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1.
Eur J Radiol Open ; 8: 100356, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34041308

RESUMO

[This corrects the article DOI: 10.1016/j.ejro.2020.100280.].

2.
Eur J Radiol Open ; 7: 100280, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33102639

RESUMO

PURPOSE: To investigate contrast dynamics and artifacts associated with different breathing maneuvers during pulmonary computed tomography angiography (pCTA) in a prospective randomized clinical trial. METHOD: Three different breathing maneuvers (inspiration, expiration, Mueller) were randomly assigned to 146 patients receiving pCTA for suspected pulmonary embolism (PE). Contrast enhancement of central and peripheral arteries and imaging quality of lung parenchyma were compared and analyzed. Results were compared by using the analysis of variances (ANOVA) and Kruskal-Wallis-Test. RESULTS: Mean enhancement in the pulmonary trunk was highest during breath-hold in inspiration (293 HU, range 195-460 HU) compared to Mueller (259 HU, range 136-429 HU, p = 0022) and expiration (267 HU, range 115-376 HU). This was similar for the right pulmonary artery (inspiration 289 HU, range 173-454 HU; Mueller 250 HU, range 119-378 HU; p = 0.007; expiration 257 HU, range 114-366 HU; p = 0.032) and left pulmonary artery (inspiration 280.3 HU, range 170-462 HU; Mueller 245 HU, range 111-371 HU; p = 0.016; expiration 252 HU, range 110-371 HU).Delineation of peripheral arteries was significantly better in inspiration vs Mueller (p = 0.006) and expiration (p = 0.049). Assessment of the lung parenchyma was significantly better in inspiration vs Mueller (p = 0.013) or expiration (p < 0.001). CONCLUSIONS: Resting inspiratory position achieved the highest enhancement levels in central and peripheral pulmonary arteries and best image quality of the pulmonary parenchyma in comparison to other breathing maneuvers. It is necessary to train the maneuver prior to the examination in order to avoid deep inspiration with the risk of suboptimal opacification of the pulmonary arteries.

3.
Artigo em Francês | MEDLINE | ID: mdl-29468863

RESUMO

Benzodiazepine hypnotics bear a higher risk of high dose dependence than benzodiazepine anxiolytics, according to a recent study in Luxemburg. This article summarizes the main indications of these molecules and the current treatment recommendations. It provides an overview of public health actions of the past and the future to reduce their excessive consumption.


Assuntos
Ansiedade/tratamento farmacológico , Benzodiazepinas/uso terapêutico , Distúrbios do Início e da Manutenção do Sono/tratamento farmacológico , Humanos , Guias de Prática Clínica como Assunto
4.
Br J Cancer ; 109(3): 610-4, 2013 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-23921280

RESUMO

BACKGROUND: Gamma-glutamyltransferase (GGT) - a membrane-bound enzyme crucially involved in the cell's detoxification pathway and apoptotic balance - is involved in tumour development, progression and chemotherapy resistance. Elevated GGT serum levels are associated with increased cancer risk in women and worse prognosis in gynaecologic cancers. The present study investigated the prognostic role of GGT in ovarian cancer patients. METHODS: In this multicenter study, pre-therapeutic GGT levels were ascertained in 634 consecutive patients with epithelial ovarian cancer (EOC, n=567) and borderline tumour of the ovary (BTO, n=67). Gamma-glutamyltransferase serum levels were associated with clinicopathological parameters and uni- and multivariate survival analyses were performed. Immunohistochemistry of GGT was performed in ovarian cancer tissue and correlated with GGT serum levels. RESULTS: Pre-therapeutic GGT serum levels were higher in patients with EOC (28.56 (38.24) U l(-1)) than in patients with BTO (20.01 (12.78) U l(-1), P=0.01). High GGT serum levels were associated with advanced FIGO stage (P<0.001) and with worse overall survival in univariate (P<0.001) and multivariable analysis (P=0.02, HR 1.2 (1.1-1.5)). We further investigated the association between systemic GGT serum levels and local GGT expression in EOC tumour tissue and observed an association between these two parameters (P=0.03). CONCLUSION: High pre-therapeutic GGT serum levels are associated with advanced tumour stage and serve as an independent prognostic marker for worse overall survival in patients with EOC. Gamma-glutamyltransferase expression in ovarian cancer tissue is reflected in GGT serum levels.


Assuntos
Neoplasias Epiteliais e Glandulares/enzimologia , Neoplasias Ovarianas/enzimologia , gama-Glutamiltransferase/sangue , Carcinoma Epitelial do Ovário , Feminino , Humanos , Imuno-Histoquímica , Estimativa de Kaplan-Meier , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Neoplasias Epiteliais e Glandulares/patologia , Neoplasias Ovarianas/patologia , Prognóstico , Índice de Gravidade de Doença
5.
J Chem Phys ; 124(13): 134903, 2006 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-16613473

RESUMO

Cycloolefin copolymers of ethylene and norbornene, with norbornene content in the range from 36 to 62 mol %, were studied with respect to the thermal, thermodynamic, and rheological properties using differential scanning calorimetry, pressure-volume-temperature, and dynamic mechanical measurements. All copolymers obey the principle of time-temperature superposition, i.e., they can be considered as thermorheologically simple except for a temperature range in the vicinity of T(g). Despite this, the results on (i) the ratio of activation energies E(V)(*)/H(*) used to quantify the origin of the liquid-to-glass transition, (ii) the pressure coefficient of the glass temperature T(g)(P), and (iii) the dynamic fragility m suggest increasing dynamic heterogeneity with increasing norbornene content that is driven by the structural heterogeneity along the backbone.

6.
Depress Anxiety ; 10(3): 89-98, 1999.
Artigo em Inglês | MEDLINE | ID: mdl-10604081

RESUMO

UNLABELLED: To evaluate the effects of maintenance treatment and durability of gains after treatment discontinuation, responders to either phenelzine (PZ) or cognitive-behavioral group therapy (CBGT) from an acute trial comparing these two treatments as well as pill placebo and a psychotherapy control (educational supportive group therapy) were enrolled into maintenance and treatment-free follow-up phases. EXPERIMENTAL DESIGN: Responders to an acute trial contrasting PZ and CBGT entered a six-month maintenance phase. Patients who continued to respond through the maintenance phase entered a six-month treatment free phase. Patients receiving pill placebo or educational supportive group therapy in the acute trial did not enter the long term study. PRINCIPAL OBSERVATIONS: PZ patients entered maintenance more improved than CBGT patients, and nonrelapsing PZ patients maintained their superior gains throughout the study. Relapse during maintenance did not differ between treatments. However, PZ patients showed a trend toward greater relapse during treatment-free follow-up. There was a greater relapse among patients with generalized social phobia with phenelzine. CONCLUSIONS: PZ and cognitive-behavioral group therapy may differ in their long term effects. The superiority seen with PZ on some measures in the acute study persisted in patients who maintained their gains over the course of maintenance and treatment-free follow-up. However, CBGT may lead to a greater likelihood of maintaining response after treatment has terminated. Replication with larger samples is needed, as is a study of the acute and long-term efficacy of combined PZ and CBGT.


Assuntos
Terapia Cognitivo-Comportamental , Inibidores da Monoaminoxidase/uso terapêutico , Fenelzina/uso terapêutico , Transtornos Fóbicos/terapia , Psicoterapia de Grupo , Adulto , Análise de Variância , Distribuição de Qui-Quadrado , Fatores de Confusão Epidemiológicos , Feminino , Seguimentos , Humanos , Masculino , Pacientes Desistentes do Tratamento , Transtornos Fóbicos/tratamento farmacológico , Prognóstico , Recidiva
7.
J Pers ; 67(2): 373-406, 1999 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10202808

RESUMO

Sociotropy (an aspect of interpersonal dependence) and sociability (affiliative need) were examined as moderator variables of the relationship between shyness and interpersonal concerns in two studies. In Study 1, sociotropy, but not sociability, predicted unique variance in three indices of interpersonal concerns through both direct and interactive relations with shyness. An initial analysis in Study 2 showed that sociotropy, but not sociability, was predictive of participants' perceived competence in situations that involved initiation of conversations and assertion. In the second part of Study 2, sociotropy accounted for significant increments in variance when predicting cognitive and affective manifestations of distress related to simulated conversation and assertion situations, while sociability did not. Study 2 results suggest that sociotropy operates primarily in an additive manner with shyness in predicting interpersonal concerns, rather than moderating the relation between shyness and interpersonal concerns. Differences in the results of the two studies and implications for future research are discussed.


Assuntos
Relações Interpessoais , Timidez , Adolescente , Adulto , Cognição , Dependência Psicológica , Feminino , Humanos , Solidão/psicologia , Estudos Prospectivos
8.
Arch Gen Psychiatry ; 55(12): 1133-41, 1998 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9862558

RESUMO

BACKGROUND: This article presents results of the acute treatment phase of a 2-site study comparing cognitive behavioral group therapy (CBGT) and treatment with the monoamine oxidase inhibitor phenelzine sulfate for social phobia. METHODS: One hundred thirty-three patients from 2 sites received 12 weeks of CBGT, phenelzine therapy, pill placebo administration, or educational-supportive group therapy (an attention-placebo treatment of equal credibility to CBGT). The "allegiance effect," ie, the tendency for treatments to seem most efficacious in settings of similar theoretical orientation and less efficacious in theoretically divergent settings, was also examined by comparing responses to the treatment conditions at both sites: 1 known for pharmacological treatment of anxiety disorders and the other for cognitive behavioral treatment. RESULTS: After 12 weeks, phenelzine therapy and CBGT led to superior response rates and greater change on dimensional measures than did either control condition. However, response to phenelzine therapy was more evident after 6 weeks, and phenelzine therapy was also superior to CBGT after 12 weeks on some measures. There were few differences between sites, suggesting that these treatments can be efficacious at facilities with differing theoretical allegiances. CONCLUSIONS: After 12 weeks, both phenelzine therapy and CBGT were associated with marked positive response. Although phenelzine therapy was superior to CBGT on some measures, both were more efficacious than the control conditions. More extended cognitive behavioral treatment and the combination of modalities may enhance treatment effect.


Assuntos
Terapia Cognitivo-Comportamental , Fenelzina/uso terapêutico , Transtornos Fóbicos/terapia , Psicoterapia de Grupo , Adulto , Análise de Variância , Animais , Terapia Combinada , Feminino , Seguimentos , Cobaias , Humanos , Masculino , Pessoa de Meia-Idade , Inventário de Personalidade , Transtornos Fóbicos/tratamento farmacológico , Transtornos Fóbicos/psicologia , Placebos , Escalas de Graduação Psiquiátrica/estatística & dados numéricos , Resultado do Tratamento
9.
Artigo em Francês | MEDLINE | ID: mdl-9534267

RESUMO

The European Union has a formal interest in public health under the Article 129 of the Maastricht Treaty. Hitherto, the main contribution of the European Union action in public health has been limited to research, health information and education concerning, in particular major diseases and drug dependence. Unfortunately the European architects did not clearly conceive a plan for the establishment of a common health policy despite the fact that the European health policies are fragmented and are often the indirect results of economic policies. Indeed, the domain of public health is essentially governed by the principle of national sovereignty, onto which the principle of subsidiarity has been grafted. Whereas Article 129 of the Maastricht Treaty applies especially to preventive health policies, the concomitant affirmation of the principle of subsidiarity in this field tends to suspend any establishment of a European health policy. In the same way, the lack of compulsory provisions relating to Community actions, expressed as recommendations, raises the question whether the European Union is willing to move to a European health policy.


Assuntos
União Europeia/organização & administração , Política de Saúde , Saúde Pública , Europa (Continente) , Humanos , Medicina Preventiva/normas , Garantia da Qualidade dos Cuidados de Saúde
10.
Biopolymers ; 36(2): 109-20, 1995 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-7492740

RESUMO

CD and nmr spectroscopy were used to compare the conformational properties of two related peptides. One of the peptides, Model AB, was designed to adopt a helix-turn-extended strand (alpha beta) tertiary structure in water that might be stabilized by hydrophobic interactions between two leucine residues in the amino-terminal segment and two methionine residues in the carboxyl terminal segment. The other peptide, AB Helix, has the same amino acid sequence as Model AB except that it lacks the -Pro-Met-Thr-Met-Thr-Gly segment at the carboxyl-terminus. Although the carboxyl-terminal segment of Model AB was found to be unstructured, its presence increases the number of residues in a helical conformation, shifts the pKas of three ionizable side chains by 1 pH unit or more compared to an unstructured peptide, stabilizes the peptide as a monomer in high concentrations of ammonium sulfate, increases the conformational stability of residues at the terminal ends of the helix, and results in many slowly exchanging amide protons throughout the entire backbone of the peptide. These results suggest that interactions between adjacent segments in a small peptide can have significant structure organizing effects. Similar kinds of interactions may be important in determining the structure of early intermediates in protein folding and may be useful in the de novo design of independently folding peptides.


Assuntos
Peptídeos/química , Conformação Proteica , Sequência de Aminoácidos , Dicroísmo Circular , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Dados de Sequência Molecular , Peso Molecular , Peptídeos/síntese química , Estrutura Terciária de Proteína
11.
Behav Res Ther ; 33(6): 637-50, 1995 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-7654156

RESUMO

The efficacy of Heimberg's (1991) Cognitive-Behavioral Group Therapy (CBGT) [Unpublished manuscript] for social phobia has been demonstrated in several studies in recent years. However, little is known about the mechanisms underlying the treatment's success. In order to determine whether the cognitive restructuring component of CBGT is essential, this study compared CBGT to an exposure-based treatment without formal cognitive restructuring. A wait-list control was also included. In general, Ss in the active treatment conditions improved and control Ss did not improve on a variety of self-report, clinician, and behavioral measures. Limited evidence indicated that Ss in the non-cognitive treatment may have made somewhat greater gains on some measures. Although CBGT Ss reported more improvement than exposure-alone Ss in subjective anxiety during an individualized behavioral test at posttreatment, this difference disappeared at 6-month follow-up. Surprisingly, CBGT was less effective than in previous controlled trials, and possible reasons for this are discussed. Implications of the results for cognitive theory and cognitive-behavioral therapy for social phobia are addressed.


Assuntos
Terapia Cognitivo-Comportamental/métodos , Transtornos Fóbicos/terapia , Psicoterapia de Grupo/métodos , Adolescente , Adulto , Nível de Alerta , Dessensibilização Psicológica/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Determinação da Personalidade , Transtornos Fóbicos/psicologia , Resultado do Tratamento
12.
J Pers ; 63(1): 47-63, 1995 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-7722850

RESUMO

Shy people are characterized as engaging in self-derogatory thinking leading to anxiousness and inhibition, while people who are publicly self-conscious are focused on the impression they create on others. In addition, public self-consciousness has been described as an antecedent of shyness. In the present research, we tested additive versus interactive hypotheses about the association of shyness and public self-consciousness with dysfunctional social interaction. Undergraduate men varying in shyness and public self-consciousness engaged in a conversation with an unfamiliar woman confederate. Following the conversation, subjects completed self-report measures focusing on their responses during the conversation. Only main effects for shyness and public self-consciousness were found, supporting an additive hypothesis. Shyness was related to all dependent variables reflecting a negative self-bias, while public self-consciousness was not. In particular, shyness was inversely related to the balance of subjects' positive and negative thoughts and to reported use of protective as well as avoidance of acquisitive self-presentation responses. Public self-consciousness was positively related to use of protective self-presentation responses but unrelated to acquisitive responses.


Assuntos
Relações Interpessoais , Autoimagem , Timidez , Adulto , Ansiedade/psicologia , Atenção , Feminino , Identidade de Gênero , Humanos , Masculino , Determinação da Personalidade
13.
Urol Int ; 55(3): 158-61, 1995.
Artigo em Inglês | MEDLINE | ID: mdl-8540162

RESUMO

We report a case of primary renal osteosarcoma diagnosed during the patient's life. A review of the literature revealed only 10 cases of primary osteogenic renal sarcoma. Differential diagnoses and possible treatment are discussed.


Assuntos
Neoplasias Renais , Osteossarcoma , Idoso , Idoso de 80 Anos ou mais , Diagnóstico Diferencial , Feminino , Humanos , Neoplasias Renais/diagnóstico , Neoplasias Renais/patologia , Neoplasias Renais/terapia , Masculino , Pessoa de Meia-Idade , Osteossarcoma/diagnóstico , Osteossarcoma/patologia , Osteossarcoma/terapia
14.
Anxiety ; 1(2): 80-9, 1994.
Artigo em Inglês | MEDLINE | ID: mdl-9160552

RESUMO

Emotionally distant and controlling child-rearing attitudes have been reported to characterize the parents of American or western European social phobics in previous research. However, the notion that these parental attitudes may be associated with social anxiety only in some cultures has not been investigated. The present study examined social anxiety among American social phobics and American and Chinese/Chinese American volunteer samples and how it may relate to their parents' child-rearing attitudes. Multivariate analyses of variance revealed overall group differences. Both volunteer samples reported lower levels of anxiety than social phobics. Parents of Chinese/Chinese Americans and social phobics were reported to be similar in their (1) isolation of children from social activities; (2) over-emphasis of others' opinions; and (3) use of shame tactics for discipline (more so than American volunteers' parents). However, parents of nonsocial phobics were more likely to attend family social activities than social phobics' parents. Overall, the association between a reported parenting style emphasizing others' opinions and shame tactics and social anxiety in their adult children was more evident in both American samples than among Chinese/Chinese Americans.


Assuntos
Asiático/psicologia , Atitude , Comparação Transcultural , Poder Familiar/psicologia , Transtornos Fóbicos/psicologia , Adulto , Feminino , Humanos , Controle Interno-Externo , Masculino , Pessoa de Meia-Idade , Inventário de Personalidade , Transtornos Fóbicos/diagnóstico , Vergonha , Percepção Social , Socialização
15.
Dent Mater ; 9(5): 312-6, 1993 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-7995483

RESUMO

A new technique using standardized test facings was designed to evaluate interdental plaque accumulation on different restoration materials. In 10 volunteers, a total of 40 samples, including enamel, two different ceramics and a bonding composite, were inserted one by one into a precision attachment in an experimental inlay bordering on either the lower second premolar or the lower first molar. Bacterial accumulation on each approximal specimen was allowed to mature for 3 d. Following microbiological processing of the plaque samples, total bacterial counts, colony forming units and the bacterial vitality were determined. The results revealed different accumulation rate patterns. Both ceramics accumulated less plaque with a reduced vitality compared to enamel, while the bonding composite showed no significant differences compared to the natural tooth substance. No significant differences were detected when comparing the two examined ceramics.


Assuntos
Biofilmes , Bis-Fenol A-Glicidil Metacrilato , Placa Dentária/microbiologia , Porcelana Dentária , Adulto , Bactérias Anaeróbias/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Restauração Dentária Permanente , Feminino , Humanos , Masculino , Estatísticas não Paramétricas
16.
Biochemistry ; 32(18): 4881-94, 1993 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-8387821

RESUMO

Nuclear magnetic resonance and circular dichroism (CD) studies of isolated peptides corresponding to WT and mutant OmpA signal sequences are reported; all of the peptides adopt substantial amounts of alpha-helical structure both in 1:1 (v/v) trifluoroethanol (TFE)/water and in sodium dodecyl sulfate (SDS) micelles. In TFE/water, the helix begins after the positively charged N-terminal residues and is most stable in the hydrophobic core, which correlates with results obtained previously for other signal sequences. The helix is weaker between the hydrophobic core and the C-terminus; such a break in the helix appears to be common to other signal peptides studied previously and could be of functional importance. No clear correlation could be established between the helicity of the peptides in TFE/water and their in vivo activities. All the peptides have a higher alpha-helix content in SDS than in TFE/water, and there is a good correlation between helix content in SDS and in vivo activity. Helicity in SDS for the functional peptides increases both at the N-terminus and in the hydrophobic core, and is driven by a strong association of the core with the hydrophobic chains of the detergent. The extension of the helix toward the N-terminus may be a result of neutralization of the N-terminal positive charges by the headgroups of the micelles, which removes unfavorable electrostatic interactions with the helix dipole. All these comparisons were facilitated by the use of upfield shifts of H alpha protons in helical regions relative to random coil chemical shifts, which also yielded estimates of helical content that correlated well with the CD results.


Assuntos
Proteínas da Membrana Bacteriana Externa/química , Escherichia coli/química , Conformação Proteica , Sinais Direcionadores de Proteínas/química , Amidas/química , Sequência de Aminoácidos , Dicroísmo Circular , Análise Mutacional de DNA , Deutério , Espectroscopia de Ressonância Magnética , Micelas , Dados de Sequência Molecular , Estrutura Secundária de Proteína , Prótons , Dodecilsulfato de Sódio/química , Trifluoretanol/química , Água/química
17.
Biopolymers ; 32(12): 1741-54, 1992 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-1472656

RESUMO

In an effort to explore the influence of interfacial environments on reverse turns, we have performed a detailed analysis by nmr of the solution conformations of two cyclic pentapeptides in sodium dodecyl sulfate (SDS) micelles. The first peptide, cyclo (D-Phe1-Pro2-Gly3-D-Ala4-Pro5), adopts a single rigid conformation in solution (either chloroform or dimethylsulfoxide) and in crystals, whereas the second, cyclo (Gly1-Pro2-D-Phe3-Gly4-Val5), is much more flexible and adopts different conformations in the crystal and in solution. Both of these peptides are solubilized by SDS micelles, and nmr relaxation rates indicate that they are both partially immobilized by interaction with the micelles. Furthermore, some amide protons in both peptides participate in hydrogen bonds with water. In the presence of micelles, the former peptide retains a conformation essentially the same as that found in crystals and in solution, which consists of a beta turn and an inverse gamma turn. However, the micellar environment has a significant effect on the latter peptide. In particular, the population of a conformer containing a cis Gly-Pro peptide bond is increased significantly. The most likely conformation of the cis isomer, determined by a combination of nmr and restrained molecular dynamics, contains a Gly1-Pro2 delta turn and a gamma turn about D-Phe3. The nmr data on the trans isomer indicate that this isomer is averaging between two conformations that differ mainly in the orientation of the D-Phe3-Gly4 peptide bond.


Assuntos
Peptídeos Cíclicos/química , Sequência de Aminoácidos , Espectroscopia de Ressonância Magnética , Micelas , Dados de Sequência Molecular , Conformação Proteica , Estrutura Secundária de Proteína , Termodinâmica
18.
Biochim Biophys Acta ; 1159(1): 81-93, 1992 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-1390913

RESUMO

Previous studies on mitochondrial targeting presequences have indicated that formation of an amphiphillic helix may be required for efficient targeting of the precursor protein into mitochondria, but the structural details are not well understood. We have used CD and NMR spectroscopy to characterize in detail the structure of a synthetic peptide corresponding to the presequence for the beta-subunit of F1-ATPase, a mitochondrial matrix protein. Although this peptide is essentially unstructured in water, alpha-helix formation is induced when the peptide is placed in structure-promoting environments, such as SDS micelles or aqueous trifluoroethanol (TFE). In 50% TFE (by volume), the peptide is in dynamic equilibrium between random coil and alpha-helical conformations, with a significant population of alpha-helix throughout the entire peptide. The helix is somewhat more stable in the N-terminal part of the presequence (residues 4-10), and this result is consistent with the structure proposed previously for the presequence of another mitochondrial matrix protein, yeast cytochrome oxidase subunit IV. Addition of increasing amounts of TFE causes the alpha-helical content to increase even further, and the TFE titration data for the presequence peptide of the F1-ATPase beta-subunit are not consistent with a single, cooperative transition from random coil to alpha-helix. There is evidence that helix formation is initiated in two different regions of the peptide. This result helps to explain the redundancy of the targeting information contained in the presequence for the F1-ATPase beta-subunit.


Assuntos
ATPases Translocadoras de Prótons/química , Sequência de Aminoácidos , Transporte Biológico , Dicroísmo Circular , Ligação de Hidrogênio , Espectroscopia de Ressonância Magnética , Mitocôndrias/metabolismo , Dados de Sequência Molecular , Peptídeos/química , Precursores de Proteínas/química , Estrutura Secundária de Proteína
19.
Eur J Biochem ; 205(1): 233-40, 1992 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-1555584

RESUMO

Reversible binding of calcium ions to a single high-affinity binding site in the 40-kDa basement membrane protein (BM-40) caused a 33% increase of alpha-helicity, an about 60% change in intrinsic fluorescence and a dramatic increase of the rate of cleavage by alpha-chymotrypsin. All these effects exhibited identical dependencies on calcium concentration from which a dissociation constant Kd = 0.6 microM was determined. Calcium release was accompanied by an increase of the frictional ratio in solution but not by denaturation which occurred at about equal guanidine.HCl concentration for both calcium-saturated and calcium-depleted protein (midpoint 1.5 M). The cleavage sites for alpha-chymotrypsin are located in or near to the EF-hand domain IV of calcium-depleted BM-40 (also known as SPARC, i.e. secreted protein acidic and rich in cysteine, and osteonectin). These and other data indicate that binding occurs in the EF-hand domain from which a large conformational change is transmitted. Low-affinity calcium-binding sites in the N-terminal glutamic-acid-rich domain I of BM-40 were identified by human leukocyte elastase which was found to cleave very specifically in the middle of this domain. From the increase of cleavage rate with increasing calcium concentration a Kd greater than or equal to 10 mM was estimated. It is suggested that variations of calcium levels in the extracellular space in this range may regulate functions of BM-40 such as collagen binding and that high-affinity binding is important for stabilization, folding and secretion during biosynthesis.


Assuntos
Cálcio/metabolismo , Osteonectina/metabolismo , Sequência de Aminoácidos , Compostos de Anilina , Animais , Cátions Bivalentes , Quimotripsina/metabolismo , Dicroísmo Circular , Eletroforese em Gel de Poliacrilamida , Hidrólise , Cinética , Elastase de Leucócito , Camundongos , Microscopia Eletrônica , Dados de Sequência Molecular , Osteonectina/ultraestrutura , Elastase Pancreática/metabolismo , Conformação Proteica , Espectrometria de Fluorescência , Especificidade por Substrato , Ultracentrifugação , Xantenos
20.
Proteins ; 10(2): 130-9, 1991.
Artigo em Inglês | MEDLINE | ID: mdl-1896426

RESUMO

Recently, Presta and Rose proposed that a necessary condition for helix formation is the presence of residues at the N- and C-termini (called NTBs and CTBs) whose side chains can form hydrogen bonds with the initial four amides and the last four carbonyls of the helix, which otherwise lack intrahelical hydrogen bonding partners. We have tested this hypothesis by conformational analysis by circular dichroism (CD) of a synthetic peptide corresponding to a region (171-188) of the protein carboxypeptidase A; in the protein, residues 174 to 186 are helical and are flanked by NTBs and CTBs. Since helix formation in this peptide may also be stabilized by electrostatic interactions, we have compared the helical content of the native peptide with that of several modified peptides designed to enable dissection of different contributions to helix stability. As expected, helix dipole interactions appear to contribute substantially, but we conclude that hydrogen bonding interactions as proposed by Presta and Rose also stabilize helix formation. To assist in comparison of different peptides, we have introduced two concentration-independent CD parameters which are sensitive probes of helix formation.


Assuntos
Carboxipeptidases/química , Ligação de Hidrogênio , Peptídeos/química , Sequência de Aminoácidos , Carboxipeptidases A , Dicroísmo Circular , Estabilidade Enzimática , Concentração de Íons de Hidrogênio , Dados de Sequência Molecular , Conformação Proteica , Trifluoretanol
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