Enhanced adipogenic differentiation and reduced collagen synthesis induced by human periodontal ligament stem cells might underlie the negative effect of recombinant human bone morphogenetic protein‐2 on periodontal regeneration

Song, D‐,S.,Park, J‐,C.,Jung, I‐,H.,Choi, S‐,H.,Cho, K‐,S.,Kim, C‐,K.,Kim, C‐,S. Blackwell Publishing Ltd 2011 Journal of periodontal research Vol.46 No.2

<P> <I>Song D‐S, Park J‐C, Jung I‐H, Choi S‐H, Cho K‐S, Kim C‐K, Kim C‐S. Enhanced adipogenic differentiation and reduced collagen synthesis induced by human periodontal ligament stem cells might underlie the negative effect of recombinant human bone morphogenetic protein‐2 on periodontal regeneration. J Periodont Res 2011; 46: 193–203. © 2010 John Wiley & Sons A/S</I> </P><P><B>Background and Objective: </B> Recombinant human bone morphogenetic protein‐2 (rhBMP‐2) is a potent inducer for the regeneration of mineralized tissue, but has a limited effect on the regeneration of cementum and periodontal ligament (PDL). The aim of the present study was to determine the effects of rhBMP‐2 on the <I>in vitro</I> and <I>in vivo</I> biologic activity of well‐characterized human PDL stem cells (hPDLSCs) and to elucidate the underlying mechanism of minimal periodontal regeneration by rhBMP‐2.</P><P><B>Material and Methods: </B> hPDLSCs were isolated and cultured, and then transplanted into an ectopic subcutaneous mouse model using a carrier treated either with or without rhBMP‐2. Comprehensive histologic, histometric and immunohistochemical analyses were performed after an 8‐wk healing period. The effects of rhBMP‐2 on the adipogenic and osteogenic/cementogenic differentiation of hPDLSCs were also evaluated. The effect of rhBMP‐2 on both soluble and insoluble collagen synthesis was analyzed, and the expression of mRNA and protein for collagen types I, II, III and V was assessed.</P><P><B>Results: </B> In the present study, rhBMP‐2 promoted both adipogenic and osteogenic/cementogenic differentiation of hPDLSCs <I>in vitro</I>, and the <I>in vivo</I> potential of hPDLSCs to form mineralized cementum and organized PDL tissue was down‐regulated following treatment with rhBMP‐2. Collagen synthesis, which plays a crucial role in the regeneration of cementum and the periodontal attachment, was significantly reduced, with associated modification of the relevant mRNA and protein expression profiles.</P><P><B>Conclusion: </B> In summary, the findings of the present study suggest that enhanced adipogenic differentiation and inhibition of collagen synthesis by hPDLSCs appear to be partly responsible for the minimal effect of rhBMP‐2 on cementum and PDL tissue regeneration by hPDLSCs.</P>

Kinetics and Mechanism of Nucleophilic Displacement Reactions of Y-Substituted Phenyl Benzoates with Cyanide

Song-I Kim,Eun-Hee Kim,Ik-Hwan Um 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.3

Second-order rate constants (kCN‒) have been measured for nucleophilic substitution reactions of Y-substituted phenyl benzoates (1a-r) with CN‒ ion in 80 mol % H2O/20 mol % DMSO at 25.0 ± 0.1 oC. The Brønsted-type plot is linear with βlg = ‒0.49, a typical βlg value for reactions reported to proceed through a concerted mechanism. Hammett plots correlated with σo and σ‒ constants exhibit many scattered points. In contrast, the Yukawa-Tsuno plot for the same reaction exhibits excellent linearity with ρY = 1.37 and r = 0.34, indicating that a negative charge develops partially on the oxygen atom of the leaving aryloxide in the rate-determining step (RDS). Although two different mechanisms are plausible (i.e., a concerted mechanism and a stepwise pathway in which expulsion of the leaving group occurs at the RDS), the reaction has been concluded to proceed through a concerted mechanism on the basis of the magnitude of βlg and ρY values.

Nucleophilic Substitution Reactions of Y-Substituted-Phenyl Benzoates with Potassium Ethoxide in Anhydrous Ethanol: Reaction Mechanism and Role of K+ Ion

Song-I Kim,Hyo-Jin Cho,엄익환 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.1

Pseudo-first-order rate constants (k obsd ) have been measured spectrophotometrically for the reactions of Y- substituted-phenyl benzoates (5a-j) with potassium ethoxide (EtOK) in anhydrous ethanol at 25.0 ± 0.1 o C. The plots of k obsd vs. [EtOK] curve upward regardless of the electronic nature of the substituent Y in the leaving group. Dissection of k obsd into the second-order rate constants for the reactions with the dissociated EtO – and ion-paired EtOK (i.e., k EtO- and k EtOK , respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated EtO – . The Brønsted-type plots for the reactions with the dissociated EtO – and ion-paired EtOK exhibit highly scattered points with βlg = –0.5 ± 0.1. The Hammett plots correlated with σo constants result in excellent linear correlations, indicating that no negative charge develops on the O atom of the leaving Y- substituted-phenoxide ion in transition state. Thus, it has been concluded that the reactions with the dissociated EtO – and ion-paired EtOK proceed through a stepwise mechanism, in which departure of the leaving group occurs after the RDS, and that K + ion catalyzes the reactions by increasing the electrophilicity of the reaction center through a four-membered cyclic TS structure.

Kinetics and Mechanism of Michael-type Reactions of Ethyl Propiolate with Alicyclic Secondary Amines in H2O and MeCN: Solvent Effect on Reactivity and Transition-State Structure

Song-I Kim,Hye-Won Baek,엄익환 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

The amines studied in this study are less reactive toward ethyl propiolate (3) in MeCN than in H2O although they are 7 to 9 pKa units more basic in the aprotic solvent. The reactivity of morpholine and deuterated morpholine toward 3 is found to be identical, indicating that proton transfer occurs after rate-determining step (RDS). The fact that kinetic isotope effect is absent excludes a stepwise mechanism in which proton transfer occurs in RDS as well as a concerted mechanism in which nucleophilic attack and proton transfer occur concertedly through a 4-membered cyclic transition state (TS). Thus, the reactions have been concluded to proceed through a stepwise mechanism in which proton transfer occurs after RDS. Brønsted-type plots are linear with small βnuc values, i.e., βnuc = 0.29 in H2O and βnuc = 0.51 in MeCN, indicating that bond formation is not advanced significantly in RDS. The small βnuc value also supports the conclusion drawn from the study of kinetic isotope effect.

Kinetic Study on Nucleophilic Substitution Reactions of 4-Nitrophenyl X-Substituted- Benzoates with Potassium Ethoxide: Reaction Mechanism and Role of K+ Ion

Song-I Kim,Min-Young Kim,엄익환 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.1

A kinetic study on nucleophilic substitution reactions of 4-nitrophenyl X-substituted-benzoates (7a-i) with EtOK in anhydrous ethanol at 25.0 ± 0.1 o C is reported. The plots of pseudo-first-order rate constants (k obsd ) vs. [EtOK] curve upward. Dissection of k obsd into the second-order rate constants for the reactions with the dissociated EtO – and ion-paired EtOK (i.e., k EtO- and k EtOK , respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated EtO – . Hammett plots for the reactions of 7a-i with the dissociated EtO – and ion-paired EtOK exhibit excellent linear correlations with  X = 3.00 and 2.47, respectively. The reactions have been suggested to proceed through a stepwise mechanism in which departure of the leaving-group occurs after the RDS. The correlation of the k EtOK /k EtO ratio with the σX constants exhibits excellent linearity with a slope of –0.53. It is concluded that the ion-paired EtOK catalyzes the reaction by increasing the electrophilicity of the reaction center rather than by enhancing the nucleofugality of the leaving group.

Kinetics and Mechanism of Nucleophilic Displacement Reactions of Y-Substituted Phenyl Benzoates with Cyanide Ion

Kim, Song-I,Kim, Eun-Hee,Um, Ik-Hwan Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.3

Second-order rate constants ($k_{CN^-}$) have been measured for nucleophilic substitution reactions of Y-substituted phenyl benzoates (1a-r) with $CN^-$ ion in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The Br${\o}$nsted-type plot is linear with ${\beta}_{1g}$ = -0.49, a typical ${\beta}_{1g}$ value for reactions reported to proceed through a concerted mechanism. Hammett plots correlated with ${\sigma}^{\circ}$ and ${\sigma}^-$ constants exhibit many scattered points. In contrast, the Yukawa-Tsuno plot for the same reaction exhibits excellent linearity with ${\rho}_Y$ = 1.37 and r = 0.34, indicating that a negative charge develops partially on the oxygen atom of the leaving aryloxide in the rate-determining step (RDS). Although two different mechanisms are plausible (i.e., a concerted mechanism and a stepwise pathway in which expulsion of the leaving group occurs at the RDS), the reaction has been concluded to proceed through a concerted mechanism on the basis of the magnitude of ${\beta}_{1g}$ and ${\rho}_Y$ values.

Visibility of Internal Target Volume of Dynamic Tumors in Free-breathing Cone-beam Computed Tomography for Image Guided Radiation Therapy

Kevin I. Kauweloa,Justin C. Park,Ajay Sandhu,Todd Pawlick,Bongyong Song,William Y. Song 한국의학물리학회 2013 의학물리 Vol.24 No.4

Respiratory-induced dynamic tumors render free-breathing cone-beam computed tomography (FBCBCT) imageswith motion artifacts complicating the task of quantifying the internal target volume (ITV). The purpose of thispaper is to study the visibility of the revealed ITV when the imaging dose parameters, such as the kVp and mAs,are varied. The TrilogyTM linear accelerator with an On-Board Imaging (OBITM) system was used to acquirelow-imaging-dose-mode (LIDM: 110 kVp, 20 mA, 20 ms/frame) and high-imaging-dose-mode (HIDM: 125 kVp,80 mA, 25 ms/frame) FBCBCT images of a 3-cm diameter sphere (density=0.855 g/cm3) moving in accordanceto various sinusoidal breathing patterns, each with an unique inhalation-to-exhalation (I/E) ratio, amplitude, andperiod. In terms of image ITV contrast, there was a small overall average change of the ITV contrast when goingfrom HIDM to LIDM of 6.5±5.1% for all breathing patterns. As for the ITV visible volume measurements, therewas an insignificant difference between the ITV of both the LIDM- and HIDM-FBCBCT images with an averagedifference of 0.5±0.5%, for all cases, despite the large difference in the imaging dose (approximately five-folddifference of ~0.8 and 4 cGy/scan). That indicates that the ITV visibility is not very sensitive to changes in imagingdose. However, both of the FBCBCT consistently underestimated the true ITV dimensions by up to 34.8%irrespective of the imaging dose mode due to significant motion artifacts, and thus, this imaging technique isnot adequate to accurately visualize the ITV for image guidance. Due to the insignificant impact of imaging doseon ITV visibility, a plausible, alternative strategy would be to acquire more X-ray projections at the LIDM settingto allow 4DCBCT imaging to better define the ITV, and at the same time, maintain a reasonable imaging dose,i.e., comparable to a single HIDM-FBCBCT scan.

Kinetics and Mechanism of Michael-type Reactions of Ethyl Propiolate with Alicyclic Secondary Amines in H₂O and MeCN: Solvent Effect on Reactivity and Transition-State Structure

Kim, Song-I,Baek, Hye-Won,Um, Ik-Hwan Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.12

The amines studied in this study are less reactive toward ethyl propiolate (3) in MeCN than in H$_2$O although they are 7 to 9 pK$_a$ units more basic in the aprotic solvent. The reactivity of morpholine and deuterated morpholine toward 3 is found to be identical, indicating that proton transfer occurs after rate-determining step (RDS). The fact that kinetic isotope effect is absent excludes a stepwise mechanism in which proton transfer occurs in RDS as well as a concerted mechanism in which nucleophilic attack and proton transfer occur concertedly through a 4-membered cyclic transition state (TS). Thus, the reactions have been concluded to proceed through a stepwise mechanism in which proton transfer occurs after RDS. Brønsted-type plots are linear with small ${\beta}_{nuc}$ values, i.e., ${\beta}_{nuc}$ = 0.29 in H$_2$O and ${\beta}_{nuc}$ = 0.51 in MeCN, indicating that bond formation is not advanced significantly in RDS. The small ${\beta}_{nuc}$ value also supports the conclusion drawn from the study of kinetic isotope effect.

Nucleophilic Substitution Reactions of Y-Substituted-Phenyl Benzoates with Potassium Ethoxide in Anhydrous Ethanol: Reaction Mechanism and Role of K⁺ Ion

Kim, Song-I,Cho, Hyo-Jin,Um, Ik-Hwan Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.1

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the reactions of Y-substituted-phenyl benzoates (5a-j) with potassium ethoxide (EtOK) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [EtOK] curve upward regardless of the electronic nature of the substituent Y in the leaving group. Dissection of $k_{obsd}$ into the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOK (i.e., $k_{EtO^-}$ and $k_{EtOK}$, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. The Br${\phi}$nsted-type plots for the reactions with the dissociated $EtO^-$ and ion-paired EtOK exhibit highly scattered points with ${\beta}_{lg}$ = -$0.5{\pm}0.1$. The Hammett plots correlated with ${\sigma}^o$ constants result in excellent linear correlations, indicating that no negative charge develops on the O atom of the leaving Y-substituted-phenoxide ion in transition state. Thus, it has been concluded that the reactions with the dissociated $EtO^-$ and ion-paired EtOK proceed through a stepwise mechanism, in which departure of the leaving group occurs after the RDS, and that $K^+$ ion catalyzes the reactions by increasing the electrophilicity of the reaction center through a four-membered cyclic TS structure.

The effect of sulphur amount in sulphurization stage on secondary phases in Cu2SnS3(CTS) films

Sozak Işil Merve Songür,Yorulmaz Uğur,Atay Ferhunde,Akyüz Idris 한국물리학회 2021 Current Applied Physics Vol.26 No.-

Cu2SnS3 is a promising absorber for green thin film solar cells because of its suitable optoelectrical properties and environment friendly components. In this study, CTS films were prepared by sulphurization of stacked metallic precursors deposited by thermal evaporation. Some physical properties were investigated by changing the amount of sulphur used in sulphurization stage. Highly crystalline tetragonal-CTS phase was obtained for all samples. However, Cu3SnS4 and CuS secondary phases were also determined at low amounts. Cu/Sn ratio approached to desired stoichiometry of CTS with increasing sulphur amount. Absorption spectra showed that there are two discrete absorption regions that are related to tetragonal-CTS and secondary phases. Thickness and optical constants were determined using spectroscopic ellipsometry. Atomic force microscope was used to evaluate the effects of sulphur amount on the morphology of CTS films. As a result, this study suggests a way of minimizing the secondary phases to obtain single phase tetragonal CTS.