The temperature dependence and thermodynamic functions of partitioning of substance P peptides in dodecylphosphocholine micelles
✍ Scribed by Tuck C. Wong; Xinfeng Gao
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1998
- Tongue
- English
- Weight
- 96 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The temperature dependence of the partition of a neuropeptide, Substance P (SP), and its [Tyr 8 ] analogue in a widely used membrane mimic, dodecylphosphocholine micelles, was studied by using a pulsed field gradient nmr diffusion technique. The partition coefficient was found to decrease when the temperature is increased, indicating a favorable (negative) enthalpy change upon partitioning of the peptides. Thermodynamic functions of the partitioning were determined. The enthalpy of partition DH part , was found to be in the 02.5 to 03.0 kcal/ mol range, which is between 2 and 3 times higher than the entropic term 0TDS part . The free energy of partitioning is consistent with a model in which the SP peptides interact with the micelles mainly through the hydrophobic side chains of the residues Phe 7 , Phe 8 (or Tyr 8 ), Leu 10 , and Met 11 , and without the insertion of a major portion of the peptide into the hydrophobic core of the micelles.