PDZ Domain-containing 1 (PDZK1) Protein Regulates Phospholipase C-β3 (PLC-β3)-specific Activation of Somatostatin by Forming a Ternary Complex with PLC-β3 and Somatostatin Receptors

Kim, Jung Kuk,Kwon, Ohman,Kim, Jinho,Kim, Eung-Kyun,Park, Hye Kyung,Lee, Ji Eun,Kim, Kyung Lock,Choi, Jung Woong,Lim, Seyoung,Seok, Heon,Lee-Kwon, Whaseon,Choi, Jang Hyun,Kang, Byoung Heon,Kim, Sanguk American Society for Biochemistry and Molecular Bi 2012 The Journal of biological chemistry Vol.287 No.25

Direct Profiling the Post-Translational Modification Codes of a Single Protein Immobilized on a Surface Using Cu-free Click Chemistry

Kim, Kyung Lock,Park, Kyeng Min,Murray, James,Kim, Kimoon,Ryu, Sung Ho American Chemical Society 2018 ACS central science Vol.4 No.5

<▼1><P/><P>Combinatorial post-translational modifications (PTMs), which can serve as dynamic “molecular barcodes”, have been proposed to regulate distinct protein functions. However, studies of combinatorial PTMs on single protein molecules have been hindered by a lack of suitable analytical methods. Here, we describe erasable single-molecule blotting (eSiMBlot) for combinatorial PTM profiling. This assay is performed in a highly multiplexed manner and leverages the benefits of covalent protein immobilization, cyclic probing with different antibodies, and single molecule fluorescence imaging. Especially, facile and efficient covalent immobilization on a surface using Cu-free click chemistry permits multiple rounds (>10) of antibody erasing/reprobing without loss of antigenicity. Moreover, cumulative detection of coregistered multiple data sets for immobilized single-epitope molecules, such as HA peptide, can be used to increase the antibody detection rate. Finally, eSiMBlot enables direct visualization and quantitative profiling of combinatorial PTM codes at the single-molecule level, as we demonstrate by revealing the novel phospho-codes of ligand-induced epidermal growth factor receptor. Thus, eSiMBlot provides an unprecedentedly simple, rapid, and versatile platform for analyzing the vast number of combinatorial PTMs in biological pathways.</P></▼1><▼2><P>An <U>e</U>rasable <U>si</U>ngle <U>m</U>olecule <U>blot</U> (eSiMBlot) assay provides an unprecedentedly simple and versatile platform for analyzing the combinatorial post-translational modifications in biological pathways.</P></▼2>

Similarity and Dissimilarity in Surface-Enhanced Raman Scattering of 4-Aminobenzenethiol, 4,4′-Dimercaptoazobenzene, and 4,4′-Dimercaptohydrazobenzene on Ag

Kim, Kwan,Kim, Kyung Lock,Lee, Hyang Bong,Shin, Kuan Soo American Chemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.21

<P>There has been a surge of interest in the surface-enhanced Raman scattering (SERS) of 4-aminobenzenethiol (4-ABT) and 4,4′-dimercaptoazobenzene (4,4′-DMAB), since 4,4′-DMAB might be capable of being produced from 4-ABT via a surface-induced photoreaction. A problem was initially encountered in the interpretation of the SERS spectrum of 4-ABT due to difficulty in correlating several peaks therein with the normal Raman peaks, as the SERS spectral pattern of 4-ABT looked similar to that of 4,4′-DMAB. To clarify the issue, we have carefully examined the similarities and dissimilarities in the SERS of 4-ABT and 4,4′-DMAB, along with the SERS spectrum of their analogue molecule 4,4′-dimercaptohydrazobenzene (4,4′-DMHAB). Under ambient conditions, the SERS spectra of 4-ABT, 4,4′-DMAB, and 4,4′-DMHAB on Ag looked in fact comparable to one another, but the excitation wavelength dependence of the peak intensities dictated that the similarity in the SERS spectral patterns could not guarantee the photoconversion of the three molecules. On the other hand, the spectral dissimilarity was evidenced not only from the SERS spectra taken after treating the probing substrates with a borohydride solution but also from the potential-dependent SERS spectra. An electrochemical reaction did not take place for 4-ABT and 4,4′-DMHAB on Ag either by placing the substrates in contact with a borohydride solution or by lowering the electrode potential down to −1.2 V versus a saturated Ag/AgCl electrode. Conversely, however, 4,4′-DMAB on Ag was converted to 4-ABT not only by contact with a 100 mM borohydride but also by lowering the potential below −1.0 V. The reverse reaction from 4-ABT on Ag to 4,4′-DMAB appeared to be insignificant electrochemically as well as photochemically. All of these results clearly support our previous proposition that the b<SUB>2</SUB>-type bands appearing in the SERS of 4-ABT must be attributable to the chemical enhancement of 4-ABT itself.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-21/jp303378p/production/images/medium/jp-2012-03378p_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp303378p'>ACS Electronic Supporting Info</A></P>

Surface enrichment of Ag atoms in Au/Ag alloy nanoparticles revealed by surface enhanced Raman scattering spectroscopy

Kim, Kwan,Kim, Kyung Lock,Lee, Seung Joon Elsevier 2005 Chemical physics letters Vol.403 No.1

<P><B>Abstract</B></P><P>Au/Ag alloy nanoparticles consisting of various mole fractions of gold and silver have been synthesized in aqueous medium using a citrate reduction method. UV/vis spectra confirm the formation of alloy nanoparticles and transmission electron microscopy reveals a rather uniform distribution of ∼35 nm-sized particles. The most interesting finding deduced from the surface-enhanced Raman scattering (SERS) of pyridine is that the Ag atoms are highly enriched in the outermost layers of the nanoparticles compared with their interiors. SERS is thus demonstrated to be an efficient surface analyzing tool specifically in nano scales for noble metal alloys.</P>

Surface-Enhanced RamanScattering of 4-Aminobenzenethiolon Ag and Au: pH Dependence of <i>b</i>₂-TypeBands

Kim, Kwan,Kim, Kyung Lock,Shin, Dongha,Choi, Jeong-Yong,Shin, Kuan Soo AmericanChemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.7

<P>The surface-enhanced Raman scattering (SERS) of 4-aminobenzenehtiol (4-ABT) has seen a surge of interest recently, since its SERS spectral features are dependent not only on the kinds of SERS substrates but also on the measurement conditions. The most unusual SERS feature is the appearance of b(2)-type bands in the region 1100-1500 cm(-1), in contrast to their absence in the normal Raman spectrum, but their origin is not yet clarified. However, propositions have been made suggesting that their appearance is associated with either a charge transfer phenomenon or a surface-induced photoreaction product such as 4,4'-dimercaptoazobenzene (4,4'-DMAB). In this work, we found that the b(2)-type bands of 4-ABT are strongly affected also by the solution pH. Regardless of the excitation wavelength and kind of SERS substrates, the b(2)-type bands appeared very weakly or negligibly at acidic pHs, while they were observed very distinctly at basic pHs. For the case of 4,4'-DMAB, any such pH dependence was not observed at all in its SERS spectra. Since the pH dependence in the SERS of 4-ABT was observed reversibly, the appearance and disappearance of the b(2)-type bands must have nothing to do with formation of any surface-induced photoreaction product like 4,4'-DMAB. Consulting the pH-dependent UV-vis absorption spectra and ab initio quantum mechanical calculation, the disappearance of the b(2)-type bands at acidic pHs is presumed to be associated with the upshift of the lowest unoccupied molecular orbital level of 4-ABT caused by protonation of the amine group: the charge transfer resonance chemical enhancement will then be less likely to occur.</P>

Surface-enhanced Raman scattering of 4,4′-dimercaptoazobenzene trapped in Au nanogaps

Kim, Kwan,Shin, Dongha,Kim, Kyung Lock,Shin, Kuan Soo The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.12

<P>The surface-enhanced Raman scattering (SERS) of 4,4′-dimercaptoazobenzene (4,4′-DMAB), an alpha, omega-dithiol possessing also an azo moiety, has seen a surge of interest recently, since 4,4′-DMAB might be able to form from 4-aminobenzenethiol (4-ABT) <I>via</I> a surface-induced photoreaction. An understanding of the intrinsic SERS characteristics of 4,4′-DMAB is thus very important to evaluate the possibility of such a photoreaction. We found in this work that 4,4′-DMAB should adsorb on a flame-annealed Au substrate <I>via</I> one of its two thiol groups such that Au nanoparticles could adsorb further on the pendent thiol group, forming a SERS hot site. The most distinctive feature in the SERS of 4,4′-DMAB was the appearance of <I>a</I><SUB><I>g</I></SUB> bands, which were quite similar to the <I>b</I><SUB>2</SUB>-type bands occurring in the SERS of 4-ABT. In an electrochemical environment, the <I>a</I><SUB><I>g</I></SUB> bands of 4,4′-DMAB at 1431, 1387, and 1138 cm<SUP>−1</SUP> became weakened at lower potentials, completely disappearing at −1.0 V, but the bands were restored upon increasing the electrode potential, implying that neither electro- nor photo-chemical reaction to break the azo group took place, in agreement with data from a cyclic voltammogram. The appearance and disappearance of these <I>a</I><SUB><I>g</I></SUB> bands are thus concluded to be associated with the charge transfer phenomenon: 4,4′-DMAB must then be one of a unique group of compounds exhibiting chemical enhancement when subjected to a SERS environment.</P> <P>Graphic Abstract</P><P>We thoroughly examined the surface-enhanced Raman scattering characteristics of 4,4′-dimercaptoazobenzene trapped in an Au nanogap electrode, comparing with those of 4-aminobenzenethiol. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp24135h'> </P>

Effect of volatile organic chemicals on surface-enhanced Raman scattering of 4-aminobenzenethiol on Ag: comparison with the potential dependence

Kim, Kwan,Kim, Kyung Lock,Choi, Jeong-Young,Shin, Dongha,Shin, Kuan Soo Royal Society of Chemistry 2011 Physical chemistry chemical physics Vol.13 No.34

<P>4-Aminobenzenethiol (4-ABT) is an unusual molecule in the sense that several distinct peaks whose counterparts are rarely found in the normal Raman spectrum are observed in its surface-enhanced Raman scattering (SERS) spectra. Their origin has been argued over recently as due to either a metal-to-adsorbate charge transfer or the formation of a photoreaction product such as dimercaptoazobenzene (DMAB). In an electrochemical SERS measurement, the intensities of the new peaks depended strongly not only on the excitation wavelength but also on the electrode potential. Interestingly, we observed a similar spectral variation even under ambient conditions by exposure of 4-ABT on Ag to volatile organic chemicals (VOCs) such as acetone and ammonia. Since acetone and ammonia barely react directly with 4-ABT, the effect of VOCs must be indirect, presumably associated with the movement of electrons between VOCs and the Ag substrate causing either an increase or a decrease in the surface potential of Ag. Based on the potential-dependent SERS data, the effect of acetone therefore appeared to correspond to an application of +0.15 V to the Ag substrate <I>vs</I>. a saturated Ag/AgCl electrode, while the effect of ammonia corresponded to the application of −0.45 V to Ag. We admit that much the same VOC effect could be observable if a photoproduct was formed immediately upon irradiation and the product was also subjected to a chemical enhancement mechanism. The Gaussian response of the peak intensities of the b<SUB>2</SUB>-type bands to applied potential, as well as to VOCs, dictated that the new peaks appearing in the SERS of 4-ABT have nothing to do with any electrochemical reaction. In addition, a separate preliminary work suggested that the b<SUB>2</SUB>-type bands are not at least due to a photoreaction product such as DMAB.</P> <P>Graphic Abstract</P><P>The Raman peak intensity of 4-aminobenzenethiol on Ag was found to be very susceptible not only to the excitation wavelength applied but also to the kind of volatile organic chemicals to which the Ag films were exposed. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cp21249d'> </P>

Coreduced Pt/Ag Alloy Nanoparticles: Surface-Enhanced Raman Scattering and Electrocatalytic Activity

Kim, Kwan,Kim, Kyung Lock,Shin, Kuan Soo American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.47

<P>In an effort to develop highly effective Pt-based substrates for surface-enhanced Raman scattering (SERS) and electrocatalysis, we have synthesized 10 nm-sized Pt/Ag alloy nanoparticles, preparing first 7 nm-sized seed particles of Pt, followed by the coreduction of Ag and Pt precursors onto them. The formation of Pt core–Pt/Ag alloy shell nanoparticles was evident from their UV–visible extinction characteristics, X-ray diffraction patterns, and high-resolution transmission electron microscopy and high-angle annular dark-field scanning transmission electron microscopy images. According to the phase diagram, an alloy is possible only with a very high atomic content of either Ag or Pt, but the formation of alloys herein, even with an apparent composition of Pt<SUB>0.70</SUB>Ag<SUB>0.30</SUB>, can be understood by presuming that due to the presence of seed Pt particles, the reduction potentials of Pt and Ag are modified to allow the formation of Pt/Ag alloys onto them. The formation of alloys of Pt with Ag has resulted in the enhancement of not only the SERS activity but also the electrocatalytic activity of Pt alone. The SERS activity was confirmed to increase as more Ag was incorporated into Pt to form Pt/Ag alloy nanoparticles. As a methanol electrooxidation catalyst, a pure Pt surface was poisoned by incompletely oxidized species such as CO and was thus unable to recover its electrocatalytic activity. In contrast, methanol oxidation peaks were observed in repeated cycles when Pt/Ag alloyed electrodes were used. In particular, the ratio of the forward oxidation current peak to the reverse current peak was as large as 2.52 for the Pt<SUB>0.95</SUB>Ag<SUB>0.05</SUB> electrode, which is more than 3 times larger than that of a commercially available pure Pt catalyst, suggesting that the Pt/Ag alloy catalysts are superior in their ability to tolerate poisoning species.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-47/jp2063707/production/images/medium/jp-2011-063707_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp2063707'>ACS Electronic Supporting Info</A></P>

Visible-Light Response of 4-Aminobenzenethiol and 4,4′-Dimercaptoazobenzene Silver Salts

Kim, Kwan,Kim, Kyung Lock,Shin, Kuan Soo American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.11

<P>Silver thiolate, which is an organic–inorganic heterostructured material, converts into thiol-derivatized Ag nanoparticles after irradiation with a visible laser. In this study, the visible-laser responses of 4-aminobenzenethiol (4-ABT) and 4,4′-dimercaptoazobenzene (4,4′-DMAB) silver salts were examined to verify that 4,4′-DMAB on Ag converts to 4-ABT on Ag because of the irradiation of light with a wavelength of 514.5 nm, to resolve the issues that result from the surface-enhanced Raman scattering (SERS) characteristics of 4-ABT. Due to the appearance of unpredicted, non-a<SUB>1</SUB>-type bands, the SERS spectrum of 4-ABT is very similar to that of 4,4′-DMAB. One explanation for the non-a<SUB>1</SUB>-type bands is that they are associated with the charge-transfer chemical-enhancement mechanism of SERS, but a few researchers have attributed them to photoinduced catalytic conversion of 4-ABT on Ag to 4,4′-DMAB. Using 514.5 nm radiation, we recently reported the successful conversion of 4,4′-DMAB on Ag to 4-ABT; however, the reverse reaction from 4-ABT to 4,4′-DMAB did not occur. Similarly, in this study, 4,4′-DMAB Ag salts first converted to 4,4′-DMAB-adsorbed Ag nanoparticles and then to 4-ABT on Ag nanoparticles after prolonged 514.5 nm irradiation. According to the results of a laser-power dependence study, the photoinduced reduction of 4,4′-DMAB on Ag to 4-ABT is a single-photon process. The photoinduced conversion of 4,4′-DMAB to 4-ABT was more facile as Ag salts than as being assembled on Ag films, which implies that fresh Ag nanoparticles produced in situ are more efficient photoelectron emitters than are aged ones. The non-a<SUB>1</SUB>-type bands that appear in the SERS of 4-ABT are thus attributed to the chemical-enhancement mechanism rather than to photoconversion.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-11/jp312252m/production/images/medium/jp-2012-12252m_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp312252m'>ACS Electronic Supporting Info</A></P>

Photoreduction of 4,4′-Dimercaptoazobenzene on Ag Revealed by Raman Scattering Spectroscopy

Kim, Kwan,Kim, Kyung Lock,Shin, Kuan Soo American Chemical Society 2013 Langmuir Vol.29 No.1

<P>The surface-enhanced Raman scattering (SERS) of 4,4′-dimercaptoazobenzene (4,4′-DMAB) has recently seen a surge of interest, since it might be possible to form 4,4′-DMAB from 4-aminobenzenethiol (4-ABT) via a surface-induced photoreaction. We found in this study, however, that the reverse conversion of 4,4′-DMAB to 4-ABT on Ag is a more feasible process upon irradiation with a 514.5 nm (not 632.8 nm) laser under ambient conditions. First of all, the SERS spectral pattern of 4,4′-DMAB on Ag varied as a function of laser irradiation time, finally becoming the same as that of 4-ABT on Ag. Second, the coupling reaction with 4-cyanobenzoic acid to form amide bonds proceeded readily like 4-ABT once 4,4′-DMAB on Ag was exposed to 514.5 nm radiation. Third, the growth of a calcite crystal occurred on 4,4′-DMAB on Ag, also likely on 4-ABT, when it was exposed to 514.5 nm radiation beforehand. All of these results led us to conclude that the appearance of the so-called b<SUB>2</SUB>-type bands in the SERS of 4-ABT must be due to the involvement of the chemical enhancement mechanism, not due to the formation of 4,4′-DMAB.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2013/langd5.2013.29.issue-1/la304159c/production/images/medium/la-2012-04159c_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la304159c'>ACS Electronic Supporting Info</A></P>