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Full-Text Articles in Life Sciences
Thermodynamics Of Effector Binding To Hemocyanin: Influence Of Temperature, Ariane Pott, Michael A. Menze, Manfred K. Grieshaber
Thermodynamics Of Effector Binding To Hemocyanin: Influence Of Temperature, Ariane Pott, Michael A. Menze, Manfred K. Grieshaber
Faculty Research & Creative Activity
Hemocyanins are allosterically regulated oxygen carriers freely dissolved in the blood of many crustaceans. The natural modulator urate accumulates under hypoxic conditions in the hemolymph of Homarus vulgaris, and increases the oxygen affinity of the respiratory pigment. Other non-physiological effectors such as caffeine, dimethylxanthines and methylxanthines are also known to modulate the oxygen-binding properties of hemocyanin. In order to gain insight into the thermodynamic driving forces of these interactions we analyzed the binding of several urate analogs to dodecameric hemocyanin at different temperatures by employing isothermal titration calorimetry (ITC). All investigated non-physiological effectors including caffeine, dimethylxanthines and methylxanthines bind exothermically …
Allosteric Models For Multimeric Proteins: Oxygen-Linked Effector Binding In Hemocyanin, Michael A. Menze, Nadja Hellman, Heinz Decker, Manfred K. Grieshaber
Allosteric Models For Multimeric Proteins: Oxygen-Linked Effector Binding In Hemocyanin, Michael A. Menze, Nadja Hellman, Heinz Decker, Manfred K. Grieshaber
Faculty Research & Creative Activity
In many crustaceans, changing concentrations of several low molecular weight compounds modulates hemocyanin oxygen binding, resulting in lower or higher oxygen affinities of the pigment. The nonphysiological effector caffeine and the physiological modulator urate, the latter accumulating in the hemolymph of the lobster Homarus Vulgaris during hypoxia, increase hemocyanin oxygen affinity and decrease cooperativity of oxygen binding. To derive a model that describes the mechanism of allosteric interaction between hemocyanin and oxygen in the presence of urate or caffeine, studies of oxygen, urate, and caffeine binding to hemocyanin were performed. Exposure of lobster hemocyanin to various pH values between 7.25 …
Binding Of Urate And Caffeine To Hemocyanin Analyzed By Isothermal Titration Calorimetry, Michael A. Menze, Nadja Hellmann, Heinz Decker, Manfred K. Grieshaber
Binding Of Urate And Caffeine To Hemocyanin Analyzed By Isothermal Titration Calorimetry, Michael A. Menze, Nadja Hellmann, Heinz Decker, Manfred K. Grieshaber
Faculty Research & Creative Activity
Haemocyanin serves as an oxygen carrier in the haemolymph of decapod crustaceans. The oxygen-binding behaviour of the pigment is modulated by the two major anaerobic metabolites, L-lactate and urate. The binding of these two metabolites to haemocyanin has been investigated mainly indirectly by following the effectorinduced changes in the oxygen-binding properties of the respiratory pigment. Only a few direct investigations of effector binding, employing ultracentrifugation techniques and equilibrium dialysis, have been carried out. No evidence for cooperative binding for either effector was detected using these methods. However, isothermal titration calorimetry (ITC) offers a useful tool to gain additional insight into …
Binding Of Urate And Caffeine To Hemocyanin Of The Lobster Homarus Vulgaris (E.) As Studied By Isothermal Titration Calorimetry †, Michael A. Menze, Nadja Hellmann, Heinz Decker, Manfred K. Grieshaber
Binding Of Urate And Caffeine To Hemocyanin Of The Lobster Homarus Vulgaris (E.) As Studied By Isothermal Titration Calorimetry †, Michael A. Menze, Nadja Hellmann, Heinz Decker, Manfred K. Grieshaber
Faculty Research & Creative Activity
Hemocyanin serves as an oxygen carrier in the hemolymph of the European lobster Homarus Vulgaris. The oxygen binding behavior of the pigment is modulated by metabolic effectors such as lactate and urate. Urate and caffeine binding to 12-meric hemocyanin (H. Vulgaris) was studied using isothermal titration calorimetry (ITC). Binding isotherms were determined for fully oxygenated hemocyanin between pH 7.55 and 8.15. No pH dependence of the binding parameters could be found for either effector. Since the magnitude of the Bohr effect depends on the urate concentration, the absence of any pH dependence of urate and caffeine binding to oxygenated hemocyanin …