Chirality and helix stability of polyglutamic acid enantiomers

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Chirality and helix stability of polyglutamic acid enantiomers (EN)

Kodona, E. K. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Kodona, E. K. (EN)

In this work the chirality and the relative thermal stability of ordered micellar aggregates of poly-L- and poly-D-glutamic acids with the cationic surfactant C(14)TAB is examined. The complexed mesophases poly-L-Glu/C(14)TAB and poly-D-Glu/C-14 TAB were characterized by circular dichroism (CD) in the temperature range 10-70 degrees C for their chirality and thermal stability as well as by X-ray diffraction (XRD) for the micellar ordered structure. Low angle XRD analysis showed that both micellar aggregates poly-L-Glu/C(14)TAB and poly-D-Glu/C(14)TAB are hexagonally packed in a MCM-41 fashion with an intermicellar distance identical and equal to 3.55 +/- 0.10 nm. The CID spectra indicated that both complexes poly-L-Glu/C(14)TAB and poly-D-Glu/C(14)TAB possess a mainly alpha-helix structure and are exact mirror images to each other. The same mirror images and a mainly a-helix configuration were also observed by CID for the free poly-L- and poly-D-glutamic acids at room temperature. As the temperature increases from 10 up to 70 degrees C the ce-helix of the poly-L-glutamic acid is gradually transformed to a mixture containing increased amounts of the 3(10)-helix while the alpha-helix structure of the poly-D-glutamic acid is constantly degenerated. In contrast the alpha-helices of the corresponding complexes poly-L-Glu/C(14)TAB and poly-D-Glu/C(14)TAB are degenerated upon heating without appreciable increase of the 3(10)-helices as an intermediate configuration. This difference in helix conservation is attributed to increase protection of the L-enantiomers, compared to D-enantiomers, which might be related to the survival of L-aminoacids in the living world. (c) 2007 Elsevier Inc. All rights reserved. (EN)

ordered micellar aggregates (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

J Colloid Interface Sci (EN)


<Go to ISI>://000252750400011

Elsevier (EN)

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