• Bulletin of the Korean Chemical Society
• /
• 제35권8호
• /
• pp.2342-2348
• /
• 2014

Poly(lactic-co-glycolic acid) (PLGA) were grafted to both ends of Pluronic$^{(R)}$ F68 ($(EO)_{75}(PO)_{30}(EO)_{75}$) triblock copolymer to produce poly{(lactic acid)$_m$-co-(glycolic acid)$_n$}-b-poly(ethylene oxide)$_{75}$-b-poly(propylene oxide)$_{30}$-b-poly(ethylene oxide)$_{75}$-b-poly{(lactic acid)$_m$-co-(glycolic acid)$_n$} (PLGA-F68-PLGA) pentablock copolymers. Molecular weights of PLGA blocks were controlled and five kinds of pentablock copolymers with different PLGA block lengths were synthesized using in-situ ring-opening polymerization of D,L-lactide and glycolide with tin(II) 2-ethylhexanoate ($Sn(Oct)_2$) catalyst. PLGA-F68-PLGA pentablock copolymers were characterized by $^1H$- and $^{13}C$-NMR, GPC, and TGA. The numbers (2m, 2n) of repeating units for lactic acid and glycolic acid inside PLGA segments were obtained as (48, 17), (90, 23), (125, 40), (180, 59), and (246, 64), with $^1H$-NMR measurement. From NMR data, the resultant molecular weights were determined in the range of 12,700-29,700, which were similar to those obtained from GPC. Polydispersity index was increased in the range of 1.32-1.91 as the content of PLGA blocks increased. TG and DTG thermograms showed discrete degradation traces for PLGA and F68 blocks, which indicate the weight fractions of PLGA blocks in pentablock copolymers can be calculated by TG profile and it is possible to remove PLGA block selectively. Hydrodynamic radius and radius of gyration of pentablock copolymer micelle were obtained in the range of 46-68 nm and 31-49 nm, respectively, in very dilute (i.e. 0.005 wt %) aqueous solution of THF:$H_2O$ = 10:90 by volume at $25^{\circ}C$.

• Bulletin of the Korean Chemical Society
• /
• 제13권2호
• /
• pp.158-162
• /
• 1992

Hydrocarbon solution of $(PPh_3)_2(CO)MOSO_2CF_3(M=Rh$, Ir)reacts rapidly with Pyrazine or 4,4'-bipyridyl to yield dinuclear metal complexes $[(PPh_3)_3(CO)M({\mu}-pyrazine)M(CO)(PPh_3)_2](SO_3CF_3)_2$ (I: M= RhH; III: M=Ir) or [$(PPh_3)_2$(CO)M(${\mu}$-44'-bipyridyl)M(CO)$(PPh_3)_2](SO_3CF_3)_2$, (II: M=Rh; IV: M=Ir), respectively. Compounds, I, II, III, and IV were characterized by $^1H-NMR$, $^{13}C-NMR$, $^{31}P-NMR$, and infrared spectrum. Ethanol solution of $(PPh_3)_2(CO)MOSO_2CF_3$ (M=Rh, Ir) also reacts with $(TBA)_2$M'$(CN)_4$ (M'=Pd, Pt) to yield trinuclear metal complexes [$(PPh_3)_2$(CO)dM-NCM'$(CN)_2$CN-M(CO)$(PPh_3)_2]$ (V : M=Rh, M'=Pd; VI : M=Rh, M'=Pt; VII: M=Ir, M'=Pd; VIII: M=Ir, M'=Pt). The trinuclear metal complexes V, VI, VII, and VIII are bridged by the cyanide groups. The infrared spectrum of V, VI, VII, and VIII supports the presence of the bridged cyanide and terminal cyanide group.

• Natural Product Sciences
• /
• 제21권2호
• /
• pp.76-81
• /
• 2015

Diospyros burmanica Kurz. is an evergreen deciduous tree distributed in Mandalay of Myanmar, which belongs to the family of Ebenaceae. In Myanmar, it has been used to treat diarrhea, diabetes, diabetes and also as lumbers. In this study, seven flavonoids (1 - 7), a phenolic compound (8), and five triterpenes (9 - 13) were isolated from the barks of D. burmanica and their chemical structures were elucidated. Isolates were identified to be (+)-catechin (1), (+)-catechin 3-O-$\alpha$-L-rhamnopyranoside (2), (+)-catechin 3-O-gallate (3), (-)-epicatechin (4), (-)-epicatechin 3-O-gallate (5), (+)-afzelechin 3-O-$\alpha$-L-rhamnopyranoside (6), (+)-2,3-trans-dihydrokaempferol 3-O-$\alpha$-L-rhamnopyranoside (7), methyl gallate (8), lupeol (9), methyl lup-20(29)-en-3-on-28-oate (10), $\beta$-amyrin (11), $\alpha$-amyrin (12), $3\beta$-hydroxy-D:B-friedo-olean-5-ene (13) through MS, ¹H NMR and ¹³C NMR spectroscopic evidences.

• 대한화학회지
• /
• 제40권1호
• /
• pp.87-95
• /
• 1996

이성분계 rendom copolyeseters인 Poly(butylene succinate-co-butylene terephthalate)(PBS/PBT)를 합성하고 $^1H$ NMR spectroecopy를 이용하여 전 조성범위에 걸쳐 sepuence distribution을 조사하였다. PBS/PBT 공중합물의 융점(Tm)은 공중합물내 dimethyl terephthalate(DMT)의 함량이 증가함에 따라 점차적으로 감소하는 현상을 나타냈고 ST3(DMT 65.8mol%)에서 최저융점(eutetic point) 거동을 보였다. 이러한 공중합물의 융점거동은 공중합물의 몰분율(Xa)보다는 triad fraction으로 계산된 sequence propagation probability(P)에 더욱 의존하는 경향을 보였다. 또한 succinate unit(또는 terephthalate unit)의 함량이 많은 공중합물들은 terephthalate unit(또는 succinate unit)를 완전히 배제시키면서 단지 PBS(또는PBT)만의 결정을 형성하였다.

• 한국수소및신에너지학회논문집
• /
• 제27권6호
• /
• pp.660-669
• /
• 2016

A fluorinated-sulfonated, hydrophobic-hydrophilic copolymer was planed subsequently synthesized using typical nucleophilic substitution polycondensation reaction. A novel AB and ABA (or BAB) block copolymers were synthesized using sBCPSBP (sulfonated 4,4'-bis[4-chlorophenyl)sulfonyl]-1,1'-biphenyl), DHN (1,5-dihydroxynaphthalene), DFBP (decafluorobiphenyl) and HFIP (4,4'-hexafluoroisopropylidenediphenol). All block copolymers were easily cast and made into clear films. The structure and synthesized copolymers and corresponding membranes were analyzed using GPC (gel permeation chromatography), $^1H$-NMR ($^1H$ nuclear magnetic resonance) and FT-IR (Fourier transform infrared). TGA (Thermogravimetric analysis) and DSC (differential scanning calorimetry) analysis showed that the prepared membranes were thermally stable, so that elevated temperature fuel cell operation would be possible. Hydrophobic/hydrophilic phase separation and clear ionic aggregate block morpology was confirmed in both triblock and diblock copolymer in AFM (atomic force microscopy), which may be highly related to their proton transport ability. A sulfonated BAB triblock copolymer membrane with an ion-exchange capacity (IEC) of 0.6 meq/g has a maximum ion conductivity of 40.3 mS/cm at $90^{\circ}C$ and 100% relative humidity.

• Membrane and Water Treatment
• /
• 제1권4호
• /
• pp.231-251
• /
• 2010

The sulfatation of chitosan, by reaction with chlorosulfonic acid under controlled conditions, allowed increasing the pH range of chitosan solubility. The biopolymer was characterized using FTIR and $^{13}C$-NMR spectroscopy, elemental analysis and titration analysis and it was tested for mercury recovery by polymer enhanced ultrafiltration (PEUF). In slightly alkaline conditions (i.e., pH 8) mercury recovery was possible and at saturation of the polymer the molar ratio $-NH_2$/Hg(II) tended to 2.6. Polymer recycling was possible changing the pH to 2 and the polymer was reused for 3 cycles maintaining high metal recovery. The presence of chloride ions influences metal speciation and affinity for the polymer and "playing" with metal speciation allowed using the PEUF process for mercury separation from cadmium; at pH 11 the formation of hydroxo-complexes of Hg(II) limits it retention. Cake formation reveals the predominant controlling step for permeation flux.

• 한국자기공명학회논문지
• /
• 제26권4호
• /
• pp.40-45
• /
• 2022

A small cage-like molecule (2) composed of three aminomethyl pyrroles and two hexa-substituted benzenes has been prepared by reduction of its iminopyrrole analogue (1) using NaBH₄. It was revealed by ¹H NMR spectroscopic analyses that cage molecule 2 strongly binds the fluoride anion in polar DMSO-d₆ relative to CDCl₃. Compared to that of compound 1, the lowered affinity of 2 for the fluoride anion is attributable to its increased electron density resulting from the production of thesecondary amine groups.

• 대한화학회지
• /
• 제39권1호
• /
• pp.66-70
• /
• 1995

토양에서 얻어진 흄산(HA)을 한외 여과법을 이용 분자량에 따라 4개의 소부분(F1 : 100,000 dalton 이상; F2 : 100,000 dalton 이하;10,000 dalton 이하; F4 : 2,000 dalton 이하)으로 분리한 뒤 적외선 분광법과 핵자기 공명 분광법을 통하여 각 소부분들의 분광학적 특성을 규명하고 상호간에 비교 분석하였다. 4개 소부분들의 $1^H$과 $13^C$ NMR 스펙트럼은 전체적인 특성에서 모두 흄산 모액 스펙트럼과 유사하게 나타났다. 이 결과는 분자량이 변하더라도 흄산의 전체적 특성이 그대로 유지됨을 제시한다. 차이점으로는 IR 스펙트럼 결과 분자량이 적어지면서 다당류 성분 함량이 다소 감소된 반면 카르복실기 성분 함량은 조금 증가된 것으로 나타났다.

• 한국미생물·생명공학회지
• /
• 제45권3호
• /
• pp.209-217
• /
• 2017

In the enduring investigation of the bioactive microbes, Pseudomonas aeruginosa strain (referred to as CGK-KS-1 (ICTB-315)), isolated from Chumathang hot spring, Ladakh, and India, was identified to possess a major bioactive fraction with antimicrobial and anti-biofilm properties. This bioactive metabolite was purified through bioactivity-guided fractionation. The chemical structure of this major compound was elucidated as phenazine-1-carboxamide (PCN) based on $^1H$ and $^{13}C$ NMR, FT-IR, EI-HR-MS and 2D NMR spectroscopic techniques. In the current study, PCN exhibited antimicrobial activity with MIC values ranging between $1.9-3.9{\mu}g/ml$ against various test human pathogens and Xanthomonas spp. PCN showed the anti-biofilm property with the $IC_{50}$ values ranging from 17.04 to $60.7{\mu}M$ against different test pathogens. The in silico docking studies showed PCN strongly interacted with various proteins of different Xanthomonas spp. with high binding energies. We report herein for the first time the anti-biofilm property and the docking studies of PCN. The extrolite from P. aeruginosa strain CGK-KS-1 showed promising bioactivities and may be considered as a potential candidate for application in various biocontrol strategies.

• 한국자원식물학회지
• /
• 제31권4호
• /
• pp.322-329
• /
• 2018

최근 식품의약품안전처에서 그동안 의약외품으로 분류되었던 '탈모 증상 완화' 관련 제품이 기능성 화장품의 범주에 포함됨에 따라서 관련 산업계에 큰 관심 중 하나라고 할 수 있다. 본 연구에서는 기존 의약품들의 한계점인 부작용의 위험률이 적으면서 탈모를 과학적으로 조절시켜줄 수 있는 객관적인 근거를 제시할 수 있는 천연물 유래 신소재를 발굴하고자, 오리나무 가지로부터 분리한 oregonin은 강력한 활성산소종 소거능을 가지며 탈모와 연관성이 높은 모유두 세포의 사멸을 명확하게 조절함을 확인하였다. 결론적으로 oregonin을 포함한 오리나무 추출물은 두피에서 발생한 활성산소를 강력하게 제거하는 효능을 기반으로 하여, 산화적 스트레스에 의한 모유두세포의 사멸 억제 및 조절을 통하여 탈모방지 효과를 기대할 수 있는 천연 탈모 방지 및 양모 신소재로서의 개발가능성이 있는 것으로 확인하였다.