Energetics of protein-cyclodextrin interactions

The energetics of interaction of a range of cyclodextrins with folded and unfolded proteins has been examined by sensitive microcalorimetry techniques. Weak interaction with exposed amino acid residues promotes unfolding and dissociation of proteins. The possibility that such interactions may facilitate the use of cyclodextrins as ''chaperone-mimics'' in the refolding of denatured protein has been explored with the enzyme phosphoglycerate kinase. Up to 40% regain of activity can be achieved in some cases

Involvement of water in carbohydrate-protein binding

The interactions of trimannosides 1 and 2 with Con A were studied to reveal the effects of displacement of well-ordered water molecules on the thermodynamic parameters of protein- ligand complexation. Trisaccharide 2 is a derivative of 1. in which the hydroxyl at C-2 of the central mannose unit is replaced by a hydroxyethyl moiety. Upon binding, this moiety displaces a conserved water molecule present in the Con A binding site. Structural studies by NMR spectroscopy and MD simulations showed that the two compounds have very similar solution conformational properties. MD simulations of the complexes of Con A with 1 and 2 demonstrated that the hydroxyethyl side chain of 2 can establish the same hydrogen bonds in a low energy conformation with the protein binding site as those mediated by the water molecule in the complex of 1 with Con A. Isothermal titration microcalorimetry (ITC) measurements showed that 2 has a more favorable entropy of binding compared to 1. This term, which was expected, arises from the return of the highly ordered water molecule to bulk solution. The favorable entropy term was, however, offset by a relatively large unfavorable enthalpy term. This observation was rationalized by comparing the extent of hydrogen bond and solvation changes during binding. It is proposed that an indirect interaction through a water molecule will provide a larger number of hydrogen bonds in the complex that have higher occupancies than in bulk solution, thereby stabilizing the complex

Bactericidal action of high-power Nd:YAG laser light on <i>Escherichia coli</i> in saline suspension

Infra-red light (1064 nm) from a high-power Nd:YAG laser caused more than 90% loss of viability of &lt;i&gt;Escherichia coli&lt;/i&gt; during exposures that raised the temperature of PBS suspensions of the bacteria to 50 °C in a thermocouple-equipped cuvette. In contrast, there was minimal loss of viability after heating the same suspensions to 50 °C in a water-bath, or in a PCR thermal cycler. The mechanism of laser killing at 50 °C was explored by differential scanning calorimetry, by laser treatment of transparent and turbid bacterial suspensions, and by optical absorbancy studies of E. coli suspensions at 1064 nm. Taken together, the data suggested that the bactericidal action of Nd:YAG laser light at 50 °C was due partly to thermal heating and partly to an additional, as yet undefined, mechanism. Scanning electron microscopy revealed localized areas of surface damage on laser-exposed &lt;i&gt;E. Coli&lt;/i&gt; cells

Synthesis and conformational analysis of a conformationnally constrained trisaccharide and complexation properties with Concanavalin A

International audienc

Acetonitrile-induced unfolding of porcine pepsin A: a proposal for a critical role of hydration structures in conformational stability

In order to increase understanding of the basis of the stability of the native conformational state of porcine pepsin A, a strategy based on induction and monitoring of protein denaturation was developed. Structural perturbation was achieved by adding acetonitrile (MeCN) to the protein-solvent system. MeCN was found to induce non-coincident disruption of the secondary and tertiary structural features of pepsin A. It is proposed that gross unfolding is prompted by disruption of the protein hydration pattern induced by the organic co-solvent. It should be noted that the functional properties and thermal stability of the protein were already impaired before the onset of global unfolding. Low and intermediate contents of MeCN in the protein-solvent system affected the sharpness of the thermal transition and the degree of residual structure of the heat-denatured state. The importance of hydration to the conformational stability of pepsin A in its biologically active state is discusse

Public health decision makers’ informational needs and preferences for receiving research evidence

Objectives: The purpose of this study was to identify decision-makers’ preferences for the transfer and exchange of research knowledge. This article is focused on how the participants define evidence-based decision-making and their preferences for receiving research evidence to integrate into the decision-making process. Methods: Semistructured interviews were conducted with a purposive sample of 16 Ontario public health decision-makers from six Ontario public health units in this fundamental qualitative descriptive study. The sample included nine program managers, six directors, and one Medical Officer of Health. Participants were asked to define the term evidence-based decision-making and identify preferred research dissemination strategies. The interviews were audio-taped, transcribed verbatim, and coded for emerging concepts. Results: Participants defined evidence-based decision-making as a process whereby multiple sources of information were consulted before making a decision concerning the provision of services. To facilitate integration of research evidence into the decision-making process, public health administrators appreciate receiving, in both electronic and hard copy, systematic reviews, executive summaries of research, and clear statements of implications for practice from health service researchers. Conclusions: Although consensus exists among participants concerning the definition of evidence based public health decision-making, ongoing efforts are required to continue to promote the use of research evidence in program planning and public health policy. It is also important to continue to improve the ease with which public health decision-makers access systematic reviews, as well as to ensure the relevance and applicability of the results to the practice setting