Migration Of Oligomers Research Articles

Persistent reovirus infections of L cells select mutations in viral attachment protein sigma1 that alter oligomer stability.

During maintenance of L-cell cultures persistently infected with reovirus, mutations are selected in viruses and cells. Cells cured of persistent infection support growth of viruses isolated from persistently infected cultures (PI viruses) significantly better than that of wild-type (wt) viruses. In a previous study, the capacity of PI virus strain L/C to grow better than wt strain type 1 Lang (T1L) in cured cells was mapped genetically to the S1 gene (R. S. Kauffman, R. Ahmed, and B. N. Fields, Virology 131:79-87, 1983), which encodes viral attachment protein sigma1. To investigate mechanisms by which mutations in S1 confer growth of PI viruses in cured cells, we determined the S1 gene nucleotide sequences of L/C virus and six additional PI viruses isolated from independent persistently infected L-cell cultures. The S1 sequences of these viruses contained from one to three mutations, and with the exception of PI 2A1 mutations in each S1 gene resulted in changes in the deduced amino acid sequence of sigma1 protein. Using electrophoresis conditions that favor migration of sigma1 oligomers, we found that sigma1 proteins of L/C, PI 1A1, PI 3-1, and PI 5-1 migrated as monomers, whereas sigma1 proteins of wt reovirus and PI 2A1 migrated as oligomers. These findings suggest that mutations in sigma1 protein affecting stability of sigma1 oligomers are important for the capacity of PI viruses to infect mutant cells selected during persistent infection. Since no mutation was found in the deduced amino acid sequence of PI 2A1 sigma1 protein, we used T1L X PI 2A1 reassortant viruses to identify viral genes associated with the capacity of this PI virus to grow better than wt in cured cells. The capacity of PI 2A1 to grow better than T1L in cured cells was mapped to the S4 gene, which encodes outer-capsid protein sigma3. This finding suggests that in some cases, mutations in sigma3 protein in the absence of sigma1 mutations confer growth of PI viruses in mutant cells. To confirm the importance of the S1 gene in PI virus growth in cured cells, we used T1L X PI 3-1 reassortant viruses to genetically map the capacity of this PI virus to grow better than wt in cured cells. In contrast to our results using PI 2A1, we found that growth of PI 3-1 in cured cells was determined by the sigma1-encoding S1 gene. Given that the sigma1 and sigma3 proteins play important roles in reovirus disassembly, findings made in this study suggest that stability of the viral outer capsid is an important determinant of the capacity of reoviruses to adapt to host cells during persistent infection.

Anomalous gel migration of DNA oligomers containing multiple conformational junctions

We have previously shown that a short 16 base pair DNA oligomer can accommodate a B-Z conformational junction [Sheardy, R. D., & Winkle, S. A. (1989) Biochemistry 28, 720-725]. Results from 1H NMR studies indicated that only three base pairs were involved in the junction and that one of these base pairs was highly distorted. Being interested in the nature of this distortion, we constructed DNA oligomers which have the potential to contain multiple B-Z junctions for polyacrylamide electrophoretic studies. We report that the mobilities displayed by these molecules through acrylamide gels in the absence and presence of cobalt suggest that these molecules run shorter than they actually are. This anomalous migration may be due to structural/dynamic properties of the DNA helix manifested by the periodic distortions of the potential B-Z junctions.

Migration of Poly(ethylene terephthalate) (PET) Oligomers from PET Plastics into Foods during Microwave and Conventional Cooking and into Bottled Beverages

The migration of total levels of poly(ethylene terephthalate) (PET) oligomers into a diverse range of foods has been determined using an analytical approach that involves hydrolysis of oligomers to terephthalic acid, methylation, and analysis as dimethyl terephthalate by stable isotope dilution GC/MS. Aspects of use of PET materials examined in this study include roasting bags, PET trays (for conventional and microwave oven use), and “susceptor pads” for microwave browning applications. Total levels of migration of PET oligomers were found to range from 0.02 to 2.73 mg/kg depending on the foodstuff and the temperature attained during cooking. On repeated-use of PET trays for heating olive oil there was a decline in migration of oligomers from the first to second and subsequent uses of the container. Migration of oligomers was found to occur at only very low levels from PET bottles into alcoholic and carbonated beverages.

Plasma‐substrate interaction: Effect of volatile oligomers in silicone rubber on plasma polymerization of fluorine‐containing monomers

AbstractThe cause of the conspicous Si content consistently observed on plasma polymers deposited on silicone rubber was investigated in this study. Plasma polymers of tetrafluoroethylene and of hexafluoroethane were deposited on the inside surface of Silastic tubings with and without oligomers by using a semicontinuous plasma polymerization reactor. This tube coating reactor is unique in the sense that the only surface which interacts with the plasma is the substrate surface (i.e., inside wall of tubing) and that plasma polymerization occurs in a very small volume of 3.3‐mm‐I.D. and 2‐cm‐long section of tubing at any given time. These two factors render the reactor a suitable system for the investigation of plasma‐substrate surface interaction. Silastic tubings free of oligomers were prepared by extracting the tubings as received with distilled n‐hexane for 3 h which yielded a 3% weight loss. It was found that the conspicuous Si content noted previously was not occasioned by the migration of oligomers through the plasma polymers but was caused by the redeposition of plasma copolymers formed from a mixture of the feed‐in monomer and the silicon‐containing volatile components evolved from the silicone rubber when exposed to the plasma. The presence of Si‐containing compounds in the plasma evidently interfered with the plasma polymerization of tetrafluoroethylene and hexafluoroethane. Without volatile oligomers (the extracted samples), ESCA analysis indicated that the plasma polymers contained large amounts of CF3, CF2, and CF moieties, just like most typical plasma polymers of these monomers deposited on nonreactive substrates. With the presence of volatile oligomers, the fluorine content decreased drastically and a significant increase of oxygen‐containing and silicon‐containing moieties was observed. The influence of the volatile oligomers in the substrate on the balance between ablation and polymerization in plasma polymerization and its energy input level dependence (manifested by W/FM) were studied as well. The results were also discussed in relation to the bicyclic rapid step‐growth polymerization mechanism.