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1.
Hum Reprod ; 34(5): 834-841, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-30927424

RESUMO

STUDY QUESTION: What is the prevalence and the relationship of anti-sperm antibodies (ASA), screened by means of IgG-mixed anti-globulin reaction (MAR) test, to semen quality and post-coital test (PCT) outcome? SUMMARY ANSWER: A 100% positive IgG-MAR test, detected in 2% of the study population, was associated with lower sperm output and progressive motility, and was the sole determinant of higher prevalence of a negative PCT outcome. WHAT IS KNOWN ALREADY: Although ASA may affect sperm fertilizing ability and the IgG-MAR test is recommended by the World Health Organization (WHO) as an integral part of semen analysis for screening the occurrence of ASA, the prevalence and clinical relevance of positive MAR test results remain controversial. STUDY DESIGN, SIZE, DURATION: A retrospective analysis of 12 296 consecutive men who attended a university/hospital andrology clinic for the evaluation of fertility potential was carried out. PARTICIPANTS/MATERIALS, SETTING, METHODS: Immunological screening with the IgG-MAR test was performed on all ejaculates as an integral part of semen analysis. Positive samples (≥10%) were further tested for IgA-ASA. The prevalence of positive IgG-MAR tests results, along with the relationship of the degree of sperm auto-immunization to semen parameters and PCT outcome, were analyzed. MAIN RESULTS AND THE ROLE OF CHANCE: After excluding semen samples showing azoospermia or severe oligo-asthenozoospermia, the prevalence of a positive IgG-MAR test in the remaining 10 025 men was 4%, 3.4% and 2%, with 10%, 50% and 100% thresholds, respectively. The 100%-positive MAR tests exhibited significantly higher consistency over time, and were significantly associated with higher prevalence of a mixed pattern (i.e. when the majority of sperm exhibited beads attached on both the head and along the tail) of positivity as well as with the concomitant occurrence of IgA-ASA. Additionally, the 100%-positive MAR tests were significantly associated with a lower median value of the total number of spermatozoa and progressive motility, compared to samples with a lower degree of positivity or negative samples. In the PCT performed in 120 couples, where ASA were detected in the male partner, the 100%-positive MAR tests were significantly associated with a higher prevalence of negative PCT outcome, in comparison to the lower degree of positivity, independent of, and without any significant contribution from, other determinants (semen and cervical mucus quality). LIMITATIONS, REASONS FOR CAUTION: Only surrogate infertility-related end-points were analyzed in the present study. However, since the impairment of sperm penetration through the cervical mucus represents the primary mechanism of ASA-interference with fertility, PCT outcome may represent a suitable clinical end-point. WIDER IMPLICATIONS OF THE FINDINGS: The present study, being the largest reported to date, provides a reliable estimate of ASA prevalence. Moreover, it indicates that a 50%-positive MAR test, which is suggested by WHO as the clinically-relevant threshold, also includes patients with a degree of sperm auto-immunization that contributes to couple infertility only in the presence of other causal factors; conversely, the 100%-positive MAR test can represent the sole determinant of couple infertility, as it was the sole significant predictor of the highly prevalent negative PCT outcome. STUDY FUNDING/COMPETING INTEREST(S): The study was supported by the University of L'Aquila, Italy. The authors declare no competing interests. TRIAL REGISTRATION NUMBER: N/A.


Assuntos
Autoanticorpos/análise , Autoantígenos/imunologia , Infertilidade Masculina/diagnóstico , Análise do Sêmen/métodos , Espermatozoides/imunologia , Autoanticorpos/imunologia , Coito , Humanos , Infertilidade Masculina/imunologia , Masculino , Estudos Retrospectivos , Sêmen/imunologia
2.
J Evol Biol ; 27(9): 2001-12, 2014 09.
Artigo em Inglês | MEDLINE | ID: mdl-25131432

RESUMO

Titanosauriformes is a conspicuous and diverse group of sauropod dinosaurs that inhabited almost all land masses during Cretaceous times. Besides the diversity of forms, the clade comprises one of the largest land animals found so far, Argentinosaurus, as well as some of the smallest sauropods known to date, Europasaurus and Magyarosaurus. They are therefore good candidates for studies on body size trends such as the Cope's rule, the tendency towards an increase in body size in an evolutionary lineage. We used statistical methods to assess body size changes under both phylogenetic and nonphylogenetic approaches to identify body size trends in Titanosauriformes. Femoral lengths were collected (or estimated from humeral length) from 46 titanosauriform species and used as a proxy for body size. Our findings show that there is no increase or decrease in titanosauriform body size with age along the Cretaceous and that negative changes in body size are more common than positive ones (although not statistically significant) for most of the titanosauriform subclades (e.g. Saltasaridae, Lithostrotia, Titanosauria and Somphospondyli). Therefore, Cope's rule is not supported in titanosauriform evolution. Finally, we also found a trend towards a decrease of titanosauriform mean body size coupled with an increase in body size standard deviation, both supporting an increase in body size variation towards the end of Cretaceous.


Assuntos
Evolução Biológica , Tamanho Corporal , Dinossauros/anatomia & histologia , Animais , Fósseis , Filogenia , Análise de Regressão
3.
Ann Pharm Fr ; 72(6): 440-50, 2014 11.
Artigo em Francês | MEDLINE | ID: mdl-25438655

RESUMO

The medication iatrogenic events are responsible for nearly one iatrogenic event in five. The main purpose of this prospective multicenter study is to determine the effect of pharmaceutical consultations on the occurrence of medication adverse events during hospitalization (MAE). The other objectives are to study the impact of age, of the number of medications and pharmaceutical consultations on the risk of MAE. The pharmaceutical consultation is associated to a complete reassessment done by both a physician and a pharmacist for the home medication, the hospital treatment (3days after admission), the treatment during chemotherapy, and/or, the treatment when the patient goes back home. All MAE are subject to an advice for the patient, additional clinical-biological monitoring and/or prescription changes. Among the 318 patients, 217 (68%) had 1 or more clinically important MAE (89% drug-drug interaction, 8% dosing error, 2% indication error, 1% risk behavior). The patients have had 1121 pharmaceutical consultations (3.2±1.4/patient). Thus, the pharmaceutical consultations divided by 2.34 the risk of MAE (unadjusted incidence ratio, P≤0.05). Each consultation decreased by 24% the risk of MAE. Moreover, adding one medication increases from 14 to 30% as a risk of MAE on the population. Pharmaceutical consultations during the hospital stay could reduce significantly the number of medication adverse effects.


Assuntos
Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/prevenção & controle , Conduta do Tratamento Medicamentoso , Farmacêuticos , Encaminhamento e Consulta , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Feminino , Serviços de Assistência Domiciliar , Hospitalização , Humanos , Doença Iatrogênica/prevenção & controle , Lactente , Masculino , Pessoa de Meia-Idade , Pacientes , Serviço de Farmácia Hospitalar , Médicos , Estudos Prospectivos , Automedicação , Adulto Jovem
4.
Heliyon ; 9(6): e16583, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37260881

RESUMO

A plasma spheroidization treatment was applied to stock stainless steel 316L powder for additive manufacturing. The normal and treated powders were compared both in the powder state as well as in the resulting laser powder bed fusion (L-PBF) builds. The plasma spheroidization process slightly increased treated powder aspect ratio and sphericity and shifted the size distribution to larger diameters relative to the normal powder. The normal powder was austenitic in nature whereas the plasma spheroidization process introduced a small fraction (∼3.5 vol %) of ferrite in the treated powder. Ferrite in the powder was not retained in the printed samples and was not shown to negatively affect the build quality. Porosity areal fraction was generally smaller in the treated powder builds. The normal powder builds had a 6% higher yield strength than treated, however the scatter was significantly larger in the 45° and horizontal orientations compared to the treated powder builds.

5.
Arch Esp Urol ; 64(3): 219-26, 2011 Apr.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-21487172

RESUMO

Approximately 4-14% pelvic fractures cause a posterior urethral injury. Pelvic fractures associated with straddle injuries or large trauma accidents are more frequently involved with this kind of lesions. Primary open repair of the urethral injury is discouraged in the acute setting. 3-6 months after urinary diversion a formal open reconstruction can be safely attempted. This gives time for scar maturation, reabsorption of pelvic hematomas, and relative restoration of anatomical fascial layers. The complexity of such interventions can be minimized following proper diagnostic and surgical protocols. Anastomotic urethroplasty under the precepts of the progressive perineal approach provides an excellent treatment option for these patients. The aim of this paper is the detailed description of the procedure for the treatment of such injuries.


Assuntos
Uretra/lesões , Estreitamento Uretral/cirurgia , Anastomose Cirúrgica/métodos , Fraturas Ósseas/complicações , Humanos , Ossos Pélvicos/lesões , Cuidados Pós-Operatórios , Resultado do Tratamento , Estreitamento Uretral/etiologia
6.
Arch Esp Urol ; 64(3): 207-18, 2011 Apr.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-21487171

RESUMO

Currently, we have different technical options for treating clinically complex scenarios such as neurogenic bladder, difficult to manage lower urinary tract obstruction and many disasters sometimes seen after prostate cancer treatment. During the seventies, clean intermittent bladder catheterization was established as the best treatment option for these patients. As a method, suprapubic urinary diversion has undergone a major evolution over the past fifty years trying to solve the most refractory and poor prognosis cases. Continent ileovesicostomy is an easy emptying and low-pressure non-catheterizable urinary conduit that enables safe and durable urine elimination. In this article a detailed and updated knowledge of this technique is provided.


Assuntos
Complicações Pós-Operatórias/cirurgia , Derivação Urinária/métodos , Doenças Urológicas/cirurgia , Adulto , Cateterismo , Feminino , Humanos , Ileostomia , Laparoscopia , Masculino , Resultado do Tratamento , Obstrução do Colo da Bexiga Urinária/cirurgia , Bexiga Urinaria Neurogênica/cirurgia , Retenção Urinária/etiologia , Retenção Urinária/cirurgia
8.
Hum Reprod ; 24(12): 2979-87, 2009 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-19729379

RESUMO

BACKGROUND: Chemokine receptor CCR5, the main HIV-1 coreceptor, is present in the human spermatozoa. This study aimed to investigate (i) whether the percentage of CCR5-positive spermatozoa varies under conditions associated with changes in the membrane architecture, such as capacitation and fixation/permeabilization procedures; (ii) whether there is any relationship between individual variability in sperm CCR5 expression and semen parameters. METHODS AND RESULTS: In cytometric analysis, the percentage of CCR5-positive unfixed spermatozoa varied from approximately 10 to approximately 60%, and it significantly decreased after 5 h capacitation. The percentage of CCR5-positive spermatozoa was increased to more than 90% following fixation and permeabilization, suggesting the existence of large intracellular pools of the receptor. Immunocytochemistry showed positive staining in the anterior region of the sperm head. In ejaculates from male partner of 102 infertile couples, the CCR5 expression rate significantly correlated with sperm count, total sperm number and forward motility, but not with sperm morphology. In stepwise analysis, only forward motility entered into the model; however, this explained only approximately 8% of the variability in CCR5 expression. Interquartile analysis showed significant differences between the first and fourth quartiles of CCR5 expression for all semen parameters, except morphology. CONCLUSIONS: The percentage of CCR5-positive spermatozoa may vary under conditions associated with changes in membrane architecture and spermatozoa showed large intracellular pools of CCR5. A lower expression of CCR5 in asthenozoospermia seems to be suggested; however, it would only partially contribute to the inter-individual variability in the CCR5 expression. A genetic basis can be hypothesized to explain the variability.


Assuntos
Proteínas de Membrana/metabolismo , Receptores CCR5/metabolismo , Sêmen/citologia , Espermatozoides/metabolismo , Adulto , Astenozoospermia/fisiopatologia , Membrana Celular/química , Membrana Celular/metabolismo , Citometria de Fluxo , Humanos , Imuno-Histoquímica , Infertilidade/fisiopatologia , Masculino , Transporte Proteico , Capacitação Espermática , Contagem de Espermatozoides , Cabeça do Espermatozoide/metabolismo , Motilidade dos Espermatozoides , Espermatozoides/citologia
9.
Ann Biol Clin (Paris) ; 67(6): 651-9, 2009.
Artigo em Francês | MEDLINE | ID: mdl-19939768

RESUMO

Since the disinfecting activity of disinfectants is evaluated by standards, the intrinsic detergent activity is not easily quantifiable and no standard have been suggested yet. Beyond the physicochemical parameters like wettability or foaming presented by the manufacturers, it appears necessary to us to objectively measure the real effect of the detergent agent. The objective of our work is to propose a simple, fast and reproducible method to evaluate detersive activity of the disinfecting detergents. We measured three factors (total amount of extracted bacteria, extraction efficiency and slope of extracting curve) by using Rodac prints technique on two different supports (PVC, stainless steel) that have been contaminated by either E. coli or S. aureus. An increasing mark from 1 to 6 is given to each of these factors in case of statistically differences. The three factors allowed us to calculate a "Specific Index of detersion" (SI) for each germ/support couple (3 to 18). Addition of the marks given to each couple for each disinfecting detergent allowed to calculate a "Globally Index of detersion" (GI) (9 to 72). We tested 4 commercialised disinfecting detergents: Surfanios, Aniosurf, Major C100 and Ecodiol. All detergents may be classified according to their effectiveness on a bacterium/support couple (value of the SI). This enlights a specific spectrum for each disinfecting detergents. As a result, Ecodiol seems to be the most effective deterging agent on 3 of the 4 germ/support couples (S. aureus/PVC, E. coli/PVC and E. coli/stainless steel), whereas Aniosurf is most effective on the S. aureus/stainless steel couple. The GI is very useful to choose the best compromise between activities for all situations. GI rankings of the tested agents were as follows: water < Aniosurf < Surfanios < neutralizing < Major C100 < Ecodiol. This experimental model will be used to test and compare the intrinsic detergent activities of other commercialised products which are usually used for the biocleaning of the medical devices (i.e. endoscopes or reusable dialysis device).


Assuntos
Detergentes/farmacologia , Desinfetantes/farmacologia , Desinfecção/normas , Bactérias/efeitos dos fármacos , Bactérias/isolamento & purificação , Desinfecção/métodos , Escherichia coli/efeitos dos fármacos , Escherichia coli/isolamento & purificação , Testes de Neutralização , Reprodutibilidade dos Testes , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/isolamento & purificação
10.
RSC Adv ; 9(35): 19905-19916, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-35514710

RESUMO

A chemical stability map is advanced by incorporating ion complexation, solubility, and chemical trajectories to predict ZnO, Zn(OH)2, ZnCO3, ZnCl2, Zn5(CO3)2(OH)6, and Zn5(OH)8Cl2·H2O precipitation as a function of the total Zn content and pH of an NaCl solution. These calculations demonstrate equilibrium stability of solid Zn products often not considered while tracking the consumed and produced aqueous Zn ion species concentrations through chemical trajectories. The effect of Cl-based ligand formation is incorporated into these stability predictions, enabling enhanced appreciation for the local corrosion conditions experienced at the Zn surface in chloride-containing environments. Additionally, the complexation of Cl- with Zn2+ is demonstrated to compete with the formation of solid phases, making precipitation more difficult. The present work also extends the chemical stability diagram derivations by incorporating a Gibbs-Thompson curvature relation to predict the effect of nanoscale precipitate phase formation on species solubility. These thermodynamic predictions correlate well with experimental results for Zn corrosion in full and alternate NaCl immersion, and have far-reaching utility in a variety of fields requiring nanoscale, semiconductor, and/or structural materials.

11.
Mini Rev Med Chem ; 8(1): 57-62, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18220985

RESUMO

Most proteins fold into their native structure through well defined pathways which involve a limited number of transient intermediates. Intermediates play a relevant role in the folding process; many diseases of genetic nature are in fact coupled with protein misfolding due to formation of stable, inactive intermediate species of the protein. This review deals with a number of diseases associated with protein misfolding and briefly describes the mechanism(s) responsible, at molecular level, for such pathologies. It is also considered the (native <--> molten globule) transition, recently observed for some proteins, in which a native protein converts into a stable compact intermediate state able to carry out distinct physiological functions inside the cell. A non-native compact form of cyt c, for example, appears to have a role in the programmed cell death (apoptosis) after that the protein is released from the mitochondrion, and non-native forms of the same protein appear involved in some of the disorders attributed to amyloid formation.


Assuntos
Doença de Alzheimer/etiologia , Neoplasias/etiologia , Doença de Parkinson/etiologia , Dobramento de Proteína , Proteínas/química , Proteínas/metabolismo , Humanos , Cinética , Estrutura Secundária de Proteína
12.
J Natl Cancer Inst ; 84(1): 47-51, 1992 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-1738173

RESUMO

Studies suggest that cell proliferation abnormalities of the colorectal mucosa are associated with risk of neoplasia, and most cancers of the large bowel are thought to arise from adenomas. The results of other studies suggest that vitamins A, C, and E have chemopreventive efficacy against colon cancer in animal models. This study evaluates the effect of dietary vitamin supplementation on cell kinetics in uninvolved rectal mucosa in patients with colorectal adenomas. Twenty patients with colorectal adenomas were given vitamins A, C, and E for 6 months after complete polypectomy, and 21 patients with adenomas received placebo. In each patient, six biopsy specimens were taken from normal-appearing rectal mucosa before treatment and after 3 and 6 months of treatment and were incubated with tritiated thymidine ([3H]thymidine), and the [3H]thymidine-labeled cells were counted by use of autoradiography. Two parameters of cell proliferation were evaluated: 1) the ratio of the number of labeled cells to the total number of cells (thymidine labeling index) and 2) the ratio of the number of labeled cells in the upper 40% of the crypt to the total number of labeled cells in the crypt (phi h). The latter index reflects abnormal expansion of the proliferative compartment and is thought to be an intermediate biomarker of cancer risk. In patients receiving vitamins, phi h decreased progressively from baseline values, with increasing statistical significance (P less than .05 after 3 months, P less than .01 after 6 months). There was a statistically significant decrease in the thymidine labeling index in the 40% of the crypt near the mucosal surface, but the variation in the overall labeling index was not statistically significant. In the placebo group, we observed no statistically significant change in cell kinetics. These findings suggest that vitamin A, C, and E supplementation is effective in reducing abnormalities in cell kinetics that may indicate a precancerous condition. Before larger trials on chemoprevention of colorectal adenoma recurrence are conducted, additional studies are needed (a) to validate that cell kinetics is an intermediate biomarker, (b) to determine active agents, optimal dosage, and the relative efficacy of agents given alone and in combination, and (c) to test toxicity.


Assuntos
Adenoma/prevenção & controle , Anticarcinógenos/farmacologia , Neoplasias Colorretais/prevenção & controle , Mucosa Intestinal/efeitos dos fármacos , Vitaminas/farmacologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Ácido Ascórbico/farmacologia , Divisão Celular/efeitos dos fármacos , Feminino , Humanos , Mucosa Intestinal/patologia , Masculino , Pessoa de Meia-Idade , Reto/efeitos dos fármacos , Reto/patologia , Vitamina A/farmacologia , Vitamina E/farmacologia
13.
Biochim Biophys Acta ; 914(2): 185-9, 1987 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-3038191

RESUMO

A circular dichroism study of carboxymethylated cytochrome c has been performed to obtain further information on the structural basis responsible for the observed changes in ligand binding and redox properties of the modified cytochrome c. The results give additional evidence of local structural changes occurring in the heme environment upon rupture of the (Met-80)-heme iron bond in the modified protein. This produces no alterations of the overall molecular conformation, but results in drastic changes in redox potential. In addition, analysis of the reversible conformational transitions induced by urea in the native and the modified proteins supports the idea that the modified derivative can be considered as an 'intermediate state' between the native and the fully unfolded protein.


Assuntos
Grupo dos Citocromos c , Hemeproteínas , Animais , Dicroísmo Circular , Cavalos , Metilação , Miocárdio/metabolismo , Conformação Proteica , Desnaturação Proteica , Ureia
14.
Biochim Biophys Acta ; 789(1): 20-5, 1984 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-6466687

RESUMO

The effect of pH and D-glycerate 2,3-bisphosphate on the oxidation-reduction equilibria of human hemoglobin, normal and modified at the SH(beta 93) groups by reaction with cystine dimethylester has been studied with the aim of comparing the redox equilibria with the oxygen equilibria previously studied under the same experimental conditions. Analysis of data has shown that: (i) the same groups are involved in the oxygenation and oxidation alkaline Bohr effect; (ii) the pK values of these groups are lower in met-hemoglobin than in oxyhemoglobin; (iii) the difference in the affinity for D-glycerate 2,3-bisphosphate of ferric and deoxyhemoglobin is pH-independent in the normal protein, while significantly decreasing with a decrease in pH in the modified protein; (iv) the high cooperativity of the redox process (also occurring at acid pH) and the reduced oxidation Bohr effect observed in the modified protein are consistent with the destabilization of the T structure induced by the bulky reagent bound to the SH(beta 93) groups of the protein.


Assuntos
Cisteína , Ácidos Difosfoglicéricos/farmacologia , Hemoglobinas/metabolismo , 2,3-Difosfoglicerato , Humanos , Concentração de Íons de Hidrogênio , Matemática , Metemoglobina/metabolismo , Oxirredução , Oxiemoglobinas/metabolismo
15.
Biochim Biophys Acta ; 1295(1): 51-8, 1996 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-8679674

RESUMO

The influence of glycerol on the structural properties of Fe(III)-horse heart myoglobin has been investigated by absorbance, CD and SR-SAXS spectroscopy. The results obtained indicate that both the tertiary and the secondary (alpha-helix) conformations of the protein are influenced by glycerol; in particular, an increase of approx. 8% in helical content was observed. Further, analysis of both the acid- and guanidine-induced denaturation transitions points to a glycerol-induced decreased stability of the tertiary structure; conversely, the alpha-helix conformation is found to be stabilized by the organic solvent. Finally, the SR-SAXS data show that gyration radius, cross-section and thickness of the protein increase in the presence of the organic solvent; however, the protein maintains a compact state.


Assuntos
Glicerol/farmacologia , Metamioglobina/química , Solventes/farmacologia , Animais , Dicroísmo Circular , Guanidina , Guanidinas/farmacologia , Cavalos , Concentração de Íons de Hidrogênio , Metamioglobina/efeitos dos fármacos , Miocárdio/química , Desnaturação Proteica , Estrutura Secundária de Proteína/efeitos dos fármacos , Estrutura Terciária de Proteína/efeitos dos fármacos , Espalhamento de Radiação , Análise Espectral/métodos , Raios X
16.
Biochim Biophys Acta ; 1250(2): 183-8, 1995 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-7632723

RESUMO

This paper reports the kinetic and thermodynamic characterization of the complex obtained by binding to microperoxidase (the heme-containing undecapeptide derived from peptic hydrolysis of cytochrome c) a 13 residues synthetic peptide with some propensity to acquire alpha-helical secondary structure (P13). Our results indicate that P13 binds to the sixth coordination position of the Fe(III) of microperoxidase (Keq = 4.8 x 10(4) M-1 at pH 7.0 and 25 degrees C) via the imidazole of His-12, forming a stable complex. The kinetics of complex formation, its secondary structure and its electrochemical activity are reported. This is a first step towards engineering a miniature-heme complex, for a better understanding of the mechanisms governing electron transfer in hemes and heme-proteins, and possibly for novel biotechnological applications.


Assuntos
Peptídeos/química , Peroxidases/química , Sequência de Aminoácidos , Dicroísmo Circular , Eletroquímica , Cinética , Dados de Sequência Molecular , Peptídeos/síntese química , Peptídeos/metabolismo , Peroxidases/metabolismo , Estrutura Secundária de Proteína , Termodinâmica
17.
Biochim Biophys Acta ; 1298(1): 102-8, 1996 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-8948494

RESUMO

This paper reports a voltammetric and spectroscopic investigation of the guanidine-induced unfolding of cytochrome c at neutral pH and 25 degrees C. Electrochemical data provide direct evidence for the presence of an equilibrium intermediate (form I) strictly dependent on the denaturant concentration. The midpoint potential of form I has been determined (E1/2 = +0.010 V vs. NHE) and its structural features defined from analysis of the circular dichroism and absorbance spectroscopy data obtained under the same experimental conditions. From the correlation of electrochemical and spectroscopic data, we propose that the features detected by the intermediate conform to the molten globule state.


Assuntos
Grupo dos Citocromos c/química , Guanidinas/farmacologia , Dobramento de Proteína , Animais , Dicroísmo Circular , Grupo dos Citocromos c/efeitos dos fármacos , Eletroquímica , Transporte de Elétrons , Guanidina , Hemeproteínas/efeitos dos fármacos , Hemeproteínas/metabolismo , Cavalos , Miocárdio/química , Oxirredução , Desnaturação Proteica , Espectrofotometria
18.
Biochim Biophys Acta ; 742(3): 565-7, 1983 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-6301557

RESUMO

Near ultraviolet and visible circular dichroism spectra of the carbomonoxy derivative of the hemoglobin component IV from trout Salmo irideus are pH-dependent in the range 6.2-7.8, and are affected by the presence of inositol hexaphosphate at pH 6.2. On the basis of previous studies, the spectral changes observed can be associated to the pH-dependent R4 leads to T4 transition occurring in the liganded protein. The CD spectra above 500 nm at low pH can be interpreted as due to release of the heme asymmetry in the T liganded conformation, in agreement with the movement of the iron toward the proximal histidine.


Assuntos
Carboxihemoglobina , Hemoglobinas , Regulação Alostérica , Animais , Dicroísmo Circular , Concentração de Íons de Hidrogênio , Conformação Proteica , Prótons , Truta/sangue
19.
Biochim Biophys Acta ; 1034(3): 294-7, 1990 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-2364086

RESUMO

Direct electrochemistry of microperoxidase (the heme-undecapeptide from cytochrome c) has been followed at a bare and a gold plated RVC thin-layer electrode, using the spectropotentiostatic method or voltabsorptometry. Both techniques yield 'clean' and undistorted signals; their analysis easily provides quantitative information for the electrochemical parameters of microperoxidase and shows that spectroelectrochemistry is a powerful method to study the redox behavior of metalloproteins or their active site fragments.


Assuntos
Carbono , Ouro , Peroxidases , Eletroquímica , Eletrodos , Concentração de Íons de Hidrogênio , Oxirredução , Espectrofotometria
20.
Biochim Biophys Acta ; 1162(3): 309-14, 1993 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-8457595

RESUMO

Inositol hexakisphosphate (InsP6) binding to the oxygenated, carbonylated and nitrosylated derivatives of ferrous human hemoglobin (HbO2, HbCO and HbNO, respectively) has been measured at pH 7.0 (0.1 M Bis-Tris buffer, 0.1 M NaCl) and 20 degrees C. The observations indicate the presence of two InsP6 binding sites per tetramer in all the heme liganded hemoglobin derivatives, with different affinities for the polyphosphate. For each binding site, InsP6 interacts with similar affinity constants to HbO2, HbCO and HbNO. Such a finding indicates that different heme ligands do not alter significantly the stereochemistry of the polyphosphate binding cleft. This behaviour seems to indicate that, even though different heme ligands are likely to affect the tertiary conformation of the subunit in a different fashion, the perturbation does not seem to be transmitted to the quaternary arrangement of the whole macromolecule, and, thus, to the InsP6 binding site.


Assuntos
Carboxihemoglobina/metabolismo , Hemoglobinas Glicadas/metabolismo , Óxido Nítrico/metabolismo , Oxiemoglobinas/metabolismo , Ácido Fítico/metabolismo , Sítios de Ligação , Carboxihemoglobina/química , Dicroísmo Circular , Hemoglobinas Glicadas/química , Humanos , Cinética , Ligantes , Óxido Nítrico/química , Oxiemoglobinas/química , Análise Espectral
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