• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1539-1544
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• 2008

A polymeric micelle, based on the poly(benzyl-L-histidine)-b-poly(ethylene glycol) (polyBz-His-b-PEG) diblock copolymer, was designed as a tumor-specific targeting carrier. The micelles (particle size: 67-80 nm, critical micelle concentration (CMC); 2-3 $\mu$g/mL) were formed from the diafilteration method at pH 7.4, as a result of self-assembly of the polyBz-His block at the core and PEG block on the shell. Removing benzyl (Bz) group from polyBz-His block provided pH-sensitivity of the micellar core; the micelles were physically destabilized in the pH range of pH 7.4-5.5, depending on the content of the His group free from Bz group. The ionization of His group at a slightly acidic pH promoted the deformation of the interior core. These pHdependent physical changes of the micelles provide the mechanism for pH-triggering anticancer drug (e.g., doxorubicin: DOX) release from the micelle in response to the tumor’s extracellular pH range (pH 7.2-6.5).

• 한국가스학회지
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• 제12권4호
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• pp.52-57
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• 2008

본 연구는 pH환경 중에서 고주파 열처리한 강인주철의 마멸 부식거동을 pH환경 중에서의 접촉압력에 따른 마멸부식거동, 침지 부식 후 부식마멸거동 및 전기화학적 부식거동에 대해 고찰하였다. 응축수의 pH가 낮아질수록 마멸부식율은 급격히 증가하고, 전기화학적 양극분극에 의한 강인주철의 부식양상은 중성에서 가늘고 긴 흑연의 편상조직이 나타나지만, 강산성 중에서는 흑연이탈 현상으로 표면이 거칠게 나타난다.

• 대한의생명과학회지
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• 제13권3호
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• pp.197-206
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• 2007

P2X receptors are membrane-bound ion channels that conduct $Na^+,\;K^+$, and $Ca^{2+}$ in response to ATP and its analogs. There are seven subunits identified so far ($P2X_1-P2X_7$). $P2X_2$ receptors are known to be expressed in a wide range of organs including brains and adrenal grands. PC12 cells are originated from adrenal grand and differentiated by nerve growth factor or pituitary adenylate cyclase activating poly peptide (PACAP). Previous studies indicate that $P2X_2$ receptor activation in PC12 cells couples to $Ca^{2+}-dependent$ release of catecholamine and ATP. It is known that acidic pH potentiates ATP currents at $P2X_2$ receptors. This leads to a hypothesis that $P2X_2$ receptors may play an important role in PC12 cell differentiation, one of the characteristics of which is neurite outgrowth, induced by the hormones under lower pH. In the present study, we isolated several clones which potentiate neurite outgrowth by PACAP in acidic pH (6.8), but not in alkaline pH (7.6). RT-PCR and electrophysiology data indicate that these clones express only functional $P2X_2$ receptors in the absence or presence of PACAP for 3 days. Potentiation of neurite outgrowth resulted from PACAP (100 nM) in acidic pH is inhibited by the two P2X receptor antagonists, suramin and PPADS ($100\;{\mu}M)$ each), and exogenous exprerssion of ATP-binding mutant $P2X_2$ receptor subunit ($P2X_2[K69A]$). However, acid sensing ion channels (ASICs) are not involved in PACAP-induced neurite outgrowth potentiation in lower pH since treatments of an inhibitor of ASICs, amyloride ($10\;{\mu}M$), did not give any effects to neurite extension. The vesicular proton pump ($H^+-ATPase$) inhibitor, bafilomycin (100 nM), reduced neurite extension indicating that ATP release resulted from $P2X_2$ receptor activation in PC12 cells is needed for neurite outgrowth. These were confirmed by activation of mitogen activated protein kinases, such as ERKs and p38. These results suggest roles of ATP and $P2X_2$ receptors in hormone-induced cell differentiation or neuronal synaptogenesis in local acidic environments.

• Journal of Microbiology and Biotechnology
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• 제23권10호
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• pp.1454-1459
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• 2013

The changes in prodiginines productions caused by pH shock culture of Streptomyces coelicolor strains were estimated. In Streptomyces coelicolor M511, undecylprodiginine and streptorubin B productions increased 1.8-fold (37.22 mg/g) and 2.5-fold (18.61 mg/g), respectively, by pH shock (from 7.2 to 4.0). In contrast, this resulted in the significantly decreased prodigignines production in the redP deletion mutant SJM1; 3.7-fold for undecylprodiginine, 4.4-fold for streptorubin B, 5.2-fold for methylundecylprodiginine, and 6.4-fold for methyldodecylundecylprodiginine, respectively. RT-PCR analyses showed that, during pH shock, expression of redD, the transcription activator gene, was increased while the expression of fabH, the decarboxylative condensation enzyme gene in fatty acid biosynthesis, was decreased in both strains. The enhanced redD expression was in good accordance with the increased total prodiginines production of M511. However, for SJM1 mutant, the decrease of fabH expression occurred more strikingly, such that it became almost completely turned off during acidic pH shock culture. Therefore, a down-regulation of fabH was considered to be the cause of decreased amount of total prodiginines produced, although redD expression was high in SJM1 mutant.

• 대한화학회지
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• 제64권2호
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• pp.74-78
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• 2020

산성 영역에서 작동하는 고감도 형광 pH 센서막을 제조하기 위하여 실란화된 유리 표면 상에 push-pull 공액 염료(DCMP)를 공유결합에 의해 고정화하였다. DCMP 유도체(DCMA), 2-hydroxyethyl methacrylate (HEMA)및 triethylene glycol dimethacrylate의 혼합물을 광개시 공중합하여 pH 감응성 형광센서막을 제조하였다. 분광학적 측정 결과, pH 2.0-5.0 사이에서 pH가 증가함에 따라 센서막의 흡광도가 증가하였으며, 같은 pH 범위에서 pH 증가에 따라 센서막의 형광 세기도 약 50배 정도 증가하였다. 산성 조건에서 pH 변화에 대한 센서막의 감응은 가역적이고 재현성이 우수하였다. 또한 센서막은 20-50초 사이의 비교적 짧은 감응 시간과 여러 금속이온 존재에서 수소 이온에 대해 높은 선택성을 나타내었다.

• 미생물학회지
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• 제38권1호
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• pp.54-56
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• 2002

Induction of laccase isozymes under acidic stresses were determined in Trametes versicolor, Pleurotus ostreatus and Ganoderma lucidum isolated in Korea, and in Lentinus squarrosulrs isolated in Thai. When cultures of these fungi were transferred to acidic liquid media (pH 3.0-4.0), the activities of secreted extralcellular laccases were increased 60% and 400% in T. versicolor and G. lucidum respectively. However, there was no such induction in L. squarrosulus or P. ostreatus. In L. squarrosulus, different laccase isozymes in the electrophoretic mobilities were induced under acidic conditions.

• Archives of Pharmacal Research
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• 제20권6호
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• pp.643-646
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• 1997

Thermal stability of a red pigment, carthamin, frm Carthamus tinctorius was investigated to explore possible applications as natural color additives for foods, cosmetics, and nutraceuticals. Degree of degradation reactions of carthamin at acidic, neutral and alkaline conditions were determined with UV/V is spectral measurements. Decomposition half lives of carthamin at 25.deg. C were 4.0 h, 5.1 h, and 12.5 h at pH 5.0, pH 7.0, and pH 12.0, respectively, indicating that carthamin is much more stable at alkaline pH than acidic or neutral conditions. The activation energies of carthamin at pH 5.0, pH 7.0, and pH 12.0 were 15.6, 15.7 and 16.8 kcal/mol, respectively.

• 생명과학회지
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• 제27권7호
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• pp.826-833
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• 2017

대기의 이산화탄소의 농도 증가는 해양산성화와 지구온난화를 유발하는 것으로 알려져 있다. 해마는 해양생태계 및 수산자원생물로서 중요한 종으로 알려져 있지만, 최근 해양산성화로 인하여 개체수가 감소되고 있는 실정이다. 따라서 본 연구에서는 멸종 위기 종인 복해마(Hippocampus kuda)에 미치는 생리적 영향을 조사하기 위해서 사육수의 산성조건인 pH 6.0, 6.5, 7.0 및 자연해수(pH 8.0)의 환경에서 복해마(H. kuda)를 15일 동안 사육 후 체내 조성 변화 및 항산화 효소 활성 변화에 대하여 조사를 실시하였다. 복해마(H. kuda)의 크기 및 성장은 대조군인 pH 8.0을 제외한 실험군에서는 pH가 저하함에 따라 감소하는 경향을 나타내었다. 체내 조성성분인 회분, 조지방 및 조단백 또한 pH 저하에 따라 농도의존적으로 감소하는 것이 관찰되었다. SOD, CAT 및 GSH와 같은 항산화 효소의 분석 결과, SOD활성의 경우, pH 저하에 따라 농도의존적으로 감소하지만, 이와 상반되게 CAT 및 GSH에서는 pH저하에 따라 활성이 농도의존적으로 증가하는 결과가 나타내었다. 이것은 복해마(H. kuda)가 사육수의 pH 저하에 따른 체내 항상성을 유지하는 과정 중 스트레스가 야기되어 에너지 대사가 손상된 것으로 추정된다. 항산화효소는 일반적으로 산성화 스트레스에 민감하게 작용하는데 본 연구에서도 사육수의 pH 변화에 따라 항산화 효소작용이 유의하게 변화하였다. 이러한 결과로 복해마(H. kuda)에 있어서 산성화 노출을 통한 생리학적 스트레스가 항산화 반응 및 체내 성분과 성장을 저해하는 것으로 여겨진다.

• 대한화학회지
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• 제12권3호
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• pp.106-113
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• 1968

여러 酸性溶媒 속에서 3,4-methylenedioxy-${\beta}$-nitrostyrene에 대한 n-butylmercaptan의 親核性 添加反應速度常數를 측정하여 넓은 pH범위에서 잘 맞는 反應速度式을 구하였다. 이 식에 의하면 pH3이하에서는 mercaptan분자가 첨가하며 pH6이상에서는 mercaptide ion이 첨가함을 알 수 있고 이 중간 pH범위에서 일어나는 복잡한 반응 메카니즘도 이 식에 의해 정량적으로 잘 설명할 수 있음을 알았다.

• The Korean Journal of Physiology and Pharmacology
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• 제12권4호
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• pp.177-183
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• 2008

The layers of keratinocytes form an acid mantle on the surface of the skin. Herein, we investigated the effects of acidic pH on the membrane current and $[Ca^{2+}]_c$ of human primary keratinocytes from foreskins and human keratinocyte cell line (HaCaT). Acidic extracellular pH ($pH_e{\leq}5.5$) activated outwardly rectifying $Cl^-$ current ($I_{Cl,pH}$) with slow kinetics of voltage-dependent activation. $I_{Cl,pH}$ was potently inhibited by an anion channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS, 73.5% inhibition at 1${\mu}$M). $I_{Cl,pH}$ became more sensitive to $pH_e$ by raising temperature from $24^{circ}C$ to $37^{circ}C$. HaCaT cells also expressed $Ca^{2+}$-activated $Cl^-$ current ($I_{Cl,Ca}$), and the amplitude of $I_{Cl,Ca}$ was increased by relatively weak acidic $pH_e$ (7.0 and 6.8). Interestingly, the acidic $pH_e$ (5.0) also induced a sharp increase in the intracellular [$Ca^{2+}$] (${\triangle}[Ca^{2+}]_{acid}$) of HaCaT cells. The ${\triangle}[Ca^{2+}]_{acid}$ was independent of extracellular $Ca^{2+}$, and was abolished by the pretreatment with PLC inhibitor, U73122. In primary human keratinocytes, 5 out of 28 tested cells showed ${\triangle}[Ca^{2+}]_{acid}$. In summary, we found $I_{Cl,pH}$ and ${\triangle}[Ca^{2+}]_{acid}$ in human keratinocytes, and these ionic signals might have implication in pathophysiological responses and differentiation of epidermal keratinocytes.