Yue Sun

Liaoning Normal University, Lü-ta-shih, Liaoning, China

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Publications (5)20.83 Total impact

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    ABSTRACT: Antimicrobial peptides (AMPs) with non-specific membrane disrupting activities are thought to exert their antimicrobial activity as a result of their cationicity, hydrophobicity and α-helical or β-sheet structures. Chensinin-1, a native peptide from skin secretions of Rana chensinensis, fails to manifest its desired biological properties because its low hydrophobic nature and an adopted random coil structure in a membrane-mimetic environment. In this study, chensinin-1b was designed by rearranging the amino acid sequence of its hydrophilic/polar residues on one face and its hydrophobic/nonpolar residues on the opposite face according to its helical diagram, and by replacing three Gly residues with three Trp residues. Introduction of Trp residues significantly promoted the binding of the peptide to the bacterial outer membrane and exerted bactericidal activity through cytoplasmic membrane damage. Chensinin-1b demonstrates higher antimicrobial activity and greater cell selectivity than its parent peptide, chensinin-1. The electrostatic interactions between chensinin-1b and lipopolysaccharide (LPS) may have facilitated the uptake of the peptide into Gram-negative cells and be also helpful to disrupt the bacterial cytoplasmic membrane, as evidenced by depolarisation of the membrane potential and leakage of calceins from the liposomes of Escherichia coli and Staphylococcus aureus. Chensinin-1b was also found to penetrate mouse skin and was also effective in vivo, as measured by hydroxyproline levels in a wound infection mouse model, and could therefore act as an anti-infective agent for wound healing. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Biomaterials 10/2014; 37C:299-311. · 8.31 Impact Factor
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    ABSTRACT: Dental caries and periodontitis are common bacterial mouth infections. As a potentially attractive substitute for conventional antibiotics, antimicrobial peptides have been widely tested and used for controlling bacterial infections. In this study, we tested the efficacy of the peptides from the skin secretions of Rana chensinensis for killing several major cariogenic and periodontic pathogens as well as Candida albicans. L-K6, a temporin-1CEb analog, exhibited high antimicrobial activity against the tested oral pathogens and was able to inhibit Streptococcus mutans biofilm formation and reduce 1-day-old S. mutans biofilms with a minimum biofilm inhibitory concentration and reducing concentration of 3.13 and 6.25 μM, respectively. The results of confocal laser scanning microscopy demonstrated that the peptide significantly reduced cell viability within oral biofilms. Furthermore, as little as 5 μM L-K6 significantly inhibited lipopolysaccharide (LPS)- and interleukin-1β-induced productions of interleukin-8 and tumor necrosis factor-α from THP-1 monocytic cells. This anti-inflammatory activity is associated with the binding of L-K6 to LPS and neutralizing LPS-induced proinflammatory responses in THP-1 cells, as well as dissociating LPS aggregates. Our results suggest that L-K6 may have potential clinical applications in treating dental caries by killing S. mutans within dental plaque and acting as anti-inflammatory agents in infected tissues.
    Applied Microbiology and Biotechnology 07/2014; · 3.81 Impact Factor
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    ABSTRACT: AIMS: To understand the effects of Trp residues in linear AMPs with α-helical conformations on cell permeation ability and membrane transduction efficacy. METHODS AND RESULTS: A series of L-K6 analogues were designed and synthesized by replacing Ile or Leu with Trp at different positions on the hydrophobic face of L-K6. The antimicrobial and hemolytic activity and secondary structure of the designed Trp-containing peptides were assessed. In addition, the role of Trp in membrane disruption for these designed peptides was investigated. I1W, I4W and L5W demonstrated stronger activity than the other peptides against both Gram-positive and Gram-negative bacteria. All of the tested peptides preferentially interacted with negatively charged vesicles composed of PG/CL or PG/CL/PE, and, to a lesser extent, with zwitterionic vesicles. I1W, I4W and L5W caused calcein release at 2.5 μmol l(-1) . CONCLUSIONS: The position of Trp, rather than the number of Trp residues, in these peptides was an important factor in the antimicrobial activity. Trp residues were deeply inserted into negatively charged membranes but were largely exposed in aqueous buffer solution. Significance and Impact of the Study These Trp-containing peptides may represent good candidates for new antibiotic agents and for use in new therapeutic approaches. This article is protected by copyright. All rights reserved.
    Journal of Applied Microbiology 05/2013; · 2.39 Impact Factor
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    ABSTRACT: Many antimicrobial peptides from amphibian skin have been purified and structurally characterized and may be developed as therapeutic agents. Here we describe the antibacterial properties and membrane interaction of chensinin-1, a cationic arginine/histidine-rich antimicrobial peptide, from the skin secretions of Rana chensinensis. The amino acid composition, sequence, and atypical structure of chensinin-1 differ from other known antimicrobial peptides from amphibian skin. Chensinin-1 exhibited selective antimicrobial activity against Gram-positive bacteria, was inactive against Gram-negative bacteria, and had no hemolytic activity on human erythrocytes. The CD spectra for chensinin-1 indicated that the peptide adopted an aperiodic structure in water and a conformational structure with 20 % β-strands, 8 % α-helices, and the remaining majority of random coils in the trifluoroethanol or SDS solutions. Time-kill kinetics against Gram-positive Bacillus cereus demonstrated that chensinin-1 was rapidly bactericidal at 2× MIC and PAE was found to be >5 h. Chensinin-1 caused rapid and large dye leakage from negatively charged model vesicles. Furthermore, membrane permeation assays on intact B. cereus indicated that chensinin-1 induced membrane depolarization in less than 1 min and followed to damage the integrity of the cytoplasmic membrane and resulted in efflux of molecules from cytoplasma. Hence, the primary target of chensinin-1 action was the cytoplasmic membrane of bacteria. Chensinin-1 was unable to overcome bacterial resistance imposed by the lipopolysaccharide leaflet, the major constituent of the outer membrane of Gram-negative bacteria. Lipopolysaccharide induced oligomerization of chensinin-1, thus preventing its translocation across the outer membrane.
    Applied Microbiology and Biotechnology 05/2012; 96(6). · 3.81 Impact Factor
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    ABSTRACT: Temporin-1CEb shows antimicrobial activity against Gram-positive bacteria, but its therapeutic potential is limited by its haemolysis. In this study, eight temporin-1CEb analogues with altered cationicities and hydrophobicities were synthesized. Increasing cationicity and amphipathicity by substituting neutral and non-polar amino acid residues on the hydrophilic face of the α-helix by five or six lysines increased antimicrobial potency approximately 10-fold to 40-fold, although when the number of positive charges was increased from +6 to +7, the antimicrobial potency was not additionally enhanced. The substitution of an l-lysine with a d-lysine, meanwhile maintaining the net charge and the mean hydrophobicity values, had only a minor effect on its antimicrobial activity, whereas significantly led a decrease in its haemolytic activity. Of all the peptides, l-K6 has the best potential as an antimicrobial agent because its antimicrobial activity against both Gram-positive and Gram-negative bacteria is substantial, and its haemolytic activity is negligible. l-K6 adopts an α-helix in 50% trifluoroethanol/water and 30 mm SDS solutions. l-K6 killed 99.9% of E. coli and S. aureus at 4× MIC in 60 min, and its postantibiotic effect was >5 h. l-K6 affects the integrity of E. coli and S. aureus plasma membranes by rapidly inducing membrane depolarization.
    Chemical Biology &amp Drug Design 02/2012; 79(5):653-62. · 2.51 Impact Factor