Effect of α-Tocopherol on the Microscopic Dynamics of Dimyristoylphosphatidylcholine Membrane

Published

January 14, 2016

Author(s)

V.K. Sharma, E. Mamontov, Madhu Sudan Tyagi, V.S. Urban

Abstract

Vitamin E behaves as an antioxidant and is well known for its protective properties of the lipid membrane. The most biologically active form of vitamin E in the human organism is α-Tocopherol (aToc). Very recently (D. Marquardt et al.., J. Am. chem. Soc. 2014, 136 , 2-3-210), it has been shown that aToc resides near the center of dimyristoylphosphatidylcholine (DMPC)bilayer, which is in stark contrast to other PC membranes, where aToc is located near the lipid-water interface. Here we report an unusual effect of this exceptional location of aToc on the dynamical behavior of DMPC membrane probed by incoherent elastic and quasielastic neutron scattering. For pure DMPC vesicles, elastic scan data shows two step-like drops in the elastic intensity at 288 and 297 K, which correspond to the pre- and main phase transitions, respectively. However, inclusion of aToc into DMPC membrane inhibits the step-like elastic intensity drops, indicating a significant impact of aToc on the phase behavior of the membrane. This observation is supported by our differential scanning calorimetry data, which shows that inclusion of aToc leads to a significant broadening of the main phase transition peak, whereas the peak corresponding to the pre-transition disappears. We have performed quasielastic neutron scattering (QENS) measurements on DMPC vesicles with various concentrations of aToc at 280, 293 and 310 K. We have found that aToc affects bot the lateral diffusion and the internal motions of the lipid molecules. Below the main phase transition temperature inclusion of aToc accelerates both the lateral and the lateral and the internal lipid motions. On the other hand, above the main phase transition temperature addition of aToc restricts only the internal motion, without a significant influence on the lateral motion. Our results support the finding the location of aToc in DMPC membrane is deep within the bilayer.

Citation

Journal of Physical Chemistry B

Volume

120

Issue

1

Pub Type

Journals

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Keywords

dynamics, neutron scattering

Citation

Sharma, V. , Mamontov, E. , Tyagi, M. and Urban, V. (2016), Effect of α-Tocopherol on the Microscopic Dynamics of Dimyristoylphosphatidylcholine Membrane, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919843 (Accessed July 17, 2024)