@article{smirnova_smirnov_chadwick_walker_2008, title={Characterization of magnetic and electronic properties of trimetallic nitride endohedral fullerenes by SQUID magnetometry and electron paramagnetic resonance}, volume={453}, ISSN={["1873-4448"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-44549085132&partnerID=MN8TOARS}, DOI={10.1016/j.cplett.2008.01.036}, abstractNote={Magnetic and electronic properties of high-purity trimetallic nitride endohedral fullerenes Er3N@C80, Lu3N@C80, Sc3N@C80 diluted in a diamagnetic host were characterized by SQUID DC magnetometry and electron paramagnetic resonance (EPR) at multiple frequencies. The Er3N@C80 sample followed the Curie–Weiss law with negligible Weiss temperature of 0.16 K. Based on temperature dependence and isothermal saturation magnetization the effective magnetic moment of Er3N@C80 was estimated as 10.2 μB. The magnetic behavior of these fullerenes is ascribed to quenching of the orbital moment of the metal ions due to interactions between the metal centers with the nitrogen and the fullerene cage.}, number={4-6}, journal={CHEMICAL PHYSICS LETTERS}, publisher={Elsevier BV}, author={Smirnova, Tatyana I. and Smirnov, Alex I. and Chadwick, Thomas G. and Walker, Kenneth L.}, year={2008}, month={Mar}, pages={233–237} }
 @article{smirnova_chadwick_voinov_poluektov_tol_ozarowski_schaaf_ryan_bankaitis_2007, title={Local polarity and hydrogen bonding inside the Sec14p phospholipid-binding cavity: High-field multi-frequency electron paramagnetic resonance studies}, volume={92}, ISSN={["1542-0086"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-34247863841&partnerID=MN8TOARS}, DOI={10.1529/biophysj.106.097899}, abstractNote={Sec14p promotes the energy-independent transfer of either phosphatidylinositol (PtdIns) or phosphatidylcholine (PtdCho) between lipid bilayers in vitro and represents the major PtdIns/PtdCho transfer protein in the budding yeast Saccharomyces cerevisiae. Herein, we employ multi-frequency high-field electron paramagnetic resonance (EPR) to analyze the electrostatic and hydrogen-bonding microenvironments for series of doxyl-labeled PtdCho molecules bound by Sec14p in a soluble protein-PtdCho complex. A structurally similar compound, 5-doxyl stearic acid dissolved in a series of solvents, was used for experimental calibration. The experiments yielded two-component rigid limit 130- and 220-GHz EPR spectra with excellent resolution in the gx region. Those components were assigned to hydrogen-bonded and nonhydrogen-bonded nitroxide species. Partially resolved 130-GHz EPR spectra from n-doxyl-PtdCho bound to Sec14p were analyzed using this two-component model and allowed quantification of two parameters. First, the fraction of hydrogen-bonded nitroxide species for each n-doxyl-PtdCho was calculated. Second, the proticity profile along the phospholipid-binding cavity of Sec14p was characterized. The data suggest the polarity gradient inside the Sec14p cavity is a significant contributor to the driving molecular forces for extracting a phospholipid from the bilayer. Finally, the enhanced g-factor resolution of EPR at 130 and 220 GHz provides researchers with a spectroscopic tool to deconvolute two major contributions to the x-component of the nitroxide g-matrix: hydrogen-bond formation and local electrostatic effects.}, number={10}, journal={BIOPHYSICAL JOURNAL}, author={Smirnova, Tatyana I. and Chadwick, Thomas G. and Voinov, Maxim A. and Poluektov, Oleg and Tol, Johan and Ozarowski, Andrzej and Schaaf, Gabriel and Ryan, Margaret M. and Bankaitis, Vytas A.}, year={2007}, month={May}, pages={3686–3695} }
 @article{smirnova_chadwick_macarthur_poluektov_song_ryan_schaaf_bankaitis_2006, title={The chemistry of phospholipid binding by the Saccharomyces cerevisiae phosphatidylinositol transfer protein Sec14p as determined by EPR spectroscopy}, volume={281}, ISSN={["1083-351X"]}, DOI={10.1074/jbc.M603054200}, abstractNote={The major yeast phosphatidylinositol/phosphatidylcholine transfer protein Sec14p is the founding member of a large eukaryotic protein superfamily. Functional analyses indicate Sec14p integrates phospholipid metabolism with the membrane trafficking activity of yeast Golgi membranes. In this regard, the ability of Sec14p to rapidly exchange bound phospholipid with phospholipid monomers that reside in stable membrane bilayers is considered to be important for Sec14p function in cells. How Sec14p-like proteins bind phospholipids remains unclear. Herein, we describe the application of EPR spectroscopy to probe the local dynamics and the electrostatic microenvironment of phosphatidylcholine (PtdCho) bound by Sec14p in a soluble protein-PtdCho complex. We demonstrate that PtdCho movement within the Sec14p binding pocket is both anisotropic and highly restricted and that the C5 region of the sn-2 acyl chain of bound PtdCho is highly shielded from solvent, whereas the distal region of that same acyl chain is more accessible. Finally, high field EPR reports on a heterogeneous polarity profile experienced by a phospholipid bound to Sec14p. Taken together, the data suggest a headgroup-out orientation of Sec14p-bound PtdCho. The data further suggest that the Sec14p phospholipid binding pocket provides a polarity gradient that we propose is a primary thermodynamic factor that powers the ability of Sec14p to abstract a phospholipid from a membrane bilayer.}, number={46}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Smirnova, Tatyana I. and Chadwick, Thomas G. and MacArthur, Ryan and Poluektov, Oleg and Song, Likai and Ryan, Margaret M. and Schaaf, Gabriel and Bankaitis, Vytas A.}, year={2006}, month={Nov}, pages={34897–34908} }