title: Thiol derivatization for LC-MS identification of microcystins in complex matrices

authors: Miles, Christopher O.

subjects: tandem mass-spectrometry

abstract: Microcystins are a group of cyclic heptapeptides originating from cyanobacteria. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analyzed by LC-MS. Derivatization with appropriate thiols (e.g., mercaptoethanol) of the olefin in the alpha,beta-unsaturated amide present in most microcystins was shown to simplify analysis of LC-MS chromatograms of sample extracts, making it much easier to identify peaks corresponding to candidate microcystins. Furthermore, interpretation of MS2 spectra was facilitated by addition of the mass associated with the thiol to the alpha,beta-unsaturated amide of microcystins. Cyanotoxins containing Mdha or Dha reacted readily with thiols, whereas Mser, Ser, Mdhb, and thiol-derivatives of Mdha or Dha did not react under the conditions used. This approach therefore provides a convenient LC-MS method to obtain evidence for the presence of Mdha or Dha and can likely be used to differentiate between the isobaric amino acids Mdha and Dhb in candidate cyanotoxin peaks. When O-(2-mercaptoethyl)-O'-methyl-hexa(ethylene glycol) (MEMHEG) (M(w)t. 356) was used as the thiol, the resulting derivatives eluted in an LC-MS mass window that was largely free of interferences. This approach simplifies detection of candidate microcystin analogues even in the presence of complex mixtures of coeluting components. The method was used for qualitative analysis of a Microcystis aeruginosa culture from Lake Naivasha, Kenya, and the results were verified using precursor-ion scanning and high-resolution mass spectrometry.

text: Thiol derivatization for LC-MS identification of microcystins in complex matrices Microcystins are a group of cyclic heptapeptides originating from cyanobacteria. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analyzed by LC-MS. Derivatization with appropriate thiols (e.g., mercaptoethanol) of the olefin in the alpha,beta-unsaturated amide present in most microcystins was shown to simplify analysis of LC-MS chromatograms of sample extracts, making it much easier to identify peaks corresponding to candidate microcystins. Furthermore, interpretation of MS2 spectra was facilitated by addition of the mass associated with the thiol to the alpha,beta-unsaturated amide of microcystins. Cyanotoxins containing Mdha or Dha reacted readily with thiols, whereas Mser, Ser, Mdhb, and thiol-derivatives of Mdha or Dha did not react under the conditions used. This approach therefore provides a convenient LC-MS method to obtain evidence for the presence of Mdha or Dha and can likely be used to differentiate between the isobaric amino acids Mdha and Dhb in candidate cyanotoxin peaks. When O-(2-mercaptoethyl)-O'-methyl-hexa(ethylene glycol) (MEMHEG) (M(w)t. 356) was used as the thiol, the resulting derivatives eluted in an LC-MS mass window that was largely free of interferences. This approach simplifies detection of candidate microcystin analogues even in the presence of complex mixtures of coeluting components. The method was used for qualitative analysis of a Microcystis aeruginosa culture from Lake Naivasha, Kenya, and the results were verified using precursor-ion scanning and high-resolution mass spectrometry.

year: 2012

title: Girmit, postmemory, and Subramani

authors: Long, Maebh

subjects: Girmit

abstract: The centenary of indenture in Fiji was celebrated with public displays, speeches, parades, and publications. The momentum for critical and creative response grew in tandem with the wave of publications inspired by the end of colonial rule in many Pacific Island countries. This period of increased agency and autonomy was also a time of political uncertainty in Fiji, as questions of the nation’s identity and direction were raised. For many Indo-Fijian writers rootedness in Fiji was voiced through the traumas of indenture, which they invested with mythic valence, and which can be understood as operating as an origin story for Indo-Fijians. Vijay Mishra considered indenture, or girmit, to be a foundational ideology for Indo-Fijian writers, but viewing girmit in terms of false consciousness leads him to read Indo-Fijian anxieties in terms of political blindness and cultural insularity. Building instead on Sudesh Mishra’s elaboration of girmit as non-agreement, and Vijay Mishra’s later revisions of girmit ideology as founded on memories of betrayal, this article argues that girmit can be productively understood through Marianne Hirsh’s work on postmemory. Looking at writings of the centenary, and in particular Subramani’s short stories, this article proposes that the traumas of girmit that haunt writings of the period do so as postmemories.

text: Girmit, postmemory, and Subramani The centenary of indenture in Fiji was celebrated with public displays, speeches, parades, and publications. The momentum for critical and creative response grew in tandem with the wave of publications inspired by the end of colonial rule in many Pacific Island countries. This period of increased agency and autonomy was also a time of political uncertainty in Fiji, as questions of the nation’s identity and direction were raised. For many Indo-Fijian writers rootedness in Fiji was voiced through the traumas of indenture, which they invested with mythic valence, and which can be understood as operating as an origin story for Indo-Fijians. Vijay Mishra considered indenture, or girmit, to be a foundational ideology for Indo-Fijian writers, but viewing girmit in terms of false consciousness leads him to read Indo-Fijian anxieties in terms of political blindness and cultural insularity. Building instead on Sudesh Mishra’s elaboration of girmit as non-agreement, and Vijay Mishra’s later revisions of girmit ideology as founded on memories of betrayal, this article argues that girmit can be productively understood through Marianne Hirsh’s work on postmemory. Looking at writings of the centenary, and in particular Subramani’s short stories, this article proposes that the traumas of girmit that haunt writings of the period do so as postmemories.

year: 2018

title: The Role of Fatherhood in the Everyday Life of Young Māori Men

authors: Elkington, Angus Marangai Brons

subjects: maori men

abstract: Little research exists that explores the positive aspects of young Māori fathers. The aim of this study was to explore the everyday lived reality of expectant and young Māori males as fathers and partners, within the context of a positive based approach and Kaupapa Māori research framework. A secondary objective of this study was to provide ideas to enhance parent resources for young Māori fathers, such as father centric parenting programmes and mobile applications. The research was derived from semi-structured interviews, which explored the unique experiences and narratives of eight young Māori fathers between the age of 16 and 25 years of age. Using thematic analysis, the findings were categorised into key themes that portrayed their perception and attitudes to roles, responsibility, relationships, barriers, and wellbeing strategies. The findings identified, a strong desire of young Māori fathers to be involved with their children and that the quality of whānau relationships provided resilience, support, and motivation to fulfil the responsibilities of fatherhood. The young Māori fathers had strong goals and aspirations but acknowledged barriers that delayed their ability to achieve them. In the outcome of this study, I have tried to portray a positive understanding of young Māori fathers and to challenge the negative stereotypes that persist in New Zealand society. Furthermore, this research supports the need for restorative cultural practices as the key to wellbeing for our whānau and further investigations in regards to policy reforms and resources to include full participation in society.

text: The Role of Fatherhood in the Everyday Life of Young Māori Men Little research exists that explores the positive aspects of young Māori fathers. The aim of this study was to explore the everyday lived reality of expectant and young Māori males as fathers and partners, within the context of a positive based approach and Kaupapa Māori research framework. A secondary objective of this study was to provide ideas to enhance parent resources for young Māori fathers, such as father centric parenting programmes and mobile applications. The research was derived from semi-structured interviews, which explored the unique experiences and narratives of eight young Māori fathers between the age of 16 and 25 years of age. Using thematic analysis, the findings were categorised into key themes that portrayed their perception and attitudes to roles, responsibility, relationships, barriers, and wellbeing strategies. The findings identified, a strong desire of young Māori fathers to be involved with their children and that the quality of whānau relationships provided resilience, support, and motivation to fulfil the responsibilities of fatherhood. The young Māori fathers had strong goals and aspirations but acknowledged barriers that delayed their ability to achieve them. In the outcome of this study, I have tried to portray a positive understanding of young Māori fathers and to challenge the negative stereotypes that persist in New Zealand society. Furthermore, this research supports the need for restorative cultural practices as the key to wellbeing for our whānau and further investigations in regards to policy reforms and resources to include full participation in society.

year: 2016