title: The upper limits of enzyme thermal stability

authors: Daniel, Roy M.

subjects: enzymes

abstract: Some enzymes, such as those from extreme thermophiles, have significant half-lives above 100°C. The differences in structure and function between these very stable and less stable enzymes are relatively small and are comparable with those differences found among enzymes of similar stability. Recent evidence suggests that protein degradative reactions at high temperatures (>80°C) occur only slowly in conformationally intact proteins, so that conformational stability may still dictate the upper temperature limit for enzyme activity. The interrelationship of both conformational stability and enzymatic activity with protein flexibility suggests that in naturally occurring enzymes, we cannot expect to find stability at temperatures far above those which are optimum for the growth of the organism. Genetic and enzyme engineering studies are promising in terms of enhancing conformational stability, but are likely to require case-by-case knowledge of the enzyme concerned, and stability enhancements achieved so far are relatively small. Furthermore, engineered increases in stability may well be accompanied by a decrease in specific activity. Nevertheless, it should be feasible to engineer enzymes to be substantially more stable than any of those found so far in nature where useful half-lives above 120°C are already available.

text: The upper limits of enzyme thermal stability Some enzymes, such as those from extreme thermophiles, have significant half-lives above 100°C. The differences in structure and function between these very stable and less stable enzymes are relatively small and are comparable with those differences found among enzymes of similar stability. Recent evidence suggests that protein degradative reactions at high temperatures (>80°C) occur only slowly in conformationally intact proteins, so that conformational stability may still dictate the upper temperature limit for enzyme activity. The interrelationship of both conformational stability and enzymatic activity with protein flexibility suggests that in naturally occurring enzymes, we cannot expect to find stability at temperatures far above those which are optimum for the growth of the organism. Genetic and enzyme engineering studies are promising in terms of enhancing conformational stability, but are likely to require case-by-case knowledge of the enzyme concerned, and stability enhancements achieved so far are relatively small. Furthermore, engineered increases in stability may well be accompanied by a decrease in specific activity. Nevertheless, it should be feasible to engineer enzymes to be substantially more stable than any of those found so far in nature where useful half-lives above 120°C are already available.

year: 1996

title: Language and literacy on the ground: disconnects between government policy and employer perspectives

authors: Hunter, Judy

subjects: literacy

abstract: Education to meet labour market demands and employer needs is a key priority in New Zealand's education policy. Government agendas for language and literacy education align with global discourses that link economic productivity to quality control, standardisation and proceduralisation through close regulation and funding. Yet, the interviews reported on here, involving employers of migrants, show that employers accept a range of linguistic diversity and judge migrant employees in subjective, complex ways. These employers tend to see effective communication as embedded in the cultures and relationships of their workplaces. Yet, they also tend to form negative judgments about employees based on dominant policy discourses and popular images of migrants as Others. The implications challenge government policy but at the same time point to spaces for critical work on change.

text: Language and literacy on the ground: disconnects between government policy and employer perspectives Education to meet labour market demands and employer needs is a key priority in New Zealand's education policy. Government agendas for language and literacy education align with global discourses that link economic productivity to quality control, standardisation and proceduralisation through close regulation and funding. Yet, the interviews reported on here, involving employers of migrants, show that employers accept a range of linguistic diversity and judge migrant employees in subjective, complex ways. These employers tend to see effective communication as embedded in the cultures and relationships of their workplaces. Yet, they also tend to form negative judgments about employees based on dominant policy discourses and popular images of migrants as Others. The implications challenge government policy but at the same time point to spaces for critical work on change.

year: 2012

title: Turning a negative into a positive: Aquatic weed harvesting Lake Rotoehu

authors: Mallinson, Richard

abstract: The submerged aquatic weed hornwort (Ceratophyllum demersum) has become widespread through Lake Rotoehu since its establishment in the lake around 2000. This exotic pest plant is surface reaching in large parts of this shallow lake making it a perfect candidate for mechanical harvesting.
As part of the Te Arawa - Rotorua Lakes Programme the Lake Rotoehu Action Plan sets out nutrient reduction targets for nitrogen and phosphorus. Realising these targets is integral if lake water quality is to be restored to the trophic level index (TLI) target for Lake
Rotoehu. Restoration measures have included land use management efforts to arrest nutrient inputs, phosphorus locking through alum dosing, floating wetlands, and most recently the deployment of two aerators. To date the most successful in-lake nutrient reduction method has been mechanical harvest of hornwort.
Aquatic weed harvesting has resulted in reaching a significant portion of the annual nutrient target for the lake catchment. Attaining this level of nutrient removal has manifested in tangible water quality gains in the past few years. Most noticeable is the reduction in cyanobacterial (blue-green) algal blooms which had been prevalent in the lake in summer months. We discuss the practicalities and problems of submerged lake weed harvesting, disposal options, and impacts of this activity on the lake.

text: Turning a negative into a positive: Aquatic weed harvesting Lake Rotoehu The submerged aquatic weed hornwort (Ceratophyllum demersum) has become widespread through Lake Rotoehu since its establishment in the lake around 2000. This exotic pest plant is surface reaching in large parts of this shallow lake making it a perfect candidate for mechanical harvesting.
As part of the Te Arawa - Rotorua Lakes Programme the Lake Rotoehu Action Plan sets out nutrient reduction targets for nitrogen and phosphorus. Realising these targets is integral if lake water quality is to be restored to the trophic level index (TLI) target for Lake
Rotoehu. Restoration measures have included land use management efforts to arrest nutrient inputs, phosphorus locking through alum dosing, floating wetlands, and most recently the deployment of two aerators. To date the most successful in-lake nutrient reduction method has been mechanical harvest of hornwort.
Aquatic weed harvesting has resulted in reaching a significant portion of the annual nutrient target for the lake catchment. Attaining this level of nutrient removal has manifested in tangible water quality gains in the past few years. Most noticeable is the reduction in cyanobacterial (blue-green) algal blooms which had been prevalent in the lake in summer months. We discuss the practicalities and problems of submerged lake weed harvesting, disposal options, and impacts of this activity on the lake.

year: 2015