion between synthetic vesicles is an interesting mechanism for the stepwise construction of vesicle compartments for origins of life models and synthetic biology. In this communication, we report an innovative study on the not well-known case of fusion between oppositely charged vesicles, in particular by using fatty acid vesicles and DDAB as cationic surfactant. By combining fluorescence, turbidity vs.

Biosynthesis of proteins inside liposomes.

Protein expression is the most complex metabolic reaction that has been encapsulated in liposomes, mainly as an intermediate step toward the synthesis of minimal semisynthetic cells. Although there are different experimental approaches to achieving the synthesis of proteins inside liposomes and it is therefore not possible to give a standard recipe, all methods follow a general strategy, which is briefly discussed. On this basis, we provide general indications for designing and realizing protein-expressing liposomes.

The minimal size of liposome-based model cells brings about a remarkably enhanced entrapment and protein synthesis.

The question of the minimal size of a cell that is still capable of endorsing life has been discussed extensively in the literature, but it has not been tackled experimentally by a synthetic-biology approach. This is the aim of the present work; in particular, we examined the question of the minimal physical size of cells using liposomes that entrapped the complete ribosomal machinery for expression of enhanced green fluorescence protein, and we made the assumption that this size would also correspond to a full fledged cell. We found that liposomes with a radius of about 100 nm, which is the smallest size ever considered in the literature for protein expression, are still capable of protein expression, and surprisingly, the average yield of fluorescent protein in the liposomes was 6.

Ser-His catalyses the formation of peptides and PNAs.

The dipeptide seryl-histidine (Ser-His) catalyses the condensation of esters of amino acids, peptide fragments, and peptide nucleic acid (PNA) building blocks, bringing to the formation of peptide bonds. Di-, tri- or tetra-peptides can be formed with yields that vary from 0.5% to 60% depending on the nature of the substrate and on the conditions.

Vesicle behavior: in search of explanations.

In this paper we will present a series of experiments in the general field of surfactant aggregates and, in particular, in vesicle chemistry, which have found no definitive explanation until now. These experiments concern vesicle self-reproduction (in particular, the so-called matrix effect); the interaction between vesicle and RNA, where RNA appears capable of discriminating between vesicles differing slightly in size; the fusion of oppositely charged vesicles, which brings about unexpected behavior of size distribution; and some aspects of local concentration inside vesicles, which still lack clarification in terms of local versus overall concentration. The theoretical and experimental implications of this not yet understood behavior will be discussed, emphasizing that progress in the field must face the difficulty of applying thermodynamics to these kinetically trapped systems, and the general difficulty of understanding how kinetic and thermodynamic factors interplay with each other.

Lecithin-based water-in-oil compartments as dividing bioreactors.

Like liposomes, water-in-oil (w/o) emulsions have recently been used as bioreactors, since they permit facile compartmentation, and therefore the creation of a synthetic cell-like structure. We show here for the first time that lecithin-based w/o compartments can also be used for these purposes and in particular as compartments for hosting complex biochemical reactions that lead to protein synthesis. The expression of enhanced green fluorescent protein (EGFP), used as a model reaction, was followed by fluorescence microscopy.

Question 3: the problem of macromolecular sequences: the forgotten stumbling block.

The Author agrees in principle with the question/statement, but states also that an important qualification is needed within this question. In fact, it is not possible by the bottom up approach to find the conditions for the synthesis of our actual proteins-lysozyme, chymotrypsin or the like--however it is possible to show experimentally that co-oligopeptides chains of that length can be produced by prebiotic reactions. Considering such a synthesis, it is important to recall that proteins-and nucleic acids-are not simply polymers, but are co-polymers, and the kinetics and thermodynamics attending the synthesis of copolymers poses stringent constraints for the biogenesis and growth of specific sequences.

From Never Born Proteins to Minimal Living Cells: two projects in synthetic biology.

The Never Born Proteins (NBPs) and the Minimal Cell projects are two currently developed research lines belonging to the field of synthetic biology. The first deals with the investigation of structural and functional properties of de novo proteins with random sequences, selected and isolated using phage display methods. The minimal cell is the simplest cellular construct which displays living properties, such as self-maintenance, self-reproduction and evolvability.

Approaches to semi-synthetic minimal cells: a review.

Following is a synthetic review on the minimal living cell, defined as an artificial or a semi-artificial cell having the minimal and sufficient number of components to be considered alive. We describe concepts and experiments based on these constructions, and we point out that an operational definition of minimal cell does not define a single species, but rather a broad family of interrelated cell-like structures. The relevance of these researches, considering that the minimal cell should also correspond to the early simple cell in the origin of life and early evolution, is also explained.