title: Purification and characterization of a thermostable proteinase isolated from Thermus sp. strain Rt41A

authors: Peek, Keith

subjects: enzyme

abstract: Thermus sp. strain Rt41A produces an extracellular thermostable alkaline proteinase. The enzyme has a high isoelectric point (10.25–10.5) which can be exploited in purification by using cation-exchange chromatography. The proteinase was purified to homogeneity and has a molecular mass of 32.5 kDa by SDS/PAGE. It is a glycoprotein, containing 0.7% carbohydrate as glucose equivalents, and has four half-cystine residues present as two disulphide bonds. Maximum proteolytic activity was observed at pH 8.0 against azocasein and greater than 75% of this activity was retained in the pH range 7.0–10.0. Substrate inhibition was observed with casein and azocasein. The enzyme was stable in the pH range 5.0–10.0 and maximum activity, in a 10-min assay, was observed at 90°C with 5 mM CaCl2 present. No loss of activity was observed after 24 h at 70°C and the half-lives at 80°C and 90°C were 13.5 h and 20 min, respectively. Removal of Ca2+ reduced the temperature for maximum proteolytic activity against azocasein to 60°C and the half-life at 70°C was 2.85 min. The enzyme was stable at low and high ionic strength and in the presence of denaturing reagents and organic solvents.
Rt41A proteinase cleaved a number of synthetic amino acid p-nitrophenol esters, the kinetic data indicating that small aliphatic or aromatic amino acids were the preferred residue at the P1 position. The kinetic data for the hydrolysis of a number of peptide p-nitroanilide substrates are also reported. Primary cleavage of the oxidized insulin B chain occurred at sites where the P1′ amino acid was aromatic. Minor cleavage sites (24 h incubation) were for amino acids with aliphatic side chains at the P1′ position. The esterase and insulin cleavage data indicate the specificity is similar for both the P1 and P1′ sites.

text: Purification and characterization of a thermostable proteinase isolated from Thermus sp. strain Rt41A Thermus sp. strain Rt41A produces an extracellular thermostable alkaline proteinase. The enzyme has a high isoelectric point (10.25–10.5) which can be exploited in purification by using cation-exchange chromatography. The proteinase was purified to homogeneity and has a molecular mass of 32.5 kDa by SDS/PAGE. It is a glycoprotein, containing 0.7% carbohydrate as glucose equivalents, and has four half-cystine residues present as two disulphide bonds. Maximum proteolytic activity was observed at pH 8.0 against azocasein and greater than 75% of this activity was retained in the pH range 7.0–10.0. Substrate inhibition was observed with casein and azocasein. The enzyme was stable in the pH range 5.0–10.0 and maximum activity, in a 10-min assay, was observed at 90°C with 5 mM CaCl2 present. No loss of activity was observed after 24 h at 70°C and the half-lives at 80°C and 90°C were 13.5 h and 20 min, respectively. Removal of Ca2+ reduced the temperature for maximum proteolytic activity against azocasein to 60°C and the half-life at 70°C was 2.85 min. The enzyme was stable at low and high ionic strength and in the presence of denaturing reagents and organic solvents.
Rt41A proteinase cleaved a number of synthetic amino acid p-nitrophenol esters, the kinetic data indicating that small aliphatic or aromatic amino acids were the preferred residue at the P1 position. The kinetic data for the hydrolysis of a number of peptide p-nitroanilide substrates are also reported. Primary cleavage of the oxidized insulin B chain occurred at sites where the P1′ amino acid was aromatic. Minor cleavage sites (24 h incubation) were for amino acids with aliphatic side chains at the P1′ position. The esterase and insulin cleavage data indicate the specificity is similar for both the P1 and P1′ sites.

year: 1992

title: Do Golden Parachutes increase CEO’s DESIRE to be taken over? empirical evidence from australia and united states

authors: Reddy, Krishna

subjects: change in control payments

abstract: This study investigates whether the large payouts that are available to Chief Executive Officers (CEOs) from a change in corporate control (takeover) do motivate some CEOs to seek acquisition of their firms by making them more attractive to a takeover bid. Using Australian and the US data, employing OLS regression, we report that there is a significant relationship between a CEOs change in control payments and their firm’s net cash levels (one of the key factors of takeover attractiveness). Our empirical results also indicate that CEOs desire their firms to be acquired by decreasing shareholders’ equity, thus supporting the view that change in control payments exist primarily for incumbent managers. Our findings provide support to the proposition that managers enjoy having large cash balances to be available to them as it allows them with greater opportunities to derive personal benefit from it. Therefore, our findings suggest that managers prefer to have large cash balances available to them to ensure their future wellbeing by setting up favourable terms in the control agreements.

text: Do Golden Parachutes increase CEO’s DESIRE to be taken over? empirical evidence from australia and united states This study investigates whether the large payouts that are available to Chief Executive Officers (CEOs) from a change in corporate control (takeover) do motivate some CEOs to seek acquisition of their firms by making them more attractive to a takeover bid. Using Australian and the US data, employing OLS regression, we report that there is a significant relationship between a CEOs change in control payments and their firm’s net cash levels (one of the key factors of takeover attractiveness). Our empirical results also indicate that CEOs desire their firms to be acquired by decreasing shareholders’ equity, thus supporting the view that change in control payments exist primarily for incumbent managers. Our findings provide support to the proposition that managers enjoy having large cash balances to be available to them as it allows them with greater opportunities to derive personal benefit from it. Therefore, our findings suggest that managers prefer to have large cash balances available to them to ensure their future wellbeing by setting up favourable terms in the control agreements.

year: 2012

title: Place responsive and culturally responsive outdoor education in secondary schools: Examining teachers' perspectives and experiences

authors: Skipworth, Andrew James

subjects: place responsive

abstract: Sustainability, place and human connectedness have increasingly become the focus of research and professional dialogue in school-based outdoor education in Aotearoa New Zealand. These developments challenge traditional practices that privilege adventure and individualistic outcomes in outdoor education. At the same time, the implementation of culturally responsive practices within many secondary schools has further challenged teachers of outdoor education to ensure that pedagogical approaches and outcomes meet the needs of their diverse student population. An increasing number of educators appear to have adopted place responsive and culturally responsive pedagogies within their outdoor education programmes or units of work at the senior school level, yet there is limited research examining teachers’ perceptions and experiences in doing so.
Adopting an interpretive framework, and using qualitative research methods, this research focuses on the challenges faced and opportunities presented when secondary school teachers in Aotearoa New Zealand adopt place and culturally responsive pedagogies in outdoor education. Six teachers of senior level outdoor education from schools spread throughout Aotearoa New Zealand shared their stories. An inductive analysis of the interviews identified these teachers faced ongoing challenges with adopting new pedagogies in outdoor education, which was in part because many colleagues held perceptions that outdoor education was less important than other subjects and was primarily about having fun. In addition, the complexities of assessment at the senior level meant that teachers often faced challenges in formally assessing student learning. Teachers also found that undertaking change required shifts in mind-set which were further supported by targeted professional development, engagement in post-graduate study and talking with like-minded teachers. However, teachers’ adoption of place and culturally responsive approaches generated notable opportunities to align to the front end of the New Zealand curriculum, promote the holistic development of students and nurture cultural diversity.
This study highlights that undertaking curriculum and pedagogical change in outdoor education in secondary schools is a complex process, which is greatly influenced by the attitudes and perceptions of others. The potential alignment of place responsive and culturally responsive pedagogies became apparent, as did the need for more targeted professional development for teachers of outdoor education. Teachers’ adoption of these pedagogies also highlighted a greater capacity for authentic outdoor education experiences for students that also strengthened a commitment to their bicultural partnerships in schools. As the nature of education changes in schools, contemporary pedagogies in outdoor education have the potential to enhance the capacity of schools to facilitate learning that will meet the diverse needs of learners in Aotearoa New Zealand.

text: Place responsive and culturally responsive outdoor education in secondary schools: Examining teachers' perspectives and experiences Sustainability, place and human connectedness have increasingly become the focus of research and professional dialogue in school-based outdoor education in Aotearoa New Zealand. These developments challenge traditional practices that privilege adventure and individualistic outcomes in outdoor education. At the same time, the implementation of culturally responsive practices within many secondary schools has further challenged teachers of outdoor education to ensure that pedagogical approaches and outcomes meet the needs of their diverse student population. An increasing number of educators appear to have adopted place responsive and culturally responsive pedagogies within their outdoor education programmes or units of work at the senior school level, yet there is limited research examining teachers’ perceptions and experiences in doing so.
Adopting an interpretive framework, and using qualitative research methods, this research focuses on the challenges faced and opportunities presented when secondary school teachers in Aotearoa New Zealand adopt place and culturally responsive pedagogies in outdoor education. Six teachers of senior level outdoor education from schools spread throughout Aotearoa New Zealand shared their stories. An inductive analysis of the interviews identified these teachers faced ongoing challenges with adopting new pedagogies in outdoor education, which was in part because many colleagues held perceptions that outdoor education was less important than other subjects and was primarily about having fun. In addition, the complexities of assessment at the senior level meant that teachers often faced challenges in formally assessing student learning. Teachers also found that undertaking change required shifts in mind-set which were further supported by targeted professional development, engagement in post-graduate study and talking with like-minded teachers. However, teachers’ adoption of place and culturally responsive approaches generated notable opportunities to align to the front end of the New Zealand curriculum, promote the holistic development of students and nurture cultural diversity.
This study highlights that undertaking curriculum and pedagogical change in outdoor education in secondary schools is a complex process, which is greatly influenced by the attitudes and perceptions of others. The potential alignment of place responsive and culturally responsive pedagogies became apparent, as did the need for more targeted professional development for teachers of outdoor education. Teachers’ adoption of these pedagogies also highlighted a greater capacity for authentic outdoor education experiences for students that also strengthened a commitment to their bicultural partnerships in schools. As the nature of education changes in schools, contemporary pedagogies in outdoor education have the potential to enhance the capacity of schools to facilitate learning that will meet the diverse needs of learners in Aotearoa New Zealand.

year: 2017