The obstinated amino acid,Boc-Asn(or Boc-Gln),was directly anchored onto the Merrifield's resin using DCHA as the base in present reaction.The yield(71.88%)of Boc-Asn-OCH_2-resin was much better than those(0-33.5%...The obstinated amino acid,Boc-Asn(or Boc-Gln),was directly anchored onto the Merrifield's resin using DCHA as the base in present reaction.The yield(71.88%)of Boc-Asn-OCH_2-resin was much better than those(0-33.5%)using Cs_2CO_3,KOH,KF.DEA and TEA as the base.which are efficient reagents for other amino acids in the same reaction.展开更多
The efficiency of TFMSA as a cleaving reagent for peptidyl resin(I-VIII)was evaluated by quantitative ninhydrin test of peptide substitution degree(SD)on resin.Under different conditions,such as variation of C-termina...The efficiency of TFMSA as a cleaving reagent for peptidyl resin(I-VIII)was evaluated by quantitative ninhydrin test of peptide substitution degree(SD)on resin.Under different conditions,such as variation of C-terminal residue,resin linkage,the temperature and reaction time etc.,TFMSA can be used very conveniently instead of HF in many cases.展开更多
Studies were carried out on the extraction characters of trivalent rare earths from chloride solutions using organophosphorus acids 2-ethylhexylphosphonic acid mono-（2-ethylhexyl） ester （HEHEHP） combined with [di-...Studies were carried out on the extraction characters of trivalent rare earths from chloride solutions using organophosphorus acids 2-ethylhexylphosphonic acid mono-（2-ethylhexyl） ester （HEHEHP） combined with [di-（2-ethylhexyl）-phosphoric acid （HDEHP）,isopropylphosphonic acid 1-hexyl-4-ethyloctyl ester （HHEOIPP）,bis（2,4,4-trimethylpentyl）-phosphinic acid （Cyanex 272）,bis（2,4,4-trimethypentyl）-monothiophosphinic acid （Cyanex 302） or bis（2,4,4-trimethypentyl）-dithiophosphinic acid （Cyanex 301）] as extractants. The effect of the equilibrium aqueous acidity on the extraction was studied. According to the corresponding separation factors for adjacent pairs of rare earths,it could be concluded that HEHEHP and Cyanex 272 could be employed for the separation of Tm（Ⅲ）,Yb（Ⅲ）,Lu（Ⅲ） from the other rare earths. Taking Yb（Ⅲ） as an example,based on the different stripping acid,the potential of the stripping was estimated.展开更多
The negative ion fast atom bombardment (NIFAB) mass spectra of mono-,di-saccharides and glycosides using phenylboronic acid (PBA) as reagent have been studied.In the ion source,PBA reacts stereospecifically with the m...The negative ion fast atom bombardment (NIFAB) mass spectra of mono-,di-saccharides and glycosides using phenylboronic acid (PBA) as reagent have been studied.In the ion source,PBA reacts stereospecifically with the molecules containing cis-vicinal glycols to form characteristic ions, from which the stereo-isomers of saccharides can be definitely distinguished.Disaccharides and glyco- sides with β-glycosidic linkage seem to be unfavorabale to react with PBA,therefore,by comparison of the abundances of the characteristic ions,the configuration of the glycosidic linkage in these compounds may be inferred.展开更多
基金The yield was evaluated by monitoring the SD(substitution degree of Asn on the resin)value from quantitative ninhydrin test5 after due time reaction and the de-Boc treatment.
文摘The obstinated amino acid,Boc-Asn(or Boc-Gln),was directly anchored onto the Merrifield's resin using DCHA as the base in present reaction.The yield(71.88%)of Boc-Asn-OCH_2-resin was much better than those(0-33.5%)using Cs_2CO_3,KOH,KF.DEA and TEA as the base.which are efficient reagents for other amino acids in the same reaction.
文摘The efficiency of TFMSA as a cleaving reagent for peptidyl resin(I-VIII)was evaluated by quantitative ninhydrin test of peptide substitution degree(SD)on resin.Under different conditions,such as variation of C-terminal residue,resin linkage,the temperature and reaction time etc.,TFMSA can be used very conveniently instead of HF in many cases.
基金Project supported by the Science and Technology Research Project of Hubei Provincial Department of Education (B20094007)Wuhan Mu-nicipal Institutions of Scientific Project (2008K018)
文摘Studies were carried out on the extraction characters of trivalent rare earths from chloride solutions using organophosphorus acids 2-ethylhexylphosphonic acid mono-（2-ethylhexyl） ester （HEHEHP） combined with [di-（2-ethylhexyl）-phosphoric acid （HDEHP）,isopropylphosphonic acid 1-hexyl-4-ethyloctyl ester （HHEOIPP）,bis（2,4,4-trimethylpentyl）-phosphinic acid （Cyanex 272）,bis（2,4,4-trimethypentyl）-monothiophosphinic acid （Cyanex 302） or bis（2,4,4-trimethypentyl）-dithiophosphinic acid （Cyanex 301）] as extractants. The effect of the equilibrium aqueous acidity on the extraction was studied. According to the corresponding separation factors for adjacent pairs of rare earths,it could be concluded that HEHEHP and Cyanex 272 could be employed for the separation of Tm（Ⅲ）,Yb（Ⅲ）,Lu（Ⅲ） from the other rare earths. Taking Yb（Ⅲ） as an example,based on the different stripping acid,the potential of the stripping was estimated.
文摘The negative ion fast atom bombardment (NIFAB) mass spectra of mono-,di-saccharides and glycosides using phenylboronic acid (PBA) as reagent have been studied.In the ion source,PBA reacts stereospecifically with the molecules containing cis-vicinal glycols to form characteristic ions, from which the stereo-isomers of saccharides can be definitely distinguished.Disaccharides and glyco- sides with β-glycosidic linkage seem to be unfavorabale to react with PBA,therefore,by comparison of the abundances of the characteristic ions,the configuration of the glycosidic linkage in these compounds may be inferred.
