Visualization of the spontaneous emergence of a complex, dynamic, and autocatalytic system

Abstract

Autocatalytic chemical reactions are widely studied as models of biological processes and to better understand the origins of life on Earth. Minimal self-reproducing amphiphiles have been developed in this context and as an approach to de novo "bottom-up" synthetic protocells. How chemicals come together to produce living systems, however, remains poorly understood, despite much experimentation and speculation. Here, we use ultrasensitive label-free optical microscopy to visualize the spontaneous emergence of an autocatalytic system from an aqueous mixture of two chemicals. Quantitative, in situ nanoscale imaging reveals heterogeneous self-reproducing aggregates and enables the real-time visualization of the synthesis of new aggregates at the reactive interface. The aggregates and reactivity patterns observed vary together with differences in the respective environment. This work demonstrates how imaging of chemistry at the nanoscale can provide direct insight into the dynamic evolution of nonequilibrium systems across molecular to microscopic length scales.autocatalysis | label-free microscopy | interferometric scattering | protocells | emergence

Emergence and Rearrangement of Dynamic Supramolecular Aggregates Visualized by Interferometric Scattering Microscopy

“…In order to avoid multiple binding events, that is, more than one aggregate particle landing on the same diffraction-limited spot within the integration time (0.1 s), we monitored the reactions under comparatively dilute conditions. The possibility of each diffraction limited spot in the iSCAT video being attributed to more than one particle was excluded by considerations of landing rates similar to those described by Ortega-Arroyo et al 30 (see SI for discussion). When the particle concentration exceeds this regime, dilution of aliquots can be used to further follow the reaction (see Figure S4a ).…”

“…All of these factors make it impossible to correlate results obtained by iSCAT in the in situ setup with those from traditional batch experiments obtained by ensemble characterization methods. In fact, the biphasic reactions studied in ref ( 30 ) did not proceed under batch conditions but only in situ on the iSCAT setup where the large surface-to-volume ratio presumably increased the contact area and accelerated the reaction between organic and aqueous components.…”

Artificial intelligence exploration of unstable protocells leads to predictable properties and discovery of collective behavior

“…The understanding of the driving forces influencing these droplets is limited, although Marangoni instabilities, imbalances in surface tension initiated by symmetry breaking, are thought to play a key role (6). Indeed, along with autocatalytic systems (7)(8)(9), chemical gardens (10,11), and other protocell models (12,13), these systems together illustrate how the combination of relatively few components and phase boundaries can lead to complex and "life-like" outcomes. Chemotaxis (14,15) movement in response to chemical stimuli such as a pH or salt concentration gradient has also been observed in simple oil-inwater droplet systems (3,4,(16)(17)(18).…”

Acceleration of Lipid Reproduction by Emergence of Microscopic Motion

“…In this autocatalytic process, the lipid aggregates into micelles that facilitate the coupling of phaseseparated 1-hexanethiol and MPC, and hence the formation of lipids enhances their own formation 21,27 . Where this bond-forming reaction specifically occurs has been the subject of debate in the context of micellar autocatalysis 16,17 .…”