The thiol group and amino group at the active site of actinidin were modified by o-phthaldehyde to form a fluorescence group with excitation and emission wavelength maxima at 345 um and 416 nm respectively. The fluore...The thiol group and amino group at the active site of actinidin were modified by o-phthaldehyde to form a fluorescence group with excitation and emission wavelength maxima at 345 um and 416 nm respectively. The fluorescence group was then used to probe the conformational changes of the modified enzyme in guanidine hydrochloride (GuHCl) solution. Results were compared with the changes of activity as well as fluorescence and CD spectra of unmodified actinidin in GuHCl sloutions. It is shown that the conformational changes of the enayme active site parallel the enzyme inactivation, and both of them precede the conformatvonal changes of the enzyme as a whole revealed by fluorescence and CD spectra.展开更多
The use of the guanidine extractant LIX 7950 extracting copper and cyanide from alkaline cyanide solution was investigated.The extraction of copper and cyanide under different initial copper and extractant concentrati...The use of the guanidine extractant LIX 7950 extracting copper and cyanide from alkaline cyanide solution was investigated.The extraction of copper and cyanide under different initial copper and extractant concentrations was examined and the stoichiometric extraction constant of Cu(CN)32- with LIX 7950 was calculated.Both the distribution coefficient and the stoichiometric extraction constant of Cu(CN)3 2-with LIX 7950 decrease when the temperature is varied from 25℃to 45℃, indicating the extraction process is exothermic.The calculated enthalpy change of the reaction(-HΘ)is about-190 kJ/mol.The copper extraction isotherms under different molar ratios of cyanide to copper are established.The preferential extraction of Cu(CN)32- over Cu(CN)4 3-and CN -has been confirmed and a high cyanide-to-copper molar ratio tends to suppress copper loading. The loaded copper and cyanide can be stripped efficiently by the moderately strong NaOH solutions(0.5-1.0 mol/L)and the presence of NaCN in the stripping solution facilitates copper stripping.展开更多
文摘The thiol group and amino group at the active site of actinidin were modified by o-phthaldehyde to form a fluorescence group with excitation and emission wavelength maxima at 345 um and 416 nm respectively. The fluorescence group was then used to probe the conformational changes of the modified enzyme in guanidine hydrochloride (GuHCl) solution. Results were compared with the changes of activity as well as fluorescence and CD spectra of unmodified actinidin in GuHCl sloutions. It is shown that the conformational changes of the enayme active site parallel the enzyme inactivation, and both of them precede the conformatvonal changes of the enzyme as a whole revealed by fluorescence and CD spectra.
文摘The use of the guanidine extractant LIX 7950 extracting copper and cyanide from alkaline cyanide solution was investigated.The extraction of copper and cyanide under different initial copper and extractant concentrations was examined and the stoichiometric extraction constant of Cu(CN)32- with LIX 7950 was calculated.Both the distribution coefficient and the stoichiometric extraction constant of Cu(CN)3 2-with LIX 7950 decrease when the temperature is varied from 25℃to 45℃, indicating the extraction process is exothermic.The calculated enthalpy change of the reaction(-HΘ)is about-190 kJ/mol.The copper extraction isotherms under different molar ratios of cyanide to copper are established.The preferential extraction of Cu(CN)32- over Cu(CN)4 3-and CN -has been confirmed and a high cyanide-to-copper molar ratio tends to suppress copper loading. The loaded copper and cyanide can be stripped efficiently by the moderately strong NaOH solutions(0.5-1.0 mol/L)and the presence of NaCN in the stripping solution facilitates copper stripping.
