Chemical Transformations in Individual Ultrasmall Biomimetic Containers

Chiu, Daniel T.; Wilson, Clyde F.; Ryttsén, Frida; Strömberg, Anette; Farre, Cecilia; Karlsson, Anders; Nordholm, Sture; Gaggar, Anuj; Modi, Biren P.; Moscho, Alexander; Garza-López, Roberto A.; Orwar, Owe; Zare, Richard N.

doi:10.1126/science.283.5409.1892

Cited by 244 publications

(240 citation statements)

References 24 publications

(15 reference statements)

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“…Therefore, we can write an enthalpy conservation equation around the droplet boundary: (2) where the first term on the right side refers to the conductive heat flux at the interface of the droplet and the surrounding organic phase; the second term refers to the laser energy absorbed by the droplet; the third term refers to the mass flux leaving the droplet, carrying with it the enthalpy of mixing, which accounts for the energy of phase change to disperse water from pure phase into the organic phase. Were the droplet surrounded by ambient air, as in typical aerosol experiments, the energy of phase change would refer to the latent heat of vaporization.…”

Section: Laser-onmentioning

confidence: 99%

“…However, strategies to obtain approximate solutions have been developed, and has been discussed succinctly in the literature. 13 Typical approaches involve solving Equations (7) and (8) independently first, assuming that the radius is stationary and the transient response of diffusion is instantaneous such that the steady-state solutions to Equations (7) and (8) can be used to evaluate the mass and temperature flux for Equations (1) and (2). This approach is sometimes referred to as "quasi-stationary".…”

Section: Laser-onmentioning

confidence: 99%

“…However, with the mass diffusion coefficient so much slower in decanol, it is possible that the concentration build-up is so localized that it becomes difficult to deplete the droplet. Figure 3b shows the comparison between acetophenone and decanol, except this time D 2 O was used as the aqueous phase. Again, changing the dispersed phase to D 2 O merely changes the amount of laser radiation absorbed (∼15% relative to H 2 O), the density of the droplet (1.1 g/cc vs 1.0 g/cc) and molecular weight.…”

Section: B Acetophenone Vs Decanolmentioning

confidence: 99%

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Controlled Shrinkage and Re-expansion of a Single Aqueous Droplet inside an Optical Vortex Trap

2007

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This paper describes the shrinkage and re-expansion of individual femtoliter-volume aqueous droplets that were suspended in an organic medium and held in an optical vortex trap. To elucidate the mechanism behind this phenomenon, we constructed a heat and mass transfer model and carried out experimental verifications of our model. From these studies, we conclude that an evaporation mechanism sufficiently describes the shrinkage of aqueous droplets held in a vortex trap, while a mechanism based on the supersaturation of the organic phase by water that surrounds the droplet adequately explains the re-expansion of the shrunk droplet. The proposed mechanisms correlate well with experimental observations using different organic media, when H 2 O was replaced with D 2 O, and when an optical tweezer was used to induce droplet shrinkage rather than an optical vortex trap. For H 2 O droplets, the temperature rise within the droplet during shrinkage was on the order of 1K or less, owing to the rapid thermal conduction of heat away from the droplet at the microscale and the sharp increase in solubility for water by the organic phase with slight elevations in temperature. Because most chemical species confined to droplets can be made impenetrable to the aqueous/organic interface, a change in the volume of aqueous droplets translates into a change in concentration of the dissolved species within the droplets. Therefore, this phenomenon should find use in the study of fundamental chemical processes that are sensitive to concentration, such as macromolecular crowding and protein nucleation and crystallization.

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Section: Laser-onmentioning

confidence: 99%

Section: Laser-onmentioning

confidence: 99%

Section: B Acetophenone Vs Decanolmentioning

confidence: 99%

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Controlled Shrinkage and Re-expansion of a Single Aqueous Droplet inside an Optical Vortex Trap

2007

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“…Since geometric effects play a significant role in the pattern formation, one should be able to take advantage of the powerful microfabrication technology both to explore the consequences of this observation and to provide stringent tests of theoretical models. This system may also find application as a component in a microfluidic screening chip, since it has been shown that subnanoliter vesicles have significant potential as tools for screening of biological and synthetic compounds [14][15][16].…”

mentioning

confidence: 99%

Dynamic Pattern Formation in a Vesicle-Generating Microfluidic Device

et al. 2001

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Spatiotemporal pattern formation occurs in a variety of nonequilibrium physical and chemical systems.Here we show that a microfluidic device designed to produce reverse micelles can generate complex, ordered patterns as it is continuously operated far from thermodynamic equilibrium. Flow in a microfluidic system is usually simple -viscous effects dominate and the low Reynolds number leads to laminar flow. Self-assembly of the vesicles into patterns depends on channel geometry and relative fluid pressures, enabling the production of motifs ranging from monodisperse droplets to helices and ribbons.

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“…In recent years, an increasing variety of materials have been encapsulated within lipid bilayer vesicles. For example, enzymatic reactions including replication and protein synthesis have been demonstrated within the aqueous interior of lipid vesicles (9)(10)(11)(12)(13)(14)(15). Cytoplasmic extracts captured within vesicles maintained enzymatic activity over several days when pore-forming proteins were incorporated in the bilayer (16).…”

mentioning

confidence: 99%

Dynamic microcompartmentation in synthetic cells

Long

Jones

Helfrich

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

229

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An experimental model for cytoplasmic organization is presented. We demonstrate dynamic control over protein distribution within synthetic cells comprising a lipid bilayer membrane surrounding an aqueous polymer solution. This polymer solution generally exists as two immiscible aqueous phases. Protein partitioning between these phases leads to microcompartmentation, or heterogeneous protein distribution within the ''cell'' interior. This model cytoplasm can be reversibly converted to a single phase by slight changes in temperature or osmolarity, such that local protein concentrations can be manipulated within the vesicle interior.aqueous phase separation ͉ intracellular organization ͉ vesicle T he interior of living cells is a crowded milieu of macromolecules, cytoskeletal filaments, and organelles. Even in cytoplasmic regions not separated by obvious barriers such as lipid membranes, differences in local composition are common. This phenomenon, referred to as microcompartmentation, is thought to have profound implications for cell function (1, 2). Understanding its role in living cells has been complicated by the lack of an experimental model system in which hypotheses could be tested. Even the mechanism(s) by which microcompartmentation is maintained remain unclear. Several possibilities have been proposed, including specific targeting and processes driven by macromolecular crowding, such as multiprotein complex formation, binding to intracellular surfaces, or phase separation (3). Aqueous phase separation occurs readily in bulk solutions of macromolecules even at much lower weight percents than are present in living cells (2). Thus, the question has been posed as to whether cytoplasm can exist without undergoing phase separation (4). Phase separation, and the accompanying partition of solutes between phases, could account for microcompartmentation of macromolecules, metabolites, and ions. Thus far, the complexity of living cells has precluded direct testing of the phase separation hypothesis. † We have encapsulated a poly(ethylene glycol) (PEG)͞dextran aqueous two-phase system (ATPS) within lipid vesicles to construct synthetic cells capable of dynamic protein and nucleic acid microcompartmentation. Substantial local variations in protein concentration can be maintained in the absence of intervening membranous barriers within these ATPS-containing vesicles. Our synthetic cytoplasm is promising as an experimental model for intracellular organization in general and demonstrates that aqueous phase separation is a viable mechanism for microcompartmentation.This work represents a bottom-up approach to understanding cell biology, in contrast to the top-down approach often adopted in biochemistry and perhaps best exemplified by efforts to generate the ''minimal cell'' through gene disruption in already simple organisms (6). Experimental model systems such as this one enable us to begin to test hypotheses in cell biology such as that of cytoplasmic phase separation. An analogy is lipid bilayer models of cell membrane...

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Chemical Transformations in Individual Ultrasmall Biomimetic Containers

Cited by 244 publications

References 24 publications

Controlled Shrinkage and Re-expansion of a Single Aqueous Droplet inside an Optical Vortex Trap

Controlled Shrinkage and Re-expansion of a Single Aqueous Droplet inside an Optical Vortex Trap

Dynamic Pattern Formation in a Vesicle-Generating Microfluidic Device

Dynamic microcompartmentation in synthetic cells

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