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The impact of grafted surface defects and their controlled removal on supramolecular self-assembly.

ABSTRACT: We demonstrate the use of covalently modified graphite as a convenient and powerful test-bed for the versatile investigation and control of 2-D crystallization at the liquid solid interface. Grafted aryls act as surface defects and create barriers to supramolecular self-assembly. An easily tunable grafting density allows for varying the effect of such defects on supramolecular self-assembly. Finally, the defects can be locally removed, triggering monolayer reconstructions and allowing in situ investigations of thermodynamically unstable or metastable morphologies.

SUBMITTER: Braganca AM

PROVIDER: S-EPMC5355800 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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The impact of grafted surface defects and their controlled removal on supramolecular self-assembly.

Bragança Ana M AM Greenwood John J Ivasenko Oleksandr O Phan Thanh Hai TH Müllen Klaus K De Feyter Steven S

Chemical science 20160725 12

We demonstrate the use of covalently modified graphite as a convenient and powerful test-bed for the versatile investigation and control of 2-D crystallization at the liquid solid interface. Grafted aryls act as surface defects and create barriers to supramolecular self-assembly. An easily tunable grafting density allows for varying the effect of such defects on supramolecular self-assembly. Finally, the defects can be locally removed, triggering monolayer reconstructions and allowing <i>in situ ...[more]

PMID: 28451139

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Project description:Poly-L-glutamic acid (PLGA) often serves as a model in studies on amyloid fibrils and conformational transitions in proteins, and as a precursor for synthetic biomaterials. Aggregation of PLGA chains and formation of amyloid-like fibrils was shown to continue on higher levels of superstructural self-assembly coinciding with the appearance of so-called β2-sheet conformation manifesting in dramatic redshift of infrared amide I' band below 1600 cm(-1). This spectral hallmark has been attributed to network of bifurcated hydrogen bonds coupling C = O and N-D (N-H) groups of the main chains to glutamate side chains. However, other authors reported that, under essentially identical conditions, PLGA forms the conventional in terms of infrared characteristics β1-sheet structure (exciton-split amide I' band with peaks at ca. 1616 and 1683 cm(-1)). Here we attempt to shed light on this discrepancy by studying the effect of increasing concentration of intentionally induced defects in PLGA on the tendency to form β1/β2-type aggregates using infrared spectroscopy. We have employed carbodiimide-mediated covalent modification of Glu side chains with n-butylamine (NBA), as well as electrostatics-driven inclusion of polylysine chains, as two different ways to trigger structural defects in PLGA. Our study depicts a clear correlation between concentration of defects in PLGA and increasing tendency to depart from the β2-structure toward the one less demanding in terms of chemical uniformity of side chains: β1-structure. The varying predisposition to form β1- or β2-type aggregates assessed by infrared absorption was compared with the degree of morphological order observed in electron microscopy images. Our results are discussed in the context of latent covalent defects in homopolypeptides (especially with side chains capable of hydrogen-bonding) that could obscure their actual propensities to adopt different conformations, and limit applications in the field of synthetic biomaterials.

Dataset Information

The impact of grafted surface defects and their controlled removal on supramolecular self-assembly.

Publications

The impact of grafted surface defects and their controlled removal on supramolecular self-assembly.

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