• Carbon letters
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• v.27
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• pp.26-34
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• 2018

To formulate folate receptor (FR)-specific graphene-based electrochemical electrodes, a folic acid (FA) derivative attached with two pyrene molecules on the glutamate tail of FA was synthesized. The resulting pyrene-functionalized FA (FA-Py) presented the spontaneous noncovalent binding on chemically reduced graphene oxides (rGO) through an ${\pi}-{\pi}$ interaction. Ultrathin morphology, high water-resistance, and preservation of intact FR-specific pteroates from the rGO/FA-Py assembly allow this assembly to be exploited as robust and FR-specific electrochemical electrode materials. The limits of detecting rGO/FA-Py modified electrodes were found to be as low as 3.07 nM in FR concentrations in cyclic voltammetry analysis.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.71-71
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• 2012

Chemically modified graphene has been great interest for the application of printed electronics using solution prossesable technique. Here, we demonstrate a large area graphene exfoliation method with fewer defects on the basal plane by application of shear stress in solution to obtain high quality reduced graphene oxide (RGO). Moreover, we introduce a novel route to preparing highly concentrated and conductive RGO in various solvents by monovalent cation-${\pi}$ interaction. Noncovalent binding forces can be induced between a monopole (cation) and a quadrupole (aromatic ${\pi}$ system). The stability of this RGO dispersion was more sensitive to the strength of the cation-${\pi}$ interactions than to the cation-oxygen functional group interactions. The RGO film prepared without a post-annealing process displayed superior electrical conductivity of 97,500 S/m. Our strategy can facilitate the development of large scalable production methods for preparing printed electronics made from high-quality RGO nanosheets.

• Journal of Life Science
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• v.2 no.2
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• pp.97-107
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• 1992

Strichartz and Richie have suggested that the mechanism of sodium donductance block of local anesthetics involves their interaction with a specific binding site within the sodium channel. However, there is evidence that local anesthetics can interact electrostatically with membrane proteins as well as membrane lipids. Whether or not all actions of local anesthetics are mediated by common site remains unclear. Thus, it can not be ruled out that local anesthetics concurrently interact with neuronal membrane lipids since sodium channels were found to be tightly associated with membrane lipids through covalent or noncovalent bonds. In summary, it is strongly postulated that local anesthetics, in addition to their direct interaction with sodium channels, concurrently interact with membrane lipids, fluidize the membrane, and thus induce conformational changes of sodium channels, which are known to be tightly associated with membrane lipids.

• Journal of Life Science
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• v.9 no.1
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• pp.76-83
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• 1999

Mammalial expression vectors containing GRP94, BiP, ERp72, and PDI, were introduced into FRTL5 cells. Transfected cells were selected by neomycin resistance for exogenously overexpressed proteins in the ER. The use of a reducible cross-linker, DSP, markedly improved the ability to detect noncovalent interactions of PDI, BiP and GRP94 with newly-synthesized thyroglobulin. Under normal conditions, GRP94 was found to associate transiently with early Tg folding intermediates, displaying interaction kinetics similar to those reported for another ER chaperones of BiP.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1277-1281
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• 2011

Making use of chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) as a reaction system, CS-EDTA nanoparticles were synthesized through a facile counterion complex coacervation method. $Ag^+$ could enter porous CS nanoparticles synthesized with this method, allowing Ag nanoparticles within chitosan nanoparticles were synthesized by reducing silver nitrate with chitosan. Because of the noncovalent interaction between CS and EDTA, the EDTA could be easily removed via dialysis against water, and pure core/shell-type Ag/CS nanoparticles could be obtained. The nanoparticles showed higher antibacterial activity toward E. coli than the active precursor Ag nanoparticles and CS.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.123-128
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• 2013

The 'Dielectrophoretic Tweezers(DEP Tweezers)' can be used as a facile, economical toolkit for quantitative measurement of chemical and biological binding forces related to many biological interactions within a microfluidic device. Our experimental setup can probe the interaction between a single receptor molecule and its specific ligand. Immunoglobulin G(IgG) functionalized on polystyrene microspheres has been used to detect individual surface linked Staphylococcus protein A(SpA) molecules and to characterize the strength of the noncovalent IgG-SpA bond. It was measured and compared with the existing measurements. Measured single binding force of between Goat, Rabbit IgG and SpA were $17{\pm}7pN$, $74{\pm}16pN$. This work can be used to investigate several different ligand-receptor interactions and antigen-antibody interactions.

• Macromolecular Research
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• v.16 no.3
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• pp.261-266
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• 2008

A variety of end-functionalized polymers were grafted spontaneously onto multi-walled carbon nano-tubes (MWNTs) using a solution mixing process. The end-functional groups of the polymers underwent noncovalent grafting to the defect sites at the surface of the purified MWNTs through zwitterionic interaction or hydrogen bonding. The physically grafted polymers including polystyrene (PS), poly(methyl methacrylate) (PMMA), polyethylene oxide (PEO), and polydimethylsiloxane (PDMS) provided sufficient compatibility with an organic solvent or polymer matrix, such that the nanotubes could be finely dispersed in various organic media. This approach is universally applicable to a broad range of polymer-solvent pairs, ensuring highly dispersed carbon nanotubes through simple solution mixing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.97-98
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• 2009

Here, we describe a versatile strategy for precise control of the optoelectrical properties of the single walled carbon nanotube (SWNT)/silane binder hybrid films by noncovalent hybridization. Stable SWNT/silane binder solutions were prepared by direct mixing of high concentration CNT solutions and silane sol solutions. The critical binder content was determined by varying the amount of binder in the SWNT/binder solutions. A binder content of 50 wt% was used to prepare the other SWNT/binder solutions. This study demonstrates how the intermolecular interactions between the SWNTs and the silanes can affect the conductivity of the CNT/binder network films by characterizing the optoelectrical and Raman spectroscopic properties of the SWNT/silane films containing silane binders with various functional groups. The use of the PTMS binder with phenyl groups was found to be most effective in the fabrication of transparent and conductive films on glass substrates. Such a precise control of the optoelectrical properties of SWNT/binder films can be useful to fabricate the high performance conductive thin films, with ramifications for understanding the fundamental intermolecular interaction in carbon materials science.

• Molecules and Cells
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• v.26 no.1
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• pp.61-66
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• 2008

Cyclic AMP receptor protein (CRP) is allosterically activated by cAMP and functions as a global transcription regulator in enteric bacteria. Structural information on CRP in the absence of cAMP (apo-CRP) is essential to fully understand its allosteric behavior. In this study we demonstrated interdomain interactions in apo-CRP, using a comparative thermodynamic approach to the intact protein and its isolated domains, which were prepared either by limited proteolysis or using recombinant DNA. Thermal denaturation of the intact apo-CRP, monitored by differential scanning calorimetry, revealed an apparently single cooperative transition with a slight asymmetry. Combined with circular dichroism and fluorescence analysis, the thermal denaturation of apo-CRP could be interpreted as a coupled process involving two individual transitions, each attributable to a structural domain. When isolated individually, both of the domains exhibited significantly altered thermal behavior, thus pointing to the existence of non-covalent interdomain interactions in the intact apo-CRP. These observations suggest that the allosteric conformational change of CRP upon binding to cAMP is achieved by perturbing or modifying pre-existing interdomain interactions. They also underline the effectiveness of a comparative approach using calorimetric and structural probes for studying the thermodynamics of a protein.