Hematoporphyrin interacts with myoglobin and alters its functions
TL;DR: The binding parameters of hematoporphyrin, a photosensitizing drug used in photodynamic therapy, interacting with myoglobin, an oxygen storage protein, have been studied spectrofluorometrically and spectrophotometric.
Abstract: The binding parameters of hematoporphyrin, a photosensitizing drug used in photodynamic therapy, interacting with myoglobin, an oxygen storage protein, have been studied spectrofluorometrically and spectrophotometrically. Two concentration ranges of hematoporphyrin, representing significantly monomeric and aggregated (dimeric) states have been used. The binding affinity constant (K) decreases and the possible number of binding sites (p) increases as the porphyrin changes from significantly monomeric state to predominantly dimeric state. Titration of the protein with hematoporphyrin in a spectrophotometric study (differential spectroscopy) exhibits an isosbestic point indicating a ground state complex formation. The interaction leads to a conformational change of the protein as observed in a circular dichroism study. The hematoporphyrin-myoglobin interaction causes oxygen release from the protein and it varies with the stoichiometric ratio of the porphyrin:protein. Hematoporphyrin also increases the myoglobin-catalysed hydrogen peroxide-mediated oxidation of o-dianisidine and NADH. These findings on the effects of hematoporphrin-myoglobin interaction should be given due consideration in therapeutic uses of the porphyrin and its derivatives.
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TL;DR: Spectrophotometric studies reveal that protoporphyrin IX interacts with haemoglobin and myoglobin forming ground state complexes, which may have a role in establishing efficacy of therapeutic uses of porphyrins as well as in elucidating their mechanisms of action as therapeutic agents.
Abstract: Protoporphyrin IX and its derivatives are used as photosensitizers in the photodynamic therapy of cancer. Protoporphyrin IX penetrates into human red blood cells and releases oxygen from them. This leads to a change in the morphology of the cells. Spectrophotometric studies reveal that protoporphyrin IX interacts with haemoglobin and myoglobin forming ground state complexes. For both proteins, the binding affinity constant decreases, while the possible number of binding sites increases, as the aggregation state of the porphyrin is increased. The interactions lead to conformational changes of both haemoglobin and myoglobin as observed in circular dichroism studies. Upon binding with the proteins, protoporphyrin IX releases the heme-bound oxygen from the oxyproteins, which is dependent on the stoichiometric ratios of the porphyrin : protein. The peroxidase activities of haemoglobin and myoglobin are potentiated by the protein-porphyrin complexation. Possible mechanisms underlying the relation between the porphyrin-induced structural modifications of the heme proteins and alterations in their functional properties have been discussed. The findings may have a role in establishing efficacy of therapeutic uses of porphyrins as well as in elucidating their mechanisms of action as therapeutic agents.
37 citations
TL;DR: The results suggest that drug action on hemoglobin is influenced by glycation-induced structural modification of the protein.
Abstract: Trifluoperazine (TFZ), a phenothiazine drug, penetrates into human erythrocytes and releases oxygen by interaction with hemoglobin. TFZ-induced oxygen release from hyperglycemic erythrocytes isolated from diabetic patients is considerably less compared to that from the cells of normoglycemic individuals. In diabetes mellitus, hemoglobin is significantly glycated by glucose. Non-glycated hemoglobin, HbA0 and its major glycated analog, HbA1c have been separated from the blood samples of diabetic patients. TFZ releases considerable amount of oxygen from HbA0, but very little from HbA1c. Spectrofluorimetric studies reveal that TFZ forms excited state complexes with both HbA0 and HbA1c. Titration of HbA0 with TFZ in a spectrophotometric study exhibits two isosbestic points. Similar experiment with HbA1c causes gradual loss of the Soret peak without appearance of any isosbestic point indicating a possibility of heme loss during interaction, which is also supported by gel filtration experiment and SDS-PAGE experiment followed by heme staining. The results suggest that drug action on hemoglobin is influenced by glycation-induced structural modification of the protein.
37 citations
TL;DR: The effect of porphyrins on heme proteins should be given due consideration in elucidating the details of the mechanism of p Morphyrin actions in therapy.
Abstract: Two important porphyrins, protoporphyrin IX and hematoporphyrin IX, derivatives of which form the basis of photosensitization in the photodynamic therapy of cancer treatment, interact with two physiologically important heme proteins hemoglobin and myoglobin. The extent and modality of these interactions vary with the state of aggregation of the two porphyrins. Upon binding with these proteins, both the drugs change the protein conformations and release the heme-bound oxygen from the oxyproteins. At the same time, the peroxidase activities of these proteins are potentiated due to the protein-porphyrin complexation, as is found in case of horseradish peroxidase also. The effect of porphyrins on heme proteins should be given due consideration in elucidating the details of the mechanism of porphyrin actions in therapy.
25 citations
Cites background from "Hematoporphyrin interacts with myog..."
...This view is also supported by porphyrin-induced potentiation of horseradish peroxidase (HRP)-catalyzed oxidation of NADH [44–46]....
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...Both PP and HP release oxygen from hemoglobin and myoglobin [53, 55]....
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...Sil and Chakraborti [8, 55] and Sil et al. [53] have shown that the binding parameters of PP and HP with both hemoglobin and myoglobin change with the state of aggregation of the porphyrins....
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...It has been reported that PP and HP increase the myoglobin or hemoglobin-catalyzed hydrogen peroxide-mediated oxidation of o-dianisidine and NADH [54, 55]....
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...Another possibility for porphyrin-induced enhanced enzyme activity of hemoglobin and myoglobin has also been suggested [55]....
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TL;DR: The interaction between zinc ion and camel alpha-lactalbumin (α-La) has been studied using different techniques of fluorescence spectroscopy, circular dichroism, isothermal titration calorimetry, and differential scanning caloricimetry (DSC) as discussed by the authors.
Abstract: The interaction between zinc ion and camel alpha-lactalbumin (α-La) has been studied using different techniques of fluorescence spectroscopy, circular dichroism, isothermal titration calorimetry, and differential scanning calorimetry (DSC). There are two sets of independent binding sites for Zn2+, two ions bind with the binding constant of 4.53 × 104 M−1 and four ions with the binding constant of 963 M−1. The Protein-Zn2+complexation is an entropy-driven process. Circular dichroism studies do not show any significant change in the secondary structure of the protein after the binding of zinc ion on the α-La. The interaction leads to a conformational change of the protein and exposure of hydrophobic patches on α-Lato the solvent as observed in ANS fluorescence spectroscopy. DSC was applied to elucidate the effect of Zn2+ binding on the protein stability. Binding of Zinc ion to α-La induces a partially folded structure of protein. At the Zn2+/α-La molar ratio of 5 and 10, a mixture of native and partially folded structures is present. When the ratio reaches 20, all molecules adopt partially folded structure. Chemometric analysis confirmed the experimental results and provided insight into the process of denaturation of α-La via characterizing the native, intermediate, and denatured conformations in the presence of different concentrations of Zn2+ and different thermal conditions. Thermal stability of the partially folded structure of α-La in the presence of Zinc ion is lower than in the native protein.
14 citations
Additional excerpts
...2 [28, 29]: 1=ð1 hÞ 1⁄4 Ka L 1⁄2 t=h n Ka ð2Þ...
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TL;DR: This QCM-FIA system was shown to be a highly effective method for the investigation of interaction between biomacromolecules and the PDT photosensitizer, and provides a potential strategy for screening an efficient and less harmful photosenitizer for PDT application.
14 citations
References
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Book•
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01 May 1988
TL;DR: A comprehensive review of mechanisms of subcellular and tumor localization of photosensitizing agents, as well as of molecular, cellular, and tumor responses associated with photodynamic therapy, are discussed.
Abstract: Photodynamic therapy involves administration of a tumor-localizing photosensitizing agent, which may require metabolic synthesis (i.e., a prodrug), followed by activation of the agent by light of a specific wavelength. This therapy results in a sequence of photochemical and photobiologic processes that cause irreversible photodamage to tumor tissues. Results from preclinical and clinical studies conducted worldwide over a 25-year period have established photodynamic therapy as a useful treatment approach for some cancers. Since 1993, regulatory approval for photodynamic therapy involving use of a partially purified, commercially available hematoporphyrin derivative compound (Photofrin) in patients with early and advanced stage cancer of the lung, digestive tract, and genitourinary tract has been obtained in Canada, The Netherlands, France, Germany, Japan, and the United States. We have attempted to conduct and present a comprehensive review of this rapidly expanding field. Mechanisms of subcellular and tumor localization of photosensitizing agents, as well as of molecular, cellular, and tumor responses associated with photodynamic therapy, are discussed. Technical issues regarding light dosimetry are also considered.
4,580 citations
1,853 citations
"Hematoporphyrin interacts with myog..." refers methods in this paper
...The α-helical contents of Mb in the presence and absence of the porphyrin were estimated from the spectra according to the relation [30]:...
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667 citations
TL;DR: An overview of photosensitizers, photochemistry, photobiology, and the lasers involved in photodynamic therapy is provided.
Abstract: Photodynamic therapy (PDT) is a treatment modality that utilizes a photosensitizing drug activated by laser generated light, and is proving effective for oncologic and nononcologic applications. This report provides an overview of photosensitizers, photochemistry, photobiology, and the lasers involved in photodynamic therapy. Clinical and preclinical PDT studies involving Photofrin and various second generation photosensitizers are reviewed.
419 citations
"Hematoporphyrin interacts with myog..." refers background in this paper
...The photosensitizers are activated by visible light or near infrared light, yielding highly reactive photoexcited species, which causes oxidative damage to variety of cellular targets and a subsequent cell death resulting in tumor ablation [6, 7]....
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Book•
01 Jan 1979
TL;DR: Best and Taylor's physiological basis of medical practice is illustrated with a simple graph depicting the response of the immune system to treatment-enhancing drugs.
Abstract: Best and Taylor's physiological basis of medical practice , Best and Taylor's physiological basis of medical practice , کتابخانه دیجیتال جندی شاپور اهواز
294 citations