PAN Unit의 단일중합체와 공중합체에서의 배향에 관한 연구

박해랑,류주환 충남대학교 산업기술연구소 2003 산업기술연구논문집 Vol.18 No.1

Polyacrylonitrile(PAN) is a well-known crystalline polymer. Even when PAN is in its atactic configuration, as is usual, the crystallinity still strongly persists. This is due to the strong interaction between the nitrile groups. Hence much interest has been focused on the elucidation of the conformation of PAN. However, a full agreement on the crystalline morphology and the conformational state of individual polymer chains is yet to be achieved. In this study, we used as samples a PAN homopolymer and an AN-methyl acrylate(MA) copolymer. In the latter, MA is considered as a way of introducing a slight structural perturbation to the AN sequence in the homopolymer. Then the infrared dichroism technique was used to follow the behavior of orientation as a function of the extension. In carrying out these experiments, detailed considerations on the conformational structure of the PAN chains were given on the molecular basis. As a result, we found that the orientation behavior of the unperturbed AN sequences was more sensitive to the extension and its linearity of the chains was higher than the perturbed counterpart, in good agreement with the conjecture on the molecular level.

ST6Gal-I Predicts Postoperative Clinical Outcome for Patients with Localized Clear-cell Renal Cell Carcinoma

Liu, Hai-Ou,Wu, Qian,Liu, Wei-Si,Liu, Yi-Dong,Fu, Qiang,Zhang, Wei-Juan,Xu, Le,Xu, Jie-Jie Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.23

Hyperactivated ${\alpha}2$-6-sialylation on N-glycans due to overexpression of the Golgi enzyme ${\beta}$-galactoside: ${\alpha}2$-6-sialyltransferase (ST6Gal-I) often correlates with cancer progression, metastasis, and poor prognosis. This study was aimed to determine the association between ST6Gal-I expression and the risk of recurrence and survival of patients with localized clear-cell renal cell carcinoma (ccRCC) following surgery. We retrospectively enrolled 391 patients (265 in training cohort and 126 in validation cohort) with localized ccRCC underwent nephrectomy at a single center. Tissue microarrays were constructed for immunostaining of ST6Gal-I. Prognostic value and clinical outcomes were evaluated. High ST6Gal-I expression was associated with Fuhrman grade (p<0.001 and p=0.016, respectively) and the University of California Los-Angeles Integrated Staging System (UISS) score (p=0.004 and p=0.017, respectively) in both cohorts. Patients with high ST6Gal-I expression had significantly worse overall survival (OS) (p<0.001 and p<0.001, respectively) and recurrence free survival (RFS) (p<0.001 and p=0.002, respectively) than those with low expression in both cohorts. On multivariate analysis, ST6Gal-I expression remained associated with OS and RFS even after adjusting for the UISS score. Stratified analysis suggested that the association is more pronounced among patients with low and intermediate-risk disease defined by the UISS score. High ST6Gal-I expression is a potential independent adverse predictor of survival and recurrence in ccRCC patients, and the prognostic value is most prominent in those with low and intermediate-risk disease defined by the UISS score.

Characterization of LasR Protein Involved in Bacterial Quorum Sensing Mechanism of Pseudomonas aeruginosa

Hai Bo Liu,Kyong Pyo Koh,이준희,김정선,박성훈 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.2

The quorum sensing (QS) mechanism of Pseudomonas aeruginosa has been studied extensively due to its involvement in cystic fibrosis, a deadly disease that is responsible for the death of more than a thousand people annually. In order to develop biochemical assay method for screening QS inhibitor, we have studied the production and characterization of recombinant LasR protein, which is a transcriptional activator for the QS mechanism in P.aeruginosa. In recombinant Escherichia coli BL21, LasR was produced as functionally-active proteins when the cells were cultivated in the presence of a proper signaling molecule (acyl homoserine lactone, AHL) only. Some soluble LasR proteins could be obtained from the cells which were grown in AHL-deficient medium, but they did not show binding affinity to the promoter sequence OP1 (lasB elastase promoter). Furthermore, the active LasR, presumably produced as LasR-AHL complex, was not dissociated into its components (LasR and AHLs)in vitro. The current results indicate that the production of pure and active LasR devoid of AHL is very difficult. It can be concluded that the development of biochemical assay method for screening AHL competitive inhibitors which requires pure and active LasR proteins might not be possible unless the structure of LasR and/or its folding processes is modified

Identification and expression profiles of chitin deacetylase genes in the rice leaf folder, Cnaphalocrocis medinalis

Hai-Zhong Yu,Ming-Hui Liu,Xue-Yang Wang,Xin Yang,Wan-Ling Wang,Lei Geng,Dong Yu,Xue-Lan Liu,Gui-Ying Liu,Jia-Ping Xu 한국응용곤충학회 2016 Journal of Asia-Pacific Entomology Vol.19 No.3

Chitin deacetylase (CDA) is an insect chitin degradation enzyme that catalyzes the deacetylation of chitin to form chitosan. In this study, combination of rapid-amplification of cDNA ends (RACE) technology with Cnaphalocrocis medinalis transcriptome database analysis revealed the presence of at least five C. medinalis CDAs (CmCDAs), which were CmCDA1, CmCDA2, CmCDA4, CmCDA5, and CmCDA6. The cDNA sequences of CmCDA1, CmCDA2, and CmCDA4 hadwhole open reading frame (ORF) for further analysis. Phylogenetic analysis indicated that insect CDAs could be categorized into five groups. CmCDAs' structural domain analysis revealed that all three CDAs contained the chitin deacetylase-like catalytic domain. CmCDA1 and CmCDA2 belong to Group I because they both contain the chitin-binding peritrophin-A domain (ChBD), low-density lipoprotein receptor class A domain (LDLa), and chitin deacetylase-like catalytic domain. CmCDA4 only contains ChBD and chitin deacetylase-like catalytic domain thus belongs to Group III. Tissue and developmental stage expression analysis showed that the expression levels of CmCDA1, CmCDA2, and CmCDA4 are significantly higher in the head than other tissues and also significantly higher in adults than in larvae. CmCDA5 had significantly higher expression in the integument than other tissues, suggesting potential roles in the process of degradation of chitin. In contrast, CmCDA5 showed relatively high expression in larvae. In conclusion, this study analyzed the cDNA sequences of three CDA genes and determined their expression and molecular characteristics, which provided a new sequence resource and improved the development of bio-pesticides and the biological pest control and contributed to management of this important agricultural pest.

Characterization of LasR Protein Involved in Bacterial Quorum Sensing Mechanism of Pseudomonas aeruginosa

Hai Bo Liu,Kyong Pyo Koh,Joon Hee Lee,Jung Sun Kim,Sunghoon Park 한국생물공학회 2008 한국생물공학회 학술대회 Vol.2008 No.10

Production and Characterization of LasR Protein Involved in Quorum Sensing Mechanism of Pseudomonas aeruginosa

Hai Bo Liu,Kyong Pyo Koh,Joon Hee Lee 한국생물공학회 2008 한국생물공학회 학술대회 Vol.2008 No.4

Experimental study of nanofluid droplet spreading on a solid substrate

( Hai Long Liu ),( Rui Wang ),( Yuan-ping Huo ),( Jun-feng Wang ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

The nanofluid is a class of fluids with high thermal conductivity and non-Newtonian flow behaviors. The spreading characteristics of a nanofluid droplet impinging on the solid surface are the key factors to efficient heat and mass transfer in related processes by the deposition of droplets. In this study, three stable nanofluids (with carbon nanotubes, graphene, nano-graphite powder) were prepared by two-step method. The shear-dependent viscosity of these nanofluids have been studied experimentally. Furthermore, we investigated the evolution morphology of the droplet during the spreading process under various Weber numbers (We) by means of high-speed camera visualization technique. Based on the image processing technique (LB-ADSA), the dynamic contact angle (DCA), rebounding height and spreading factor of the droplet have been obtained along with spreading time. The experimental results show that the degrees of shear thinning in nanofluids are dissimilar and thus influence the spreading behaviors of nanofluid droplet. Specifically, the shear thinning behaviors suppress the spreading and rebounding stage of droplets. This suppression in nanofluid with large infinite shear viscosity are more prominent.

The Effects of Betonicine, Floridoside, and Isethionic Acid from the Red Alga Ahnfeltiopsis flabelliformis on Quorum-Sensing Activity

Hai Bo Liu,고경표,김정선,서영완,박성훈 한국생물공학회 2008 Biotechnology and Bioprocess Engineering Vol.13 No.4

A mixture of three compounds (betonicine, floridoside, and isethionic acid) purified from the red alga Ahnfeltiopsis flabelliformis, was reported to have an inhibition activity on bacterial quorum sensing mechanism mediated by N-octanoyl-DL-homoserine lactone (OHL) and the TraR transcriptional activator protein. We subsequently conducted a more detailed investigation of the three compounds using chemically synthesized (betonicine and floridoside) or commercially available (isethionic acid) compounds, individually or in various combinations. When tested alone, none of the three compounds inhibited OHL, but a mixture of floridoside and isethionic acid exhibited a dose-dependent inhibitory effect on the function of OHL. In contrast, betonicine or its isomer exhibited a dose-dependent stimulatory effect, similar to OHL, at concentrations between 10-³and 10-6M. These three compounds will be useful for elucidating the interaction between OHL and TraR, and for developing novel bacterial quorum-sensing inhibitors.

Spectroscopic Properties of Quercetin Derivatives, �Quercetin-3-<i>O</i>-rhamnoside and Quercetin-3-<i>O</i>-rutinoside, in �Hydro-organic Mixed Solvents

Liu, Hai-Bo,Yu, Daun,Shin, Sung Chul,Park, Hyoung-Ryun,Park, Jong Keun,Bark, Ki-Min Wiley (Blackwell Publishing) 2009 Photochemistry and photobiology Vol.85 No.4

<P>The characteristic fluorescence properties of quercetin-3-O-rhamnoside (QCRM) and quercetin-3-O-rutinoside (QCRT) were studied in CH3OH-H2O and CH3CN-H2O mixed solvents. Although QCRM and QCRT are known as nonfluorescent molecules, significant fluorescence emissions were discovered at 360 nm in CH3OH and CH3CN when they were promoted to the second excited state. The emission band is broad and structureless and the intensity decreases quickly as the H2O composition in the solvent increases. When the amount of H2O exceeds 60% in both mixed solvents, this emission disappears due to the formation of the distorted excited state. This state will be formed due to the strong intermolecular hydrogen bonding between the polar groups of solute and H2O. As the composition of CH3OH or CH3CN in solvent becomes large, the number of molecules having several intramolecular hydrogen bonding increases. Some of these molecules will be changed to a fluorescent species during the decay process, after excitation. The theoretical calculation further supports these results. The change of the lifetimes, quantum yields, and radiative and nonradiative rate constants of molecules was also examined as a function of solvatochromic parameters for CH3OH-H2O and CH3CN-H2O.</P>

Numerical simulation of a shear-thinning fluid through packed spheres

Hai Long Liu,Jong Sin Moon,황욱렬 한국유변학회 2012 Korea-Australia rheology journal Vol.24 No.4

Flow behaviors of a non-Newtonian fluid in spherical microstructures have been studied by a direct numerical simulation. A shear-thinning (power-law) fluid through both regular and randomly packed spheres has been numerically investigated in a representative unit cell with the tri-periodic boundary condition, employing a rigorous three-dimensional finite-element scheme combined with fictitious-domain mortar-element methods. The present scheme has been validated for the classical spherical packing problems with literatures. The flow mobility of regular packing structures, including simple cubic (SC), body-centered cubic (BCC), face-centered cubic (FCC), as well as randomly packed spheres, has been investigated quantitatively by considering the amount of shear-thinning, the pressure gradient and the porosity as parameters. Furthermore, the mechanism leading to the main flow path in a highly shear-thinning fluid through randomly packed spheres has been discussed.