Absence Of Ge Research Articles

Anterograde Spread of Herpes Simplex Virus Type 1 Requires Glycoprotein E and Glycoprotein I but Not Us9

Anterograde neuronal spread (i.e., spread from the neuron cell body toward the axon terminus) is a critical component of the alphaherpesvirus life cycle. Three viral proteins, gE, gI, and Us9, have been implicated in alphaherpesvirus anterograde spread in several animal models and neuron culture systems. We sought to better define the roles of gE, gI, and Us9 in herpes simplex virus type 1 (HSV-1) anterograde spread using a compartmentalized primary neuron culture system. We found that no anterograde spread occurred in the absence of gE or gI, indicating that these proteins are essential for HSV-1 anterograde spread. However, we did detect anterograde spread in the absence of Us9 using two independent Us9-deleted viruses. We confirmed the Us9 finding in different murine models of neuronal spread. We examined viral transport into the optic nerve and spread to the brain after retinal infection; the production of zosteriform disease after flank inoculation; and viral spread to the spinal cord after flank inoculation. In all models, anterograde spread occurred in the absence of Us9, although in some cases at reduced levels. This finding contrasts with gE- and gI-deleted viruses, which displayed no anterograde spread in any animal model. Thus, gE and gI are essential for HSV-1 anterograde spread, while Us9 is dispensable.

The Herpes Simplex Virus Type 1 Glycoprotein D (gD) Cytoplasmic Terminus and Full-Length gE Are Not Essential and Do Not Function in a Redundant Manner for Cytoplasmic Virion Envelopment and Egress

Herpes simplex virus type 1 (HSV-1) acquires its final envelope by budding into cytoplasmic vesicles thought to be derived from trans-Golgi network membranes. This process is facilitated by interactions among the carboxyl termini of viral glycoproteins and tegument proteins. To directly investigate the relative importance of the carboxyl terminus of glycoprotein D (gD) in the presence or absence of gE, a recombinant virus (gDDeltact) was constructed to specify a truncated gD lacking the carboxy-terminal 29 amino acids. Furthermore, two additional recombinant viruses were constructed by mutating from ATG to CTG the initiation codons of gE (gEctg) or both gE and gM (gEctg+gMctg), causing lack of expression of gE or both gE and gM, respectively. A fourth mutant virus was constructed to specify the gEctg+gDDeltact mutations. The replication properties of these viruses were compared to those of a newly constructed recombinant virus unable to express UL20 due to alteration of the two initiation codons of UL20 (UL20ctgctg). All recombinant viruses were constructed by using the double-Red, site-directed mutagenesis system implemented on the HSV-1(F) genome cloned into a bacterial artificial chromosome. The gEctg, gEctg+gMctg, gDDeltact, and gEctg+gDDeltact viruses produced viral plaques on African monkey kidney cells (Vero), as well as other cells, that were on average approximately 30 to 50% smaller than those produced by the wild-type virus HSV-1(F). In contrast, the UL20ctgctg virus produced very small plaques containing three to five cells, as reported previously for the DeltaUL20 virus lacking the entire UL20 gene. Viral replication kinetics of intracellular and extracellular viruses revealed that all recombinant viruses produced viral titers similar to those produced by the wild-type HSV-1(F) virus intracellularly and extracellularly at late times postinfection, with the exception of the UL20ctgctg and DeltaUL20 viruses, which replicated more than two-and-a-half logs less efficiently than HSV-1(F). Electron microscopy confirmed that all viruses, regardless of their different gene mutations, efficiently produced enveloped virions within infected cells, with the exception of the UL20ctgctg and DeltaUL20 viruses, which accumulated high levels of unenveloped virions in the cytoplasm. These results show that the carboxyl terminus of gD and the full-length gE, either alone or in a redundant manner, are not essential in cytoplasmic virion envelopment and egress from infected cells. Similarly, gM and gE do not function alone or in a redundant manner in cytoplasmic envelopment and virion egress, confirming previous findings.

Synthesis and Monte Carlo Structure Determination of SSZ-77: A New Zeolite Topology

A new molecular sieve topology has been determined from a multistage Monte Carlo computer simulation procedure using the program ZEFSAII. The material, SSZ-77, consists of alternating layers present in the RUT and AST topologies, and intergrowths may be possible in the way that this material grows. The product first arose from a synthesis where it appears that the degradation of the quaternary ammonium structure directing agent (SDA) produced the viable organo-guest molecule in the structure formation. The synthesis requires the use of Ge as well as Si as lattice components. In the absence of Ge, only RUT forms. An additional study was carried out to determine the suitable size of guest molecules in a series spanning trimethylamine to tetraethylammonium in the presence of benzyltrimethylammonium. It is found from NMR investigations that none of the larger molecules are occluded within the cages of the SSZ-77 structure, and that the primary occluded species is trimethylamine or tetramethylammonium.

Influence of a Si layer intercalated between Si0.75Ge0.25 and Ni on the behavior of the resulting NiSi1−uGeu film

The interaction of Ni films with epitaxially grown Si-capped and not capped Si0.75Ge0.25 layers on Si(100) at 500°C leads to the formation of NiSi1−uGeu films as a bilayer NiSi on NiSi0.75Ge0.25 with a rather clear compositional boundary. In the absence of a Si cap at the surface, NiSi0.75Ge0.25 is formed on NiSi. Epitaxy of NiSi on NiSi0.75Ge0.25, and vice versa, occurs across the compositional boundary. The crystallographic orientation of the NiSi1−uGeu films is strongly affected by the initial layer thicknesses and the layer sequence. Without a Si cap, the NiSi1−uGeu films show an increased fiber texture with increasing Si0.75Ge0.25 thickness. In the presence of a Si cap, on the other hand, the texture collapses into a random orientation already for thin caps. Rapid diffusion of Ge at 500°C results in the presence of some Ge at the NiSi∕Si interface for a NiSi0.75Ge0.25∕NiSi∕Si structure. This diffusion is accompanied by an increased roughness at the NiSi∕Si interface, as compared to the quite flat NiSi∕Si interface in the absence of Ge. For thin Si caps, severe interface roughening with thick NiSi0.75Ge0.25 grains protruding deeply into the remaining Si0.75Ge0.25 is observed.

Biosynthesis of glycoproteins E and I of feline herpesvirus: gE-gI interaction is required for intracellular transport.

The biosynthesis of glycoproteins E and I of feline herpesvirus was studied by using the vaccinia virus vTF7-3 expression system. gE and gI were synthesized as N-glycosylated, endoglycosidase H (EndoH)-sensitive precursors with Mrs of 83,000 and 67,000, respectively. When coexpressed, gE and gI formed sodium dodecyl sulfate-sensitive hetero-oligomeric complexes that were readily transported from the endoplasmic reticulum (ER). Concomitantly, the glycoproteins acquired extensive posttranslational modifications, including O glycosylation, leading to an increase in their apparent molecular weights to 95,000 and 80,000 to 100,000 for gE and gI, respectively. In the absence of gE, most gI remained EndoH sensitive. Only a minor population became EndoH resistant, but these molecules were processed aberrantly as indicated by their Mrs (100,000 to 120,000). By immunofluorescence microscopy, gI was detected primarily in the ER but also at the plasma membrane. gE, when expressed by itself, remained EndoH sensitive and was found only in the ER and the nuclear envelope. These results were corroborated by studying the biosynthesis of gE in feline herpesvirus (FHV)-infected cells. In cells infected with wild-type FHV, gE acquired the same co- and posttranslational modifications as during vTF7-3-driven expression. However, an FHV mutant lacking gI failed to produce mature gE. We conclude that gE is retained in the ER, presumably by associating with molecular chaperones, and becomes transport competent only when in a complex with gI.

The effects of Ge content on the microstructure and specific contact resistance of solid-state NiAuGe/ZrB2/Au ohmic contacts to n-InGaAs

The Ge thickness, x, of NiAuGe(5 nm/45 nm/xnm)/ZrB2(50 nm)/Au(20 nm) ohmic contacts to n-lnGaAs was varied between 0 and 20 nm. The microstructures of these contacts, after annealing at 270°C, were investigated using transmission electron microscopy (TEM) and correlated with the respective specific contact resistances. In the absence of Ge, a Ni-Ga-As phase was formed at the metal-semiconductor interface and the specific contact resistance was high (0.63 Ωmm). When thicknesses of x = 10 nm or x = 15 nm of Ge were added, Ni-Ge-As phases were observed, but they were replaced by AuGeAs and NiGe when x = 20 nm. The specific contact resistance was a minimum (0.11 Ωmm) for this composition. Ge was clearly beneficial for ohmic-contact formation. The low-temperature I–V characteristics of the contact containing the largest amount of Ge (that is, x = 20 nm) indicated that electron tunnelling through degenerately-Ge-doped regions was not the dominant ohmic mechanism in these contacts.

Oxygen removal from Si via reaction with adsorbed Ge

Silicon surface optimization prior to film growth is central to the fields of chemical vapor deposition and molecular beam epitaxy. We have examined a method for low-temperature in situ cleaning of the Si (100) surfaces utilizing a submonolayer coverage of germanium. Synchrotron excited x-ray photoemission data indicate that Ge atoms arriving at a Si (100) surface can break silicon–oxygen bonds, thereby producing new chemical species which sublimate at 625 °C. In the absence of Ge, the observed silicon oxide species were stable at temperatures well in excess of 750 °C. These results are used to investigate the mechanisms by which adsorbed Ge can be used to produce oxide-free Si (100) surfaces at 625 °C.

High pressure studies of Ge using synchrotron radiation

Compressibility studies have been carried out on Ge–I (diamond-cubic structure) to 12.0 GPa; the results are in very good agreement with previous work. We confirm the recent report of a substantial lowering of the Ge I–II transition pressure in a nonhydrostatic pressure environment. We observe the Ge–II (200)-peak at 10.5±0.2 GPa in a more hydrostatic pressure environment and as low as 6.7 GPa when shear stresses are present. On release of pressure from above 11 GPa, we find that Ge–II converts predominantly into Ge–III when Ge–I and shear stresses are present and completely into Ge–III in the absence of Ge–I in a more hydrostatic pressure environment. This is contrary to what had been previously presumed.