Hyun Kyu Choi

A pathway for helical membrane proteins Membrane proteins are inserted into cell membranes while they are being translated and may fold concurrently into their secondary and tertiary structures. Choi et al. describe a single-molecule force microscopy technique that allowed them to monitor folding of helical membrane proteins in vesicles and bicelles. Two helical membrane proteins, the Escherichia coli rhomboid protease GlpG and the human β 2 -adrenergic receptor, both folded from the N to the C

Single-molecule magnetic tweezers deliver magnetic force and torque to single target molecules, permitting the study of dynamic changes in biomolecular structures and their interactions. Because the magnetic tweezer setups can generate magnetic fields that vary slowly over tens of millimeters-far larger than the nanometer scale of the single molecule events being observed-this technique can maintain essentially constant force levels during biochemical experiments while generating a biologically

The TCR integrates forces in its triggering process upon interaction with pMHC. Force elicits TCR catch-slip bonds with strong pMHCs but slip-only bonds with weak pMHCs. We develop two models and apply them to analyze 55 datasets, demonstrating the models' ability to quantitatively integrate and classify a broad range of bond behaviors and biological activities. Comparing to a generic two-state model, our models can distinguish class I from class II MHCs and correlate their structural parameters

Abstract This work presents the application of a Koopman operator approach to a batch pulp digester. To manufacture paper products with desired properties, it is essential to consider both macroscopic and microscopic attributes of pulp. However, the complexity of multiscale dynamics of pulping processes hinders proper control system design. Therefore, we utilize extended dynamic mode decomposition (EDMD), which is based on Koopman operator theory, to derive a global linear representation of a pu

Abstract This work proposes a multiscale modeling and model‐based feedback control framework for the delignification process in a batch‐type pulp digester. Specifically, we focus on a hardwood chip in the digester and develop a multiscale model capturing both the evolution of microscopic properties such as the pore size and shape distributions in the solid phase and the dynamic changes in the temperature and component concentrations in the liquor phase. While the macroscopic model adopts the con

Abstract Even though it is widely known that mechanical properties of papers are dependent upon fiber morphology such as fiber length and cell wall thickness, existing macroscopic models are limited in describing the microscopic traits of pulp. Thus, we proposed a multiscale model by integrating a macroscopic model (i.e., Purdue model ) and a microscopic model (i.e., kinetic Monte Carlo algorithm) to capture the dynamic evolution of the fiber morphology as well as conventional pulp quality index

Even though continuous pulp processes have been studied for many years, the absence of a model that can accurately describe the evolution of fiber morphology has impeded the application of advanced control techniques. In this study, a multiscale model for continuous Kraft pulping processes, which can capture the spatiotemporal evolution of wood chips and cooking liquor, is developed by integrating a macroscopic model (i.e., Purdue model) with a microscopic model (i.e., kinetic Monte Carlo algori

We recently discovered that the nature of lectin multivalency and glycolipid diffusion on cell membranes could lead to the heteromultivalent binding (i.e., a single lectin simultaneously binding to different types of glycolipid ligands). This heteromultivalent binding may even govern the lectin-glycan recognition process. To investigate this, we developed a kinetic Monte Carlo simulation, which only considers the fundamental physics/chemistry principles, to model the process of lectin binding to

B cell maturation depends on cognate interactions between the T and B cells. Upon interaction with CD40 ligand (CD40L) on T cells, CD40 delivers costimulatory signals alongside B cell antigen receptor (BCR) signaling to regulate affinity maturation and antibody class switch. Mutations affecting CD40-CD40L interactions cause abnormal antibody responses in immunodeficiencies known as X-linked hyper-IgM syndrome (X-HIgM). Here, we study the CD40-mediated mechanotransduction in B cells, which likely

Catch bonds are molecular bonds that last longer under force than slip bonds, which become shorter-lived under force. Although catch bonds were initially discovered in studies of leukocyte and bacterial adhesions two decades ago, they have since been found in many other contexts, including platelet binding to blood vessel walls during clotting, structural support within the cell and between cells, force transmission in the cell's machineries for motility and mechanotransduction, viral infection

ABSTRACT Central to T cell biology, the T cell receptor (TCR) integrates forces in its triggering process upon interaction with peptide-major histocompatibility complex (pMHC) 1-3 . Phenotypically, forces elicit TCR catch-slip bonds with strong pMHCs but slip-only bonds with weak pMHCs 4-10 . While such correlation is commonly observed, the quantitative bond pattern and degree of “catchiness” vary. We developed two models based on the structure, elastic properties, and force-induced conformation