Biomedical subjects

Frances Separovic

Publications and source records attributed to Frances Separovic.

21 records · Page 2Linked to original sources

PubMed2003

Interaction of antimicrobial peptides from Australian amphibians with lipid membranes.

Solid-state NMR and CD spectroscopy were used to study the effect of antimicrobial peptides (aurein 1.2, citropin 1.1, maculatin 1.1 and caerin 1.1) from Australian tree frogs on phospholipid membranes. 31P NMR results revealed some effect on the phospholipid headgroups when the peptides interact with DMPC/DHPC (dimyristoylphosphatidylcholine/dihexanoylphosphatidylcholine) bicelles and aligned DMPC multilayers. 2H NMR showed a small effect of the peptides on the acyl chains of DMPC in bicelles or aligned multilayers, suggesting interaction with the membrane surface for the shorter peptides and partial insertion for the longer peptides. 15N NMR of selectively labelled peptides in aligned membranes and oriented CD spectra indicated an alpha-helical conformation with helix long axis approximately 50 degrees to the bilayer surface at high peptide concentrations. The peptides did not appear to insert deeply into PC membranes, which may explain why these positively charged peptides preferentially lyse bacterial rather than eucaryotic cells.

Amino Acid Sequence↗

PubMed2003

Solid-state NMR structure determination.

Biological applications of solid-state NMR (SS-NMR) have been predominantly in the area of model membrane systems. Increasingly the focus has been membrane peptides and proteins. SS-NMR is able to provide information about how the peptides or proteins interact with the lipids or other peptides/proteins in the membrane, their effect on the membrane and the location of the peptides or proteins relative to the membrane surface. Recent developments in biological SS-NMR have been made possible by improvements in labelling and NMR techniques. This review discusses aligned systems and magic angle spinning techniques, bilayers and bicelles, and measurement of chemical shift anisotropy and dipolar coupling. A number of specific experiments such as cross polarization, rotational resonance, REDOR, PISEMA, MAOSS and multidimensional experiments are described. In addition to 2H, 13C and 15N, recent solid-sate 1H, 19F and 17O NMR work is discussed. Several examples of the use of SS-NMR to determine the structure of membrane peptides and proteins are given.

Anisotropy↗

PubMed2002

A solid-state NMR study of protein mobility in lyophilized protein-sugar powders.

The molecular mobility of protein in lyophilized lysozyme-sugar systems stored at different relative humidities was studied using solid-state NMR. Relaxation measurements, T(1) of high-frequency (MHz), and T(1rho), of low-frequency (kHz) motions, were performed on lysozyme lyophilized with lactose and trehalose. Molecular aggregation and enzymatic activity of the protein were determined using HPLC and bioassays. An increase in hydration had little effect on the T(1rho) values of pure lysozyme, trehalose, lactose, trehalose-lysozyme, and lysozyme at low lactose concentrations. The T(1) values of pure sugar increased as moisture content increased. The presence of both sugars led to increased T(1) values of the lysozyme but increasing hydration gradually reduced T(1) values. When a larger amount of lactose was lyophilized with lysozyme, longer T(1) (and T(1rho)) values were seen for lactose than for lysozyme. Although longer T(1) values were related to an increase in protein stability, the effect of crystallization and sugar type appeared to be major contributing factors. Trehalose and lactose decreased relaxation rates in the lysozyme-sugar systems while hydration increased relaxation rates that were correlated with changes in aggregation and activity of the protein.

Carbohydrates↗