Immobilized artificial membrane chromatography : quantitative structure-retention relationships of structurally diverse drugs

The chromatographic capacity factors (log k‘) for 32 structurally diverse drugs were determined by high performance liquid chromatography (HPLC) on a stationary phase composed of phospholipids, the so-called immobilized artificial membrane (IAM). In addition, quantitative structure-retention relationships (QSRR) were developed in order to explain the dependence of retention on the chemical structure of the neutral, acidic, and basic drugs considered in this study. The obtained retention data were modeled by means of multiple regression analysis (MLR) and partial least squares (PLS) techniques. The structures of the compounds under study were characterized by means of calculated physicochemical properties and several nonempirical descriptors. For the carboxylic compounds included in the analysis, the obtained results suggest that the IAM-retention is governed by hydrophobicity factors followed by electronic effects due to polarizability in second place. Further, from the analysis of the results obtained of two developed quantitative structure-permeability studies for 20 miscellaneous carboxylic compounds, it may be concluded that the balance between polarizability and hydrophobic effects is not the same toward IAM phases and biological membranes. These results suggest that the IAM phases could not be a suitable model in assessing the acid-membrane interactions. However, it is not possible to generalize this observation, and further work in this area needs to be done to obtain a full understanding of the partitioning of carboxylic compounds in biological membranes. For the non-carboxylic compounds included in the analysis, this work shows that the hydrophobic factors are of prime importance for the IAM-retention of these compounds, while the specific polar interactions, such as electron pair donor−acceptor interactions and electrostatic interactions, are also involved, but they are not dominant.

Wayfarersʼ tales : reflecting on the doctoral journey

This paper provides a temporal snapshot of two midterm PhD candidates as they both grapple with paradigms and methodology, research questions, external challenges within the research field, locating their voices as doctoral students, and maintaining energy and focus to continue their doctoral journey. These two candidates, one of whom is interstate, share the same supervisor and have come to know each other through telephone reading groups, email communications, and face-to-face meetings with their supervisor, and attending conferences and other collegial opportunities. The catalyst for this paper was a reading group discussion of a paper by Pirrie and Macleod (2010, p. 367) applying the descriptors of ʻjourneyman, wayfarer, fellow traveller or craftsmanʼ to the conceptualisation of the identities of researchers at temporal moments in the research process. We were also inspired by Kamler and Thomsonʼs (2001) paper where they respond to each otherʼs emails in a conversation formulating ideas and perspectives about ʻwriting upʼ research. Additionally, we have considered the work of Ryan, Amorim and Kusch (2010) and Lindsay, Kell, Ouellette and Westall (2010). We have linked their work on reflective learning to our experience of reflecting ʻaloudʼ in a supportive learning community and our subsequent individual reflexive learning. At the heart of our reflections is a relationship between supervisor (Jennifer) and doctoral candidates (Christine and Cheryl); the relationship is a fluid community of practice (Wenger, 1998). A community of practice that depends not so much on direction from the supervisor, but rather as a space where concepts and ideas can be spoken aloud in a safe, critical and supportive environment. Members are able to listen, both to themselves and to each other, before reflecting and finding their own way. At other times each juggles their own professional and personal identities as they become teacher, journeyman, fellow traveller and recalcitrant.