A large deletion in the matrix domain of the human immunodeficiency virus gag gene redirects virus particle assembly from the plasma membrane to the endoplasmic reticulum.

Morphogenesis of retroviruses involves assembly of the structural Gag and Gag-Pol polyproteins with subsequent budding of the virus particle from the plasma membrane and proteolytic cleavage by the viral proteinase. The matrix (MA) domain, representing the N-terminal segment of Gag, plays a critical role in this process. We constructed an in-frame deletion in the MA coding region (lacking codons 16 to 99) of the human immunodeficiency virus (HIV) type 1 gag gene. Following transient transfection of the complete proviral DNA carrying the deletion, the mutant polyprotein was synthesized and proteolytically processed like the wild-type polyprotein. However, release of virus particles was reduced approximately 10-fold. The extracellular particles that were released did not contain viral glycoproteins and were noninfectious. Electron micrographs revealed budding of virus particles into the endoplasmic reticulum (ER) of transfected cells and large numbers of particles within the ER. These particles were all immature and morphologically indistinguishable from intracisternal A-type particles, a class of murine endogenous retrovirus elements. Budding structures at the plasma membrane were rarely seen and only a few extracellular particles were observed, but in contrast to those in the ER, these particles had the morphology of mature particles, similar to that of wild-type HIV, except for the lack of surface projections

Detailed investigation of the propagation rate of urethane acrylates

Temperature dependent propagation rate coefficients, kp, are determined for four acrylate monomers containing a carbamate moiety via the pulsed laser polymerization-size exclusion chromatography (PLP-SEC) technique. Therefore, the Mark-Houwink-Kuhn-Sakurada coefficients K and a of the respective polymers were additionally determined via triple-detection SEC. The monomers under investigation were synthesized from hydroxyethyl acrylate, hydroxyl(iso)propyl acrylate as well as phenyl isocyanate and hexyl isocyanate, respectively, in all four possible combinations. For 2-(phenylcarbamoyloxy)ethyl acrylate (PhCEA) an activation energy of 14.3 kJ mol-1 and a frequency factor of A = 1.2 × 107 L·mol-1 s-1 are obtained for kp. The MHKS parameters for poly(PhCEA) are K = 8.3 × 10-5 dL g-1 and a = 0.677. For 2-(phenylcarbamoyloxy)isopropyl acrylate (PhCPA) an activation energy of 14.2 kJ mol-1 and a frequency factor of A = 4.9 × 10 6 L mol-1 s-1 are found for kp and the MHKS parameters for poly(PhCPA) read K = 10.3 × 10-5 dL g-1 and a = 0.657. The activation parameters of kp of 2-(hexylcarbamoyloxy)ethyl acrylate (HCEA) are EA = 13.3 kJ mol -1 and A = 6.6 × 106 L mol-1 s -1 with K = 36.0 × 10-5 dL g-1 and a = 0.552 for poly(HCEA). For 2-(hexylcarbamoyloxy)isopropyl acrylate (HCPA) E A is 14.1 kJ mol-1 and A = 6.6 × 106 L mol-1 s-1 with K = 26.0 × 10-5 dL g -1 and a = 0.587 for poly(HCPA). All rate measurements were performed in 1 M solutions in butyl acetate. The fast propagating nature and reduced activation energy of the monomers may be understood on the basis of the increased nucleophilicity that is induced by the carbamate functionality present in all monomers. Rate-increasing effects from solvent polarity and/or from H-bonding can, however, not be excluded and might also contribute to the observed high propagation rates. © 2010 The Royal Society of Chemistry