title: Hemicellulolytic and cellulolytic functions of the domains of a β-mannanase cloned from Caldicellosiruptor saccharolyticus

authors: Frangos, Tracy

subjects: mannanase

abstract: Various combinations of the four domains of the multifunctional mannanase from Caldicellosiruptor saccharolyticus have been cloned and expressed in Escherichia coli. The four domains comprise two catalytic domains (1 and 4), and two putative cellulose binding domains (2 and 3). Each of the six gene products (Man1, Man123, Man1234, Man23, Man234 and Man4) was partially purified by heat treatment.
The enzymes Man1234, Man123 and Man1 exhibited activity on mannans, and Man1234, Man234 and Man4 exhibited activity on xylan and carboxymethylcellulose (CMC). For the complete enzyme (Man1234) all activities were of the same order of magnitude. Activities were additive against a mixture of mannan and xylan or mannan and CMC (but not xylan and CMC). The expression product Man23 exhibited activity on none of the substrates tested, nor did its presence influence thermostability or significantly reduce the Km value for any of the substrates. However, when expressed in combination with domains 1 or 4 it greatly increased their activity.
We conclude that domain 1 catalyses mannan hydrolysis and domain 4 catalyses xylan and CMC hydrolysis at the same active site: domains 2 and 3 have no obvious function, since they do not reduce substrate Km nor affect thermostability. However, their effect on rates of substrate hydrolysis may indicate a role influencing the conformation of the adjacent catalytic domains.

text: Hemicellulolytic and cellulolytic functions of the domains of a β-mannanase cloned from Caldicellosiruptor saccharolyticus Various combinations of the four domains of the multifunctional mannanase from Caldicellosiruptor saccharolyticus have been cloned and expressed in Escherichia coli. The four domains comprise two catalytic domains (1 and 4), and two putative cellulose binding domains (2 and 3). Each of the six gene products (Man1, Man123, Man1234, Man23, Man234 and Man4) was partially purified by heat treatment.
The enzymes Man1234, Man123 and Man1 exhibited activity on mannans, and Man1234, Man234 and Man4 exhibited activity on xylan and carboxymethylcellulose (CMC). For the complete enzyme (Man1234) all activities were of the same order of magnitude. Activities were additive against a mixture of mannan and xylan or mannan and CMC (but not xylan and CMC). The expression product Man23 exhibited activity on none of the substrates tested, nor did its presence influence thermostability or significantly reduce the Km value for any of the substrates. However, when expressed in combination with domains 1 or 4 it greatly increased their activity.
We conclude that domain 1 catalyses mannan hydrolysis and domain 4 catalyses xylan and CMC hydrolysis at the same active site: domains 2 and 3 have no obvious function, since they do not reduce substrate Km nor affect thermostability. However, their effect on rates of substrate hydrolysis may indicate a role influencing the conformation of the adjacent catalytic domains.

year: 1999-08

title: Eruption and emplacement of the 1.3-Ma Ongatiti Ignimbrite, New Zealand:  Regional pathways, particle processes, and pumice evolution associated with a large-volume pyroclastic flow deposit

authors: Yousef Zadeh, Elham

abstract: Pyroclastic flows are the most devastating phenomena of explosive volcanic eruptions. These hazardous density currents are able to travel several tens of kilometers radially away from their source as fast, hot density currents. Due to the enveloping ash cloud, it is still impossible to directly study pyroclastic flows, however, their deposits (i.e. ignimbrites) provide useful insight into their internal processes.

The Ongatiti Ignimbrite was sourced from Mangakino caldera (1600-950 ka), the oldest volcanic center in the Taupo Volcanic Zone, North Island, New Zealand. The crystal- and pumice-rich ignimbrite offers a unique opportunity to understand an ancient and large-volume pyroclastic flow as well as more details about particle processes and pumice evolution. The minimum deposit volume for the Ongatiti Ignimbrite has been revised to approximately 720 km³, or 512 km³ dense rock equivalent. Previous studies proposed ages from 1.21 to 1.28 Ma by dating methods, such as ⁴⁰Ar/³⁹Ar, K/Ar, and zircon fission-track. This research used the (U-Th)/He method to determine an age of 1.3 Ma. 

This study has combined field facies analysis and GIS methods to characterize the Ongatiti Ignimbrite. The topographic controls on the spatial distribution of the ignimbrite has been determined to understand pyroclastic flow pathways through valleys and over hills. The Ongatiti Ignimbrite was a landscape-modifying event that covered at least the western North Island and as far away as Auckland and Wellington. It is a welded to non-welded, columnar-jointed, cliff-forming deposit, that has been divided into nine facies based on the variation in pumice and lithic clast abundance, and welding rank. 
This study also focuses on the texture and components of the ignimbrite matrix to better understand the magma fragmentation process, the transportational and depositional dynamics of the gas-ash fluid, and the post-emplacement processes. The microtextures of ignimbrite matrix were described and quantified by using optical microscopy, scanning electron microscopy, synchrotron x-ray microtomography, electron probe microanalysis, and X-ray powder diffraction (XRD).
The matrix is poorly sorted and varies in the size and texture of ash-sized pumice fragments, glass shards, crystals, and lithic clasts. Glass shards range in shape between dominantly platy, Y-shaped, and complex shapes, and in size from a few microns to about 900 microns. The matrix is crystal-rich and comprises primary subhedral to anhedral volcanic crystals (plagioclase, quartz, pyroxene, hornblende, and Ti-Fe oxides and range between 100 to a few 1000 microns in size. The degree of welding in the matrix is defined by crystal-crystal contacts and deformation of glass shards around particles, and the highest degree of welding is shown by moderately deformed shards. 
The physical characteristics and chemical composition of pumice clasts were determined, and the main pumice textures were recognised as vesicular, fibrous, microvesicular and dense type.  Tomographic imaging shows different vesicularities and local crystal arrangement within pumice and ignimbrite. Glass chemical analysis shows two different groups, higher-silica (~80-81 wt%), and high-silica (76-78 wt%). 
The Ongatiti Ignimbrite was emplaced by a super-eruption with a volcanic explosivity index (VEI) of 7, and eruptions of similar size could catastrophically bury a vast area of the North Island. The matrix of the Ongatiti Ignimbrite suggests complex particle interactions within the ash-gas fluid of pyroclastic flows. Microtomographic imaging of ignimbrite components offers new insights into understanding these complex processes.

text: Eruption and emplacement of the 1.3-Ma Ongatiti Ignimbrite, New Zealand:  Regional pathways, particle processes, and pumice evolution associated with a large-volume pyroclastic flow deposit Pyroclastic flows are the most devastating phenomena of explosive volcanic eruptions. These hazardous density currents are able to travel several tens of kilometers radially away from their source as fast, hot density currents. Due to the enveloping ash cloud, it is still impossible to directly study pyroclastic flows, however, their deposits (i.e. ignimbrites) provide useful insight into their internal processes.

The Ongatiti Ignimbrite was sourced from Mangakino caldera (1600-950 ka), the oldest volcanic center in the Taupo Volcanic Zone, North Island, New Zealand. The crystal- and pumice-rich ignimbrite offers a unique opportunity to understand an ancient and large-volume pyroclastic flow as well as more details about particle processes and pumice evolution. The minimum deposit volume for the Ongatiti Ignimbrite has been revised to approximately 720 km³, or 512 km³ dense rock equivalent. Previous studies proposed ages from 1.21 to 1.28 Ma by dating methods, such as ⁴⁰Ar/³⁹Ar, K/Ar, and zircon fission-track. This research used the (U-Th)/He method to determine an age of 1.3 Ma. 

This study has combined field facies analysis and GIS methods to characterize the Ongatiti Ignimbrite. The topographic controls on the spatial distribution of the ignimbrite has been determined to understand pyroclastic flow pathways through valleys and over hills. The Ongatiti Ignimbrite was a landscape-modifying event that covered at least the western North Island and as far away as Auckland and Wellington. It is a welded to non-welded, columnar-jointed, cliff-forming deposit, that has been divided into nine facies based on the variation in pumice and lithic clast abundance, and welding rank. 
This study also focuses on the texture and components of the ignimbrite matrix to better understand the magma fragmentation process, the transportational and depositional dynamics of the gas-ash fluid, and the post-emplacement processes. The microtextures of ignimbrite matrix were described and quantified by using optical microscopy, scanning electron microscopy, synchrotron x-ray microtomography, electron probe microanalysis, and X-ray powder diffraction (XRD).
The matrix is poorly sorted and varies in the size and texture of ash-sized pumice fragments, glass shards, crystals, and lithic clasts. Glass shards range in shape between dominantly platy, Y-shaped, and complex shapes, and in size from a few microns to about 900 microns. The matrix is crystal-rich and comprises primary subhedral to anhedral volcanic crystals (plagioclase, quartz, pyroxene, hornblende, and Ti-Fe oxides and range between 100 to a few 1000 microns in size. The degree of welding in the matrix is defined by crystal-crystal contacts and deformation of glass shards around particles, and the highest degree of welding is shown by moderately deformed shards. 
The physical characteristics and chemical composition of pumice clasts were determined, and the main pumice textures were recognised as vesicular, fibrous, microvesicular and dense type.  Tomographic imaging shows different vesicularities and local crystal arrangement within pumice and ignimbrite. Glass chemical analysis shows two different groups, higher-silica (~80-81 wt%), and high-silica (76-78 wt%). 
The Ongatiti Ignimbrite was emplaced by a super-eruption with a volcanic explosivity index (VEI) of 7, and eruptions of similar size could catastrophically bury a vast area of the North Island. The matrix of the Ongatiti Ignimbrite suggests complex particle interactions within the ash-gas fluid of pyroclastic flows. Microtomographic imaging of ignimbrite components offers new insights into understanding these complex processes.

year: 2020

title: Waiwharangi

authors: Maxwell, Te Kahautu

abstract: Haka. Lyrics/Musical score composed by Te Kahautu Maxwell. Performed by Ōpōtiki Mai Tawhiti (Kapa Haka group) (4mins)

Waiata: Tira Aroha
Whakaeke: Haere mai rā
Mōteatea: Te Pātere a Te Turuki
Poi: Iarararararī
Waiata ā ringa: Taku Mana Māori Motuhake
Haka: Waiwharangi
Whakawātea: Āio

text: Waiwharangi Haka. Lyrics/Musical score composed by Te Kahautu Maxwell. Performed by Ōpōtiki Mai Tawhiti (Kapa Haka group) (4mins)

Waiata: Tira Aroha
Whakaeke: Haere mai rā
Mōteatea: Te Pātere a Te Turuki
Poi: Iarararararī
Waiata ā ringa: Taku Mana Māori Motuhake
Haka: Waiwharangi
Whakawātea: Āio

year: 2020-02-06