Clonal variation in cell surface display of an H-2 protein lacking a cytoplasmic tail

Truncated variants of the gene encoding H-2Ld, an integral membrane protein encoded by the major histocompatibility complex, were constructed by in vitro mutagenesis to elucidate the function of charged amino acids found on the cytoplasmic side of the transmembrane (TM) region. Analysis of cloned L cells transfected with these genes shows that the seven amino acids following the TM segment, four of which are basic, enhance the cell surface expression of H-2Ld protein but are not required for it. However, some clones do not express a tailless H-2Ld protein on the cell surface but express it intracellularly where it has a long half-life. Turnover measurements on cell surface H-2Ld proteins suggest that the basic residues following the TM segment are not a "stop transfer" sequence (Blobel, G., 1980, Proc. Natl. Acad. Sci. USA., 77:1496-1500) which anchors the H-2Ld protein in the membrane. Pulse-chase and endoglycosidase H sensitivity studies show that H-2Ld proteins lacking some or all of the basic residues and H-2Ld proteins which have a full-length cytoplasmic tail are processed with different kinetics. These results suggest an involvement of the membrane-proximal region of the cytoplasmic tail in the intracellular transport of H-2Ld. We further suggest that the L cell clones which do and do not express a tailless H-2Ld protein on the cell surface differ in the ability to transport a tailless integral membrane protein to the cell surface

Spacecraft design sensitivity for a disaster warning satellite system

A disaster warning satellite (DWS) is described for warning the general public of impending natural catastrophes. The concept is responsive to NOAA requirements and maximizes the use of ATS-6 technology. Upon completion of concept development, the study was extended to establishing the sensitivity of the DWSS spacecraft power, weight, and cost to variations in both warning and conventional communications functions. The results of this sensitivity analysis are presented

The magnetic field of the double-lined spectroscopic binary system HD 5550

(Abridged) In the framework of the BinaMicS project, we have begun a study of the magnetic properties of a sample of intermediate-mass and massive short-period binary systems, as a function of binarity properties. We report in this paper the characterisation of the magnetic field of HD 5550, a double-lined spectroscopic binary system of intermediate-mass, using high-resolution spectropolarimetric Narval observations of HD 5550. We first fit the intensity spectra using Zeeman/ATLAS9 LTE synthetic spectra to estimate the effective temperatures, microturbulent velocities, and the abundances of some elements of both components, as well as the light-ratio of the system. We then fit the least-square deconvolved $I$ profiles to determine the radial and projected rotational velocities of both stars. We then analysed the shape and evolution of the LSD $V$ profiles using the oblique rotator model to characterise the magnetic fields of both stars. We confirm the Ap nature of the primary, previously reported in the literature, and find that the secondary displays spectral characteristics typical of an Am star. While a magnetic field is clearly detected in the lines of the primary, no magnetic field is detected in the secondary, in any of our observation. If a dipolar field were present at the surface of the Am star, its polar strength must be below 40 G. The faint variability observed in the Stokes $V$ profiles of the Ap star allowed us to propose a rotation period of $6.84_{-0.39}^{+0.61}$ d, close to the orbital period ($\sim$6.82 d), suggesting that the star is synchronised with its orbit. By fitting the variability of the $V$ profiles, we propose that the Ap component hosts a dipolar field inclined with the rotation axis at an angle $\beta=156\pm17$ $^{\circ}$ and a polar strength $B_{\rm d}=65 \pm 20$ G. The field strength is the weakest known for an Ap star.Comment: 13 pages, 12 figures, accepted for publication in Astronomy & Astrophysic