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Gomes ICP, Divino LDA, Rodrigues FM, Fleury CMF, Ducas ESA, Desordi JC, Iglesias BA, Santana RC, Monteiro CMO, Lopes WDZ, Gonçalves PJ, Souza GRL. Daylight photodynamic inactivation of cattle tick Rhipicephalus microplus by porphyrins: An alternative for the ectoparasite control. J Photochem Photobiol B 2024; 251:112847. [PMID: 38241947 DOI: 10.1016/j.jphotobiol.2024.112847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 12/22/2023] [Accepted: 01/12/2024] [Indexed: 01/21/2024]
Abstract
The bovine tick Rhipicephalus microplus, a primary ectoparasite of veterinary concern, contributes significantly to disease transmission and reduced cattle productivity, resulting in substantial economic losses. The overuse of chemical acaricides has led to the emergence of resistant strains, posing a considerable challenge to veterinary medicine. Consequently, the development of alternative parasite control methods is essential to ensure livestock quality and enhance food safety worldwide. Our study introduces an innovative approach to photodynamic inactivation (PDI) of the bovine tick, harnessing natural daylight for a potential field application. Reproductive parameters (female and egg mass, egg production index, and larval hatch) were evaluated in engorged female ticks under photodynamic action using the hematoporphyrin (HP) and tetra-cationic porphyrins free-base meso-tetra-ruthenated (4-pyridyl) (RuTPyP) and its zinc(II) complex (ZnRuTPyP) as photosensitizers (PS). The results showed that there was no significant difference between the groups treated with tetra‑ruthenium porphyrins and the control group. However, HP exhibits a control percentage of 97.9% at a concentration of 2.5 μmol.L-1, aligning with the expected control rates achieved by conventional chemical acaricides. Photophysical and physicochemical parameters such as the number of singlet oxygen produced and lipophilicity were discussed for each PS and related to tick control percentages. Furthermore, the interaction between HP and chitin, an important macromolecule presents in the tick's cuticle, considered as the primary target tick structure during PDI was observed by the absorption and fluorescence emission spectroscopic techniques. Therefore, the results presented here extend the potential for controlling R. microplus through photodynamic inactivation while utilizing sunlight as a source of natural irradiation.
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Affiliation(s)
| | - Lorena Dias Amor Divino
- Programa de Pós-Graduação em Ciências Animal, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | | | | | | | | | - Bernardo Almeida Iglesias
- Laboratório de Bioinorgânica e Materiais Porfirínicos, Universidade Federal de Santa Maria, Santa Maria, RS, Brazil
| | | | - Caio Márcio Oliveira Monteiro
- Programa de Pós-Graduação em Ciências Animal, Universidade Federal de Goiás, Goiânia, Goiás, Brazil; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | - Welber Daniel Zanetti Lopes
- Programa de Pós-Graduação em Ciências Animal, Universidade Federal de Goiás, Goiânia, Goiás, Brazil; Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Goiânia, Goiás, Brazil
| | - Pablo José Gonçalves
- Instituto de Química, Universidade Federal de Goiás, Goiânia, Brazil; Instituto de Física, Universidade Federal de Goiás, Goiânia, Brazil; Centro de Excelência em Hidrogênio e Tecnologias Energéticas Sustentáveis (CEHTES), Goiânia, GO, Brazil.
| | - Guilherme Rocha Lino Souza
- Programa de Pós-Graduação em Ciências Animal, Universidade Federal de Goiás, Goiânia, Goiás, Brazil; Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, Goiás, Brazil.
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Costa T, Fernandez-Villalba E, Izura V, Lucas-Ochoa AM, Menezes-Filho NJ, Santana RC, de Oliveira MD, Araújo FM, Estrada C, Silva V, Costa SL, Herrero MT. Combined 1-Deoxynojirimycin and Ibuprofen Treatment Decreases Microglial Activation, Phagocytosis and Dopaminergic Degeneration in MPTP-Treated Mice. J Neuroimmune Pharmacol 2020; 16:390-402. [PMID: 32564332 DOI: 10.1007/s11481-020-09925-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 05/14/2020] [Indexed: 12/28/2022]
Abstract
Inflammation is a predominant aspect of neurodegenerative diseases and experimental studies performed in animal models of Parkinson's disease (PD) suggesting that a sustained neuroinflammation exacerbates the nigrostriatal degeneration pathway. The central role of microglia in neuroinflammation has been studied as a target for potential neuroprotective drugs for PD, for example nonsteroidal anti-inflammatory drugs (NSAIDs) and matrix metalloproteinases (MMP) inhibitors that regulates microglial activation and migration. The aim of this study was to investigate the neuroprotective response of the iminosugar 1-deoxynojirimycin (1-DNJ) and compare its effect with a combined treatment with ibuprofen. MPTP-treated mice were orally dosed with ibuprofen and/or 1-DNJ 1. Open-field test was used to evaluate behavioral changes. Immunohistochemistry for dopaminergic neurons marker (TH+) and microglia markers (Iba-1+; CD68+) were used to investigate neuronal integrity and microglial activation in the substantia nigra pars compacta (SNpc). The pro-inflammatory cytokines TNF-α and IL-6 were analysed by qPCR. Treatments with either 1-DNJ or Ibuprofen alone did not reduce the damage induced by MPTP intoxication. However, combined treatment with 1-DNJ and ibuprofen prevents loss of mesencephalic dopaminergic neurons, decreases the number of CD68+/ Iba-1+ cells, the microglia/neurons interactions, and the pro-inflammatory cytokines, and improves behavioral changes when compared with MPTP-treated animals. In conclusion, these data demonstrate that the combined treatment with a MMPs inhibitor (1-DNJ) plus an anti-inflammatory drug (ibuprofen) has neuroprotective effects open for future therapeutic interventions. Graphical Abstract MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is a protoxicant that, after crossing the Blood Brain Barrier, is metabolized by astrocytic MAO-B to MPDP+, a pyridinium intermediate, which undergoes further two-electron oxidation to yield the toxic metabolite MPP+ (methyl-phenyltetrahydropyridinium) that is then selectively transported into nigral neurons via the mesencephalic dopamine transporter. In this study, we demonstrated that MPTP induced death of dopaminergic neurons, microgliosis, increase of gliapses, motor impairment and neuroinflammation in mice, which were inhibited by combined 1-deoxynojirimycin and ibuprofen treatment.
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Affiliation(s)
- Tcs Costa
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain.,Department of Biochemistry and Biophysics, Laboratory of Neurochemistry and Cell Biology, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil
| | - E Fernandez-Villalba
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain
| | - V Izura
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain
| | - A M Lucas-Ochoa
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain
| | - N J Menezes-Filho
- Department of Biochemistry and Biophysics, Laboratory of Neurochemistry and Cell Biology, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil
| | - R C Santana
- Department of Bioregulation, Laboratory of Neuroscience, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil
| | - M D de Oliveira
- Department of Biochemistry and Biophysics, Laboratory of Neurochemistry and Cell Biology, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil.,Faculty of Ceilandia, University of Brasilia - UnB, Brasilia, Federal District, Brazil
| | - F M Araújo
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain.,Department of Biochemistry and Biophysics, Laboratory of Neurochemistry and Cell Biology, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil
| | - C Estrada
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain
| | - Vda Silva
- Department of Biochemistry and Biophysics, Laboratory of Neurochemistry and Cell Biology, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil
| | - S L Costa
- Department of Biochemistry and Biophysics, Laboratory of Neurochemistry and Cell Biology, Institute of Health Sciences, Federal University of Bahia, Salvador, Bahia, 40110-100, Brazil.
| | - M T Herrero
- Clinical & Experimental Neuroscience (NiCE). Institute for Bio-Health Research of Murcia (IMIB), Institute for Aging Research (IUIE). School of Medicine, University of Murcia, Murcia, Spain.
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Leite De Barros Filho A, Moreira HT, Santos MK, Schmidt A, Santana RC, Rodrigues AJ, Maciel BC, Marin-Neto JA, Romano MMD. P187 Multimodality in tuberculous constrictive pericarditis. Eur Heart J Cardiovasc Imaging 2020. [DOI: 10.1093/ehjci/jez319.057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
CASE PRESENTATION
K.C.P., a 26 y.o. female, presenting dizziness and progressive dyspnea since 9 months ago. Physical examination showed hepatomegaly at 2 centimeters below the right inferior costal border, but without edema, cardiac murmurs or other findings. Electrocardiogram showed atria overload and diffuse ventricular repolarization abnormality. Chest X-ray revealed normal sized cardiac silhouette but with signs of pericardial calcification. Transthoracic echocardiogram revealed: enlargement of both atria, no signs of myocardial left ventricular (LV) hypertrophy; dilated inferior vena cava with minimal respiratory variation; septal bounce; septal e´= 17.20 cm/s, lateral e´= 6.09 cm/s; E/e" septal ratio = 3.9; E deceleration time = 144 ms; thickening and hyper-refringence of the pericardium with calcification adjacent to the lateral and inferior walls of the LV and the free wall of the right ventricle. For evaluation of thickness and extent of pericardial involvement, computed tomography (CT) was performed, showing gross calcifications of the pericardium, mainly in basal and lower portions, without pericardial effusion. Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement revealed areas suggestive of active inflammation adjacent to the basal wall of the LV. With this evidence of active inflammatory activity, the patient was treated empirically against the etiologic agent for tuberculosis. Because of progressively severe edema and dyspnea pericardiectomy was warranted providing relief of symptoms. DISCUSSION: The echocardiogram is the initial image exam for diagnosis and monitoring of pericardial conditions. It is a widely available, low-cost method that does not use ionizing radiation and allows a complete morphological and functional evaluation of the heart. However, in up to 20% of cases, pericardial thickening may not be detectable at echocardiography. CT allows a more accurate assessment of pericardial thickening, while CMR allows detection of active inflammatory process. CONCLUSION: A typical and illustrative clinical case of constrictive pericarditis is presented, where the multimodality of cardiac imaging was decisive for the diagnostic and therapeutic delineation.
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Affiliation(s)
- A Leite De Barros Filho
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - H T Moreira
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - M K Santos
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - A Schmidt
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - R C Santana
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - A J Rodrigues
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - B C Maciel
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - J A Marin-Neto
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
| | - M M D Romano
- Medical School of Ribeirao Preto, University of Sao Paulo, Cardiology, Ribeirao Preto, Brazil
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Santana RC, Machado AA, Martinelli ALC, Jordão AA, Ramalho LNZ, Vannucchi H. Assessment of indicators of vitamin A status in non-cirrhotic chronic hepatitis C patients. ACTA ACUST UNITED AC 2016; 49:e4785. [PMID: 26577844 PMCID: PMC4678655 DOI: 10.1590/1414-431x20154785] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Accepted: 05/10/2015] [Indexed: 12/31/2022]
Abstract
Subjects with chronic liver disease are susceptible to hypovitaminosis A due to
several factors. Therefore, identifying patients with vitamin deficiency and a
requirement for vitamin supplementation is important. Most studies assessing vitamin
A in the context of hepatic disorders are conducted using cirrhotic patients. A
cross-sectional study was conducted in 43 non-cirrhotic patients with chronic
hepatitis C to evaluate markers of vitamin A status represented by serum retinol,
liver retinol, and serum retinol-binding protein levels. We also performed the
relative dose-response test, which provides an indirect estimate of hepatic vitamin A
reserves. These vitamin A indicators were assessed according to the stage of liver
fibrosis using the METAVIR score and the body mass index. The sample study was
predominantly composed of male subjects (63%) with mild liver fibrosis (F1). The
relative dose-response test was <20% in all subjects, indicating vitamin A
sufficiency. Overweight or obese patients had higher serum retinol levels than those
with a normal body mass index (2.6 and 1.9 µmol/L, respectively; P<0.01). Subjects
with moderate liver fibrosis (F2) showed lower levels of serum retinol (1.9
vs 2.5 µmol/L, P=0.01) and retinol-binding
protein levels compared with those with mild fibrosis (F1) (46.3 vs
67.7 µg/mL, P<0.01). These results suggested an effect of being overweight on
serum retinol levels. Furthermore, more advanced stages of liver fibrosis were
related to a decrease in serum vitamin A levels.
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Affiliation(s)
- R C Santana
- Divisão de Infectologia, Departamento de Clínica Médica, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - A A Machado
- Divisão de Infectologia, Departamento de Clínica Médica, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - A L C Martinelli
- Divisão de Gastroenterologia, Departamento de Clínica Médica, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - A A Jordão
- Divisão de Nutrologia e Nutrição, Departamento de Clínica Médica, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - L N Z Ramalho
- Departamento de Patologia, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
| | - H Vannucchi
- Divisão de Nutrologia e Nutrição, Departamento de Clínica Médica, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
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Slavov SN, Vilar FC, Wagatsuma VMD, Santana RC, Machado AA, Fonseca BALD, Kashima S, Covas DT. Late emergence of A594V and L595W mutations related to ganciclovir resistance in a patient with HCMV retinitis and long-term HIV progression. ACTA ACUST UNITED AC 2015; 48:777-81. [PMID: 26270327 PMCID: PMC4568804 DOI: 10.1590/1414-431x20154507] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 03/13/2015] [Indexed: 11/22/2022]
Abstract
The emergence of ganciclovir (GCV) resistance during the treatment of human cytomegalovirus (HCMV) infection is a serious clinical challenge, and is associated with high morbidity and mortality. In this case report, we describe the emergence of two consecutive mutations (A594V and L595W) related to GCV resistance in a patient with HCMV retinitis and long-term HIV progression after approximately 240 days of GCV use. Following the diagnosis of retinitis, the introduction of GCV did not result in viral load reduction. The detected mutations appeared late in the treatment, and we propose that other factors (high initial HCMV load, previous GCV exposure, low CD4+ cell count), in addition to the presence of resistance mutations, may have contributed to the treatment failure of HCMV infection in this patient.
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Affiliation(s)
- S N Slavov
- Hemocentro de Ribeirão Preto, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - F C Vilar
- Divisão de Moléstias Infecciosas e Tropicais, Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - V M D Wagatsuma
- Laboratório de Hematologia Experimental, Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - R C Santana
- Divisão de Moléstias Infecciosas e Tropicais, Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - A A Machado
- Divisão de Moléstias Infecciosas e Tropicais, Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - B A L da Fonseca
- Divisão de Moléstias Infecciosas e Tropicais, Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - S Kashima
- Hemocentro de Ribeirão Preto, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
| | - D T Covas
- Hemocentro de Ribeirão Preto, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, BR
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Vanni T, Morejón KM, Santana RC, Melo LD, Ferrão SBRL, Amorim AP, Gaspar GG, Ponzi CC, Golin NA, Custódio FL, Marangoni ATD, Campos CP, Fonseca BAL. Comparison of the effectiveness of initial combined antiretroviral therapy with nelfinavir or efavirenz at a university-based outpatient service in Brazil. Braz J Med Biol Res 2008; 40:963-9. [PMID: 17653450 DOI: 10.1590/s0100-879x2007000700011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Accepted: 05/11/2007] [Indexed: 11/22/2022] Open
Abstract
Since there are some concerns about the effectiveness of highly active antiretroviral therapy in developing countries, we compared the initial combination antiretroviral therapy with zidovudine and lamivudine plus either nelfinavir or efavirenz at a university-based outpatient service in Brazil. This was a retrospective comparative cohort study carried out in a tertiary level hospital. A total of 194 patients receiving either nelfinavir or efavirenz were identified through our electronic database search, but only 126 patients met the inclusion criteria. Patients were included if they were older than 18 years old, naive for antiretroviral therapy, and had at least 1 follow-up visit after starting the antiretroviral regimen. Fifty-one of the included patients were receiving a nelfinavir-based regimen and 75 an efavirenz-based regimen as outpatients. Antiretroviral therapy was prescribed to all patients according to current guidelines. By intention-to-treat (missing/switch = failure), after a 12-month period, 65% of the patients in the efavirenz group reached a viral load <400 copies/mL compared to 41% of the patients in the nelfinavir group (P = 0.01). The mean CD4 cell count increase after a 12-month period was also greater in the efavirenz group (195 x 10(6) cells/L) than in the nelfinavir group (119 x 10(6) cells/L; P = 0.002). The efavirenz-based regimen was superior compared to the nelfinavir-based regimen. The low response rate in the nelfinavir group might be partially explained by the difficulty of using a regimen requiring a higher patient compliance (12 vs 3 pills a day) in a developing country.
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Affiliation(s)
- T Vanni
- Departamento de Clínica Médica, Hospital das Clínicas, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil
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Ribeiro MG, de Oliveira IR, Santana RC, Costa DT, Quarantini LC, de Castro E Silva E, Fregoneze JB. c-Fos expression identifies brain areas activated in response to nortriptyline. Mol Psychiatry 2007; 12:613-5. [PMID: 17592482 DOI: 10.1038/sj.mp.4001989] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Santana RC, Cunha RO, Carvalho JF, Vencato I, Calvo R. Single crystal EPR study of electronic structure and exchange interactions for copper(II)(L-arginine)2(SO4).(H2O)6: a model system to study exchange interactions between unpaired spins in proteins. J Inorg Biochem 2005; 99:415-23. [PMID: 15621273 DOI: 10.1016/j.jinorgbio.2004.10.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 10/04/2004] [Accepted: 10/13/2004] [Indexed: 11/15/2022]
Abstract
We report EPR measurements at 9.77 and 34.1 GHz in powder and single crystal samples of the ternary copper amino acid complex Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). The single crystal Electron Paramagnetic Resonance spectra display a single resonance for all magnetic field orientations in the ca and cb crystal planes. In the ab plane they display two resonances for most orientations of the magnetic field, and only one resonance for orientations close to the crystal axes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between copper ions. From the characteristics of the collapse and the angular dependences of the position and width of the resonances we evaluate the g-tensors of the copper molecules and estimate exchange interactions |J(1)/k(B)|=0.9 K and |J(2)/k(B)|=0.009 K between copper neighbors at 5.908 A and at 15.684 A, respectively. J(1) is assigned to a syn-anti equatorial-apical carboxylate bridge with a total bond length of 7.133 A. J(2) is assigned to a long bridge of 12 atoms with a total bond length of 19.789 A, that includes two hydrogen bonds. The results are discussed in terms of the crystal and electronic structure of Cu(L-arginine)(2)(SO(4)).(H(2)O)(6). We show that J(2) is in excellent agreement with the observed magnetic interaction between the reduced quinone acceptors in the photosynthetic reaction center protein of the bacterium Rb. sphaeroides, which is transmitted along a similar chemical path containing two hydrogen bonds. Our findings indicate that it is valid to estimate values for the exchange interactions between redox centers in proteins transmitted along long chemical paths containing sigma and H-bonds, from data obtained in model systems, and emphasize the importance of measuring exchange interactions in biologically relevant model systems.
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Affiliation(s)
- R C Santana
- Universidade Federal de Goiás, Instituto de Física, CP 131, Goiânia, Goiás 74001-970, Brazil.
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