Is HIV-1 RNA dimerization a prerequisite for packaging? Yes, no, probably?

During virus assembly, all retroviruses specifically encapsidate two copies of full-length viral genomic RNA in the form of a non-covalently linked RNA dimer. The absolute conservation of this unique genome structure within the Retroviridae family is strong evidence that a dimerized genome is of critical importance to the viral life cycle. An obvious hypothesis is that retroviruses have evolved to preferentially package two copies of genomic RNA, and that dimerization ensures the proper packaging specificity for such a genome. However, this implies that dimerization must be a prerequisite for genome encapsidation, a notion that has been debated for many years. In this article, we review retroviral RNA dimerization and packaging, highlighting the research that has attempted to dissect the intricate relationship between these two processes in the context of HIV-1, and discuss the therapeutic potential of these putative antiretroviral targets

Insights into the Nature of Synergistic Effects in Proton-Conducting 4,4−1H,1H-Bitriazole-Poly(ethylene oxide) Composites

A nitrogen-containing heterocycle (NCH), 4,4-1H-1H-bi-1,2,3-triazole (bitriazole), capable of mimicking the hydrogen bonding of water in the solid state is synthesized and its ability to conduct protons in the presence of poly(ethylene oxides) under anhydrous conditions is investigated. Bitriazole is shown to have sufficient thermal and electrochemical stability for fuel cell applications. The composites formed between bitriazole and poly(ethylene oxides) give proton conductivities that can be described by the Vogel−Tamman−Fulcher (VTF) equation. These characteristics suggest coupling between polymer segmental motion and ion transport. The bitriazole N-H proton is shown to be the source of conductivity, and bitriazole and poly(ethylene oxides) function synergistically through specific intermolecular interactions and polymer-induced segmental motion to create a pathway for proton transport via structural diffusion

A Dynamin-3 Spliced Variant Modulates the Actin/Cortactin-Dependent Morphogenesis of Dendritic Spines

Immature dendrites extend many actin-rich filopodial structures that can be replaced by synapse-containing dendritic spines as the neuron matures. The large GTPase dynamin-3 (Dyn3) is a component of the postsynapse in hippocampal neurons but its function is undefined. Here, we demonstrate that a specific Dyn3 variant (Dyn3baa) promotes the formation of immature dendritic filopodia in cultured neurons. This effect is dependent upon Dyn3 GTPase activity and a direct interaction with the F-actin-binding protein cortactin. Consistent with these findings, Dyn3baa binds to cortactin with a 200% higher affinity than Dyn3aaa, a near identical isoform that does not induce dendritic filopodia when expressed in cultured neurons. Finally, levels of Dyn3baa-encoding mRNA are tightly regulated during neuronal maturation and are markedly upregulated during synaptogenesis. Together, these findings provide the first evidence that an enhanced interaction between a specific Dyn3 splice variant and cortactin modulate actin-membrane dynamics in developing neurons to regulate the morphogenesis of dendritic spines. Supplementary material available online at http://jcs.biologists.org/cgi/content/full/118/6/1279/DC

Mechanical properties of connected carbon nanorings via molecular dynamics simulation

Stable, carbon nanotori can be constructed from nanotubes. In theory, such rings could be used to fabricate networks that are extremely flexible and offer a high strength-to-density ratio. As a first step towards realizing such nanochains and nanomaile, the mechanical properties of connected carbon nanorings were investigated via molecular dynamics simulation. The Young's modulus, extensibility and tensile stength of nanorings were estimated under conditions that idealize the constraints of nanochains and nanomaile. The results indicate nanorings are stable under large tensile deformation. The calculated Young's modulus of nanorings was found increase with deformation from 19.43 GPa to 121.94 GPa (without any side constraints) and from 124.98 GPa to 1.56 TPa (with side constraints). The tensile strength of unconstrained and constrained nanorings is estimated to be 5.72 and 8.522 GPa, respectively. The maximum strain is approximately 39% (nanochains) and 25.2% (nanomaile), and these deformations are completely reversible

Remark on Charm Quark Fragmentation to D∗∗D^{**} Mesons

The observed $D^{**}$ mesons have $c\bar q$ flavor quantum numbers and spin-parity of the light degrees of freedom $s_\ell^{\pi_{\ell}} = 3/2^+$. In the $m_c \rightarrow \infty$ limit the spin of the charm quark is conserved and the $c \rightarrow D^{**}$ fragmentation process is characterized by the probability for the charm quark to fragment to a $D^{**}$ meson with a given helicity for the light degrees of freedom. We consider the calculated $b \rightarrow B_c^{**}$ fragmentation functions in the limit $m_c/m_b \rightarrow 0$ as a qualitative model for the $c \rightarrow D^{**}$ fragmentation functions. We find that in this model charm quark fragmentation to $s_\ell^{\pi_{\ell}} = 3/2^+$ light degrees of freedom with helicities $\pm 1/2$ is favored over fragmentation to $s_\ell^{\pi_{\ell}} = 3/2^+$ light degrees of freedom with helicities $\pm 3/2$.Comment: 6 pages, CALT-68-192

A Story of Innovation: The Alexian Village Health Center, Milwaukee

This monograph is the result of a study at the Alexian Village of Milwaukee, Wisconsin, a continuing care retirement community. It shows how the quality of its Health Center residents\u27 lives were improved through manipulation of the physical environment. This monograph set out to achieve four major goals: 1) to show the relationships between organizational, social, and environmental factors; 2) to demonstrate the role of the physical environment as a therapeutic tool; 3) to demonstrate the importance of the preparatory process in creating a facility for older persons; 4) to demonstrate the rewards of ongoing analysis and evaluation.https://dc.uwm.edu/caupr_mono/1018/thumbnail.jp