Ubiquitin is covalently attached to the p6Gag proteins of human immunodeficiency virus type 1 and simian immunodeficiency virus and to the p12Gag protein of Moloney murine leukemia virus

Host proteins are incorporated into retroviral virions during assembly and budding. We have examined three retroviruses, human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus (SIV), and Moloney murine leukemia virus (Mo-MuLV), for the presence of ubiquitin inside each of these virions. After a protease treatment to remove exterior viral as well as contaminating cellular proteins, the proteins remaining inside the virion were analyzed. The results presented here show that all three virions incorporate ubiquitin molecules at approximately 10% of the level of Gag found in virions. In addition to free ubiquitin, covalent ubiquitin-Gag complexes were detected, isolated, and characterized from all three viruses. Our immunoblot and protein sequencing results on treated virions showed that approximately 2% of either HIV-1 or SIV p6Gag was covalently attached to a single ubiquitin molecule inside the respective virions and that approximately 2 to 5% of the p12Gag in Mo-MuLV virions was monoubiquitinated. These results show that ubiquitination of Gag is conserved among these retroviruses and occurs in the p6Gag portion of the Gag polyprotein, a region that is likely to be involved in assembly and budding.     

Flow and heat transfer of natural convection around an upward‐facing horizontal plate with a vertical plate at the edge

Natural convective flows around an upward‐facing horizontal heated plate with a vertical plate at the edge were investigated experimentally. Of particular concern were the influences of the vertical plate on the fluid flow and the heat transfer of the horizontal plate. The flow and temperature fields adjacent to the horizontal plate were visualized with dye and a liquid‐crystal thermometry. The results show that the vertical plate obstructs the flow from the top of the vertical plate, while the flow from the open edge of the horizontal plate covers the whole horizontal surface when the height of the vertical plate exceed H/W = 0.14 for adiabatic vertical plate and H/W = 0.1 for the heated vertical plate. The local heat‐transfer‐coefficients of the horizontal plate were also measured. It was found that the vertical adiabatic plates deteriorate the heat transfer, while the heated vertical plates enhance the heat transfer from the horizontal plates. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 527–539, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20033     

The influence of oxidation-sirtl etch condition on the stacking fault generation in (111) silicon wafers

The successive oxidation-Sirtl etch technique has been investigated to evaluate the perfection of silicon crystals by detecting extrinsic stacking faults produced during oxidation. Experiments were performed in (111) epitaxial wafers. Measured densities of stacking faults were found to epend on the conditions of thermal oxidation, and stacking fault densities were a maximum at an oxidation temperature of around 1100°C. The stacking fault densities were reduced appreciably when epitaxial wafers were chemically etched to remove several tens of microns prior to the test. The generation of stacking faults is thought to occur by heterogeneous nucleation due to a very small amount of unidentified impurity found in epitaxial crystals.     

Targeting Delivery of Protein Drugs by Chemical Modification

In vivo disposition profiles of protein derivatives having various chemical modifications were systematically compared in mice based on the clearance concept. Proteins such as bovine γ-globulin (IgG), bovine serum albumin (BSA), superoxide dismutase (SOD), soybean trypsin inhibitor (STI), and chicken egg white lysozyme (LZM) were l)conjugated with polyethylene glycol (PEG) and dextran to increase molecular size, 2) conjugated with carboxymethyl-dextran (CMD) and diethylaminoethyl-dextran (DEAED) or coupled with diaminohexane or succinic acid to introduce electric charges, and 3) modified with galactose (Gal) and mannose (Man) moieties to bestow an affinity for receptor-mediated endocytosis in cells. By applying these modifications, in vivo disposition features of proteins were extensively changed; i.e., in the case of SOD, conjugation with CMD and PEG prolonged its circulation half-life more than 100 times but cationized SOD showed remarkable accumulation on the surface of the liver tissue. In addition, specific targeting to the parenchymal cells of the liver was demonstrated in Gal-SOD, while, Man-SOD and succinylated SOD showed rapid uptake by the nonparenchymal cells. These results revealed the utility of chemical modification for controlling in vivo disposition of proteins.     

Electrical Spin Injection in Perpendicular Magnetized FePt/MgO/GaAs Heterostructures at Room Temperature

We report zero-magnetic-field spin injection from FePt into GaAs at room temperature using FePt/MgO/GaAs-based light-emitting diode heterostructures. Experiments are performed on two samples with different compositions; Fe₆₁Pt₃₉ and Fe₅₇Pt₄₃. The polarizations of injected electrons at 0 T for these two samples are at least 1.5% and 3.3%, respectively. The higher zero-magnetic-field injected spin polarization is considered to be due to the better remanent perpendicular magnetization of the FePt layer in the sample with Fe₅₇Pt₄₃.     

Correlation between 1/f noise and semiconductor laser degradation

The origin of the increase in residual spectral linewidth during device degradation is experimentally and theoretically clarified in a multiple quantum well (MQW) distributed feedback (DFB) laser. Non-radiative recombination current increases during device degradation and causes 1/f noise to increase. This current 1/f noise is the origin of the increase in the residual spectral linewidth. Through these degradation behaviours, a model showing a correlation between 1/f noise and the semiconductor laser degradation is proposed.