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Liquid Crystal Coacervates Composed of Short Double-Stranded DNA and Cationic Peptides
Tommaso P. Fraccia and Tony Z. Jia
ACS Nano - 14, 11 15071–15082 - - 2020
Phase separation of nucleic acids and proteins is a ubiquitous phenomenon regulating subcellular compartment structure and function. While complex coacervation of flexible single-stranded nucleic acids is broadly investigated, coacervation of double-stranded DNA (dsDNA) is less studied because of its propensity to generate solid precipitates. Here, we reverse this perspective by showing that short dsDNA and poly-l-lysine coacervates can escape precipitation while displaying a surprisingly complex phase diagram, including the full set of liquid crystal (LC) mesophases observed to date in bulk dsDNA. Short dsDNA supramolecular aggregation and packing in the dense coacervate phase are the main parameters regulating the global LC-coacervate phase behavior. LC-coacervate structure was characterized upon variations in temperature and monovalent salt, DNA, and peptide concentrations, which allow continuous reversible transitions between all accessible phases. A deeper understanding of LC-coacervates can gain insights to decipher structures and phase transition mechanisms within biomolecular condensates, to design stimuli-responsive multiphase synthetic compartments with different degrees of order and to exploit self-assembly driven cooperative prebiotic evolution of nucleic acids and peptides.
Elasticity and Viscosity of DNA Liquid Crystals
Liana Lucchetti, Tommaso P. Fraccia, Giovanni Nava, Taras TurivTaras Turiv Advanced Materials and Liquid Crystal Institute, Chemical Physics Interdisciplinary Program, Kent State University, Kent, Ohio 44242, United States More by Taras Turiv , Fabrizio
ACS Nano - 9, 7 1034–1039 - - 2020
Concentrated solutions of blunt-ended DNA oligomer duplexes self-assemble in living polymers and order into lyotropic nematic liquid crystal phase. Using the optical torque provided by three distinct illumination geometries, we induce independent splay, twist, and bend deformations of the DNA nematic and measure the corresponding elastic coefficients K1, K2, and K3, and viscosities ηsplay, ηtwist, and ηbend. We find the viscoelasticity of the system to be remarkably soft, as the viscoelastic coefficients are smaller than in other lyotropic liquid crystals. We find K1 > K3 > K2, in agreement with the elasticity of the nematic phase of flexible polymers, and ηbend > ηsplay > ηtwist a behavior that is nonconventional in the context of chromonic, polymeric, and thermotropic liquid crystals, indicating a possible role of the weakness and reversibility of the DNA aggregates.
Liquid Crystal Peptide/DNA Coacervates in the Context of Prebiotic Molecular Evolution
Tommaso P. Fraccia and Tony Z. Jia
CRYSTALS - 10(11) 964 - - 2020
Liquid–liquid phase separation (LLPS) phenomena are ubiquitous in biological systems, as various cellular LLPS structures control important biological processes. Due to their ease of in vitro assembly into membraneless compartments and their presence within modern cells, LLPS systems have been postulated to be one potential form that the first cells on Earth took on. Recently, liquid crystal (LC)-coacervate droplets assembled from aqueous solutions of short double-stranded DNA (s-dsDNA) and poly-L-lysine (PLL) have been reported. Such LC-coacervates conjugate the advantages of an associative LLPS with the relevant long-range ordering and fluidity properties typical of LC, which reflect and propagate the physico-chemical properties of their molecular constituents. Here, we investigate the structure, assembly, and function of DNA LC-coacervates in the context of prebiotic molecular evolution and the emergence of functional protocells on early Earth. We observe through polarization microscopy that LC-coacervate systems can be dynamically assembled and disassembled based on prebiotically available environmental factors including temperature, salinity, and dehydration/rehydration cycles. Based on these observations, we discuss how LC-coacervates can in principle provide selective pressures effecting and sustaining chemical evolution within partially ordered compartments. Finally, we speculate about the potential for LC-coacervates to perform various biologically relevant properties, such as segregation and concentration of biomolecules, catalysis, and scaffolding, potentially providing additional structural complexity, such as linearization of nucleic acids and peptides within the LC ordered matrix, that could have promoted more efficient polymerization. While there are still a number of remaining open questions regarding coacervates, as protocell models, including how modern biologies acquired such membraneless organelles, further elucidation of the structure and function of different LLPS systems in the context of origins of life and prebiotic chemistry could provide new insights for understanding new pathways of molecular evolution possibly leading to the emergence of the first cells on Earth
Stable liquid foams from a new polyfluorinated surfactant
Maria Russo, Zacharias Amara, Johan Fenneteau, Pauline Chaumont-Olive, Ilham Maimouni, Patrick Tabeling and Janine Cossy
Chem. Comm. - 56 5807-5810 - - 2020
Liquid foams exhibiting long-term stability are a key-challenge in material design. Based on this perspective, new pyridinium polyfluorinated surfactants were synthesized from simple building blocks enabling unusually stable liquid foams. While the batch-generated foams were used for qualitative foaming evaluation, microfluidics allowed a quantitative insight into the aging effects of monodisperse foams.
Predicting Evolution Using Regulatory Architecture
Philippe Nghe , Marjon G J de Vos , Enzo Kingma , Manjunatha Kogenaru , Frank J Poelwijk , Liedewij Laan , Sander J Tans
Annu Rev Biophys - 6(49) 181-197 - doi: 10.1146/annurev-biophys-070317-032939 - 2020
The limits of evolution have long fascinated biologists. However, the causes of evolutionary constraint have remained elusive due to a poor mechanistic understanding of studied phenotypes. Recently, a range of innovative approaches have leveraged mechanistic information on regulatory networks and cellular biology. These methods combine systems biology models with population and single-cell quantification and with new genetic tools, and they have been applied to a range of complex cellular functions and engineered networks. In this article, we review these developments, which are revealing the mechanistic causes of epistasis at different levels of biological organization-in molecular recognition, within a single regulatory network, and between different networks-providing first indications of predictable features of evolutionary constraint.

Thresholds in origin of life scenarios
Jeancolas, C., Malaterre, C., & Nghe, P.
Iscience - 23(11) 101756 - - 2020
Predicting Evolutionary Constraints by Identifying Conflicting Demands in Regulatory Networks
M., Nghe, P., Poelwijk, F.J. and Tans, S.J.
Cell systems - 10(6) 526-534 - - 2020
Metabolic cost of rapid adaptation of single yeast cells
Gabrielle Woronoff, Philippe Nghe, Jean Baudry, Laurent Boitard, Erez Bra
PNAS - 117 (20) 10660-10666 - - 2020
We establish, using single-cell analysis of metabolism and division in a droplet microfluidic system, that yeast can adapt, resuming division, extremely rapidly to an unforeseen environmental challenge, and that adaptation is an active process, requiring the consumption of a characteristic amount energy. The adapted state is stable over at least several days, showing that this is a genuine adaptation process. The adaptation rate (10−3 cells per hour) is orders of magnitude higher than expected based on known mutation rates, suggesting an epigenetic origin, and the tight energetic coupling implies that there is active exploration of different states, and fixation of the solution(s) that allow adaptation.

Universal motifs and the diversity of autocatalytic systems
Blokhuis, A., Lacoste, D., & Nghe, P
Proceedings of the National Academy of Sciences of the United States of America - 117(41) 25230-25236 - - 2020
The generality of transient compartmentalization and its associated error thresholds
Alex Blokhuis, Philippe Nghe , Luca Peliti , David Lacoste
J Theor Biol . - 487 110110 - doi: 10.1016/j.jtbi.2019.110110 - 2020
Can prelife proceed without cell division? A recently proposed mechanism suggests that transient compartmentalization could have preceded cell division in prebiotic scenarios. Here, we study transient compartmentalization dynamics in the presence of mutations and noise in replication, as both can be detrimental the survival of compartments. Our study comprises situations where compartments contain uncoupled autocatalytic reactions feeding on a common resource, and systems based on RNA molecules copied by replicases, following a recent experimental study. Using the theory of branching processes, we show analytically that two regimes are possible. In the diffusion-limited regime, replication is asynchronous which leads to a large variability in the composition of compartments. In contrast, in a replication-limited regime, the growth is synchronous and thus the compositional variability is low. Typically, simple autocatalysts are in the former regime, while polymeric replicators can access the latter. For deterministic growth dynamics, we introduce mutations that turn functional replicators into parasites. We derive the phase boundary separating coexistence or parasite dominance as a function of relative growth, inoculation size and mutation rate. We show that transient compartmentalization allows coexistence beyond the classical error threshold, above which the parasite dominates. Our findings invite to revisit major prebiotic transitions, notably the transitions towards cooperation, complex polymers and cell division.


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65 publications.