Polar or Apolar—The Role of Polarity for Urea-Induced Protein Denaturation

Urea-induced protein denaturation is widely used to study protein folding and stability; however, the molecular mechanism and driving forces of this process are not yet fully understood. In particular, it is unclear whether either hydrophobic or polar interactions between urea molecules and residues at the protein surface drive denaturation. To address this question, here, many molecular dynamics simulations totalling ca. 7 µs of the CI2 protein in aqueous solution served to perform a computational thought experiment, in which we varied the polarity of urea. For apolar driving forces, hypopolar urea should show increased denaturation power; for polar driving forces, hyperpolar urea should be the stronger denaturant. Indeed, protein unfolding was observed in all simulations with decreased urea polarity. Hyperpolar urea, in contrast, turned out to stabilize the native state. Moreover, the differential interaction preferences between urea and the 20 amino acids turned out to be enhanced for hypopolar urea and suppressed (or even inverted) for hyperpolar urea. These results strongly suggest that apolar urea–protein interactions, and not polar interactions, are the dominant driving force for denaturation. Further, the observed interactions provide a detailed picture of the underlying molecular driving forces. Our simulations finally allowed characterization of CI2 unfolding pathways. Unfolding proceeds sequentially with alternating loss of secondary or tertiary structure. After the transition state, unfolding pathways show large structural heterogeneity

KIFC1-Like Motor Protein Associates with the Cephalopod Manchette and Participates in Sperm Nuclear Morphogenesis in Octopus tankahkeei

Nuclear morphogenesis is one of the most fundamental cellular transformations taking place during spermatogenesis. In rodents, a microtubule-based perinuclear structure, the manchette, and a C-terminal kinesin motor KIFC1 are believed to play crucial roles in this process. Spermatogenesis in Octopus tankahkeei is a good model system to explore whether evolution has created a cephalopod prototype of mammalian manchette-based and KIFC1-dependent sperm nuclear shaping machinery.We detected the presence of a KIFC1-like protein in the testis, muscle, and liver of O. tankahkeei by Western Blot. Then we tracked its dynamic localization in spermatic cells at various stages using Immunofluorescence and Immunogold Electron Microscopy. The KIFC1-like protein was not expressed at early stages of spermatogenesis when no significant morphological changes occur, began to be present in early spermatid, localized around and in the nucleus of intermediate and late spermatids where the nucleus was dramatically elongated and compressed, and concentrated at one end of final spermatid. Furthermore, distribution of the motor protein during nuclear elongation and condensation overlapped with that of the cephalopod counterpart of manchette at a significant level.The results support the assumption that the protein is actively involved in sperm nuclear morphogenesis in O. tankahkeei possibly through bridging the manchette-like perinuclear microtubules to the nucleus and assisting in the nucleocytoplasmic trafficking of specific cargoes. This study represents the first description of the role of a motor protein in sperm nuclear shaping in cephalopod

Aspectos clínico-patológicos do carcinoma bronquioloalveolar e sobrevida em pacientes no estágio clínico I Clinicopathological aspects of and survival in patients with clinical stage I bronchioloalveolar carcinoma

OBJETIVO: Analisar os aspectos clínico-patológicos do carcinoma bronquioloalveolar (CBA) e a sobrevida em uma amostra de pacientes com estadiamento clínico I. MÉTODOS: Foram estudados retrospectivamente 26 pacientes com diagnóstico de CBA e estágio clínico I, , segundo a classificação tumor-node-metastasis (TNM, tumor-linfonodo-metástase),(15)operados no Instituto de Doenças do Tórax da Universidade Federal do Rio de Janeiro, na cidade do Rio de Janeiro, RJ, entre 1987 e 2007, quanto a variáveis clínico-patológicas e radiológicas, mortalidade e sobrevida. Os dados foram colhidos dos prontuários médicos dos pacientes e analisados estatisticamente. RESULTADOS: Houve predomínio de mulheres (n = 16). A idade média ao diagnóstico foi de 68,5 anos. Houve predomínio de tabagistas (69,2%). As formas de apresentação assintomática (84,6%) e nodular (88,5%) foram as mais comuns. Houve predileção pelos lobos superiores (57,7%). O estágio patológico IB foi o mais comum, seguido pelos estágios IA e IIB (46,2%, 38,4% e 15,4%, respectivamente). Não houve óbitos hospitalares. Quatro pacientes faleceram durante o seguimento pós-operatório, com tempo livre de doença médio de 21,3 meses. A taxa de sobrevida global em cinco anos foi 83%. A probabilidade de sobrevida para os pacientes diagnosticados depois de 1999 tendeu a ser maior do que para aqueles diagnosticados até 1999 (taxa de sobrevida em três anos: 92% vs. 68%; p = 0,07). CONCLUSÕES: Os aspectos clínico-patológicos da amostra estudada foram semelhantes àqueles de estudos anteriores em pacientes com CBA.<br>OBJECTIVE: To analyze the clinicopathological aspects of bronchioloalveolar carcinoma (BAC) and the survival in a sample of patients at clinical stage I. METHODS: A retrospective study involving 26 patients diagnosed with clinical stage I BAC and undergoing surgery at the Thoracic Diseases Institute of the Federal University of Rio de Janeiro, in the city of Rio de Janeiro, Brazil, between 1987 and 2007. We analyzed clinicopathological and radiological aspects, as well as mortality and survival. The data, which were collected from the medical charts of the patients, were statistically analyzed. RESULTS: Females predominated (n = 16). The mean age at diagnosis was 68.5 years. Most patients were active smokers (69.2%). The most common forms of presentation of BAC were the asymptomatic form (84.6%) and the nodular form (88.5%). Involvement of the upper lobes predominated (57.7%). Stage IB was the most common pathological stage, followed by stages IA and IIB (46.2%, 38.4% and 15.4%, respectively). There was no in-hospital mortality. Four patients died during the postoperative follow-up, with a mean disease-free survival time of 21.3 months. The overall five-year survival rate was 83%. The probability of survival for the patients diagnosed after 1999 showed a trend toward an increase when compared with that for those diagnosed up through 1999 (three-year survival rate: 92% vs. 68%; p = 0.07). CONCLUSIONS: The clinicopathological aspects of this study sample were similar to those of patients with BAC evaluated in previous studies