Biology subjects

Fracassi, A.

Publications and source records attributed to Fracassi, A..

3 recordsLinked to original sources

bioRxiv2026

A Reaction-Driven Condensate-to-Vesicle Transition Selects, Activates, and Spatially Organizes RNA

Living systems depend on the selective concentration of informational polymers within membrane-bound compartments. Liquid-liquid phase-separated condensates efficiently concentrate biomolecules, whereas membrane-bound vesicles provide persistent compartment boundaries. However, direct chemical mechanisms that couple these organizational states remain largely unexplored. Here we report a reaction-driven pathway linking condensates to RNA-enriched lipid vesicles. Electrostatic interactions between cationic thioesters and RNA drive phase separation into reactive condensates. Reaction with cysteine generates membrane lipids and transforms the condensates into unilamellar bilayer vesicles with near-uniform size distribution. The vesicles encapsulate >90% of the RNA from the initial solution and concentrate it by more than two orders of magnitude to >100 {micro}M. Encapsulation is strongly dependent on RNA length, with short oligonucleotides excluded while longer RNAs are selectively retained. Under spatial gradients of the chemical trigger, sharply defined vesicle populations with distinct RNA compositions emerge. Reaction-driven compartmentalization raises local ribozyme and substrate concentrations above the threshold required for catalytic activity, enabling function from otherwise inactive dilute solutions. These findings establish a mechanism by which chemical reactions generate selective, functional, and spatially organized RNA-enriched membrane-bound compartments from heterogeneous molecular mixtures.

biochemistry↗

bioRxiv2025

De Novo Protocell Membrane Formation Fueled by Primitive Metabolites

Lipid membranes define cell boundaries, acting as gatekeepers for transport and signaling. A central principle in biology is that all cellular membranes descend from a common ancestral membrane, as they cannot be generated in the absence of preexisting lipid structures. It is thus unclear how the first protocell membranes originated from membrane-less precursors. Here we demonstrate the de novo generation of lipid bilayers in the absence of any preexisting membranes, membrane-bound proteins, or lipid nanostructure templates. Using acetate as a two-carbon precursor, lipid tails are constructed by soluble enzymes and spontaneously conjugate to cysteine backbones, forming diacyl lipids that assemble into vesicles. Pore-forming peptides facilitate precursor transport into vesicles, allowing the continuous generation of new lipids. Formation of glycolipid membranes creates compartments that can maintain proton gradients. The de novo formation of membrane bilayers using primitive chemical building blocks may have been an intermediary step between primitive prebiotic biochemistry and the emergence of cellular life.

synthetic biology↗

bioRxiv2023

Encoding extracellular modification of artificial cell membranes using engineered self-translocating proteins

A common method of generating artificial cells is to encapsulate protein expression systems within lipid vesicles. However, to communicate with the external environment, protein translocation across lipid membranes must take place. In living cells, protein transport across membranes is achieved with the aid of complex translocase systems which are difficult to reconstitute into artificial cells. Thus, there is need for simple mechanisms by which proteins can be encoded and expressed inside synthetic compartments yet still be externally displayed. Here we present a genetically encodable membrane functionalization system based on mutants of pore-forming proteins. We show that the membrane translocating loop of -hemolysin can be engineered to translocate functional peptides up to 52 amino acids across lipid membranes. Engineered hemolysins can be used for genetically programming artificial cells to display interacting peptide pairs, enabling their assembly into artificial tissue-like structures capable of signal transduction.

synthetic biology↗