RESUMEN
Using NMR and Monte Carlo (MC) methods, we investigate the stability and dynamics of superoxide dismutase 1 (SOD1) in homogeneous crowding environments, where either bovine pancreatic trypsin inhibitor (BPTI) or the B1 domain of streptococcal protein G (PGB1) serves as a crowding agent. By NMR, we show that both crowders, and especially BPTI, cause a drastic loss in the overall stability of SOD1 in its apo monomeric form. Additionally, we determine chemical shift perturbations indicating that SOD1 interacts with the crowder proteins in a residue-specific manner that further depends on the identity of the crowding protein. Furthermore, the specificity of SOD1-crowder interactions is reciprocal: chemical shift perturbations on BPTI and PGB1 identify regions that interact preferentially with SOD1. By MC simulations, we investigate the local unfolding of SOD1 in the absence and presence of the crowders. We find that the crowders primarily interact with the long flexible loops of the folded SOD1 monomer. The basic mechanisms by which the SOD1 ß-barrel core unfolds remain unchanged when adding the crowders. In particular, both with and without the crowders, the second ß-sheet of the barrel is more dynamic and unfolding-prone than the first. Notably, the MC simulations (exploring the early stages of SOD1 unfolding) and the NMR experiments (under equilibrium conditions) identify largely the same set of PGB1 and BPTI residues as prone to form SOD1 contacts. Thus, contacts stabilizing the unfolded state of SOD1 in many cases appear to form early in the unfolding reaction.
Asunto(s)
Aprotinina/metabolismo , Proteínas Bacterianas/metabolismo , Desplegamiento Proteico , Superóxido Dismutasa-1/metabolismo , Animales , Aprotinina/química , Proteínas Bacterianas/química , Escherichia coli/genética , Humanos , Método de Montecarlo , Resonancia Magnética Nuclear Biomolecular , Unión Proteica , Estabilidad Proteica , Estructura Secundaria de Proteína , Streptococcus/química , Superóxido Dismutasa-1/química , Superóxido Dismutasa-1/genéticaRESUMEN
Protein-based encapsulation systems have a wide spectrum of applications in targeted delivery of cargo molecules and for chemical transformations in confined spaces. By engineering affinity between cargo and container proteins it has been possible to enable the efficient and specific encapsulation of target molecules. Missing in current approaches is the ability to turn off the interaction after encapsulation to enable the cargo to freely diffuse in the lumen of the container. Separation between cargo and container is desirable in drug delivery applications and in the use of capsids as catalytic nanoparticles. We describe an encapsulation system based on the hepatitisâ B virus capsid in which an engineered high-affinity interaction between cargo and capsid proteins can be modulated by Ca2+ . Cargo proteins are loaded into capsids in the presence of Ca2+ , while ligand removal triggers unbinding inside the container. We observe that confinement leads to hindered rotation of cargo inside the capsid. Application of the designed container for catalysis was also demonstrated by encapsulation of an enzyme with ß-glucosidase activity.
Asunto(s)
Calcio/química , Cápside/química , Preparaciones de Acción Retardada/química , Virus de la Hepatitis B/química , Proteínas/administración & dosificación , Proteínas de la Cápside/química , Sistemas de Liberación de Medicamentos , Modelos Moleculares , Espectrometría de FluorescenciaRESUMEN
Using Monte Carlo methods, we explore and compare the effects of two protein crowders, BPTI and GB1, on the folding thermodynamics of two peptides, the compact helical trp-cage and the ß-hairpin-forming GB1m3. The thermally highly stable crowder proteins are modeled using a fixed backbone and rotatable side-chains, whereas the peptides are free to fold and unfold. In the simulations, the crowder proteins tend to distort the trp-cage fold, while having a stabilizing effect on GB1m3. The extent of the effects on a given peptide depends on the crowder type. Due to a sticky patch on its surface, BPTI causes larger changes than GB1 in the melting properties of the peptides. The observed effects on the peptides stem largely from attractive and specific interactions with the crowder surfaces, and differ from those seen in reference simulations with purely steric crowder particles.
Asunto(s)
Simulación por Computador , Método de Montecarlo , Péptidos/química , Animales , Aprotinina/química , Humanos , Pliegue de Proteína , Receptores de GABA-B/química , TermodinámicaRESUMEN
While steric crowders tend to stabilize globular proteins, it has been found that protein crowders can have an either stabilizing or destabilizing effect, where a destabilization may arise from nonspecific attractive interactions between the test protein and the crowders. Here, we use Monte Carlo replica-exchange methods to explore the equilibrium behavior of the miniprotein trp-cage in the presence of protein crowders. Our results suggest that the surrounding crowders prevent trp-cage from adopting its global native fold, while giving rise to a stabilization of its main secondary-structure element, an α-helix. With the crowding agent used (bovine pancreatic trypsin inhibitor), the trp-cage-crowder interactions are found to be specific, involving a few key residues, most of which are prolines. The effects of these crowders are contrasted with those of hard-sphere crowders.
Asunto(s)
Modelos Moleculares , Simulación de Dinámica Molecular , Péptidos/química , Proteínas/química , Método de Montecarlo , Pliegue de Proteína , Estructura Secundaria de Proteína , TermodinámicaRESUMEN
BACKGROUND: Recent studies have indicated that the 11-item Psychotic Depression Assessment Scale (PDAS), consisting of the 6-item melancholia subscale (HAM-D6) of the Hamilton Depression Rating Scale and 5 psychosis items from the Brief Psychiatric Rating Scale (BPRS), is a valid measure for the severity of psychotic depression. The aim of this study was to subject the PDAS, and its depression (HAM-D6) and psychosis (BPRS5) subscales to further validation. METHODS: Patients diagnosed with psychotic depression at Danish psychiatric hospitals participated in semi-structured interviews. Video recordings of these interviews were assessed by two experienced psychiatrists (global severity rating of psychotic depression, depressive symptoms and psychotic symptoms) and by two young physicians (rating on 27 symptom items, including the 11 PDAS items). The clinical validity and responsiveness of the PDAS and its subscales was investigated by Spearman correlation analysis of the global severity ratings and the PDAS, HAM-D6, and BPRS5 total scores. The unidimensionality of the scales was tested by item response theory analysis (Mokken). RESULTS: Ratings from 39 participants with unipolar psychotic depression and nine participants with bipolar psychotic depression were included in the analysis. The Spearman correlation analysis indicated that the PDAS, HAM-D6 and BPRS5 were clinically valid (correlation coefficients from 0.78 to 0.85, p<0.001) and responsive (correlation coefficients from 0.72 to 0.86, p<0.001) measures of psychotic depression. According to the Mokken analysis, all three scales were unidimensional. CONCLUSIONS: The clinical validity, responsiveness and unidimensionality of the PDAS and its subscales were confirmed in an independent sample of patients with psychotic depression.
Asunto(s)
Trastorno Depresivo Mayor/diagnóstico , Escalas de Valoración Psiquiátrica , Trastornos Psicóticos/diagnóstico , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Trastorno Depresivo Mayor/psicología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Psicometría , Trastornos Psicóticos/psicología , Reproducibilidad de los Resultados , Adulto JovenRESUMEN
Pott's puffy tumour is a well known but rare complication of frontal sinusitis or trauma. It was first described by Sir Percivall Pott in 1768. Pott's puffy tumour is characterized by subperio-steal abscess associated with osteomyelitis. This report presents a 43-year-old patient with schizophrenia who developed Pott's puffy tumour due to lack of sufficient treatment of sinusitis. Furthermore, the literature on the clinical manifestations, diagnosis, microbiology, treatment, and complications of Pott's puffy tumour is reviewed.
Asunto(s)
Sinusitis Frontal/complicaciones , Tumor Hinchado de Pott/etiología , Adulto , Sinusitis Frontal/tratamiento farmacológico , Humanos , Masculino , Tumor Hinchado de Pott/diagnóstico por imagen , Tumor Hinchado de Pott/patología , Tumor Hinchado de Pott/cirugía , Esquizofrenia/complicaciones , Infecciones Estreptocócicas/complicaciones , Infecciones Estreptocócicas/tratamiento farmacológico , Streptococcus intermedius/aislamiento & purificación , Tomografía Computarizada por Rayos XRESUMEN
Copper, zinc superoxide dismutase 1 (SOD1) is a ubiquitous homodimeric enzyme, whose misfolding and aggregation play a potentially key role in the neurodegenerative disease amyotrophic lateral sclerosis (ALS). SOD1 aggregation is thought to be preceded by dimer dissociation and metal loss, but the mechanisms by which the metal-free monomer aggregates remain incompletely understood. Here we use implicit solvent all-atom Monte Carlo (MC) methods to investigate the local unfolding dynamics of the ß-barrel-forming SOD1 monomer. Although event-to-event variations are large, on average, we find clear differences in dynamics among the eight strands forming the ß-barrel. Most dynamic is the eighth strand, ß8, which is located in the dimer interface of native SOD1. For the four strands in or near the dimer interface (ß1, ß2, ß7, and ß8), we perform aggregation simulations to assess the propensity of these chain segments to self-associate. We find that ß1 and ß2 readily self-associate to form intermolecular parallel ß-sheets, whereas ß8 shows a very low aggregation propensity.
Asunto(s)
Superóxido Dismutasa/química , Secuencia de Aminoácidos , Esclerosis Amiotrófica Lateral/enzimología , Esclerosis Amiotrófica Lateral/patología , Cobre/química , Dimerización , Humanos , Método de Montecarlo , Estructura Secundaria de Proteína , Desplegamiento Proteico , Superóxido Dismutasa/metabolismo , Superóxido Dismutasa-1 , Zinc/químicaRESUMEN
BACKGROUND/AIMS: The aim of the study was to assess the prevalence of persisting symptoms 6 months or more after eclampsia. METHODS: During a 2-year period (mid-1998 to mid-2000), 210 patients with eclampsia were included in a prospective cohort study of eclampsia in Denmark, Norway and Sweden. One hundred and twenty-three women (59%) were followed up with a structured telephone interview, 6-24 months (median 11) after their eclamptic fit. RESULTS: At the time of follow-up, 63 women (51%) had at least one persistent symptom; 2 patients had severe neurological sequels (hemiparesis and dysarthria), 11% had visual disturbances, 22% had problems concentrating or recalling phone numbers and messages, 18% reported frequent headaches and 10% had vertigo or balance problems. CONCLUSION: Although few women suffered from severe sequels, many women had persisting symptoms following eclampsia indicating a need for follow-up of these patients. A case-control study comparing the health and symptoms between women having suffered from eclampsia and women without this complication may therefore be justified.