• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2149-2151
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• 2009

• Journal of Biomedical Engineering Research
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• v.40 no.1
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• pp.1-6
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• 2019

Human mesenchymal stem cells (hMSC) are multipotent stromal cells that have great potential to differentiate into a variety of cell types such as osteocytes, chondrocytes, and myocytes. Although there have been many studies on their clinical availability, little is known about how intracellular signals can be modulated by topographic features of the extracellular matrix (ECM). In this study, we investigated whether and how microwavy-patterned extracellular matrix (ECM) could affect the signaling activity of focal adhesion kinase (FAK), a key cellular adhesion protein. The fluorescence resonance energy transfer (FRET)-based FAK biosensor-transfected cells are incubated on microwavy-patterned surfaces and then platelet derived growth factor (PDGF) are treated to trigger FAK signals, followed by monitoring through live-cell FRET imaging in real time. As a result, we report that PDGF-induced FAK was highly activated in cells cultured on microwavy-patterned surface with L or M type, while inhibited by H type-patterned surface. In further studies, PDGF-induced FAK signals are regulated by functional support of actin filaments, microtubules, myosin-related proteins, suggesting that PDGF-induced FAK signals in hMSC upon microwavy surfaces are dependent on cytoskeleton (CSK)-actomyosin networks. Thus, our findings not only provide new insight on molecular mechanisms on how FAK signals can be regulated by distinct topographical cues of the ECM, but also may offer advantages in potential applications for regenerative medicine and tissue engineering.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.352-352
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• 2010

일반적인 근접장 현미경은 광섬유 팁 (tip) 끝에 수십 nm 크기의 구멍을 이용하여 근접장을 발생시키거나 측정한다. 근접장은 전파되는 빛보다 미세한 구조의 정보를 반영하게 되는데 수십 나노미터의 구멍대신 FRET (fluorescence resonance energy transfer)이라는 현상을 근접장 현미경에 적용하고자 한다. 10 nm 이내의 거리에서 상호작용을 하는 이 현상을 이용하여 광학적 분해능을 향상시킬 수 있다. FRET 현상의 도우너(donor)로서는 양자점을 사용하였으며 억셉터(acceptor) 로서는 Cy5 염료를 사용하였다. 팁으로는 광섬유를 에칭한 팁에 Cy5 염료를 코팅한 팁과 광섬유의 코어(core) 부근에 양자점이 포함된 광 폴리머를 응고시켜서 만들어진 팁을 사용하였다. 팁에 위치한 도우너와 시료로 사용되는 억셉터를 FRET 상호 작용 거리 내로 접근시키기 위하여 tuning fork를 이용한 shear force control을 사용하였다. 한 점에서의 접근 과정에서 FRET의 현상의 특징으로서 도우너인 양자점의 형광이 약해지고 Cy5의 형광이 강해지는 것을 측정하였다. 또한, 양자점을 Cy5 염료에 근접시켰을 때 발광 생존시간 (lifetime)이 짧아지는 것을 관찰하여 FRET 현상을 재확인 하였다.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.1021-1024
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• 2010

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.314-314
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• 2006

The FRET property has been extensively studied from the theoretical view points to the practical applications. In case that the donor and acceptor are confined in nanodimension, the FRET effectively occurs, because of their distant dependent characteristic. However, there are no reports concerning FRET with one dimensional (1D) nanomaterial. We have successfully prepared the PMMA nanotubes using vapor deposition polymerization as the platform of FRET. The dye-PMMA composite nanofiber has also been produced without phase separation and any deterioration of properties of the dyes. The PMMA 1D nanocomposite doped two dyes with great spectral overlap between donor and acceptor displayed FRET property.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3229-3232
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• 2011

A FRET-based high-throughput screening system was developed for the discovery of competitive smallmolecule Hsp90 inhibitors. The biarsenical fluorescein derivative FlAsH and dabcyl-conjugated Hsp90 inhibitor GM were employed as the FRET donor and quencher, respectively. The spatial proximity perturbation between FlAsH-labeled Hsp90N and GM-dabcyl upon treatment of a small molecule led to changes in the FRET-induced fluorescence, monitored in a high-throughput fashion.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.529-534
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• 2012

The fluorescence of 4',6-diamidino-2-phenylindole (DAPI) bound to DNA at a [DAPI]/[DNA base] ratio of 0.005 was quenched by meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) or cis-bis(N-methylpyridinium-4-yl)porphyrin (BMPyP) when both DAPI and either porphyrin spontaneously bound to the same DNA strand. The quenching was investigated using the "one-dimensional inner sphere" and the "F$\ddot{o}$rster resonance energy transfer" (FRET) models. Total quenching occurred when DAPI and TMPyP were up to 19.3 base pairs or $66\AA$ apart. BMPyP could quench the fluorescence up to 13.9 base pairs or $47\AA$. TMPyP, which intercalated between the DNA base-pairs, appeared to be a better acceptor than BMPyP, which stacked along the DNA stem. The higher quenching and higher resonance energy transfer efficiency of TMPyP was due to the larger overlap integral between its absorption spectrum and the emission spectrum of DNA-bound DAPI.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.4
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• pp.743-750
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• 1997

Direct measurement of the kinetics of free fatty acid transfer between phospholipid model membrane is technically limited by the rapid nature of the transfer process. Separation of membrane-bound fatty acid by centrifugation has shown that although the equilibrium distribution of free fatty acid is determined by this method, fatty acid transfer occurs too rapidly for accurate kinetic measurements. Recently fluorescence resonance energy transfer(FRET) assay has been developed to examine transfer of fatty acids between membranes. Donor membranes which has fluorescent fatty acid, anthroyloxy fatty acid(AOFA), is mixed with acceptor membranes which has non-interchangeable fluorescent quencher, nitrobenzo-xadiazol(NBD), using stopped flow apparatus. As the fluorescent fatty acids transfer from donor membrane to acceptor membrane, fluorescence intensity would be decreased and the rate and degree of fatty acid transfer can be analyzed. Fatty acid transfer between micelles is more complicated because of bile salt. Therefore in experiments with micelles, fluorescence self quenching assay is used. At high concentrations, a fluorophore tends to quench its own fluorescence causing a reduction in fluorescence intensity. Donor micelles contained self quenching concentrations of fluorophore and acceptor micelles had no fluorophore. Upon mixing of donor and acceptor micelles, the rate of transfer of the fluorophore from the donor to the acceptor was measured by monitoring the release in self quenching when its concentration in donor decreased over time.

• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1817-1820
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• 2009

Controlling cell-matrix interactions is critical in regulating cell phenotypes for tissue engineering applications. Cellular adhesion to synthetic extracellular matrices (ECMs) can be enhanced by introduction of adhesion ligands to the matrices. We tested the hypothesis that biophysical cues such as ligand organization in synthetic ECMs play an important role in modulating cell responses to the microenvironment. To investigate and monitor cell-matrix interactions, we used a fluorescence resonance energy transfer (FRET) technique with cell-interactive polymers generated by conjugating a peptide with the sequence of arginine-glycine-aspartic acid (RGD) to alginate hydrogels.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.221-226
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• 2013

The water soluble quantum dots (QDs) are synthesized by the phase transfer and silica coating reaction. The photoluminescence intensity of silica-coated QDs are mainly affected by the amount of phase transfer agent, SDS (sodium dodecyl sulfate), and the maximum value is obtained at the cmc (critical micell concentration) concentration of SDS in the phase transfer reaction. Based on fluorescence spectra and field emission transmission electron microscope (FETEM), the energy transfer rate by forster resonance energy transfer (FRET) is increasing with the thickness of the silica shell coated on CdSe/ZnS QDs.