Thermodynamics of partitioning of substance P in isotropic bicelles.
The temperature dependence of the partition of a neuropeptide, substance P (SP), in isotropic (q = 0.5) bicelles was investigated by using pulsed field gradient NMR diffusion technique. The partition coefficient decreases as the temperature is increased from 295 to 325 K, indicating a favorable (negative) enthalpy change upon partitioning of the peptide. Thermodynamic analysis of the data shows that the partitioning of SP at 300 K is driven by the enthalpic term (DeltaH) with the value of - 4.03 kcal mol(-1), while it is opposed by the entropic term (-TDeltaS) by approximately 1.28 kcal mol(-1) with a small negative change in heat capacity (DeltaC(p)). The enthalpy-driven process for the partition of SP in bicelles is the same as in dodecylphosphocholine (DPC) micelles, however, the negative entropy change in bicelles of flat bilayer surface is in sharp contrast with the positive entropy change in DPC micelles of highly curved surface, indicating that the curvature of the membrane surface might play a significant role in the partitioning of peptides.
Kim
Chul
C
Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea.
Baek
Seung Bin
SB
Kim
Do Hun
DH
Lim
Sung Chul
SC
Lee
Hyeong Ju
HJ
Lee
Hee Cheon
HC
D004058:Diffusion; D008051:Lipid Bilayers / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013373:Substance P / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
D008051:Lipid Bilayers; D013373:Substance P