scholarly journals QM/MM Study of Thymidylate Synthase: Enzymatic Motions and the Temperature Dependence of the Rate Limiting Step†

2009 ◽  
Vol 113 (10) ◽  
pp. 2176-2182 ◽  
Author(s):  
Natalia Kanaan ◽  
Sergio Martí ◽  
Vicent Moliner ◽  
Amnon Kohen
Keyword(s):  
Temperature Dependence ◽  
Thymidylate Synthase ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

scholarly journals The influence of active site conformations on the hydride transfer step of the thymidylate synthase reaction mechanism

2015 ◽  
Vol 17 (46) ◽  
pp. 30793-30804 ◽  
Author(s):  
Katarzyna Świderek ◽  
Amnon Kohen ◽  
Vicent Moliner
Keyword(s):  
Reaction Mechanism ◽  
Thymidylate Synthase ◽  
Active Site ◽  
Hydride Transfer ◽  
Md Simulations ◽  
Concerted Mechanism ◽  
X Ray ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

QM/MM MD simulations from different X-ray structures support the concerted mechanism character in the rate limiting step of thymidylate synthase catalysis.

scholarly journals Seasonal cycle and temperature dependence of pinene oxidation products, dicarboxylic acids and nitrophenols in fine and coarse air particulate matter

2010 ◽  
Vol 10 (5) ◽  
pp. 13253-13286 ◽  
Author(s):  
Y. Zhang ◽  
L. Müller ◽  
R. Winterhalter ◽  
G. K. Moortgat ◽  
T. Hoffmann ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Temperature Dependence ◽  
Dicarboxylic Acids ◽  
Oxidation Products ◽  
Air Particulate Matter ◽  
Air Particulate ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Pinic Acid

Abstract. Filter samples of fine and coarse air particulate matter (PM) collected over a period of one year in central Europe (Mainz, Germany) were analyzed for water-soluble organic compounds (WSOCs), including the α- and β-pinene oxidation products pinic acid, pinonic acid and 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA), as well as a variety of dicarboxylic acids and nitrophenols. Seasonal variations and other characteristic features in fine, coarse, and total PM (TSP) are discussed with regard to aerosol sources and sinks in comparison to data from other studies and regions. The ratios of adipic acid and phthalic acid to azelaic acid indicate that the investigated samples were mainly influenced by biogenic sources. A strong Arrhenius-type correlation was found between the 3-MBTCA concentration and inverse temperature (R2=0.79, n=52, Ea=126±10 kJ mol−1, temperature range 275–300 K). Model calculations suggest that the temperature dependence observed for 3-MBTCA can be explained by enhanced photochemical production due to an increase of hydroxyl radical (OH) concentration with increasing temperature, whereas the influence of gas-particle partitioning appears to play a minor role. The results indicate that the OH-initiated oxidation of pinonic acid is the rate-limiting step in the formation of 3-MBTCA, and that 3-MBTCA may be a suitable tracer for the chemical aging of biogenic secondary organic aerosol (SOA) by OH radicals. An Arrhenius-type temperature dependence was also observed for the concentration of pinic acid (R2=0.60, n=56, Ea=84±9 kJ mol−1); it can be tentatively explained by the temperature dependence of biogenic pinene emission as the rate-limiting step of pinic acid formation.

scholarly journals Seasonal cycle and temperature dependence of pinene oxidation products, dicarboxylic acids and nitrophenols in fine and coarse air particulate matter

2010 ◽  
Vol 10 (16) ◽  
pp. 7859-7873 ◽  
Author(s):  
Y. Y. Zhang ◽  
L. Müller ◽  
R. Winterhalter ◽  
G. K. Moortgat ◽  
T. Hoffmann ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Temperature Dependence ◽  
Dicarboxylic Acids ◽  
Oxidation Products ◽  
Air Particulate Matter ◽  
Air Particulate ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Pinic Acid

Abstract. Filter samples of fine and coarse air particulate matter (PM) collected over a period of one year in central Europe (Mainz, Germany) were analyzed for water-soluble organic compounds (WSOCs), including the α- and β-pinene oxidation products pinic acid, pinonic acid and 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA), as well as a variety of dicarboxylic acids and nitrophenols. Seasonal variations and other characteristic features in fine, coarse, and total PM (TSP) are discussed with regard to aerosol sources and sinks in comparison to data from other studies and regions. The ratios of adipic acid and phthalic acid to azelaic acid indicate that the investigated aerosol samples were mainly influenced by biogenic sources. A strong Arrhenius-type correlation was found between the 3-MBTCA concentration and inverse temperature (R2 = 0.79, n = 52, Ea = 126 ± 10 kJ mol−1, temperature range 275–300 K). Model calculations suggest that the temperature dependence observed for 3-MBTCA can be explained by enhanced photochemical production due to an increase of hydroxyl radical (OH) concentration with increasing temperature, whereas the influence of gas-particle partitioning appears to play a minor role. The results indicate that the OH-initiated oxidation of pinonic acid is the rate-limiting step in the formation of 3-MBTCA, and that 3-MBTCA may be a suitable tracer for the chemical aging of biogenic secondary organic aerosol (SOA) by OH radicals. An Arrhenius-type temperature dependence was also observed for the concentration of pinic acid (R2 = 0.60, n = 56, Ea = 84 ± 9 kJ mol−1); it can be tentatively explained by the temperature dependence of biogenic pinene emission as the rate-limiting step of pinic acid formation.

Ornithine Decarboxylase Activity in Cultured Endothelial Cells Stimulated by Serum, Thrombin and Serotonin

1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro
Keyword(s):  
Endothelial Cells ◽  
Ornithine Decarboxylase ◽  
Decarboxylase Activity ◽  
Aortic Endothelial Cells ◽  
Ornithine Decarboxylase Activity ◽  
Rate Limiting Step ◽  
Bovine Aortic Endothelial Cells ◽  
Limiting Step ◽  
Rate Limiting ◽  
Serum Serotonin

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.

Dynamics of hepatic and peripheral insulin effects suggest common rate-limiting step in vivo

Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman
Keyword(s):  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting
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