An exploration of how clinician attitudes and beliefs influence the implementation of lifestyle risk factor management in primary healthcare: a grounded theory study

Background

Given the current emphasis on networks as vehicles for innovation and change in health service delivery, the ability to conceptualise and measure organisational enablers for the social construction of knowledge merits attention. This study aimed to develop a composite tool to measure the organisational context for evidence-based practice (EBP) in healthcare.

Methods

A structured search of the major healthcare and management databases for measurement tools from four domains: research utilisation (RU), research activity (RA), knowledge management (KM), and organisational learning (OL). Included studies were reports of the development or use of measurement tools that included organisational factors. Tools were appraised for face and content validity, plus development and testing methods. Measurement tool items were extracted, merged across the four domains, and categorised within a constructed framework describing the absorptive and receptive capacities of organisations.

Results

Thirty measurement tools were identified and appraised. Eighteen tools from the four domains were selected for item extraction and analysis. The constructed framework consists of seven categories relating to three core organisational attributes of vision, leadership, and a learning culture, and four stages of knowledge need, acquisition of new knowledge, knowledge sharing, and knowledge use. Measurement tools from RA or RU domains had more items relating to the categories of leadership, and acquisition of new knowledge; while tools from KM or learning organisation domains had more items relating to vision, learning culture, knowledge need, and knowledge sharing. There was equal emphasis on knowledge use in the different domains.

Conclusion

If the translation of evidence into knowledge is viewed as socially mediated, tools to measure the organisational context of EBP in healthcare could be enhanced by consideration of related concepts from the organisational and management sciences. Comparison of measurement tools across domains suggests that there is scope within EBP for supplementing the current emphasis on human and technical resources to support information uptake and use by individuals. Consideration of measurement tools from the fields of KM and OL shows more content related to social mechanisms to facilitate knowledge recognition, translation, and transfer between individuals and groups.     

Secondary structural analysis of the carboxyl‐terminal domain from different connexin isoforms

The connexin carboxyl‐terminal (CxCT) domain plays a role in the trafficking, localization, and turnover of gap junction channels, as well as the level of gap junction intercellular communication via numerous post‐translational modifications and protein–protein interactions. As a key player in the regulation of gap junctions, the CT presents itself as a target for manipulation intended to modify function. Specific to intrinsically disordered proteins, identifying residues whose secondary structure can be manipulated will be critical toward unlocking the therapeutic potential of the CxCT domain. To accomplish this goal, we used biophysical methods to characterize CxCT domains attached to their fourth transmembrane domain (TM4). Circular dichroism and nuclear magnetic resonance were complementary in demonstrating the connexin isoforms that form the greatest amount of α‐helical structure in their CT domain (Cx45 > Cx43 > Cx32 > Cx50 > Cx37 ≈ Cx40 ≈ Cx26). Studies compared the influence of 2,2,2‐trifluoroethanol, pH, phosphorylation, and mutations (Cx32, X‐linked Charcot‐Marie Tooth disease; Cx26, hearing loss) on the TM4‐CxCT structure. While pH modestly influences the CT structure, a major structural change was associated with phosphomimetic substitutions. Since most connexin CT domains are phosphorylated throughout their life cycle, studies of phospho‐TM4‐CxCT isoforms will be critical toward understanding the role that structure plays in regulating gap junction function. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 143–162, 2016.     

Effects of Phosphorylation on the Structure and Backbone Dynamics of the Intrinsically Disordered Connexin43 C-terminal Domain

Phosphorylation of the connexin43 C-terminal (Cx43CT) domain regulates gap junction intercellular communication. However, an understanding of the mechanisms by which phosphorylation exerts its effects is lacking. Here, we test the hypothesis that phosphorylation regulates Cx43 gap junction intercellular communication by mediating structural changes in the C-terminal domain. Circular dichroism and nuclear magnetic resonance were used to characterize the effects of phosphorylation on the secondary structure and backbone dynamics of soluble and membrane-tethered Cx43CT domains. Cx43CT phospho-mimetic isoforms, which have Asp substitutions at specific Ser/Tyr sites, revealed phosphorylation alters the α-helical content of the Cx43CT domain only when attached to the membrane. The changes in secondary structure are due to variations in the conformational preference and backbone flexibility of residues adjacent and distal to the site(s) of modification. In addition to the known direct effects of phosphorylation on molecular partner interactions, the data presented here suggest phosphorylation may also indirectly regulate binding affinity by altering the conformational preference of the Cx43CT domain.     

Purification and reconstitution of the connexin43 carboxyl terminus attached to the 4th transmembrane domain in detergent micelles

In recent years, reports have identified that many eukaryotic proteins contain disordered regions spanning greater than 30 consecutive residues in length. In particular, a number of these intrinsically disordered regions occur in the cytoplasmic segments of plasma membrane proteins. These intrinsically disordered regions play important roles in cell signaling events, as they are sites for protein–protein interactions and phosphorylation. Unfortunately, in many crystallographic studies of membrane proteins, these domains are removed because they hinder the crystallization process. Therefore, a purification procedure was developed to enable the biophysical and structural characterization of these intrinsically disordered regions while still associated with the lipid environment. The carboxyl terminal domain from the gap junction protein connexin43 attached to the 4th transmembrane domain (TM4-Cx43CT) was used as a model system (residues G178-I382). The purification was optimized for structural analysis by nuclear magnetic resonance (NMR) because this method is well suited for small membrane proteins and proteins that lack a well-structured three-dimensional fold. The TM4-Cx43CT was purified to homogeneity with a yield of 6 mg/L from C41(DE3) bacterial cells, reconstituted in the anionic detergent 1-palmitoyl-2-hydroxy-sn-glycero-3-[phospho-RAC-(1-glycerol)], and analyzed by circular dichroism and NMR to demonstrate that the TM4-Cx43CT was properly folded into a functional conformation by its ability to form α-helical structure and associate with a known binding partner, the c-Src SH3 domain, respectively.     

Enrichment of Escherichia coli proteins by column chromatography on reactive dye columns

The reliable identification and analysis of the low abundance proteins expressed by a cell remains a key challenge in the study of cellular proteomes. The analysis of low abundance proteins is a particular problem when using two-dimensional gel electrophoresis (2-DE) to resolve the cellular proteins since the technology is unable to display the wide dynamic range of protein levels typically synthesized by cells. We have investigated the use of reactive dye compounds for the enrichment of low abundance cellular proteins prior to analysis by 2-DE. The capacity of reactive dye compounds to bind specific protein species was used as the basis for a general chromatographic tool for protein enrichment. Six reactive dye compounds were investigated in detail for the analysis of Escherichia coli proteins. Whole bacterial cell lysates were passed down columns prepared with the reactive dye compounds. The bound proteins were eluted with 1.5 M NaCl and analyzed by 2-DE. Distinctive protein profiles were observed for the bound proteins recovered from the different reactive dye compounds. Selected proteins enriched by these methods were identified by peptide mass mapping. The enrichment procedure developed using reactive dye compounds were used to investigate acid-induced changes in the proteome of E. coli grown at either pH 7.0 or pH 5.8. Increased levels of expression were observed for a number of proteins (for example, GdhA, PanC, ProC, TkrA, EF-TS and YodA) were observed for E. coli grown at pH 5.8. Five identified proteins (AroG, FabI, GlyA, PurA and EF-Tu) showed reduced levels of synthesis for bacteria grown at pH 5.8 compared to pH 7.0. In the case of PanC and FabI the altered expression profiles were only reliably demonstrated using the enrichment protocols. One theme emerging from these data was that the expression of proteins concerned with one-carbon metabolism was perturbed at pH 5.8, which may point to a previously unrecognized affect of low pH stress on the physiology of E. coli cells. We conclude that the prefractionation of cell lysates on reactive dye columns will serve as a valuable generic tool for the analysis of low abundance proteins expressed by both prokaryotic and eukaryotic cells.     

1H, 13C, and 15N backbone resonance assignments of the connexin43 carboxyl terminal domain attached to the 4th transmembrane domain in detergent micelles

Gap junctions are specialized membrane channels that enable coordination of cellular functions and whole-organ responses by facilitating both molecular and electrical communication between neighboring cells. Connexin43 (Cx43) is the most widely expressed and well-studied gap junction protein. In the heart, Cx43 is essential for normal cardiac development and function. Studies using a soluble version of the Cx43 carboxyl-terminal domain (Cx43CT; S255-I382) have established the central role it plays in channel regulation. However, in purifying and characterizing a more ‘native-like’ construct (Cx43CT attached to the fourth transmembrane domain (TM4-Cx43CT; D196-I382)), we have identified that the TM4-Cx43CT is a better model than the soluble Cx43CT to further investigate the mechanisms governing Cx43 channel regulation. Here, we report the backbone ¹H, ¹⁵N, and ¹³C assignments and predicted secondary structure of the TM4-Cx43CT. Assignment of the TM4-Cx43CT is a key step towards a better understanding of the structural basis of Cx43 regulation, which will lead to improved strategies for modulation of junctional communication that has been altered due to disease or ischemic injury.