Trends in Biotechnology, Volume 25, Issue 2, 1 February 2007, Pages 48-55
Richard E. Palmer and Carl Leung
In this Opinion article, we describe a nanotechnology-based approach to immobilize and orient proteins onto surfaces using atomic clusters prepared by physical methods. This is relevant to future protein biochips where dilute arrays of protein binding sites, each designed to immobilize no more than one protein molecule, would be ideal. In the case of a surface consisting of size-selected atomic gold clusters, proteins containing free cysteine residues can chemisorb directly to the bare cluster surface, thus effecting oriented immobilisation. The selection of atomic gold clusters in the size range 1–100 atoms (<3nm in diameter) is intended to ensure that, typically, only one protein can bind directly to the cluster surface. These nanoclusters of a smaller size scale than that of the protein present minimal contact between the gold and the protein, and hence imply a reduced risk of protein denaturing compared with gold films or extended surfaces.
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Trends in Biotechnology, Volume 29, Issue 10, 1 October 2011, Pages 490-498
Narendra Reddy and Yiqi Yang
Various natural and synthetic polymers are being explored to develop biomaterials for tissue engineering and drug delivery. Although proteins are preferable over carbohydrates and synthetic polymers, biomaterials developed from proteins lack the mechanical properties and/or biocompatibilities required for medical applications. Plant proteins are widely available, have low potential to be immunogenic and can be made into fibers, films, hydrogels and micro- and nano-particles for medical applications. Studies, mostly with zein, have demonstrated the potential of using plant proteins for tissue engineering and drug delivery. Although other plant proteins such as wheat gluten and soyproteins have also shown biocompatibility using in vitro studies, fabricating biomaterials such as nano-fibers and nano-particles from soy and wheat proteins offers considerable challenges.
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Biophysical Journal, Volume 100, Issue 4, 16 February 2011, Pages 1083-1093
Mahmoud Moradi, Volodymyr Babin, Celeste Sagui and Christopher Roland
There has been considerable debate about the intrinsic PPII propensity of amino-acid residues in denatured polypeptides. Experimentally, the propensity scale is based on the behavior of guest amino-acid residues placed in the middle of polyproline hosts. We have used classical molecular dynamics simulations, with state-of-the-art force fields to carry out a comprehensive analysis of the conformational equilibria of the proline-based host oligopeptides with single guests. The tracked structural characteristics include the PPII content, the cis/trans isomerization of the prolyl bonds, the puckering of the pyrrolidine rings of the proline residues, and the secondary structural motifs. We find no evidence for an intrinsic PPII propensity in any of the guest amino acids other than proline. Instead, the PPII content as derived from experiments may be explained in terms of: 1), a local correlation between the dihedral angles of the guest amino acid and the proline residue immediately preceding it; and 2), a nonlocal correlation between the cis/trans states of the peptide bonds. In terms of the latter, we find that the presence of a guest (other than proline, tyrosine, or tryptophan) increases the trans content of most of the prolyl bonds, which results in an effective increase of the peptide PPII content. With respect to the local dihedral correlations, we find that these are well described in terms of the so-called odds-ratio statistic. Expressed in terms of free energy language, the PPII content based on the odds-ratio of the relevant residues correlate well with the experimentally measured PPII content.
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Copyright © 2002 The Biophysical Society All rights reserved.
Biophysical Journal, Volume 83, Issue 2, 1194-1204, 1 August 2002
* Departament de Química Orgànica, Parc Científic de Barcelona, Universitat de Barcelona, 08028-Barcelona
† Departament de Química Física, Parc Científic de Barcelona, Universitat de Barcelona, 08028-Barcelona
‡ Serveis Científicotècnics, Parc Científic de Barcelona, Universitat de Barcelona, 08028-Barcelona
§ Departament de Tensioactius, IIQAB, CID, CSIC, 08034-Barcelona, Spain
Zeins are maize storages proteins that accumulate inside large vesicles called protein bodies. γ-Zein lines the inner face of the protein body membrane, and its N-terminal proline-rich repetitive domain with the sequence (VHLPPP)8 appears to be necessary for the accumulation of the protein within the organelle. Synthetic (VHLPPP)8 adopts an amphipathic polyproline II conformation. In a preliminary recent work we used atomic force microscopy to study the surface organization of the octamer and transmission electron microscopy to visualize aggregates of the peptide from aqueous solution. We previously envisioned two self-assembly models (i.e., the geometric and the micellar) that take into account the observed features. In the present work we studied in detail the self-assembly of the peptide in solution and found that the peptide is able to form cylindrical micelles. Fibrils formed on graphite are generated by assembly of solution micelles. Based on the results of these studies, we focused exclusively on the micellar model. To our knowledge we have characterized for the first time supramolecular aggregates of polyproline structures other than collagen. The spontaneous arrangement of (VHLPPP)8 suggests a role for the N-terminal domain of γ-zein in the process of the whole protein deposition in protein bodies.