• Preventive Nutrition and Food Science
• /
• v.3 no.2
• /
• pp.143-151
• /
• 1998

Protein -surfactant interactions have been investigate by measuring ζ-potential of $\beta$-lactoglobulin-coated emulsion droplets and $\beta$-lactoglobulin in solution in the rpesenceof surfactant, with particular emphasis on the effect of protein heat treatment(7$0^{\circ}C$, 30min). When ionic surfactant (SDS or DATEM) is added to the protein solution, the ζ-potential of the mixture is found to increase with increasing surfactant concentration, indicating surfactant binding to the protein molecules. For heat-denatured protein,it has been observed that the ζ-potential tends to be lower than that of the native protein. The effect of surfactant on emulsions is rather complicated .With SDS, small amounts of surfactant addition induce a sharp increase in zeta potential arising from the specific interaction of surfactant with protein. With further surfacant addition, there is a gradual reductio in the ζ-potential, presumably caused by the displacement of adsorped protein (and protein-surfactant complex) from the emulsion droplet surfac by the excess of SDS molecules. At even higher surfactant concentrations, the measured zeta potential appears to increase slightly, possibly due to the formation of a surfactant measured zeta potential appears to increase slightly, possibly due to the formation of surfactant micellar structure at the oil droplet surface. This behaviour contrastswith the results of the corresponding systems containing the anionic emulsifier DATEM, in which the ζ-potential of the system is found to increase continuously with R, particularly at very low surfactant concentration. Overall, such behaviour is consisten with a combination of complexation and competitive displacement between surfactant and protein occurring at the oil-water interface. In addition, it has also been found that above the CMC, there is a time-dependent increase in the negative ζ-potential of emulsion droplets in solutions of SDS, possibly due to the solublization of oil droplets into surfactant micelles in the aqueous bulk phase.

• Journal of the Korean Chemical Society
• /
• v.58 no.4
• /
• pp.351-358
• /
• 2014

Anionic (sodium lauryl sulphate, NaLS) cationic (cetyl ammonium bromide, CTAB) and non-ionic (Tween-80) surfactants have been found to inhibit the rate of oxiadation L-proline and L-methionine by alkaline $KMnO_4$. A first order dependence of rate of oxidation was observed with respect to $MnO_4{^-}$. The order of reaction in substrate and alkali was found to be fractional nearby 0.65 and 0.55 in Aminoacid and $OH^-$, respectively. An aggregation/association between $MnO_4{^-}$ and surfactant has been confirmed spectrophotometrically. A mechanism, involving kinetically inactive [$MnO_4{^-}$ surfactant] aggregate and consistent with kinetic data, has been proposed. The effect of surfactants has been discussed in terms of hydrophobic and electrostatic interactions.

• Journal of Applied Biological Chemistry
• /
• v.57 no.1
• /
• pp.33-40
• /
• 2014

Polysaccharides have attracted great attention for their wide range of applications in biological and medical fields. In this paper, the interaction of polysaccharides with human serum albumin (HSA) was systematically investigated by fluorescence (FL) spectroscopy and circular dichroism (CD) spectra under different conditions. The Stern-Volmer quenching constants ($K_a$) at different ionic strength and pH were calculated, and information of the structural features of HSA was discussed. FL and CD results indicate that both hydrophobic and electrostatic interactions play important roles during the binding process. The quenching of the fluorescence resulting the binding of polysaccharides and HSA is static.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.37-38
• /
• 2006

Conjugated diacetylene supramolecules are interesting biomimetic materials in view of application to chemical and label-free biological sensors. These supramolecules are unique in changing color from blue to red upon specific binding events. Various binding events including viruses, toxins, glucose, and ionic interactions have been reported detectible. Here, we focus on fabrication of polydiacetylene supramolecule dot array patterns on solid substrates by using a conventional microarrayer. Each dot is found to possess the color-changing property as well as the fluorescence self-emission. This technique allows us, for the first time, to fabricate biochips based on polydiacetylene supramolecules. Label-free detection of small molecules and biological targets will be discussed.

• Macromolecular Research
• /
• v.13 no.5
• /
• pp.385-390
• /
• 2005

The electrospinning process is a fascinating method to fabricate small nanosized fibers of diameter several hundred nanometers. Surfactant-polymer solutions were prepared by adding poly(vinyl alcohol) (PVOH) to distilled water with cationic, anionic, amphoteric, and non-ionic surfactants. Average diameter of the electrospun PVOH fibers prepared from PVOH solution was over 300 nm, and was decreased to 150 nm for the mixture of PVOH/amphoteric surfactant. To explain the formation of ultra fine fiber, the characteristic properties in a mixture of PVOH/surfactant such as surface tension, viscosity, and conductivity were determined. In this paper, the effect of interactions between polymers with different classes of surfactants on the morphological and mechanical properties of electrospun PVOH nonwoven mats was broadly investigated.

• Bulletin of the Korean Chemical Society
• /
• v.2 no.4
• /
• pp.132-138
• /
• 1981

Ab initio molecular orbital calculations have been performed in an effort to determine which types of chemical interactions play essential roles for the system, , $H_2O+CH_2SH^+$, and $H_2O+ CH_2S$. The most important contribution to the interaction energy in controlling reaction path is the exchange repulsion energy, EX, which is largely responsible for the shape of the total interaction energy curve. In the ion-molecule reaction, prior protonation of thioformaldehyde or prior deprotonation of water leads to formation of the corresponding ionic adducts ($H_2O+CH_2SH$ and $HOCH_2S^-$), with no barrier to reaction, simulating specific acid and base catalysis, respectively, as in the case of formaldehyde. Otherwise, approach of water to thioformaldehyde gives rise to a completely repulsive interaction.

• Bulletin of the Korean Chemical Society
• /
• v.17 no.6
• /
• pp.511-514
• /
• 1996

The interactions between Ln(dpm)3 [Ln3+=Eu3+, Yb3+, Pr3+, Sm3+, Tb3+and Ho3+; dpm=tris 2,2,6,6-tetramethylheptane-3,5-dionate] and acetamide in CCl4 solution were investigated using near IR absorption spectroscopy. From the measured 2 νC=O+ amide Ⅲ combination band of acetamide in the region of 2130-2180 nm(4695-4587 cm-1), it was found that acetamide is coordinating through its carbonyl oxygen atom to Ln(dpm)3[C=O…Ln(dpm)3)] and forms only 1 : 1 stoichiometric Ln(dpm)3- acetamide complex. The ΔHo values for the formation of Ln(dpm)3-acetamide obtained from the temperature studies are -39.1, -28.4, -25.5, -24.7, -21.1 and -17.7 kJ mol-1 for Eu(dpm)3, Yb(dpm)3, Pr(dpm)3, Sm(dpm)3, Tb(dpm)3 and Ho(dpm)3, respectively, which are larger than those of the hydrogen bond between amide and various hydrogen acceptors. Except Eu(dpm)3 and Yb(dpm)3, -ΔHovalue increases as the ionic size increases.

• Journal of the Korean Chemical Society
• /
• v.68 no.2
• /
• pp.65-73
• /
• 2024

The halide-acetylene anions, X^--HCCH (X = F, Cl, and Br) have been studied by using several different ab initio and DFT methods to determine structures, hydrogen-bond energies, vibrational frequencies of the anion complexes. Although the halide-acetylene complexes all have linear equilibrium structures, it is found that the fluoride complex is characterized with distinctively different structure and interactions compared to those of the chloride and bromide complexes. The performance of various density functionals on describing ionic hydrogen-bonded complexes is assessed by examining statistical deviations with respect to high level ab initio CCSD(T) results as reference. The density functionals employed in the present work show considerably varying degrees of performance depending on the properties computed. The performances of each density functional on geometrical parameters related with the hydrogen bond, hydrogen-bond energies, and scaled harmonic frequencies of the anion complexes are examined and discussed based on the statistical deviations.

• Archives of Pharmacal Research
• /
• v.26 no.10
• /
• pp.846-854
• /
• 2003

The oligomerization of G-proteincoupled receptors (GPCRs) has been shown to occur by various mechanisms, such as via disulfide covalent linkages, non covalent (ionic, hydrophobic) interactions of the N-terminal, and/or transmembrane and/or intracellular domains. Interactions between GPCRs could involve an association between identical proteins (homomers) or non-identical proteins (heteromers), or between two monomers (to form dimers) or multiple monomers (to form oligomers). It is believed that muscarinic receptors may also be arranged into dimeric or oigomeric complexes, but no systematic experimental evidence exists concerning the direct physical interaction between receptor proteins as its mechanism. We undertook this study to determine whether muscarinic receptors form homomers or a heteromers by direct protein-protein interaction within the same or within different subtypes using a yeast two-hybrid system. Intracellular loops (i1, i2 and i3) and the C-terminal cytoplasmic tails (C) of human muscarinic (Hm) receptor subtypes, Hm1, Hm2 and Hm3, were cloned into the vectors (pB42AD and pLexA) of a two-hybrid system and examined for heteromeric or homodimeric interactions between the cytoplasmic domains. No physical interaction was observed between the intracellular domains of any of the Hm/Hm receptor sets tested. The results of our study suggest that the Hm1, Hm2 and Hm3 receptors do not form dimers or oligomers by interacting directly through either the hydrophilic intracellular domains or the C-terminal tail domains. To further investigate extracellular domain interactions, the N-terminus (N) and extracellular loops (o1 and o2) were also cloned into the two-hybrid vectors. Interactions of Hm2N with Hm2N, Hm2o1, Hm2o2, Hm3N, Hm3o1 or Hm3o2 were examined. The N-terminal domain of Hm2 was found to have no direct interaction with any extracellular domain. From our results, we excluded the possibility of a direct interaction between the muscarinic receptor subtypes (Hm1, Hm2 and Hm3) as a mechanism for homo- or hetero-meric dimerization/oligomerization. On the other hand, it remains a possibility that interaction may occur indirectly or require proper conformation or subunit formation or hydrophobic region involvement.

• Polymer(Korea)
• /
• v.33 no.6
• /
• pp.615-619
• /
• 2009

Pd-POSS nanoparticles were produced from the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$) in methanol at room temperature. Pd-POSS nanoparticles with a mean diameter of 60-80 nm were the highly ordered spherical aggregates. In contrast, Pd nanoparticles with a size of 4.0 nm were obtained when POSS-${NH_3}^+$ was not introduced. Pd-POSS/PAA nanocomposites of Pd-POSS nanoparticles and poly(acrylic acid) (PAA) were fabricated by utilizing ionic interactions between positively charged Pd-POSS nanoparticles and negatively charged carboxylate groups of PAA. PAA was used as a cross-linker for the preparation of hybrid nanocomposites with the controlled organized structures of Pd-POSS nanoparticles. That is, the self-organization of Pd-POSS nanoparticles was formed into the shape of continuous lines by using PAA as a cross-linker. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/PAA nanocomposites were studied by FE-SEM, AFM, TEM, FT-IR, and TGA.