Few studies have systematically standardised and evaluated matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for identification of yeasts from bloodstream infections. This is rapidly becoming pertinent for early identification of yeasts and appropriate antifungal therapy. We used 354 yeast strains identified by polymerase chain reaction (PCR) sequencing for standardisation and 367 blind clinical strains for validation of our MALDI-TOF MS protocols. We also evaluated different sample preparation methods and found the on-plate formic acid extraction method as most cost- and time-efficient. The MALDI-TOF assay correctly identified 98.9% of PCR-sequenced yeasts. Novel main spectrum projections (MSP) were developed for Candida auris, C. viswanathii and Kodamaea ohmeri, which were missing from the Bruker MALDI-TOF MS database. Spectral cut-offs computed by receiver operating characteristics (ROC) analysis showed 99.4% to 100% accuracy at a log score of ≥ 1.70 for C. tropicalis, C. parapsilosis, C. pelliculosa, C. orthopsilosis, C. albicans, C. rugosa, C. guilliermondii, C. lipolytica, C. metapsilosis, C. nivariensis. The differences in the species-specific scores of our standardisation and blind validation strains were not statistically significant, implying the optimal performance of our test protocol. The MSPs of the three new species also were validated. We conclude that MALDI-TOF MS is a rapid, accurate and reliable tool for identification of bloodstream yeasts. With proper standardisation, validation and regular database expansion, its efficiency can be further enhanced.
A family of supramolecular reagents containing two different binding sites, pyridine and aminopyrimidine, were allowed to react with iodo-or bromo-substituted benzoic acids in order to assemble individual molecules into larger architectures with precise intermolecular interactions, using a combination of hydrogen-and halogen-bonds. The hydrogen-bond based amino-pyrimidine/ carboxylic acid or amino-pyrimidinium/carboxylate synthons are responsible for the assembly of the primary structural motif in every case (7/7 times, 100% supramolecular yield), while I⋯N, Br⋯N, and I⋯O, halogen bonds play a structural supporting role by organizing these supermolecules into extended 1-D and 2-D architectures (5/7 times, 71% supramolecular yield). These results illustrate how two different non-covalent interactions can be employed side-by-side in the reliable construction of extended molecular solid-state networks with predictable connectivity and dimensionality.
A halogen-bonded capsule is obtained via directed assembly of a rigid tetra(3-pyridyl) cavitand and a flexible tetra(4-iodotetrafluorophenyl)calix[4] arene. The pyridyl nitrogen atoms from one cavitand molecule interact with the iodine atoms of a single calixarene molecule through short and directional I⋯N halogen bonds. The flexibility of the ethylenedioxy moieties on the calixarene platform results in positional flexibility of the iodotetrafluorobenzene sites which, coupled with a supramolecular chelating effect, allow for an effective partner-induced geometric fitting between four nitrogen atoms on the cavitand and four iodine atoms on the calixarene
Crystal Growth & DesignCOMMUNICATION cations to hold the capsules together in the solid state, which provided enhanced stabilities in aqueous solutions with high sodium concentrations and strongly basic pH. As these conditions are very similar to those found in nuclear wastes, the results reported here promise to provide in the near future the basis for a viable technology for sulfate separation from such wastes.' ASSOCIATED CONTENT b S Supporting Information. Crystallographic data in CIF format, details of the X-ray structural determinations, synthetic procedures, sulfate separation and ligand recovery experiments. This material is available free of charge via the Internet at http:// pubs.acs.org.
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