Molecular Layer-by-Layer Self-Assembly and Mercury Sensing Characteristics of Novel Brush Polymers Bearing Thymine Moieties

Jung, Jungwoon,Kim, Jin Chul,Rho, Yecheol,Kim, Mihee,Kwon, Wonsang,Kim, Heesoo,Ree, Moonhor American Chemical Society 2011 ACS APPLIED MATERIALS & INTERFACES Vol.3 No.7

<P>Two new brush polyoxyethylenes bearing thymine moieties at the bristle ends have been synthesized as model polymers in which the chemical loading of the thymine functional group into the polymer is maximized: poly(oxy(11-thyminoacetyloxyundecylthiomethyl)ethylene) (PECH(S)-T) and poly(oxy(11-thyminoacetyloxyundecylsulfonylmethyl)ethylene) (PECH(SO<SUB>2</SUB>)-T). These brush polymers are thermally stable up to around 225 °C, and their glass transitions occur in the range 23–27 °C, but they have significantly different properties despite the similarity of their chemical structures. In particular, PECH(SO<SUB>2</SUB>)-T films exhibit better performance in sensing mercury ions than PECH(S)-T films. These differences were found to originate in the differences between their morphological structures. The PECH(SO<SUB>2</SUB>)-T film has a multi-bilayer structure without interdigitation, in which the layers stack along the out-of-plane of the film and provide a thymine-rich surface. In contrast, the PECH(S)-T film is amorphous with a relatively low population of thymine moieties at the surface. This study demonstrated that a thymine-rich surface is required for recyclable thymine-based polymers to provide highly improved sensitivity and selectivity as well as full reversibility in the sensing of mercury ions. A thymine-rich surface can be achieved with a brush polymer bearing thymine moieties that can self-assemble into a multi-bilayer structure. Because of the thymine-rich surface, the PECH(SO<SUB>2</SUB>)-T thin films even in only 6 nm thickness demonstrate the detection of mercury ions in aqueous solutions with a detection limit of 10<SUP>–6</SUP> M.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2011/aamick.2011.3.issue-7/am200454x/production/images/medium/am-2011-00454x_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am200454x'>ACS Electronic Supporting Info</A></P>

Self-assembly of novel lipid-mimicking brush polymers in nanoscale thin films

Jung, Jungwoon,Kim, Heesoo,Ree, Moonhor The Royal Society of Chemistry 2014 SOFT MATTER Vol.10 No.5

<P>A series of well-defined poly(oxy(11-phosphorylcholineundecylthiomethyl)ethylene-<I>ran</I>-oxy(<I>n</I>-dodecylthiomethyl)ethylene) (PECH-PC<I>m</I>: <I>m</I> = 0–100 mol% phosphorylcholine (PC)) polymers were used to prepare nanoscale thin films that were characterized by synchrotron X-ray reflectivity (XR) analysis. The quantitative XR analysis provided structural insights into the PECH-PC<I>m</I> thin films. The PECH-PC0 polymer film formed a well-ordered in-plane oriented molecular multibilayer structure, whose individual layers consisted of two sublayers. One sublayer was composed of the fully extended backbones and inner part of the bristles, exhibiting a relatively low electron density, whereas the other sublayer was composed of a bilayer of the outer parts of the bristles without interdigitation. The PECH-PC100 polymer film also formed a well-ordered in-plane oriented molecular multibilayer structure, the individual layers of which were composed of four sublayers rather than two. The bristles in the layer were interdigitated in part <I>via</I> the zwitterionic interactions of the PC end groups. Surprisingly, regardless of the copolymer composition, the PECH-PC<I>m</I> random copolymer molecules in the thin films self-assembled to form a multilayered structure that resembled the structure formed by the PECH-PC100 polymer. These properties have not been observed in other conventional random brush copolymer films. The remarkable multibilayer structures originated from the zwitterionic PC end groups and their favorable interactions and interdigitated structures, which overcame any negative contributions caused by the heterogeneity of the bristles. The unique self-assembly properties of the PECH-PC<I>m</I> polymers always provide a PC-rich surface. The PECH-PC<I>m</I> random copolymers successfully mimicked the molecular bilayer structures formed by natural lipids.</P> <P>Graphic Abstract</P><P>Well-defined lipid-mimicking brush polymers, which contain phosphorylcholine (PC) moieties, have been demonstrated to favorably self-assemble at a molecular level and form a multibilayer structure in thin films, providing a PC-rich surface. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c3sm52263f'> </P>

Novel Brush Polymers with Phosphorylcholine Bristle Ends: Synthesis, Structure, Properties, and Biocompatibility

Kim, Gahee,Park, Samdae,Jung, Jungwoon,Heo, Kyuyoung,Yoon, Jinhwan,Kim, Heesoo,Kim, Ik Jung,Kim, Jung Ran,Lee, Jong Im,Ree, Moonhor WILEY-VCH Verlag 2009 Advanced functional materials Vol.19 No.10

<P>New brush polymers with various numbers of bristle ends incorporating phosphorylcholine (PC) moieties are synthesized. The polymers are thermally stable up to 175 °C and form good-quality films with conventional spin-, roll-, and dip-coating, and subsequent drying processes. Interestingly, all these brush polymers, as a PC-containing polymer, demonstrate a stable molecular multi-bilayer structure in thin films that arise due to the efficient self-assembly of the bristles for temperatures <55 °C and PC-rich surfaces, and therefore successfully mimic natural cell-membrane surfaces. These brush-polymer films exhibit excellent water wettability and water sorption whilst retaining the remarkable molecular multi-bilayer structure, and thus have hydrophilic surfaces. These novel multi-bilayer structured films repel fibrinogen molecules and platelets from their surfaces but also have bactericidal effects on bacteria. Moreover, the brush-polymer films are found to provide comfortable surface environments for the successful anchoring and growth of HEp-2 cells, and to exhibit excellent biocompatibility in mice. These newly developed brush polymers are suitable for use in biomedical applications including medical devices and biosensors that require biocompatibility and the reduced possibility of post-operative infection.</P> <B>Graphic Abstract</B> <P>New brush polymers with various numbers of bristle ends incorporating phosphorylcholine (PC) moieties are synthesized. The new PC-containing brush polymers (see image) form a stable molecular multi-bilayer structure in thin films and successfully mimic natural cell membrane surfaces. The hydrophilic surface of the films repels fibrinogen and platelets and exhibit bactericidal effects. <img src='wiley_img/1616301X-2009-19-10-ADFM200801680-content.gif' alt='wiley_img/1616301X-2009-19-10-ADFM200801680-content'> </P>

Well-Defined DNA-Mimic Brush Polymers Bearing Adenine Moieties: Synthesis, Layer-by-Layer Self-Assembly, and Biocompatibility

Kim, Jin Chul,Jung, Jungwoon,Rho, Yecheol,Kim, Mihee,Kwon, Wonsang,Kim, Heesoo,Kim, Ik Jung,Kim, Jung Ran,Ree, Moonhor American Chemical Society 2011 Biomacromolecules Vol.12 No.7

<P>Two new DNA-mimicking brush polymers were synthesized: poly[oxy(11-(3-(9-adeninyl)propionato)-undecanyl-1-thiomethyl)ethylene] (PECH-AP) and poly[oxy(11-(5-(9-adenylethyloxy)-4-oxopentanoato)undecanyl-1-thiomethyl)ethylene] (PECH-AS). These polymers were found to be thermally stable up to 220 °C and could be applied easily by conventional coating processes to produce good quality films. Interestingly, both brush polymers formed molecular multibilayer structures to provide an adenine-rich surface. Despite the structural similarities, PECH-AS surprisingly exhibited higher hydrophilicity and better water sorption properties than PECH-AP. These differences were attributed to the chemical structures in the bristles of the polymers. The adenine-rich surfaces of the polymer films demonstrated selective protein adsorption, suppressed bacterial adherence, facilitated HEp-2 cell adhesion, and exhibited good biocompatibility in mice. However, the high hydrophilicity and good water sorption characteristics of the PECH-AS film suggest that this brush polymer is better suited to applications requiring good biocompatibility and reduced chance of bacterial infection compared with the PECH-AP film.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/bomaf6/2011/bomaf6.2011.12.issue-7/bm200572t/production/images/medium/bm-2011-00572t_0012.gif'></P>

자동차 차체에서 빗물의 역류 모사에 관한 연구

이정운(Jungwoon Lee),윤재득(Jeadeuk Yun),박성배(Sungbae Park),정융호(Yoongho Jung) (사)한국CDE학회 2012 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2012 No.2

Large number of part design such as for aircraft and automotive development is preceded by functional or sectional design groups for efficiency. With the assembly development of large number of parts, interferences and gaps can be found when the parts and sub-assemblies by those design groups are to be assembled. When rainwater come into the space among parts and is not be drained sufficiently, rainwater within the structure can backflow to gaps or unexpected outlets, which may cause severe problems of part corrosion and electric shock. This research has developed a method and a program to simulate backflow of rainwater within space among parts, which can find unexpected outlets and gaps as in real situation. The developed program can not only simulate up and downstream of liquid, but also the flow with multiple channels of division and joining. The developed method can also be applied to aircraft and ship design process.

자동차 차체에서 빗물의 역류 모사에 관한 연구

이정운(Jungwoon Lee),윤재득(Jeadeuk Yun),박성배(Sungbae Park),정융호(Yoongho Jung) (사)한국CDE학회 2011 한국CDE학회 논문집 Vol.16 No.5

Large number of part design such as for aircraft and automotive development is preceded by functional or sectional design groups for efficiency. With the assembly development of large number of parts, interferences and gaps can be found when the parts and sub-assemblies by those design groups are to be assembled. When rainwater come into the space among parts and is not be drained sufficiently, rainwater within the structure can backflow to gaps or unexpected outlets, which may cause severe problems of part corrosion and electric shock. This research has developed a method and a program to simulate backflow of rainwater within space among parts, which can find unexpected outlets and gaps as in real situation. The developed program can not only simulate up and downstream of liquid, but also the flow with multiple channels of division and joining. The developed method can also be applied to aircraft and ship design process.

Causes and Mechanisms of Hematopoietic Stem Cell Aging

Lee, Jungwoon,Yoon, Suk Ran,Choi, Inpyo,Jung, Haiyoung MDPI 2019 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.20 No.6

<P>Many elderly people suffer from hematological diseases known to be highly age-dependent. Hematopoietic stem cells (HSCs) maintain the immune system by producing all blood cells throughout the lifetime of an organism. Recent reports have suggested that HSCs are susceptible to age-related stress and gradually lose their self-renewal and regeneration capacity with aging. HSC aging is driven by cell-intrinsic and -extrinsic factors that result in the disruption of the immune system. Thus, the study of HSC aging is important to our understanding of age-related immune diseases and can also provide potential strategies to improve quality of life in the elderly. In this review, we delineate our understanding of the phenotypes, causes, and molecular mechanisms involved in HSC aging.</P>

Pharmacological Regulation of Oxidative Stress in Stem Cells

Lee, Jungwoon,Cho, Yee Sook,Jung, Haiyoung,Choi, Inpyo Hindawi 2018 Oxidative medicine and cellular longevity Vol.2018 No.-

<P>Oxidative stress results from an imbalance between reactive oxygen species (ROS) production and antioxidant defense mechanisms. The regulation of stem cell self-renewal and differentiation is crucial for early development and tissue homeostasis. Recent reports have suggested that the balance between self-renewal and differentiation is regulated by the cellular oxidation-reduction (redox) state; therefore, the study of ROS regulation in regenerative medicine has emerged to develop protocols for regulating appropriate stem cell differentiation and maintenance for clinical applications. In this review, we introduce the defined roles of oxidative stress in pluripotent stem cells (PSCs) and hematopoietic stem cells (HSCs) and discuss the potential applications of pharmacological approaches for regulating oxidative stress in regenerative medicine.</P>

고정형 연료전지 계통연계·독립 운전 전환 안전기술 연구

정재환(JAEHWAN JUNG),유수연(SUYEON YU),이정운(JUNGWOON LEE) 한국가스학회 2023 한국가스학회 학술대회논문집 Vol.2023 No.11

연구용원자로에서 수조수관리계통 운전에 따른 수조수 온도 해석

최정운,이선일,박기정,서경우,Choi, Jungwoon,Lee, Sunil,Park, Ki-Jung,Seo, KyoungWoo 대한기계학회 2017 대한기계학회 논문집. Transactions of the KSME. C, 산업기술과 혁신 Vol.5 No.2

국내 유일의 연구용원자로인 하나로(Hi-flux Advanced Neutron Application ReactOr)는 다목적으로 중성자를 이용하기 위해 개방형 수조 내 노심이 존재하는 구조이며, 노심에서 발생되는 핵분열 열을 제거하기 위한 일차 냉각계통, 그리고 연결된 유체계통이 구비되어 있다. 원자로 수조 상부 근방에서 진행되는 방사성 작업 시 작업자의 방사능 피폭을 최소화하기 위해 수조고온층계통에 의해 상부에 고온층이 형성되어 있으며, 다소 저온 영역에 있는 방사능 가스 및 이물질이 상부로 올라오는 것을 방지하기 위해 수조수 온도를 $50^{\circ}C$이하로 제한하고 있으며 이를 위해 수조수관리계통이 연결되어 있다. 수조수관리계통의 구비된 판형열교환기의 열용량을 정상운전 조건에서 260 kW가 되도록 설계하여 각 수조에서 발생되는 열원을 제거하는지에 대해 평가하였고, 원자로 운전 모드와 관계없이 정상적으로 유체계통이 운전된다면 각 수조의 수조수 온도는 제한치 이하를 유지하고 있음을 확인하였다. The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below $50^{\circ}C$ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the designed PWMS heat exchanger has enough capacity with the design margin regardless of the reactor operation mode.