Characterization of a Dominant Negative Mutant of the Cell Cycle Ubiquitin-conjugating Enzyme Cdc34

The yeast Saccharomyces cerevisiae CDC34 gene encodes a ubiquitin-conjugating enzyme that is required for the cell cycle G(1)/S transition. We show here that a dominant negative Cdc34 protein is generated by simultaneously replacing both Cys and Leu with Ser residues. Cys is an essential catalytic residue that forms a transient thiol ester with ubiquitin during catalysis, and Leu is highly conserved among all known ubiquitin-conjugating enzymes. Mutants that encode either an alanine or a serine at one or both of these two positions are inactive. Of these eight mutants, overexpression of CDC34-C95S,L99S in wild type strains was found to block cell growth. Although cells overexpressing Cdc34-C95S,L99S do not exhibit the characteristic multibudded phenotype of cdc34 temperature-sensitive or null mutants, this blockade is relieved by simultaneous overexpression of wild type Cdc34. Purified Cdc34-C95S,L99S protein can be shown to inhibit in vitro ubiquitination of the Cdc34-specific substrate, Cln2 protein. We suggest that Cdc34-C95S,L99S selectively sequesters a subset of Cdc34 substrates or regulators. These findings have implications for the structure/function relationships of ubiquitin-conjugating enzymes, and suggest a general method for identifying components and substrates of specific ubiquitination pathways of eukaryotes

Charged Vaidya-Tikekar model for super compact star

In this work, we explore a class of compact charged spheres that have been tested against experimental and observational constraints with some known compact stars candidates. The study is performed by considering the self-gravitating, charged, isotropic fluids which is more pliability in solving the Einstein-Maxwell equations. In order to determine the interior geometry, we utilize the Vaidya-Tikekar geometry for the metric potential with Riessner-Nordstrom metric as an exterior solution. In this models, we determine constants after selecting some particular values of M and R, for the compact objects SAX J1808.4-3658, Her X-1 and 4U 1538-52. The most striking consequence is that hydrostatic equilibrium is maintained for different forces, and the situation is clarified by using the generalized Tolman-Oppenheimer-Volkoff (TOV) equation. In addition to this, we also present the energy conditions, speeds of sound and compactness of stars that are very much compatible to that for a physically acceptable stellar model. Arising solutions are also compared with graphical representations that provide strong evidences for more realistic and viable models, both at theoretical and astrophysical scale.Comment: 13 Pages, 5 Figures and 4 Table

Magnetic field induced emergent inhomogeneity in a superconducting film with weak and homogeneous disorder

When a magnetic field is applied, the mixed state of a conventional Type II superconductor gets destroyed at the upper critical field Hc2, where the normal vortex cores overlap with each other. Here, we show that in the presence weak and homogeneous disorder the destruction of superconductivity with field follows a different route. Starting with a weakly disordered NbN thin film ( Tc ~ 9K ), we show that under the application of magnetic field the superconducting state becomes increasingly granular, where lines of vortices separate the superconducting islands. Consequently, phase fluctuations between these islands give rise to a field induced pseudogap phase, which has a gap in the electronic density of states but where the global zero resistance state is destroyed.Comment: New data added in this versio

Under-nutrition among adolescents: a survey in five secondary schools in rural Goa.

BACKGROUND: This study was done in 2008-09 to assess the nutritional status among adolescents (10-19 years of age, Classes V-XII) in 5 schools in rural Goa to inform the content of a health promotion intervention in these schools. METHODS: Three methods were used. First, nutritional status was measured by assessing body mass index among 1015 students during a health camp in each school. Second, a diet analysis was done to measure energy and protein Intake of 76 randomly selected underweight students. Third, a self-report questionnaire survey measured the prevalence of hunger among 684 students. RESULTS: One-third of students (338; 37.8% boys and 27.5% girls) who attended the health camps were underweight and 59.2% of the 684 students who completed the survey reported experiencing hunger due to inadequate food consumption. More boys were underweight than girls (p<0.001) and under-nutrition was uniform across all the years of schooling. Energy intake of underweight students was significantly lower than the recommended daily allowance. The results were shared with the School Health Promotion Advisory Boards to generate information on the stakeholders' perception about the issue and ways to address it. CONCLUSION: There is an immediate need to address the high burden of hunger and under-nutrition in adolescents of both sexes in schools by instituting routine annual monitoring of nutritional status, extending the mid-day meal programme to all school-going adolescents, providing nutritional counselling for underweight adolescents and expanding research on the causes and impact of under-nutrition and evaluation of the impact of the enhanced mid-day meal programme

Equation of motion approach to non-adiabatic quantum charge pumping

We use the equations of motion of non-interacting electrons in a one-dimensional system to numerically study different aspects of charge pumping. We study the effects of the pumping frequency, amplitude, band filling and finite bias on the charge pumped per cycle, and the Fourier transforms of the charge and energy currents in the leads. Our method works for all values of parameters, and gives the complete time-dependences of the current and charge at any site of the system. Our results agree with Floquet and adiabatic scattering theory where these are applicable, and provides support for a mechanism proposed elsewhere for charge pumping by a traveling potential wave. For non-adiabatic and strong pumping, the charge and energy currents are found to have a marked asymmetry between the two leads, and pumping can work even against a substantial bias.Comment: 11 pages including 9 figures; expanded the paper to discuss left-right asymmetry of charge and energy currents, and effect of finite bia