Phosphatidylcholine “Wobble” in Vesicles Assessed by High-Resolution 13C Field Cycling NMR Spectroscopy

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• 作者：V. N. Sivanandam^† ; ^‡ ; ; Jingfei Cai^§ ; ; Alfred G. Redfield^† ; ; Mary F. Roberts*^§ ;
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：March 18, 2009
• 年：2009
• 卷：131
• 期：10
• 页码：3420-3421
• 全文大小：111K
• 年卷期：v.131,no.10(March 18, 2009)
• ISSN：1520-5126

文摘

High resolution ¹³C NMR field cycling (covering 11.7 down to 0.002 T) relaxation studies of the sn-2 carbonyl of phosphatidylcholines in vesicles provide a detailed look at the dynamics of this position of the phospholipid in vesicles. The spin−lattice relaxation rate, R₁, observed down to 0.05 T is the result of dipolar and CSA relaxation components characterized by a single correlation time τ_c, with a small contribution from a faster motion contributing to CSA relaxation. At lower fields, R₁ increases further with a correlation time consistent with vesicle tumbling. The τ_c is particularly interesting since it is 2−3 times slower than what is observed for ³¹P of the same phospholipid. However, cholesterol increases the τ_c for both ³¹P and ¹³C sites to the same value, 25 ns. These observations suggest faster local motion dominates the dipolar relaxation of the ³¹P, while a slower rotation or wobble dominates the relaxation of the carbonyl carbon by the α-CH₂ group. The faster motion must be damped with the sterol present. As a general methodology, high resolution ¹³C field cycling may be useful for quantifying dynamics in other complex systems as long as a ¹³C label (without attached protons) can be introduced.