Hyerim Park

Optogenetic control of endogenous Ca 2+ channels in vivo

Calcium (Ca2+) signals that are precisely modulated in space and time mediate a myriad of cellular processes, including contraction, excitation, growth, differentiation and apoptosis. However, study of Ca2+ responses has been hampered by technological limitations of existing Ca2+-modulating tools. Here we present OptoSTIM1, an optogenetic tool for manipulating intracellular Ca2+ levels through activation of Ca2+-selective endogenous Ca2+ release−activated Ca2+ (CRAC) channels. Using OptoSTIM1, which combines a plant photoreceptor and the CRAC channel regulator STIM1 (ref. 4), we quantitatively and qualitatively controlled intracellular Ca2+ levels in various biological systems, including zebrafish embryos and human embryonic stem cells. We demonstrate that activating OptoSTIM1 in the CA1 hippocampal region of mice selectively reinforced contextual memory formation. The broad utility of OptoSTIM1 will expand our mechanistic understanding of numerous Ca2+-associated processes and facilitate screening for drug candidates that antagonize Ca2+ signals.

A study of the hydrostatic extrusion of copper-clad aluminium tube

Abstract This paper is concerned with the hydrostatic extrusion process of copper-clad aluminium tube. In this study, the rigid-plastic finite-element method is used to analyze the steady-state extrusion process of the bimetal tube. Simulations are performed for copper-clad aluminium tube to give the distributions of the effective strain rate, equivalent stress and hardness for some extrusion ratios and die angles. In addition, the interface profile of the bimetal tube is predicted by tracking a particle path at the interface in the Eulerian domain. Experiments are carried out for copper-clad aluminium tube at room temperature. It is found that the finite-element predictions are generally in good agreement with the experimental observations. Detailed comparisons of the extrusion loads and interface profiles by the finite-element method with those from experiment are given.

Cytoprotective effects of graphene oxide for mammalian cells against internalization of exogenous materials

To date, graphene oxide (GO), an oxidized version of graphene, has been utilized in many research areas including bioapplications such as drug delivery and bioanalysis. Unlike other spherical or polygonal nanomaterials, GO exhibits a sheet-like structure, which in itself suggests interesting applications based on its shape. Here we show that GO can protect cells from internalization of toxic hydrophobic molecules, nanoparticles, and nucleic acids such as siRNA and plasmid DNA by interacting with cell surface lipid bilayers without noticeably reducing cell viability. Furthermore, the cytoprotective effect of GO against the internalization of extracellular materials enabled spatial control over gene transfection through region-selective gene delivery only into GO-untreated cells, and not into the GO-treated cells.

Optogenetic oligomerization of Rab GTPases regulates intracellular membrane trafficking

Intracellular membrane trafficking, which is involved in diverse cellular processes, is dynamic and difficult to study in a spatiotemporal manner. Here we report an optogenetic strategy, termed light-activated reversible inhibition by assembled trap of intracellular membranes (IM-LARIAT), that uses various Rab GTPases combined with blue-light-induced hetero-interaction between cryptochrome 2 and CIB1. In this system, illumination induces a rapid and reversible intracellular membrane aggregation that disrupts the dynamics and functions of the targeted membrane. We applied IM-LARIAT to specifically perturb several Rab-mediated trafficking processes, including receptor transport, protein sorting and secretion, and signaling initiated from endosomes. We finally used this tool to reveal different functions of local Rab5-mediated and Rab11-mediated membrane trafficking in growth cones and soma of young hippocampal neurons. Our results show that IM-LARIAT is a versatile tool that can be used to dissect spatiotemporal functions of intracellular membranes in diverse systems.

Optogenetic protein clustering through fluorescent protein tagging and extension of CRY2.

Protein homo-oligomerization is an important molecular mechanism in many biological processes. Therefore, the ability to control protein homo-oligomerization allows the manipulation and interrogation of numerous cellular events. To achieve this, cryptochrome 2 (CRY2) from Arabidopsis thaliana has been recently utilized for blue light-dependent spatiotemporal control of protein homo-oligomerization. However, limited knowledge on molecular characteristics of CRY2 obscures its widespread applications. Here, we identify important determinants for efficient cryptochrome 2 clustering and introduce a new CRY2 module, named ‘‘CRY2clust’’, to induce rapid and efficient homo-oligomerization of target proteins by employing diverse fluorescent proteins and an extremely short peptide. Furthermore, we demonstrate advancement and versatility of CRY2clust by comparing against previously reported optogenetic tools. Our work not only expands the optogenetic clustering toolbox but also provides a guideline for designing CRY2-based new optogenetic modules.Cryptochrome 2 (CRY2) from A. thaliana can be used to control light-dependent protein homo-oligomerization, but the molecular mechanism of CRY2 clustering is not known, limiting its application. Here the authors identify determinants of CRY2 clustering and engineer fusion partners to modulate clustering efficiency.

AR Reference Model for K-Culture Time Machine

In this paper, we introduce the K-Culture Time Machine Project, which develops a mobile AR platform for visualizing time-space connected cultural contents of Korea. Existing AR Applications in cultural heritage domains are currently not interoperable and cannot reuse content. To solve this problem, we developed the modified AR reference model as generic framework of a context-aware AR platform; and we developed the context-aware AR platform with several core technologies according to this model. For back-end, we established the Korean Cultural Heritage Data Model (KCHDM) to aggregate the heterogeneous cultural heritage databases in Korea. We also developed the semi-auto time-space correlation generation module for domain experts. Moreover, we developed the authoring tool to generate the time-space connected AR contents. For the front-end, we developed the vision- and sensor-based spatial data composition technology to perform the solid tracking in outdoor environment and context-aware AR framework. Through the UI/UX and 3D contents, whole technologies are packaged into the mobile AR platform. As a validation process for the application, a mobile AR application for the Korean world cultural heritage was developed. Based on this project, an interoperable AR platform that responds with heterogeneous database would be developed and smart tour guide of the cultural heritage site would be possible.

Connecting the Dots: Enhancing the Usability of Indexed Multimedia Data for AR Cultural Heritage Applications through Storytelling

This paper proposes a method to effectively utilize multimedia databases created and indexed by a metadata schema designed specifically for AR applications used at cultural heritage sites. We attempt to do so by incorporating storytelling principles that employ video data for the purpose of providing useful and meaningful guidance at Changdeokgung Palace, a UNESCO World Heritage Site that consists of multiple PoIs. We designed a themed narrative that embeds video data related to the PoIs, creating a guide route that connects each PoI in a fixed order. An extensive between-group user evaluation comparing a search-based AR experience and the proposed narrative-based one was conducted to test and prove the validity and effectiveness of our approach. Our results show that storytelling is indeed a significantly powerful tool to enhance the level of immersion users experience through video data in an AR environment at cultural heritage sites.

Incorporating Geo-Tagged Mobile Videos into Context-Aware Augmented Reality Applications

In recent years, augmented-reality (AR) has been attracting extensive attentions from both the research community and industry as a new form of media, mixing virtual content into the physical world. However, the scarcity of the AR content and the lack of user contexts are major impediments to providing and representing rich and dynamic multimedia content on AR applications. In this study, we propose an approach to search and filter big multimedia data, specifically geo-tagged mobile videos, for context-aware AR applications. The challenge is to automatically search for interesting video segments out of a huge amount of user-generated mobile videos, which is one of the biggest multimedia data, to be efficiently incorporated into AR applications. We model the significance of video segments as AR content adopting camera shooting patterns defined in filming, such as panning, zooming, tracking and arching. Then, several efficient algorithms are proposed to search for such patterns using fine granular geospatial properties of the videos such as camera locations and viewing directions over time. Experiments with real-world geo-tagged video dataset show that the proposed algorithms effectively search for a large collection of user-generated mobile videos to identify top K significant video segments.

Protein Inactivation by Optogenetic Trapping in Living Cells

Optogenetic modules that use genetically encoded elements to control protein function in response to light allow for precise spatiotemporal modulation of signaling pathways. As one of optical approaches, LARIAT (Light-Activated Reversible Inhibition by Assembled Trap) is a unique light-inducible inhibition system that reversibly sequesters target proteins into clusters, generated by multimeric proteins and a blue light-induced heterodimerization module. Here we present a method based on LARIAT for optical inhibition of targets in living mammalian cells. In the protocol, we focus on the inhibition of proteins that modulate cytoskeleton and cell cycle, and describe how to transfect, conduct a photo-stimulation, and analyze the data.

Metadata Design for Location-Based Film Experience in Augmented Places

We present a Markerless 3D Augmented Reality Application for virtual accessory try-on applications around human arm. The system is based on a Kinect sensor and a multi-layer rendering framework to render RGB, depth data and 3D model of accessories simultaneously. The aim is to support realistic visualization of virtual objects around human arm, by detecting wrist pose and handling occlusion for various interactive marketing and retail applications, such as virtual watch try-on.My research focus is on posthumanism: future biomorphic transformations and sculptural reconstruction of the human body. I work with digital—physical sculpture, data art, performance and contemporary technology and materials, such as 3D printing, attempting to bridge the gap between art, science, design and technology. My work investigates a presently topical discourse on the aspects of posthumanism theories, such as bioengineering, gender issues and outer space exploration. Philosophically, I lean on posthumanism theories, uncovered by Cary Wolfe, Daryl Wennemann, N. Katherine Hayles, et al. I further these ideas into sculptural surfaces, enmeshing future skin concept and biomorphic transformations of the skin based on the data from the human body. Current research eventually will result in a multi sensorial experience with mixed reality scenarios — exhibition and performances with augmented to body 3D printed sculptures — a visualisation of humans personal data. The work contributes articulating future possibilities of the relationship of technology and the body. The contribution can be important to the postgender related discussion in relation to digital technologies, data and bodies; to the augmented and mixed reality issues relating to the body and also the themes of embodiment, bodies of matter and data bodies. The objects encapsulate different layers of information and might encourage different perspective on posthumanism.