title: Identification of microcystins in a Lake Victoria cyanobacterial bloom using LC–MS with thiol derivatization

authors: Miles, Christopher O.

subjects: Microcystin

abstract: Microcystins are cyclic heptapeptides from cyanobacteria which are responsible for poisonings of livestock and humans. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analysed by LC–MS. Thiol derivatization of the α,β-unsaturated amide present in most microcystins was recently shown to simplify analysis of LC–MS chromatograms of a Microcystis culture, making it easier to identify peaks corresponding to microcystins in complex mixtures. This method was applied to analysis of extracts taken from a natural cyanobacteria bloom in Mwanza Gulf, Lake Victoria, Tanzania, in 2010, revealing the presence of numerous putative microcystin analogues in the sample. Results were verified using LC–MS², LC–MS/MS with precursor-ion scanning, and LC–HRMS, leading to identification of 8 major and 17 minor microcystins in the sample, including analogues of microcystin-RY, -RL and -RA. Microcystin-YR (2), -RR (3), and -RY (9) were isolated from bloom material from Lake Victoria, and the structure of 9 was confirmed by NMR spectroscopic analysis and NMR spectral comparison with 2 and 3. Confirmation of the structure of MC-RY (9) facilitated detailed analysis of its MS² spectrum, thereby supporting the structures of related analogues tentatively established on the basis of MS analyses.

text: Identification of microcystins in a Lake Victoria cyanobacterial bloom using LC–MS with thiol derivatization Microcystins are cyclic heptapeptides from cyanobacteria which are responsible for poisonings of livestock and humans. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analysed by LC–MS. Thiol derivatization of the α,β-unsaturated amide present in most microcystins was recently shown to simplify analysis of LC–MS chromatograms of a Microcystis culture, making it easier to identify peaks corresponding to microcystins in complex mixtures. This method was applied to analysis of extracts taken from a natural cyanobacteria bloom in Mwanza Gulf, Lake Victoria, Tanzania, in 2010, revealing the presence of numerous putative microcystin analogues in the sample. Results were verified using LC–MS², LC–MS/MS with precursor-ion scanning, and LC–HRMS, leading to identification of 8 major and 17 minor microcystins in the sample, including analogues of microcystin-RY, -RL and -RA. Microcystin-YR (2), -RR (3), and -RY (9) were isolated from bloom material from Lake Victoria, and the structure of 9 was confirmed by NMR spectroscopic analysis and NMR spectral comparison with 2 and 3. Confirmation of the structure of MC-RY (9) facilitated detailed analysis of its MS² spectrum, thereby supporting the structures of related analogues tentatively established on the basis of MS analyses.

year: 2013

title: Full 2-port vector-corrected network analyzer in the acoustic domain

authors: MacDonell, Marcus Scott Glengarry

abstract: This manuscript presents the theory and design of a Vector-corrected Network Analyzer (VNA) realized in the acoustic domain. This is a novel measurement instrument based on the established microwave vector network analyzer. It employs directional couplers to separate forward and reverse traveling waves in acoustic waveguide. This instrument is intended to supersede the acoustic impedance tube. Advantages include greatly increased measurement speed and potential for traceability to external standards. Traceability is achieved by means of a calibration through an analytical solution of the error matrix produced from the measurement of a limited number of available acoustic standards. Operation is verified through analysis of the acoustic S-parameters of a passive, asymmetrical, reciprocal acoustic device constructed inside the acoustic waveguide. To the best of our knowledge this Acoustic Vector-corrected Network Analyzer (AVNA) is the first of its kind.

text: Full 2-port vector-corrected network analyzer in the acoustic domain This manuscript presents the theory and design of a Vector-corrected Network Analyzer (VNA) realized in the acoustic domain. This is a novel measurement instrument based on the established microwave vector network analyzer. It employs directional couplers to separate forward and reverse traveling waves in acoustic waveguide. This instrument is intended to supersede the acoustic impedance tube. Advantages include greatly increased measurement speed and potential for traceability to external standards. Traceability is achieved by means of a calibration through an analytical solution of the error matrix produced from the measurement of a limited number of available acoustic standards. Operation is verified through analysis of the acoustic S-parameters of a passive, asymmetrical, reciprocal acoustic device constructed inside the acoustic waveguide. To the best of our knowledge this Acoustic Vector-corrected Network Analyzer (AVNA) is the first of its kind.

year: 2022

title: The Māori health data governance model: A planning and protocol checklist

authors: Kremer, Lisa

abstract: Māori health data (MHD) governance is a critical enabler of achieving health equity for Māori. The Māori Data Governance Model (the Model) provides a framework for all stages of Māori data handling but has yet to be meaningfully implemented within health settings. This study aimed to meet the need for health-specific guidance by adapting the Model to create an MHD governance checklist. This checklist can be used by health researchers and agencies to develop and embed their own MHD governance protocol (e.g. embed within study protocol).

text: The Māori health data governance model: A planning and protocol checklist Māori health data (MHD) governance is a critical enabler of achieving health equity for Māori. The Māori Data Governance Model (the Model) provides a framework for all stages of Māori data handling but has yet to be meaningfully implemented within health settings. This study aimed to meet the need for health-specific guidance by adapting the Model to create an MHD governance checklist. This checklist can be used by health researchers and agencies to develop and embed their own MHD governance protocol (e.g. embed within study protocol).

year: 2025