• Transactions on Electrical and Electronic Materials
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• 제11권4호
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• pp.190-193
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• 2010

This report covers an effective fabrication method of graphene nanoribbon for top-gated field effect transistors (FETs) utilizing electron beam lithography with a bi-layer resists (XR-1541/poly methtyl methacrylate) process. To improve the variation of the gating properties of FETs, the residues of an e beam resist on the graphene channel are successfully taken off through the combination of reactive ion etching and a lift-off process for the XR-1541 bi-layer. In order to identify the presence of graphene structures, atomic force microscopy measurement and Raman spectrum analysis are performed. We believe that the lift-off process with bi-layer resists could be a good solution to increase gate dielectric properties toward the high quality of graphene FETs.

• Applied Biological Chemistry
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• 제47권4호
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• pp.390-395
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• 2004

토마토 뿌리에 존재하는 이온채널의 특성을 조사하기 위하여, 마이크로솜을 분리하고 전기생리용 분석장치가 연결된 인공지질 이중막에 유입하였다. 그 결과 다섯 종류의 이온채널을 확인하였고, 이들 중 450 pS의 전기전도도를 갖는 비선택성 양이온채널을 가장 자주 관측하였다. 이 채널은 세 가지의 subconductance 상태를 보였으며, 이들의 전기전도도는 450, 257, 105 pS으로 측정되었다. 모든 subconductance 상태는 막전위 변화에 따른 전류변화가 직선적으로 나타났다. 채널의 활성은 양의 막전위에서 열림과 닫힘이 반복되는 전이상태를 보였지만, 음의 막전위에서는 평균 열림시간과 함께 열림확률도 증가하였다. 막전위 -40mV에서 측정한 채널의 열림확률은 0.83이었다. 이온선택성을 측정하기 위하여 지질막의 한쪽에만 50mM의 $K^+$ 또는 $Na^+$을 가하여 비대칭 이온조건을 만들었을 때, 두 경우 모두에서 전류역전전위는 동일하게 약 -l0mV 이동하였다. 이것은 450 pS채널이 $K^+$과 $Na^+$을 구별없이 통과시킴을 나타낸다. 중금속 이온들 중, $100\;{\mu}M$ 농도의 $La^{3+}$과 $Ba^{2+},\;Zn^{2+}$는 채널의 활성을 크게 저해하여 열림확률을 0.2 이하로 감소시켰다. 그러나, $Al^{3+}$과 $Cd^{2+}$은 활성을 약 20% 저해하였다. 흥미롭게도, 각각의 중금속 이온은 서로 다른 형태로 채널활성을 저해하였다. $La^{3+}$은 $500\;{\mu}M$ 농도에서 모든 subconductance 상태를 저해하였으나, $Zn^{2+}$는 1 mM의 농도에서도 105 pS의 subconductance 상태는 저해하지 않았다. 또한 $Cd^{2+}$은 음의 막전위에서도 채널의 열림을 long-opening상태에서 전이상태 열림으로 전환시켰다. 이러한 결과는 중금속 이온들이 채널단백질에 각각의 결합부위를 가질 수 있을 가능성을 의미하여, 식물 뿌리의 생리현상에서 450 pS 채널의 기능적 역할 뿐 만아니라 구조적 특징을 탐색할 수 있는 유용한 조절자나 탐색자로 이용될수 있음을 시사한다.

• International Journal of Oral Biology
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• 제47권3호
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• pp.33-40
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• 2022

Store-operated Ca²⁺ entry (SOCE) represents one of the major Ca²⁺ entry routes in non-excitable cells. It is involved in a variety of fundamental biological processes and the maintenance of Ca²⁺ homeostasis. The Ca²⁺ release-activated Ca²⁺ (CRAC) channel consists of stromal interaction molecule and Orai; however, the role and action of Homer proteins as an adaptor protein to SOCE-mediated Ca²⁺ signaling through the activation of CRAC channels in non-excitable cells still remain unknown. In the present study, we investigated the role of Homer2 in the process of Ca²⁺ signaling induced by the interaction between CRACs and Homer2 proteins in non-excitable cells. The response to Ca²⁺ entry by thapsigargin-mediated Ca²⁺ store depletion remarkably decreased in pancreatic acinar cells of Homer2^-/- mice, as compared to wild-type cells. It also showed critical differences in regulated patterns by the specific blockers of SOCE in pancreatic acinar cells of Homer2^-/- mice. The response to Ca²⁺ entry by the depletion in Ca²⁺ store markedly increased in the cellular overexpression of Orai1 and STIM1 as compared to the overexpression of Homer2 in cells; however, this response was remarkably inhibited by the overexpression of Orai1, STIM1, and Homer2. These results suggest that Homer2 has a critical role in the regulatory action of SOCE activity and the interactions between CRAC channels.

• The Korean Journal of Physiology and Pharmacology
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• 제21권2호
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• pp.259-265
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• 2017

Excessive influx and the subsequent rapid cytosolic elevation of $Ca^{2+}$ in neurons is the major cause to induce hyperexcitability and irreversible cell damage although it is an essential ion for cellular signalings. Therefore, most neurons exhibit several cellular mechanisms to homeostatically regulate cytosolic $Ca^{2+}$ level in normal as well as pathological conditions. Delayed rectifier $K^+$ channels ($I_{DR}$ channels) play a role to suppress membrane excitability by inducing $K^+$ outflow in various conditions, indicating their potential role in preventing pathogenic conditions and cell damage under $Ca^{2+}$-mediated excitotoxic conditions. In the present study, we electrophysiologically evaluated the response of $I_{DR}$ channels to hyperexcitable conditions induced by high $Ca^{2+}$ pretreatment (3.6 mM, for 24 hours) in cultured hippocampal neurons. In results, high $Ca^{2+}$-treatment significantly increased the amplitude of $I_{DR}$ without changes of gating kinetics. Nimodipine but not APV blocked $Ca^{2+}$-induced $I_{DR}$ enhancement, confirming that the change of $I_{DR}$ might be targeted by $Ca^{2+}$ influx through voltage-dependent $Ca^{2+}$ channels (VDCCs) rather than NMDA receptors (NMDARs). The VDCC-mediated $I_{DR}$ enhancement was not affected by either $Ca^{2+}$-induced $Ca^{2+}$ release (CICR) or small conductance $Ca^{2+}$-activated $K^+$ channels (SK channels). Furthermore, PP2 but not H89 completely abolished $I_{DR}$ enhancement under high $Ca^{2+}$ condition, indicating that the activation of Src family tyrosine kinases (SFKs) is required for $Ca^{2+}$-mediated $I_{DR}$ enhancement. Thus, SFKs may be sensitive to excessive $Ca^{2+}$ influx through VDCCs and enhance $I_{DR}$ to activate a neuroprotective mechanism against $Ca^{2+}$-mediated hyperexcitability in neurons.

• The Korean Journal of Physiology and Pharmacology
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• 제26권4호
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• pp.277-285
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• 2022

To investigate the adverse effects of clozapine on cardiovascular ion channels, we examined the inhibitory effect of clozapine on voltage-dependent K⁺ (Kv) channels in rabbit coronary arterial smooth muscle cells. Clozapine-induced inhibition of Kv channels occurred in a concentration-dependent manner with an half-inhibitory concentration value of 7.84 ± 4.86 µM and a Hill coefficient of 0.47 ± 0.06. Clozapine did not shift the steady-state activation or inactivation curves, suggesting that it inhibited Kv channels regardless of gating properties. Application of train pulses (1 and 2 Hz) progressively augmented the clozapine-induced inhibition of Kv channels in the presence of the drug. Furthermore, the recovery time constant from inactivation was increased in the presence of clozapine, suggesting that clozapine-induced inhibition of Kv channels is use (state)-dependent. Pretreatment of a Kv1.5 subtype inhibitor decreased the Kv current amplitudes, but additional application of clozapine did not further inhibit the Kv current. Pretreatment with Kv2.1 or Kv7 subtype inhibitors partially blocked the inhibitory effect of clozapine. Based on these results, we conclude that clozapine inhibits arterial Kv channels in a concentration-and use (state)-dependent manner. Kv1.5 is the major subtype involved in clozapine-induced inhibition of Kv channels, and Kv2.1 and Kv7 subtypes are partially involved.