Pulsed field gradient NMR investigation of solubilization equilibria in amino acid and dipeptide terminated micellar and polymeric surfactant solutions

Hickok, Robin S.; Wedge, Seamus A.; Hansen, Alexandar L.; Morris, Kevin; Billiot, Fereshteh; Warner, Isiah M.

doi:10.1002/mrc.1099

Cited by 14 publications

(8 citation statements)

References 38 publications

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“…A major difference between the micelles of conventional surfactant monomers and polymeric surfactants is that there usually is a covalent linkage in individual polymeric surfactant molecules within the hydrophobic core that does not allow dynamic exchange of monomers between free solution and the micellar pseudo-phase. This confers rigidity and stability to the polymeric micelles [6]. The diameter of polymeric micelle ranges from 10 to 100 nm.…”

Section: Polymeric Micellesmentioning

confidence: 99%

Polymeric micelles: authoritative aspects for drug delivery

Kulthe

Choudhari

Inamdar

et al. 2012

Designed Monomers and Polymers

187

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Section: Polymeric Micellesmentioning

confidence: 99%

Polymeric micelles: authoritative aspects for drug delivery

Kulthe

Choudhari

Inamdar

et al. 2012

Designed Monomers and Polymers

187

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“…The PFG-NMR diffusion method for determining association constants becomes less accurate as the binding constants become large because the denominator in Eqn (4) contains the term (1 f b ). 23,24,33 Therefore, small changes in f b can produce large changes in the association constant when f b approaches one. If we instead compare the f b values for Leu-enkephalin-Arg and Leu-enkephalin-Lys, the respective mole fractions of 0.986 and 0.988 are nearly equal, suggesting that the affinity of these two peptides for the micelles is similar.…”

Section: Resultsmentioning

confidence: 98%

A pulsed field gradient NMR diffusion investigation of enkephalin peptide‐sodium dodecyl sulfate micelle association

Begotka

Hunsader

Oparaeche

et al. 2006

Magnetic Reson in Chemistry

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Pulsed field gradient NMR (PFG-NMR) diffusion experiments were used to investigate the binding of leucine and methionine enkephalin peptides to anionic sodium dodecyl sulfate (SDS) micelles. The study was undertaken to investigate the mechanism of interaction between enkephalin peptides and SDS micelles and to determine if NMR-derived association constants, K(eq), can predict the elution order in electrokinetic chromatography (EKC). In EKC, peptides are separated on the basis of their interactions with micelles. The Leu-enkephalin peptide-micelle association constant increased from 130 +/- 8 to 1459 +/- 57 and 1744 +/- 64 M(-1), respectively, when an Arg or Lys was added to the C-terminus. The association constant of Leu-enkephalinamide was approximately equal to that of Leu-enkephalin-Arg. Substitution of Phe4 with a Trp or Gly2 with an Ala in the Leu-enkephalin peptides also increased the micelle binding affinity. These results confirm that the interaction of Leu-enkephalin peptides with SDS micelles is largely electrostatic and that the non-polar amino acid side chains interact with the hydrophobic micelle core. The peptide-micelle association constants for the cationic Met-enkephalin peptides were also greater than their zwitterionic counterparts. For example, the Met-enkephalin K(eq) value was 162 +/- 9 M(-1), while the association constants for Met-enkephalin-Arg, Met-enkephalin-Lys, and Met-enkephalinamide were, respectively, 674 +/- 31, 426 +/- 23, and 453 +/- 27 M(-1). In both Met-enkephalin and Met-enkephalinamide, replacing Gly2 with an Ala did not significantly increase the association constant. These results confirm that with the Met-enkephalin peptides, there was little or no interaction of the amino acid side chains with the micelle core. For both the Leu-enkephalin and Met-enkephalin peptides, the association constants were consistent with EKC results, in that the peptides with smaller K(eq) values were found to elute before those with larger association constants.

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“…This comparison suggests that in both the poly(SULV) and poly(SUVL) MM structures, more of the surfactant chain area is accessible to water molecules than in a corresponding SDS micelle. It is also interesting to note that NMR diffusion studies have shown that small non-polar probe molecules solubilize in the interior of SDS and unpolymerized amino acid-based surfactant micelles to a much greater degree than into the corresponding MM [27). For example, the mole fraction of toluene molecules solubilzed into unpolymerized micelles formed by the amino acid-based surfactants sodium undecyl-(L,L)-valine and sodium undecyl-(L,L)-valine-valine were found to be 0.88 and 0.90 respectively.…”

Section: Resultsmentioning

confidence: 99%

A Molecular Dynamics Simulation Study of Two Dipeptide Based Molecular Micelles: Effect of Amino Acid Order

Morris¹,

Billiot²,

Billiot³

et al. 2013

OJPC

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Molecular dynamics (MD) simulations were used to compare the structures of the chiral molecular micelles (MM) poly-(sodium undecyl-(L,L)-leucine-valine) (poly(SULV)) and poly-(sodium undecyl-(L,L)-valine-leucine) (poly (SUVL)). Both MM contained polymerized surfactant monomers tenninated by chiral dipeptide headgroups. The study was undertaken to investigate why poly(SULV) is generally a better chiral selector compared to poly(SUVL) in electrokinetic chromatography separations. When comparing poly(SULV) to poly(SUVL), poly(SULV) had the more conformational flexible dipeptide headgroup and hydrogen bond analyses revealed that the poly(SULV) headgroup conformation allowed a larger number of intramolecular hydrogen bonds to form between monomer chains. In addition, a larger number of water molecules surrounded the chiral centers of the poly(SULV) molecular micelle. Poly(SULV) was also found to have a larger solvent accessible surface area (SASA) than poly(SUVL) and fluctuations in the poly(SULV) SASA during the MD simulation allowed dynamic monomer chain motions expected to be important in chiral recognition to be identified. Finally, approximately 50% of the Na+ counterions were found in the first three solvation shells surrounding both MM, with the remainder located in the bulk. Overall the MD simulations point to both greater headgroup flexibility and solvent and analyte access to the chiral centers of the dipeptide headgroup as factors contributing to the enhanced chiral selectivity observed with poly(SULV).

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Pulsed field gradient NMR investigation of solubilization equilibria in amino acid and dipeptide terminated micellar and polymeric surfactant solutions

Cited by 14 publications

References 38 publications

Polymeric micelles: authoritative aspects for drug delivery

Polymeric micelles: authoritative aspects for drug delivery

A pulsed field gradient NMR diffusion investigation of enkephalin peptide‐sodium dodecyl sulfate micelle association

A Molecular Dynamics Simulation Study of Two Dipeptide Based Molecular Micelles: Effect of Amino Acid Order

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