Biomedical subjects
John M Sanderson
Publications and source records attributed to John M Sanderson.
Micellar aggregates formed following the addition of hexafluoroisopropanol to phospholipid membranes.
The addition of 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) to aqueous phospholipid membranes leads to perturbation of the bilayer. In the case of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), calorimetric and small-angle X-ray scattering analyses indicate that effects are already apparent at bound molar HFIP/lipid ratios of less than 1:150, with a pronounced decrease in the temperature of the main (gel to liquid crystalline) phase transition and a decrease in the intensity of the first- and second-order scattering reflections. As the HFIP concentration is raised further, at bound molar HFIP/lipid ratios >2:1, uniform isotropic particulate structures are formed with higher intrinsic curvature than the parent liposomes. These observations are supported by the results of thin-film experiments and are consistent with the formation of DMPC/HFIP adducts that are detergent-like in nature. In the case of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) the effects are much less marked, with no blebbing observed over a comparable range of HFIP concentrations. Although HFIP interacts strongly with DOPC membranes, it appears that membrane rupture is not promoted as readily with this lipid. Data from electron microscopy, laser correlation spectroscopy, and marker release experiments suggest that some of the immediate (nonequilibrium) effects of HFIP on membranes are the consequence of microinhomogeneity in water/HFIP mixtures. On the basis of our observations, we propose a model for the interaction of HFIP with phospholipid membranes.
Peptide-lipid interactions: insights and perspectives.
As the number of membrane proteins in the Protein Data Bank increases, efforts to understand how they interact with their natural environment are increasing in importance. A number of membrane proteins crystallise with lipid molecules implicitly bound at discrete locations that are consistent with the transmembrane regions of the protein. Bioinformatics studies also point to the specific interactions of some amino acids with membrane lipids. The results of experiments using model systems are revealing how these interactions contribute to the stability of both the protein and the membrane in which it is embedded. From a different perspective, the processes involved in the binding of peptides to membrane surfaces to produce a variety of effects are being understood in ever-increasing detail. This review describes current research efforts and thinking in this area.
The synthesis of peptides and proteins containing non-natural amino acids.
Methods for the incorporation of non-natural amino acids into proteins have advanced significantly over recent years and in this tutorial review we aim to give a general overview of the area. These techniques offer the possibility of modulating the structures and functions of proteins and thus permit the generation of novel designed systems for both biocatalytic and mechanistic studies. Four complementary approaches are discussed in detail along with examples of their application. The advantages and disadvantages of each technique are also discussed.
Analysis of liposomal membrane composition using Raman tweezers.
We have developed a methodology for the analysis of liposomal membranes and their contents using near-IR Raman spectroscopy on liposomes held in an optical trap. We were able to detect a variety of membrane components including lipids, cholesterol, and small molecule solutes such as ethanol, DMSO and hexafluoroisopropanol. The methodology is able to distinguish between solutes that equilibrate across the liposomal membrane from those that partition selectively into the lipid bilayer.
The design, synthesis and characterisation of channel-forming peptides.
Synthetic peptides designed using criteria derived from statistical analyses of beta-barrel membrane proteins form channels in synthetic membranes at very low peptide:lipid ratios.