• Molecules and Cells
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• 제26권1호
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• pp.87-92
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• 2008

We employed dual color Fluorescence Cross Correlation Spectroscopy (FCCS) to measure the interaction between PKA regulatory (RII) and catalytic subunits (CAT) in living cells. Elevation of intracellular cAMP with forskolin decreased the cross-correlation amplitude between RFP-fused RII (RII -mRFP) and GFP-fused CAT (CAT-EGFP) by 50%, indicating that cAMP elevation leads to dissociation of RII-CAT complexes. Moreover, diffusion coefficient analysis showed that the diffusion rate of CAT-EGFP was significantly increased, suggesting that the decreased RII-CAT association caused by cAMP generated free CAT subunits. Our study demonstrates that in vivo FCCS measurements and their quantitative analysis permit one not only to directly quantify protein-protein interactions but also to estimate changes in the intracellular cAMP concentration.

• Fibers and Polymers
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• 제1권2호
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• pp.92-96
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• 2000

A high molecular weight polyhydroxyamide (PHA) solution in N, N-dimethyl acetamide (DMAc) was prepared from 3, 3'-dihydroxybenzidine and isophthalic chloride (IPC), which was used for spinning PHA fiber. Before spinning, the diffusion property of DMAc into various coagulants was examined. The fiber was well formed in coagulants such as water/ethanol with a composition of 5/5, ethanol, and ethanol/isopropanol with a composition of 7/3 and 5/5. However, the PHA fiber spun in the water/ethanol mixture contained voids. After the fiber spun in ethanol was annealed at over $350^{\circ}C$, the ultimate stress and initial modulus of the fiber increased from 75.5 MPa and 3.22 GPa to 369 MPa and 29.5 GPa, respectively. These properties of the PHA fiber spun by the dry spinning method were also enhanced, attaining 154 MPa and 5.56 Gpa, respectivel.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제26권8호
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• pp.366-374
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• 2014

Experimental mass transfer data, which were obtained for the $CO_2$-water slug flows in vertical tubes with 2, 5, and 8mm diameters, were analyzed in comparison with the penetration theory. It was found that a penetration model with molecular diffusion coefficient cannot predict the experimental data accurately. An effective diffusion coefficient, which considers enhancement effect of interfacial waves, was suggested to improve prediction. Another empirical factor was also suggested to consider the effect of non-uniform interface velocity. A modified penetration model was found to be capable of predicting the experimental data reasonably well.

• Molecules and Cells
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• 제27권3호
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• pp.321-327
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• 2009

Voltage-dependent anion channels (VDACs) are reported to be porin-type, ${\beta}$-barrel diffusion pores. They are prominently localized in the outer mitochondrial membrane and are involved in metabolite exchange between the organelle and the cytosol. In this study, we have investigated a family of VDAC isoforms in Arabidopsis thaliana (AtVDAC). We have shown that the heterologous expression of AtVDAC proteins can functionally complement a yeast mutant lacking the endogenous mitochondrial VDAC gene. AtVDACs tagged with GFP were localized to mitochondria in both yeast and plant cells. We also looked at the response of AtVDACs to biotic and abiotic stresses and found that four AtVDAC transcripts were rapidly up-regulated in response to a bacterial pathogen.

• Journal of the Korean Magnetic Resonance Society
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• 제4권1호
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• pp.29-40
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• 2000

Coupled carbon-13 relaxation study of 1,1,1-trichloroethane dissolved in DMSO has been performed to gain some crucial insight into the dynamics of methyl group in this compound. For this purpose the relaxation behaviors of several observable magnetization modes for CH3 spin system generated by various perturbing pulse sequences have been carefully investigated and various dipolar spectral densities were estimated by nonlinear numerical fittings of the observed data with the relaxation curves, which were then employed to determine the three principal values for the diffusion tensor for end-over-end molecular rotation as well as internal rotational parameters of methyl group. In this process we could uniquely determine two correlation times $\tau$int(1) and $\tau$int(2) which give valuable information on internal rotor dynamics and thus obtained data were interpreted on the basis of various proposed models for internal rotation. compound undergoes three-fold jumps at 25$^{\circ}$. The fact that the ratio $\tau$int(1) / $\tau$int(2) is close to 1.0 may be interpreted as indicating that methyl group in this C.

• Proceedings of the Membrane Society of Korea Conference
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• 한국막학회 2003년도 The 4th Korea-Italy Workshop
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• pp.91-94
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• 2003

In this work, the physicochemical properties for permeant molecules and polyion complex membrane prepared by complexation between SA and chitosan were determined by using molecular modeling methods, and the permeation behaviors of water and alcohol molecules through the PIC membrane have been investigated. In the case of penetrant molecule, the experimental results showed that the prepared membrane was excellent pervaporation performance result in most solution, and the selectivity and permeability of the membrane were dependent on the molecular size, the polarity and the hydrophilic surface of permeant organics. However, the separation behavior of methanol aqueous solution exhibited other permeation tendency with other feed solutions and contradictory result. That is, the membrane were preferentially permeable to methanol over water despite water molecule has stronger polarity and small molecular size than methanol molecule. In this study, the results were discussed from the viewpoint of chemical and physical properties between permeant molecules and membrane in the diffusion state.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제35권6호
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• pp.325-331
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• 2022

Hydrogen embrittlement in metals has been a serious issue with regard to structural safety. In this study, molecular dynamics simulations revealed that the aggregation of hydrogen atoms at the crack tips suppresses the dislocation emission and thus results in cleavage fracture. A series of molecular dynamics simulations were performed considering factors such as the concentration of hydrogen atoms, loading rate, and diffusion coefficient. We investigated the conditions that minimize hydrogen embrittlement. The simulation results were consistent with the experimental results and used to quantify hydrogen embrittlement.

• Applied Chemistry for Engineering
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• 제10권6호
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• pp.876-880
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• 1999

The surfactant self-diffusion coefficients of mixed micellar solutions of ionic and nonionic surfactants have been measured by the NMR pulsed field gradient spin echo(FT-PGSE) method. In addition, the line widths of $^1H$ NMR signal have been monitored. The system investgated are $C_{12}EO_5/SDS/D_2O$, $C_{12}EO_5/DTAC/D_2O$, and $C_{12}EO_8/SDS/D_2O$. In the sample series, the molar ratios of $D_2O$ to surfactant(ionic+nonionic) were kept constant while the surfactant mixing ratio was varied. For the $C_{12}EO_5$ system, the surfactant self-diffusion coefficient indicates minimum when the surfactant mixing ratio is about 20% ionic surfactant. The observed decrease in self-diffusion coefficients as nonionic surfactant was replaced by ionic surfactant is interpreted to mainly be due to an increased micelle-micelle repulsion. The increase in self-diffusion coefficients occurring at higher fraction of ionic surfactant is shown to be due to a decrease in micelle size. For the $C_{12}EO_8$ system, the effect of the surfactant mixing ratio is much weaker which can be understood by considering the molecular geometry and large headgroup area. The proton NMR line widths correlate well with the self-diffusion coefficients and broadening of the alkyl chain methylene signals is found when the self-diffusion coefficients is low.

• Journal of Advanced Marine Engineering and Technology
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• 제39권6호
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• pp.662-669
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• 2015

There has been an increased interest in the mitigation of wax deposition because wax, which usually accumulates in subsea oil-production systems, interrupts stable oil production and significantly increases the cost. To guarantee a required oil flow by mitigating wax deposition, we need to obtain a reliable estimation of the wax deposition. In this research, we perform simulations to understand the major mechanisms that lead to wax deposition, namely molecular diffusion, shear stripping reduction, and aging. While the model variables (shear reduction multiplier, wax porosity, wax thermal conductivity, and molecular diffusion multiplier) can be measured experimentally, they have high uncertainty. We perform an analysis of these variables and the amount of water and gas in the multiphase flow to determine these effects on the behavior of wax deposition. Based on the results obtained during this study for a higher wax porosity and molecular diffusion multiplier, we were able to confirm the presence of thicker wax deposits. As the shear reduction multiplier decreased, the thickness of the wax deposits increased. As the amount of water increased, there was also an increase in the amount of wax deposits until 40% water cut and decreased. As the amount of gas increased, the amount of wax deposits increased because of the loss of the light hydrocarbon component in the liquid phase. The results of this study can be utilized to estimate the wax deposition behavior by comparing the experiment (or field) and simulation data.

• Membrane Journal
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• 제25권2호
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• pp.123-131
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• 2015

The PTMSP/PDMS graft copolymer were synthesized from the PTMSP[poly(1-trimethylsilyl-1-propyne)] and the PDMS[poly(dimethylsiloxane)] and then the PTMSP/PDMS-borosilicate composite membranes were prepared by adding the porous borosilicates to the PTMSP/PDMS graft copolymer. The number-average molecular weight (${\bar{M}}_n$) and the weight-average molecular weight (${\bar{M}}_w$) of PTMSP/PDMS graft copolymer were 460,000 and 570,000 respectively, and glass transition temperature ($T_g$) of PTMSP/PDMS graft copolymer appeared at $33.53^{\circ}C$ according to DSC analysis. According to the TGA measurements, the addition of borosilicate to the PTMSP/PDMS graft copolymer leaded the decreased weight loss and the completed weight loss temperature went down. SEM observation showed that borosilicate was dispersed in the PTMSP/PDMS-borosilicate composite membranes with the size of $1{\sim}5{\mu}m$. Gas permeation experiment indicated that the addition of borosilicate to PTMSP/PDMS graft copolymer resulted in the increase in free volume, cavity and porosity resulting in the gradual shift of the mechanism of the gas permeation from solution diffusion to molecular sieving surface diffusion, and Knudsen diffusion. Consequently, the permeability of $H_2$ and $N_2$ increased and selectivity ($H_2/N_2$) decreased as the contents of borosilicate increased.