The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration lea...The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase展开更多
BACKGROUND： Parkinson＇s disease （PD） is a common, age-dependent degenerative neurological disorder impairing motor control function and cognition. A key pathology of PD is a degeneration of the nigrostriatal dopam...BACKGROUND： Parkinson＇s disease （PD） is a common, age-dependent degenerative neurological disorder impairing motor control function and cognition. A key pathology of PD is a degeneration of the nigrostriatal dopamine system, leading to a severe dopamine denervation in the striatum and dynsfunction of the striatal neural circuits. OBJECTIVE： To better understand the pathophysiology of the nigrostriatal dopamine denervation and to discover better treatments, animal PD models are needed. METHODS： The authors＇ original research on the transcription factor Pitx3 null mutant mice and the relevant literature were reviewed. RESULTS： An important feature of an animal PD model is the severe, PD-like nigrostriatal dopamine denervation. This feature is provided in the transcription factor Pitx3 null mutant mice. These mice have a severe and bilateral nigral dopamine neuron loss and dopamine denervation in the dorsal striatum, while the dopamine neuron loss in the ventral tegmental area and dopamine denervation in the ventral striatum are moderate, creating a dorsal-ventral dopamine loss gradient and mimicking the dopamine denervation pattern in PD. Pitx3 null mice show motor function deficits in the balance beam and pole tests and these deficits are reversed by L-3,4-dihydroxyphenylalanine （L-dopa）. These mice also show impaired cognitive functions as indicated by reduced motor learning and avoidance memory. L-dopa, D 1 agonists and, to a lesser extent, D2 agonists, induce normal horizontal movements （walking） and also dyskinesia-like movements consisting of vertical body trunk movements and waving paw movements. CONCLUSIONS： The easy-to-maintain Pitx3 null mice with an autogenic, consistent and gradient dopamine denervation are a convenient and suitable mouse model to study the consequences of dopamine loss in PD and to test dopaminergic replacement therapies for PD.展开更多
An L（3, 2, 1）-labeling of a graph G is a function from the vertex set V（G） to the set of all nonnegative integers such that ｜f（u）-f（v）｜≥3 if dG（u,v） = 1, ｜f（u）-f（v）｜≥2 if dG（u,v） = 2, and ｜f（u...An L（3, 2, 1）-labeling of a graph G is a function from the vertex set V（G） to the set of all nonnegative integers such that ｜f（u）-f（v）｜≥3 if dG（u,v） = 1, ｜f（u）-f（v）｜≥2 if dG（u,v） = 2, and ｜f（u）-f（v）｜≥1 if dG（u,v） = 3. The L（3, 2,1）-labeling problem is to find the smallest number λ3（G） such that there exists an L（3, 2,1）-labeling function with no label greater than it. This paper studies the problem for bipartite graphs. We obtain some bounds of λ3 for bipartite graphs and its subclasses. Moreover, we provide a best possible condition for a tree T such that λ3（T） attains the minimum value.展开更多
基金Supported by the Natural Science Foundation of Guangdong Province (No. 011563, No. 04020114).
文摘The inhibitory effect of ferulic acid on the diphenolase activity of mushroom tyrosinase and the kinetic behavior were studied with L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The inhibitor concentration leading to 50% relative activity lost （IC50） was estimated to be 0.15 mmol·L^-1. The inhibition mechanism obtained from Lineweaver-Burk plots shows that ferulic acid is a competitive inhibitor and the inhibition of tyrosinase by ferulic acid is a reversible reaction. The equilibrium constant for ferulic acid binding with the tyrosinase was determined to be 0.25 mmol·L^-1 for diphenolase. Keywords tyrosinase, ferulic acid, kinetics, inhibition, L-DOPA, diphenolase
文摘BACKGROUND： Parkinson＇s disease （PD） is a common, age-dependent degenerative neurological disorder impairing motor control function and cognition. A key pathology of PD is a degeneration of the nigrostriatal dopamine system, leading to a severe dopamine denervation in the striatum and dynsfunction of the striatal neural circuits. OBJECTIVE： To better understand the pathophysiology of the nigrostriatal dopamine denervation and to discover better treatments, animal PD models are needed. METHODS： The authors＇ original research on the transcription factor Pitx3 null mutant mice and the relevant literature were reviewed. RESULTS： An important feature of an animal PD model is the severe, PD-like nigrostriatal dopamine denervation. This feature is provided in the transcription factor Pitx3 null mutant mice. These mice have a severe and bilateral nigral dopamine neuron loss and dopamine denervation in the dorsal striatum, while the dopamine neuron loss in the ventral tegmental area and dopamine denervation in the ventral striatum are moderate, creating a dorsal-ventral dopamine loss gradient and mimicking the dopamine denervation pattern in PD. Pitx3 null mice show motor function deficits in the balance beam and pole tests and these deficits are reversed by L-3,4-dihydroxyphenylalanine （L-dopa）. These mice also show impaired cognitive functions as indicated by reduced motor learning and avoidance memory. L-dopa, D 1 agonists and, to a lesser extent, D2 agonists, induce normal horizontal movements （walking） and also dyskinesia-like movements consisting of vertical body trunk movements and waving paw movements. CONCLUSIONS： The easy-to-maintain Pitx3 null mice with an autogenic, consistent and gradient dopamine denervation are a convenient and suitable mouse model to study the consequences of dopamine loss in PD and to test dopaminergic replacement therapies for PD.
基金Supported by the Natural Science Foundation of Education Ministry of Anhui Province (No.KJ2010B138)the Foundation for the Excellent Young Talents of Anhui Province(No.2010SQRL136ZD)the Natural Science Foundation of Chuzhou University(No.2008kj013B)
基金The NSF (60673048) of China the NSF (KJ2009B002,KJ2009B237Z) of Education Ministry of Anhui Province.
文摘An L（3, 2, 1）-labeling of a graph G is a function from the vertex set V（G） to the set of all nonnegative integers such that ｜f（u）-f（v）｜≥3 if dG（u,v） = 1, ｜f（u）-f（v）｜≥2 if dG（u,v） = 2, and ｜f（u）-f（v）｜≥1 if dG（u,v） = 3. The L（3, 2,1）-labeling problem is to find the smallest number λ3（G） such that there exists an L（3, 2,1）-labeling function with no label greater than it. This paper studies the problem for bipartite graphs. We obtain some bounds of λ3 for bipartite graphs and its subclasses. Moreover, we provide a best possible condition for a tree T such that λ3（T） attains the minimum value.
