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CDKL5 deficiency disorder (CDD) is a rare developmental and epileptic encephalopathy. Ganaxolone, a neuroactive steroid, reduces the frequency of major motor seizures in children with CDD. This analysis explored the effect of ganaxolone on non-seizure outcomes. Children (2-19 years) with genetically confirmed CDD and ≥ 16 major motor seizures per month were enrolled in a double-blind randomized placebo-controlled trial. Ganaxolone or placebo was administered three times daily for 17 weeks. Behaviour was measured with the Anxiety, Depression and Mood Scale (ADAMS), daytime sleepiness with the Child Health Sleep Questionnaire, and quality of life with the Quality of Life Inventory-Disability (QI-Disability) scale. Scores were compared using ANOVA, adjusted for age, sex, number of anti-seizure mediations, baseline 28-day major motor seizure frequency, baseline developmental skills, and behaviour, sleep or quality of life scores. 101 children with CDD (39 clinical sites, 8 countries) were randomized. Median (IQR) age was 6 (3-10) years, 79.2 % were female, and 50 received ganaxolone. After 17 weeks of treatment, Manic/Hyperactive scores (mean difference 1.27, 95%CI -2.38,-0.16) and Compulsive Behaviour scores (mean difference 0.58, 95%CI -1.14,-0.01) were lower (improved) in the ganaxolone group compared with the placebo group. Daytime sleepiness scores were similar between groups. The total change in QOL score for children in the ganaxolone group was 2.6 points (95%CI -1.74,7.02) higher (improved) than in the placebo group but without statistical significance. Along with better seizure control, children who received ganaxolone had improved behavioural scores in select domains compared to placebo.
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Calidad de Vida , Humanos , Femenino , Masculino , Método Doble Ciego , Niño , Preescolar , Adolescente , Adulto Joven , Resultado del Tratamiento , Síndromes Epilépticos/tratamiento farmacológico , Convulsiones/tratamiento farmacológico , Convulsiones/etiología , Pregnanolona/análogos & derivados , Espasmos InfantilesRESUMEN
PURPOSE: Validated measures capable of demonstrating meaningful interventional change in the CDKL5 deficiency disorder (CDD) are lacking. The study objective was to modify the Rett Syndrome Gross Motor Scale (RSGMS) and evaluate its psychometric properties for individuals with CDD. METHODS: Item and scoring categories of the RSGMS were modified. Caregivers registered with the International CDKL5 Clinical Research Network uploaded motor videos filmed at home to a protected server and completed a feedback questionnaire (n = 70). Rasch (n = 137), known groups (n = 109), and intra- and inter-rater reliability analyses (n = 50) were conducted. RESULTS: The age of individuals with CDD ranged from 1.5 to 34.1 years. The modified scale, Gross Motor-Complex Disability (GM-CD), comprised 17 items. There were no floor or ceiling effects and inter- and intra-rater reliability were good. Rasch analysis demonstrated that the items encompassed a large range of performance difficulty, although there was some item redundancy and some disordered categories. One item, Prone Head Position, was a poor fit. Caregiver-reported acceptability was positive. Scores differed by age and functional abilities. SUMMARY: GM-CD appears to be a suitable remotely administered measure and psychometrically sound for individuals with CDD. This study provides the foundation to propose the use of GM-CD in CDD clinical trials. Longitudinal evaluation is planned.
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Síndromes Epilépticos , Síndrome de Rett , Espasmos Infantiles , Humanos , Lactante , Preescolar , Niño , Adolescente , Adulto Joven , Adulto , Psicometría , Destreza Motora , Reproducibilidad de los Resultados , Síndrome de Rett/diagnóstico , Síndrome de Rett/genética , Proteínas Serina-Treonina Quinasas/genéticaRESUMEN
BACKGROUND: Comparative data collection in transborder areas can contribute to informed decision making processes when dealing with borderless health threats such as pandemics, and thus help minimize the negative health effects for its citizens. To examine the pandemic response over time and the impact of infectious disease control in a cross-border setting, a prospective longitudinal study was conducted in the border area between Germany, Belgium and the Netherlands. In the spring of 2021, a random sample of 26,925 adult citizens selected from governmental registries was invited to collect a blood sample at home for SARS-CoV-2 antibody testing and to fill in an online questionnaire on attitudes and behaviour towards infection prevention measures, cross-border mobility, social network and support, COVID-19 self-reported infection(s) and symptoms, vaccination, general self-reported health and socio-demographics. In autumn 2021, participants were invited for a follow-up round. An online tool was developed to coordinate fieldwork procedures, real-time monitoring of participation and consultation of antibody test results. Furthermore, a helpdesk in all three languages for participants' support was set up. RESULTS: In the first round, 6,006 citizens in the Meuse-Rhine Euroregion participated. 15.3% of the invited citizens on the Belgian side of the border participated. In the Netherlands and Germany this was respectively 27% and 23.7%. In the follow-up round 4,286 (71.4%) citizens participated for the second time. The participation rate was highest in the age group 50-69 years and lowest in > 80 in all sub regions of the Meuse-Rhine Euroregion. More women participated than men. Overall, more blood samples were returned than completed questionnaires. In total, 3,344 citizens in the Meuse-Rhine Euroregion completed all components of participation in both rounds. CONCLUSIONS: The collection of comparative data can help better assess the pandemic response and the impact of infectious disease control in a cross-border area. Recommendations for a longitudinal cross-border study include a centralized online environment, mapping out potential challenges related to national regulations in the preparation phase and organizing regional coordination centres to create more familiarity and trust towards the involved organisations.
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BACKGROUND: Based on successive Health Interview Surveys (HIS), it has been demonstrated that also in Belgium obesity, measured by means of a self-reported body mass index (BMI in kg/m2), is a growing public health problem that needs to be monitored as accurately as possible. Studies have shown that a self-reported BMI can be biased. Consequently, if the aim is to rely on a self-reported BMI, adjustment is recommended. Data on measured and self-reported BMI, derived from the Belgian Food Consumption Survey (FCS) 2014 offers the opportunity to do so. METHODS: The HIS and FCS are cross-sectional surveys based on representative population samples. This study focused on adults aged 18-64 years (sample HIS = 6545 and FCS = 1213). Measured and self-reported BMI collected in FCS were used to assess possible misreporting. Using FCS data, correction factors (measured BMI/self-reported BMI) were calculated in function of a combination of background variables (region, gender, educational level and age group). Individual self-reported BMI of the HIS 2013 were then multiplied with the corresponding correction factors to produce a corrected BMI-classification. RESULTS: When compared with the measured BMI, the self-reported BMI in the FCS was underestimated (mean 0.97 kg/m2). 28% of the obese people underestimated their BMI. After applying the correction factors, the prevalence of obesity based on HIS data significantly increased (from 13% based on the original HIS data to 17% based on the corrected HIS data) and approximated the measured one derived from the FCS data. CONCLUSIONS: Since self-reported calculations of BMI are underestimated, it is recommended to adjust them to obtain accurate estimates which are important for decision making.
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The use of bispecific antibodies (BsAbs) to treat human diseases is on the rise. Increasingly complex and powerful therapeutic mechanisms made possible by BsAbs are spurring innovation of novel BsAb formats and methods for their production. The long-lived in vivo pharmacokinetics, optimal biophysical properties and potential effector functions of natural IgG monoclonal (and monospecific) antibodies has resulted in a push to generate fully IgG BsAb formats with the same quaternary structure as monoclonal IgGs. The production of fully IgG BsAbs is challenging because of the highly heterogeneous pairing of heavy chains (HCs) and light chains (LCs) when produced in mammalian cells with two IgG HCs and two LCs. A solution to the HC heterodimerization aspect of IgG BsAb production was first discovered two decades ago; however, addressing the LC mispairing issue has remained intractable until recently. Here, we use computational and rational engineering to develop novel designs to the HC/LC pairing issue, and particularly for κ LCs. Crystal structures of these designs highlight the interactions that provide HC/LC specificity. We produce and characterize multiple fully IgG BsAbs using these novel designs. We demonstrate the importance of specificity engineering in both the variable and constant domains to achieve robust HC/LC specificity within all the BsAbs. These solutions facilitate the production of fully IgG BsAbs for clinical use.
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Anticuerpos Biespecíficos/química , Biología Computacional/métodos , Cadenas Pesadas de Inmunoglobulina/química , Cadenas kappa de Inmunoglobulina/química , Ingeniería de Proteínas/métodos , Animales , Anticuerpos Biespecíficos/genética , Anticuerpos Biespecíficos/metabolismo , Células CHO , Cricetinae , Cricetulus , Células HEK293 , Humanos , Cadenas Pesadas de Inmunoglobulina/genética , Cadenas Pesadas de Inmunoglobulina/metabolismo , Cadenas kappa de Inmunoglobulina/genética , Cadenas kappa de Inmunoglobulina/metabolismo , Modelos Moleculares , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Programas InformáticosRESUMEN
PURPOSE: In the majority of studies on determinants of use of anxiolytics and antidepressants a substantially higher consumption is observed among women than among men. We investigated gender differences in the association between the use of anxiolytics and antidepressants and mental health and explored if there are indications of gender differences in inappropriate use of these medicines. METHODS: Data were from the 2004 Belgian Health Interview Survey, a nationally representative sample of the Belgian population. The analysis was restricted to the population of 15 years and older (n = 11,220). The probability of use of anxiolytics and antidepressants was assessed through logistic regression models by gender and through models including the interaction between gender and mental health. RESULTS: The association between the use of antidepressants and mental health did not vary substantially between men and women. Among men the use of anxiolytics showed a strong association with sleeping problems, but not with depressive disorders. Among women the use of anxiolytics was significantly associated with the three mental health conditions that were investigated: depressive disorder, anxiety, and sleeping problems. CONCLUSIONS: The link between mental health and use of anxiolytics differs by gender. Some indications exist for gender differences in inappropriate use of anxiolytics, whereas this does not hold true for the use of antidepressants. Further efforts are needed to increase the awareness of prescribers, policy makers, and the general public on the appropriate use of anxiolytics, especially among women and in the older population.
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Ansiolíticos/administración & dosificación , Antidepresivos/administración & dosificación , Revisión de la Utilización de Medicamentos , Salud Mental , Vigilancia de la Población , Caracteres Sexuales , Adolescente , Adulto , Anciano , Bélgica , Femenino , Humanos , Modelos Logísticos , Masculino , Salud Mental/estadística & datos numéricos , Persona de Mediana Edad , Adulto JovenRESUMEN
PURPOSE: This study aimed to examine the 12-month and lifetime prevalence rates of pure and comorbid mental disorders (mood, anxiety and alcohol disorders) in Belgian home-dwelling elderly. METHODS: A representative random sample of 665 non-instutionalized older adults (60+) from Belgium was interviewed in 2000 and 2001. DSM-IV disorders were assessed by interviewers trained to use a revised version of the World Mental Health Composite International Diagnostic Interview (WMH-CIDI) of the World Health Organization. RESULTS: Twenty percent of the respondents reported a lifetime history of at least one mental disorder; 5% met criteria for a a mental disorder in the past twelve months. Mood and anxiety disorders were the most common mental disorders. Almost 5% of the respondents reported suicidal ideation in their lifetime, while 0.22% had suicidal ideation in the past twelve months preceding the interview. CONCLUSIONS: Mental disorders are not uncommon in the Belgian home-dwelling elderly. The results of this study imply that in 2000-2001 at least five percent of the older adults living in the community had at least one mental disorder. Two in thousand older adults reported suicidal ideations in the 12 months preceding the interview.
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Evaluación Geriátrica , Trastornos Mentales/epidemiología , Suicidio/psicología , Anciano , Anciano de 80 o más Años , Alcoholismo/epidemiología , Ansiedad/epidemiología , Bélgica/epidemiología , Femenino , Encuestas Epidemiológicas , Humanos , Entrevistas como Asunto , Masculino , Salud Mental , Persona de Mediana Edad , Trastornos del Humor/epidemiología , Prevalencia , Suicidio/estadística & datos numéricos , Intento de Suicidio/psicología , Intento de Suicidio/estadística & datos numéricosRESUMEN
OBJECTIVE: To assess psychotropic drug utilization in the general population of Belgium, and the pattern of use in individuals with mental disorders. METHOD: A representative random sample of non-institutionalized inhabitants from Belgium aged 18 or older (n = 2419) were interviewed between April 2001 and June 2002. Individuals were asked about any psychotropic drug use in the past 12 months, even if they used the drug(s) just once. The interview took place by means of the World Mental Health Composite International Diagnostic Interview (WMH-CIDI). RESULTS: Slightly more than 19% reported that they had used any psychotropic drug in the past 12 months; 11% had a 12-month mental disorder. The extent of psychotropic drug utilization varied according to the nature of the disorders: 60% in mood disorders, 53% in alcohol disorders, and 39% in anxiety disorders. Thirty nine percent of the respondents with a mood disorder consumed an antidepressant drug in the past year; 23% of the respondents with an anxiety disorder consumed an anxiolytic drug in the past 12 months. Among those who reported that they used antidepressants, selective serotonin reuptake inhibitors were most commonly consumed (SSRI). CONCLUSION: These data do not provide evidence for any over-consumption of psychopharmacological agents in Belgium. By contrast, they question the appropriateness of pharmacological treatments, in which under-treatment seems to be coupled with a high use of non-specific medications.
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Trastornos Mentales/tratamiento farmacológico , Psicotrópicos/uso terapéutico , Adolescente , Adulto , Anciano , Bélgica/epidemiología , Femenino , Humanos , Masculino , Trastornos Mentales/epidemiología , Persona de Mediana Edad , Inhibidores Selectivos de la Recaptación de Serotonina/uso terapéuticoRESUMEN
AIMS: This study reports the impact of mental disorders on daily functioning in the Belgian population. MATERIAL AND METHOD: A representative sample of 2419 non-institutionalised Belgian adults (18+) was interviewed between 2001 and 2002 using the Composite International Diagnostic Interview of the World Mental Health Surveys of the World Health Organisation (WMH-CIDI). Common mental disorders (mood, anxiety, and alcohol disorders--according to DSM-IV) and functional disabilities (according to the World Health Organization Disablement Assessment Scale--WHO-DAS-2) were assessed. RESULTS: Mood and anxiety disorders were associated with substantial levels of disability: social, emotional and physical domains were affected. Mood disorders were found to exert the largest impact in different domains of daily functioning, although the social life was most affected. Anxiety disorders were, on the contrary, more associated with emotional and physical discomfort. Persons with a alcohol disorder reported a substantially low impact on their daily functioning. CONCLUSIONS: Mental disorders affect several domains of daily functioning, with considerable limitations in personal and social life, but also with dramatic cutbacks in work productivity.
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Salud de la Familia , Trastornos Mentales/rehabilitación , Conducta Social , Adolescente , Adulto , Síntomas Afectivos , Anciano , Bélgica , Personas con Discapacidad , Empleo , Femenino , Encuestas Epidemiológicas , Humanos , Masculino , Persona de Mediana EdadRESUMEN
OBJECTIVE: To investigate socio-economic differences in the use of health services in Belgium and to explore to what extent eventual socio-economic inequalities are explained by differences in demographic determinants and health needs. DESIGN: Data was obtained from the 1997 Belgian national Health Interview Survey. In this survey information was collected on the health status, the life style and the medical consumption of a representative sample of the Belgian non-institutionalised population consisting of 8560 Belgian inhabitants aged 15 years and over. RESULTS: Lower socio-economic groups make more often use of the general practitioner and nursing care at home and are more often admitted to hospital than persons with a high socio-economical status. There is, however, no socio-economic gradient when the health status is taken into account. On the opposite, persons with a higher socio-economic status report more often a visit to a specialist, a physiotherapist or a dentist. For the health services for which this was investigated no association was found between socio-economic status and the volume of the use of health services. CONCLUSIONS: There are in Belgium still important socio-economic gradients in the use of some health services. These differences may be due to socio-economic inequities but could also indicate that the existing health facilities are not always used in an optimal way. Patient factors may be more important than supply factors in explaining the differential use of health services. Further research needs to focus on socio-economic differences in the reasons, the outcome and the quality of the provided care.
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Servicios de Salud/estadística & datos numéricos , Aceptación de la Atención de Salud/estadística & datos numéricos , Clase Social , Adolescente , Adulto , Anciano , Bélgica , Estudios Transversales , Composición Familiar , Femenino , Encuestas de Atención de la Salud , Servicios de Salud/clasificación , Estado de Salud , Humanos , Masculino , Persona de Mediana Edad , ProbabilidadRESUMEN
An epidemic of health complaints occurred in five Belgian schools in June 1999. A qualitative investigation described the scenario. The role of soft drinks was assessed by using a case-control study. Cases were students complaining of headache, dizziness, nausea, vomiting, abdominal pain, diarrhea, or trembling. Controls were students present at school on the day of the outbreak but not taken ill. An analysis was performed separately for school A, where the outbreak started, and was pooled for schools B-E. In school A, the attack rate (13.2%) was higher than in schools B-E (3.6%, relative risk = 3.6, 95% confidence interval (CI): 2.5, 5.3). Exclusive consumption of regular Coca-Cola (school A: odds ratio (OR) = 29.7, 95% CI: 1.32, 663.6; schools B-E: OR = 7.3, 95% CI: 2.9, 18.0) and low mental health score (school A: OR = 16.1, 95% CI: 1.3, 201.9; schools B-E: OR = 3.1, 95% CI: 1.5, 6.6) were independently associated with the illness. In schools B-E, consumption of Fanta, consumption of Coca-Cola light, and female gender were also associated with the illness. It seems reasonable to attribute the first cases of illness in school A to regular Coca-Cola consumption. However, mass sociogenic illness could explain the majority of the other cases.
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Bebidas Gaseosas/envenenamiento , Brotes de Enfermedades , Trastornos Somatomorfos/epidemiología , Adolescente , Bélgica/epidemiología , Estudios de Casos y Controles , Niño , Contaminación de Alimentos , Humanos , Sulfuro de Hidrógeno/envenenamiento , Modelos Logísticos , Estadísticas no Paramétricas , Óxidos de Azufre/envenenamiento , Encuestas y CuestionariosRESUMEN
alpha-Lactalbumin (alpha LA) forms a well-populated equilibrium molten globule state, while the homologous protein hen lysozyme does not. alpha LA is a two-domain protein and the alpha-domain is more structured in the molten globule state than is the beta-domain. Peptide models derived from the alpha-subdomain that contain the A, B, D, and 3(10) helices of alpha LA are capable of forming a molten globule state in the absence of the remainder of the protein. Here we report comparative studies of a peptide model derived from the same region of hen lysozyme and a set of chimeric alpha-lactalbumin--lysozyme constructs. Circular dichroism, dynamic light scattering, sedimentation equilibrium, and fluorescence experiments indicate that the lysozyme construct does not fold. Chimeric constructs were prepared to probe the origins of the difference in the ability of the two isolated subdomains to fold. The first consists of the A and B helices of alpha LA cross-linked to the D and C-terminal 3(10) helices of lysozyme. This construct is highly helical, while a second construct that contains the A and B helices of lysozyme cross-linked to the D and 3(10) helices of alpha LA does not fold. Furthermore, the disulfide cross-linked homodimer of the alpha LA AB peptide is helical, while the homodimer of the lysozyme AB peptide is unstructured. Thus, the AB helix region of alpha LA appears to have an intrinsic ability to form structure as long as some relatively nonspecific interactions can be made with other regions of the protein. Our studies show that the A and B helices plays a key role in the ability of the respective alpha-subdomains to fold.
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Lactalbúmina/química , Muramidasa/química , Fragmentos de Péptidos/química , Pliegue de Proteína , Proteínas Recombinantes de Fusión/química , Secuencia de Aminoácidos , Animales , Pollos , Dicroismo Circular , Dimerización , Humanos , Lactalbúmina/síntesis química , Lactalbúmina/genética , Luz , Modelos Moleculares , Datos de Secuencia Molecular , Muramidasa/síntesis química , Muramidasa/genética , Fragmentos de Péptidos/síntesis química , Fragmentos de Péptidos/genética , Estructura Secundaria de Proteína , Estructura Terciaria de Proteína/genética , Proteínas Recombinantes de Fusión/síntesis química , Dispersión de Radiación , Espectrometría de Fluorescencia , Relación Estructura-Actividad , Termodinámica , UltracentrifugaciónRESUMEN
The molten globule state of alpha-lactalbumin (alpha LA) has served as a paradigm for understanding the role of these partially folded states in protein folding. We previously showed that a peptide construct consisting of the A and B helices (residues 1-38) cross-linked to the D- and C-terminal 3(10) helices (residues 101-120) of alpha LA is capable of folding to a stable molten globule-like state. Here, we report the study of three peptide constructs that are designed to investigate the contribution two short hydrophobic sequences located near the C-terminus of alpha LA make to the structure and stability of the alpha LA molten globule state. These regions of the protein have been shown to form stable non-native structures in isolation. The three peptide constructs contain residues 1-38 cross-linked to three separate C-terminal peptides via the native 28-111 disulfide bond. The C-terminal peptides consist of residues 101-114, 106-120, and 106-114. The results of CD, fluorescence, ANS binding, and urea denaturation experiments indicate that constructs that lack either of the hydrophobic sequences (residues 101-105 and 115-120) are significantly less structured. These results highlight the importance of long-range, mutually stabilizing interactions within the molten globule state of the protein. Proteins 2001;42:237-242.
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Lactalbúmina/química , Secuencia de Aminoácidos , Dicroismo Circular , Humanos , Modelos Moleculares , Datos de Secuencia Molecular , Péptidos/síntesis química , Péptidos/química , Conformación Proteica , Desnaturalización Proteica , Pliegue de ProteínaRESUMEN
OBJECTIVES: The aim of the paper is to assess the significance of hearing disability as a public health problem through its association with multiple negative health outcomes: subjective health perception, mental health and social well-being. METHODS: The data come from the participants of the 1997 national health survey in Belgium, who were 15 years and older (n = 8,560). The presence and severity of the hearing disability was estimated through self-reporting. The association of hearing disability with the studied health outcomes was assessed using logistic regression while controlling for confounding factors such as age, sex, co-morbidity and socio-economic status. RESULTS: The prevalence of hearing disability is 7% in the population 15 years and older. The prevalence of subjective ill health (Odds Ratio (OR): 1.32), mental ill health (OR: 1.51), and a low appreciation of the social contacts (OR: 1.73) was higher in subjects with hearing disability. No association was found between hearing disability and the frequency of social contacts or with the functional content of the social contacts. CONCLUSIONS: Given the health and social consequences of hearing disability, increased public health attention, including both strategies for prevention, for identification and treatment, is warranted.
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Estado de Salud , Personas con Deficiencia Auditiva/psicología , Calidad de Vida , Ajuste Social , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Bélgica/epidemiología , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Personas con Deficiencia Auditiva/estadística & datos numéricosRESUMEN
Elucidating the properties of the denatured state of proteins under conditions relevant for their folding is a key factor in understanding the folding process. We show that a peptide corresponding to residues 111-120 of human alpha-lactalbumin has a pronounced propensity to adopt nonnative structure in aqueous solution. Two-dimensional NMR provides evidence for a structured, nonnative conformation in fast exchange with a random coil ensemble. A total of 78 Rotating Frame Overhauser Effects (ROEs) were used to calculate the conformation of the structured population. A nonnative cluster of hydrophobic residues involving the side chains of K114, W118, Ll119, and A120 is observed, which helps to stabilize a turn-like conformation in the vicinity of residues 115-118. The structure in 30% (vol/vol) TFE was also calculated. Interestingly, the addition of TFE did not simply amplify the population of the structured conformer observed in H2O, but instead induced a new conformation. The implications for the folding of the intact protein are discussed. We also discuss the implications of this study for the relevance of the use of mixed TFE/H2O solvent systems to study isolated peptides.
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Lactalbúmina/química , Pliegue de Proteína , Dicroismo Circular , Humanos , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Conformación Proteica , Desnaturalización ProteicaRESUMEN
Molten globule states are partially folded states of proteins which are compact and contain a high degree of secondary structure but which lack many of the fixed tertiary interactions associated with the native state. A set of peptides has been prepared in order to probe the role of local interactions in the vicinity of the Cys(6)-Cys(120) disulfide bond in stabilizing the molten globule state of human alpha-lactalbumin. Peptides derived from the N-terminal and C-terminal regions of human alpha-lactalbumin have been analyzed using nuclear magnetic resonance, circular dichroism, fluorescence spectroscopy and sedimentation equilibrium experiments. A peptide corresponding to the first helical region in the native protein, residues 1-13, is only slightly helical in isolation. Extending the peptide to include residues 14-18 results in a modest increase in helicity. A peptide derived from the C-terminal 12 residues, residues 112-123, is predominantly unstructured. Crosslinking the N- and C-terminal peptides by the native disulfide bond results in almost no increase in structure and there is no evidence for any significant cooperative structure formation over the range of pH 2.2-11.7. These results demonstrate that there is very little enhancement of local structure due to the formation of the Cys(6)-Cys(120) disulfide bond. This is in striking contrast to peptides derived from the region of the Cys(28)-Cys(111) disulfide.
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Disulfuros/química , Lactalbúmina/química , Secuencia de Aminoácidos , Dicroismo Circular , Concentración de Iones de Hidrógeno , Modelos Moleculares , Datos de Secuencia Molecular , Péptidos/síntesis química , Conformación Proteica , Pliegue de ProteínaRESUMEN
Molten globules are partially folded states of proteins which are generally believed to mimic structures formed during the folding process. In order to determine the minimal requirements for the formation of a molten globule state, we have prepared a set of peptide models of the molten globule state of human alpha-lactalbumin (alphaLA). A peptide consisting of residues 1-38 crosslinked, via the native 28-111 disulfide bond, to a peptide corresponding to residues 95-120 forms a partially folded state at pH 2.8 which has all of the characteristics of the molten globule state of alphaLA as judged by near and far UV CD, fluorescence, ANS binding and urea denaturation experiments. The structure of the peptide construct is the same at pH 7.0. Deletion of residues 95-100 from the construct has little effect. Thus, less than half the sequence is required to form a molten globule. Further truncation corresponding to the selective deletion of the A (residues 1-19) or D (residues 101-110) helices or the C-terminal 310 helix (residues 112-120) leads to a significant loss of structure. The loss of structure which results from the deletion of any of these three regions is much greater than that which would be expected based upon the non-cooperative loss of local helical structure. Deletion of residues corresponding to the region of the D helix or C-terminal 310 helix region results in a peptide construct which is largely unfolded and contains no more helical structure than is expected from the sum of the helicity of the two reduced peptides. These experiments have defined the minimum core structure of the alphaLA molten globule state.