Localization of Goα in the Developing and Adult Mouse Brain : 발생 중인 신경세포와 성체 생쥐 뇌에서의 Goα 단백질 발현 위치

Cha Hye Lim 아주대학교 2013 국내석사

-Abstracts- Localization of Goα in the Developing and Adult Mouse Brain Heterotrimeric G proteins mediate signal transduction generated by hormone and neurotransmitters. Among G proteins, Go, a member of the Gi/o family, is the most abundant heterotrimeric G protein in the brain but the roles and effectors for the Go have not been clearly defined. As previously reported, the expression of Go protein is found in various brain regions, including cerebrum, hippocampus, thalamus, and cerebellum. Although Go is already known to be present on both plasma- and endo-membranes, the precise subcellular location of Go protein has been a controversial issue because diverse detection methods such as in situ hybridization versus and immunohistochemistry yielded apparently contradictory results. We previously found that Go functions as a signaling scaffolding molecule that determines the subcellular localization of cAMP-dependent protein kinase A (Ghil et al., 2006). In this study, we showed that Go is expressed in Purkinje cell dendrites of developing and adult cerebellum by comparing the Go expression in wild type and Go knockout mice and confirm the subcellular location of Go protein through the hippocampal neuron in vitro culture. Consequently, this study provides more accurate information to speculate the role of Go protein on the basis of its correct localization as a character of the Go.

Go 단백질에 의한 Protein Kinase A 신호 전달 경로의 구획화 : Compartmentalization of Protein Kinase A Signaling by a Heterotrimeric G Protein, Go

최정미 아주대학교 2008 국내박사

G 단백질은 호르몬과 신경 전달물질에 의해서 발생되는 신호를 전달하는 역할을 한다. 모든 G 단백질 중에서 Gi/o 단백질 집단에 속하는 Go 단백질은 뇌조직에 많은 양이 존재한다. 지금까지 보고된 Go의 활성에 관한 많은 결과들은 그들의 Gβγ에 때문이라는 설명을 하고 있지만 Goα를 과발현 시킨 F11 세포에서 cAMP로 분화를 유도하면 신경 돌기의 길이 성장이 억제되는 것과 같이 이러한 Gβγ를 매개하는 것 같지 않은 효과들은 아마도 아직 밝혀지지 않은 Goα의 효과자가 존재할 것을 암시한다. 이 논문의 PART I에서 우리는 Goα가 GTPase 부위를 통해 PKA와 결합하며, 막 분획에서 PKA와 함께 존재하며, PKA의 촉매 소단위체 (catalytic subunit)의 핵 안으로의 전이를 억제함을 관찰하였다. 그러나 이러한 Goα와 PKA-Cα 간의 결합은 PKA의 인산화 활성을 방해하지 않았다. 결론적으로 이러한 결합은 PKA를 매개로 한 핵 안에서의 CREB 활성은 억제하는 반면, 세포질에서 PKA에 의한 β-catenin의 인산화나 Rap1의 활성은 그대로 남겨 두었다. 이러한 결과들은 Goα가 막/세포질 구획에 PKA를 고립시킴으로써 PKA 신호의 갈라짐에서 중요한 역할을 한다는 것을 보여준다. PKA 신호의 갈라짐에 있어서의 Goα에 의한 새로운 조절 메커니즘은 아마도 세포 변형 (cell transformation), 장기간 약물 처리 후에 나타나는 과민감화 (hypersensitization), 활성 의존적인 유전자의 발현, 그리고 신경 세포에서의 시냅스 재구성 동안의 신경 돌기 형성 (dendritic morphogenesis)과 같은 복잡한 과정을 어떻게 Goα가 조절하는 지에 대한 식견을 제공해 줄 것이다. 이 논문의 PART II에서는 Goα 결여 생쥐에서 관찰되는 신경학적으로 비정상적인 여러 행동들을 조사하였다. 예를 들어, Goα 결여 생쥐들은 다양한 여러 테스트들 (rotarod, open field, elevated plus maze, forced swim 테스트) 에서 심각한 운동 조절의 이상 및 높은 수준의 운동성 (hyperlocomotor)을 보여 주었다. Goα의 결여는 감소된 불안 (anxiety) 및 증가된 우울 (depression)의 경향을 보여주었다. 또한 Goα 결여 생쥐에서는 PKA의 소단위체 중의 하나인 RIIβ 결여 생쥐와 AC 5 결여 생쥐에서 관찰되는 바와 같이 도파민 D2 수용체의 길항제인 haloperidol에 의해 강경증 (catalepsy)이 유도되지 않았다. Goα, RIIβ 그리고 AC5 결여 생쥐들에서 보여지는 비슷한 행동 패턴들은 Goα가 PKA의 catalytic 소단위체와 결합하여 그들의 활성을 조절하며, 그럼으로써 PKA와 관련된 다양한 생리학적인 반응들이 일어나게 된다는 이전의 in vitro 결과를 지지해 준다. 이 논문의 PART III에서는 Goα 결여 생쥐에서 페로몬 관련 기관들의 조직학적 분석 및 성적 행동을 조사하였다. 척추동물에 있어서 페로몬은 다양한 사회적 행동을 촉진하고 조절하는데 있어서 중요한 역할을 한다. 대부분의 포유류의 후각 시스템에는 서로 분리된 두 기관인 주후각상피 (MOE)와 보습코기관 (VNO)이 존재한다. 고전적으로 보습코기관 (VNO)이 페로몬 감지를 담당하는 특수한 기관으로 인식되어 왔으나, 최근의 논문들에 의하면 주후각기관 (MOE) 역시 페로몬에 의해 조절되는 다양한 행동들과 관련되어 있으며, 보습코기관 (VNO)을 통한 신호전달은 성행동의 시작보다는 오히려 성분별과 관련되어 있다. Goα 결여 생쥐는 암컷과 수컷 모두 새끼를 번식하지 못한다. Goα 결여 수컷 생쥐에서 수컷 특이적인 성행동인 head-mounting과 mounting의 빈도가 현저하게 감소하였다. Goα 결여 생쥐의 후각 능력은 정상적인 반면, 페로몬 지각 능력은 감소하였다. Goα 결여 생쥐에서 Goα의 발현은 보습코기관 (VNO)의 기저층 (basal layer)과 보조후각망울 (AOB)의 후부쪽 (posterior part)에서 사라졌다. 흥미롭게도 Goα 결여 생쥐에서 Goα의 발현이 사라진 이 부분들은 심하게 변질 (degradation) 되었다. 그 외 Goα 결여 생쥐의 주후각기관 (MOE) 세포들의 발생 과정에서도 문제가 있는 것을 확인하였다. 그러나 Goα 결여 생쥐의 정낭 (seminal vesicle), 고환 (testis)과 같은 수컷 생식 기관들은 야생형 (wild-type) 생쥐와의 해부학적인 차이가 발견되지 않았다. 이 결과는 Goα 결여 생쥐에서 관찰되는 성적 행동의 이상은 아마도 수컷 생식 기관의 발생학적인 문제 때문이라기 보다는 페로몬 감지 기관의 이상 때문인 것으로 생각된다. Heterotrimeric G proteins mediate signal transduction generated by hormones and neurotransmitters. Among all G proteins, Go, a member of the Gi/o family, is the most abundant heterotrimeric G protein in brain, being present on both plasma- and endo- membranes. To date all consequences of trimeric Go activation for which there is a mechanistic explanation have been shown to be due to its Gβγ dimmers. Roles and effectors for the Goα subunit have not been clearly defined. Yet, overexpression of Goα has profound effects, including cAMP-induced inhibition of neurite outgrowth, which are unlikely mediated by Gβγ dimmers and suggest existence of unidentified Goα effector(s). In PART I, we showed that Goα interacts directly with cAMP dependent protein kinase (PKA) through its GTPase domain, colocalizes with PKA in membrane fractions, and inhibits nuclear translocation of the catalytic subunit of PKA. These interactions between Goα and PKA-Cα did not block the kinase activity of PKA. As the result, these interaction repressed PKA-mediated-activation of cAMP-responsive element binding protein (CREB) in the nucleus whereas spared phospholyration of β-catanin and activation of Rap1 by PKA in the cytosol. The results indicate that Goα plays a pivotal role in bifurcation of PKA signaling by sequestering the PKA in the membrane/cytosolic compartments. This novel regulatory mechanism of bifurcating PKA signaling by Goα may provide insight into how Goα regulates complex processes such as cell transformation, hypersensitization after prolonged drug treatments, activity-dependent gene expression, and dendritic morphogenesis during synaptic reorganization in neurons. In PART II, we investigated the neurologically abnormal behaviors in Goα knock-out mice. For example, Goα knock-out mice exhibited severe motor control impairment as tested rotarod, open field, elevated plus maze and forced swim tests, as well as a high level of locomotor activity. Ablation of Goα reduced anxiety while increasing more depressiveness. Thus, catalepsy was not induced by haloperidol, a dopamine receptor D2R antagonist, in Goα knock-out mice as found in mice defective in cAMP-PKA signaling pathway including RIIβ, a regulatory subunit of PKA or adenylyl cyclase (AC) 5. Similar behavior deficits found in Goα, RIIβ, and AC5 knock-out mice support our previous in vitro finding that Goα may interact with the catalytic subunit of PKA and modulate its activity, and thereby evoke various PKA-related physiological responses. In PART III, we investigated anatomical alteration of the pheromone-related organs and sexual behaviors in Goα knock-out mice. In most mammals, there are two separated olfactory systems, main olfactory epithelium (MOE) and vomeronasal organ (VNO). We showed the evidence that Go is required for detecting pheromone and evoking sexual behavior. Goα knock-out male mice showed lower frequencies of head-mounting and mounting behavior. In the Goα knock-out male mice, the pheromone sensation was markedly diminished whereas the olfaction was normal. Loss of Goα caused degeneration of cells in the basal layer of VNO as well as their target neurons in the posterior portion of accessory olfactory bulb. Moreover these mice showed additional defects in the MOE. There are no anatomical differences in male reproductive organs, such as testis and seminal vesicles between wild type and Goα knock-out mice. The data suggest that the absence of sexual interaction in Goα knock-out male mice is not due to abnormal development of male reproductive organs nor the male sex hormones, but rather defects in neurological processing that was triggered by pheromones in VNO and MOE.

Go 단백질의 알파 소단위체에 의한 신경돌기형성의 조절

오휘현 아주대학교 아주대학교 일반대학원 2016 국내석사

Heterotrimeric G protein은 많은 신경전달물질과 호르몬에 의해서 일어나는 신호전달을 중개한다. 모든 G 단백질들 중에서, Go는 신경세포분화에 관여한다고 알려져 있지만 어떻게 중재하는지는 명확히 알려진 바가 없다. 이전 연구에서 Goα가 F11 세포에서 신경돌기진전(neurite outgrowth)을 조절한다는 것을 보았다. Goα가 과발현되는 세포에서 신경돌기의 평균길이는 감소하였으나 세포당 신경돌기의 수는 반대로 증가하였고 이러한 양상은 cAMP-PKA-CREB 신호에 의해 매개되었다. 본 연구에서는 신경돌기형성 과정 동안 Go의 기능획득과 기능상실변이를 F11 세포와 일차신경세포에서 각 각 조사하고 그 기작을 밝혀내는데 목적이 있다. 이를 위해 미세소관과 액틴과 같은 세포뼈대단백질(cytoskeletal protein)의 양상을 관찰하였다. Go가 없는 조건의 배측피질 신경세포(dorsal cortical neuron)에서 짧은 돌출부(short protrusion) 또는 신경돌기(neurite)가 적게 나타났으며 형성 시기 또한 늦어졌다. 반면 F11 세포에서 Goα를 과발현 시킨 후 시간의 흐름에 따라 관찰하였을 때, 신경분화 초기단계에서 Goα가 신경돌기형성을 유도함을 보았다. 이러한 Goα는 PKA의 catalytic subunit(c)과 물리적으로 결합하며 이러한 결합이 세포 내 PKA-Cα가 핵으로의 이동을 억제함을 확인하였다. 더불어 PKA-Cα가 세포의 핵보다 세포질에서 과발현 되었을 때 형태학적으로 Goα가 과발현 되었을 때와 비슷한 양상을 보임을 관찰함으로써 결론적으로 Goα가 PKA-Cα의 위치를 영향을 줌으로써 신경돌기형성에 기능을 한다는 것을 알 수 있다.

Multi-Strategic Learning, Reasoning and Searching in the Game of Go

이병두 The University of Auckland 2004 해외박사

Go is a fascinating research domain for exploring new approaches in Artificial Intelligence(AI). In spite of its very simple rules, computer Go is much more difficult to implement than computer chess, because Go is an extremely complex strategic board game and has a vast search space. The traditional AI approach when faced with a board game problem is to search the space of all possible moves to find the best move sequence that leads to an advantageous position. Heuristic searching methods are often used to tackle the problem. As Go is a complete-knowledge, deterministic and strategic game with extreme complexity, these approaches are not feasible in computer Go. Computer Go must be tackled with Go knowledge-intensive approaches rather than just the heuristic searching methods that are applied to computer chess. A lot of Go knowledge has been accumulated over the past several centuries by human master players. Most of it is implicit in the form of expert games. The patterns recognised by human players are more than just stones and empty spaces. That is, players intuitively perceive the life-and-death status of surrounded groups, and select an effective next move in a certain Go board position with a priori knowledge of Go concepts such as influence, the safety of groups, connectedness between groups etc. This visual nature in Go is easy for human perception but hard to model with computers. In this thesis, we classify Go knowledge into implicit Go knowledge and explicit Go knowledge. Because implicit Go knowledge is embedded in prototypical professional Go games as pattern knowledge, we use pattern recognition capability to infer implicit knowledge from professional Go games. Meanwhile, explicit Go knowledge is represented as Go propositions (including Go proverbs, Go maxims and Go terms), and thus we apply Go term knowledge to a rule-based fuzzy reasoning model to solve problems in the opening game. This thesis discusses and implements a learning model, a reasoning model and a heuristic searching model. The learning model is a neural network for Temporal Difference (TD) learning with pattern recognition capability. The reasoning model includes a neuro-fuzzy controller for fuzzy reasoning using Go term knowledge based on pattern knowledge. Both models are applied to the full-sized (1919) opening games of Go instead of a simplified version(e.g.9×9), which is often used to study AI methods in Go. Additionally, the heuristic searching model is applied to solving life-and-death problems in a local domain. Firstly, we analyse the feasibility of applying a TD(λ) learning model in the opening game of Go. We implement TD(λ) learning with a neural network to predict the next stone moves, to evaluate the different opening styles and to find the most favourable opening game for black, and then evaluate the performance of TD(λ). The empirical result for predicting the next stone moves is promising, but there is no guarantee that TD(λ) will always pick the same opening game, which is one of the most favourable opening games for black, independent of different values. The competition between two TD(λ)s shows that it is difficult to clearly say that which TD(λ) is better, with a few games played between two TD(λ)s. Secondly, we discuss the implementation of a novel fuzzy reasoning model, which includes three components: (1) a neural network with supervised learning to generate the candidate moves, (2) a heuristic evaluator of the candidate moves, and(3) an adapted neuro-fuzzy controller to decide the best next move. We also let the fuzzy reasoning model play against TD(λ) learning to test the performance. The experimental result reveals that even the simple fuzzy reasoning model can compete against TD(λ) learning and it shows great potential to be applied to the real game of Go. Finally, we construct a heuristic searching model that enables the reduction of the branching factor in a game tree for solving life-and-death problems. The set of first moves in a game tree composes a set of candidate moves generated by pattern clustering and a set of possible moves generated by shape analysis. Then α-βsearching is conducted to find the best sequence of moves for solving life-and-death problems. The empirical result shows that when there is a complete boundary between black and white, the sequence of moves generated is almost always correct, except that it does not deal well with fighting. Meanwhile, α-βsearching does not generate a correct sequence of moves for solving problems that have an incomplete boundary between black and white. Keywords: α-βSearching, Complexity, Computer Go, Distance Transform, Eye Shape Analysis, Explicit Go Knowledge, Go Knowledge, Implicit Go Knowledge, Influence, Learning, Mamdani Fuzzy Model, Neural Network, Neuro-Fuzzy Reasoning, Pattern Clustering, Pattern Recognition, Reasoning, Rein-forcement Learning, Searching, Sugeno Fuzzy Model, Super vised Learning, Temporal Difference (TD) Learning, Tsukamoto Fuzzy Model, Unsupervised Learning.

PEBAX-GO와 PTMSP-GO 복합막에 의한 기체분리

이슬기 상명대학교 일반대학원 2017 국내석사

본 연구는 PEBAX (Poly ether block amide)와 PTMSP (poly-1-trymethyl-silyl-propyne)에 GO (Graphene Oxide)를 첨가하여 solution-mixing 방법으로 고분자나노복합막을 제조하여 N2, O2, CH4, CO2 단일기체에 대한 기체투과특성을 연구하였다. PEBAX-GO, PTMSP-GO, PEBAX-syn.GO 복합막에 대한 특성은 FT-IR, TGA, SEM 분석을 통해 확인하였고, GO의 특성은 XRD 분석을 통하여 확인하였다. GO의 분산성을 용액 상태일 때와 제막된 형태로 확인한 결과 PEBAX 용액에 첨가한 GO는 24시간 이후에도 분산이 잘 유지되었고 제조된 막의 형태 또한 분산이 잘됨을 육안으로 확인하였다. FT-IR분석 결과, GO는 1730 cm-1에서는 카르복실기의 C=O 신축진동피크, 1620 cm-1에서 aromatic C=C의 피크, 1060 cm-1에서는 알콕시기 피크가 관찰되었고, PEBAX-GO 복합막과 PTMSP-GO 복합막은 고분자 고유의 작용기 피크가 GO 함량이 증가함에 따라 피크의 강도가 약해졌으나 새로운 피크는 관찰되지 않아 고분자와 GO사이에 화학적 결합은 생성되지 않고 물리적으로 잘 혼합되었음을 알 수 있었다. 다만 GO와 고분자 간의 수소결합으로 낮은 주파수 방향으로 shift가 확인되었다는 특징을 보였다. TGA 분석 결과 PEBAX-GO 복합막과 PTMSP-GO 복합막의 온도 감량은 1단계로 일어났고 PEBAX-syn.GO 복합막의 온도 감량은 3단계로 나타났으며, 세 복합막 모두 GO의 함량이 증가할수록 열적안정성은 전반적으로 향상되었다. SEM 분석 결과, PEBAX-GO 복합막은 GO의 함량의 증가함에 따라 PEBAX 내 작용기와 GO 작용기의 친화성으로 막 구조 내에서 조밀한 구성을 보였고, PTMSP-GO 복합막은 PEBAX와는 다르게 GO와의 친화성을 보이는 작용기를 가지지 않아 GO 함량이 커지면서 PTMSP와 GO 사이에 공극이 관찰되었다. PEBAX-syn.GO 복합막의 단면은 층층이 배열된 조직을 가져 PEBAX-GO 복합막에 비교하였을 때, 그 구조가 다름을 알 수 있었다. XRD 분석 결과를 토대로 Graphite, GO, syn.GO의 층간거리를 Bragg’s equation을 통해 도출한 결과 각각 3.34 Å, 3.35 Å, 10.53 Å임을 확인하였다. 기체투과실험결과, PEBAX-GO 복합막은 CO2에 대한 기체투과도 값이 가장 컸으며 N2, CH4, CO2는 GO 함량이 증가함에 따라 기체투과도 값은 감소하였다. 반면 H2의 기체투과도 값은 특히 GO 30 wt%에서 21.43 barrer로 단일막에 비하여 약 5배가 증가하였고 이는 GO 층간 공간이 투과경로로 사용되었기 때문에 확산도가 커졌기 때문인 것으로 생각한다. 선택도(H2/N2)와 선택도(H2/CH4)의 증가는 확산선택도 증가영향을 기인한 것으로 생각하고 선택도(CO2/N2)와 선택도(CO2/CH4) 또한 증가하는 경향을 보여 기체분리성능이 향상됨을 알 수 있었다. PTMSP-GO 복합막의 기체투과결과는 N2<H2<CH4<CO2 순으로 높은 기체투과도 값을 가졌다. N2, H2, CH4의 기체투과 경향은 0 ∼ 10 wt% 범위에서 감소하다가 10 ∼ 30 wt% 범위에서 증가하였고, CO2는 0 ∼ 20 wt%에서 기체투과도가 감소하다가 그 이후의 함량에서는 증가하는 현상을 보였는데 여기서 기체투과도의 감소는 GO의 첨가가 filler로 작용하여 PTMSP의 자유부피가 감소하여 그 구조가 변하기 때문이고 이후의 기체투과도 증가는 PTMSP와 GO의 친화성이 낮아 계면에 공극이 생기기 때문인 것으로 생각된다. 기체투과도에 대한 선택도(H2/N2), 선택도(H2/CH4), 선택도(CO2/N2), 선택도(CO2/CH4)는 전반적으로 PTMSP-GO 10 wt% 복합막은 투과도가 감소하였으나 선택도는 증가하였고, PTMSP-GO 20 wt% 복합막은 투과도와 선택도 모두 감소하였다. PTMSP-GO 30 wt% 복합막은 투과도 향상의 폭이 컸으며 이에 따른 선택도는 감소하였으나 단일막에 비하여 Robeson upper bound 기준에 근접하여 기체투과성능이 다소 증가함을 보였다. PEBAX-syn.GO 복합막의 기체투과는 N2와 CO2 기체에 대하여 실행하였고, 각각 그 값은 함량 1 wt%, 10 wt%, 20 wt%, 30 wt% syn.GO에서 CO2기체는 83.2, 72.4, 58.9, 10.62 barrer로 감소하였고 N2기체는 약간 감소하였다. syn.GO 함량에 따른 기체투과도 값의 감소는 XRD 측정 결과 syn.GO의 넓은 층간 공간을 기체투과 경로로 사용하여 확산도의 증가를 인한 투과도 증가를 예상했던 바와 달리 syn.GO가 막 제조 시 기체투과방향에 대하여 수직으로 배열되어 예상 확산경로가 차단되었고 GO 표면의 배리어 특성이 주요한 영향으로 작용되었기 때문인 것으로 생각된다. Keyword: PEBAX, PTMSP, GO, polymer nanocomposite membrane, gas separation

기능화된 GO 함량에 따른 수지상 폴리(아릴렌 이써 설폰)과 폴리(페닐렌 옥사이드)를 포함하는 복합 막의 합성 및 특성 분석

김현진 전북대학교 일반대학원 2022 국내석사

Fuel cell is a energy conversion device that converts chemical energy into electrochemical energy, and is receiving a lot of attention as a very efficient device with low greenhouse gas emission. In particulary, anion exchange membrane fuel cell(AEMFC) have been developed as a alternative to proton exchange membrane fuel cells(PEMFCs) owing to high energy efficiency and usage of non-platinum catalyst. In this study, composite membranes were prepared for 5 species with various content of functionalized GO(GO-Im) to investigate electrochemical performance and physical/chemical properties of AEM. First, branched poly(arylene ether sulfone)(BPAES) and poly(phenylene oxide)(PPO) were synthesized, followed by the chloromethylation reaction proceeded. After mixing two synthesized polymers, GO-Im was added in various content to prepare a composite membranes. The chemical structure of the polymers used for blending was confirmed through 1H-NMR and FT-IR, and the degree of chloromethylation of CM-BPAES and CM-PPO was confirmed to be about 4-50%. Subsequently, the successful functionalization of GO nanosheets was achieved through hydrolysis and substitution reaction using (3-chloropropyl)trimethoxysliane(CTMS) and 1-methylimidazole. XPS and FT-IR analysis proved introduction of functional group into GO nanosheets. Additionally, introduced functional groups were confirmed through FE-SEM and EDS mapping. The thermal properties of the prepared membranes were confirmed by TGA and DSC. Water uptake, swelling ratio, and ion exchange capacity(IEC) were performed to characterize membranes. Overall, when the GO-Im content increased, the ionic conductivity tended to increase, but the excessive introduction of GO-Im reduced the number of ion conducting channels due to aggregation, confirming that the ionic conductivity was low. This indicates that the introduction of an appropriate amonunt of inorganic material is essential for the electrochemical performance. The QBPAES/PPO-GO-Im-0.9wt% composite membrane had a high water uptake and suitable dimensional stability, and achieved a high ionic conductivity of 116 mS cm-1 at 90 ℃. As a result, the prepared composite membrane have an excellent potential as an AEM for AEMFC.

신경분화과정에서 Go와 Rit의 역활 규명

김승현 경기대학교 2006 국내석사

Heterotrimeric GTP binding proteins (G proteins) transduce signals initiated by a variety of hormones and neurotransmitters. Among G proteins, Go is one of the most abundant G proteins expressed in the brain and is classified as a member of the Gi/Go family due to its sequence homology to Gi proteins. To determine the function of the alpha subunit of Go in brain, We searched for Goα-interacting partners from human fetal cDNA library using yeast two hybrid screening. We identified a cDNA encoding 219 amino acids of Ras like protein in all tissue (Rit). We confirmed Goα::Rit interaction employing several biochemical analysis. Rit also preferentially bind the GoαQ205L, constitutively active form of Goα than wild type Goα. To determine the effects of Goα::Rit interaction on neuronal differentiation, we transfected expression vector for Goα or/and RitDN, dominant negative form of Rit. While the expression of GoαQ205L alone induced neurite outgrowth, coexpression of GoαQ205L and RitDN did not show such effect. To investigate the downstream signaling of Rit in neuronal differentiation, we search Ral-stat3 and ERK pathway. As results, Rit could not activate Ral-stat3 pathway and rather stimulated ERK phosphorylation. ERK phospholyrlation was increased by expression of GoαQ205L but decreased by coexpression of GoαQ205L and RitDN. These results suggested that activation of Goα increase the function by Rit as a ERK-dependent neuronal differentiation inducer.

전자전달층의 GO와 ZrO2층 삽입에 따른 페로브스카이트 태양전지 물성 연구

이혜령 서울시립대학교 일반대학원 2020 국내석사

In this study, we investigated electron transport layer (ETL) engineering of perovskite solar cell (PSC) by adding graphene oxide (GO) into TiO2 and inserting ZrO2 layer on the TiO2 layer. Solar simulator and potenetist were used to confirm photovoltaic properties and interfaces resistance of PSC. External quantum efficiency was analyzed by incident photon-to-current efficiency (IPCE). Field emission scanning electron microscopy (FE-SEM) and atomic forced microscopy (AFM) were used for microstructure. Electron probe X-ray microanalyzer (EPMA) was used to analyze cross section component of PSC. Also, ultraviolet-visible-near infrared (UV-VIS-NIR) spectroscopy was used to analyze transmittance of ETL. First, we fabricated glass/FTO/B.L-TiO2/meso-TiO2+GO/perovskite/HTL/Au electrode structure perovskite solar cell. Here, various contents of GO (0.0, 0.3, 0.5 and 0.7wt %) added to the TiO2 solution. The results of the photovoltaic properties indicated in energy conversion efficiency (ECE) were measured 12.70, 13.13, 14.19 and 12.63%, respectively according to 0.0, 0.3, 0.5, and 0.7wt % GO contents. In particular, the best ECE was observed at mixing 0.5wt % GO, but after mixing 0.7wt % GO, ECE decreased. The ECE changed since short circuit current density (Jsc) and shunt resistance increased by added low-resistance GO into TiO2. However, result of microstructure analysis, 0.5wt % GO caused increase RMS of ETL, facilitating perovskite nucleation site formation increase perovskite crystal size. The size of perovskite crystal decreased at 0.7wt % GO due to the reduced RMS of ETL, because of this reduced Jsc and ECE. And excessive amount of GO decreased Jsc by reduction ETL transmittance, which consequently caused a decrease in ECE. So, appropriate amount of GO into TiO2 layer might improve the ECE of PSC. Second, we fabricated glass/FTO/B.L-TiO2/meso-TiO2/ZrO2/perovskite/HTL/Au electrode structure perovskite solar cell by adding different ZrO2 layer (168, 204, 242, 288nm) on the top of TiO2 layer. The TiO2/ZrO2 layer thickness were measured as 264/0, 228/168, 228/204, 270/242 and 282/288nm, respectively, it was confirmed that EPMA. The results of the photovoltaic properties indicated in Jsc were observed at 19.56, 21.15, 20.07 and 19.75mA/cm2, according to different thickness of ZrO2 layer. The best Jsc was observed at 204nm ZrO2 layer, but after 242nm ZrO2 layer, Jsc decreased. The analysis of IPCE, confirmed that the ration of incident wavelength to PSC and collected by carriers on PSC was consistent. Particularly, the highest Jsc was confirmed at 204nm ZrO2 layer in PSC. It was shown by impedance analysis that there was a decrease of the interface resistance between the perovskite layer and ZrO2 layer, which has high electrical conductivity. Result of microstructure analysis, the perovskite crystal size and thickness were changed according to different ZrO2 layer thickness. Especially, 204nm ZrO2 layer affected the upper perovskite layer that increasing perovskite grain size and capping layer, then an increasing in ECE. However, As the increasing thickness of ZrO2 layer, perovskite layer thickness decreased. Also, decreasing transmittance, it was caused decreasing light reach to perovskite layer, it is reducing Jsc, then reducing ECE of PSC. Thus, we confirmed that the appropriate GO contents and ZrO2 layer into TiO2 layer, improve Jsc and ECE, compared with the PSC employing only TiO2. 본 연구에서는 페로브스카이트 태양전지(perovskite solar cell ; PSC)의 전자전달층(electron transport layer ; ETL)으로 사용되는 TiO2에 graphene oxide(GO)를 혼합하고, TiO2층 위에 ZrO2층을 삽입하여 이를 채용한 PSC 소자의 물성을 확인하였다. PSC 소자의 광전기적 특성과 impedance를 확인하기 위해 solar simulator와 potentiostat를 이용하였으며, 외부양자효율 확인은 incident photon-to-current efficiency(IPCE)를 이용하였다. 미세구조 분석은 field emission scanning electron microscopy과 atomic forced microscopy을 이용하였으며, 소자의 단면 성분 분석을 위해 electron probe X-ray microanalyzer(EPMA)를 사용하였다. 또한 ETL의 투과도를 분석하기 위해 ultraviolet-visible-near-infrared을 이용하였다. 첫 번째로, TiO2 용액에 0.0, 0.3, 0.5, 0.7wt %의 GO 수용액을 혼합하여 glass/FTO/B.L-TiO2/meso-TiO2+GO/perovskite/HTL/Au electrode 구조의 PSC 소자를 제작하였다. 광전기적 특성 결과, GO 혼합 양에 따른 PSC 소자의 에너지변환효율(energy conversion efficiency ; ECE)은 각각 12.70, 13.13, 14.19, 12.63%로, 점차 증가하다가 감소하는 경향을 보였다. 특히 0.5wt % GO 소자의 ECE 값이 가장 우수하였으며, 0.7wt % GO 소자의 ECE 값이 감소하였다. 이러한 ECE 변화는 TiO2에 저항이 낮은 GO를 혼합하여 소자의 단락전류밀도(short circuit current density ; Jsc)와 션트 저항을 향상시켜 ECE 값이 증가하였다. 미세구조 분석 결과, TiO2의 GO 혼합은 ETL의 RMS 값을 증가시켜, 상부 페로브스카이트 핵생성 사이트를 용이하게 형성시켰다. 이를 통해 페로브스카이트 결정립 크기 증가로, ECE 값이 증가하였다. 그러나 과도한 양의 GO 혼합은 ETL의 RMS를 감소시켰으며, 이는 페로브스카이트 결정립 크기 감소로 소자의 ECE 값을 저하시켰다. 또한 과도한 양의 GO 혼합은 ETL의 투과도를 감소시켜 Jsc가 감소하였으며, 이는 ECE 감소의 원인이 되었다. 따라서 TiO2의 0.5wt % GO 혼합은 PSC 소자의 ECE를 향상시킬 수 있었다. 두 번째로, TiO2층 위에 168, 204, 242, 288nm의 ZrO2층을 삽입하여 glass/FTO/B.L-TiO2/meso-TiO2/ZrO2/perovskite/HTL/Au electrode 구조의 PSC 소자를 제작하였다. TiO2/ZrO2층의 두께는 EPMA 분석을 통해 각각 264/0, 228/168, 228/204, 270/242, 282/288nm로 형성됨을 확인하였다. 광전기적 특성 결과, ZrO2층 두께에 따른 Jsc는 각각 19.56, 21.15, 20.07, 19.75mA/cm2로, 증가하다가 감소하는 경향을 확인하였다. 이는 IPCE 분석을 통해 소자에 입사한 파장 대비 수집된 캐리어 비율이 일치하는 것을 확인하였으며, 특히 204nm ZrO2를 채용한 소자의 Jsc가 가장 우수함을 확인하였다. 이는 impedance 분석을 통해 전도도(conductivity)가 우수한 ZrO2를 ETL로 사용하여 ETL/페로브스카이트 층간의 계면 저항이 감소하여 나타난 결과임을 확인하였다. 미세구조 분석 결과, ZrO2층 두께에 따라 페로브스카이트 결정립 크기 및 층 두께가 변화하였으며, 특히 204nm ZrO2는 우수한 페로브스카이트 층을 형성시켜 소자의 ECE 값이 증가하였다. 반면에 ZrO2층의 두께가 두꺼워지면 페로브스카이트 층 두께 감소 및 ETL의 투과도 감소로 Jsc가 감소하였으며, 이는 소자의 ECE를 감소시켰다. 따라서 기존 TiO2만을 ETL로 채용한 소자와 비교하여 ETL에 적절한 양의 GO 혼합 및 적절한 두께의 ZrO2층 삽입은 Jsc와 ECE 값을 향상시킬 수 있었다.

연결된 그래핀과 이를 이용한 고분자 나노복합재료의 제조와 특성 : Preparation and characterization of the stitched graphene and its polymer nanocomposites

김남훈 전북대학교 일반대학원 2013 국내박사

A simple, efficient and cost-effective approach for the simultaneous reduction, surface modification and stitching of graphene oxide (GO) using ethylenediamine is described. The effects of stitched graphene on the mechanical properties of linear low density polyethylene (LLDPE)-based composites were investigated. The microstructures were analyzed by Atomic Force Microscopy (AFM) and Transmission Electron Microscopy (TEM) revealing stitching and crystalline behavior of the reduced graphene oxide (RGO). The storage modulus of the ethylenediamine functionalized GO (3 wt.%)/LLDPE composites are significantly higher than that of pure LLDPE or ethylamine functionalized GO/LLDPE composites in the temperature range studied (from -70 to 90 oC). The results suggest that the reduction of GO with ethylenediamine is a promising route for large-scale production of RGO. In order to find an eco-friendly, cost effective reduction method, Tin (Sn) powder also was used to reduce GO (SR-GO). Reduction has been carried out for various processing time from 0.5 to 3 h both at room temperature (RT) and at 50 oC using Sn powder and hydrochloric acid to study the reduction states and resulting SR-GO structure with time. The level of reduction of GO increases with increasing reduction time as evidenced from electrical conductivity study and XPS analysis. The electrical conductivity of the SR-GO will be influenced by the reduction rate of SR-GO and the amount of Sn powder remained. The presence of Sn particles in SR-GO obtained at room temperature causes to increase its electrical conductivity. XPS elemental analysis shows a good agreement with this observation. In order to study electrochemical performances of SR-GO, cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy analysis were performed. A maximum specific capacitance of 110 F g-1 at a current density of 2 A g-1 has been recorded for SR-GO prepared at 50 ◦C for 3 h. The results conclude that Sn powder can be used to reduce GO effectively and the optimal condition for the reduction process are 50 oC and 3 h in the tested range In order to prepare high performance nanocomposites, 3-D nanostructures using rGO and multi-walled carbon nanotubes (MWNTs) were synthesized. The thionyl chloride (SOCl2) treated MWNTs are attached to the surface of stitched rGO previously. The surface of stitched rGO still has some unreacted -NH2 groups and they allow -Cl terminated MWNTs to attach on the surface. Using resulting 3-D nanostructures, rGO-MWNTs/LLDPE composite was prepared by solution mixing and its mechanical properties were investigated. The structural features of rGO-MWNTs nanostructures were chracterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Field emission scanning electron microscopy was used to observe the morphology of the nanostructures. The thermal stabilities of the nanostructures have been evaluated using Thermogravimetric analysis (TGA). The tensile strength of rGO-MWNTs/LLDPE composites was much enhanced comparing to the neat LLDPE and single filler system. The improvement in tensile strength of the rGO-MWNTs/LLDPE composites is attributed to better interaction between 3-D nanostructured fillers and polymer matrix and better dispersion of fillers in the matrix.

Graphene Oxide Hole Injection Layer for Organic Light-Emitting Diodes by Using Electrophoretic Coating and Electrical Reduction

Kim, Jungyoon 고려대학교 그린스쿨대학원 2014 국내석사

Many researchers have interest in graphite family such as graphene oxide (GO), reduced graphene oxide (RGO) and Graphene. Among this graphite family, the GO has unique properties which are band gap, high dispersion force in water and high transmittance. These properties are very useful for making devices like Field Effect Transistor (FET), Organic Photovoltaic (OPV), and Organic Light-emitting Diodes (OLED). Since the band gap of GO is too large for these kind of devices, band gap engineering is an essential prerequisite. The band gap gradually narrowed down from GO to RGO, hence it is necessary to control band gap reduction as per requirement of the device. There are some methods for the Band gap engineering. The first one is a chemical method that uses toxic solutions such as hydrazine. Another is a physical method that needs high temperature about 1000℃. Both methods are very toxic, dangerous and inefficient methods. So we have studied about electrical method to reduce GO. Also the fabrication of GO thin film is important issue for adapting GO to devices. Traditionally spin-coating method was used to fabrication GO thin film. The spin-coating method is valuable method. The difficulties in spin coating method are thickness control and limitation of the coated area. Electrophoretic deposition (EPD) method solves the problems which are related with Band gap engineering (reduction) and fabrication (deposition) of the GO thin film. Both phenomena are happened at the same time and respective electrode. On applying voltage reduction of GO occurs at cathode while deposition of GO occurs at anode. Using these phenomena we can get GO film at the anode. Then deposited GO film moved to the cathode position for reduction. We can regulate not only the thickness of GO film by controlling the deposition time but also band gap of GO by controlling the reduction time. Since GO can only be deposited on conductive material, we can deposit GO on ITO that is used as electrode of device. The thin films that coated at the anode and reduced at the cathode have various properties, it is important to clarify the distinctions for adapting to device. These properties of GO and RGO thin films coated by EPD method are demonstrated by Raman spectroscopy, Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (SEM), X-ray Photoelectron spectroscopy (XPS) and transmittance. Finally, we adopt the GO thin film to OLED device as a Hole Injection Layer (HIL) and demonstrated increasing performance of the OLED device. Taken all together, we consider that EPD is simple and useful method for fabricating GO thin film and OLED device.