Enzymatic Grooming of Organic Thin Films

Abstract

These conditions for oxidative coupling of terminal acetylenes were adopted from: D O'Krongly, S. R. Denmeade, M. Y. Chiang, R. Breslow, J Am. Chrm. S O L . 1985. 107. 5544. The molecular mass of compound 4. but not of 12, was determined by matrixassisted laser desorption time-of-flight mass spectrometry (MALD-TOF-MS) (9-nitroanthracene matrix). We are grateful to Armen Boldi and Prof. Dr. Franqois Diederich, ETH, Zurich. Structure determination of 4: Dlffractometer Nicolet R 3m/V, i(MoKI), graphite monochromator. Wyckoff scan, 3 I 2 0 2 50-, direct methods (SHELXTL-PLUS). Crystal dimensions 0.65 x 0.52 x 0.45 mm3, space group P2,:n, Z = 2. T = 200 K : cell dimensions: a = 6 053(2), h = 21.121(8), c =15 l61(4) A. 1 = 7 = 90', fl = 92.34(2)'. pEalCd = 1 . 3 6 g~m -~. 3397 Independent reflections, of which 2566 were considered observed (F" 2 4a(F)). 229 parameters for the structure refinement, all non-hydrogen atoms anisotropic, R = 0.047. R, = 0.047. Further details of the crystal structure investigation may he obtained from the Fachinformationsrentrum Karlsruhe, D-76344 Eggenstein-Leopoldshafen, on quoting the depository number CSD-400451, the names of the authors. and the journal citation.We recently described the preparation of new materials consisting of helical peptides arranged nearly vertically and unidirectionally from the surface of gold and of indium-tin oxide (ITO) glass."] These layers were produced by polymerization of the N-carbonic anhydride of amino acids, and although they are composed of essentially completely helical structures. the polypeptide chains appeared not to be monodisperse. We report here that these synthetic, oriented peptide layers can be manipulated enzymatically to clip selectively the longer peptide chains, providing a more uniform layer without concurrently destroying bulk material or adversely influencing the high levels of helicity of the layers. These results are significant from two perspectives. First, we have demonstrated that enzymes can be used to manipulate the macroscopic features of bulk materials, in this case resulting in the smoothing of an uneven polymer surface. Second, we have shown that bulk materials comprised of natural substrates for enzymes are resistant to natural enzymatic degradation when formed in a tightly organized array.Through the use of suitable starting "seeds" of different size, we have been able to define an area on the surface that is appropriate for the helical secondary structure of polyphenylalanine, polyethylglycine, and polyleucine on gold (as a thin layer on chromium-coated silicon) and of polyalanine on both I T 0 glass and gold (Fig. I).". Possible applications of these polypeptide Fig. 1. Schematic representation of a layer of helical polyalanine formed by polymerizarion of the N-carbonic anhydride starting with a monolayer of aminotrithiol 1 as a "seed" bound to a gold layer on silicon with an intervening layei ofchromium. For clarity, 1 is shown as a cylinder on the surface layers include waveguide optical switches based on nonlinear ...

α-Helical Polypeptide Films Grown From Sulfide or Thiol Linkers on Gold Surfaces

“…Film thicknesses were determined by grazing angle reflectance (GAF) FT-IR spectroscopy, where it has been previously shown that each 0.1 absorbance represents ca. 300 ä [2]. We were able to grow layers approximately 1000 ä thick from both linkers 2 and 3.…”

“…The resulting layers are oriented nearly vertically to the metal surface and are relatively thick, exceeding 1000 ä. Furthermore, we have shown that the layers can be smoothed to a fairly uniform length by enzymatically grooming longer peptide chains with retention complete surface coverage and a-helicity of the layers [2]. These highly oriented supramolecular materials may serve as optical switches based on presumed nonlinear optical properties resulting from unidirectional alignment of polarization [3] [4].…”

“…FT-IR (KBr): 2972m, 2954m, 2923m, 1727s, 1441m, 1419m, 1363m, 1284m, 1265s, 1210s, 1193m, 1096m, 1048s, 1009m, 929m, 853m. 1 (2). According to a modified procedure of Brown and Narasimhan [13].…”

Electric-field-enhanced oriented cobalt coordinated peptide monolayer and its electrochemical properties

“…The fabrication techniques of the a-helical assemblies on the substrates have been well studied, such as the Langmuir-Blodgett (L-B) method [10][11][12], self-assembly [13][14][15][16][17][18] and the ring opening polymerization of N-carboxyanhydride of amino acids (NCA) on the initiator immobilized substrate surfaces [19][20][21][22]. These techniques offered a powerful platform for the formation of the a-helical peptide assemblies on substrate.…”

Photo-induced vectorial electron transfer through oriented metal-coordinated peptide assembly on a self-assembled monolayer

“…Studies on vertically and unidirectionally oriented peptide assembly systems may be important not only to the understanding of a simple and/or essential mechanism for the signal transduction through biological membrane but also may provide the basis for a molecular device capable of transferring information. The fabrication of vertically oriented α-helical peptide assemblies such as Langmuir-Blodgett (LB) films [5][6][7] and selfassembled monolayers (SAMs) [8][9][10][11][12] and grafted polypeptide layers prepared by the ring opening polymerization of Ncarboxyanhydride of amino acids (NCA) on the initiator immobilized substrate surfaces [13][14][15][16] has been reported. However, the LB films are practically insufficient because of the lack of physical stability due to the fact that the individual peptide chain remains unfixed.…”