• Bulletin of the Korean Chemical Society
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• 제24권9호
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• pp.1293-1302
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• 2003

Rate constants at various temperatures and activation parameters are reported for solvolyses of acyl chlorides (RCOCl), with R = Me, Et, i-Pr, t-Bu, cyclopentylmethyl, benzyl, thiophenylmethyl, 2-phenylethyl, diphenylmethyl, and phenylthiomethyl in 100% ethanol, 100% 2,2,2-trifluoroethanol (TFE), 80% v/v ethanol/ water and 97% w/w TFE/water. Additional rate constants for solvolyses with R = Me, t-Bu, and $PhCH_2$ are reported for TFE/water and TFE/ethanol mixtures, and for solvolyses with R = t-Bu, and PhCH2 are reported for 1,1,1,3,3,3-hexafluoropropan-2-ol/water mixtures, as well as selected kinetic solvent isotope effects (MeOH/MeOD and TFE). Taft plots show that electron withdrawing groups (EWG) decrease reactivity significantly in TFE, but increase reactivity slightly in ethanol. Correlation of solvent effects using the extended Grunwald-Winstein (GW) equation shows an increasing sensitivity to solvent nucleophilicity for EWG. The effect of solvent stoichiometry in assumed third order reactions is evaluated for TFE/ethanol mixtures, which do not fit well in GW plots for R = Me, and t-Bu, and it is proposed that one molecule of TFE may have a specific role as electrophile; in contrast, reactions of substrates containing an EWG can be explained by third order reactions in which one molecule of solvent (ethanol or TFE) acts as a nucleophile, and a molecule of ethanol acts as a general base catalyst. Isokinetic relationships are also investigated.

• 한국환경농학회지
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• 제14권1호
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• pp.45-54
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• 1995

esters of the acid analytes were synthesized using $H_2SO_4$ as the catalyst. Efficiency of derivatization and instrumental molecular-response were compared with herbicides methylated with $BF_3-methanol$(14% W/V), $H_2SO_4-methanol$(33% V/V), and diazomethane. The molecular integrity of TFE-2,4-D, TFE-dicamba, and TFE-mecoprop, in the mixture, was confirmed by the GC/MSD method. The TFE-Esterification efficiency was maximized by adjusting the volume of $H_2SO_4$ the reaction time, and temperature. Optimal efficiency for the herbicide mixture was obtained by adding 1 ml of $H_2SO_4$ and 1 ml of TFE to the dried sample and allowing the reaction to proceed at $22^{\circ}C$ for 8 hr or using 0.5 ml $H_2SO_4$ and 1 ml of TFE at $60^{\circ}C$. For 120 min increasing the temperature and decreasing the reaction time were required for maximum esterification efficiency. The sensitivity of the GC/ECD to the TFE esters was about $2{\sim}20$ times greater than that to the methyl ester derivatives. The herbicides were extracted and esterified to TFE derivatives simultaneously from soil leachates previously spiked with the analytes. Herbicide recovery, peak resolution, and detector sensitivity were excellent without using column cleanup procedures.

• Bulletin of the Korean Chemical Society
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• 제25권6호
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• pp.838-842
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• 2004

Amyloid peptide (A${\beta}$) is the major component of senile plaques found in the brain of patient of Alzheimer's disease. ${\beta}$-amyloid peptide (25-35) (A${\beta}$25-35) is biologically active fragment of A${\beta}$. The three-dimensional structure of A${\beta}$25-35 in aqueous solution with 50% (vol/vol) TFE determined by NMR spectroscopy previously adopts an ${\alpha}$-helical conformation from $Ala^{30}$ to $Met^{35}$. It has been proposed that A${\beta}$(25-35) exhibits pH- and concentration-dependent ${\alpha}-helix{\leftrightarrow}{\beta}$sheet transition. This conformational transition with concomitant peptide aggregation is a possible mechanism of plaque formation. Here, in order to gain more insight into the mechanism of ${\alpha}$-helix formation of A${\beta}$25-35 peptide by TFE, which particularly stabilizes ${\alpha}$-helical conformation, we studied the secondary-structural elements of A${\beta}$25-35 peptide by molecular dynamics simulations. Secondary structural elements determined from NMR spectroscopy in aqueous TFE solution are preserved during the MD simulation. TFE/water mixed solvent has reduced capacity for forming hydrogen bond to the peptide compared to pure water solvent. TFE allows A${\beta}$25-35 to form bifurcated hydrogen bonds to TFE as well as to residues in peptide itself. MD simulation in this study supports the notion that TFE can act as an ${\alpha}$-helical structure forming solvent.

• 대한영상의학회지
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• 제85권2호
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• pp.437-444
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• 2024

고유신장과 이식신장 모두에 신세포암종이 발생하는 경우는 매우 드물며, 소수의 증례만이 영문 문헌에서 보고되었다. Xp11.2전위/전사인자E3 (이하 TFE3)-재배열 신세포암종은 성인인구에서 드문 아형이다. 신장이식을 받은 어린이에서 TFE3-재배열 신세포암종이 소수의 증례로 보고되었으나, 어른에서 신장이식 후 TFE3-재배열 신세포암종이 보고된 증례는 없다. 저자들은 이식신장에 유두모양 신세포암종이, 고유신장에 TFE3-재배열 신세포암종이 있던 드문 증례를 영상 소견과 함께 보고하고자 한다. 고유신장에 생긴 TFE3-재배열 신세포암종은 5년에 걸쳐 천천히 자랐다. CT에서 약한 조영증강을 보이는 소엽 모양 종괴였으며, MRI에서는 T1 강조영상에서 높은 신호 강도를, T2 강조영상에서 낮은 신호 강도를 보였다.

• 대한한방부인과학회지
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• 제21권3호
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• pp.18-33
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• 2008

Purpose: The research is to investigate the effect of TFE on apoptosis of human-derived breast cancer cells, to find out the relationship with apoptosis. Methods: Human-derived breast adenocarcinoma cell line, MCF-7 cells were treated by TFE with various concentration. The inducement effect of TFE on cell apoptosis was observed with MTT assay and the relationship between the treatment and apoptosis was investigated with FACS analysis, TUNEL assay and DNA laddering assay and the change in the protein levels of PARP and caspase-3 activities were also observed. The release of cytochrome-c was observed to find out the pathway of apoptosis induced by TFE. Results: The cell apoptosis was significantly induced in MCF-7 cells treated with TFE in concentration-dependent and time-dependent manner. It was verified by FACS analysis, TUNEL assay, DNA laddering assay that cell-death was caused not by necrosis but by apoptosis. The activity of PARP and caspase were increased concentration-dependently. The release of cytocrome-c was decreased in proportion to the concentration of the fruit extract. It therefore demonstrated that mitochondria were involved in apoptosis induced by TFE. The appearance of Bcl-2 protein was decreased concentration-dependently. Conclusion: The treatment by TFE induced apoptosis of human breast adenocarcinoma cell line, MCF-7. It seems likely that cell-death was caused by apoptosis and mitochondria were involved in it. The mechanism of protein change causing apoptosis seems related to the inhibition of Bcl-2 protein, the promotion of inversion from cytochrome-c into cytosol, the activation of caspase and the promotion of PARP cleavage.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.26-26
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• 2003

The backbone dynamics of ketosteroid isomerase, a homodimeric enzyme with 125 amino acid residues per subunit, has been studied in the presence/absence of a steroid ligand and 5％ trifluoroethanol (TFE) by $^{15}$ M relaxation measurements. The relaxation data were analyzed using the model-free formalism to extract the model-free parameters (S$^2$, $\tau$$_{e}$, and R$_{ex}$ ). The results show that a large number of the residues, particularly those involved in the dimer interaction, exhibit reduced order parameters (S$^2$) in the steroid-bound enzyme, indicating the increased high-frequency (pico- to nanosecond) motions in the interface region upon ligand binding. The results also show that that the presence of 5 ％ TFE in free enzyme causes little change or slight increase in the order parameters for a number of residues in the dimer interface region. However, the majority of the residues in free enzyme exhibit reduced order parameters in the presence of 5 ％ TFE, indicating that the increase in entropy is partially responsible for the increased stability of KSI by 5％ TFE.E.E.

• Investigative Magnetic Resonance Imaging
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• 제17권1호
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• pp.41-46
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• 2013

신세포암의 여러 종류 중 Xp11.2 염색체 재배열/TFE3 유전자 융합 연관 신세포암은 드물며 소아나 젊은 성인에서 더 흔한 것으로 알려져 있다. 이 증례보고는 병리학적으로 확인된 4세 남자 환자의 Xp11.2 염색체 재배열/TFE3 유전자 융합 연관 신세포암에 대한 것이다. 본 증례에서 종양은 컴퓨터 단층 촬영에서 우측 신장에 2.5 cm 크기의 경계가 불명확한 종괴로 보였으며, 초음파상 고에코 병변으로 보였다. 자기공명영상에서는 종괴 캡슐의 조영증강과 함께 종괴의 확산 제한이 보였다. 저자들은 이 드문 신세포암의 영상 소견에 대해 증례를 보고하고 문헌을 고찰하는 바이다.

• 한국환경농학회지
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• 제13권2호
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• pp.199-208
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• 1994

토양 침투수중에 잔류하는 제초제 MCPP를 추출, 유도체를 합성하여 GC-MS로 확인하고 capillary GC-ECD로 잔류분석하였다. Diazomethane과 $BF_3$/MeOH 등을 이용하여 합성한 MCPP의 methyl 유도체, 황산을 촉매로 이용하여 합성한 MCPP의 2,2,2-trifluoroethyl(TFE) 및 2,2,2-trichloroethyl(TCE) 유도체, 그리고 MCPP의 pentafluorobenzyl(PFB) 유도체간의 잔류분석법을 비교한 결과 이 연구에서 개발된 MCPP-TFE 유도체화가 간편하고 신속, 안전한 유도체화 기술로서 GC-ECD에서 비교적 감도가 우수한 편이었다. MCPP의 methyl 유도체는 GC-ECD에서 그 감도가 너무 낮아 시료가 소량인 경우 ppb 수준의 잔류분석이 불가능하였고 MCPP-TCE 및 MCPP-PFB 유도체는 그 감도는 우수하였으나 크로마토그람상의 방해물질이 많아 액액분리에 의한 정제만으로는 잔류분석이 곤란하였다. MCPP-TFE 유도체화에 의하면 토양침투수 100ml중 $0.1{\mu}g$ 미만의 농도를 가진 MCPP의 잔류분석이 액액분리에 의한 정제만으로 가능하였다.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.615-621
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• 2013

Solvolyses of isobutyl chloroformate (4) in 43 binary solvent mixtures including highly aqueous media, water, $D_2O$, $CH_3OD$, 2,2,2-trifluoroethanol (TFE) as well as aqueous 1,1,1,3,3,3-hexafluoro-isopropanol (HFIP) solvents were performed at $45^{\circ}C$, in order to further investigate the recent results of D'Souza, M. $J^1$. et al.; solvolyses of 4 are found to be consistent with the proposed mechanism ($Ad_E$). The variety of solvent systems was extended to comprise highly ionizing power solvent media ($Y_{Cl}$ > 2.7 excepted for aqueous fluorinated solvents and pure TFE solvent) to investigate whether a mechanistic change occurs as solvent compositions are varied. However, in case of 18-solvent ranges having aqueous fluorinated solvent systems (TFE-$H_2O$ and HFIP-$H_2O$) and/or having $Y_{Cl}$ > 2.7 solvent systems, the solvent effect on reactivity for those of 4 are evaluated by the multiple regression analysis as competition with $S_N2$ - type mechanism. And in pure TFE and 97 w/w % HFIP solvents with high $Y_{Cl}$ and weak $N_T$, these solvolyses are understood as reactions which proceed through an ionization ($S_N1$) pathway.

• Korean Journal of Radiology
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• 제22권4호
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• pp.513-524
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• 2021

Objective: To assess the noncontrast two-dimensional single-shot balanced turbo-field-echo magnetic resonance angiography (b-TFE MRA) features of the abdominal aortic aneurysm (AAA) status following endovascular aneurysm repair (EVAR) and evaluate to detect endoleaks (ELs). Materials and Methods: We examined four aortic stent-grafts in a phantom study to assess the degree of metallic artifacts. We enrolled 46 EVAR-treated patients with AAA and/or common iliac artery aneurysm who underwent both computed tomography angiography (CTA) and b-TFE MRA after EVAR. Vascular measurements on CTA and b-TFE MRA were compared, and signal intensity ratios (SIRs) of the aneurysmal sac were correlated with the size changes in the AAA after EVAR (AAA prognoses). Furthermore, we examined six feasible b-TFE MRA features for the assessment of ELs. Results: There were robust intermodality (r = 0.92-0.99) correlations and interobserver (intraclass correlation coefficient = 0.97-0.99) agreement. No significant differences were noted between SIRs and aneurysm prognoses. Moreover, "mottled high-intensity" and "creeping high-intensity with the low-band rim" were recognized as significant imaging findings suspicious for the presence of ELs (p < 0.001), whereas "no signal black spot" and "layered high-intensity area" were determined as significant for the absence of ELs (p < 0.03). Based on the two positive features, sensitivity, specificity, and accuracy for the detection of ELs were 77.3%, 91.7%, and 84.8%, respectively. Furthermore, the k values (0.40-0.88) displayed moderate-to-almost perfect agreement. Conclusion: Noncontrast MRA could be a promising imaging modality for ascertaining patient follow-up after EVAR.