• Bulletin of the Korean Chemical Society
• /
• 제28권7호
• /
• pp.1127-1134
• /
• 2007

It was demonstrated that Y[N(TMS)2]3, the neutral yttrium-diamine complex 13 and yttrium-NPS complexes 15 are efficient precatalysts for intramolecular hydroamination of aminoalkynes involving primary amines. Complex 13 and 15 were quantitatively prepared in situ by direct metalation of the ligands 4 and 9 with 1 equiv of Y[N(TMS)2]3 in benzene-d6 at 120 oC for 5 days and 10 days, respectively, via elimination of (TMS)2NH. 5-Exo- and 6-exo-dig intramolecular hydroamination of aminoalkynes using catalyst 12 and 13 proceeded smoothly to give nitrogen-contained cyclic products in good to excellent yields in all cases. In the case of 7- exo-dig intramolecular hydroamination, the desired product was produced in 41% and 48% yields despite the gem-dimethyl effect. However, treatment of catalyst 15 with aminoalkynes (19 and 22) having a methyl substituent at the carbon adjacent to triple bond and 6-exo-dig intramolecular hydroamination of 21 failed to give the desired products. Zirconium-catalyzed intramolecular hydroamination of aminoallenes (25, 27, and 31) with 5 mol% 16 afforded 2-(trans-1-propenyl)pyrrolidine, 2-isopropylenepyrrolidine, and 2-(trans-1- propenyl)piperidine in 96%, 95%, and 93% yield, respectively. However, subjecting 25 to 5 mol% 15 was unsuccessful to produce the desired product.

• Fibers and Polymers
• /
• 제2권2호
• /
• pp.92-97
• /
• 2001

New film forming aromatic poly(amide-imide)s containing isoindoloquinazolinedione (IQ) unit in the backbone chain (polymer XIV) have been successfully synthesized by preparing prepolymers of poly(amic acid-carbonamide). followed by subsequent thermal cyclization of the prepolymers. 4,4-Diamino-3-carbamoylbenzanilide (DACB) V has been synthesized by reduction of 3-carbamoyl-4-amino-4-nitrobenzanilide IV. The prepolymers of poly(amic-acid-carbonamide) (polymers VII and VIII) which exhibit viscosities ranging from 1.4 to 1.7 dl/g have been prepared by a condensation polymerization of monomers such as BPDA, ODA, and DACB. Polymer XIV has been obtained by thermal cyclization of the polymers VII and VIII. During the thermal cyclization reaction, imide ring structure was first introduced and then transformed to the structure of IQ unit. The thermal degradation rate of the resultant polymers were influenced by the cleavage of amide bond but the final char yield was comparable to that of poly(BPDA-ODA).

• 대한화학회지
• /
• 제31권5호
• /
• pp.457-463
• /
• 1987

2-브로모프로피오닐화된 수지를 이용해 insulin A (1-21) 사슬을 합성하였다. 시스테인의 결사슬은 각각 acetamidomethyl, benzyl, 그리고 benzhydryl기로 보호하였으며 그루타민과 아스파라긴은 p-nitrophenyl기로 활성화하여 합성에 이용하였다. 매 짝지음단계마다 DCC/HOBT coupling agent로 각 아미노산을 축합하였으며 반응의 완결여부는 닌히드린시험으로 측정하였다. 생성물은 NH$_3$/MeOH-Dioxane(v/v 1:1)로 수지로부터 분리하여 DEAE Sephadex A-25와 Sephadex LH-20으로 정제하였으며 최종생산물은 HPLC, electrophoresis로 확인한 결과 순수한 것(>99.9%)으로 나타났으며 총수득율은 6%이었다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제8권4호
• /
• pp.265-273
• /
• 2004

압축강도 실험결과, 고막패각 혼입량 15%와 20% 시험체가 무혼입 시험체보다 증가하는 것으로 나타났다. 시험체의 연성능력은 일반 잔골재를 사용한 시험체가 가장 높았으며, 고막패각의 혼입량이 많을수록 연성능력은 낮게 나타났고, 고막패각 혼입량이 많을수록 낮은 하중에서 초기균열이 발생하여 하중의 증가로 인하여 부재의 처짐 속도가 빨라지는 것으로 나타났다. 이는 고막패각의 혼입량에 따라 부착력이 부족하여, 이후 항복내력이 상대적으로 증가하지 못한 것으로 판단된다

• Journal of Microbiology and Biotechnology
• /
• 제1권2호
• /
• pp.102-110
• /
• 1991

Alkalophilic Bacillus sp. YJ-451, which was isolated from soil at several area in Korea, produced a novel type of bacteriolytic enzyme (cell wall peptidoglycan hydrolase) extracellulary. The cell wall hydrolytic activity was identified as a clear zone on sodium dodecyl sulfate polyacrylamide gel electrophoresis containing 0.2% (w/v) cell wall of Bacillus sp. as substrate. This enzyme was successively purified 66 fold with 3.2% yield in culture broth by ammonium sulfate precipitation, CM-cellulose column chromatography, and gel filtration, followed by hydroxylapatite column chromatography. The molecular weight of the purified enzyme was estimated to be 27,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration column chromatography. The optimum pH and temperature for the activity of the enzyme were pH 10.0 and $50^{\circ}C$, respectively. The enzyme was stable between pH 5.0 and 10.0 and up to $40^{\circ}C$. Among the microorganisms used in this experiment the enzyme was active against most of gram negative strains and the genus Bacillus such as B. megaterium, B. licheniformis, B. circulans, B. pumilus, B. macerans, B. polymyxa. The release of dinitrophenylglutamic acid but not reducing group from cell wall peptidoglycan digested by the enzyme suggested that the enzyme is a kind of peptidase which hydrolyzes the peptide bond at the amino group of D-glutamic acid in the peptidoglycan.

• 한국응용약물학회:학술대회논문집
• /
• 한국응용약물학회 1998년도 Proceedings of UNESCO-internetwork Cooperative Regional Seminar and Workshop on Bioassay Guided Isolation of Bioactive Substances from Natural Products and Microbial Products
• /
• pp.150-151
• /
• 1998

Drug delivery to the brain is facilitated by the synthesis of chimeric peptides, where in neuropharmaceuticals are linked to a vector such as an antibody to the transferrin receptor that mediates transcytosis through the blood-brain barrier (BBB). When disulfide linkers are used in the chimeric peptide, it is crucial that the S-S bridge is stable during transit and that cleavage does not occur prematurely within endothelial cells, as the peptide drug moiety would then be sequestered by the BBB instead of passing through it. The present study addressed that problem. As a model drug a metabolically stable opioid peptide, [$^3$H]DALDA (Tyr-dArg-Phe-Lys-NH$_2$), was used. It was monobiotinylated with NHS-SS-biotin to yield bio-[$^3$H]DALDA. The biotinylated peptide was bound to the vector OX26-SA which is a covalent conjugate of OX26 and streptavidin (molar ratio = 1: 1). In vitro treatment of the chimeric peptide, bio-[$^3$H]DALDA/OX26-SA, with a reducing agent, dithiothreitol, released the labeled peptide from the vector by conversion of bio-[$^3$H]DALDA to the desbiotinylated derivative, desbio-[$^3$H]DALDA.

• KSBB Journal
• /
• 제24권3호
• /
• pp.239-245
• /
• 2009

광학활성 styrene oxide는 친전자성반응, 친핵성반응, 산 염기반응, 산화 환원반응 등 다양한 반응을 유도할 수 있어 광학활성 중간체로 널리 사용될 수 있다. Styrene monooxygenase (SMO)를 생촉매로 이용하여 styrene의 side-chain 이중결합에 입체선택적으로 에폭사이드 링을 도입시켜 광학활성 styrene oxide 유도체를 제조할 수 있다. 다양한 기질 특이성을 가진 신규 SMO 생촉매 개발, 이상계 반응 시스템, in situ 분리 공정, multimeric oxygenase 효소발현 및 안정화 기술 개발, NADH 등 cofactor regeneration 등에 대한 연구개발이 활발히 진행되고 있어, 미생물유래의 SMO를 생촉매로 활용하는 광학활성 styrene oxide 유도체 제조 기술의 상업화가 기대된다.

• Steel and Composite Structures
• /
• 제20권6호
• /
• pp.1305-1322
• /
• 2016

This paper presents the results of experimental and numerical model analyses on partially encased composite columns under concentric loads. The main objective of this study is to evaluate the influence of replacing the conventional longitudinal and transverse steel bars by welded wire mesh on the structural behavior of these members under concentric loads. To achieve these goals experimental tests on four specimens of partially encased composite columns submitted to axial loading were performed and the results were promising in terms of replacing the traditional reinforcement by steel meshes. In addition, a numerical FE model was developed using the software DIANA$^{(R)}$ with FX+. The experimental results were used to validate the numerical model. Satisfactory agreement between experimental and numerical results was observed in both capacity and deformability of the composite columns. Despite of the simplifying assumptions of perfect bond between steel and concrete, the numerical model adequately represented the columns behavior. A finite element parametric study was performed and parameters including thickness of the steel profile and the concrete and steel strengths were evaluated. The parametrical study results found no significant changes in the partially encased columns behavior due to variations of the steel profile thickness or yield strength. However, significant changes in the post peak behavior were observed when using high strength concrete and these results suggest a change in the failure mode.

• Steel and Composite Structures
• /
• 제11권6호
• /
• pp.469-488
• /
• 2011

This paper consists of two parts; the first part describes the laboratory work concerning the behavior of lightweight aggregate concrete filled steel tubes (LACFT). Based on eccentricity tests, fifty-four specimens with different slenderness ratios (L/D= 3, 7, and 14) were tested. The main parameters varied in the test are: load eccentricity; steel ratio; and slenderness ratio. The standard load-strain curves of LACFT columns under eccentric loading were summarized and significant parameters affecting LACFT column's bearing capacity, failure mechanism and failure mode such as confinement effect and bond strength were all studied and analyzed through the comparison with predicted strength of concrete filled steel tube columns (CFT) using the existing codes such as AISC-LRFD (1999), CHN DBJ 13-51-2003 (2003) and CHN CECS 28:90 (1990). The second part of this paper presents the results of parametric study and introduces a practical and accurate method for determination of the maximum compressive strength of confined concrete core ($f_{max}$), In addition to, the study of the effect of aspect-ratio and length-width ratio on the yield stress of steel tubes ( $f_{sy}$) under biaxial state of stress in CFT columns and the effect of these two factors on the ultimate load carrying capacity of axially loaded CFT/LACFT columns.

• Bulletin of the Korean Chemical Society
• /
• 제28권11호
• /
• pp.2003-2008
• /
• 2007

The aminolysis of diphenyl thiophosphinic chloride (2) with substituted anilines in acetonitrile at 55.0 oC is investigated kinetically. Kinetic results yield large Hammett ρX (ρnuc = ?3.97) and Bronsted βX (βnuc = 1.40) values. A concerted mechanism involving a partial frontside nucleophilic attack through a hydrogen-bonded, four-center type transition state is proposed on the basis of the primary normal kinetic isotope effects (kH/kD = 1.0-1.1) with deuterated aniline (XC6H4ND2) nucleophiles. The natural bond order charges on P and the degrees of distortion of 42 compounds: chlorophosphates [(R1O)(R2O)P(=O)Cl], chlorothiophosphates [(R1O)(R2O)P(=S)Cl], phosphonochloridates [(R1O)R2P(=O)Cl], phosphonochlorothioates [(R1O)R2P(=S)Cl], chlorophosphinates [R1R2P(=O)Cl], and chlorothiophosphinates [R1R2P(=S)Cl] are calculated at the B3LYP/ 6-311+G(d,p) level in the gas phase.