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Authors
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Müller, M. ; Keßler, B. ; Lunkwitz, K.
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Title
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Induced Orientation of a-Helical Polypeptides in Polyelectrolyte Multilayers
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Date
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31.12.2003
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Number
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11384
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Abstract
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Polyelectrolyte multilayers (PEMs) consisting of stiff polypeptides at texturized silicon substrates were studied.These studies are focused on anisotropic PEMs in contrast with common ones consisting of flexiblepolyelectrolytes. When stiff polycation poly(<FONT SIZE="-1">L</FONT>-lysine hydrobromide) (PLL, <I>M</I><SUB>w</SUB> = 200000 g/mol) was used atpH = 11 or in the presence of NaClO<SUB>4</SUB>, a transition from random coil (R-PLL) to <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-helix (<IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-PLL) wasfound. When stiff polyanion poly(<FONT SIZE="-1">L</FONT>-glutamic acid) (PLG, <I>M</I><SUB>w</SUB> = 70000) was chosen, the <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-helical conformation(<IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-PLG) was adopted at pH = 3. The conformation was checked by IR spectroscopy and circular dichroism.The layer-by-layer technique was used in order to get homogeneous thin films of the polypeptides. TexturizedSi-ATR-substrates with parallel nanosized grooves 50-70 nm in width were used for orienting the <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-helicalpolypeptides with contour length <I>L</I> > 70 nm. Two different types of PEMs were fabricated: (i) <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-PLG/poly(diallyldimethylammoniumchloride) (PDADMAC) and (ii) <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-PLL/poly(vinyl sulfate) (PVS). Theorientation was studied by dichroic ATR-FTIR spectroscopy using polarized light. An ATR-FTIR-dichroismconcept was applied, which was established at low molecular liquid-crystalline systems. Via the dichroicratio of the amide I and II band areas measured with parallel (A<SUB>p</SUB>) and with vertically polarized IR light (A<SUB>s</SUB>)an order parameter <I>S</I> could be determined, knowing the angle <IMG SRC="/images/gifchars/theta.gif" BORDER=0 > between the <IMG SRC="/images/gifchars/alpha.gif" BORD<br />ER=0>-helical axis and the amidemode transition dipole moments. <I>S</I> is a measure for the uniaxial orientation of the multilayer embeddedpolypeptides within the nanogrooves of the silicon plate, where <I>S</I> = 0 means no and <I>S</I> = 1 means highorientation. <I>S</I> > 0.5 was found for both multilayer embedded <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-PLL and <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-PLG (i and ii), indicating asignificant orientation with respect to the nanogroove direction. The influence of <I>M</I><SUB>w</SUB>, concentration, numberof adsorption steps, and drying was investigated. PEMs exposing charged <IMG SRC="/images/gifchars/alpha.gif" BORDER=0>-helical polypeptides in theoutermost layer can be used to create biomimetic and biosensor surfaces.
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Publisher
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Journal of Physical Chemistry / B
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Wikidata
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Citation
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Journal of Physical Chemistry / B 107 (2003) 8189-8197
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DOI
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https://doi.org/10.1021/jp027812x
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