We investigated the effect of a synthetic complement peptide C3a on the outcome of Brucella abortus 544 infection in a murine macrophage cell line RAW264.7 cell. First, we determined the highest non-cytotoxic concentration of the peptide in the cell line. We also found that the peptide significantly increased the growth of the bacteria at 8 and 24 h. Although the number of bacterial CFU was also elevated at 48 and 72 h, the increases were not significant as compared to controls. We further investigated the effect of C3a peptide on the growth of Brucella by pre-incubating the peptide at various temperatures and found that the effect was reversed at 24 h post-incubation suggesting that incubation of peptide at high temperatures including 65°C or 95°C could inactivate its action. This also could indicate the beneficial effect of high temperature during infection. Although several studies reported the inhibitory effect of different antimicrobial peptides including C3a, the present study preliminarily revealed that it had no positive contribution on the control of B. abortus 544 infection in vitro and indirectly to its receptor, CD88, which belongs to GPCR. Moreover, the encouraged further exploration of the effect of other similar peptides would be performed for the purpose of finding Brucella-host cell interaction for the control of disease progression.

A positional scanning synthetic peptide combinatorial library (PS-SCL) was screened in order to identify antimicrobial peptides against the cariogenic oral bacteria, Streptococcus mutans. Activity against Streptococcus gordonii and Aggregatibacter actinomycetemcomitans was also examined. The library was comprised of six sub-libraries with the format O(1-6)XXXXX-NH2, where O represents one of 19 amino acids (excluding cysteine) and X represents equimolar mixture of these. Each sub-library was tested for antimicrobial activity against S. mutans and evaluated for antimicrobial activity against S. gordonii and A. actinomycetemcomitans. The effect of peptides was observed using transmission electron microscopy (TEM). Two semi-mixture peptides, RXXXXN-NH2 (pep-1) and WXXXXN-NH2 (pep-2), and one positioned peptide, RRRWRN-NH2 (pep-3), were identified. Pep-1 and pep-2 showed significant antimicrobial activity against Gram positive bacteria (S. mutans and S. gordonii), but not against Gram negative bacteria (A. actinomycetemcomitans). However, pep-3 showed very low antimicrobial activity against all three bacteria. Pep-3 did not form an amphiphilic α-helix, which is a required structure for most antimicrobial peptides. Pep-1 and pep-2 were able to disrupt the membrane of S. mutans. Small libraries of biochemically-constrained peptides can be used to generate antimicrobial peptides against S. mutans and other oral microbes. Peptides derived from such libraries may be candidate antimicrobial agents for the treatment of oral microorganisms.

Previously, we performed de novo RNA sequencing of Scolopendra subpinipes mutilans using high-throughput sequencing technology and identified several AMP candidates. Among them, a synthetic peptide (CP112) was designed based on the physicochemical properties of antimicrobial peptide such as length, charge, isoelectric point. Here, we have assessed the antimicrobial activities of CP112 against various microbes and the antioxidative effects. The results showed that CP112 had antimicrobial activities in radial diffusion assay and colony count assay. In addition, we found that CP112 bound to the surface of microorganisms via a specific interaction with lipoteichoic acid, lipopolysaccharide and peptidoglycan, which is one of bacteria cell wall components. Furthermore, CP112 has shown significant DPPH radical scavenging activity. Taken together, the results would be provided the basis for developing of peptide antibiotics and antioxidants.

Previously, we have performed de novo RNA sequencing of Scolpendra subpinipes mutilans using next generation sequencing technology and identified several AMP candidates. Among them, a synthetic peptide (scolopendrasin I) was designed based on SVM algorithm. In this study, we reported that the synthetic peptide scolopendrasin I had an antimicrobial and anticancer activity. As a result, scolopendrasin I showed antibacterial activities against Gram positive and Gram negative bacteria strains in radial diffusion assay and colony count assay without hemolytic activity. In addition, we confirmed that scolopendrasin I bound to the surface of bacteria via a specific interaction with lipoteichoic acid and lipopolysaccharide, which is one of bacteria cell membrane components. In addition, we found that scolopendrasin I had anticancer activities in the human leukemic T lymphocyte cell line Jurkat using MTS assay. In conclusion, our results suggested that scolopendrasin I could be useful for developing peptide antibiotics and anticancer agents.

The addition of dipeptides and 1,2-bis (aminoacyl) hydrazine derivatives a level of 250 ppm to corn oil resulted in the retardation of the oxidaitive deterioration of the oil when it was stored in the oven at 70℃ during 5 days. Their antioxidant activities were investigated by UV absorbance of the corn oil at the wavelength of 234nm. 1,2-bis (aminoacyl) hydrazine derivatives showed higher antioxidant activity than normal dipeptides. Dipeptides containing phenyl ring with which is conjugable a-carbon radical showed antioxidant activity.