RESUMO
Single-particle tracking experiments have been used widely to study the heterogeneity of a sample. Segments with dissimilar diffusive behaviors are associated with different intermediate states, usually by visual inspection of the tracking trace. A likelihood-based, systematic approach is presented to remove this incertitude. Maximum likelihood estimators are derived for the determination of diffusion coefficients. A likelihood ratio test is applied to the localization of the changes in them. Simulations suggest that the proposed procedure is statistically robust and is able to quantitatively recover time-dependent changes in diffusion coefficients even in the presence of large measurement noise.
Assuntos
Funções Verossimilhança , Modelos Estatísticos , Nanopartículas , Algoritmos , Intervalos de Confiança , Difusão , Microscopia de Vídeo , Movimento (Física) , Processos EstocásticosRESUMO
The crystallization of 16 proteins was carried out using 60 wells on board Shenzhou 3 in 2002. Although the mission was only 7 days, careful and concerted planning at all stages made it possible to obtain crystals of improved quality compared to their ground controls for some of the proteins. Significantly improved resolutions were obtained from diffracted crystals of 4 proteins. A complete data set from a space crystal of the PEP carboxykinase yielded significantly higher resolution (1.46A vs. 1.87A), I/sigma (22.4 vs. 15.5), and a lower average temperature factor (29.2A(2) vs. 42.9A(2)) than the best ground-based control crystal. The 3-D structure of the enzyme is well improved with significant ligand density. It has been postulated that the reduced convection and absence of macromolecule sedimentation under microgravity have advantages/benefits for protein crystal growth. Improvements in experimental design for protein crystal growth in microgravity are ongoing.
Assuntos
Cristalização/métodos , Cristalografia por Raios X/métodos , Citocromos b5/química , Elétrons , Escherichia coli/enzimologia , Análise de Fourier , Humanos , Modelos Moleculares , Fosfoenolpiruvato Carboxiquinase (ATP)/química , Transdução de Sinais , Software , Voo Espacial , Temperatura , Ausência de PesoRESUMO
A Controllable and Observable Protein Crystallization Facility (ACOP) was developed in 1999 for space experiment in the Get Away Special canister of Space Shuttle. To regulate the vapor diffusion rate, in a crystallization chamber, five cells each containing precipitant solution of different concentrations, exposed to one protein cell in turn. Five layers of chambers were overlapped coaxially. The crystallization process was observed and recorded by digital cameras. Structure of facility and result of image sequence were given.
Assuntos
Cristalografia/instrumentação , Proteínas/química , Voo Espacial/instrumentação , Ausência de Peso , Cristalização , Desenho de Equipamento , Estudos de Avaliação como Assunto , FotografaçãoRESUMO
AIM: To explore the association of methylation of the CpG island in the promotor of the p16 tumor suppressor gene with the clinicopathological characteristics of the colorectal cancers. METHODS: Methylation-specific PCR (MSP) was used to detect p16 methylation of 62 sporadic colorectal cancer specimens. RESULTS: p16 methylation was detected in 42% of the tumors.Dukes'staging was associated with p16 methylation status.p16 methylation occurred more frequently in Dukes'C and D patients (75.9%) than in Dukes'A and B patients (12.1%). CONCLUSION: p16 methylation plays a role in the carcinogenesis of a subset of colorectal cancer, and it might be linked to poor prognosis.