FMOC-Amino Acid Surfactants: Discovery, Characterization and Chiroptical Spectroscopy

Vijay, R.; Polavarapu, Prasad L.

doi:10.1021/jp308134m

Cited by 22 publications

(34 citation statements)

References 46 publications

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“…The Fmoc-amino acids were dispersed in deionised water and sodium hydroxide used to adjust the pH. 40,41 However, we find that even the most hydrophobic amino acids are easily deprotected if care is not taken at the concentrations used here. We have found that the most effective method is to use an excess of the Fmoc-amino acid, which we then remove by filtration.…”

Section: Resultsmentioning

confidence: 94%

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Hydrogels formed from Fmoc amino acids

et al. 2015

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A number of Fmoc amino acids can be effective low molecular weight hydrogelators. The type of gel formed depends on the amino acid used and, in the case of FmocF, the final pH of the system. The single crystal structure of two of the gelators (FmocF and FmocY) have been determined and the data compared to the fibre X-ray diffraction data. FmocF, which forms metastable gels, crystallises easily and the data for the fibre phase and crystal phase are relatively similar. For FmocF, the fibre axis in b is consistent with the hydrogen bonding repeat distances and the diffraction pattern calculated from the single crystal structure is a good match with the experimental fibre X-ray diffraction data. On the other hand, there are significant differences between the crystalline phase determined and the fibre phase for FmocY. The packing of FmocY within the crystal structure is created by interactions between the planar Fmoc groups, whilst it is clear that hydrogen bonding drives the self-assembly into fibrillar structures within the gels. This shows that understanding the packing in gel phase by analogy to isolated crystal structures has the potential to lead to erroneous conclusions. CrystEngCommThis journal is

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Section: Resultsmentioning

confidence: 94%

“…Of course, the Fmoc group is used as a base-sensitive protecting group 39 and great care needs to be taken here to avoid removing the Fmoc group from the amino acid. 40,41 To test for gelation, we then lowered the pH. 8 The solution is used immediately after formation to minimise deprotection.…”

Section: Resultsmentioning

confidence: 99%

Hydrogels formed from Fmoc amino acids

et al. 2015

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“…Significant advantages associated with using SOR for studying the chiral amphiphiles include the following: (1) Chiral guest molecules can be used as probes for studying the aggregation of achiral surfactants . (2) Some chiral amphiphiles showed a dramatic increase in SOR, beyond their CMCs, but no such changes could be observed in ECD and VCD spectra . (3) A relationship between the size of spherical chiral surfactant aggregates and their SOR values has been discerned .…”

Section: Introductionmentioning

confidence: 99%

Specific optical rotation is a versatile tool for the identification of critical micelle concentration and micellar growth of tartaric acid–based diastereomeric amphiphiles

Raghavan

Polavarapu

2017

Chirality

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Four novel tartaric acid-based diastereomeric chiral amphiphiles, two being enantiomers of the other two, have been synthesized and investigated using chiroptical spectroscopic methods, along with tensiometry and dynamic light scattering experiments. We found that an inflection point in specific optical rotation (SOR) values at ~0.32 mM corresponds to the critical micelle concentration (CMC). The increase in magnitude of SOR values beyond CMC corresponds to the growth of aggregates. For enantiomers, oppositely signed SOR values were observed, ruling out the possibility for the presence of aggregation size mediated artefacts. SOR values did not exhibit concentration dependence for a chiral tartaric acid based non-aggregating analogue further establishing the absence of artefacts or anomalous interaction of tartaric acid based head group with solvent. Electronic circular dichroism spectra showed no significant changes in band positions or intensities with concentration. Due to the requirement for higher concentrations (~200 mM) needed to obtain vibrational circular dichroism spectra, these measurements are not found to be useful for studying concentration dependent properties of chiral amphiphiles.

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“…5 This is the case for chiral surfactants where some experimentally observed chiroptical properties are yet to be fully understood. [6][7][8] Surfactants are a class of compounds that are "surface active", in that they tend to gather at aqueous surfaces, or interfaces between immiscible liquid layers, and influence the amount of work needed to expand the surface. 9 Surfactant molecules, also called amphiphiles, generally possess two chemically distinct groups: a hydrophilic group that favorably interacts with the water solvent and a hydrophobic group that repels the water solvent.…”

Section: Introductionmentioning

confidence: 99%

Concentration Dependent Specific Rotations of Chiral Surfactants: Experimental and Computational Studies

Covington

Polavarapu

2016

J. Phys. Chem. A

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Recent experimental studies have shown unexpected chiroptical response from some chiral surfactant molecules, where the specific rotations changed significantly as a function of concentration. To establish a theoretical understanding of this experimentally observed phenomena, a novel methodology for studying chiral surfactants via combined molecular dynamics (MD) and quantum mechanical (QM) calculations is presented. MD simulations on the +10 000 atom surfactant systems have been performed using MD and QM/molecular mechanics (MM) approaches. QM calculations performed on MD snapshots coupled with extensive analysis on lauryl ester of phenylalanine (LEP) surfactant system indicate that the experimentally observed variation of specific rotation with concentration may be due to the conformational differences of the surfactant monomers in the aggregates. Though traditional MM simulations did not show significant differences in the conformer populations, QM/MM simulations using the forces derived from the PM6 method did predict conformational differences between aggregated and nonaggregated LEP molecules, which is consistent with experimental data. Additionally the electrostatic environment of charged surfactants may also be important, since dramatic changes in the Boltzmann populations of surfactant monomers can be noted in the presence of an electric field generated by the chiral ionic aggregates.

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FMOC-Amino Acid Surfactants: Discovery, Characterization and Chiroptical Spectroscopy

Cited by 22 publications

References 46 publications

Hydrogels formed from Fmoc amino acids

Hydrogels formed from Fmoc amino acids

Specific optical rotation is a versatile tool for the identification of critical micelle concentration and micellar growth of tartaric acid–based diastereomeric amphiphiles

Concentration Dependent Specific Rotations of Chiral Surfactants: Experimental and Computational Studies

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