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1.
Scott Med J ; 57(1): 60, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-22408219

RESUMO

Patients with physical problems related to the use of alcohol or drugs often present to general hospitals in an unplanned, emergency fashion. In 2005, the Kerr report concluded that fundamental changes were needed in our approach, shifting the emphasis from a reactive to a more proactive, prevention-based model in the treatment of acute medical conditions. We studied patients who had at least one alcohol- or drug-related emergency admission, whose most recent admission was to Aberdeen Royal Infirmary and who, using the Scottish Patients at Risk of Re-admission and Admission (SPARRA) All Ages Tool, were thought to be at high risk of further emergency admission. We examined data sets derived from the National Health Service National Services Scotland Information Services Division, a Liaison Psychiatry database, data from the local psychiatric Patient Information Management System and data collected by the hospital alcohol liaison nurse to examine this group of patients further and consider the scope for any future intervention. Patients who have an alcohol- or drug-related emergency admission to the general hospital are at increased risk of re-admission. A substantial proportion of these patients has come into contact with the psychiatric services, often attracting a substance misuse and/or personality disorder diagnosis. A significant proportion also presents in the context of self-harm. In conclusion, this group of frequent hospital attenders may be difficult to engage but may benefit from more proactive intervention, a more joined-up management approach and the development of an enhanced general hospital alcohol liaison service.


Assuntos
Hospitais Gerais , Transtornos Mentais/epidemiologia , Readmissão do Paciente , Comportamento Autodestrutivo/epidemiologia , Transtornos Relacionados ao Uso de Substâncias/epidemiologia , Adolescente , Adulto , Idoso , Feminino , Hospitalização/estatística & dados numéricos , Humanos , Masculino , Pessoa de Meia-Idade , Readmissão do Paciente/estatística & dados numéricos , Medição de Risco , Fatores de Risco , Escócia/epidemiologia , Adulto Jovem
2.
J Neurol Neurosurg Psychiatry ; 82(7): 810-3, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21257981

RESUMO

OBJECTIVES: To determine the disability, distress and employment status of new neurology outpatients with physical symptoms unexplained by organic disease and to compare them with patients with symptoms explained by organic disease. METHODS: As part of a cohort study (the Scottish Neurological Symptoms Study) neurologists rated the extent to which each new patient's symptoms were explained by organic disease. Patients whose symptoms were rated as 'not at all' or only 'somewhat' explained by disease were considered cases, and those whose symptoms were 'largely' or 'completely' explained by disease were considered controls. All patients completed self-ratings of disability, health status (Medical Outcomes Study Short Form 12-Item Scale (SF-12)) and emotional distress (Hospital Anxiety and Depression Scale) and also reported their employment and state financial benefit status. RESULTS: 3781 patients were recruited: 1144 (30%) cases and 2637 (70%) controls. Cases had worse physical health status (SF-12 score 42 vs 44; difference in means 1.7 (95% CI -2.5 to 0.9)) and worse mental health status (SF-12 score 43 vs 47; difference in means -3.5 (95% CI -4.3 to to 2.7)). Unemployment was similar in cases and controls (50% vs 50%) but cases were more likely not to be working for health reasons (54% vs 37% of the 50% not working; OR 2.0 (95% CI 1.6 to 2.4)) and also more likely to be receiving disability-related state financial benefits (27% vs 22%; (OR 1.3, 95% CI 1.1 to 1.6)). CONCLUSIONS: New neurology patients with symptoms unexplained by organic disease have more disability-, distress- and disability-related state financial benefits than patients with symptoms explained by disease.


Assuntos
Doenças do Sistema Nervoso/psicologia , Desemprego/estatística & dados numéricos , Adulto , Ansiedade/etiologia , Ansiedade/psicologia , Estudos de Coortes , Transtorno Depressivo/etiologia , Transtorno Depressivo/psicologia , Avaliação da Deficiência , Pessoas com Deficiência , Feminino , Nível de Saúde , Humanos , Masculino , Saúde Mental , Pessoa de Meia-Idade , Doenças do Sistema Nervoso/epidemiologia , Pacientes Ambulatoriais , Estudos Prospectivos , Escócia/epidemiologia , Seguridade Social , Estresse Psicológico/psicologia , Resultado do Tratamento
3.
Psychol Med ; 40(4): 689-98, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19627646

RESUMO

BACKGROUND: Patients whose symptoms are 'unexplained by disease' often have a poor symptomatic outcome after specialist consultation, but we know little about which patient factors predict this. We therefore aimed to determine predictors of poor subjective outcome for new neurology out-patients with symptoms unexplained by disease 1 year after the initial consultation. METHOD: The Scottish Neurological Symptom Study was a 1-year prospective cohort study of patients referred to secondary care National Health Service neurology clinics in Scotland (UK). Patients were included if the neurologist rated their symptoms as 'not at all' or only 'somewhat explained' by organic disease. Patient-rated change in health was rated on a five-point Clinical Global Improvement (CGI) scale ('much better' to 'much worse') 1 year later. RESULTS: The 12-month outcome data were available on 716 of 1144 patients (63%). Poor outcome on the CGI ('unchanged', 'worse' or 'much worse') was reported by 482 (67%) out of 716 patients. The only strong independent baseline predictors were patients' beliefs [expectation of non-recovery (odds ratio [OR] 2.04, 95% confidence interval [CI] 1.40-2.96), non-attribution of symptoms to psychological factors (OR 2.22, 95% CI 1.51-3.26)] and the receipt of illness-related financial benefits (OR 2.30, 95% CI 1.37-3.86). Together, these factors predicted 13% of the variance in outcome. CONCLUSIONS: Of the patients, two-thirds had a poor outcome at 1 year. Illness beliefs and financial benefits are more useful in predicting poor outcome than the number of symptoms, disability and distress.


Assuntos
Atitude Frente a Saúde , Doenças do Sistema Nervoso Central/diagnóstico , Doenças do Sistema Nervoso Central/terapia , Cultura , Adulto , Doenças do Sistema Nervoso Central/epidemiologia , Estudos de Coortes , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Valor Preditivo dos Testes , Estudos Prospectivos , Índice de Gravidade de Doença , Fatores Socioeconômicos , Fatores de Tempo , Resultado do Tratamento , Adulto Jovem
4.
Brain ; 132(Pt 10): 2878-88, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-19737842

RESUMO

It has been previously reported that a substantial proportion of newly referred neurology out-patients have symptoms that are considered by the assessing neurologist as unexplained by 'organic disease'. There has however been much controversy about how often such patients subsequently develop a disease diagnosis that, with hindsight, would have explained the symptoms. We aimed to determine in a large sample of new neurology out-patients: (i) what proportion are assessed as having symptoms unexplained by disease and the diagnoses given to them; and (ii) how often a neurological disorder emerged which, with hindsight, explained the original symptoms. We carried out a prospective cohort study of patients referred from primary care to National Health Service neurology clinics in Scotland, UK. Measures were: (i) the proportion of patients with symptoms rated by the assessing neurologist as 'not at all' or only 'somewhat explained' by 'organic disease' and the neurological diagnoses recorded at initial assessment; and (ii) the frequency of unexpected new diagnoses made over the following 18 months (according to the primary-care physician). One thousand four hundred and forty-four patients (30% of all new patients) were rated as having symptoms 'not at all' or only 'somewhat explained' by 'organic disease'. The most common categories of diagnosis were: (i) organic neurological disease but with symptoms unexplained by it (26%); (ii) headache disorders (26%); and (iii) conversion symptoms (motor, sensory or non-epileptic attacks) (18%). At follow-up only 4 out of 1030 patients (0.4%) had acquired an organic disease diagnosis that was unexpected at initial assessment and plausibly the cause of the patients' original symptoms. Eight patients had died at follow-up; five of whom had initial diagnoses of non-epileptic attacks. Seven other types of diagnostic change with very different implications to a 'missed diagnosis' were found and a new classification of diagnostic revision is presented. One-third of new neurology out-patients are assessed as having symptoms 'unexplained by organic disease'. A new diagnosis, which with hindsight explained the original symptoms, rarely became apparent to the patient's primary care doctor in the 18 months following the initial hospital consultation.


Assuntos
Doenças do Sistema Nervoso/diagnóstico , Adulto , Transtorno Conversivo/diagnóstico , Transtorno Conversivo/fisiopatologia , Erros de Diagnóstico , Feminino , Seguimentos , Cefaleia/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Doenças do Sistema Nervoso/complicações , Doenças do Sistema Nervoso/etiologia , Exame Neurológico , Pacientes Ambulatoriais , Seleção de Pacientes , Prognóstico , Resultado do Tratamento
5.
J Mol Biol ; 259(5): 947-56, 1996 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-8683597

RESUMO

Time-resolved linear dichroism (TRLD) measurements are conducted on gels of sickle cell hemoglobin following laser photolysis of the carbonyl adduct to monitor religation kinetics to hemoglobin S polymers. The return of the polymer phase to its equilibrium ligation state has been found to be about 1000 times slower than that of the solution phase hemoglobin tetramers. Several mechanisms describing this slow religation to the polymer were proposed: (1) religation occurs through a biomolecular process involving all polymer hemes, (2) religation occurs through a bimolecular process in which only hemoglobin molecules at the polymer ends can participate, and (3) religation occurs through the exchange of ligated hemoglobin molecules in the monomer phase with unligated ones in the polymer phase. To test these mechanisms, measurements are performed on gels having different domain sizes. The results show no relation between domain size and religation kinetics. The independence of religation kinetics and domain size is most consistent with the first of the three mechanisms described above (bimolecular recombination involving all polymer hemes). This result is discussed in terms of a model in which diffusion of the ligand is inhibited in the polymer phase. An understanding of the ligand binding kinetics of sickle hemoglobin polymers could have pathophysiological significance in its relevance to polymer formation and melting during red blood cell circulation.


Assuntos
Hemoglobina Falciforme/química , Monóxido de Carbono/química , Humanos , Lasers , Fotólise , Polímeros , Análise Espectral
6.
Addiction ; 92(3): 313-24, 1997 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9219393

RESUMO

Results of previous studies suggest that end-of-treatment self-efficacy in problem drinkers has limited predictive validity. One explanation for this finding has been the postulated existence of a ceiling effect, i.e. the possibility that subjects who rate themselves highly in terms of self-efficacy form a heterogeneous group with some subjects making inflated self-efficacy judgements based on an over-optimistic perception of their coping abilities. In the present study, end-of-treatment self-efficacy in 63 problem drinkers, as measured by the Situational Confidence Questionnaire and a newly designed Self-Efficacy Questionnaire (SEQ), was predictive of abstinence status at 3 month follow-up. In those patients who on the SEQ had expressed great confidence in their ability to remain abstinent over the follow-up period, the additional consideration of keyworkers' confidence in their patients' ability to remain abstinent as well as patients' anticipated need for future help improved the prediction of abstinence status. These results are discussed with respect to the postulated ceiling effect. A prognostic tree using just three baseline variables predicted abstinence status correctly in 88% of all cases.


Assuntos
Alcoolismo/psicologia , Autocuidado/psicologia , Autoimagem , Inquéritos e Questionários , Temperança/psicologia , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes
7.
Photochem Photobiol ; 56(6): 953-8, 1992 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-1492138

RESUMO

Nanosecond excited state absorption spectra of all-trans-1,4-diphenyl-1,3-butadiene (DPB) and a rigid s-cis DPB analog, 1,4-diphenyl-1,3-cyclopentadiene, were obtained in several hydrocarbon solvents at room temperature and low temperatures. Analysis of the excited state absorption spectra of these two molecules suggests the presence of excited state s-cis rotamers in DPB at room temperature.


Assuntos
Butadienos/química , Butadienos/efeitos da radiação , Fotoquímica , Solventes , Espectrofotometria , Estereoisomerismo , Temperatura
8.
J Psychosom Res ; 43(6): 575-93, 1997 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9430071

RESUMO

Denial is a concept often encountered in literature describing patients' psychological responses to physical illness. Definitions and theories of denial have drawn on clinical, cognitive, psychodynamic, organic, and interpersonal frameworks. Denial is related to other concepts such as lack of insight, self-deception, and anosognosia. Empirical studies have yielded mixed results with regard to the adaptive properties of denial. These results require interpretation in the light of: (1) the definitional complexities of denial; (2) the diversity of methods used for its assessment; and (3) the choice of different clinical samples and heterogeneous outcome measures. The clinical management of maladaptive denial poses a challenging problem which requires consideration of factors pertaining to the patient, the illness, the treating clinician, as well as the patient's social environment. To achieve further clarification of the role of denial in physical illness, future research would benefit from clearer definitions and more refined, consistent methods of assessment. A number of recommendations are outlined.


Assuntos
Negação em Psicologia , Doença/psicologia , Adaptação Psicológica , Humanos
9.
J Neurol ; 259(1): 33-8, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21674198

RESUMO

Many patients with a diagnosis of neurological disease, such as multiple sclerosis, have symptoms or disability that is considered to be in excess of what would be expected from that disease. We aimed to describe the overall and relative frequency of symptoms 'unexplained by organic disease' in patients attending general neurology clinics with a range of neurological disease diagnoses. Newly referred outpatients attending neurology clinics in all the NHS neurological centres in Scotland, UK were recruited over a period of 15 months. The assessing neurologists recorded their initial neurological diagnoses and also the degree to which they considered the patient's symptoms to be explained by organic disease. Patients completed self report scales for both physical and psychological symptoms. The frequency of symptoms unexplained by organic disease was determined for each category of neurological disease diagnoses. 3,781 patients participated (91% of those eligible). 2,467 patients had a diagnosis of a neurological disease (excluding headache disorders). 293 patients (12%) of these patients were rated as having symptoms only "somewhat" or "not at all" explained by that disease. These patients self-reported more physical and more psychological symptoms than those with more explained symptoms. No category of neurological disease was more likely than the others to be associated with such symptoms although patients with epilepsy had fewer. A substantial proportion of new outpatients with diagnoses of neurological disease also have symptoms regarded by the assessing neurologist as being unexplained by that disease; no single neurological disease category was more likely than others to be associated with this phenomenon.


Assuntos
Doenças do Sistema Nervoso/etiologia , Adulto , Idoso , Ansiedade/etiologia , Transtorno Conversivo/epidemiologia , Depressão/etiologia , Emoções , Epilepsia/complicações , Epilepsia/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doenças do Sistema Nervoso/diagnóstico , Doenças do Sistema Nervoso/psicologia , Exame Neurológico , Dor/etiologia , Escócia/epidemiologia , Transtornos Somatoformes/epidemiologia
10.
Clin Neurol Neurosurg ; 112(9): 747-51, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20646830

RESUMO

OBJECTIVE: Information on the nature and relative frequency of diagnoses made in referrals to neurology outpatient clinics is an important guide to priorities in services, teaching and research. Previous studies of this topic have been limited by being of only single centres or lacking in detail. We aimed to describe the neurological diagnoses made in a large series of referrals to neurology outpatient clinics. METHOD: Newly referred outpatients attending neurology clinics in all the NHS neurological centres in Scotland, UK were recruited over a period of 15 months. The assessing neurologists recorded the initial diagnosis they made. An additional rating of the degree to which the neurologist considered the patient's symptoms to be explained by disease was used to categorise those diagnoses that simply described a symptom such as 'fatigue'. RESULTS: Three thousand seven hundred and eighty-one patients participated (91% of those eligible). The commonest categories of diagnosis made were: headache (19%), functional and psychological symptoms (16%), epilepsy (14%), peripheral nerve disorders (11%), miscellaneous neurological disorders (10%), demyelination (7%), spinal disorders (6%), Parkinson's disease/movement disorders (6%), and syncope (4%). Detailed breakdowns of each category are provided. CONCLUSIONS: Headache, functional/psychological disorders and epilepsy are the most common diagnoses in new patient referral to neurological services. This information should be used to shape priorities for services, teaching and research.


Assuntos
Doenças do Sistema Nervoso/epidemiologia , Doenças do Sistema Nervoso/terapia , Neurologia , Encaminhamento e Consulta/estatística & dados numéricos , Adulto , Fatores Etários , Idoso , Estudos de Coortes , Epilepsia/diagnóstico , Epilepsia/tratamento farmacológico , Epilepsia/epidemiologia , Feminino , Geografia , Transtornos da Cefaleia/diagnóstico , Transtornos da Cefaleia/epidemiologia , Transtornos da Cefaleia/terapia , Humanos , Masculino , Transtornos Mentais/diagnóstico , Transtornos Mentais/epidemiologia , Transtornos Mentais/terapia , Pessoa de Meia-Idade , Doenças do Sistema Nervoso/diagnóstico , Exame Neurológico , Seleção de Pacientes , Estudos Prospectivos , Escócia/epidemiologia , Fatores Sexuais , Medicina Estatal/estatística & dados numéricos
12.
Biophys J ; 81(5): 2919-34, 2001 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-11606302

RESUMO

The influence of solvation on the rate of quaternary structural change is investigated in human hemoglobin, an allosteric protein in which reduced water activity destabilizes the R state relative to T. Nanosecond absorption spectroscopy of the heme Soret band was used to monitor protein relaxation after photodissociation of aqueous HbCO complex under osmotic stress induced by the nonbinding cosolute poly(ethylene glycol) (PEG). Photolysis data were analyzed globally for six exponential time constants and amplitudes as a function of osmotic stress and viscosity. Increases in time constants associated with geminate rebinding, tertiary relaxation, and quaternary relaxation were observed in the presence of PEG, along with a decrease in the fraction of hemes rebinding CO with the slow rate constant characteristic of the T state. An analysis of these results along with those obtained by others for small cosolutes showed that both osmotic stress and solvent viscosity are important determinants of the microscopic R --> T rate constant. The size and direction of the osmotic stress effect suggests that at least nine additional water molecules are required to solvate the allosteric transition state relative to the R-state hydration, implying that the transition state has a greater solvent-exposed area than either end state.


Assuntos
Monóxido de Carbono/metabolismo , Hemoglobinas/metabolismo , Modelos Biológicos , Polietilenoglicóis/farmacologia , Água/metabolismo , Regulação Alostérica/efeitos dos fármacos , Regulação Alostérica/fisiologia , Sítios de Ligação/efeitos dos fármacos , Sítios de Ligação/fisiologia , Hemoglobinas/efeitos dos fármacos , Humanos , Cinética , Pressão Osmótica , Fotólise/efeitos dos fármacos , Conformação Proteica/efeitos dos fármacos , Estrutura Quaternária de Proteína/efeitos dos fármacos , Estrutura Quaternária de Proteína/fisiologia , Estrutura Terciária de Proteína/efeitos dos fármacos , Estrutura Terciária de Proteína/fisiologia , Água/farmacologia
13.
Biopolymers ; 57(1): 29-36, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10679637

RESUMO

Protein unfolding during guanidine HCl denaturant titration of the reduced and oxidized forms of cytochrome c is monitored with magnetic circular dichroism (MCD), natural CD, and absorption of the heme bands and far-UV CD of the amide bands. Direct MCD spectral evidence is presented for bis-histidinyl heme ligation in the unfolded states of both the reduced and oxidized protein. For both redox states, the unfolding midpoints measured with MCD, which is an indicator of tertiary structure, are significantly lower than those measured with far-UV CD, an indicator of secondary structure. The disparate titration curves are interpreted in terms of a compound mechanism for denaturant-induced folding and unfolding involving a molten globulelike intermediate state (MG) with near-native secondary structure and nonnative tertiary structure and heme ligation. A comparison of the dependence of the free energy of formation of the MG intermediate on the redox state with the known contributions from heme ligation and solvation suggests that the heme is significantly more accessible to solvent in the MG intermediate than it is in the native state.


Assuntos
Grupo dos Citocromos c/química , Grupo dos Citocromos c/metabolismo , Animais , Dicroísmo Circular , Heme/metabolismo , Cavalos , Cinética , Oxirredução , Desnaturação Proteica , Dobramento de Proteína , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Espectrofotometria
14.
Artigo em Inglês | MEDLINE | ID: mdl-9241422

RESUMO

Over the past two decades, nanosecond absorption and vibrational spectroscopies have developed into powerful tools for monitoring the secondary, tertiary, and quaternary structural relaxations of biological macromolecules under near-physiological conditions of solvent and temperature. Observed through such methods, the dynamic response of a biomolecule to photoinitiated excursions from equilibrium can reveal valuable information about the structure-function relationship, information beyond that obtained from the static structures provided by X-ray crystallography, nuclear magnetic resonance spectroscopy, and other steady-state methods. Most recently, the development of ultra-sensitive polarization techniques for absorption spectroscopy has greatly enhanced the amount of time-resolved structural information that can be obtained from the broadened electronic spectra of biomolecules. This review examines nanosecond absorption, vibrational, and polarized absorption methods, and their applications to protein function and folding, emphasizing the complementary nature of information obtained from electronic and vibrational spectra measured on the nanosecond time scale.


Assuntos
Proteínas/química , Análise Espectral/métodos , Hemeproteínas/química , Humanos , Dobramento de Proteína , Fatores de Tempo
15.
Biophys J ; 60(1): 125-34, 1991 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-1653049

RESUMO

Nanosecond time-resolved magnetic circular dichroism (TRMCD) and time-resolved natural circular dichroism (TRCD) measurements of photolysis products of the CO complex of eukaryotic cytochrome c oxidase (CcO-CO) are presented. TRMCD spectra obtained at 100 ns and 10 microseconds after photolysis are diagnostic of pentacoordinate cytochrome a3Fe2+, as would be expected for simple photodissociation. Other time-resolved spectroscopies (UV-visible and resonance Raman), however, show evidence for unusual Fea3(2+) coordination after CO photolysis (Woodruff, W. H., O. Einarsdóttir, R. B. Dyer, K. A. Bagley, G. Palmer, S. J. Atherton, R. A. Goldbeck, T. D. Dawes, and D. S. Kliger. 1991. Proc. Nat. Acad. Sci. U.S.A. 88:2588-2592). Furthermore, time-resolved IR experiments have shown that photodissociated CO binds to CuB+ prior to recombining with Fea3(2+) (Dyer, R. B., O. Einarsdóttir, P. M. Killough, J. J. López-Garriga, and W. H. Woodruff. 1989. J. Am. Chem. Soc. 111:7657-7659). A model of the CcO-CO photolysis cycle which is consistent with all of the spectroscopic results is presented. A novel feature of this model is the coordination of a ligand endogenous to the protein to the Fe axial site vacated by the photolyzed CO and the simultaneous breaking of the Fe-imidazole(histidine) bond.


Assuntos
Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Sítios de Ligação , Birrefringência , Monóxido de Carbono/metabolismo , Dicroísmo Circular , Complexo IV da Cadeia de Transporte de Elétrons/efeitos da radiação , Cinética , Magnetismo , Fotólise , Conformação Proteica , Fatores de Tempo
16.
Biochem Biophys Res Commun ; 235(3): 610-4, 1997 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-9207206

RESUMO

In order to study interdimer heme-heme electronic interactions in human hemoglobin, the Soret circular dichroism spectrum of the carboxy adduct is measured as a function of protein concentration, the spectrum at the highest concentration representing primarily that of alpha2beta2 tetramers (93%) and the lowest concentration representing primarily alphabeta dimers (68%). The tetramer-dimer difference spectrum, obtained using singular value decomposition and linear least squares fitting from a matrix of CD spectra measured at ten concentrations, is roughly conservative, with a larger negative lobe at shorter wavelengths and a peak-to-trough magnitude that is 18% of the tetramer's maximum Soret CD magnitude. It is tentatively assigned to heme-heme excitonic interactions on the basis of theoretical predictions by R. W. Woody [(1985) in Optical Properties and Structure of Tetrapyrroles (Blauer, G., and Sund, H., Eds.), pp. 239-256, Walter de Gruyter, New York].


Assuntos
Heme/química , Hemoglobinas/química , Conformação Proteica , Carboxihemoglobina/química , Dicroísmo Circular , Dimerização , Humanos , Substâncias Macromoleculares , Espectrofotometria
17.
Proc Natl Acad Sci U S A ; 96(6): 2782-7, 1999 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-10077588

RESUMO

The funnel landscape model predicts that protein folding proceeds through multiple kinetic pathways. Experimental evidence is presented for more than one such pathway in the folding dynamics of a globular protein, cytochrome c. After photodissociation of CO from the partially denatured ferrous protein, fast time-resolved CD spectroscopy shows a submillisecond folding process that is complete in approximately 10(-6) s, concomitant with heme binding of a methionine residue. Kinetic modeling of time-resolved magnetic circular dichroism data further provides strong evidence that a 50-microseconds heme-histidine binding process proceeds in parallel with the faster pathway, implying that Met and His binding occur in different conformational ensembles of the protein, i.e., along respective ultrafast (microseconds) and fast (milliseconds) folding pathways. This kinetic heterogeneity appears to be intrinsic to the diffusional nature of early folding dynamics on the energy landscape, as opposed to the late-time heterogeneity associated with nonnative heme ligation and proline isomers in cytochrome c.


Assuntos
Dobramento de Proteína , Proteínas/química , Animais , Humanos , Cinética , Modelos Moleculares
18.
Biochemistry ; 37(50): 17527-36, 1998 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-9860868

RESUMO

Nanosecond time-resolved absorption and magnetic optical rotatory dispersion (MORD) measurements of photolyzed myoglobin-CO visible bands (500-650 nm) are presented. These measurements reveal a 400 ns process, spectrally distinct from ligand recombination, that accounts for 7% of the observed spectral evolution in the visible absorption bands and 4% in the MORD. The time-resolved MORD, more sensitive to heme coordination geometry than absorption, suggests that this process is most likely associated with protein relaxation on the distal side of the heme pocket, perhaps accompanying rehydration of the deoxymyoglobin photoproduct or accommodation of protein side chains to ligand escape.


Assuntos
Mioglobina/química , Fotólise , Animais , Dicroísmo Circular , Cavalos , Cinética , Ligantes , Magnetismo , Modelos Moleculares , Mioglobina/análogos & derivados , Dispersão Óptica Rotatória/métodos
19.
Arch Biochem Biophys ; 392(2): 233-44, 2001 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-11488597

RESUMO

We directly measured the absolute reactivity of 17-beta-estradiol (E2) and several phenolic model compounds for E2 toward t-butoxy radical (t-BuO*) by nanosecond time-resolved optical spectroscopy. Compared to other phenols, E2 is a moderate, but not strong deactivator of oxyradicals. The absolute bimolecular rate constant for H-atom transfer from E2 to t-BuO* is 1.3 +/- 0.3 x 10(9) M(-1) x s(-1) (23 degrees C, benzene). We estimate the O-H bond strength of 17-beta-estradiol to be approximately 85 +/- 2 kcal/mol and calculate the reaction rate constant of E2 toward peroxy radical to be 10(5) M(-1) x s(-1) at 37 degrees C. The conjugate phenoxy radical of 17-beta-estradiol, E2O*, is unusually reactive toward alpha-tocopherol and ascorbate by H-atom transfer in homogeneous solution (10(8)-10(9) M(-1) x s(-1)). Our findings suggest that E2 functions in vivo as a highly localized, synergistic biological antioxidant. This may partly explain the clinical effectiveness of ovarian steroids in delaying the manifestations of Alzheimer's Disease as well as in protecting against cardiovascular pathologies. In the absence of complementary antioxidant synergists, E2O* is expected to be a pro-oxidant.


Assuntos
Antioxidantes/farmacologia , Estradiol/química , Estradiol/farmacologia , Sequestradores de Radicais Livres/farmacologia , Doença de Alzheimer/metabolismo , Ácido Ascórbico/química , Relação Dose-Resposta a Droga , Cinética , Modelos Químicos , Fenol/química , Espectrofotometria , Vitamina E/química
20.
Biophys J ; 71(3): 1596-604, 1996 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-8874033

RESUMO

The time-resolved spectra of photoproducts from ligand photodissociation of oxyhemoglobin are measured in the Soret spectral region for times from 10 ns to 320 microseconds after laser photolysis. Four processes are detected at a heme concentration of 80 microM: a 38-ns geminate recombination, a 137-ns tertiary relaxation, and two bimolecular processes for rebinding of molecular oxygen. The pseudo-first-order rate constants for rebinding to the alpha and beta subunits of hemoglobin are 3.2 x 10(4) s-1 (31 microseconds lifetime) and 9.4 x 10(4) s-1 (11 microseconds lifetime), respectively. The significance of kinetic measurements made at different heme concentrations is discussed in terms of the equilibrium compositions of hemoglobin tetramer and dimer mixtures. The rebinding rate constants for alpha and beta chains are observed to be about two times slower in the dimer than in the tetramer, a finding that appears to support the observation of quaternary enhancement in equilibrium ligand binding by hemoglobin tetramers.


Assuntos
Oxiemoglobinas/química , Oxiemoglobinas/efeitos da radiação , Sítios de Ligação , Fenômenos Biofísicos , Biofísica , Heme/química , Humanos , Técnicas In Vitro , Cinética , Ligantes , Oxigênio/química , Fotoquímica , Fotólise , Conformação Proteica , Estrutura Terciária de Proteína , Espectrofotometria/instrumentação , Espectrofotometria/métodos
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