Biology subjects

Choi, S. Q.

Publications and source records attributed to Choi, S. Q..

3 recordsLinked to original sources

bioRxiv2024

Lipid droplet surface promotes three-dimensional morphological evolution of non-rhomboidal cholesterol crystals

Cholesterol crystals, which cause inflammation and various diseases, predominantly grow in a platy, rhomboid structure on the plasma membranes but exhibit an uneven three-dimensional architecture intracellularly. Here, we demonstrate how cholesterol crystallizes in a non-rhomboidal shape on the surface of lipid droplets and develops into three-dimensional sheet-like agglomerates using an in vitro lipid droplet reconstitution system with stereoscopic fluorescence imaging. Our findings reveal that interfacial cholesterol transport on the lipid droplet surface and unique lipid droplet components significantly influence the nucleation-and-growth dynamics of cholesterol crystals, leading to crystal growth in various polygonal shapes. Furthermore, cholesterol crystals readily agglomerate to form large, curved sheet structures on the confined, spherical surfaces of lipid droplets. This discovery enhances our understanding of the volumetric morphological growth of intracellular cholesterol crystals.

biophysics↗

bioRxiv2024

In-situ microscopy-assisted meniscus-guided coating for highly sensitive reduced graphene oxide-based nanocomposite biosensor

Meniscus-guided coating provides great potential for fabricating the nanomaterial-based thin film into high-performance biomedical devices due to the strong relationship between its experimental parameters and the resulting structural properties. However, the complex leverages of various fluid dynamics phenomena hamper optimization of structural properties and device performances. This is due to the absence of in-depth analytical techniques to observe, interpret, and control the solidification process. In this work, we propose an analytical strategy based on the rheological properties of a rGO-based solution using computational fluid dynamics modeling and in situ high-speed microscopy. Through this, we reveal the principles of the solidification mechanism that creates a rGO-based nanocomposite in the form of highly- and evenly-wrinkled thin film and the experimental condition at which this mechanism occurs. The optimized thin film presents high electroconductivity, low chip-to-chip signal variation, and multiplexed electrochemical biosensing performance for three classes of antibodies related to the excessive enrichment of endoplasmic reticulum stress, with detection limits of picomolar levels. This optimizing technique can be universally applied to understanding various solution-based coating systems, and can streamline the production of large-area and high-quality nanocomposite biosensors.

bioengineering↗

bioRxiv2022

Lateral compression of lipids drives transbilayer coupling of liquid-like protein condensates

Liquid-liquid phase separation of proteins has recently been observed on the surfaces of biological membranes, where it plays a role in diverse cellular processes, from assembly of focal adhesions and the immunological synapse, to biogenesis of trafficking vesicles. Interestingly in each of these cases, proteins on both surfaces of the membrane are thought to participate, suggesting that protein phase separation could be coupled across the membrane. To explore this possibility, we used an array of freestanding planar lipid membranes to observe protein phase separation simultaneously on both surfaces of lipid bilayers. When proteins known to engage in phase separation bound to the surfaces of these membranes, two-dimensional, protein-rich phases rapidly emerged. These phases displayed the hallmarks of a liquid, coarsening over time by fusing and re-rounding. Interestingly, we observed that protein-rich domains on one side of the membrane colocalized with those on the other side, resulting in transbilayer coupling. How do liquid-like protein phases communicate across the lipid bilayer? Our results, based on lipid probe partitioning and the differential mobility of proteins and lipids, collectively suggest an entropic coupling mechanism, which relies on the ability of protein phase separation to locally reduce the entropy of the underlying lipid membrane, most likely by increasing lipid packing. Regions of reduced entropy then colocalize across the bilayer to minimize the overall free energy of the membrane. These findings suggest a previously unknown mechanism by which cellular signals originating from one side of the membrane, triggered by protein phase separation, can be transferred to the opposite side.

biophysics↗