Marcus Jack Swann

Publications (54) View all

• Article: Measurement of conformational changes in the structure of transglutaminase on binding calcium ions using optical evanescent dual polarisation interferometry.

  K Karim, J D Taylor, D C Cullen, M J Swann, N J Freeman
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  ABSTRACT: The conformational changes occurring when the protein transglutaminase binds calcium ions have been studied using the optical evanescent technique of dual polarization interferometry (DPI) implemented via a dual slab waveguide structure. Immobilized transglutaminase layers of 4-5 nm in thickness were obtained, which when challenged with calcium ions underwent a contraction of approximately 0.5 nm (depending on the concentration of calcium) and an increase in refractive index of approximately 1 x 10-2. The affinity constant for the calcium binding was found to be in the range of 0.95 +/- 0.2 mM. The results reported are in good agreement with those found in the literature obtained by other techniques. It has also been shown that the structural changes occurring during the binding event are considerably larger than the mass changes that take place; thus, DPI offers a potentially valuable method to study real-time structural changes occurring to proteins when they bind metal ions.
  Analytical Chemistry 05/2007; 79(8):3023-31. · 5.86 Impact Factor
• Article: Quantifying the effects of melittin on liposomes.

  J F Popplewell, M J Swann, N J Freeman, C McDonnell, R C Ford
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  ABSTRACT: Melittin, the soluble peptide of bee venom, has been demonstrated to induce lysis of phospholipid liposomes. We have investigated the dependence of the lytic activity of melittin on lipid composition. The lysis of liposomes, measured by following their mass and dimensions when immobilised on a solid substrate, was close to zero when the negatively charged lipids phosphatidyl glycerol or phosphatidyl serine were used as the phospholipid component of the liposome. Whilst there was significant binding of melittin to the liposomes, there was little net change in their diameter with melittin binding reversed upon salt injection. For the zwitterionic phosphatidyl choline the lytic ability of melittin is dependent on the degree of acyl chain unsaturation, with melittin able to induce lysis of liposomes in the liquid crystalline state, whilst those in the gel state showed strong resistance to lysis. By directly measuring the dimensions and mass changes of liposomes on exposure to melittin using Dual Polarisation Interferometry, rather than following the florescence of entrapped dyes we attained further information about the initial stages of melittin binding to liposomes.
  Biochimica et Biophysica Acta 02/2007; 1768(1):13-20. · 4.66 Impact Factor
• Source

  Available from: S. Brand

  Article: The metrics of surface adsorbed small molecules on the Young's fringe dual-slab waveguide interferometer.

  G. H. Cross, A. Reeves, S. Brand, M J Swann, L. L. Peel, N. J. Freeman, J. R. Lu
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  ABSTRACT: A method for analysing thin films using a dual-waveguide interferometric technique is described. Alternate dual polarization addressing of the interferometer sensor using a ferroelectric liquid crystal polarization switch allowed the opto-geometrical properties (density and thickness) of adsorbed layers at a solid-liquid interface to be determined. Differences in the waveguide mode dispersion between the transverse electric and transverse magnetic modes allowed unique combinations of layer thickness and refractive index to be determined at all stages; of the layer formation process. The technique has been verified by comparing the analysis of the surface adsorption of surfactants with data obtained using neutron scattering techniques, observing their behaviour on trimethylsilane coated silicon oxynitride surfaces. The data obtained were found to be in excellent agreement with analogous neutron scattering experiments and the precision of the measurements taken to be of the order of 40 pm with respect to adsorbed layer thicknesses. The study was extended to a series of surfactants whose layer morphology could be correlated with their hydrophilicity/lipophilicity balance. Those in the series with longer alkyl chains were observed to form thinner, denser layers at the hydrophobic solid/aqueous liquid interface and the degree of order attained at sub-critical micelle concentrations to be correlated with molecular fluidity. The technique is expected to find utility with those interested in thin film analysis. An important and growing area of application is within the life sciences, especially in the field of protein structure and function.
  Journal of Physics D Applied Physics 04/2004; 37(1):74-80. · 2.54 Impact Factor
• Article: Real time, high resolution studies of protein adsorption and structure at the solid-liquid interface using dual polarization interferometry

  NJ Freeman, LL Peel, MJ Swann, GH Cross, A Reeves, S Brand, JR Lu
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  ABSTRACT: A novel method for the analysis of thin biological films, called dual polarization interferometry (DPI), is described. This high resolution (<1 Angstrom), laboratory-based technique allows the thickness and refractive index (density) of biological molecules adsorbing or reacting at the solid-liquid interface to be measured in real time (up to 10 measurements per second). Results from the adsorption of bovine serum albumin (BSA) on to a silicon oxynitride chip surface are presented to demonstrate how time dependent molecular behaviour can be examined using DPI. Mechanistic and structural information relating to the adsorption process is obtained as a function of the solution pH.
  Journal of Physics Condensed Matter 01/2004; 16(26):S2493-S2496. · 2.55 Impact Factor
• Article: Temporal and spatial profiling of the modification of an electroactive polymeric interface using neutron reflectivity.

  A Glidle, L Bailey, C S Hadyoon, A R Hillman, A Jackson, K S Ryder, P M Saville, M J Swann, J R Webster, R W Wilson, J M Cooper
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  ABSTRACT: Electropolymerized films of the functionalized pyrrole, pentafluorophenyl-3-(pyrrol-1-yl)propionate (PFP), were reacted with a solution-phase nucleophile, ferrocene ethylamine. This reaction was chosen as a model representative of a postdeposition modification of the polymer membrane's properties. For the first time, a nondestructive method for direct chemical analysis of the reaction profile within the electrodeposited polymer membrane after nucleophilic substitution is presented. This was achieved through the application of in situ neutron reflectivity with supplementary analytical information concerning the film's chemical composition obtained from XPS, FT-IR, and electrochemical measurements. The results presented illustrate how, for a partially reacted film resulting from a short reaction time, the extent of reaction with ferrocene ethylamine is not homogeneous throughout the thickness of the film, but occurs predominantly at the polymer/solution interface. We show that the progress of the reaction within the polymer film is limited by the transport of reacting species in the dense regions of the membrane that are furthest from the solution interface. The data do not fit an alternative model in which there is spatially homogeneous progression of the reaction front throughout the bulk of the thin film polymer. Guided by the neutron reflectivity measurements, suitable modifications were made to the electrodeposition method to prepare films whose architecture resulted in faster rates of reaction.
  Analytical Chemistry 12/2001; 73(22):5596-606. · 5.86 Impact Factor