Paramagnetic micelles structure

Rapoport NY, Herron JN, Pitt WG, Pitina L. Micellar delivery of doxorubicin and its paramagnetic analog, rubo l, to HL-60 cells Effect of micelle structure and ultrasoimd on the intracellular drug uptake. J Contr Rel 1999 58 153—162. 

Table 1). The r value of Gd-DOTA(GACi2)2 (Scheme 2) (34.8 mM s at 298 K and 20 MHz) is the highest reported to date for monohydrated Gd-based paramagnetic micelles. Analogously, the incorporation of the two-chain complex into liposomal structures also brings an important relaxivity gain with respect to the mono-chain derivative (-1-135% at 0.47 T and - -99% at 1.41 T). 

McManus, H. J. D., Kang, Y. S., and Kevan, L. (1993). Electron-paramagnetic-resonance and proton matrix electron-nuclear double-resonance studies of N,N,N, N -tetramethylbenzidine photoionization in sodium dodecyl-sulfate micelles— Structural effects of added alcohols. J. Chem. Soc. Faraday Trans., 89,4085-4089. 

Paramagnetic amphiphilic complexes embedded in micelles have their hydrophilic head and thus the paramagnetic ion in contact with the surrounding water. If the complex has only one hydrophobic chain, the access of water to the ion should be easy but when two hydrophobic chains are involved like in DTPA bisamides complexes, the incorporation of both chains in the micellar structure could reduce either the accessibility of water to the ion or the water exchange rate. It has been reported that micellar Gd-DOTA complexes substituted by one hydrophobic chain are characterized by a water residence time similar to that of Gd-DOTA 200 ns) and that their enhanced relax-... 

The structure of the HA2 N-terminal fusion peptide has been probed by a combination of NMR and electron paramagnetic resonance (EPR) in detergent micelles that mimic the lipid bilayer, at both acid and neutral pHs (Han et al, 2001). At both acidic and neutral pH the structure is predominantly helical with a kink where it rises most prominently to the presumptive membrane surface. At lower pH the kink is stronger, there is additional 3io helix, and two charged residues are rotated out of the membrane plane. The stronger kink likely allows the peptide to become more deeply immersed, perhaps disrupting the membrane and facilitating fusion. 

NMR as well as and diffusion NMR to characterise the water interaction. Other studies include membrane protein-lipid interactions in mixed micelles studied by NMR with the use of paramagnetic reagents, DHPC and the OMPX of Escherichia colv a review on the outer membrane proteins (OMPs) of Gram negative bacteria has been published indicating the paucity of NMR structures for these and the use of molecular simulation for their study. ... 

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