Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modifi...Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.展开更多
Here,a dopa decarboxylase(DDC)from Harmonia axyridis was heterogeneously expressed in Escherichia coli for the efficient biosynthesis of dopamine.For the production of recombinant DDC,the cultivation conditions includ...Here,a dopa decarboxylase(DDC)from Harmonia axyridis was heterogeneously expressed in Escherichia coli for the efficient biosynthesis of dopamine.For the production of recombinant DDC,the cultivation conditions including IPTG concentration,temperature and induction time were optimized and obtained an optimal specific enzyme activity of 51.72 U·mg^(-1) crude extracts.After the purification of DDC with a recovery yield of 68.79%,its activity was further characterized.The Vmax,Km,Kcat,and Kcat/Km of DDC for d ihyd roxy pheny la la nine(dopa)were 0.02 mmol·ml^(-1)·s^(-1),2.328 mmol·ml^(-1),10435.90 s^(-1) and4482.77 ml,mmol respectively.The highest DDC activity was observed at the condition of pH 7.5 and 45℃.With the purified DDC,the feasibility to produce dopamine from L-dopa was evaluated.The optimal yield was determined at the following bioconversion conditions:pH of 7,0,the reaction temperature of 40℃,0.4 mmol·L^(-1) of PLP and 4 g·L^(-1) of L-dopa,Subsequently,a fed-batch process for the production of dopamine was developed and the effect of oxygen was evaluated.The titer,yield and productivity of dopamine reached up to 21.99 g·L^(-1)80.88%and 14.66 g·L^(-1)·h^(-1) at 90 min under anaerobic condition.展开更多
Idiopathic nondementing Parkinson’s disease (PD) is marked by progressive loss of dopaminergic neurons in the substantia nigra pars compacta and ventral tegmental area. Recent brain imaging work implicates these stru...Idiopathic nondementing Parkinson’s disease (PD) is marked by progressive loss of dopaminergic neurons in the substantia nigra pars compacta and ventral tegmental area. Recent brain imaging work implicates these structures in dopamine modulated networks subserving episodic memory. These findings are of relevance to PD because they suggest that dopamine depletion contributes to the disease-dependent decline in episodic memory, and therefore, this decline should, at least partially, be remediated by dopaminergic medication. Recognition memory (RM), recollection and familiarity during recognition was examined in 17 PD patients, 12 of whom were medicated with a D2 dopamine agonist (pramipexole or ropinirole) and l-dopa, with a further 5 PD control patients on l-dopa but no D2 agonist. Memory was tested “ON” and, following a period of medication withdrawal, “OFF” and compared to a group of 14 matched healthy volunteers (HV). The HVs were also tested twice in the absence of medication. The patients on the agonists PD showed significant impairments in recollection ON- and OFF-medication, whereas the l-dopa control patients exhibited a decline in OFF-recollection only. RM and familiarity were spared in both groups ON- and OFF-medication. These findings suggest that D2 dopamine agonists (combined with l-dopa) contribute to disease-dependent episodic memory impairment.展开更多
基金the Key Technologies R&D Program of Hubei Province(No.2005AA301B14)
文摘Fe3O4 magnetic nanoparticles were prepared by co-precipitation of Fe^2＋ and Fe^3＋ in an ammonia solution, and its size was about 36 nm measured by an atomic force microscope. Fe3O4 magnetic nanoparticles were modified by L-dopa or dopamine using sonication method. The analysis of FTIR clearly indicated the formation of Fe-O-C bond. Direct immobilization of trypsin （EC： 3.4.21.4） on Fe3O4 magnetic nanoparticles with L-dopa and dopamine spacer was investigated using glutaraldehyde as a coupling agent. No significant changes in the size and magnetic property of the three kinds of magnetic nanoparticles linked with or without trypsin were observed. The existence of the spacer molecule on magnetic nanoparticles could greatly improve the activity and the storage stability of bound trypsin through increasing the flexibility of enzyme and changing the microenvironment on nanoparticles surface compared to the naked magnetic nanoparticles.
基金funded by the National Natural Science Foundation of China(21576134 and 21706126)the National Key Research and Development Program(2016YFA0204300)。
文摘Here,a dopa decarboxylase(DDC)from Harmonia axyridis was heterogeneously expressed in Escherichia coli for the efficient biosynthesis of dopamine.For the production of recombinant DDC,the cultivation conditions including IPTG concentration,temperature and induction time were optimized and obtained an optimal specific enzyme activity of 51.72 U·mg^(-1) crude extracts.After the purification of DDC with a recovery yield of 68.79%,its activity was further characterized.The Vmax,Km,Kcat,and Kcat/Km of DDC for d ihyd roxy pheny la la nine(dopa)were 0.02 mmol·ml^(-1)·s^(-1),2.328 mmol·ml^(-1),10435.90 s^(-1) and4482.77 ml,mmol respectively.The highest DDC activity was observed at the condition of pH 7.5 and 45℃.With the purified DDC,the feasibility to produce dopamine from L-dopa was evaluated.The optimal yield was determined at the following bioconversion conditions:pH of 7,0,the reaction temperature of 40℃,0.4 mmol·L^(-1) of PLP and 4 g·L^(-1) of L-dopa,Subsequently,a fed-batch process for the production of dopamine was developed and the effect of oxygen was evaluated.The titer,yield and productivity of dopamine reached up to 21.99 g·L^(-1)80.88%and 14.66 g·L^(-1)·h^(-1) at 90 min under anaerobic condition.
文摘Idiopathic nondementing Parkinson’s disease (PD) is marked by progressive loss of dopaminergic neurons in the substantia nigra pars compacta and ventral tegmental area. Recent brain imaging work implicates these structures in dopamine modulated networks subserving episodic memory. These findings are of relevance to PD because they suggest that dopamine depletion contributes to the disease-dependent decline in episodic memory, and therefore, this decline should, at least partially, be remediated by dopaminergic medication. Recognition memory (RM), recollection and familiarity during recognition was examined in 17 PD patients, 12 of whom were medicated with a D2 dopamine agonist (pramipexole or ropinirole) and l-dopa, with a further 5 PD control patients on l-dopa but no D2 agonist. Memory was tested “ON” and, following a period of medication withdrawal, “OFF” and compared to a group of 14 matched healthy volunteers (HV). The HVs were also tested twice in the absence of medication. The patients on the agonists PD showed significant impairments in recollection ON- and OFF-medication, whereas the l-dopa control patients exhibited a decline in OFF-recollection only. RM and familiarity were spared in both groups ON- and OFF-medication. These findings suggest that D2 dopamine agonists (combined with l-dopa) contribute to disease-dependent episodic memory impairment.
