Thermodynamic characterization of the palm tree Roystonea regia peroxidase stability

The structural stability of a peroxidase, a dimeric protein from royal palm tree (Roystonea regia) leaves, has been characterized by high-sensitivity differential scanning calorimetry, circular dichroism, steady-state tryptophan fluorescence and analytical ultracentifugation under different solvent conditions. It is shown that the thermal and chemical (using guanidine hydrochloride (Gdn-HCl)) folding/unfolding of royal palm tree peroxidase (RPTP) at pH 7 is a reversible process involving a highly cooperative transition between the folded dimer and unfolded monomers, with a free stabilization energy of about 23 kcal per mol of monomer at 25 degrees C. The structural stability of RPTP is pH-dependent. At pH 3, where ion pairs have disappeared due to protonation, the thermally induced denaturation of RPTP is irreversible and strongly dependent upon the scan rate, suggesting that this process is under kinetic control. Moreover, thermally induced transitions at this pH value are dependent on the protein concentration, allowing it to be concluded that in solution RPTP behaves as dimer, which undergoes thermal denaturation coupled with dissociation. Analysis of the kinetic parameters of RPTP denaturation at pH 3 was accomplished on the basis of the simple kinetic scheme N ->(k) D, where k is a first-order kinetic constant that changes with temperature, as given by the Arrhenius equation; N is the native state, and D is the denatured state, and thermodynamic information was obtained by extrapolation of the kinetic transition parameters to an infinite heating rate. Obtained in this way, the value of RPTP stability at 25 degrees C is ca. 8 kcal per mole of monomer lower than at pH 7. In all probability, this quantity reflects the contribution of ion pair interactions to the structural stability of RPTP. From a comparison of the stability of RPTP with other plant peroxidases it is proposed that one of the main factors responsible for the unusually high stability of RPTP which enhances its potential use for biotechnological purposes, is its dimerization. (c) 2008 Elsevier Masson SAS. All rights reserved.

Cr3+ and Cr4+ luminescence in glass ceramic silica

This paper reports on the effect of glass ceramic silica matrix on [CrO4](4-) and Cr2O3 NIR and visible luminescence. Chromium-containing silica was obtained by precipitation from water-glass and chromium nitrate acid solution with thermal treatment at 1000 degrees C. From XRD results silica and silica-chromium samples are crystalline. The chromium emission spectrum presents two main broad bands: one in the NIR region (1.1-1.7 mu m) and other in the visible region (0.6-0.7 mu m) assigned to Cr4+ and to Cr3+, respectively. This thermal treated glass ceramic silica-chromium sample stabilizes the [CrO4](4-) where Cr4+ substitutes for Si4+ and also hexacoordinated Cr3+ group probably as segregated phase in the system. It can be pointed out that luminescence spectroscopy is a powerful toot for detecting the two chromium optical centers in the glass ceramic silica. (C) 2008 Elsevier B.V. All rights reserved.

Crystal structure and statistical coupling analysis of highly glycosylated peroxidase from royal palm tree (Roystonea regia)

Royal palm tree peroxidase (RPTP) is a very stable enzyme in regards to acidity, temperature, H(2)O(2), and organic solvents. Thus, RPTP is a promising candidate for developing H(2)O(2)-sensitive biosensors for diverse applications in industry and analytical chemistry. RPTP belongs to the family of class III secretory plant peroxidases, which include horseradish peroxidase isozyme C, soybean and peanut peroxidases. Here we report the X-ray structure of native RPTP isolated from royal palm tree (Roystonea regia) refined to a resolution of 1.85 angstrom. RPTP has the same overall folding pattern of the plant peroxidase superfamily, and it contains one heme group and two calcium-binding sites in similar locations. The three-dimensional structure of RPTP was solved for a hydroperoxide complex state, and it revealed a bound 2-(N-morpholino) ethanesulfonic acid molecule (MES) positioned at a putative substrate-binding secondary site. Nine N-glycosylation sites are clearly defined in the RPTP electron-density maps, revealing for the first time conformations of the glycan chains of this highly glycosylated enzyme. Furthermore, statistical coupling analysis (SCA) of the plant peroxidase superfamily was performed. This sequence-based method identified a set of evolutionarily conserved sites that mapped to regions surrounding the heme prosthetic group. The SCA matrix also predicted a set of energetically coupled residues that are involved in the maintenance of the structural folding of plant peroxidases. The combination of crystallographic data and SCA analysis provides information about the key structural elements that could contribute to explaining the unique stability of RPTP. (C) 2009 Elsevier Inc. All rights reserved.

In Situ Infrared (FTIR) Study of the Mechanism of the Borohydride Oxidation Reaction on Smooth Pt Electrode

Although Pt has been thoroughly studied regarding its activity for the borohydride oxidation reaction (BOR), the BOR mechanism at Pt remains unclear: Depending on the applied potential, spontaneous BH(4)(-) hydrolysis can compete with the direct BOR. The goal of the present work is to provide more insight into the behavior of smooth Pt electrodes toward the BOR, by coupling in situ infrared reflectance spectroscopy with electrochemistry. The measurements were performed on a Pt electrode in 1 M NaOH/1 M NaBH(4), so as to detect the reaction intermediate species generated as a function of the applied potential. Several bands were monitored in the B-H ((v) over bar approximate to 1180, 1080, and 972 cm(-1)) and B-O ((v) over bar = 1325 and similar to 1425 cm(-1)) bond regions upon increased electrode polarization. These absorption bands, which appear sequentially and were already detected for similar measurements on Au electrodes, are assigned to BH(3), BH(2), and BO(2)(-) species. In light of these experimental data and previous results obtained in our group for Pt- or Au-based electrodes, possible initial elementary steps of the BOR on platinum electrodes are proposed and discussed according to the relevant literature data.

Mass transport effects in the borohydride oxidation reaction-Influence of the residence time on the reaction onset and faradaic efficiency

The borohydride oxidation reaction (BOR) was studied on Pt and Au electrodes by cyclic voltammetry in dilute alkaline borohydride solutions (0.1 M NaOH + 10(-3) mol L(-1) NaBH(4)). More specifically, the electrodes were considered as either Vulcan XC72-supported Pt or Au (noted as Pt/C and Au/C, respectively) active layers or smooth Pt or Au surfaces, the latter possibly being covered by a layer of (non-metalized) Vulcan XC72 carbon powder. The BOR onset potential and the number of electrons (n(e-)) exchanged per BH(4)(-) anion (faradaic efficiency) were investigated for these electrodes, to determine whether the residence time of reaction intermediates (at the electrode surface or inside the porous layer) does influence the overall reaction pathway/completion. For the carbon-supported platinum, n(e-) strongly depends on the thickness of the active layer. While thin (ca. 0.5 mu m-thick) Pt/C active layers yield n(e-) < 4, thick layers (approximately 3 mu m) yield n(e-)approximate to 8, which can be ascribed to the sufficient residence time of the molecules formed within the active layer (H(2), by heterogeneous hydrolysis, or BOR intermediates) enabling further (near-complete) oxidation. This puts into evidence that not only the nature of the electrocatalyst is important to reach high BOR efficiency, but also the structure/thickness of the active layer. The same trend applies for Au/C active layers and for smooth Pt or Au surfaces covered with a layer of (inactive) Vulcan XC72. In addition, the BOR onset usually shifts negative when the reaction intermediates are trapped, which suggests that some of the intermediates are more easily oxidized than BH(4)(-) itself; based on literature data, BH(3)OH(-) species is a likely candidate. (C) 2011 Elsevier B.V. All rights reserved.

Getting below the surface of the principal recruitment 'crisis' in New Zealand primary schools

Since 1989 in New Zealand, the work of the primary school principal has been transformed in official policy texts from that of leading professional to chief executive officer. Surveys document the changing nature of the role and the workload and other pressures that have resulted, particularly for principals with teaching responsibilities in smaller schools. There is a generally accepted crisis of preparation, recruitment, development and retention. Below the surface, however, are deeper-seated, structural difficulties: women comprise the majority of teachers, yet are a minority of principals and their career advancement is largely limited to small schools and those in poorer socioeconomic areas. This article reviews the situation and examines the reasons why dominant images of the primary school principalship may be both partial and counterproductive.

Towards a Protocol for the Attachment of Semantic Descriptions to Grid Services

Service discovery in large scale, open distributed systems is difficult because of the need to filter out services suitable to the task at hand from a potentially huge pool of possibilities. Semantic descriptions have been advocated as the key to expressive service discovery, but the most commonly used service descriptions and registry protocols do not support such descriptions in a general manner. In this paper, we present a protocol, its implementation and an API for registering semantic service descriptions and other task/user-specific metadata, and for discovering services according to these. Our approach is based on a mechanism for attaching structured and unstructured metadata, which we show to be applicable to multiple registry technologies. The result is an extremely flexible service registry that can be the basis of a sophisticated semantically-enhanced service discovery engine, an essential component of a Semantic Grid.

Governance in rural communities: the case of Victoria

State and federal government policies for rural areas have encouraged local people and organizations to play a greater role in the provision of their local services. This emphasis on local participation has been described as a shift from ‘government’ to ‘governance’. However while there is an emerging research around small towns in Australia there is very little known about the processes of community governance. This paper focuses on local development groups in small towns in rural Victoria that have emerged or have been reconstituted with a broader community focus following municipal amalgamations. The basic aim of this paper is analyse to what degree these local community development groups can be regarded as constituting a form of community governance and the implications this has for democracy and accountability in small rural areas. The paper begins with a discussion of community governance as it represented in the literature. We then analyse ten case studies from across Victoria in the light of the changing political context.

Performance appraisals in Australian universities- imposing a managerialistic framework into a collegial culture

As a result of federal government pressure in the late 1980’s Australian universities now find themselves embracing managerial practices at the expense of their traditional collegial practices. The application of managerialism into the
university sector has seen the inculcation of business practices, including the widespread application of performance appraisals, into an environment which has in the past, been self-regulatory. Performance appraisals as a tool of managerialism, have provided university administrators with a mechanism which provides a sense of compliance with private sector practices. But has it worked? This paper examines the nature of performance appraisals and its usage within one university and questions how successful the introduction of such practices has been. In doing so, it identifi es areas of further research.

Crossing boundaries between learning and research : doctoral programs at a distance

Australian distance education, from school to university contexts, typically concerns teaching people the knowledge, values and skills that constitute their chosen courses of study; whereas doctoral courses principally concern candidates learning how to produce – through producing – significant original new knowledge. This paper considers the history and contemporary practices of Australian off-campus doctoral education and argues that these are at the forefront internationally. It is argued that understanding the provision of quality doctoral education at a distance requires a form of conceptual boundary crossing by policymakers, distance educators, and (especially) doctoral education practitioners, in order to develop and/or enhance future practices.

Who are they? A profile of complainants about advertising in Australia

Advertising expenditure in Australia has almost doubled in the last 10 years even though some advertisements maybe ''unacceptable." We investigated consumer complaint responses specifically within the area of advertising in Australia. Our findings indicate that these complainants to be older, more highly educated and more likely to be female, than the population at large.

Prevalence of genital human papillomavirus DNA in a sample of senior school-aged women in the Australian Capital Territory

Background: A strong association between persistent infection with oncogenic types of human papillomavirus (HPV) and cervical cancer is well established. Small numbers of international studies examining adolescent HPV infection and the risk factors associated are published, but there is currently no evidence on the prevalence and risk factors for HPV in an Australian, sexually active female adolescent population. Methods: To provide prevalence and risk factors for HPV in a female sexually active, senior high school population in the Australian Capital Territory (ACT), a convenience sample of 161, 16–19-year-old females attending a senior high school was evaluated. The sample formed part of a larger sample recruited for a study of sexually transmitted infections and blood-borne viruses in senior high school students. A clinical record was used to collect information about sexual and other risk behaviours, while self-collected vaginal swabs were tested for HPV DNA detection and genotyping using polymerase chain reaction. Results: The prevalence of HPV DNA in this sample overall was 11.2%, with multiple genotypes in 38%. No statistically significant associations were found between HPV DNA and the number of male partners, age of coitarche, time since first sexually active, condom use, smoking or alcohol intake. Conclusions: This is the first Australian study that has examined the prevalence and risk factors for genital HPV in this demographic group. The prevalence of HPV infection is slightly lower than reported in similar age groups overseas and is lower than other Australian studies in older women and those attending sexual health centres. Of HPV-positive young women, high-risk genotypes were found in over half, with more than one-third of HPV existing as multiple genotypes. Large community-based prevalence studies are needed to guide the development of recommendations for the vaccination of young women against HPV and to support other health promotion initiatives.

The glue that binds : workplace climate, human resource systems and performance

There is now a substantial body of research examining the relationship between human resources (HR) and organisational performance. During the last decade, this research has focused on the impacts of ‘bundles’ of HR practices. While researchers have consistently found a significant relationship between HR systems and performance, the mechanisms that give rise to this relationship remain poorly conceptualised. Building on the work of Barney (1998), Ferris et al. (1998) and Bowen and Ostroff (2004) we suggest the social context in which such practices are implemented provide the basis for specifying these transmission mechanisms. Workplace climate provides a key social context that induces high levels of effort and dynamic efficiency. Using a large sample we find workplace climate significantly influences the relationship between HR systems and performance.