Yuming Wang

China University of Petroleum, Peping, Beijing, China

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Publications (4)13.08 Total impact

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    ABSTRACT: The interplay between hydrogen bonding, hydrophobic interaction and the molecular geometry of amino acid side-chains is crucial to the development of nanostructures of short peptide amphiphiles. An important step towards developing their practical use is to understand how different amino acid side-chains tune hydrophobic interaction and hydrogen bonding and how this process leads to the control of the size and shape of the nanostructures. In this study, we have designed and synthesized three sets of short amphiphilic peptides (I(3)K, LI(2)K and L(3)K; L(3)K, L(4)K and L(5)K; I(3)K, I(4)K and I(5)K) and investigated how I and L affected their self-assembly in aqueous solution. The results have demonstrated a strong tendency of I groups to promote the growth of β-sheet hydrogen bonding and the subsequent formation of nanofibrillar shapes. All I(m)K (m = 3-5) peptides assembled into nanofibers with consistent β-sheet conformation, whereas the nanofiber diameters decreased as m increased due to geometrical constraint in peptide chain packing. In contrast, L groups had a weak tendency to promote β-sheet structuring and their hydrophobicity became dominant and resulted in globular micelles in L(3)K assembly. However, increase in the number of hydrophobic sequences to L(5)K induced β-sheet conformation due to the cooperative hydrophobic effect and the consequent formation of long nanofibers. The assembly of L(4)K was, therefore, intermediate between L(3)K and L(5)K, similar to the case of LI(2)K within the set of L(3)K, LI(2)K and I(3)K, with a steady transition from the dominance of hydrophobic interaction to hydrogen bonding. Thus, changes in hydrophobic length and swapping of L and I can alter the size and shape of the self-assembled nanostructures from these simple peptide amphiphiles.
    Chemistry 09/2011; 17(46):13095-102. · 5.93 Impact Factor
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    ABSTRACT: The effects of addition of a series of stoichiometric salts on the nanostructuring of cationic amphiphilic peptides have been investigated through the combination of atomic force microscopy (AFM), circular dichroism (CD), and turbidity measurements. The results revealed that anions had more pronounced effects than cations in tuning the nanostructures formed from these peptides. Addition of ClO(3)(-), NO(3)(-), and Br(-) could stabilize the primary nanostructures (nanostacks, nanospheres, or short nanorods) formed by A(9)K and I(3)K and effectively inhibit their growth into longer nanostructures (nanorods or nanotubes). In contrast, the anions of Cl(-), SO(4)(2-), HPO(4)(2-), PO(4)(3-), and C(6)H(5)O(7)(3-) (citrate) favored the axial growth of these peptides to form long intersecting nanofibrils and led to an increase in diameter and surface roughness, as well, clearly enhancing their propensity for nanostructuring. The efficiency of different anions in promoting the growth of peptide nanoaggregates into larger ones could be ordered as ClO(3)(-) < NO(3)(-) ≤ Br(-) < Cl(-) < SO(4)(2-) < HPO(4)(2-) < PO(4)(3-) < C(6)H(5)O(7)(3-), broadly consistent with the Hofmeister anion sequence. These observations were well rationalized by considering different aspects of direct interactions of the anions with the peptide molecules.
    The Journal of Physical Chemistry B 09/2011; 115(41):11862-71. · 3.61 Impact Factor
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    ABSTRACT: Many de novo designed amphiphilic peptides capable of self-assembly and further structural templating into hierarchical organizations such as nanofibers and gels carry more than 10 amino acid residues. A curious question is now raised about the minimal size that is required for initiating amphiphilically driven nanostructuring. In this work, we show that ultrashort peptides I3K and L3K could readily self-assemble into stable nanostructures. While L3K formed spherical nanospheres with diameters of 10−15 nm, I3K self-assembled into nanotubes with diameters of 10 nm and lengths of >5 μm. I3K nanotubes were very smooth and carried defined pitches of twisting. The difference could arise from the different β-sheet promoting power between isoleucine and leucine, suggesting that while hydrophobic interaction was dominant in the formation of L3K nanospheres hydrogen bonding governed the templating of antiparallel β-sheets and the subsequent formation of I3K nanotubes. Because of their extreme stability against heating or exposure to organic solvents, I3K nanotubes were used as templates for silicification from the hydrolysis of organosilicate precursors using TEOS (tetraethoxysilane). The lysine groups on the inner and outer nanotube surfaces worked to catalyze silicification, leading to the formation of silica nanotubes, which is evident from both AFM and TEM imaging. The formation of interesting nanotubes and nanospheres as demonstrated from very short peptide amphiphiles is significant for further exploration of their use in technological applications.
    Chemistry of Materials - CHEM MATER. 08/2010;
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    ABSTRACT: Spectroscopic ellipsometry (SE) and atomic force microscopy (AFM) have been used to investigate the adsorption of a mouse monoclonal antibody (type IgG1, anti-beta-hCG) on hydrophilic silica (bearing weak negative charges above pH 3), followed by the assessment of binding of human chorionic gonadotrophin (hCG). The antibody is a relatively large molecule with a molecular weight of 150 kDa and the isoelectric point (IP) around pH 6. The antibody adsorption was conducted at pH 4.0, 6.0 and 8.0 to examine the role of charge interaction. Ellipsometric results show that away from the IP, both initial adsorption rate and surface excess decreased, with the reduction at pH 8.0 being more pronounced than that at pH 4.0 due to the electrostatic repulsion not only between the charged antibody molecules within the adsorbed layer but also between antibody and the silica surface. Whilst parallel AFM measurements confirmed the main trend of pH dependent antibody adsorption, they also revealed the tendency of surface aggregation with increasing surface coverage. AFM height profiling at low surface coverage confirmed the "flat-on" orientation of adsorbed antibody molecules, consistent with the previous study by neutron reflection. Interestingly, the antibody height at pH 4.0 was found to be lower than that at pH 8.0, showing the influence from different electrostatic interactions under the two pH conditions. Subsequent hCG binding to the adsorbed antibodies was found to decrease with increasing surface coverage due to the steric hindrance. Under similar antibody surface coverage, the hCG binding ratio at pH 8 was higher than that at pH 4.0, a difference that could only be accounted for by the tighter surface confinement at pH 4.0.
    Journal of Colloid and Interface Science 08/2008; 323(1):18-25. · 3.55 Impact Factor