• Journal of Pharmaceutical Investigation
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• 제31권1호
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• pp.7-12
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• 2001

Amphotericin B (AmB) is a drug of choice for the treatment of systemic fungal diseases, but its use is considerably limited due to a high incidence of toxicity, particularly nephrotoxicity. It has been demonstrated that the toxicity of AmB is caused by self-aggregated species of the drug and that unaggregated (monomeric) drug is nontoxic but still expresses antifungal activity. Poly (ethylene oxide) (PEO) is a water-soluble polymer, which may impact the aggregation state of AmB. We have studied the aggregation state of AmB as a function of PEO molecular weight and concentration. At 3,000 and 8,000 g/mole, there was minimal or no change of critical aggregation concentration (CAC) of AmB regardless of the concentration of polymer. By contrast at 20,000 g/mole, the CAC of AmB strikingly increased to 24.3 and $37.5\;{\mu}M$ at 5.0% and 10 % w/v of polymer, respectively. The critical overlap concentration (COC) of PEO 20,000 g/mole was 5.5%. It appears that an interaction between monomeric AmB and polymer coil increases above the COC, competing with self-aggregation of the drug. Accordingly, the degree of aggregation of AmB stayed low and the toxicity became less. There was no such effect at 3,000 and 8,000 g/mole of PEO, owing perhaps to small dimensions in comparison to AmB. Based upon these findings, less toxic AmB formulation may be developed by a pharmaceutical technique such as solid dispersion system containing both AmB and PEO 20,000 g/mole.

• 한국수산과학회지
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• 제29권1호
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• pp.92-96
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• 1996

CM-chitin의 고유특성 및 유동특성을 밝혀 효과적으로 식품산업에 이용하기 위하여 CM-chitin 수용액의 유동특성 중 임계농도와 유동방정식을 조사하였다. 물에서 CM-chitin의 환원농도는 2.5이었으며, 이 때의 임계농도는 $0.8\%(w/v)$이었다. 즉 $0.8\%$ 이하의 농도에서는 분자사슬간 상호작용이 일어나지 않았으며, $0.8\%$ 이상에서 상호작용이 일어나는 것으로 나타났다. $0.5\%$ CM-chitin 용액은 전단속도가 증가하여도 점도는 일정하게 유지되는 뉴우튼 유체의 특성을 보였으며, $1.0\%$ 용액은 전단속도가 증가하면 점도가 낮아지는 의가소성 유체의 특성을 보였다. $3.0\%$ CM-chitin 수용액의 유동상수 $\eta_\infty,\;\eta_0,\;\beta$, n은 각각 $0.0908(\fallingdotseq0.1)cp$, 770cp, 0.81, 0.36이었다. 따라서 $3.0\%$ CM-chitin 수용액의 유동방정식은 $\eta=0.1+\{{770/(1+0.81D^{0.36})\}$으로 나타낼 수 있다.

• 한국물환경학회지
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• 제34권3호
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• pp.270-284
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• 2018

Paldang is a river reservoir located in the Midwest of Korea, with a water volume of $244{\cdot}10^6m^3$ and a water surface area of $36.5km^2$. It has eutrophied since the construction of a dam at the end of 1973, and the phosphorus concentration has decreased since 2001. Average hydraulic residence time of the Paldang reservoir is about 10 days during the spring season and 5.6 days as an annual level. The hydraulics and water quality of the reservoir can differ greatly, both temporally and spatially. For the spring period (March to May) in 2001 ~ 2017, the reservoir mean total phosphorus concentration calculated from the budget model based on a plug-flow system (PF) and a continuous stirred-tank reaction system (CSTR) was 13 % higher and 10 % lower than the observed concentration, respectively. A composite flow system (CF) was devised by assuming that the transition zone was plug flow, and that the lacustrine zone was completely mixed. The mean concentration calculated from the model based on CF was not skewed from the observed concentration, and showed just 6 % error. The retention coefficient of the phosphorus derived from the CF was 0.30, which was less than those of the natural lakes abroad or river reservoirs in Korea. The apparent settling velocity of total phosphorus was estimated to be $93m\;yr^{-1}$, which was 6 ~ 9 times higher than those of foreign natural lakes. Assuming CF, the critical load line for the total phosphorus concentration showed a hyperbolic relation to the hydraulic load in the Paldang reservoir. This is different from the previously known straight critical load line. The trophic state of the Paldang reservoir has recently been estimated to be mesotrophic based on the critical-load curve of the phosphorus budget model developed in this study. Although there is no theoretical error in the newly developed budget model, it is necessary to verify the validity of the portion below the inflection point of the critical-load curve afterwards.

• Bulletin of the Korean Chemical Society
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• 제30권9호
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• pp.2001-2006
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• 2009

Temperature dependence of the critical micelle concentration (CMC), $x_{CMC}$, in micellization can be described by ln $x_{CMC}$ = A + BT + C lnT + D/T, which has been derived statistical-mechanically. Here A, B, C, and D are fitting parameters. The equation fits the CMC data better than conventionally used polynomial equations of temperature. Moreover, it yields the unique(exponent) value of 2 when the CMC is expressed in a power-law form. This finding is quite significant, because it may point to the universality of the thermal behavior of CMC. Hence, in this article, the nature of the equation ln $x_{CMC}$ = A + BT + C lnT + D/T is examined from a lattice-theory point of view through the Flory-Huggins model. It is found that a linear behavior of heat capacity change of micellization is responsible for the CMC equation of temperature.

• 해양환경안전학회지
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• 제13권4호
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• pp.51-54
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• 2007

화장품과 유처리제 등에 응용할 수 있는 계면활성제인 hexadecyl pyridinium bromide를 사용하여 온도 $40{\sim}60^{\circ}C$ 범위에서 임계미셀농도를 적하법으로 측정한 결과를 이용하여 미셀형성에 따른 열역학적 양을 다항식으로 계산하였다.

• 한국응용과학기술학회지
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• 제30권3호
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• pp.380-386
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• 2013

N,N,N-Trimethyl-10-nitrophenoxy decylammonium bromide (N10TAB) and N,N,N,N-Tetramethyl-bis-[10-nitrophenoxy decyl]-1,6-hexanediammonium dibromide (N10-6-10N), bearing aromatic nitrophenoxy group in the end of their hydrophobic chains have been prepared, and their properties in aqueous solutions have been studied by conductivity and H-NMR spectroscopy. Below the critical micelle concentration N10-6-10N form premicelle with two or three surfactant molecules. Beyond the critical micelle concentration two molecules have strong self-aggregation ability and form micelles of rather small size and with small aggregation numbers. H-NMR at different concentrations give the informations on the environmental changes of the surfactants on their micellization progress.

• 한국응용과학기술학회지
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• 제28권4호
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• pp.449-454
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• 2011

This surfactant can be used as a cosmetics and chemical dispersants. The variation of critical micelle concentration(CMC) with temperature for N-eicosyl pyridinium bromide over the range $40^{\circ}C$ to $60^{\circ}C$ has been measured by drop methods. Thermodynamic quantities for micellization of N-eicosyl pyridinium bromide in water have been calculated by polynominal equation.

• 해양환경안전학회지
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• 제14권2호
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• pp.145-148
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• 2008

화장품과 유처리제 등에 응용할 수 있는 양이온 계면활성제인 N-octadecyl pyridinium bromide를 사용하여 온도 $40{\sim}60^{\circ}C$ 범위에서 적하법을 이용한 임계미셀농도를 적용 미셀형성에 따른 열역학적 특성(자유에너지, 엔탈피, 엔트로피, 열용량)을 조사하였다. 그 결과 자유에너지 변화는 온도가 증가함에 따라 감소함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제24권10호
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• pp.1449-1454
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• 2003

A new equation has been derived on the basis of ${\delta}G^o$ = -RT lnK, linear behavior of the enthalpy of micellization with temperature, and the Gibbs-Helmholtz relation. It describes correctly the dependence of critical micelle concentration $(X_{CMC})$ on temperature and has yielded excellent fitting results for various surfactant systems. The new equation results in the linear behavior of the entropy of micellization with temperature and accounts for the compensation phenomena observed for the micellization in aqueous solutions, along with the linear dependence of the enthalpy of micellization on temperature. These results imply that the new equation of $X_{CMC}(T)$ accounts for the temperature dependence of CMC correctly.

• Archives of Pharmacal Research
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• 제15권2호
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• pp.126-129
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• 1992

The critical micelle concentrations (CMCs) of aqueous solutions of a nonionic surfactant, polyoxyl 23 lauryl ether in the presence of various concentration of urea and its derivatives were measured. The CMC of the surfactant increase in proportion to the concentration of the additives, and the CMC-raising activities increased with more and longer alkyl grups substituted in urea. The CMC shift values were successfully correlated with the cloud point shift values and the protein-denaturing activities of the additives, respectively. These results suggest that the micelle formation, clouding of the surfactant and the protein denaturation are a closely related phenomenon, and a common mechanism is operating which might be the hydrophobic interaction.