Automated acquisition and analysis of data from the photoelectric scanner of the model E analytical ultracentrifuge.

To facilitate sedimentation equilibrium experiments on the model E analytical ultracentrifuge, a method for automated data acquisition from the photoelectric scanner system has been developed. The instrumentation described is relatively simple to install and convenient to operate. Direct access to computer analysis of data is thus achieved. Application is made to the study of a protein, allophycocyanin. Results over a range of pH and protein concentrations confirm that an α₃β₃ structure is stable in aqueous media.     

Incongruent gene trees, complex evolutionary processes, and the phylogeny of a group of North American minnows (Hybognathus Agassiz 1855)

Hybognathus is a putatively monophyletic group of North American minnows containing seven extant species. Although much is known about the taxonomy, biology, and life history of Hybognathus species, their phylogenetic relations with each other remain unclear. We address this problem with partial sequences of mitochondrial cytochrome-b, 16S rRNA, and ND4 mtDNA genes and nuclear growth hormone (GH) and S7 introns from representatives of all Hybognathus species and four outgroup taxa. Phylogenetic analyses of these data corroborated previous studies on the monophyly of seven recognized species of Hybognathus, and indicated weak support for monophyly of the genus. Topological tests, however, revealed significant (all P < 0.001) conflict among molecular data sets. Ad hoc removal of taxa from topologies and subsequent testing indicated that incongruence was localized to two specific ingroup taxa (H. hayi and H. regius) and suggested that the conflict is a function of underlying processes that have generated the observed phylogenetic patterns. Hybridization (ancestral), which is commonplace in cyprinids, may best explain topological disagreements among datasets; however, retention of ancestral polymorphism and natural selection remain as alternative hypotheses. Our results highlight methodological and topological problems associated with estimating interspecific phylogenies from multiple genes.     

Orthopoxvirus gene expression in Xenopus laevis oocytes: a component of the virion is needed for late gene expression.

We have examined the feasibility of using Xenopus laevis oocytes microinjected with rabbit poxvirus as a system to study poxvirus gene expression. The injection of either intact virus or subviral cores resulted in accurate synthesis of viral proteins. This expression was dependent on the multiplicity of injected virus, with the optimal injected dose being equivalent to approximately 300 PFU per oocyte. Extensive viral gene expression including late viral protein synthesis was observed when intact virions were microinjected into the oocyte. However, the injection of subviral cores resulted in only early protein synthesis. When oocytes were injected with a mixture of subviral cores and the nonionic detergent-soluble fraction was removed from virus during the preparation of cores, both early and late viral proteins were synthesized. Therefore, the detergent-soluble fraction appears to contain a factor(s) required for the transition from early to late gene expression.