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A new perturbation theory which is reliable over a wide fluid region is presented. The new theory reduces to the theory of Weeks, Chandler, and Anderson at densities near or below the triple point density of a simple fluid but it can also accurately predict thermodynamic properties at higher densities near the freezing line of the fluid. This is done by employing an optimized reference potential whose repulsive range decreases with increase in density. Thermodynamic properties for Lennard-Jones, exponential-6, and inverse nth-power (n=12, 9, 6, and 4) potentials have been calculated from the new theory. Comparison of the calculated data with available Monte Carlo simulations and additional simulations carried out in this work shows that the theory gives excellent thermodynamic results for these systems. The present theory also gives a physically reasonable hard-sphere diameter over the entire fluid range.

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Up to 6 ؋ 10 7 PFU of infectious virions of the double-stranded DNA bacteriophage 29 per ml were assembled in vitro, with 11 proteins derived from cloned genes and nucleic acids synthesized separately. The genomic DNA-gp3 protein conjugate was efficiently packaged into a purified recombinant procapsid with the aid of a small viral RNA (pRNA) transcript, a DNA-packaging ATPase (gp16), and ATP. The DNA-filled capsids were subsequently converted into infectious virions after the addition of four more recombinant proteins for neck and tail assembly. Electron microscopy and genome restriction mapping confirmed the identity of the infectious 29 virions synthesized in this system. A nonstructural protein, gp13, was indispensable for the assembly of infectious virions. The overproduced tail protein gp9 was present in solution in mostly dimeric form and was purified to homogeneity. The purified gp9 was biologically active for in vitro 29 assembly. Higher-order concentration dependence of in vitro 29 assembly on gp9 suggests that a complete tail did not form before attaching to the DNA-filled capsid, a result contrary to earlier findings for phages T4 and. The work described here constitutes an extremely sensitive assay system for the analysis of components in 29 assembly and dissection of functional domains of structural components, enzymes, and pRNA (C.-S. Lee and P. Guo, Virology 202:1039-1042, 1995). Efficient packaging of foreign DNA in vitro and synthesis of viral particles from recombinant proteins facilitate the development of 29 as an in vivo gene delivery system. The finding that purified tail protein was able to incorporate into infectious virions might allow the construction of chimeric 29 carrying a tail fused to ligands for specific receptor of human cells.