Excellence in Research Australia (ERA) - Collection - UQ eSpace

Absorption and fluorescence spectroscopy of rhodamine 6G in titanium dioxide nanocomposites

2007-08-15T00:00:00Z

A comparison has been made between the spectroscopic properties of the laser dye rhodamine 6G (R6G) in mesostructured titanium dioxide (TiO2) and in ethanol. Steady-state excitation and emission techniques have been used to probe the dye-matrix interactions. We show that the TiO2-nanocomposite studied is a good host for R6G, as it allows high dye concentrations, while keeping dye molecules isolated, and preventing aggregation. Our findings have important implications in the context of solid state dye-lasers and microphotonic device applications. (C) 2003 Elsevier B.V. All rights reserved.

Abstand, Ausbau, creativity and ludicity in Australian English

Sussex, Roland — 2007-08-15T00:00:00Z

The social history of a language or variety, and its emergence, consolidation and stabiliza tion, allow us to combine the formal data of the language (principally its sound structure, grammar and lexis) with the external conditions in which they have evolved. The advance of Australian English in terms of its differentiation (Kloss's abstand) and elaboration of roles (Kloss's ausbau) pose problems of chronology, periodization, description and expla nation. This paper extends the conventional scope of abstand and ausbau to the analysis of the social history of Australian English. It argues that two factors are central to the emerging identification of Australian English: creativity, in the sense of morphological innovation, especially here in diminutives like reffo ('refugee') and pollie ('politician'); and in ludicity, defined as a deep-rooted playfulness with language. While these character istics are only part of the overall dynamics of the social history of Australian English, the evidence is sufficiently extensive to warrant further investigation. An earlier version of this paper was given at the Mitchell Symposium at Macquarie University on 26 April 2002 under the title ‘E pluribus plures? Diversity and integrity in Australian English’. I am grateful to members of the Symposium, and to two anonymous reviewers, for valuable comments and criticism

Abstraction and figuration in monuments and counter-monuments

Strakosch, Elizabeth — 2010-03-04T00:00:00Z

Abstract 3304: Psychometric Evaluation of Two Coronary Heart Disease HRQL Questionnaires in Chinese Patients

2009-03-23T00:00:00Z

Objectives: To evaluate the psychometric properties of two HRQL questionnaires - Myocardial Infarction Dimensional Assessment Scale (MIDAS) and the MacNew HRQL Questionnaire (MacNew) - in Chinese patients with coronary heart disease. Methods: Conforming to the guidelines of the Medical Outcomes Trust (2002), we examined item-internal consistency, stability, concurrent, discriminative and construct validity, and a conceptual model of the Chinese versions of the MIDAS and MacNew instruments. Results: Data were obtained from 393 patients with either myocardial infarction (n = 131), angina (n = 165) or heart failure (n = 102), with 92 of them repeating completion of the questionnaires seven days later for testing stability. Cronbach’s alphas (MIDAS, r = 0.73 – 0.94; MacNew subscales, r = 0.88 – 0.93) supported their item-internal consistency and test-retest reliability exceeded ICC > 0.75 for both. Concurrent and construct validity for the MIDAS and MacNew subscales were supported by their moderate to high correlations with most of the Short Form 36 Health Survey subscales and the Hospital Anxiety and Depression Scale, except that the diet, medication and side effect subscales of MIDAS showed lower correlations. Discriminative validity of the MIDAS and MacNew subscales was demonstrated with poorer HRQL in female patients (p <.001), those with psychiatric morbidity (p <.001) and those with health deterioration (p <.001). Results of confirmatory factor analysis supported the original seven-factor and three-factor structure of the MIDAS and MacNew, respectively, with five items of the MacNew loading significantly on only one but not two subscales as proposed by the original version. Conclusion: The MacNew and the MIDAS are psychometrically sound when used in Chinese patients with coronary heart disease. The problematic subscales of the MIDAS may be related to their small number of items (≤ 3) and cultural variations in perceiving disease management.

Abstract specification in Object-Z and CSP

Smith, G. P. og Derrick, J. — 2007-08-24T00:00:00Z

A number of integrations of the state-based specification language Object-Z and the process algebra CSP have been proposed in recent years. In developing such integrations, a number of semantic decisions have to be made. In particular, what happens when an operation's precondition is not satisfied? Is the operation blocked, i.e., prevented from occurring, or can it occur with an undefined result? Also, are outputs from operations angelic, satisfying the environment's constraints on them, or are they demonic and not influenced by the environment at all? In this paper we discuss the differences between the models, and show that by adopting a blocking model of preconditions together with an angelic model of outputs one can specify systems at higher levels of abstraction.

Abundance and ecophysiology of Defluviicoccus spp., glycogen-accumulating organisms in full-scale wastewater treatment processes

2008-02-18T00:00:00Z

A bureaucratic cinema: The fraught relationship between government and film.

Goldsmith, Ben — 2009-06-09T00:00:00Z

Abwassertechnik am Scheideweg : Entsorgung oder Wertstoffgewinnung

Wilderer P.A. — 2009-02-17T00:00:00Z

Tag für Tag befreit uns ein sanfter Druck auf die Spültaste von dem stinkenden gelb-braunen Süppchen, das wir „Unser Abwasser“ nennen. Wasser aus Duschen, Spül- und Wachmaschinen kommt hinzu. Auf seinem Weg durch kilometerlange, unterirdisch verlegte Rohrleitungen vereinigt sich dieses „Unser Abwasser“ mit Abläufen aus Gewerbebetrieben und Industrieanlagen. So entsteht schließlich eine heterogene Mischung aus gelösten und partikulären Substanzen organischer und anorganischer Natur. Dieses Stoffgemisch zu entwirren und aus dem Abwasser wieder abzuscheiden, ist die Aufgabe der Kläranlage. Es entsteht so aber nicht nur gereinigtes Abwasser, sondern auch das Konzentrat dessen, was zuvor im Abwasser enthalten war, Klärschlamm nämlich. Über dessen Entsorgungsmöglichkeiten reden sich bereits Generationen von Ingenieuren, Landwirten, Umweltschützern und Kommunalpolitikern die Köpfe heiß. Ist die Technik der Abwasserbehandlung, wie sie sich über die zurückliegenden 150 Jahre hinweg in den Industriestaaten entwickelt hat, eigentlich noch zeitgemäß?

Academia Nuts by Michael Wilding

Hergenhan, L. T. — 2007-08-15T00:00:00Z

Academia - Shaping future pharmacists

Nissen, Lisa — 2008-09-01T00:00:00Z

Academic journal publishing: Desiderata for the digital age

Petelin, Roslyn — 2007-08-15T00:00:00Z

The consumption of academic journals has radically changed over the past decade, explains the author. While there has been an exponential rise in published scholarship, spiralling costs for commercial journals have caused cutbacks in subscriptions to academic journals by institutional libraries and raised calls for free online access to unpublished work that scholars have produced. The rise of the Internet has facilitated a concomitant growth in online scholarship. What, asks the author, are the promises on online scholarship?

Academic managers and ethics: A question of making the right decision

2007-08-23T00:00:00Z

Academic medical centers and conflicts of interest

Ting, Joseph Yuk Sang — 2006-07-31T00:00:00Z

The author suggests a combination of educational outreach, clinical audits, mailed feedback of prescribing data, interactive peer group meetings, problem-based learning, and dissemination of prescribing guidelines to improve evidence-based general practitioner prescribing.

Academic medicine: The evidence base

2007-08-15T00:00:00Z

The International Campaign to Revitalise Academic Medicine recognises that an evidence based approach is important in discussing the problems of academic medicine. A preliminary exploration of the evidence on academic medicine has led to a research agenda for examining and proposing realistic solutions. Copyright © 2004, BMJ Publishing Group Ltd.

Academic Performance of International Students in Electrical Engineering at the University of Queensland

Lovell, Brian C. — 2004-02-25T00:00:00Z

In this paper we study the academic performance of the large cohort of international students enrolled in the Bachelor of Engineering (Electrical) program at the University of Queensland. The need for this study arises from the extremely rapid internationalisation of the Electrical Engineering program over the past five years and the possible consequences of this growth on graduate quality. We conclude that the international students perform as well as, if not better than, domestic students. Thus international student quality does not appear to represent a major limiting factor when examining limits to program growth.

Academics researching in schools - making first contact

Sim, Cheryl Rae og McCluskey, Kerryn Gail — 2010-01-13T00:00:00Z

It is almost one hundred years since Dewey stated that the purpose of research in all its forms and disciplines was an “effort to understand and help others understand what teachers and learners do during the process of learning and what this means potentially for the education of teachers” (Dewey, 1904/1974). Early in 2003 the author of this paper began a research study that investigates the development of relationships between teacher mentors and preservice teachers. The aim of the study seeks to examine the extent to which the concept of community of practice influences the construction of professional identity through the situated learning of preservice teachers in selected school settings. Associated with this aim is to identify the potential for 'communities of practice' to address the anxiety of teachers in the context of seemingly overwhelming levels of change in education and society affecting their professional roles and identities right now. Ironically the researchers found that the anxieties of teachers actually affected their efforts to entice schools and teachers to be involved in the study. This paper focuses on this first stage of the research study. It examines the dilemmas experienced by the researchers as they endeavoured to encourage schools and teachers to participate in the research. It raises issues about the relationship between academics in teacher education and schools and how we can facilitate teachers’ involvement in future research in schools.

Acadmeic performatnce of medical students attending rural clincal schools: a comparison of 3rd year medical students attending rural or urban clincal schools in Queensland

2007-08-23T00:00:00Z

A call to arms at the end of history: a discourse-historical analysis of George W. Bush's declaration of war on terror

2007-08-15T00:00:00Z

In this article we take a discourse-historical approach to illustrate the significance of George W Bush's (2001) declaration of a 'war on terror'. We present four exemplary 'call to arms' speeches by Pope Urban 11 (1095), Queen Elizabeth I (1588), Adolf Hitler (1938) and George W Bush (2001) to exemplify the structure, function, and historical significance of such texts in western societies over the last millennium. We identify four generic features that have endured in such texts throughout this period: (i) an appeal to a legitimate power source that is external to the orator, and which is presented as inherently good; (ii) an appeal to the historical importance of the culture in which the discourse is situated; (iii) the construction of a thoroughly evil Other; and (iv) an appeal for unification behind the legitimating external power source. We argue further that such texts typically appear in historical contexts characterized by deep crises in political legitimacy.

A calreticulin-like protein from endoparasitoid venom fluid is involved in host hemocyte inactivation

2007-08-15T00:00:00Z

During oviposition, most endoparasitoid wasps inject maternal factors into their hosts to interfere with host immune reactions and ensure successful development of their progeny. Since encapsulation is a major cellular defensive response of insects against intruding parasites, parasitoids have developed numerous mechanisms to suppress the host encapsulation capability by interfering with every step in the process, including recognition, adherence and spreading. In previous studies, components of Cotesia rubecula venom were shown to inhibit melanization of host hemolymph by interfering with the prophenoloxidase activation cascade and facilitate expression of polydnavirus genes. Here we report the isolation and characterization of another venom protein with similarity to calreticulin. Results indicate that C rubecula calreticulin (CrCRT) inhibits hemocyte spreading behavior, thus preventing encapsulation of the developing parasitoid. It is possible that the protein might function as an antagonist competing for binding sites with the host hemocyte calreticulin, which mediates early-encapsulation reactions. (c) 2005 Elsevier Ltd. All rights reserved.

A canonical FtsZ protein in Verrucomicrobium spinosum, a member of the bacterial phylum Verrucomicrobia that also includes tubulin-producing Prosthecobacter species

2008-02-18T00:00:00Z

A canonical toolkit for modelling plant function

Renton, M. og Hanan, J. S. og Burrage, K. — 2007-08-23T20:08:14Z

A canopy architectural model to study the competitive ability of chickpea with sowthistle

2009-04-08T00:00:00Z

A Capacity-building approach to health literacy through the use of information communication technologies

2009-01-16T00:00:00Z

A carbon activation model with application to longan seed char gasification

2007-08-15T00:00:00Z

In this paper a new structural model is presented to describe the evolution of porosity of char during the gasification process. The model assumes the char structure to be composed of bundles of parallel graphite layers, and the reactivities of each layer with the gasification agent are assumed to be different to represent the different degree of heterogeneity of each layer (i.e. each layer will react with the gasification agent at a different rate). It is this difference in the reactivity that allows micropores to be created during the course of gasification. This simple structural model enables the evolution of pore volume, pore geometrical surface area and the pore size distribution to be described with respect to the extent of char burn-off. The model is tested against the experimental data of gasification of longan seed-derived char with carbon dioxide and it is found that the agreement between the model and the data is reasonably satisfactory, especially the evolution of surface area and pore volume with burn-off.

A cardiovascular life history: A life course analysis of the original Framingham Heart Study cohort

2007-10-17T10:37:24Z

A C5a receptor antagonist provides greater protection than an NSAID in a skin pouch model of sodium urate induced inflammation

2008-02-18T00:00:00Z

A case-control study of risk factors of early childhood caries

2009-12-10T00:00:00Z

A case for including popular culture in literacy education for young adults with Down syndrome

Moni, K. B. og Jobling, A. — 2009-01-27T17:20:59Z

Popular culture has been part of English and literacy studies in Australia for several years. However, the issue of the inclusion of popular culture in literacy education for young adults with Down syndrome has been marginalised. Using examples of engagement with popular culture by young adults with Down syndrome attending a post-school literacy program, the authors argue that educators need to take note of the role popular culture plays in the lives of these young adults. In the second part of the article, suggestions are given for including popular culture texts in literacy programs for young adults with Down syndrome in the senior years of high school and in post-school settings.

A case for intervention? Physical activity behaviour in an urban sample of middle-to-high income Northeast Mexicans

Gilson, N. D. — 2009-02-19T00:00:00Z

Gilson evaluates the need for physical activity (PA) intervention in a select group of urban, middle-to-high income men and women from the Northeast of Mexico. This was undertaken by assessing the extent to which the sample fulfilled contemporary PA criteria. Results show that all subjects reported an income greater than 5 times the national minimum, classifying the sample within the middle-to-high socio-economic cohort of Mexico.

A Case for Investigating the Ethics of Artificial Life?

2004-02-12T00:00:00Z

A major stream of Artificial Life (ALife) research aims to build synthetic life forms, operating in virtual worlds, implemented as computer programs. A clear long-term target for this research is the evolution of digital life-forms with a complexity of structure and behaviour analogous to biological life-forms, potentially exhibiting intelligence and self-awareness. The creation of intelligent, self-aware digital life-forms has clear ethical implications, but there is no current research into how these ethical issues might be addressed. This paper argues that such ethical research is needed. Furthermore, it describes our future research plans to build a solid philosophical foundation for the consideration of these ethical issues.

A case in variant in cow's milk is atherogenic

2007-08-15T00:00:00Z

Casein is a major protein in cow's milk that occurs in several variant forms, two of which are beta-casein A(1) and beta-casein A(2). The levels of these two proteins vary considerably in milk dependent on the breed of cow, and epidemiology studies suggest that there is a relationship between their consumption and the degree of atherosclerosis. In the present study, the direct effect of consumption of beta-casein A(1) vs beta-casein A(2) on atherosclerosis development was examined in a rabbit model. Sixty rabbits had their right carotid artery balloon de-endothelialised at t = 0, divided randomly into 10 groups (n = 6 per group), then for 6 weeks fed a diet containing 0, 5, 10 or 20% casein isolate, either beta-casein variant A(1) or A(2) made up to 20% milk protein with whey. Some groups had their diets supplemented with 0.5% cholesterol. Blood samples were collected at t = 0, 3 and 6 weeks and rabbits were sacrificed at t = 6 weeks. In the absence of dietary cholesterol, beta-casein A(1) produced significantly higher (P < 0.05) serum cholesterol, LDL, HDL and triglyceride levels than whey diet alone, which in turn produced higher levels than beta-casein A(2). Rabbits fed beta-casein A(1) had a higher percent surface area of aorta covered by fatty streaks than those fed beta-casein A(2) (5.2+/-0.81 vs 1.1+/-0.39, P < 0.05) and the thickness of the fatty streak lesions in the aortic arch was significantly higher (0.04+/-0.010 vs 0.00, P < 0.05). Similarly, the intima to media ratio (I:M) of the balloon injured carotid arteries in A(1) fed animals (0.77+/-0.07) was higher than in those that consumed A(2) (0.57+/-0.04) or whey (0.58+/-0.04), but this did not reach significance. In the presence of 0.5% dietary cholesterol, the thickness of the aortic arch lesions was higher (P < 0.05) in 5, 10 and 20% casein A(1) fed animals compared with their A(2) counterparts, while other parameters were not significantly different. It is concluded that beta-casein A(1)is atherogenic compared with beta-casein A(2). (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.

A case of imported Plasmodium ovale malaria

2009-04-07T00:00:00Z

A Case of Mistaken Identity Reappraisal of the Species of Hookworms (Ancylostoma) Present in Australia and India

2009-01-15T13:04:22Z

This study serves to clarify the current status of canid and felid Ancylostoma species present in Australia. The morphological identification of A. ceylanicum from cats for the first time in Townsville, Australia, appears to be in error, together with the genetic markers provided for the species. Morphological and genetic data presented herein provide strong evidence that the hookworms from cats in Towsville are not A. ceylanicum as previously identified (i.e. the first report of this species in Australia), but are A. braziliense. Therefore the subsequent genetic markers established for A. ceylanicum in subsequent molecular studies based on these Townsville specimens should also be attributed to A. braziliense. Based on this information, a study of canine hookworm species present in northern India is also in error and it is apparent that the hookworms found in this region are those of A. ceylanicum. The distribution of A. braziliense and A. ceylanicum in the Americas and Asia Pacific region is discussed together with the importance of combining parasite morphology with genetic data for parasite diagnosis in epidemiological studies.

A case of myoepithelial carcinoma displaying biallelic inactivation of the tumour suppressor gene APC in a patient with familial adenomatous polyposis

2007-08-14T00:00:00Z

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder caused by mutation of the APC gene. It is characterised by the appearance of hundreds to thousands of colorectal adenomas in adolescence and the subsequent development of colorectal cancer. Various extracolonic malignancies are associated with FAP, including desmoids and neoplasms of the stomach, duodenum, pancreas, liver, and brain. We present a family affected by FAP with an exon 14 APC mutation displaying two rare extracolonic lesions, a hepatoblastoma and a myoepithelial carcinoma. The hepatoblastoma was found in a male patient aged 2 years. The second lesion, a myoepithelial carcinoma of the right cheek, was found in a female patient aged 14 years. Inactivation of the normal APC allele was demonstrated in this lesion by loss of heterozygosity analysis, thus implicating APC in the initiation or progression of this neoplasm. This is the first reported case of this lesion in a family affected by FAP.

A Case of Nosocomial Legionella pneumophila Pneumonia (Short Communication)

2009-04-08T00:00:00Z

A case of periportal fibrosis in a Sudanese refugee

Daveson , James og Macdonald, Graeme — 2010-02-15T00:00:00Z

A case of traumatic carotid cavernous sinus fistula treated by trans-arterial coil embolisation of the internal carotid artery

Wallace, S. og Coulthard, A. — 2010-03-15T00:00:00Z

A case report on using mixed methods in qualitative research

Langridge, M. og Ahern, K. J. — 2007-08-14T00:00:00Z

A case study in specification and implementation testing

Miller, T. og Strooper, P. A. — 2007-08-23T00:00:00Z

Achieving consistency between a specification and its implementation is an important part of software development In previous work, we have presented a method and tool support for testing a formal specification using animation and then verifying an implementation of that specification. The method is based on a testgraph, which provides a partial model of the application under test. The testgraph is used in combination with an animator to generate test sequences for testing the formal specification. The same testgraph is used during testing to execute those same sequences on the implementation and to ensure that the implementation conforms to the specification. So far, the method and its tool support have been applied to software components that can be accessed through an application programmer interface (API). In this paper, we use an industrially-based case study to discuss the problems associated with applying the method to a software system with a graphical user interface (GUI). In particular, the lack of a standardised interface, as well as controllability and observability problems, make it difficult to automate the testing of the implementation. The method can still be applied, but the amount of testing that can be carried on the implementation is limited by the manual effort involved.

A case study of a high growth metropolitan spill over, sea change and tree change community

Christie, M. J. og Rowe, P. A. — 2007-08-23T00:00:00Z

A case study of a resort destination's rise and fall and rise in line with government intervention

Pike, Steven — 2009-11-20T00:00:00Z

A Case Study of Partial Agenesis of the Corpus Callosum: Audiological Implications

Skinner, Leanne og Hickson, Louise — 2007-08-14T00:00:00Z

This case study presents four and a half years of audiological observations, testing and aural habilitation of a female child with a partial agenesis of the corpus callosum (ACC). The ACC was diagnosed by MRI scan performed at 6 months of age to eliminate neurological causes for the developmental delay. This child was also born with a cleft palate and was diagnosed with Robinow Syndrome at 3 years and 3 months of age. The audiological results showed an improvement in hearing thresholds over the 4-year period. The child’s ophthalmologist also reported an improvement in visual skills over time. The most interesting aspect of the child’s hearing was the discrepancy between the monaural and the binaural results. That is, when assessed binaurally she often presented with a mild to moderate mixed loss and, when assessed monaurally, she showed a moderate to severe mixed loss for the right ear and a severe mixed loss for the left ear. Over time, the discrepancy between the monaural and binaural results changed. When assessed binaurally, the loss decreased to normal low frequency hearing sloping to a mild high frequency loss. When assessed monaurally, the most recent results showed a mild loss for the right ear and a moderate loss for the left ear. This discrepancy between binaural and monaural results was evident for both aided and unaided tests. For the most recent thresholds, the binaural results were consistent with the right monaural thresholds for the first time over the four and a half years. Parental reports of the child’s hearing were consistent with the binaural clinical results. This case indicates the need for audiologists to (1) carefully monitor the hearing of children with ACC, (2) obtain monaural and binaural hearing and aided thresholds results, and (3) compare these children’s functional abilities with the objective test results obtained. This case does question whether hearing aids are appropriate for children with ACC. If hearing aids are deemed to be appropriate, then hearing aids with compression characteristics should be considered.

A Case Study of the New Cooperative Medical System on Financial Production in a Rural Population

2008-05-01T00:00:00Z

A case study of the resolution of paediatric dysphagia following brainstern injury: clinical and instrumental assessment

Morgan, A. og Ward, E. og Murdoch, B. — 2007-08-15T00:00:00Z

The coexistance of a swallowing impairment can severely impact upon the medical condition and recovery of a child with traumatic brain injury [ref.(1): Journal of Head Trauma Rehabilitation 9 (1) (1994) 43]. Limited data exist on the progression or outcome of dysphagia in the paediatric population with brainstem injury. The present prospective study documents the resolution of dysphagia in a 14-year-old female post-brainstem injury using clinical, radiological and endoscopic evaluations of swallowing. The subject presented with a pattern of severe oral-motor and oropharyngeal swallowing impairment post-injury that resolved rapidly for the initial 12 weeks, slowed to gradual progress for weeks 12-20, and then plateaued at 20 weeks post-injury. Whilst a clinically functional swallow was present at 10 months post-injury, radiological examination revealed a number of residual physiological impairments, reduced swallowing efficiency, and reduced independence for feeding, indicating a potential increased risk for aspiration. The data highlight the need for early and continued evaluation and intensive treatment programs, to focus on the underlying physiological swallowing impairment post-brainstem injury, and to help offset any potential deleterious effects of aspiration that may affect patient recovery, such as pneumonia. (C) 2003 Elsevier Ltd. All rights reserved.

A case study of water management on closure of an open pit mining operation in North Queensland, Australia

2007-08-24T00:00:00Z

A case study of young people in Christchurch: A three- year longitudinal study of young people in a co-educational secondary school

2009-03-19T00:00:00Z

A case study on the effect of speed variation on the growth of wear-type rail corrugation

2008-05-16T00:00:00Z

A case study on the numerical simulation of enhanced coalbed methane recovery

2007-08-23T00:00:00Z

A caspase-like gene from Heliothis virescens ascovirus (HvAV-3e) is not involved in apoptosis but is essential for virus replication

Asgari, S. — 2008-02-18T00:00:00Z

Ascoviruses (AVs) are double-stranded DNA viruses causing a fatal disease in lepidopteran host larvae. A unique feature of AV infection is cleavage of host cells into membrane bound vesicles containing the virions. A recent study showed that a caspase from Spodoptera frugiperda AV (SfAV) is directly involved in initiation of apoptosis and eventually cell cleavage. Results shown here indicate that Heliothis virescens AV does not induce apoptosis in host cells. HvAV codes for a caspase-like protein but no apoptosis was observed when the gene was expressed in vitro. RNAi studies indicated that the gene is essential for virus replication. (C) 2007 Elsevier B.V. All rights reserved.

A cassette ligation strategy with thioether replacement of three Gly-Gly peptide bonds: Total chemical synthesis of the 101 residue protein early pregnancy factor [psi(CH2S)(28-29,56-57,76-77)]

2007-08-14T00:00:00Z

The 101 residue protein early pregnancy factor (EPF), also known as human chaperonin 10, was synthesized from four functionalized, but unprotected, peptide segments by a sequential thioether ligation strategy. The approach exploits the differential reactivity of a peptide-NHCH2CH2SH thiolate with XCH2CO-peptides, where X = Cl or I/Br. Initial model studies with short functionalized (but unprotected) peptides showed a significantly faster reaction of a peptide-NHCH2CH2SH thiolate with a BrCH2CO-peptide than with a CICH2CO-peptide, where thiolate displacement of the halide leads to chemoselective formation of a thioether surrogate for the Gly-Gly peptide bond. This rate difference was used as the basis of a novel sequential ligation approach to the synthesis of large polypeptide chains. Thus, ligation of a model bifunctional N-alpha-chloroacetyl, C-terminal thiolated peptide with a second N-alpha-bromoacetyl peptide demonstrated chemoselective bromide displacement by the thiol group. Further investigations showed that the relatively unreactive N-alpha-chloroacetyl peptides could be activated by halide exchange using saturated KI solutions to yield the highly reactive No-iodoacetyl peptides. These findings were used to formulate a sequential thioether ligation strategy for the synthesis of EPF, a 101 amino acid protein containing three Gly-Gly sites approximately equidistantly spaced within the peptide chain. Four peptide segments or cassettes comprising the EPF protein sequence (BrAc-[EPF 78-101] 12, ClAc-[EPF 58-75]-[NHCH2CH2SH] 13, ClAc-[EPF 30-55]-[NHCH2CH2SH] 14, and Ac-[EPF 1-27]-[NHCH2CH2SH] 15) of EPF were synthesized in high yield and purity using Boc SPPS chemistry. In the stepwise sequential ligation strategy, reaction of peptides 12 and 13 was followed by conversion of the N-terminal chloroacetyl functional group to an iodoacetyl, thus activating the product peptide for further ligation with peptide 14. The process of ligation followed by iodoacetyl activation was repeated to yield an analogue of EPF (EPF psi(CH2S)(28-29,56-57,76-77)) 19 in 19% overall yield.