title: Identification of extracellular siderophores and a related peptide from the endophytic fungus Epichloë festucae in culture and endophyte-infected Lolium perenne

authors: Koulman, Albert

subjects: Epichloë festucae

abstract: A number of genes encoding non-ribosomal peptide synthetases (NRPSs) have been identified in fungi of Epichloë/Neotyphodium species, endophytes of Pooid grasses, including sidN, putatively encoding a ferrichrome siderophore-synthesizing NRPS. Targeted gene replacement and complementation of sidN in Epichloë festucae has established that extracellular siderophore epichloënin A is the major product of the SidN enzyme complex (Johnson et al., 2007a). We report here high resolution mass spectrometric fragmentation experiments and NMR analysis of an isolated fraction establishing that epichloënin A is a siderophore of the ferrichrome family, comprising a cyclic sequence of four glycines, a glutamine and three Nδ-trans-anhydromevalonyl–Nδ-hydroxyornithine (AMHO) moieties. Epichloënin A is unusual among ferrichrome siderophores in comprising an octapeptide rather than hexapeptide sequence, and in incorporating a glutamine residue. During this investigation we have established that desferrichrome siderophores with pendant trans-AMHO groups can be distinguished from those with pendant cis-AMHO groups by the characteristic neutral loss of an hydroxyornithine moiety in the MS/MS spectrum. A minor component, epichloënin B, has been characterized as the triglycine variant by mass spectrometry. A peptide characterized by mass spectrometry as the putative deoxygenation product, epichloëamide has been detected together with ferriepichloënin A in guttation fluid from ryegrass (Lolium perenne) plants infected with wild-type E. festucae, but not in plants infected with the ΔsidN mutant strain, and also detected at trace levels in wild-type E. festucae fungal culture.

text: Identification of extracellular siderophores and a related peptide from the endophytic fungus Epichloë festucae in culture and endophyte-infected Lolium perenne A number of genes encoding non-ribosomal peptide synthetases (NRPSs) have been identified in fungi of Epichloë/Neotyphodium species, endophytes of Pooid grasses, including sidN, putatively encoding a ferrichrome siderophore-synthesizing NRPS. Targeted gene replacement and complementation of sidN in Epichloë festucae has established that extracellular siderophore epichloënin A is the major product of the SidN enzyme complex (Johnson et al., 2007a). We report here high resolution mass spectrometric fragmentation experiments and NMR analysis of an isolated fraction establishing that epichloënin A is a siderophore of the ferrichrome family, comprising a cyclic sequence of four glycines, a glutamine and three Nδ-trans-anhydromevalonyl–Nδ-hydroxyornithine (AMHO) moieties. Epichloënin A is unusual among ferrichrome siderophores in comprising an octapeptide rather than hexapeptide sequence, and in incorporating a glutamine residue. During this investigation we have established that desferrichrome siderophores with pendant trans-AMHO groups can be distinguished from those with pendant cis-AMHO groups by the characteristic neutral loss of an hydroxyornithine moiety in the MS/MS spectrum. A minor component, epichloënin B, has been characterized as the triglycine variant by mass spectrometry. A peptide characterized by mass spectrometry as the putative deoxygenation product, epichloëamide has been detected together with ferriepichloënin A in guttation fluid from ryegrass (Lolium perenne) plants infected with wild-type E. festucae, but not in plants infected with the ΔsidN mutant strain, and also detected at trace levels in wild-type E. festucae fungal culture.

year: 2012

title: Extracting information from time series data from rechargable batteries

authors: Wilson, Marcus T.

abstract: In practical applications such as electric vehicles, mobile phones, etc, rechargable batteries are continually charged and discharged, resulting in time-varying voltages and currents. The relationship between voltage and current depends on the properties of the battery and analysis of the time-series can yield useful information about battery performance. However, analysis is complicated because the charge-discharge cycles are not periodic or regular.  For example, in an electric vehicle the battery might undergo intensive periods of discharge and charge, corresponding to acceleration and regenerative braking respectively, while the vehicle is in use, followed by long periods of inactivity.  There is structure on the timescales of seconds through to days. We have recorded voltage, current and temperature of several batteries in a laboratory as they have been continually cycled over many months using both regular and irregular cycles, the latter mimicking cycles experienced in practical applications. We have used established methods of time-series analysis such as the Hilbert Transform to investigate the relationships between voltage and current, and have shown that results agree with more sophisticated but less practical methods of battery characterisation such as electrical impedance spectroscopy. The relationships imply that several different processes occur, depending on time-scale.

text: Extracting information from time series data from rechargable batteries In practical applications such as electric vehicles, mobile phones, etc, rechargable batteries are continually charged and discharged, resulting in time-varying voltages and currents. The relationship between voltage and current depends on the properties of the battery and analysis of the time-series can yield useful information about battery performance. However, analysis is complicated because the charge-discharge cycles are not periodic or regular.  For example, in an electric vehicle the battery might undergo intensive periods of discharge and charge, corresponding to acceleration and regenerative braking respectively, while the vehicle is in use, followed by long periods of inactivity.  There is structure on the timescales of seconds through to days. We have recorded voltage, current and temperature of several batteries in a laboratory as they have been continually cycled over many months using both regular and irregular cycles, the latter mimicking cycles experienced in practical applications. We have used established methods of time-series analysis such as the Hilbert Transform to investigate the relationships between voltage and current, and have shown that results agree with more sophisticated but less practical methods of battery characterisation such as electrical impedance spectroscopy. The relationships imply that several different processes occur, depending on time-scale.

year: 2023-09-15

title: Oranga whānau, oranga niho: The oral health status of 5-year-old Māori children. A case study

authors: Te Amo, Kirstin Mei

subjects: Maori health

abstract: Research has shown that the oral health of Māori is far worse than non-Māori across all
age groups. The objective of this research study was to assess the dental wellbeing of
5-year olds with a specific focus on Māori children currently residing in the Hamilton City
region. In addition, this research focused on the impact that social, economic, cultural
and environmental factors have on oral health. A total of 32 participants were invited to
take part in this research: 15 5-year-old children from three selected schools, 15 (of the
children's) caregivers and 2 dental therapists who work in the Hamilton City region.
The findings indicated that overall Māori children and children of lower socio-economic
status had a much higher prevalence of dental caries (tooth decay) than non-Māori
children and children of higher socio-economic status. A number of contributing factors
were shown to be responsible for this disparity including the cultural inappropriateness
of oral health services and resources, affordability, role-modelling, parental awareness
and education, and the transient nature of families.
It was found that no one strategy or intervention will achieve dramatic improvements in
Māori oral health as a concerted effort is required by Local and Central Government, the
Health Sector and Māori communities.

text: Oranga whānau, oranga niho: The oral health status of 5-year-old Māori children. A case study Research has shown that the oral health of Māori is far worse than non-Māori across all
age groups. The objective of this research study was to assess the dental wellbeing of
5-year olds with a specific focus on Māori children currently residing in the Hamilton City
region. In addition, this research focused on the impact that social, economic, cultural
and environmental factors have on oral health. A total of 32 participants were invited to
take part in this research: 15 5-year-old children from three selected schools, 15 (of the
children's) caregivers and 2 dental therapists who work in the Hamilton City region.
The findings indicated that overall Māori children and children of lower socio-economic
status had a much higher prevalence of dental caries (tooth decay) than non-Māori
children and children of higher socio-economic status. A number of contributing factors
were shown to be responsible for this disparity including the cultural inappropriateness
of oral health services and resources, affordability, role-modelling, parental awareness
and education, and the transient nature of families.
It was found that no one strategy or intervention will achieve dramatic improvements in
Māori oral health as a concerted effort is required by Local and Central Government, the
Health Sector and Māori communities.

year: 2007