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
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
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
Guanidine hydrochloride was chemically bonded to surface of modified silica by means of condensation with grafted amino groups. Ion-exchanging and complexing properties of the obtained adsorbent have been studied with...Guanidine hydrochloride was chemically bonded to surface of modified silica by means of condensation with grafted amino groups. Ion-exchanging and complexing properties of the obtained adsorbent have been studied with respect to cations of Zn(II), Cu(II), Pb(II), Cd(II), Co(II) and metal-containing oxoanions of W(VI), Mo(VI), Cr(VI), V(V). Optimum conditions for quantitative extraction of the studied ions were determined. The structure and composition of Co(II) and Cu(II) complexes on the surface of the synthesized adsorbent have been investigated. The possibility of quantitative determination of cobalt(II) and copper(II) trace amounts after their preconcentration by the synthesized adsorbent was demonstrated.展开更多
The massive use of polyhexamethylene guanidine(PHMG),as a typical bactericidal agent,raised environmental concerns to the public.This work comprehensively revealed the hormesis effects of PHMG occurred in waste activa...The massive use of polyhexamethylene guanidine(PHMG),as a typical bactericidal agent,raised environmental concerns to the public.This work comprehensively revealed the hormesis effects of PHMG occurred in waste activated sludge(WAS)on the generation of volatile fatty acids(VFAs)during anaerobic fermentation.The low level of PHMG(100 mg/g TSS)significantly promoted the VFAs generation(1283 mg COD/L,compared with 337 mg COD/L in the control)via synchronously facilitating the solubilization,hydrolysis,and acidification steps but inhibiting methanogenesis.Metagenomic analysis showed that the functional anaerobe(i.e.,Bacteroides,Macellibacteroide and Parabacteroide)and corresponding genetic expressions responsible for extracellular hydrolysis(i.e.,clp P),membrane transport(i.e.,ffh and gsp F),intracellular substrates metabolism(i.e.,ald and paa F)and VFAs biosynthesis(i.e.,ACACA and FASN)were enhanced in the optimal presence of PHMG.Moreover,the anaerobic species could respond and adapt to low PHMG stimuli via quorum sensing(i.e.,cqs A,rpf C and rpf G),and thus maintain the high microbial metabolic activities.However,they were unable to tolerate the toxicity of excessive PHMG,resulting in the extremely low VFAs production.This work enlightened the effects of emerging pollutants on WAS fermentation at the genetic levels,and provided guidance on the WAS treatment and resource recovery.展开更多
The effect of a novel alkaline TSV (through-silicon-via) slurry with guanidine hydrochloride (GH) on CMP (chemical mechanical polishing) was investigated. The novel alkaline TSV slurry was free of any inhibitors...The effect of a novel alkaline TSV (through-silicon-via) slurry with guanidine hydrochloride (GH) on CMP (chemical mechanical polishing) was investigated. The novel alkaline TSV slurry was free of any inhibitors. During the polishing process, the guanidine hydrochloride serves as an effective surface-complexing agent for TSV CMP applications, the removal rate of barrier (Ti) can be chemically controlled through tuned selectivity with respect to the removal rate of copper and dielectric, which is helpful to modifying the dishing and gaining an excellent topography performance in TSV manufacturing. In this paper, we mainly studied the working mechanism of the components of slurry and the skillful application guanidine hydrochloride in the TSV slurry.展开更多
A bridged bicydic compound (7), the key intermediate for the synthesis of ( - )-huperzine A (1), was prepared by diastereos-elective Michael-aldol annulation of β-keto ester (4) catalyzed by chiral guanidine (2). A v...A bridged bicydic compound (7), the key intermediate for the synthesis of ( - )-huperzine A (1), was prepared by diastereos-elective Michael-aldol annulation of β-keto ester (4) catalyzed by chiral guanidine (2). A variety of chiral catalysts, substrates and reaction conditions were tested.展开更多
Pathogen infection is the main cause of human morbidity and death.Traditional antibiotics usually sterilize bacteria in chemical ways,which tends to develop serious antibiotic resistance.Cationic polymers exhibit good...Pathogen infection is the main cause of human morbidity and death.Traditional antibiotics usually sterilize bacteria in chemical ways,which tends to develop serious antibiotic resistance.Cationic polymers exhibit good bacterial inhibition with less resistance,but often face severe cytotoxicity toward normal cells.The optimization of polymeric antimicrobials for enhanced bactericidal capacity and improved biocompatibility is quite meaningful.In addition,photodynamic therapy(PDT) is a therapeutic modality with less susceptibility to develop resistance.Herein,a typical commercial polymeric antimicrobial,polyhexamethylene guanidine(PHMG) was selected for current proof-of-concept optimization due to its excellent bactericidal capacity but moderate biocompatibility.Eosin-Y(EoS)was copolymerized to afford EoS-labeled polymer conjugates,poly(2-(dimethylamino) ethyl methacrylate-co-eosin),P(DMAEMA-co-EoS),which was conjugated with PHMG to afford a novel polymeric antimicrobial,P(DMAEMA-co-EoS)-b-PHMG-b-P(DMAEMA-co-EoS),noted as PEoS-PHMG.It could efficiently kill broad-spectrum bacteria by physical damage and photodynamic therapy.Compared with PHMG,the bacterial inhibition of PEoS-PHMG was potentiated after the functionalization.Furthermore,PEoS-PHMG exhibited low cytotoxicity and minimal hemolysis,which was demonstrated by cell viability assays toward LO2 cells and RAW 264.7 cells as well as hemolytic assays against red blood cells.These results confirmed that the resultant PEoS-PHMG could act as promising alternative antibacterial materials with excellent broad-spectrum bacterial inhibition and favorable biocompatibility.展开更多
The cold and heat denaturations of bovine β-lactoglobuhn A (β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCl) by differential scanning calorimelry (DSC) The experimental results are presented ...The cold and heat denaturations of bovine β-lactoglobuhn A (β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCl) by differential scanning calorimelry (DSC) The experimental results are presented and discussed.It is shown that the number of protons bound by the monomeric molecules of β-lg A was unchanged before and after its heat denaturation below pH 3,and that the activation energy of the heat denaturation was depressed owing to the presence of GuHCl.In the solutions with 2.50 and 3.06 mol/L of GuHCl,both the cold and heat denat-urations of β-lg A were observed.In comparison with the heat denaturation,the activation energy of cold denaturation was far lower and the number of GuHCl molecules bound by the unfolded polypeptide chains after cold denaturation increased a lot.The absolute value of the enthalpy of cold denaturation was larger than that of heat denaturation It was found by the analysis that the contribution to the total denaturational enthalpy of conformational change展开更多
Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the dena- turation of t...Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the dena- turation of two photosynthesis membrane proteins: CP43 and CP47. THz-TDS was proven to be useful in discriminating the different conformational states of given proteins with similar structure and in monitoring the denaturation process of proteins. Upon treatment with guanidine hydrochloride (GuHCl), a 1.8 THz peak appeared for CP47 and free chlorophyll a (Chl a). This peak was deemed to originate from the interaction between Chl a and GuHCl molecules. The Chl a molecules in CP47 interacted with GuHCl more easily than those in CP43.展开更多
The conformation changes of dihydrofolate reductase (DHFR) from chicken liver in guanidine hy-drochloride were monitored by protein intrinsic fluorescence, hydrophobic fluorescence probe TNS and limited proteol-ysis b...The conformation changes of dihydrofolate reductase (DHFR) from chicken liver in guanidine hy-drochloride were monitored by protein intrinsic fluorescence, hydrophobic fluorescence probe TNS and limited proteol-ysis by proteinase K. The kinetics of the enzyme denaturation were also studied and compared with its activity changes. It was indicated by the enhanced fluorescence of 2-p-toluidinylnaphthalene (TNS) that a subtle conforma-tional change of the enzyme in dilute GuHCl parallels GuHCl-induced activation. At GuHCl concentration higher than 0.75 mol/L, the conformational change can be detected by increased susceptibility of the enzyme to proteinase K, but no significant gross conformational change of the enzyme molecule is observed by intrinsic fluorescence up to a GuHCl concentration of 1.2 mol/L. The results suggest that the denaturation of DHFR by GuHCl does not follow strictly the two-state model. The enzyme seems to open up sequentially with increasing concentrations of denaturants, mainly at展开更多
The catalytic activity and activity changes during denaturation by guanidine hydrochloride of glyceraldehyde-3-phosphate dehydrogenase,lactate dehydrogenase and α-chymotrypsin in crystalline state and in solution hav...The catalytic activity and activity changes during denaturation by guanidine hydrochloride of glyceraldehyde-3-phosphate dehydrogenase,lactate dehydrogenase and α-chymotrypsin in crystalline state and in solution have been compared.The catalytic activities are lower in crystalline state than in solution. Enzymes in crystalline state are more stable than in solution during denaturation by guanidine hydrochloride.Ammonium sulfate has different effects on catalytic activities of different enzymes and shows protection on all enzymes studied during denaturation by guanidine hydrochloride.The protection is more obvious at high concentrations of guanidine hydrochloride than at low concentrations.It is suggested that the flexibility or mobility of enzyme is required for the catalytic activity and related to the stability of enzymes. Enzymes with less flexibility or mobility are more stable.展开更多
Ⅰ. INTRODUCTIONIn earlier publications from this laboratory it has been reported that during the denaturation of creatine kinase (ATP: creatine phosphotransferase EC 2.7.3.2) by guanidine and urea, the inactivation o...Ⅰ. INTRODUCTIONIn earlier publications from this laboratory it has been reported that during the denaturation of creatine kinase (ATP: creatine phosphotransferase EC 2.7.3.2) by guanidine and urea, the inactivation of the enzyme takes place at denaturant concentrations much lower than necessary to bring about noticeable conformational changes as detected by conventional physicochemical, methods. Moreover, at the same denaturant concentration, the inactivation rates are several orders of magnitude展开更多
A convenient one-step synthesis of five-membered or six-membered imino-protected cyclic guanidine via an intramolecular ring-closure reaction of alkyl diamine(2a-2g) with 1,3-diamino-protected methylisothiourea(1a ...A convenient one-step synthesis of five-membered or six-membered imino-protected cyclic guanidine via an intramolecular ring-closure reaction of alkyl diamine(2a-2g) with 1,3-diamino-protected methylisothiourea(1a and 1b) was established and investigated.Amino guanidine such as 3-(2-aminoethyl)-1,2-dibenzyloxycarbonylguanidine(4a) has been proved to be the intermediate of the reaction via utilizing mono-protected diamine as starting material.The intramolecular ring closure of 4a results in 2-benzyloxycarbonyliminoimidazolidine(3a).This new one-step synthesis has advantages of simple condition,easy workup procedure and reasonable yield.展开更多
The C2 domain originally referred to the second of four constant structural motifs in protein kinase C (PKC). Now this domain represents a large structural family sharing a homologous dimensional structure in many ...The C2 domain originally referred to the second of four constant structural motifs in protein kinase C (PKC). Now this domain represents a large structural family sharing a homologous dimensional structure in many proteins that play important roles in many organisms. The C2A domain is one of the two C2 domains of synaptotagmin I involved in the Ca 2+ regulation of exocytosis. This domain is mostly composed of β sheet except for a small fraction of α helix, and therefore provides an ideal model for a protein folding study. In this report, the unfolding equilibrium of the C2A domain in guanidine hydrochloride (GdnHCl) containing solutions has been studied using ultraviolet (UV) difference spectrum, fluorescence spectrum, size exclusion chromatography (SEC), and circular dichroism (CD) spectrum. The results suggest that unfolding of the C2A domain occurs as a two state process during GdnHCl titration. By examining the changes of both tertiary structure and secondary structure, no intermediates could be detected during this unfolding study. However, it has been found that the native state of the C2A domain has a large hydrophobic surface. This result suggests that as a fragment of a protein, the C2A domain itself may exist in a state with large hydrophobic surface. This hydrophobic surface may be the molecular basis for interaction between domains in the whole protein. Furthermore, the hydrophobic behavior may play a role during the oligomerization of synaptotagmin.展开更多
A novel and efficient[3+2]annulation of 2-substituted aziridines and N-tosyl cyanamides via a dominoregioselective ring-opening/5-exo-dig cyclization procedure has been developed,allowing the directpreparation of N_(2...A novel and efficient[3+2]annulation of 2-substituted aziridines and N-tosyl cyanamides via a dominoregioselective ring-opening/5-exo-dig cyclization procedure has been developed,allowing the directpreparation of N_(2)-unprotected five-membered cyclic guanidines in good to excellent yields under mildconditions without metals and strong bases.Moreover,the highly biologically interesting urea analoguescould also be conveniently obtained via hydrolysis of the produced guanidines.展开更多
To reduce the burden of denture stomatitis and oral candidiasis,an aqueous solution containing polyhexamethylene guanidine hydrochloride(PHMGH)was investigated as an antifungal disinfectant against the leading cause o...To reduce the burden of denture stomatitis and oral candidiasis,an aqueous solution containing polyhexamethylene guanidine hydrochloride(PHMGH)was investigated as an antifungal disinfectant against the leading cause of these oral conditions,Candida albicans.The solutions formulated with concentrations ranging from 0.125 to 0.50 wt%enabled increasing disinfection at the initial 5min-contact with 72h-mature candida biofilms formed on denture liner specimens.After 10 min-contact,the solution at lower concentration has reached total fungal elimination.The results also indicated that the denture liners preserved their mechanical property after the maximum contact time with the solution at the highest tested concentration.The PHMGH aqueous solutions at 0.125 wt%could be applied to promote interim denture liner disinfection without promoting the loss of materials’mechanical property.展开更多
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 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.
文摘Guanidine hydrochloride was chemically bonded to surface of modified silica by means of condensation with grafted amino groups. Ion-exchanging and complexing properties of the obtained adsorbent have been studied with respect to cations of Zn(II), Cu(II), Pb(II), Cd(II), Co(II) and metal-containing oxoanions of W(VI), Mo(VI), Cr(VI), V(V). Optimum conditions for quantitative extraction of the studied ions were determined. The structure and composition of Co(II) and Cu(II) complexes on the surface of the synthesized adsorbent have been investigated. The possibility of quantitative determination of cobalt(II) and copper(II) trace amounts after their preconcentration by the synthesized adsorbent was demonstrated.
基金financially supported by the National Natural Science Foundation of China(No.52070069)Jiangsu Province Natural Science Foundation(No.BK20211207)+3 种基金China Postdoctoral Science Foundation(No.2021M692423)Shanghai Post-doctoral Excellence Program(No.2020419)State Key Laboratory of Pollution Control and Resource Reuse Foundation(No.PCRRF20005)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),China。
文摘The massive use of polyhexamethylene guanidine(PHMG),as a typical bactericidal agent,raised environmental concerns to the public.This work comprehensively revealed the hormesis effects of PHMG occurred in waste activated sludge(WAS)on the generation of volatile fatty acids(VFAs)during anaerobic fermentation.The low level of PHMG(100 mg/g TSS)significantly promoted the VFAs generation(1283 mg COD/L,compared with 337 mg COD/L in the control)via synchronously facilitating the solubilization,hydrolysis,and acidification steps but inhibiting methanogenesis.Metagenomic analysis showed that the functional anaerobe(i.e.,Bacteroides,Macellibacteroide and Parabacteroide)and corresponding genetic expressions responsible for extracellular hydrolysis(i.e.,clp P),membrane transport(i.e.,ffh and gsp F),intracellular substrates metabolism(i.e.,ald and paa F)and VFAs biosynthesis(i.e.,ACACA and FASN)were enhanced in the optimal presence of PHMG.Moreover,the anaerobic species could respond and adapt to low PHMG stimuli via quorum sensing(i.e.,cqs A,rpf C and rpf G),and thus maintain the high microbial metabolic activities.However,they were unable to tolerate the toxicity of excessive PHMG,resulting in the extremely low VFAs production.This work enlightened the effects of emerging pollutants on WAS fermentation at the genetic levels,and provided guidance on the WAS treatment and resource recovery.
基金Project supported by the Major National Science and Technology Special Projects(No.2009ZX02308)the Fund Project of Hebei Provincial Department of Education,China(No.QN2014208)+1 种基金the Natural Science Foundation of Hebei Province,China(No.E2013202247)Colleges and Universities Scientific research project of Hebei Province,China(No.Z2014088)
文摘The effect of a novel alkaline TSV (through-silicon-via) slurry with guanidine hydrochloride (GH) on CMP (chemical mechanical polishing) was investigated. The novel alkaline TSV slurry was free of any inhibitors. During the polishing process, the guanidine hydrochloride serves as an effective surface-complexing agent for TSV CMP applications, the removal rate of barrier (Ti) can be chemically controlled through tuned selectivity with respect to the removal rate of copper and dielectric, which is helpful to modifying the dishing and gaining an excellent topography performance in TSV manufacturing. In this paper, we mainly studied the working mechanism of the components of slurry and the skillful application guanidine hydrochloride in the TSV slurry.
基金Project supported by Chinese Academy of Sciences and the National Natural Science Foundation of China(No.29725205).
文摘A bridged bicydic compound (7), the key intermediate for the synthesis of ( - )-huperzine A (1), was prepared by diastereos-elective Michael-aldol annulation of β-keto ester (4) catalyzed by chiral guanidine (2). A variety of chiral catalysts, substrates and reaction conditions were tested.
基金supported by the Natural Science Foundation for Distinguished Young Scholars of Guangdong Province(No.2016A030306013)the Pearl River Young Talents Program of Science and Technology in Guangzhou(No.201906010047)the National Key Research and Development Program of China(No.2017YFA0205200)。
文摘Pathogen infection is the main cause of human morbidity and death.Traditional antibiotics usually sterilize bacteria in chemical ways,which tends to develop serious antibiotic resistance.Cationic polymers exhibit good bacterial inhibition with less resistance,but often face severe cytotoxicity toward normal cells.The optimization of polymeric antimicrobials for enhanced bactericidal capacity and improved biocompatibility is quite meaningful.In addition,photodynamic therapy(PDT) is a therapeutic modality with less susceptibility to develop resistance.Herein,a typical commercial polymeric antimicrobial,polyhexamethylene guanidine(PHMG) was selected for current proof-of-concept optimization due to its excellent bactericidal capacity but moderate biocompatibility.Eosin-Y(EoS)was copolymerized to afford EoS-labeled polymer conjugates,poly(2-(dimethylamino) ethyl methacrylate-co-eosin),P(DMAEMA-co-EoS),which was conjugated with PHMG to afford a novel polymeric antimicrobial,P(DMAEMA-co-EoS)-b-PHMG-b-P(DMAEMA-co-EoS),noted as PEoS-PHMG.It could efficiently kill broad-spectrum bacteria by physical damage and photodynamic therapy.Compared with PHMG,the bacterial inhibition of PEoS-PHMG was potentiated after the functionalization.Furthermore,PEoS-PHMG exhibited low cytotoxicity and minimal hemolysis,which was demonstrated by cell viability assays toward LO2 cells and RAW 264.7 cells as well as hemolytic assays against red blood cells.These results confirmed that the resultant PEoS-PHMG could act as promising alternative antibacterial materials with excellent broad-spectrum bacterial inhibition and favorable biocompatibility.
基金Project supported by the National Natural Science Foundation of Chinaby the fund for excellent items under Director of the Institute of Chemistry
文摘The cold and heat denaturations of bovine β-lactoglobuhn A (β-lg A) has been studied in solutions of guanidine hydrochloride (GuHCl) by differential scanning calorimelry (DSC) The experimental results are presented and discussed.It is shown that the number of protons bound by the monomeric molecules of β-lg A was unchanged before and after its heat denaturation below pH 3,and that the activation energy of the heat denaturation was depressed owing to the presence of GuHCl.In the solutions with 2.50 and 3.06 mol/L of GuHCl,both the cold and heat denat-urations of β-lg A were observed.In comparison with the heat denaturation,the activation energy of cold denaturation was far lower and the number of GuHCl molecules bound by the unfolded polypeptide chains after cold denaturation increased a lot.The absolute value of the enthalpy of cold denaturation was larger than that of heat denaturation It was found by the analysis that the contribution to the total denaturational enthalpy of conformational change
基金the National Natural Science Foundation of China (Grant No. 39890390)
文摘Terahertz time-domain spectroscopy (THz-TDS) is a new technique in studying the conformational state of a molecule in recent years. In this work, we reported the first use of THz-TDS to examine the dena- turation of two photosynthesis membrane proteins: CP43 and CP47. THz-TDS was proven to be useful in discriminating the different conformational states of given proteins with similar structure and in monitoring the denaturation process of proteins. Upon treatment with guanidine hydrochloride (GuHCl), a 1.8 THz peak appeared for CP47 and free chlorophyll a (Chl a). This peak was deemed to originate from the interaction between Chl a and GuHCl molecules. The Chl a molecules in CP47 interacted with GuHCl more easily than those in CP43.
文摘The conformation changes of dihydrofolate reductase (DHFR) from chicken liver in guanidine hy-drochloride were monitored by protein intrinsic fluorescence, hydrophobic fluorescence probe TNS and limited proteol-ysis by proteinase K. The kinetics of the enzyme denaturation were also studied and compared with its activity changes. It was indicated by the enhanced fluorescence of 2-p-toluidinylnaphthalene (TNS) that a subtle conforma-tional change of the enzyme in dilute GuHCl parallels GuHCl-induced activation. At GuHCl concentration higher than 0.75 mol/L, the conformational change can be detected by increased susceptibility of the enzyme to proteinase K, but no significant gross conformational change of the enzyme molecule is observed by intrinsic fluorescence up to a GuHCl concentration of 1.2 mol/L. The results suggest that the denaturation of DHFR by GuHCl does not follow strictly the two-state model. The enzyme seems to open up sequentially with increasing concentrations of denaturants, mainly at
基金Project supported by Grant No. 9388006 of the National Natural Science Foundation of China and the China Foundation for Post-doctoral Studies.
文摘The catalytic activity and activity changes during denaturation by guanidine hydrochloride of glyceraldehyde-3-phosphate dehydrogenase,lactate dehydrogenase and α-chymotrypsin in crystalline state and in solution have been compared.The catalytic activities are lower in crystalline state than in solution. Enzymes in crystalline state are more stable than in solution during denaturation by guanidine hydrochloride.Ammonium sulfate has different effects on catalytic activities of different enzymes and shows protection on all enzymes studied during denaturation by guanidine hydrochloride.The protection is more obvious at high concentrations of guanidine hydrochloride than at low concentrations.It is suggested that the flexibility or mobility of enzyme is required for the catalytic activity and related to the stability of enzymes. Enzymes with less flexibility or mobility are more stable.
文摘Ⅰ. INTRODUCTIONIn earlier publications from this laboratory it has been reported that during the denaturation of creatine kinase (ATP: creatine phosphotransferase EC 2.7.3.2) by guanidine and urea, the inactivation of the enzyme takes place at denaturant concentrations much lower than necessary to bring about noticeable conformational changes as detected by conventional physicochemical, methods. Moreover, at the same denaturant concentration, the inactivation rates are several orders of magnitude
基金Project 81001366 supported by NSFC and basic scientific research foundation of Institute of Materia Medica(No.2009CHX07) for financial support.
文摘A convenient one-step synthesis of five-membered or six-membered imino-protected cyclic guanidine via an intramolecular ring-closure reaction of alkyl diamine(2a-2g) with 1,3-diamino-protected methylisothiourea(1a and 1b) was established and investigated.Amino guanidine such as 3-(2-aminoethyl)-1,2-dibenzyloxycarbonylguanidine(4a) has been proved to be the intermediate of the reaction via utilizing mono-protected diamine as starting material.The intramolecular ring closure of 4a results in 2-benzyloxycarbonyliminoimidazolidine(3a).This new one-step synthesis has advantages of simple condition,easy workup procedure and reasonable yield.
基金Supported by the National Key Basic Research Specific Foundation of China(No.G19990 75 6 0 7)
文摘The C2 domain originally referred to the second of four constant structural motifs in protein kinase C (PKC). Now this domain represents a large structural family sharing a homologous dimensional structure in many proteins that play important roles in many organisms. The C2A domain is one of the two C2 domains of synaptotagmin I involved in the Ca 2+ regulation of exocytosis. This domain is mostly composed of β sheet except for a small fraction of α helix, and therefore provides an ideal model for a protein folding study. In this report, the unfolding equilibrium of the C2A domain in guanidine hydrochloride (GdnHCl) containing solutions has been studied using ultraviolet (UV) difference spectrum, fluorescence spectrum, size exclusion chromatography (SEC), and circular dichroism (CD) spectrum. The results suggest that unfolding of the C2A domain occurs as a two state process during GdnHCl titration. By examining the changes of both tertiary structure and secondary structure, no intermediates could be detected during this unfolding study. However, it has been found that the native state of the C2A domain has a large hydrophobic surface. This result suggests that as a fragment of a protein, the C2A domain itself may exist in a state with large hydrophobic surface. This hydrophobic surface may be the molecular basis for interaction between domains in the whole protein. Furthermore, the hydrophobic behavior may play a role during the oligomerization of synaptotagmin.
基金support from the Natural Science Foundation of Henan Province(grant no.212300410152)the Key Scientific and Technological Project of Henan Province(grant no.212102110439)+1 种基金Henan University of Animal Husbandry and Economy(grant no.2019HNUAHEDF011 and XKYCXJJ2020006)the Key Scientific Research Project for Colleges and Universities of Henan Province(grant no.22B150005)。
文摘A novel and efficient[3+2]annulation of 2-substituted aziridines and N-tosyl cyanamides via a dominoregioselective ring-opening/5-exo-dig cyclization procedure has been developed,allowing the directpreparation of N_(2)-unprotected five-membered cyclic guanidines in good to excellent yields under mildconditions without metals and strong bases.Moreover,the highly biologically interesting urea analoguescould also be conveniently obtained via hydrolysis of the produced guanidines.
文摘To reduce the burden of denture stomatitis and oral candidiasis,an aqueous solution containing polyhexamethylene guanidine hydrochloride(PHMGH)was investigated as an antifungal disinfectant against the leading cause of these oral conditions,Candida albicans.The solutions formulated with concentrations ranging from 0.125 to 0.50 wt%enabled increasing disinfection at the initial 5min-contact with 72h-mature candida biofilms formed on denture liner specimens.After 10 min-contact,the solution at lower concentration has reached total fungal elimination.The results also indicated that the denture liners preserved their mechanical property after the maximum contact time with the solution at the highest tested concentration.The PHMGH aqueous solutions at 0.125 wt%could be applied to promote interim denture liner disinfection without promoting the loss of materials’mechanical property.