A linear energy transfer distributions computation method for inhomogeneous medium by using the water equivalent ratio approximation.

Dose-averaged linear energy transfer (LET), LETd is widely used in proton therapy. Compared with analytical models, Monte Carlo (MC) simulations are more accurate in obtaining LETd distributions, but they are time-consuming. This study used the 3D LETd distributions of proton beam spots in water by MC simulations as a benchmark data set. Subsequently, by combining the water equivalent ratio of various human tissues, the 3D LETd distributions of clinical cases could be quickly obtained. Our method was applied to a single spot of 160 MeV proton beam in a water-bone phantom and a pelvic case. We also computed the 3D LETd distributions for multiple proton beam spots in the pelvic case and a lung case. The results of our method were compared with the results of MC simulations, demonstrating that our method can rapidly provide 3D LETd distributions of clinical cases with acceptable differences from MC simulations.

CARP-2 is an endosome-associated ubiquitin ligase for RIP and regulates TNF-induced NF-kappaB activation.

BACKGROUND: The proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) elicits cellular responses by signaling through a receptor complex that includes the essential adaptor molecule RIP. One important consequence of signaling is activation of the transcription factor NF-kappaB, and failure to downregulate TNF-induced NF-kappaB transcriptional activity results in chronic inflammation and death. Internalization of the receptor complex plays an important regulatory role in TNF signaling. RESULTS: We report that CARP-2, a RING domain-containing ubiquitin protein ligase (E3), is a negative regulator of TNF-induced NF-kappaB activation. By virtue of its phospholipid-binding FYVE domain, CARP-2 localized to endocytic vesicles, where it interacted with internalized TNF-receptor complex, resulting in RIP ubiquitination and degradation. Knockdown of CARP-2 stabilized TNFR1-associated polyubiquitinated RIP levels after TNF simulation and enhanced activation of NF-kappaB. CONCLUSIONS: CARP-2 acts at the level of endocytic vesicles to limit the intensity of TNF-induced NF-kappaB activation by the regulated elimination of a necessary signaling component within the receptor complex.

[Progress in the studies of DNA-protein interactions by atomic force microscopy].

Atomic force microscopy (AFM) has been applied in many biological investigations in recent years, and this review focuses on the application of AFM in DNA-protein interactions. AFM images of static DNA-protein complexes, in air and in liquid, can be used to obtain quantitative and qualitative information on the structure of different complexes. And dynamic AFM images of DNA-protein complexation in real time under liquid conditions will help to understand biological processes and mechanisms at single molecule level. In addition, the measurement of intermolecular forces between biomolecules also provides new opportunities for studying mechanical properties of biomolecules and the interactions in their native environment. AFM has revealed many mechanisms of gene regulation, and will play a more and more important role in life science research.

[AFLP fingerprinting map analysis of Pleurotus ostreatus].

AFLP analysis was carried out with 14 Pleurotus ostreatus strains from different areas. Optimal conditions of the AFLP fingerprinting analysis for P. ostreatus were first tested and the results showed that the primer pairs E-3/M-3 especially E-AGC/M-CAT and E-AGC/M-ACC could give more amplified DNA fragments than others like E-2/M-1 or E-2/M-3. From the fingerprinting map of the primer pair E-AGC/M-CAT, 184 clear and stable DNA bands were observed, including 101 polymorphous bands that are accounted for 54.89%. The genetic similarity coefficient and genetic distance were calculated from AFLP data among 14 P. ostreatus strains. The genetic distance between these strains ranged from 0.192 to 0.754, indicating that P. ostreatus was rich in genetic diversity. UPGMA cluster analysis was also performed. It's shown that 14 P. ostreatus strains are divided into six groups, and strains from same areas or with similar best-growth temperature usually have higher comparability in the UPGMA tree. P. ostreatus P17 and P. ostreatus Za3, P. ostreatus Min31 and P. ostreatus Yiping have intimate genetic relationships with each other respectively which were consistent with its geographical distribution and best growth temperature. P. ostreatus Ce5 showed remarkable genetic differentiation, which has farther genetic relationships compared with other P. ostreatus strains. In addition, the reasons for cluster results of strains from AFLP data consistent with morphology, geographical distribution and optimal condition of AFLP fingerprinting analysis for P. ostreatus were discussed.

Expression and functional analysis of an inhibitor of apoptosis protein from Trichoplusia ni.

An inhibitor of the apoptosis protein (IAP) family gene from Trichoplusia ni, Tn-IAP1v, a variant of lepidopteran Tn-IAP1, was cloned by RT-PCR. There are six single nucleotide polymorphisms between the two Tn-IAP1 variants, resulting in three predicted single amino acid polymorphisms. With the GST fusion expression system, soluble recombinant Tn-IAP1v was highly expressed in Escherichia coli and then purified by affinity chromatography. Caspase inhibition assays indicated that recombinant Tn-IAP1v could specifically inhibit human caspase-9 in vitro instead of caspase-3, -7, and -8, which was further confirmed by the observation that recombinant Tn-IAP1v can directly bind caspase-9 in the protein pull-down assay. These results suggested that Tn-IAP1v might serve as an initiator caspase inhibitor in vivo in the conserved mitochondria apoptotic pathway.

Fusion and Expression of the Genes Encoding Murine-Human Chimeric Heavy Chain to Carcinoembryonic Antigen with Core-streptavidin Gene.

In order to reduce the human anti-murine antibody (HAMA) in radioimmunotherapy, the gene encoding the heavy chain variable region (V(H)) of the murine monoclonal antibody with high specificity and affinity to carcinoembryonic antigen was fused to the human C(gamma3) gene to construct the murine-human chimeric heavy chain antibody gene, then was linked to core-streptavidin which can specifically bind to biotin, facilitating its purification and radioisotope labeling. The fusion gene was expressed in E.coli at high level, accounting for 24% of the total bacteria protein, and was characterized by SDS-PAGE and Western-blots. When using RIA the content of inclusion bodies was denatured and followed by renaturation, it was shown by using RIA to possess ability to bind to its specific antigen of CEA. Using horseradish peroxidase (HRP) labeled biotin as antibody in Western-blots, one band of 70 kD only was detected, demonstrating the fusion protein not only had the ability to bind CEA, but also could bind biotin specifically.