Publications by authors named "Chang-Woo Cho"

33 Publications

Deep Neural Network-Based Prediction of the Risk of Advanced Colorectal Neoplasia.

Gut Liver 2021 Jan;15(1):85-91

Division of Gastroenterology, Department of Internal Medicine and Gastrointestinal Cancer Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.

Background/aims: Risk prediction models using a deep neural network (DNN) have not been reported to predict the risk of advanced colorectal neoplasia (ACRN). The aim of this study was to compare DNN models with simple clinical score models to predict the risk of ACRN in colorectal cancer screening.

Methods: Databases of screening colonoscopy from Kangbuk Samsung Hospital (n=121,794) and Kyung Hee University Hospital at Gangdong (n=3,728) were used to develop DNN-based prediction models. Two DNN models, the Asian-Pacific Colorectal Screening (APCS) model and the Korean Colorectal Screening (KCS) model, were developed and compared with two simple score models using logistic regression methods to predict the risk of ACRN. The areas under the receiver operating characteristic curves (AUCs) of the models were compared in internal and external validation databases.

Results: In the internal validation set, the AUCs of DNN model 1 and the APCS score model were 0.713 and 0.662 (p<0.001), respectively, and the AUCs of DNN model 2 and the KCS score model were 0.730 and 0.667 (p<0.001), respectively. However, in the external validation set, the prediction performances were not significantly different between the two DNN models and the corresponding APCS and KCS score models (both p>0.1).

Conclusions: Simple score models for the risk prediction of ACRN are as useful as DNN-based models when input variables are limited. However, further studies on this issue are warranted to predict the risk of ACRN in colorectal cancer screening because DNN-based models are currently under improvement.
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http://dx.doi.org/10.5009/gnl19334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7817932PMC
January 2021

Application of deep learning to predict advanced neoplasia using big clinical data in colorectal cancer screening of asymptomatic adults.

Korean J Intern Med 2020 Oct 23. Epub 2020 Oct 23.

Division of Gastroenterology, Department of Internal Medicine and Gastrointestinal Cancer Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.

Background/aims: We aimed to develop a deep learning model for the prediction of the risk of advanced colorectal neoplasia (ACRN) in asymptomatic adults, based on which colorectal cancer screening could be customized.

Methods: We collected data on 26 clinical and laboratory parameters, including age, sex, smoking status, body mass index, complete blood count, blood chemistry, and tumor marker, from 70,336 first-time colonoscopy screening recipients. For reference, we used a logistic regression (LR) model with nine variables manually selected from the 26 variables. A deep neural network (DNN) model was developed using all 26 variables. The area under the receiver operating characteristic curve (AUC), sensitivity, and specificity of the models were compared in a randomly split validation group.

Results: In comparison with the LR model (AUC, 0.724; 95% confidence interval [CI], 0.684 to 0.765), the DNN model (AUC, 0.760; 95% CI, 0.724 to 0.795) demonstrated significantly improved performance with respect to the prediction of ACRN (p < 0.001). At a sensitivity of 90%, the specificity significantly increased with the application of the DNN model (41.0%) in comparison with the LR model (26.5%) (p < 0.001), indicating that the colonoscopy workload required to detect the same number of ACRNs could be reduced by 20%.

Conclusions: The application of DNN to big clinical data could significantly improve the prediction of ACRNs in comparison with the LR model, potentially realizing further customization by utilizing large quantities and various types of biomedical information.
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http://dx.doi.org/10.3904/kjim.2020.020DOI Listing
October 2020

Z-vestigial nematic order due to superconducting fluctuations in the doped topological insulators NbBiSe and CuBiSe.

Nat Commun 2020 Jun 16;11(1):3056. Epub 2020 Jun 16.

Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

A state of matter with a multi-component order parameter can give rise to vestigial order. In the vestigial phase, the primary order is only partially melted, leaving a remaining symmetry breaking behind, an effect driven by strong classical or quantum fluctuations. Vestigial states due to primary spin and charge-density-wave order have been discussed in iron-based and cuprate materials. Here we present the observation of a partially melted superconductivity in which pairing fluctuations condense at a separate phase transition and form a nematic state with broken Z, i.e., three-state Potts-model symmetry. Thermal expansion, specific heat and magnetization measurements of the doped topological insulators NbBiSe and CuBiSe reveal that this symmetry breaking occurs at [Formula: see text] above [Formula: see text], along with an onset of superconducting fluctuations. Thus, before Cooper pairs establish long-range coherence at T, they fluctuate in a way that breaks the rotational invariance at T and induces a crystalline distortion.
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http://dx.doi.org/10.1038/s41467-020-16871-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298044PMC
June 2020

Synthesis of α-Trifluoromethylthio-α,β-Unsaturated Carbonyl Compounds by DABCO-Mediated Electrophilic Trifluoromethylthiolation with -SCF-Dibenzenesulfonimide.

J Org Chem 2020 Jun 22;85(11):7077-7085. Epub 2020 May 22.

Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 41566, Republic of Korea.

A DABCO-mediated electrophilic α-trifluoromethylthiolation of α,β-unsaturated carbonyl compounds comprising no β-substituents has been achieved using -trifluoromethylthio-dibenzenesulfonimide as the SCF source. The direct trifluoromethylthiolation provides the corresponding α-trifluoromethylthio-α,β-unsaturated carbonyl products in good yields (up to 88%). Furthermore, the vinyl group in the α-trifluoromethylthio-α,β-unsaturated carbonyl product was successfully transformed into diverse functional groups in good to excellent yields (70-95%) by reactions such as epoxidation, aziridination, hydrocyanation, and hydrogenation.
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http://dx.doi.org/10.1021/acs.joc.0c00448DOI Listing
June 2020

Observation of a thermoelectric Hall plateau in the extreme quantum limit.

Nat Commun 2020 Feb 25;11(1):1046. Epub 2020 Feb 25.

Department of Physics, Southern University of Science and Technology, 518055, Shenzhen, China.

The thermoelectric Hall effect is the generation of a transverse heat current upon applying an electric field in the presence of a magnetic field. Here, we demonstrate that the thermoelectric Hall conductivity α in the three-dimensional Dirac semimetal ZrTe acquires a robust plateau in the extreme quantum limit of magnetic field. The plateau value is independent of the field strength, disorder strength, carrier concentration, or carrier sign. We explain this plateau theoretically and show that it is a unique signature of three-dimensional Dirac or Weyl electrons in the extreme quantum limit. We further find that other thermoelectric coefficients, such as the thermopower and Nernst coefficient, are greatly enhanced over their zero-field values even at relatively low fields.
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http://dx.doi.org/10.1038/s41467-020-14819-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7042294PMC
February 2020

Spectroscopic fingerprint of chiral Majorana modes at the edge of a quantum anomalous Hall insulator/superconductor heterostructure.

Proc Natl Acad Sci U S A 2020 Jan 18;117(1):238-242. Epub 2019 Dec 18.

Department of Physics, The Hong Kong University of Science and Technology, Kowloon, Hong Kong;

With the recent discovery of the quantum anomalous Hall insulator (QAHI), which exhibits the conductive quantum Hall edge states without external magnetic field, it becomes possible to create a topological superconductor (SC) by introducing superconductivity into these edge states. In this case, 2 distinct topological superconducting phases with 1 or 2 chiral Majorana edge modes were theoretically predicted, characterized by Chern numbers (N) of 1 and 2, respectively. We present spectroscopic evidence from Andreev reflection experiments for the presence of chiral Majorana modes in an Nb/(CrBiSb)Te heterostructure with distinct signatures attributed to 2 different topological superconducting phases. The results are in qualitatively good agreement with the theoretical predictions.
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http://dx.doi.org/10.1073/pnas.1910967117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6955289PMC
January 2020

A Combined Experimental and Theoretical Study of the Versatile Reactivity of an Oxocerium(IV) Complex: Concerted Versus Reductive Addition.

Chemistry 2019 Aug 26;25(46):10834-10839. Epub 2019 Jul 26.

LPCNO, Université de Toulouse, 31077, Toulouse, France.

A combined experimental and theoretical investigation on the cerium(IV) oxo complex [(L ) Ce(=O)(H O)]⋅MeC(O)NH (1; L =[Co(η -C H ){P(O)(OEt) } ] ) demonstrates that the intermediate spin-state nature of the ground state of the cerium complex is responsible for the versatility of its reactivity towards small molecules such as CO, CO , SO , and NO. CASSCF calculations together with magnetic susceptibility measurements indicate that the ground state of the cerium complex is of multiconfigurational character and comprised of 74 % of Ce and 26 % of Ce . The latter is found to be responsible for its reductive addition behavior towards CO, SO , and NO. This is the first report to date on the influence of the multiconfigurational ground state on the reactivity of a metal-oxo complex.
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http://dx.doi.org/10.1002/chem.201903035DOI Listing
August 2019

Organocatalytic enantioselective synthesis of acyclic pyrimidine nucleosides by aza-Michael reaction.

Org Biomol Chem 2018 12;16(48):9477-9486

Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 41566, Republic of Korea.

An efficient diarylprolinol triphenylsilyl ether-catalyzed enantioselective aza-Michael reaction of pyrimidines as N-centered nucleophiles to α,β-unsaturated aldehydes, followed by reduction, provided chiral acyclic pyrimidine nucleosides in good yields (51-78% yields for two steps) and excellent enantioselectivities (91-98% ee). In addition, the chiral acyclic pyrimidine nucleoside having the tert-butyldiphenylsilyl-protected hydroxyl substituent was successfully applied to the synthesis of the corresponding chiral cyclic pyrimidine nucleoside analogue bearing the tetrahydrofuranyl ring.
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http://dx.doi.org/10.1039/c8ob02754dDOI Listing
December 2018

WITHDRAWN: Application of deep learning to predict advanced neoplasia using big clinical data in colorectal cancer screening of asymptomatic adults.

Gastrointest Endosc 2018 Nov 4. Epub 2018 Nov 4.

Division of Gastroenterology, Department of Internal Medicine and Gastrointestinal Cancer Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine.

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.
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http://dx.doi.org/10.1016/j.gie.2018.10.041DOI Listing
November 2018

5-Bromo-4',5'-bis(dimethylamino)fluorescein: Synthesis and Photophysical Studies.

Molecules 2018 Jan 20;23(1). Epub 2018 Jan 20.

Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 41566, Korea.

In this study, three new fluorescein derivatives-5-bromo-4',5'-dinitrofluorescein (), 5-bromo-4',5'-diaminofluorescein (), and 5-bromo-4',5'-bis(dimethylamino)fluorescein ()-were synthesized and their pH-dependent protolytic equilibria were investigated. In particular, exhibited pH-dependent fluorescence, showing strong emission only at pH 3-6. bears a bromine moiety and thus, can be used in various cross-coupling reactions to prepare derivatives and take advantage of its unique emission properties. To confirm this, the Suzuki and Sonogashira reactions of with phenylboronic acid and phenylacetylene, respectively, were performed, and the desired products were successfully obtained.
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http://dx.doi.org/10.3390/molecules23010219DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6017165PMC
January 2018

Catalytic enantioselective synthesis of carboxy-substituted 2-isoxazolines by cascade oxa-Michael-cyclization.

Org Biomol Chem 2018 01;16(4):657-664

Department of Chemistry and Green-Nano Materials Research Center, Kyungpook National University, Daegu 41566, Republic of Korea.

An efficient quinidine-based phase-transfer-catalyzed enantioselective cascade oxa-Michael-cyclization reaction of hydroxylamine with various β-carboxy-substituted α,β-unsaturated ketones has been achieved for the preparation of chiral carboxy-substituted 2-isoxazolines. This cascade reaction provided the desired products in good yields (up to 98%) with excellent enantioselectivities (91-96% ee). In addition, the cascade reaction was effectively applied to the first catalytic asymmetric synthesis of the herbicide (S)-methiozolin.
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http://dx.doi.org/10.1039/c7ob02722bDOI Listing
January 2018

Thermodynamic Evidence for the Fulde-Ferrell-Larkin-Ovchinnikov State in the KFe_{2}As_{2} Superconductor.

Phys Rev Lett 2017 Nov 20;119(21):217002. Epub 2017 Nov 20.

Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.

We investigate the magnetic phase diagram near the upper critical field of KFe_{2}As_{2} by magnetic torque and specific heat experiments using a high-resolution piezorotary positioner to precisely control the parallel alignment of the magnetic field with respect to the FeAs layers. We observe a clear double transition when the field is strictly aligned in the plane and a characteristic upturn of the upper critical field line, which goes far beyond the Pauli limit at 4.8 T. This provides firm evidence that a Fulde-Ferrell-Larkin-Ovchinnikov state exists in this iron-based KFe_{2}As_{2} superconductor.
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http://dx.doi.org/10.1103/PhysRevLett.119.217002DOI Listing
November 2017

Isolation and Characterization of Few-Layer Manganese Thiophosphite.

ACS Nano 2017 11 16;11(11):11330-11336. Epub 2017 Oct 16.

Department of Physics and Engineering Physics, Tulane University , New Orleans, Louisiana 70118, United States.

This work reports an experimental study on an antiferromagnetic honeycomb lattice of MnPS that couples the valley degree of freedom to a macroscopic antiferromagnetic order. The crystal structure of MnPS is identified by high-resolution scanning transmission electron microscopy. Layer-dependent angle-resolved polarized Raman fingerprints of the MnPS crystal are obtained, and the Raman peak at 383 cm exhibits 100% polarity. Temperature dependences of anisotropic magnetic susceptibility of the MnPS crystal are measured in a superconducting quantum interference device. Anisotropic behaviors of the magnetic moment are explored on the basis of the mean field approximation model. Ambipolar electronic conducting channels in MnPS are realized by the liquid gating technique. The conducting channel of MnPS offers a platform for exploring the spin/valleytronics and magnetic orders in 2D limitation.
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http://dx.doi.org/10.1021/acsnano.7b05856DOI Listing
November 2017

Which Technique Is Better Option for C3 Segment in Multilevel Open-Door Laminoplasty of the Cervical Spine?: Laminectomy Versus Laminoplasty.

Spine (Phila Pa 1976) 2017 Jul;42(14):E833-E840

Department of Orthopaedic Surgery, Yeungnam University Medical Center, Yeungnam University College of Medicine, Daegu, Korea (Republic of).

Study Design: A post-hoc comparative study.

Objective: To evaluate postoperative clinical, radiological, and surgical outcomes after laminoplasty (LP) involving the C3 segment and to compare outcomes with those of patients who underwent LP with C3 laminectomy (LN).

Summary Of Background Data: In many of the pathologies that require LP involving C3 segment, most spine surgeons perform LP at C3 and other cervical segments. Considering the peculiarities of the C2-C3 level, spine surgeons should take into account those in LP involving the C3 segment, but the particular aspects of the C2-C3 levels have not been fully evaluated.

Methods: Of 93 patients, 66 patients (39 in group A, LP involving C3; 27 in group B, LP with C3 LN) were enrolled in the study. The primary outcome measure was pain intensity of the posterior neck measured with visual analog scale. Secondary endpoints included the following: (1) radiologic outcomes based on the cervical range of motion and rate of bony impingement and spontaneous fusion between C2 and C3, (2) clinical outcomes based on the 12-item short-form health survey and Japanese Orthopedic Association scale, and (3) surgical outcomes.

Results: The primary end-point of the present study, posterior neck pain, exhibited a greater improvement in the group with C3 LN than in the group with C3 LP at 6 months and 1 year after surgery (P = 0.03 and 0.01, respectively). The cervical range of motion of C3 LN group was significantly greater than C3 LP group at postoperative 1 year (P = 0.02). Radiologic evidences of bony impingement and spontaneous fusion between C2 and C3 were significantly greater in C3 LP group than in C3 LN group. Clinical outcomes and surgical outcomes did not differ significantly between groups.

Conclusion: We recommend performing LN instead of LP for the C3 segment in cases requiring multilevel LP surgery involving C3.

Level Of Evidence: 3.
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http://dx.doi.org/10.1097/BRS.0000000000001974DOI Listing
July 2017

Efficient Syntheses of 1,2,3-Triazoloamide Derivatives Using Solid- and Solution-Phase Synthetic Approaches.

Molecules 2015 Nov 5;20(11):19984-20013. Epub 2015 Nov 5.

College of Pharmacy, Research Institute of Pharmaceutical Sciences, Kyungpook National University, 80 Daehak-ro, Buk-gu, Daegu 702-701, Korea.

Efficient synthetic routes for the preparation of secondary and tertiary 1,2,3-triazoloamide derivatives were developed. A secondary α-1,2,3-triazoloamide library was constructed and expanded by a previously developed solid-phase synthetic route and a tertiary 1,2,3-triazoloamide library was constructed by a parallel solution-phase synthetic route. The synthetic routes rely on amide formation with secondary amines and chloro-acid chlorides; SN2 reaction with sodium azide; and the selective [3 + 2] Hüisgen cycloaddition with appropriate terminal alkynes. The target secondary and tertiary 1,2,3-triazoloamide derivatives were obtained with three-diversity points in excellent overall yields and purities using the reported solid- and solution-phase synthetic routes, respectively.
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http://dx.doi.org/10.3390/molecules201119673DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6332172PMC
November 2015

Enantioselective Phase-Transfer-Catalyzed Synthesis of Chiral N-Substituted 3,3-Dinitroazetidines by Aza-Michael Reaction.

J Org Chem 2015 Nov 11;80(22):11435-40. Epub 2015 Nov 11.

Department of Chemistry, Kyungpook National University , Daegu 702-701, Republic of Korea.

An efficient and highly enantioselective phase-transfer-catalyzed aza-Michael reaction of 3,3-dinitroazetidine, as N-centered nucleophile, to α,β-unsaturated ketones has been achieved using a quinidine-based phase-transfer catalyst (0.5-1 mol %), providing chiral N-substituted 3,3-dinitroazetidines in good yields (up to 99%) and excellent enantioselectivities (90-95% ee). This is the first example of the use of azetidines as N-centered nucleophiles in catalytic enantioselective aza-Michael reactions.
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http://dx.doi.org/10.1021/acs.joc.5b02124DOI Listing
November 2015

A two-photon fluorescent probe for lysosomal zinc ions.

Chem Commun (Camb) 2016 Jan;52(1):124-7

Department of Chemistry, POSTECH, Pohang 790-784, Republic of Korea.

The selective detection of zinc ions in lysosomes over that in cytosol is achieved with a fluorescent probe, which enabled the fluorescence imaging of endogenous zinc ions in lysosomes of NIH 3T3 cells as well as mouse hippocampal tissues by two-photon microscopy under excitation at 900 nm.
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http://dx.doi.org/10.1039/c5cc06976aDOI Listing
January 2016

Recyclable rhodium nanoparticles: green hydrothermal synthesis, characterization, and highly catalytic performance in reduction of nitroarenes.

J Nanosci Nanotechnol 2013 Nov;13(11):7477-81

Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 609-735, Korea.

In this work, rhodium nanoparticles were synthesized using hydrothermal method that is simple and easy to manipulate reaction and use nontoxic supercritical water. The rhodium nanoparticles were formed in uniform size and shape. These Rh NPs also acted as a efficient heterogenous catalyst in reduction of 4-nitrophenol to 4-aminophenol. Moreover, the rhodium nanoparticles can be recycled without any loss in catalytic activity, and showed highly catalytic activity for various nitroarenes. Therefore, this method will contribute greatly to the development of environmental field and be suitable for use in the industry.
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http://dx.doi.org/10.1166/jnn.2013.7903DOI Listing
November 2013

Overexpression of VrUBC1, a Mung Bean E2 Ubiquitin-Conjugating Enzyme, Enhances Osmotic Stress Tolerance in Arabidopsis.

PLoS One 2013 18;8(6):e66056. Epub 2013 Jun 18.

Department of Genetic Engineering, College of Natural Resources and Life Science, Dong-A University, Busan, Republic of Korea.

The ubiquitin conjugating enzyme E2 (UBC E2) mediates selective ubiquitination, acting with E1 and E3 enzymes to designate specific proteins for subsequent degradation. In the present study, we characterized the function of the mung bean VrUBC1 gene (Vigna radiata UBC 1). RNA gel-blot analysis showed that VrUBC1 mRNA expression was induced by either dehydration, high salinity or by the exogenous abscisic acid (ABA), but not by low temperature or wounding. Biochemical studies of VrUBC1 recombinant protein and complementation of yeast ubc4/5 by VrUBC1 revealed that VrUBC1 encodes a functional UBC E2. To understand the function of this gene in development and plant responses to osmotic stresses, we overexpressed VrUBC1 in Arabidopsis (Arabidopsis thaliana). The VrUBC1-overexpressing plants displayed highly sensitive responses to ABA and osmotic stress during germination, enhanced ABA- or salt-induced stomatal closing, and increased drought stress tolerance. The expression levels of a number of key ABA signaling genes were increased in VrUBC1-overexpressing plants compared to the wild-type plants. Yeast two-hybrid and bimolecular fluorescence complementation demonstrated that VrUBC1 interacts with AtVBP1 (A. thalianaVrUBC1 Binding Partner 1), a C3HC4-type RING E3 ligase. Overall, these results demonstrate that VrUBC1 plays a positive role in osmotic stress tolerance through transcriptional regulation of ABA-related genes and possibly through interaction with a novel RING E3 ligase.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0066056PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3688854PMC
October 2017

Cinchona-based primary amine-catalyzed asymmetric cascade aza-Michael-aldol reactions of enones with 2-(1H-pyrrol-2-yl)-2-oxoacetates: synthesis of chiral pyrrolizines with multistereocenters.

J Org Chem 2013 Apr 27;78(7):3306-12. Epub 2013 Feb 27.

Department of Chemistry, Kyungpook National University, Daegu 702-701, Republic of Korea.

Cinchona-based primary amine-catalyzed cascade aza-Michael-aldol reactions of α,β-unsaturated ketones with 2-(1H-pyrrol-2-yl)-2-oxoacetates provided highly functionalized chiral pyrrolizines bearing multistereocenters including a chiral quaternary carbon center in good yields (up to 92%) with excellent levels of stereocontrol (90-95% ee, >20:1 dr in all cases). The ketone group in the cascade product was asymmetrically reduced to chiral secondary hydroxyl groups in good yields.
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http://dx.doi.org/10.1021/jo4001614DOI Listing
April 2013

Organocatalytic enantioselective formal synthesis of bromopyrrole alkaloids via aza-Michael addition.

Org Biomol Chem 2011 Oct 27;9(22):7734-41. Epub 2011 Sep 27.

Department of Chemistry, Kyungpook National University, Daegu, Republic of Korea.

An unprecedented organocatalytic enantioselective formal synthesis of bromopyrrole alkaloid natural products is reported. An organocatalytic aza-Michael addition using pyrroles as the N-centered nucleophile is utilized as the enantioselective step to construct the nitrogen-substituted stereogenic carbon center in bromopyrrole alkaloids in good yield and excellent enantioselectivity. The aza-Michael product is converted via lactamization using a Staudinger-type reductive cyclization to the key intermediate, which was previously used in the total synthesis of bromopyrrole alkaloid natural products.
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http://dx.doi.org/10.1039/c1ob06078cDOI Listing
October 2011

Exploration for the salt stress tolerance genes from a salt-treated halophyte, Suaeda asparagoides.

Plant Cell Rep 2012 Jan 28;31(1):35-48. Epub 2011 Aug 28.

BK21 Center for Silver-Bio Industrialization, College of Natural Resources and Life Science, Dong-A University, Busan, Republic of Korea.

Salinity stress severely affects plant growth and development causing crop loss worldwide. Suaeda asparagoides is a salt-marsh euhalophyte widely distributed in southwestern foreshore of Korea. To isolate salt tolerance genes from S. asparagoides, we constructed a cDNA library from leaf tissues of S. asparagoides that was treated with 200 mM NaCl. A total of 1,056 clones were randomly selected for EST sequencing, and 932 of them produced readable sequence. By sequence analysis, we identified 538 unigenes and registered each in National Center for Biotechnology Information. The 80 salt stress related genes were selected to study their differential expression. Reverse transcription-PCR and Northern blot analysis revealed that 23 genes were differentially expressed under the high salinity stress conditions in S. asparagoides. They are functionally diverse including transport, signal transduction, transcription factor, metabolism and stress associated protein, and unknown function. Among them dehydrin (SaDhn) and RNA binding protein (SaRBP1) were examined for their abiotic stress tolerance in yeast (Saccharomyces cerevisiae). Yeast overexpressing SaDhn and SaRBP1 showed enhanced tolerance to osmotic, freezing and heat shock stresses. This study provides the evidence that SaRBP1 and SaDhn from S. asparagoides exert abiotic stress tolerance in yeast. Information of salt stress related genes from S. asparagoides would contribute for the accumulating genetic resources to improve osmotic tolerance in plants.
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http://dx.doi.org/10.1007/s00299-011-1137-4DOI Listing
January 2012

Organocatalytic asymmetric synthesis of chiral pyrrolizines by cascade conjugate addition-aldol reactions.

Org Lett 2010 Oct;12(19):4352-5

Department of Chemistry, Kyungpook National University, Daegu 702-701, Republic of Korea.

As the first N-centered heteroaromatic nucleophile for organocatalytic cascade reactions, pyrroles underwent the enantio- and diastereoselective organocatalytic cascade conjugate addition-aldol reactions of α,β-unsaturated aldehydes that afford the highly functionalized chiral pyrrolizines bearing three consecutive stereocenters in good yields, high enantioselectivities (90-98% ee), and excellent diastereoselectivities (>20:1 dr in all cases).
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http://dx.doi.org/10.1021/ol101811cDOI Listing
October 2010

Molecular cloning and characterization of the soybean DEAD-box RNA helicase gene induced by low temperature and high salinity stress.

Gene 2009 Aug 20;443(1-2):91-9. Epub 2009 May 20.

BK21 Center for Silver-Bio Industrialization, College of Natural Resources and Life Science, Dong-A University, Busan 604-714, Republic of Korea.

A novel gene encoding a DEAD-box RNA helicase designated as GmRH was isolated from soybean. Amino acid sequence alignment and phylogenetic tree analysis revealed a close relationship between GmRH and other orthologous DEAD-box RNA helicases from other plant species. Structural motif analysis revealed that the bipartite lysine rich nuclear localization signal (NLS) is present in the N-terminal variable region of GmRH and that there are ten conserved motifs found in DEAD-box RNA helicase proteins. Southern blot analysis revealed the presence of 2 copies of GmRH in the soybean genome. Northern blot analysis demonstrated that the RNA expression of the GmRH was induced during low temperature or high salinity stress, but not by the exogenous application of abscisic acid or drought stress. Subcellular localization studies showed that GmRH((1-355))-GFP is localized in the nucleus, whereas GmRH((130-355))-GFP is localized both in the cytoplasm and in the nucleus. This provides the evidence that the N-terminal region predicted as NLS is essential for nuclear targeting of the GmRH protein in the plant cell. Purified GST-GmRH recombinant protein was shown to unwind dsRNA independent of ATP in vitro. Here, we propose that GmRH plays an important role in RNA processing during low temperature and high salinity stresses in plants.
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http://dx.doi.org/10.1016/j.gene.2009.05.005DOI Listing
August 2009

Enantioselective reductive coupling of 1,3-enynes to glyoxalates mediated by hydrogen: asymmetric synthesis of beta,gamma-unsaturated alpha-hydroxy esters.

Org Lett 2007 Sep 18;9(19):3745-8. Epub 2007 Aug 18.

University of Texas at Austin, Department of Chemistry and Biochemistry, Austin, Texas 78712, USA.

Catalytic hydrogenation of 1,3-enynes 1a-8a in the presence of ethyl glyoxalate at ambient pressure and temperature using a rhodium catalyst modified by (R)-(3,5-tBu-4-MeOPh)-MeO-BIPHEP results in highly regio- and enantioselective reductive coupling to furnish the corresponding alpha-hydroxy esters 1b-8b. As demonstrated by the elaboration of alpha-hydroxy ester 1b, the terminal and internal olefin moieties embodied by the diene side chain are subject to selective manipulation, one over the other.
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http://dx.doi.org/10.1021/ol7015548DOI Listing
September 2007

Molecular characterization of the soybean L-asparaginase gene induced by low temperature stress.

Mol Cells 2007 Jun;23(3):280-6

Department of Genetic Engineering, Dong-A University, Busan 604-714, Korea.

L-asparaginase (EC 3.5.1.1) catalyzes the hydrolysis of the amide group of L-asparagine, releasing aspartate and NH4+. We isolated a low temperature-inducible cDNA sequence encoding L-asparaginase from soybean leaves. The full-length L-asparaginase cDNA, designated GmASP1, contains an open reading frame of 1,258 bp coding for a protein of 326 amino acids. Genomic DNA blotting and fluorescence in situ hybridization showed that the soybean genome has two copies of GmASP1. GmASP1 mRNA was induced by low temperature, ABA and NaCl, but not by heat shock or drought stress. E. coli cells expressing recombinant GmASP1 had 3-fold increased L-asparaginase activity. A possible function of L-asparaginase in the early response to low temperature stress is discussed.
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June 2007

Hypolipidemic effect of Salicornia herbacea in animal model of type 2 diabetes mellitus.

Nutr Res Pract 2007 31;1(4):371-5. Epub 2007 Dec 31.

Biohealth Product Research Center, School of Food and Life Science, Institute for Food Sciences, Institute of Biomedical Engineering, Inje University, Gimhae, 621-749, Korea.

To control blood glucose level as close to normal is a major goal of treatment of diabetes mellitus. Hyperglycemia and hyperlipidemia are the major risk factors for cardiovascular complications, the major cause of immature death among the patients with type 2 diabetes. The purpose of this study is to determine the hypoglycemic and hypolipidemic effects of Salicornia herbacea in animal model of type 2 diabetes and to investigate the possible mechanisms for the beneficial effects of S. herbacea. S. herbacea was extracted with 70% ethanol and desalted with 100% ethanol. Three week-old db/db mice (C57BL/KsJ, n=16) were fed AIN-93G semipurified diet or diet containing 1% desalted ethanol extract of S. herbacea for 6 weeks after 1 week of adaptation. Fasting plasma glucose, triglyceride, and total cholesterol were measured by enzymatic methods and blood glycated hemoglobin (HbA(1C)) by the chromatographic method. Body weight and food intake of S. herbacea group were not significantly different from those of the control group. Fasting plasma glucose and blood glycated hemoglobin levels tended to be lowered by S. herbacea treatment. Consumption of S. herbacea extract significantly decreased plasma triglyceride and cholesterol levels (p<0.05). The inhibition of S. herbacea extract against yeast alpha-glucosidase was 31.9% of that of acarbose at the concentration of 0.5 mg/mL in vitro. The inhibitory activity of ethanol extract of S. herbacea against porcine pancreatic lipase was 59.0% of that of orlistat at the concentration of 0.25 mg/mL in vitro. Thus, these results suggest that S. herbacea could be effective in controlling hyperlipidemia by inhibition of pancreatic lipase in animal model of type 2 diabetes.
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http://dx.doi.org/10.4162/nrp.2007.1.4.371DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2849048PMC
July 2011

Phosphine-catalyzed allylic substitution of Morita-Baylis-Hillman acetates: synthesis of N-protected beta-aminophosphonic acid esters.

J Org Chem 2006 Sep;71(20):7892-4

College of Pharmacy, Kangwon National University, Chuncheon, 200-701, Republic of Korea.

A series of N-protected beta-amino phosphonic acid esters have been prepared by phosphine-catalyzed allylic substitution of 2-(diethylphosphonyl)-substituted allylic acetates employing 4,5-dichlorophthalimide as nucleophilic partner. These organocatalytic allylic substitutions exhibit exceptionally high levels of regiospecificity by virtue of a tandem S(N)2'-S(N)2' mechanism.
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http://dx.doi.org/10.1021/jo061218sDOI Listing
September 2006

Alpha-hydroxy esters via enantioselective hydrogen-mediated C-C coupling: regiocontrolled reactions of silyl-substituted 1,3-diynes.

Org Lett 2006 Aug;8(17):3873-6

Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712, USA.

[reaction: see text] Catalytic hydrogenation of ethyl glyoxalate in the presence of 1,3-diynes 4a-9a using chirally modified rhodium catalysts enables formation of alpha-hydroxy esters 4c-9c in highly optically enriched form. Notably, for such trialkylsilyl-substituted 1,3-diynes, C-C coupling occurs exclusively at the carbon atom bearing silicon. Pi-back-bonding from low valent rhodium as described by the Dewar-Chatt-Duncanson model appears to direct the regiochemistry of C-C coupling, as corroborated by calculations of the diyne LUMO coefficients.
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http://dx.doi.org/10.1021/ol061485kDOI Listing
August 2006

Enantioselective reductive coupling of alkynes and alpha-keto aldehydes via rhodium-catalyzed hydrogenation: an approach to bryostatin substructures.

Org Lett 2006 Mar;8(5):891-4

University of Texas at Austin, Department of Chemistry and Biochemistry, Austin, Texas 78712, USA.

Hydrogen-mediated reductive coupling of glyoxal 2 and 1,3-enyne 3 provides alpha-hydroxy ketone 4 in 70% yield and 91% enantiomeric excess. Notably, the benzylic ether and diene side chain of 4 remain intact under the conditions of hydrogen-mediated coupling. In four steps, alpha-hydroxy ketone 4 is converted to pyrans 8 and 9, which embody key structural features of the bryostatin recognition domain.
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http://dx.doi.org/10.1021/ol052976sDOI Listing
March 2006