کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
611452 880676 2008 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Chirality and helix stability of polyglutamic acid enantiomers
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی شیمی کلوئیدی و سطحی
پیش نمایش صفحه اول مقاله
Chirality and helix stability of polyglutamic acid enantiomers
چکیده انگلیسی

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 C14TAB is examined. The complexed mesophases poly-l-Glu/C14TAB and poly-d-Glu/C14TAB were characterized by circular dichroism (CD) in the temperature range 10–70 °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/C14TAB and poly-d-Glu/C14TAB are hexagonally packed in a MCM-41 fashion with an intermicellar distance identical and equal to 3.55±0.10 nm3.55±0.10 nm. The CD spectra indicated that both complexes poly-l-Glu/C14TAB and poly-d-Glu/C14TAB possess a mainly α-helix structure and are exact mirror images to each other. The same mirror images and a mainly α-helix configuration were also observed by CD for the free poly-l- and poly-d-glutamic acids at room temperature. As the temperature increases from 10 up to 70 °C the α-helix of the poly-l-glutamic acid is gradually transformed to a mixture containing increased amounts of the 310-helix while the α-helix structure of the poly-d-glutamic acid is constantly degenerated. In contrast the α-helices of the corresponding complexes poly-l-Glu/C14TAB and poly-d-Glu/C14TAB are degenerated upon heating without appreciable increase of the 310-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.

Depiction of the chiral micellar aggregates developed in the systems P-l-Glu/C14TAB and P-d-Glu/C14TAB packed in hexagonal lattices of similar size 3.55±0.10 nm3.55±0.10 nm (a,ba,b-axes).Figure optionsDownload as PowerPoint slide

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Colloid and Interface Science - Volume 319, Issue 1, 1 March 2008, Pages 72–80
نویسندگان
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