Surface grafting of poly(L-glutamates). 2. Helix orientation
| Autor: | R.H Wieringa, P.J Werkman, E.A. Siesling, H.J Angerman, A.J. Schouten, E.J. Vorenkamp |
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| Přispěvatelé: | Polymers at Surfaces and Interfaces, Zernike Institute for Advanced Materials |
| Jazyk: | angličtina |
| Rok vydání: | 2001 |
| Předmět: |
chemistry.chemical_classification
POLYPEPTIDES Transition dipole moment MONOLAYERS PEPTIDES Surfaces and Interfaces Polymer Condensed Matter Physics CONFORMATION Crystallography Tilt (optics) chemistry Helix Monolayer Electrochemistry Polar General Materials Science Absorption (chemistry) POLYMERS Pendant group Spectroscopy |
| Zdroj: | Langmuir, 17(21), 6485-6490. AMER CHEMICAL SOC |
| ISSN: | 1520-5827 0743-7463 |
| Popis: | In this paper the average helix orientation of surface-grafted poly(gamma -benzyl L-glutamate) (PBLG), poly(gamma -methyl L-glutamate) (PMLG), and poly(gamma -methyl L-glutamate)-co-(gamma -n-stearyl L-glutamate) (PMLGSLG 70/30) was investigated by means of FT-IR transmission spectroscopy. The theoretical relation between the average tilt angle (theta) and the absorption peak areas of three different backbone amide bands could be calculated because their transition dipole moment directions with respect to the helix axis were known. From the normalized absorptions, the average tilt angles of grafted helices of PBLG, PMLG, and PMLGSLG 70/30 were determined. The somewhat larger average angle of PMLG helices of 35 +/- 5 degrees with respect to the substrate compared to the value of 32 +/- 5 degrees of PBLG was due to the higher grafting density of PMLG. Because of the smaller helix diameter as a result of the smaller size of the methyl side group, more PMLG helices grew on the same surface area. Sterical hindrance and unfavorable polar interactions between unidirectional aligned helices forced the PMLG helices in a more upright arrangement. The even more perpendicular orientation of PMLGSLG 70/30 (48 +/- 6 degrees) could be the result of incorporation of mainly gamma -methyl L-glutamate N-carboxyanhydride (MLG-NCA) monomers during the initiation step. Incorporation of the much larger gamma -n-stearyl L-glutamate N-carboxyanhydride (SLG-NCA) monomers afterward lead to enlarged angles with respect to the substrate. Due to swelling, a pronounced change in helix orientation of grafted PMLGSLG 70/30 in n-hexadecane was observed, resulting in an almost perpendicular helix orientation. |
| Databáze: | OpenAIRE |
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