Thermal Expansion of Composite Resins and Sealants

Linear thermal coefficients of expansion (α) of seven commercial composite resins and four pit and fissure sealants were determined between 0 and 60°C on a thermomechanical analyzer. The thermal expansion curves obtained were nonlinear. Values of α ranged from 26.5 to 39.6 × 10-6 °/C for the composite and from 70.9 to 93.7 x 10-6/°C for the sealants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67284/2/10.1177_00220345790580020701.pd

Comparative genomics of plant-asssociated Pseudomonas spp.: Insights into diversity and inheritance of traits involved in multitrophic interactions

We provide here a comparative genome analysis of ten strains within the Pseudomonas fluorescens group including seven new genomic sequences. These strains exhibit a diverse spectrum of traits involved in biological control and other multitrophic interactions with plants, microbes, and insects. Multilocus sequence analysis placed the strains in three sub-clades, which was reinforced by high levels of synteny, size of core genomes, and relatedness of orthologous genes between strains within a sub-clade. The heterogeneity of the P. fluorescens group was reflected in the large size of its pan-genome, which makes up approximately 54% of the pan-genome of the genus as a whole, and a core genome representing only 45–52% of the genome of any individual strain. We discovered genes for traits that were not known previously in the strains, including genes for the biosynthesis of the siderophores achromobactin and pseudomonine and the antibiotic 2-hexyl-5-propyl-alkylresorcinol; novel bacteriocins; type II, III, and VI secretion systems; and insect toxins. Certain gene clusters, such as those for two type III secretion systems, are present only in specific sub-clades, suggesting vertical inheritance. Almost all of the genes associated with multitrophic interactions map to genomic regions present in only a subset of the strains or unique to a specific strain. To explore the evolutionary origin of these genes, we mapped their distributions relative to the locations of mobile genetic elements and repetitive extragenic palindromic (REP) elements in each genome. The mobile genetic elements and many strain-specific genes fall into regions devoid of REP elements (i.e., REP deserts) and regions displaying atypical tri-nucleotide composition, possibly indicating relatively recent acquisition of these loci. Collectively, the results of this study highlight the enormous heterogeneity of the P. fluorescens group and the importance of the variable genome in tailoring individual strains to their specific lifestyles and functional repertoir

Nanoparticles featuring amino acid-functionalized side chains as DNA receptors

A family of nanoparticles has been fabricated featuring cationic amino acid-based side chains. This controlled surface modification provides a tool to investigate the effect of various non-covalent interactions at the nanoparticle-DNA interface. The binding affinities of these nanoparticles towards DNA were determined using fluorescence, exhibiting more than threefold modulation in binding a 37-mer DNA strand. The secondary structure of the DNA strand was distorted upon nanoparticle binding, with the extent of distortion dependent on the structure of amino acid side chain