Selective Signal Detection in Solid-State NMR Using Rotor-Synchronized Dipolar Dephasing for the Analysis of Hemicellulose in Lignocellulosic Biomass
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Authors: Komatsu, Takanori; Kikuchi, Jun
Abstract
Solid-state dipolar dephasing filtered (DDF)-INADEQUATE experiments were used to detect the hemicellulosic signals of lignocellulosic mixtures; here dipolar dephasing was used as a signal filter to remove signals derived from cellulose. The maximum filtering efficiency was obtained when the dephasing time was adjusted to half the rotor period at a magic-angle spinning (MAS) frequency of 12 kHz, which indicated that the molecular motions in hemicelluloses are faster than those in cellulose. In a DDF-INADEQUATE spectrum of uniformly C-13-labeled lignocellulose from corn (Zea mays) collected with a dephasing time of 1/2v(MAS), the chemical shifts of beta-D-xylopyranose (Xylp) and alpha-L-arabinofuranose (Araf) in glucuronoarabinoxylan, the major hemicellulose in the secondary cell walls of the gramineous plant, were assigned.
Elevated Prevalence of Azole-Resistant Aspergillus fumigatus in Urban versus Rural Environments in the United Kingdom
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY
Authors: Sewell, Thomas R.; Zhang, Yuyi; Brackin, Amelie P.; Shelton, Jennifer M. G.; Rhodes, Johanna; Fisher, Matthew C.
Abstract
Azole resistance in the opportunistic pathogen Aspergillus fumigatus is increasing, dominated primarily by the following two environmentally associated resistance alleles: TR34/L98H and TR46/Y121F/T289A. By sampling soils across the South of England, we assess the prevalence of azole-resistant A. fumigatus (ARAf) in samples collected in both urban and rural locations. We characterize the susceptibility profiles of the resistant isolates to three medical azoles, identify the underlying genetic basis of resistance, and investigate their genetic relationships. ARAf was detected in 6.7% of the soil samples, with a higher prevalence in urban (13.8%) than rural (1.1%) locations. Twenty isolates were confirmed to exhibit clinical breakpoints for resistance to at least one of three medical azoles, with 18 isolates exhibiting resistance to itraconazole, 6 to voriconazole, and 2 showing elevated minimum inhibitory concentrations to posaconazole. Thirteen of the resistant isolates harbored the TR34/L98H resistance allele, and six isolates carried the TR46/Y121F/T289A allele. The 20 azole-resistant isolates were spread across five csp1 genetic subtypes, t01, t02, t04B, t09, and t18 with t02 being the predominant subtype. Our study demonstrates that ARAf can be easily isolated in the South of England, especially in urban city centers, which appear to play an important role in the epidemiology of environmentally linked drug-resistant A. fumigatus.