Study of DNA-protein coacervates

Abstract

Membraneless organelles (MLOs) are compartments within cells that are not enclosed by a lipid membrane. These structures play important roles in various cellular processes, but many aspects of their formation, stability, and function are not yet fully understood. In this study, model MLOs were prepared and characterized using a system composed of type A gelatin, dextran, and DNA in a solution of PBS (0.01M). The combination of gelatin and dextran in solution result in the formation of a water-in-water emulsion due to the repulsion between the two molecules. However, in the presence of DNA, electrostatic attractive forces between the DNA and the gelatin form coacervate particles, dispersed in the dextran solution. These coacervate particles might have similar properties to the MLOs that exist inside living cells. Nevertheless, the presence of the PBS solution hinders the coacervate formation and cause the coacervates to rapidly coalesce. The present study focuses in investigating the influence of different variables on the formation, size, and stability of these structures in the presence of a buffer solution. It was found that the stability of the coacervates was influenced by the structure of the DNA, with double-stranded (dsDNA) resulting in more stable coacervates than single-stranded (ssDNA). The addition of Pluronic F127 surfactant also improves the stability of the coacervates, slowing down the coalescence process and leading to the formation of relatively stable samples. The fluorescence microscopy analysis confirmed the presence of both gelatin and DNA in the coacervates. It was observed that changes in the concentrations of DNA and dextran affect the size of the coacervates, with higher concentrations leading to the formation of larger particles. In addition, the osmolality of the samples with different dextran concentrations was measured and found to be very similar to plasma osmolality, which is relevant for a potential future application in the biomedical area. Ultimately, it was found that to study the stability of the coacervates over time, the addition of a preservative is necessary to prevent the growth of microorganisms. However, further research is required to fully understand the evolution of these model MLOs over time.