Reaction of Ce(O-t-Bu)2(NO3)2 and sodium guanidinate GuaNa (Gua-=TMS2NC(NC6H11)2-) in THF affords the first guanidinate Ce(IV) complex of Ce2(O-t-Bu)7(Guaˊ) (1, Gua-=(C6H11NH)C(NC6H 11)(NH)-). I...Reaction of Ce(O-t-Bu)2(NO3)2 and sodium guanidinate GuaNa (Gua-=TMS2NC(NC6H11)2-) in THF affords the first guanidinate Ce(IV) complex of Ce2(O-t-Bu)7(Guaˊ) (1, Gua-=(C6H11NH)C(NC6H 11)(NH)-). It crystallizes in monoclinic, space group P21/n with a=15.2937(14), b=17.8409(16), c=19.0454(16), β=97.713(2)°, V=5149.6(8)3 , Z=4, Mr=1014.38, Dc=1.308 g/cm3 , μ=1.787 mm-1 , F(000)=2104, S=1.015, R=0.0451 and wR=0.0901 (I 〉 2σ(I)). In the reaction the cleavage of TMS-N bonds happened unexpectedly.展开更多
The synthesis,characterization,and theoretical studies of titanium-μ-N_(2) complexes with di-anionic guanidinate ligands were reported as the first example of its kind.Thus,with(Me_(3)Si)_(2)N-guanidinate ligands,the...The synthesis,characterization,and theoretical studies of titanium-μ-N_(2) complexes with di-anionic guanidinate ligands were reported as the first example of its kind.Thus,with(Me_(3)Si)_(2)N-guanidinate ligands,the mono-anionic guanidinate-supported titanium-μ-N2complex 1 was obtained.Then,reduction of 1 with potassium afforded the di-anionic guanidinate-supported titanium-μ-N_(2) complex 2 via cleavage of one N–Si bond of the(Me3Si)2N substituents in 1,changing the guanidinate ligands automatically from mono-anionic to di-anionic and remarkably lengthening the bond length of theμ-N_(2).Characteristic studies and DFT calculations were performed to reveal that the di-anionic guanidinate ligands stabilized the geometry of 2 and increased the charge density on the bridging dinitrogen.展开更多
Two chelating guanidinate-based dysprosium(Ⅲ)complexes,namely the monomeric{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)_(2)Li(THF)_(2) 1 and the dimeric[{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)]_(2) 2,have been c...Two chelating guanidinate-based dysprosium(Ⅲ)complexes,namely the monomeric{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)_(2)Li(THF)_(2) 1 and the dimeric[{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)]_(2) 2,have been confirmed to be single-molecule magnets.Moreover,the alteration from 1 to 2 leads to an obvious mitigated quantum tunnelling of magnetization at zero field of the hysteresis loop and much enhanced magnetic relaxation barrier(up to 312 K).5%dilution with the yttrium(Ⅲ)analogue for 2 shows no clear change for the hysteresis,indicating the single-ion nature of the magnetic behavior.展开更多
Density functional theory (DFT) calculations were carried out on the compounds Cp2Ln-guan for Ln=Y, Lu, Yb, Dy and Gd, [guan=(iPrN)2CN(iPr)2]. The results were compared with the X-ray structures that were available fr...Density functional theory (DFT) calculations were carried out on the compounds Cp2Ln-guan for Ln=Y, Lu, Yb, Dy and Gd, [guan=(iPrN)2CN(iPr)2]. The results were compared with the X-ray structures that were available from the literature; the calculations reproduced quite well the experimental structural features in these complexes exhibiting distorted tetrahedron geometry. The calculated evolution of the Ln-guan bond as a function of the cation showed that lanthanide-ligand distances increased with the increa...展开更多
Reactions of 1,3-diisopropylcarbodiimide with alkali metal amides, MN(SiMe3)2 (M=Li or Na) in hexane or THF produced the alkali metal guanidinates { (i-PrN)2C [N(SiMe3)2]Li }2 (1) and { (i-PrN)2C[N(SiMe3...Reactions of 1,3-diisopropylcarbodiimide with alkali metal amides, MN(SiMe3)2 (M=Li or Na) in hexane or THF produced the alkali metal guanidinates { (i-PrN)2C [N(SiMe3)2]Li }2 (1) and { (i-PrN)2C[N(SiMe3)2]Na(THF) } 2 (2) in nearly quantitative yields. Both complexes 1 and 2 were well characterized by elemental analysis, IR spectra, ^1H and ^13C NMR spectra, and X-ray diffraction. It was found that the guanidinates adopt different coordination modes in these complexes.展开更多
Addition of one equivalent of LiN(i-Pr)2 or LiN(CH2)5 to carbodiimides, RN=C=NR [R=cyclohexyl (Cy), isopropyl (i-Pr)], generated the corresponding lithium of tetrasubstituted guanidinates {Li[RNC(N R^′2)NR]...Addition of one equivalent of LiN(i-Pr)2 or LiN(CH2)5 to carbodiimides, RN=C=NR [R=cyclohexyl (Cy), isopropyl (i-Pr)], generated the corresponding lithium of tetrasubstituted guanidinates {Li[RNC(N R^′2)NR](THF)}2 [R=i-Pr, N R^′2=N(i-Pr)2 (1), N(CH2)5 (2); R=Cy, N R^′2=N(i-Pr)2 (3), N(CH2)5 (4)]. Treatment of ZrCl4 with freshly prepared solutions of their lithium guanidinates provided a series of bis(guanidinate) complexes of Zr with the general formula Zr[RNC(N R^′2)NR]2Cl2 [R=i-Pr, N R^′2=N(i-Pr)2 (5), N(CH2)5 (6); R=Cy, N R^′2=N(i-Pr)2 (7), N(CH2)5 (8)]. Complexes 1, 2, 5-8 were characterized by elemental analysis, IR and ^1H NMR spectra. The molecular structures of complexes 1, 7 and 8 were further determined by X-ray diffraction studies.展开更多
The reaction of [(SiMe3)2NC(NC6H11)2]Li with SmCl3 in 2:1 molar ratio in THF gave bis(N,N-cyclohexyl-N创-bis(trimethylsilyl)samarium chloride, [(SiMe3)2NC(NC6H11)2]Sm(m- Cl)2Li(THF)2 1 in 85% isolated yield as pale-ye...The reaction of [(SiMe3)2NC(NC6H11)2]Li with SmCl3 in 2:1 molar ratio in THF gave bis(N,N-cyclohexyl-N创-bis(trimethylsilyl)samarium chloride, [(SiMe3)2NC(NC6H11)2]Sm(m- Cl)2Li(THF)2 1 in 85% isolated yield as pale-yellow crystals. Complex 1 was structurally characte- rized by single-crystal X-ray diffraction analysis at 289(2) K. It crystallizes in monoclinic, space group C2/c with a = 26.886(3), b = 13.677(2), c = 19.465(3) ? b = 120.26(1), V = 6182(2) ?, Z = 4, Mr = 1105.84, Dc = 1.188 g/cm3, F(000) = 2340 and m(MoKa) = 1.150 mm-1. The structure was refined to R = 0.0378 and wR = 0.0885 for 4342 observed reflections with I > 2s(I). The coordination geometry of samarium ion can be best described as a distorted pseudooctahedron.展开更多
One new Ni(Ⅱ) complex [Ni(H2L)]Cl(H2O)3 based on one in-situ synthesized Schiff base ligand H3L (H3L = bis(benzyl-2-pyridylidene)-diaminoguanidine) was prepared and structurally characterized by single-crys...One new Ni(Ⅱ) complex [Ni(H2L)]Cl(H2O)3 based on one in-situ synthesized Schiff base ligand H3L (H3L = bis(benzyl-2-pyridylidene)-diaminoguanidine) was prepared and structurally characterized by single-crystal X-ray diffraction method. The complex crystallizes in the monoclinic system, space group C2/c with a = 27.944(7), b = 7.7405(19), c = 25.999(7) ,A, β = 115.545(2)°, V = 5074(2) A^3, Mr = 566.69, Z = 8, Dc = 1.484 g/cm^3, F(000) = 2352,μ(MoKα) = 0.912 mm^-1, R = 0.0594 and wR = 0.1477 for 5145 observed reflections (1 〉 2σ(I)). The complex exhibits one mononuclear structure in which the Ni(Ⅱ) atom adopts a [NiN4] pseudo-planar square geometry. Interestingly, along the b axis, each two neighboring [Ni(H2L)]^+ units by an inverse center form pairs of molecules through the intermolecular benzene-pyridine π…π interactions.展开更多
The changes in the activity and the conformation of the hyperthermophilic esterase derived from aerobic thermophilic Aeropyrum pernix K1 ( APE1547 ) were studied during denaturation by guanidine hydrochlofide ( Gdn...The changes in the activity and the conformation of the hyperthermophilic esterase derived from aerobic thermophilic Aeropyrum pernix K1 ( APE1547 ) were studied during denaturation by guanidine hydrochlofide ( GdnHC1 ) and urea. The denaturation course of APE1547 was followed by the steady-state and time resolved fluorescence methods. An increase in the denaturant concentration in the denatured system can significantly enhance the inactivation and unfolding of APE1547. The enzyme can be completely inactivated with a urea concentration of 2.7 mol/L or a GdnHCl concentration of 7.5 mol/L. The fluorescence emission maximum of the enzyme protein red shifts in magnitude to a maximum value(355 nm) when the concentration of GdnHCl is 5.1 mol/L. The experimental results indicate that APE1547 has a high resistance to urea. Unfolding of APE1547 in GdnHCI(4. 2-6.0 mol/L) was shown to be an irreversible process. The present results indicate that the ion pairs in this protein may be a key factor for the stability of this esterase.展开更多
A series of novel derivatives of ligustrazine linked with substituted benzoyl guanidine were synthesized. These compounds have not been reported in literature, and their chemical structures were confirmed by IR, ^1H N...A series of novel derivatives of ligustrazine linked with substituted benzoyl guanidine were synthesized. These compounds have not been reported in literature, and their chemical structures were confirmed by IR, ^1H NMR and MS. The results of NHE1 inhibitory activity test showed that compounds I2, I3, I4, I6, and I7 possess more potent NHE1 inhibitory activity than cariporide.展开更多
Compared to antiarrhythmic drugs, implantable cardioverter defibrillator (ICD) leads to a more significant im- provement in preventing ventricular arrhythmia in heart failure patients. However, an important question...Compared to antiarrhythmic drugs, implantable cardioverter defibrillator (ICD) leads to a more significant im- provement in preventing ventricular arrhythmia in heart failure patients. However, an important question has been raised that how to select appropriate patients for ICD therapy. 1-123 metaiodobenzylguanidine (MIBG) planar and SPECT imaging have shown great potentials to predict ventricular arrhythmia in heart failure patients by as- sessing the abnormalities of the sympathetic nervous system. Clinical trials demonstrated that several parameters measured from 1-123 MIBG planar and SPECT imaging, such as heart-to-mediastinum ratio, washout rate, defect score, and innervation/perfusion mismatch, predicted ventricular arrhythmias in heart failure patients. This paper introduces the current practice of ICD therapy and reviews the technical background of 1-123 MIBG planar and SPECT imaging and their clinical data in predicting ventricular arrhythmia.展开更多
GCP and APP were used as flame retardants for poplar wood and larch wood,and their flame retardancy(OI), permeability (Surface electron spectroscopy), water-re pellency and corrosion toward nail evaluated. The results...GCP and APP were used as flame retardants for poplar wood and larch wood,and their flame retardancy(OI), permeability (Surface electron spectroscopy), water-re pellency and corrosion toward nail evaluated. The results showed that GCP is in advance of APP. From the thermal analysis and char composition analysis, it is concluded that GCP mainly functions in condensed phase.展开更多
Efficient polymer supported synthesis of multi-substituted pyrimidine-4-one derivatives was described. Target products were produced from fluorenylmethoxycarbonyl(Fmoc) protected β-amino acid loaded on hydro- xymet...Efficient polymer supported synthesis of multi-substituted pyrimidine-4-one derivatives was described. Target products were produced from fluorenylmethoxycarbonyl(Fmoc) protected β-amino acid loaded on hydro- xymethyl resin through deprotection, N-alkylation, guanidine formation, and cleavage of 2,2,4,6,7-pentamethyl dihy-drobenzofuran-sulfonyl(Pbf) by trifluoracetic acid(TFA) followed with cyclization. The procedure has the advantages of easy operation, mild reaction conditions, and forming multiple substituents.展开更多
Chloroamidinium salts and a-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-(N,N-dialkylamino)oxazolines in m...Chloroamidinium salts and a-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-(N,N-dialkylamino)oxazolines in moderate to excellent yields without any catalyst. It is a simple and mild method for the syntheses of optically active oxazolines展开更多
A new compound, [(NH2)2C=NH2]+N(NO2)2-(GDN), was prepared by mixing ammonium dinitramide (ADN) and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions...A new compound, [(NH2)2C=NH2]+N(NO2)2-(GDN), was prepared by mixing ammonium dinitramide (ADN) and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy(E) and pre-exponential constant(A) of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion(Tb) of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.展开更多
The rheological behavior of polyhexamethylene guanidine hydrochloride (PHGC) and polyethylene guanidine stearate (PHGS) has been investigated using the capillary rheometer. It is shown that the polyelectrolyte melts a...The rheological behavior of polyhexamethylene guanidine hydrochloride (PHGC) and polyethylene guanidine stearate (PHGS) has been investigated using the capillary rheometer. It is shown that the polyelectrolyte melts are non-Newtonian of shear. thinning fluid. The melt viscosity, the flow activation energy and the flow temperature are high even if the molecular weight is not high. The melting viscosity of PHGC is higher than that of PHGS at the same experimental conditions. By comparison with the case of PHGS the non-Newtonian index of PHGC is smaller, the flow activation energy and the flow temperature of PHGC are higher, which was caused by the difference in their molecular structure.展开更多
In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized th...In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a ]pyrazin-3-amines, and then elucidated their structures based on their ~1H-NMR, ^(13)C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.展开更多
A new guanidine derivative,complanatin has been isolated from the seeds of Chinese traditional medicine Astragalus complanatus R.Br..Its structure was established on the basis of spectral data and X-ray crystallograph...A new guanidine derivative,complanatin has been isolated from the seeds of Chinese traditional medicine Astragalus complanatus R.Br..Its structure was established on the basis of spectral data and X-ray crystallographic analysis to be N-[3-carboxypropyl]-N-[3-methyl-2-butenyl]guanidine.展开更多
基金supported by the Foundation of Innovation Projects of USTS for Graduate StudentsJiangsu Key Laboratory for the Environment Functional Materialsa Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘Reaction of Ce(O-t-Bu)2(NO3)2 and sodium guanidinate GuaNa (Gua-=TMS2NC(NC6H11)2-) in THF affords the first guanidinate Ce(IV) complex of Ce2(O-t-Bu)7(Guaˊ) (1, Gua-=(C6H11NH)C(NC6H 11)(NH)-). It crystallizes in monoclinic, space group P21/n with a=15.2937(14), b=17.8409(16), c=19.0454(16), β=97.713(2)°, V=5149.6(8)3 , Z=4, Mr=1014.38, Dc=1.308 g/cm3 , μ=1.787 mm-1 , F(000)=2104, S=1.015, R=0.0451 and wR=0.0901 (I 〉 2σ(I)). In the reaction the cleavage of TMS-N bonds happened unexpectedly.
基金supported by the Basic Science Center of Transformation Chemistry of Key Components of Air, the National Natural Science Foundation of China (21988101)supported by the High-performance Computing Platform of Peking University
文摘The synthesis,characterization,and theoretical studies of titanium-μ-N_(2) complexes with di-anionic guanidinate ligands were reported as the first example of its kind.Thus,with(Me_(3)Si)_(2)N-guanidinate ligands,the mono-anionic guanidinate-supported titanium-μ-N2complex 1 was obtained.Then,reduction of 1 with potassium afforded the di-anionic guanidinate-supported titanium-μ-N_(2) complex 2 via cleavage of one N–Si bond of the(Me3Si)2N substituents in 1,changing the guanidinate ligands automatically from mono-anionic to di-anionic and remarkably lengthening the bond length of theμ-N_(2).Characteristic studies and DFT calculations were performed to reveal that the di-anionic guanidinate ligands stabilized the geometry of 2 and increased the charge density on the bridging dinitrogen.
基金the Shenzhen Science and Technology Program(No.JCYJ20180306170859634)the National Natural Science Foundation of China(Nos.21773130,21801202,21971203 and 21620102002)+5 种基金the Key Scientific and Technological Innovation Team of Shaanxi Province(No.2020TD-001)the Key Laboratory Construction Program of Xi’an Municipal Bureau of Science and Technology(No.201805056ZD7CG40)the China Postdoctoral Science Foundation(Grants Nos.2019T120891,2017M623150 and 2018M643615)the Postdoctoral Foundation of Shaanxi Province(Grant No.2018BSHEDZZ100)the Shaanxi Postdoctoral Science Foundation(No.2017BSHTDZZ08)the Fundamental Research Funds for Central Universities.We also thank the Instrument Analysis Center of Xi'an Jiaotong University for the measurement on dilution ratio and the University of Manchester for elemental analyses measurement.
文摘Two chelating guanidinate-based dysprosium(Ⅲ)complexes,namely the monomeric{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)_(2)Li(THF)_(2) 1 and the dimeric[{(Me_(3)Si)_(2)NC(N^(i)Pr)_(2)}_(2)Dy(μ-CI)]_(2) 2,have been confirmed to be single-molecule magnets.Moreover,the alteration from 1 to 2 leads to an obvious mitigated quantum tunnelling of magnetization at zero field of the hysteresis loop and much enhanced magnetic relaxation barrier(up to 312 K).5%dilution with the yttrium(Ⅲ)analogue for 2 shows no clear change for the hysteresis,indicating the single-ion nature of the magnetic behavior.
文摘Density functional theory (DFT) calculations were carried out on the compounds Cp2Ln-guan for Ln=Y, Lu, Yb, Dy and Gd, [guan=(iPrN)2CN(iPr)2]. The results were compared with the X-ray structures that were available from the literature; the calculations reproduced quite well the experimental structural features in these complexes exhibiting distorted tetrahedron geometry. The calculated evolution of the Ln-guan bond as a function of the cation showed that lanthanide-ligand distances increased with the increa...
基金Project supported by the National Natural Science Foundation of China (Nos. 20632040, 20604023).
文摘Reactions of 1,3-diisopropylcarbodiimide with alkali metal amides, MN(SiMe3)2 (M=Li or Na) in hexane or THF produced the alkali metal guanidinates { (i-PrN)2C [N(SiMe3)2]Li }2 (1) and { (i-PrN)2C[N(SiMe3)2]Na(THF) } 2 (2) in nearly quantitative yields. Both complexes 1 and 2 were well characterized by elemental analysis, IR spectra, ^1H and ^13C NMR spectra, and X-ray diffraction. It was found that the guanidinates adopt different coordination modes in these complexes.
基金Project supported by the National Natural Science Foundation of China (No. 20472063).
文摘Addition of one equivalent of LiN(i-Pr)2 or LiN(CH2)5 to carbodiimides, RN=C=NR [R=cyclohexyl (Cy), isopropyl (i-Pr)], generated the corresponding lithium of tetrasubstituted guanidinates {Li[RNC(N R^′2)NR](THF)}2 [R=i-Pr, N R^′2=N(i-Pr)2 (1), N(CH2)5 (2); R=Cy, N R^′2=N(i-Pr)2 (3), N(CH2)5 (4)]. Treatment of ZrCl4 with freshly prepared solutions of their lithium guanidinates provided a series of bis(guanidinate) complexes of Zr with the general formula Zr[RNC(N R^′2)NR]2Cl2 [R=i-Pr, N R^′2=N(i-Pr)2 (5), N(CH2)5 (6); R=Cy, N R^′2=N(i-Pr)2 (7), N(CH2)5 (8)]. Complexes 1, 2, 5-8 were characterized by elemental analysis, IR and ^1H NMR spectra. The molecular structures of complexes 1, 7 and 8 were further determined by X-ray diffraction studies.
文摘The reaction of [(SiMe3)2NC(NC6H11)2]Li with SmCl3 in 2:1 molar ratio in THF gave bis(N,N-cyclohexyl-N创-bis(trimethylsilyl)samarium chloride, [(SiMe3)2NC(NC6H11)2]Sm(m- Cl)2Li(THF)2 1 in 85% isolated yield as pale-yellow crystals. Complex 1 was structurally characte- rized by single-crystal X-ray diffraction analysis at 289(2) K. It crystallizes in monoclinic, space group C2/c with a = 26.886(3), b = 13.677(2), c = 19.465(3) ? b = 120.26(1), V = 6182(2) ?, Z = 4, Mr = 1105.84, Dc = 1.188 g/cm3, F(000) = 2340 and m(MoKa) = 1.150 mm-1. The structure was refined to R = 0.0378 and wR = 0.0885 for 4342 observed reflections with I > 2s(I). The coordination geometry of samarium ion can be best described as a distorted pseudooctahedron.
基金This research was supported by the State Key Laboratory of Structural Chemistry, the Chinese Academy of Sciences (CAS), the National Science and Technology of China (001CB1089), the NNSFC (20273073, 20333070, 90206040) and NSF of Fujian Province (2005HZ01-1, 2004HZ01-1, 2003J042 and 2004J041)
文摘One new Ni(Ⅱ) complex [Ni(H2L)]Cl(H2O)3 based on one in-situ synthesized Schiff base ligand H3L (H3L = bis(benzyl-2-pyridylidene)-diaminoguanidine) was prepared and structurally characterized by single-crystal X-ray diffraction method. The complex crystallizes in the monoclinic system, space group C2/c with a = 27.944(7), b = 7.7405(19), c = 25.999(7) ,A, β = 115.545(2)°, V = 5074(2) A^3, Mr = 566.69, Z = 8, Dc = 1.484 g/cm^3, F(000) = 2352,μ(MoKα) = 0.912 mm^-1, R = 0.0594 and wR = 0.1477 for 5145 observed reflections (1 〉 2σ(I)). The complex exhibits one mononuclear structure in which the Ni(Ⅱ) atom adopts a [NiN4] pseudo-planar square geometry. Interestingly, along the b axis, each two neighboring [Ni(H2L)]^+ units by an inverse center form pairs of molecules through the intermolecular benzene-pyridine π…π interactions.
文摘The changes in the activity and the conformation of the hyperthermophilic esterase derived from aerobic thermophilic Aeropyrum pernix K1 ( APE1547 ) were studied during denaturation by guanidine hydrochlofide ( GdnHC1 ) and urea. The denaturation course of APE1547 was followed by the steady-state and time resolved fluorescence methods. An increase in the denaturant concentration in the denatured system can significantly enhance the inactivation and unfolding of APE1547. The enzyme can be completely inactivated with a urea concentration of 2.7 mol/L or a GdnHCl concentration of 7.5 mol/L. The fluorescence emission maximum of the enzyme protein red shifts in magnitude to a maximum value(355 nm) when the concentration of GdnHCl is 5.1 mol/L. The experimental results indicate that APE1547 has a high resistance to urea. Unfolding of APE1547 in GdnHCI(4. 2-6.0 mol/L) was shown to be an irreversible process. The present results indicate that the ion pairs in this protein may be a key factor for the stability of this esterase.
文摘A series of novel derivatives of ligustrazine linked with substituted benzoyl guanidine were synthesized. These compounds have not been reported in literature, and their chemical structures were confirmed by IR, ^1H NMR and MS. The results of NHE1 inhibitory activity test showed that compounds I2, I3, I4, I6, and I7 possess more potent NHE1 inhibitory activity than cariporide.
文摘Compared to antiarrhythmic drugs, implantable cardioverter defibrillator (ICD) leads to a more significant im- provement in preventing ventricular arrhythmia in heart failure patients. However, an important question has been raised that how to select appropriate patients for ICD therapy. 1-123 metaiodobenzylguanidine (MIBG) planar and SPECT imaging have shown great potentials to predict ventricular arrhythmia in heart failure patients by as- sessing the abnormalities of the sympathetic nervous system. Clinical trials demonstrated that several parameters measured from 1-123 MIBG planar and SPECT imaging, such as heart-to-mediastinum ratio, washout rate, defect score, and innervation/perfusion mismatch, predicted ventricular arrhythmias in heart failure patients. This paper introduces the current practice of ICD therapy and reviews the technical background of 1-123 MIBG planar and SPECT imaging and their clinical data in predicting ventricular arrhythmia.
文摘GCP and APP were used as flame retardants for poplar wood and larch wood,and their flame retardancy(OI), permeability (Surface electron spectroscopy), water-re pellency and corrosion toward nail evaluated. The results showed that GCP is in advance of APP. From the thermal analysis and char composition analysis, it is concluded that GCP mainly functions in condensed phase.
基金Supported by the Scientific Forefront and Interdisciplinary Innovation Project of Jilin UniversityChina(No.421031531412)+1 种基金the Jilin Provincial Research Foundation for Basic Research China(No.3D109K856604)
文摘Efficient polymer supported synthesis of multi-substituted pyrimidine-4-one derivatives was described. Target products were produced from fluorenylmethoxycarbonyl(Fmoc) protected β-amino acid loaded on hydro- xymethyl resin through deprotection, N-alkylation, guanidine formation, and cleavage of 2,2,4,6,7-pentamethyl dihy-drobenzofuran-sulfonyl(Pbf) by trifluoracetic acid(TFA) followed with cyclization. The procedure has the advantages of easy operation, mild reaction conditions, and forming multiple substituents.
文摘Chloroamidinium salts and a-amino alcohols derived from commercially available tetraalkyl ureas and α-amino acids, respectively, can be used for the syntheses of optically active 2-(N,N-dialkylamino)oxazolines in moderate to excellent yields without any catalyst. It is a simple and mild method for the syntheses of optically active oxazolines
基金Supported by the National Natural Science Foundation of China(No.20803058)Xi’an Scientific and Technical Plan Foundation, China(No.YF07106).
文摘A new compound, [(NH2)2C=NH2]+N(NO2)2-(GDN), was prepared by mixing ammonium dinitramide (ADN) and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy(E) and pre-exponential constant(A) of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion(Tb) of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.
文摘The rheological behavior of polyhexamethylene guanidine hydrochloride (PHGC) and polyethylene guanidine stearate (PHGS) has been investigated using the capillary rheometer. It is shown that the polyelectrolyte melts are non-Newtonian of shear. thinning fluid. The melt viscosity, the flow activation energy and the flow temperature are high even if the molecular weight is not high. The melting viscosity of PHGC is higher than that of PHGS at the same experimental conditions. By comparison with the case of PHGS the non-Newtonian index of PHGC is smaller, the flow activation energy and the flow temperature of PHGC are higher, which was caused by the difference in their molecular structure.
基金supported by the National Nature Science Foundation of China(Nos.21576195 and 21776207)
文摘In this study, we applied a novel, mild, and convenient synthetic method involving the oxidative cyclization of 1-(pyrazin-2-yl)guanidine derivatives to produce [1,2,4]triazolo[4,3-a ]pyrazin-3-amines. We optimized the reaction procedure to easily obtain 5-chloro-[1,2,4]triazolo[4,3-a ]pyrazin-3-amine. Various types of halogenated pyrazines can successfully undergo this process. We synthesized a series of 1-(pyrazin-2-yl)guanidines and [1,2,4]triazolo[4,3-a ]pyrazin-3-amines, and then elucidated their structures based on their ~1H-NMR, ^(13)C-NMR, ESI-HRMS, and nuclear Overhauser effect spectra.
文摘A new guanidine derivative,complanatin has been isolated from the seeds of Chinese traditional medicine Astragalus complanatus R.Br..Its structure was established on the basis of spectral data and X-ray crystallographic analysis to be N-[3-carboxypropyl]-N-[3-methyl-2-butenyl]guanidine.