Motor step size and ATP coupling efficiency of the dsDNA translocase EcoR124I

The Type I restriction-modification enzyme EcoR124I is an archetypical helicase-based dsDNA translocase that moves unidirectionally along the 3′–5′ strand of intact duplex DNA. Using a combination of ensemble and single-molecule measurements, we provide estimates of two physicochemical constants that are fundamental to a full description of motor protein activity—the ATP coupling efficiency (the number of ATP consumed per base pair) and the step size (the number of base pairs transported per motor step). Our data indicate that EcoR124I makes small steps along the DNA of 1 bp in length with 1 ATP consumed per step, but with some uncoupling of the ATPase and translocase cycles occurring so that the average number of ATP consumed per base pair slightly exceeds unity. Our observations form a framework for understanding energy coupling in a great many other motors that translocate along dsDNA rather than ssDNA

MIP/Aquaporin 0 Represents a Direct Transcriptional Target of PITX3 in the Developing Lens

The PITX3 bicoid-type homeodomain transcription factor plays an important role in lens development in vertebrates. PITX3 deficiency results in a spectrum of phenotypes from isolated cataracts to microphthalmia in humans, and lens degeneration in mice and zebrafish. While identification of downstream targets of PITX3 is vital for understanding the mechanisms of normal ocular development and human disease, these targets remain largely unknown. To isolate genes that are directly regulated by PITX3, we performed a search for genomic sequences that contain evolutionarily conserved bicoid/PITX3 binding sites and are located in the proximity of known genes. Two bicoid sites that are conserved from zebrafish to human were identified within the human promoter of the major intrinsic protein of lens fiber, MIP/AQP0. MIP/AQP0 deficiency was previously shown to be associated with lens defects in humans and mice. We demonstrate by both chromatin immunoprecipitation and electrophoretic mobility shift assay that PITX3 binds to MIP/AQP0 promoter region in vivo and is able to interact with both bicoid sites in vitro. In addition, we show that wild-type PITX3 is able to activate the MIP/AQP0 promoter via interaction with the proximal bicoid site in cotransfection experiments and that the introduction of mutations disrupting binding to this site abolishes this activation. Furthermore, mutant forms of PITX3 fail to produce the same levels of transactivation as wild-type when cotransfected with the MIP/AQP0 reporter. Finally, knockdown of pitx3 in zebrafish affects formation of a DNA-protein complex associated with mip1 promoter sequences; and examination of expression in pitx3 morphant and control zebrafish revealed a delay in and reduction of mip1 expression in pitx3-deficient embryos. Therefore, our data suggest that PITX3 is involved in direct regulation of MIP/AQP0 expression and that the alteration of MIP/AQP0 expression is likely to contribute to the lens phenotype in cataract patients with PITX3 mutations

Спільна робота профілів ЛСТК з обшивкою

In the work, the efforts were made in the joints of the frame elements with the skin, ensuring the normal operation of the structure. The cases of the appearance of forces in joints that perceive the conditional lateral force along the length of the compressed element (the construction of the wall panel) and redistribute the external forces between the frame elements and the skin are considered.В работе производилась оценке усилий в узлах соединения элементов каркаса с обшивкой, обеспечивающих нормальную работу конструкции. Рассмотрены случаи возникновения усилий в узлах соединения, воспринимающих условную поперечную силу по длине сжатого элемента (конструкции стеновой панели) и перераспределяющих внешние усилия между элементами каркаса и обшивкой.В роботі проводилася оцінці зусиль у вузлах з'єднання елементів каркаса з обшивкою, що забезпечують нормальну роботу конструкції. Розглянуто випадки виникнення зусиль у вузлах з'єднання, що сприймають умовну поперечну силу по довжині стисненого елемента (конструкції стіновий панелі) і перерозподіляють зовнішні зусилля між елементами каркаса і обшивкою

Estimation of the conversion coefficients from dose-area product to effective dose for barium meal examinations for adult patients

Fluoroscopic examinations of the upper gastro-intestinal tract and, especially, barium meal examinations, are commonly performed in a majority of hospitals. These examinations are associated both with substantial individual patient doses and contribution to the collective dose from medical exposure. Effective dose estimation for this type of examinations is complicated due to: 1) the necessity to simulate the moving X-ray irradiation field; 2) differences in study structure for the individual patients; 3) subjectivity of the operators; and 4) differences in the X-ray equipment. The aim of the current study was to estimate conversion coefficients from dose-area product to effective dose for barium meal examinations for the over couch and under couch exposure conditions. The study was based on data collected in the X-ray unit of the surgical department of the St-Petersburg Mariinsky hospital. A model of patient exposure during barium meal examination was developed based on the collected data on fluoroscopy protocols and adult patient irradiation geometry. Conversion coefficients were calculated using PCXMC 2.0 software. Complete examinations were converted into a set of typical fluoroscopy phases and X-ray images, specified by the examined anatomical region and the projection of patient exposure. Conversion coefficients from dose-area product to effective dose were calculated for each phase of the examination and for the complete examination. The resulting values of the conversion coefficients are comparable with published data. Variations in the absolute values of the conversion coefficients can be explained by differences in clinical protocols, models for the estimation of the effective dose and parameters of barium meal examinations. The proposed approach for estimation of effective dose considers such important features of fluoroscopic examinations as: 1) non-uniform structure of examination, 2) significant movement of the X-ray tube within a single fluoroscopic phase, and 3) the variety of exposure geometries within complete examination