BACKGROUND Direct-acting antiviral (DAA) resistance-associated substitutions (RASs) can jeopardize the effectiveness of DAAs in patients with hepatitis C virus (HCV). The selection pressure by pegylated-interferon (Peg-IFN) plus ribavirin (P/R) treatment may enhance HCV genome variation. However, whether P/R treatment alters the rate of change of RASs is still unclear. MATERIALS AND METHODS W...

Although native chemical ligation (NCL) and related chemoselective ligation approaches provide an elegant method to stitch together unprotected peptides, the handling and purification of insoluble and aggregation-prone peptides and assembly intermediates create a bottleneck to routinely preparing large proteins by completely synthetic means. In this work, we introduce a new general tool, Fmoc-D...

In Salmonella enterica serovar Typhimurium, Mg2+ limitation induces transcription of the mgtA Mg2+ transport gene, but the mechanism involved is unclear. The 5' leader of the mgtA mRNA contains a 17-codon, proline-rich ORF, mgtL, whose translation regulates the transcription of mgtA [Park S-Y et al. (2010) Cell 142:737-748]. Rapid translation of mgtL promotes formation of a secondary structure ...

The HamiltonianH = p2+x4+iAx, whereA is a real parameter, is investigated. The spectrum of H is discrete and entirely real and positive for |A| < 3.169. As |A| increases past this point, adjacent pairs of energy levels coalesce and then become complex, starting with the lowest-lying energy levels. For large energies, the values ofA at which this merging occurs scale as the three-quarters power ...

Haemophilus ducreyi is a gram-negative bacterium that is the causative agent of chancroid. Strain 35000HP has been well characterized and is representative of the majority of H. ducreyi strains. Strain 35000HP produces a lipooligosaccharide (LOS) that contains D-glycero-D-manno-heptose in the main oligosaccharide chain extension; the lbgB gene has been shown to encode the DD-heptosyltransferase...

Zinc ions play indispensable roles in biological chemistry. However, bacteria have an impressive ability to acquire Zn(2+) from the environment, making it exceptionally difficult to achieve Zn(2+) deficiency, and so a comprehensive understanding of the importance of Zn(2+) has not been attained. Reduction of the Zn(2+) content of Escherichia coli growth medium to 60 nm or less is reported here ...

Very recently a new method has been developed for finding lower bounds on the maximum number of codewords possible in a code of minimum distance d and length n . This method has led in turn to a number of interesting questions in graph theory and additive number theory. In this brief survey we summarize some of these developments. -/ * Visiting Professor, Computer Science Department, Stanford U...

BACKGROUND Measurement scales seeking to quantify latent traits like attitudes, are often developed using traditional psychometric approaches. Application of the Rasch unidimensional measurement model may complement or replace these techniques, as the model can be used to construct scales and check their psychometric properties. If data fit the model, then a scale with invariant measurement pro...

The USA’s federally funded Conservation Reserve Program (CRP) has largely been successful in restoring many critical ecosystem functions to millions of acres through the conversion of vulnerable croplands to diverse perennial plant communities—primarily to perennial grass and forb plantings. CRP contracts, however, on as much as 6.5 million hectares (ha) are now expiring. Aside from leaving the...