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231224s2013 xx |||||o 00| ||eng c |
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|a 10.1021/la4008922
|2 doi
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|a pubmed24n1407.xml
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|a (DE-627)NLM226721817
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|a (NLM)23590729
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|a DE-627
|b ger
|c DE-627
|e rakwb
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| 041 |
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|a eng
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| 100 |
1 |
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|a Singh, Jasmeet
|e verfasserin
|4 aut
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|a pH-responsive aggregation states of chiral polymerizable amphiphiles from L-tyrosine and L-phenyl alanine in water
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|c 2013
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|a Text
|b txt
|2 rdacontent
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|a ƒaComputermedien
|b c
|2 rdamedia
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|a ƒa Online-Ressource
|b cr
|2 rdacarrier
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|a Date Completed 10.12.2013
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|a Date Revised 14.05.2024
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|a published: Print-Electronic
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|a Citation Status MEDLINE
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|a Sodium salts of maleamic acid derivatives of lauryl ester of tyrosine (MTNa) and phenyl alanine (MPNa) in water exhibited strong pH-responsive behaviors of viscosity and specific conductivity that originate from the concentration and pH dependence of their aggregation states. The aggregates were characterized by a novel spin-probe-partitioning electron paramagnetic resonance (SPPEPR) method and dynamic light scattering (DLS). Results of high-precision fitting of the second-harmonic EPR spectra of the small spin probe di-tert-butyl nitroxide (DTBN) in these aggregates together with viscosity, conductivity, and DLS showed that, at pH ~ 7.54, MTNa formed micelles and MPNa vesicles and MTNa exhibited a pH-induced micelle to vesicle transition as pH was lowered toward 6. MTNa, at pH ~ 7.54, formed small micelles at low concentrations that transformed to long worm-like micelles for concentrations ≥ 0.05 M, accompanied by a 30-fold increase in solution viscosity. The hydrodynamic radii from DLS confirmed the presence of small micellar aggregates of radius ~ 2 nm in MTNa at pH ~ 7.54 at the lower concentrations, with coexisting micelles (~2 nm) and vesicles (~50 nm) at pH near 6.5, vesicles (radii ~ 70 nm) at pH near 6, and large vesicles (85 nm) in MPNa at pH ~ 7.60. Both MTNa and MPNa precipitated upon reduction of pH below 6 and below 7, respectively. The rate of transfer of DTBN between the aqueous phase and the aggregate was calculated from the high-field Lorentzian linewidths of the electron paramagnetic resonance (EPR) spectra. The activation energy for the transfer determined from the temperature dependence of the rate of transfer is 12.7 kJ/mol for MTNa vesicles (pH ~ 6) and 20.6 ± 1.3 kJ/mol for MPNa (pH ~ 7.60). The pH-induced transformations were reversible
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|a Journal Article
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|a Research Support, N.I.H., Extramural
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|a Research Support, Non-U.S. Gov't
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|a Surface-Active Agents
|2 NLM
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|a Water
|2 NLM
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|a 059QF0KO0R
|2 NLM
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|a Tyrosine
|2 NLM
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|a 42HK56048U
|2 NLM
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| 650 |
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|a Phenylalanine
|2 NLM
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| 650 |
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|a 47E5O17Y3R
|2 NLM
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| 700 |
1 |
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|a Ranganathan, Radha
|e verfasserin
|4 aut
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1 |
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|a Angayarkanny, S
|e verfasserin
|4 aut
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|a Baskar, Geetha
|e verfasserin
|4 aut
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|a Mandal, A B
|e verfasserin
|4 aut
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| 773 |
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|i Enthalten in
|t Langmuir : the ACS journal of surfaces and colloids
|d 1992
|g 29(2013), 19 vom: 14. Mai, Seite 5734-41
|w (DE-627)NLM098181009
|x 1520-5827
|7 nnns
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| 773 |
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|g volume:29
|g year:2013
|g number:19
|g day:14
|g month:05
|g pages:5734-41
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|u http://dx.doi.org/10.1021/la4008922
|3 Volltext
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