• Proceedings of the Korean Biophysical Society Conference
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• 1997.07a
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• pp.13-13
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• 1997

Gaegurin 4 is an antimicrobial peptide found in the skin of a Korean frog, Rana rugosa, known for its "wound-healing" effect for years. This 37-residue basic peptide binds to cell membranes and forms ion channels like other antimicrobial peptides but does not exhibit hemolytic activity.(omitted)

• BMB Reports
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• v.37 no.4
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• pp.460-465
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• 2004

A 16-residue polypeptide model with the sequence acetyl-YALSLAATLLKEAASL-OH was derived by rational de novo peptide design. The designed sequence consists of amino acid residues with high propensity to adopt an alpha helical conformation, and sequential order was arranged to produce an amphipathic surface. The designed sequence was chemically synthesized using a solid-phase method and the polypeptide was purified by reverse-phase liquid chromatography. Molecular mass analysis by electro-spray ionization mass spectroscopy confirmed the correct designed sequence. Structural characterization by circular dichroism spectroscopy demonstrated that the peptide adopts the expected alpha helical conformation in 50% acetonitrile solution. Liposome binding assay using Small Unilamellar Vesicle (SUV) showed a marked release of entrapped glucose by interaction between the lipid membrane and the tested peptide. The channel-forming activity of the peptide was revealed by a planar lipid bilayer experiment. An analysis of the conducting current at various applied potentials suggested that the peptide forms a cationic ion channel with an intrinsic conductance of 188 pS. These results demonstrate that a simple rational de novo design can be successfully employed to create short peptides with desired structures and functions.

• Mass Spectrometry Letters
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• v.12 no.4
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• pp.131-136
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• 2021

Collision-induced dissociation of peptides involves a series of proton-transfer reactions in the activated peptide. To describe the kinetics of energy-variable dissociation, we considered the heat capacity of the peptide and the Marcus-theory-type proton-transfer rate. The peptide ion was activated to the high internal energy states by collision with a target gas in the collision cell. The mobile proton in the activated peptide then migrated from the most stable site to the amide oxygen and subsequently to the amide nitrogen (N-protonated) of the peptide bond to be broken. The N-protonated intermediate proceeded to the product-like complex that dissociated to products. Previous studies have suggested that the proton-transfer equilibria in the activated peptide affect the dissociation kinetics. To take the extent of collisional activation into account, we assumed a soft-sphere collision model, where the relative collision energy was fully available to the internal excitation of a collision complex. In addition, we employed a Marcus-theory-type rate equation to account for the proton-transfer equilibria. Herein, we present results from the integrated thermochemical approach using a tryptic peptide of ubiquitin.

• Preventive Nutrition and Food Science
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• v.8 no.2
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• pp.154-157
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• 2003

A peptide inhibiting HIV-1 pretense was isolated from the hydrolysate of manila clam (Ruditapes philippinarum) proteins digested with thermolysin. The peptide was purified by using membrane filtration, gel permeation chromatography, ion exchange chromatography, and reverse phase HPLC, The amino acid sequence of the peptide was determined to be Ile-Tyr-Glu-Gly. This tetrapeptide sequence exists in some proteins of Physarum polycephalum and Mycobacterium smegmatis. Chemically synthesized Ile-Tyr-Glu-Gly showed the $IC_{50}$/ value of 22.3 $\mu$M.

• Microbiology and Biotechnology Letters
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• v.22 no.1
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• pp.52-58
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• 1994

The induced antibiotic peptides were isolatde from the white-spotted folwer chafer, Protaetia brevitarsis by injection of E. coli suspension to the larvae of the insect. The antibacterial activity of the peptides were assayed by the plate growth ingibition method, and were purified by ion-exchange chromatography, reversed-phase HPLC, ion-exchange HPLC and SDS-PAGE etc. The peptides were estimated as 9 kDa in molecular weight and named Protaecin I and Protaecin II, respectively. Protaecin I and II have strong antibacterial activities against Gram-positivie and/or Gram-negative bacteria, and they are stable in the heat treatment and in the range of pH 2-12.

• Bulletin of the Korean Chemical Society
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• v.22 no.6
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• pp.570-574
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• 2001

Magnesium isotope separation was investigated by chemical ion exchange with the 1-aza-12-crown-4 bonded Merrifield peptide resin using an elution chromatographic technique. The capacity of the novel azacrown ion exchanger was 1.0 meq/g dry resin. The heavier isotopes of magnesium were enriched in the resin phase, while the lighter isotopes were enriched in the solution phase. The single stage separation factor was determined according to the method of Glueckauf from the elution curve and isotopic assys. The separation factors of $^{24}Mg^{2+}$-$^{25}Mg^{2+}$, $^{24}Mg^{2+}$-$^{26}Mg^{2+}$, and $^{25}Mg^{2+}$-$^{26}Mg^{2+}$ were 1.008, 1.019, and 1.006, respectively.

• Applied Biological Chemistry
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• v.49 no.3
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• pp.196-201
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• 2006

Vitellogenin, which is found in the serum of female and male fishes exposed to environmental endocrine disrupter or estrogen hormone, is used as a biomarker for environmental contamination with an endocrine disrupter. In order to produce antibody against vitellogenin, a synthetic peptide for partial vitellogenin was injected into rabbits. In addition, by using ion exchange chromatography on DE-52, vitellogenin was purified from the serum of carp induced with $17{\beta}$-estradiol. Polyclonal antibody against purified vitellogenin reacted well with vitellogenin in the serum of carp induced with $17{\beta}$-estradiol and the serum of female carp, whereas polyclonal antibody against the vitellogenin peptide did not react with proteins in those samples. This may indicate that vitellogenin proteins, covalently modified largely, could not be detected by Western blotting with the polyclonal antibody against the synthetic vitellogenin peptide.

• BMB Reports
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• v.49 no.2
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• pp.128-133
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• 2016

Astrocytes play a critical role in normal brain functions and maintaining the brain microenvironment, and defects in astrocytogenesis during neurodevelopment could give rise to severe mental illness and psychiatric disorders. During neuro-embryogenesis, astrocytogenesis involves astrocytic differentiation of neural precursor cells (NPCs) induced by signals from ciliary neurotrophic factor (CNTF) or pituitary adenylate cyclase-activating peptide (PACAP). However, in contrast to the CNTF signaling pathway, the exact mechanism underlying astrocytic differentiation induced by PACAP is unknown. In the present study, we aimed to verify a signaling pathway specific to PACAP-induced astrocytogenesis, using exchange protein directly activated by cAMP2 (Epac2)-knockout mice. We found that PACAP could trigger astrocytic differentiation of NPCs via Epac2 activation and an increase in the intracellular calcium concentration via a calcium ion influx. Taken together, we concluded that astrocytogenesis stimulated by PACAP occurs through a novel signaling pathway independent from CNTF-JAK/STAT signaling, that is the well-known pathway of astrocytogenesis.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.4
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• pp.358-366
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• 2012

A novel neuropeptide was isolated from the skin of the conger eel Conger myriaster using hagfish Eptatretus burgeri intestine as a bioassay system. The sequence of the purified peptide was analyzed using automated amino acid sequencing and MALDI-TOF mass spectrophotometry. The molecular ion peak in the MALDI-TOF mass spectrum of the peptide was at m/z 962.89 $(M+H)^+$. The sequence of the peptide was determined to be L-P-M-L-E-T-Q-M, and was tentatively named comyrin. To investigate the complete primary structure of comyrin, comyrin-OH and comyrin-$NH_2$ were synthesized and the chemical and pharmacological properties of the synthetic peptides were compared with those of the native peptide. However, the elution time of synthetic peptides did not match that of the native peptide on the reverse-phase HPLC chromatogram. In addition, the synthetic peptides did not cause contractile activity in the intestinal smooth muscle of the hagfish. Based on these results, one possible reason for this disagreement may be the presence of a D-amino acid in comyrin.

• YAKHAK HOEJI
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• v.55 no.3
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• pp.227-233
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• 2011

We previously reported the protein isolated from Coptidis Rhizoma (CRP), which has antifungal activity against a fungal pathogen, Candida albicans. In the current study, we investigated what portion in the CRP is responsible for the antifungal activity. For the investigation, the CRP was fractionated on a Shepadex G-50 column. Data resulting from the fractionation, seven fractions were obtained. Fractions (Fr.) I, II, and III eluted initially from the column showed no inhibitory effect on the growth of C. albicans, whereas Fr. IV, V, and VI eluted later revealed inhibition of the growth, and Fr. IV and VI showed potent antifungal activity by broth susceptibility analysis. However, Fr. VI was contained in the CRP more than Fr. IV, which led us to select the VI for the following experiments. In a murine model of a subcutaneous candidiasis caused by C. albicans, the Fr. VI displayed a therapeutic effect on nude mice pretreated with anti-neutrophil monoclonal antibody (RB68C5) and then infected subcutaneously with live C. albicans. At day 16, these mice were healed almost up to 78% of the infected area when compared to infected area of control nude mice that received diluent (Dulbecco's Phosphate-Buffered Saline; DPBS), instead of the Fr. VI (P<0.01). The Fr. VI blocked hyphal formation from blastoconidial form of C. albicans (P<0.01), which might prevent penetration of hyphae to the deeper site of skin and thus helps the healing. In the ionic strength test, the effect of Fr. was influenced by $Ca^{2+}$ ion just like other known antimicrobial peptides, but the influence was affected at an extremely high concentration such as 500 mM. Thus, such ion-concentration is considered to be meaningless in the clinical situation. Considering all data together, Coptidis Rhizoma is appeared to produce an antimicrobial peptide that has therapeutic effect on subcutaneous infection caused by C. albicans.