Structural and biochemical characterisation of the oxidoreductase NmDsbA3 from Neisseria meningitidis

DsbA is an enzyme found in the periplasm of Gram-negative bacteria that catalyses the formation of disulfide bonds in a diverse array of protein substrates, many of which are involved in bacterial pathogenesis. Whilst most bacteria possess only a single essential DsbA, Neisseria meningitidis is unusual in that it possesses three DsbAs, although the reason for this additional redundancy is unclear. Two of these N. meningitidis enzymes (NmDsbA1 and NmDsbA2) play an important role in meningococcal attachment to human epithelial cells, whilst NmDsbA3 is considered to have a narrow substrate repertoire. To begin to address the role of DsbAs in the pathogenesis of N. meningitidis, we have determined the structure of NmDsbA3 to 2.3 Å resolution. Although the sequence identity between NmDsbA3 and other DsbAs is low, the NmDsbA3 structure adopted a DsbA-like fold. Consistent with this finding, we demonstrated that NmDsbA3 acts as a thiol-disulfide oxidoreductase in vitro and is reoxidised by Escherichia coli DsbB (EcDsbB). However, pronounced differences in the structures between DsbA3 and EcDsbA, which are clustered around the active site of the enzyme, suggested a structural basis for the unusual substrate specificity that is observed for NmDsbA3.

Disorganized attachment and reproductive strategies

Del Giudice provides an extension of the life history theory of attachment that incorporates emerging data suggestive of sex differences in avoidant male and preoccupied female attachment patterns emerging in middle childhood. This commentary considers the place of disorganized attachment within this theory and why male children may be more prone to disorganized attachment by drawing on Trivers’s parental investment theory.

Dislodgment and attachment strength of the intertidal macroalga Hormosira banksii (Fucales, Phaeophyceae)

Hormosira banksii is a dominant intertidal alga characterised by limited dispersal of propagules, yet it has a broad distribution throughout temperate Australasia. However, the high abundance of beach wrack of H. banksii on sandy beaches along southwest Victoria, the frequency of frond dislodgment and the force required to break it from the substratum remain unknown. Dislodgment of macroalgae has been shown to influence dispersal processes; therefore, we tested the model that long-distance dispersal of H. banksii is facilitated by weak attachment to the substratum and frequent dislodgment of fertile fronds. We monitored the dislodgment of H. banksii individuals and conducted in situ pull tests to determine the attachment strength of fronds of H. banksii. We further tested whether thallus size or pull direction influenced attachment strength of H. banksii. We found that breakage of vesicles and fronds was a regular event during the survey period and that the mean attachment strength of fronds of H. banksii was weak compared to other intertidal algae. Furthermore, we found that thallus size did not influence the force required to break fronds of H.banksii from the substratum but that the direction that fronds were pulled from the substratum did. We suggest that fronds of H. banksii do drift frequently and that long-distance dispersal is likely to be an important mechanism for the distributional success of this species.

Water quality, bacterial flora and production in shrimp farms in Sri Lanka

This study investigated the possibilities of improvement in the brackish water shrimp culture industry in Sri Lanka. Feeding rates could be further reduced without negative effect on shrimp growth while improving effluent water quality. Improvements of feed quality and pond management practices were also suggested.

Adults with arthritic conditions and care-seeking in an attachment framework

This thesis investigated the role of care-seeking amongst adults with arthritis, using an attachment framework to help explain the inconsistent results of previous studies in regard to psychological adjustment to a chronic illness. The results highlight the importance of attachment processes in partially influencing care-seeking and coping strategies that shape psychological adjustment. The portfolio addresses the frequent co-occurence of depression with chronic medical disorders. This impacts the ability for chronic, medically ill adults to engage in self-management strategies. Four case studies are presented.

Internet child pornography : an examination of attachment and intimacy deficits

This study found that Internet child pornographers (ICP) reported significantly less optimal attachment than non-offenders, matched child and matched adult sexual offenders. ICP also reported a more negative view of self than non-offenders and the matched sexual offender groups. Finally, the ICP group reported more social avoidance and distress than non-offenders. The portfolio explores the influence of treatment readiness on the best practice principles when working with violent offenders in relation to their assessment, and subsequent treatment recommendations. The importance of treatment readiness and its utility in relation to these principles is highlighted in four case studies.

Attachment as a predictor of leadership and follower outcomes

Research has suggested that effective leadership, specifically the utilisation of transformational leadership behaviours, is heavily entrenched in a leader’s interpersonal skills. However, few studies have investigated the interpersonal factors that drive appropriate use of transformational and transactional leadership in leader-follower settings. Attachment theory provides a robust framework in which to chart the developmental precursors of effective leadership that underpin positive leader-follower relationships and potential organisational outcomes. In this study, 46 manager-non manager dyads recruited from a Victorian education institution, a national telecommunications company and a Victorian real-estate business (managers – Mean age = 48.5 years, SD = 7.78, non-managers – Mean age 43.92 years, SD = 8.72) took part in an online questionnaire. Participants completed measures of attachment, leadership behaviour and organisational citizenship behaviour. Path analysis revealed that manager’s attachment style significantly predicted follower ratings of transformational and transactional leadership behaviours. Additionally, follower ratings of leadership were associated with organisational citizenship behaviour. Thus, it is concluded that attachment theory provides a valid framework in which to understand follower perceptions of leadership behaviour and subsequent organisational outcomes. These findings are discussed within the context of attachment theory and the leadership literature.

A novel romance : conceptualising emotional attachment as a barrier to adoption

The Technology Acceptance Model (TAM) aims to understand consumers’ adoption of new technologies. Some 30 years after TAM was first proposed, it is still widely used today. This paper proposes an extended version of the TAM, with the primary addition to it being the construct of consumers’ emotional attachment to an existing product. The expanded TAM, Technology Acceptance Model with Emotional Attachment (TAME), is applied to the understudied area of e-book reader technology and its adoption by consumers who read for pleasure versus for academic purposes, as has been the focus of past research on e-book readers. The extended model considers consumers’ emotional attachment to paper books (pbooks) as a likely barrier to the take up of e-book reader technology.

Rethinking attachment : fostering positive relationships between infants, toddlers and their primary caregivers

This article provides a synthesis of current theory and research in relation to attachment between infants/toddlers and their caregivers. Worldwide statistics show that there are a significant number of women working in the global labour market. In Australia, recent research also found that over 300,000 children aged 0-5 years are currently attending long day child care, and a child can spend up to 12,500 hours in child care before starting school (based on attendance of 50 hours per week for five years). In order to understand the importance of developing secure relationships that build on the first transition from home to child-care centre, semi-structured interviews were conducted to collect views from parents and child-care staff. Results showed that most participants in the sample were in favour of using a primary caregiver approach. Implications for the implementation of this approach will be discussed.

Immobilization of bacterial recombinant proteins

Recombinant α-L Rhamnosidase has several potential applications in citrus fruit juice processing industries. Immobilized recombinant α-L Rhamnosidase further provides an added advantage to this industrially important enzyme. Various techniques have been used to immobilize native rhamnosidase from fungal origin and applications were explored in great details by several workers. (Puri et al., 1996, 2000, 2001)

A recombinant rhamnosidase from a bacterial source was expressed in E.coli has been immobilized in calcium alginate beads (entrapment method). A batch bioreactor was created for the hydrolysis of naringin using immobilized recombinant α-L Rhamnosidase under shaking and stationary conditions and it was found to hydrolyze naringin effectively. The system was efficient to hydrolyze narigin under shaking conditions and was operationally stable up to 9 days. A high percent hydrolysis of naringin was achieved at pH 7.5 and 60˚C by immobilized rhamnosidase. Entrapped rhamnosidase was able to hydrolyze naringin content in kinnow juice repeatedly and this feature makes this technique economically suitable for debittering of fruit juices.