• Proceedings of the Korean Biophysical Society Conference
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• 2001.06a
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• pp.35-35
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• 2001

The conformational study on cyclic Ac-Cys-Pro-Xaa-Cys-NHMe (Ac-CPXC-NHMe; X = Ala, Val, Leu, Aib, Gly, His, Phe, Tyr, Asn, and Ser) peptides has been carried out using the ECEPP/3 force field and the hydration shell model in the unhydrated and hydrated states. This work has been undertaken to investigate structural implications of the CPXC sequence as the chain reversal for the initiation of protein folding and as the motif for active site of disulfide oxidoreductases.(omitted)

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.874-880
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• 2010

A series of 13- and 14-membered cyclic enkephalin analogs based on the moderately $\mu$ selective prototype compound Tyr-C[D-$A_2bu$-Gly-Phe-Leu] 8a were synthesized to investigate the structure-activity relationship. The modifications of sequence were mainly focused on two positions 3 and 5, critical for the selective recognition for $\mu$ and $\delta$ opioid receptors. The substitution of hydrophobic $Leu^5$ with hydrophilic $Asp^5$ derivatives led to Tyr-C[D-$A_2bu$-Gly-Phe-Asp(N-Me)] 7 and Tyr-C[D-Glu-Phe-gPhe-rAsp(O-Me)] 5, the peptides with a large affinity losses at both $\mu$ and $\delta$ receptors. The substitution of $Phe^3$ with $Gly^3$ led to Tyr-C[D-Glu-Gly-gPhe-rLeu] 3 and Tyr-C[D-Glu-Gly-gPhe-D-rLeu] 4, the peptides with large affinity losses at $\mu$ receptors, indicating the critical role of phenyl ring of $Phe^3$ for $\mu$ receptor affinities. One atom reduction of the ring size from 14-membered analogs Tyr-C[D-Glu-Phe-gPhe-(L and D)-rLeu] 6a, 6b to 13-membered analogs Tyr-C[D-Asp-Phe-gPhe-(L and D)-rLeu] 1, 2 reduced the affinity at both $\mu$ and $\delta$ receptors, but increased the potency in the nociceptive assay, indicating the ring constrain is attributed to high nociceptive potency of the analogs. For the influence of D- or L-chirality of $Leu^5$ on the receptor selectivity, regardless of chirality and ring size, all cyclic diastereomers displayed marked $\mu$ selectivity with low potencies at the $\delta$ receptor. The retro-inverso analogs display similar or more active at $\mu$ receptor, but less active at $\delta$ receptor than the parent analogs.

• Fisheries and Aquatic Sciences
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• v.15 no.1
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• pp.15-19
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• 2012

A new cyclic peptide (six-membered amino acid), gamakamide-E (L-Leu-L-Met (SO)-L-Me-Phe-L-Leu-D-Lys-L-Phe), was isolated as a strongly bitter tasting compound from cultured oysters, Crassostrea gigas. The molecular formula of $C_{43}H_{61}N_7O_8S$ was deduced from high resolution fast atom bombardment mass spectrometry (HR FAB-MS) ($[M+H]^+$ m/z 836.4356 ${\Delta}$= -2.4 mmu). Its unique structure including a hydantoin structure was firstly elucidated by nuclear magnetic resonance (NMR) analysis. Stereochemistries of constituent amino acids were determined by chiral high performanced liquid chromatography analysis of natural and synthesized peptides.

• Journal of Microbiology and Biotechnology
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• v.21 no.8
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• pp.802-807
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• 2011

Cationic liposomes have been actively used as gene delivery vehicle because of their minimal toxicity, but their relatively low efficiency of gene delivery is the major disadvantage of these vectors. Recently, cysteine residue incorporation to HIV-1 Tat peptide increased liposomemediated transfection compared with unmodified Tat peptide. Therefore, we designed a novel modified Tat peptide having a homodimeric (Tat-CTHD, Tat-NTHD) and closed structure (cyclic Tat) simply by using the disulfide bond between cysteines to develop a more efficient and safe nonviral gene delivery system. The mixing of Tat-CTHD and Tat-NTHD with DNA before mixing with lipofectamine increased the transfection efficiency compared with unmodified Tat peptide and lipofectamine only in MCF-7 breast cancer cells and rat vascular smooth muscle cells. However, cyclic Tat did not show any improvement in the transfection efficiency. In the gel retardation assay, Tat-CTHD and Tat-NTHD showed more strong binding with DNA than unmodified Tat and cyclic Tat peptide. This enhancement was only shown when Tat-CTHD and Tat-NTHD were mixed with DNA before mixing with lipofectamine. The effects of Tat- CTHD and Tat-NTHD were also valid in the experiment using DOTAP and DMRIE instead of lipofectamine. We could not find any significant cytotoxicity in the working concentration and more usage of these peptides. In conclusion, we have designed a novel transfection-enhancing peptide by easy homodimerization of Tat peptide, and the simple mix of these novel peptides with DNA increased the gene transfer of cationic lipids more efficiently with no additional cytotoxicity.

• Journal of Microbiology and Biotechnology
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• v.17 no.7
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• pp.1198-1203
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• 2007

Conidial adhesion and appressorium formation of Magnaporthe oryzae on the rice surface are important early events in the infection process. As an initiative step to understand the mechanisms underlying these cellular processes at a biochemical level, the effect of a human fibronectin antibody (HFA) and RGD peptides on conidial adhesion and appressorium formation was evaluated. HFA inhibited conidial adhesion and appressorium formation in a dosage-dependent manner. RGD peptides also inhibited these cellular events. Conidial adhesion and appressorium formation inhibited by RGD peptides were restored by chemicals involved in the cyclic AMP-dependent signaling pathway. These results suggest that extracellular matrix proteins might be involved in conidial adhesion and appressorium formation through integrin-like receptor mediation and modulation of cAMP-dependent signaling in the cells.

• Fisheries and Aquatic Sciences
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• v.18 no.2
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• pp.131-135
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• 2015

Two new bitter-tasting cyclic peptides comprising six amino acids, namely gamakamide C and D, were isolated from cultured oysters Crassostrea gigas. Dimethylaminoazobenzene sulfonyl-amino acid analysis detected Val and Leu in gamakamide C and Ile and Leu in gamakamide D. The molecular formula of gamakamide C was determined as $C_{43}H_{60}N_{7}O_8S$ by high-resolution fast atom bombardment mass spectroscopy (HR FAB-MS) ($[M+H]^+m/z822.4200{\Delta}-2.4mmu$), and that of gamakamide D was determined as $C_{43}H_{62}N_7O_8S$ by HR FAB-MS ($[M+H]^+m/z836.4379{\Delta}-2.0mmu$). Comparison of amino acid analyses and fragment ions by MS/MS among gamakamide C, D, and E (known), the structures of gamakamide C and D were confirmed $as-{\small{L}}-Val-{\small{L}}-Met(SO)-{\small{L}}-NMe-Phe-{\small{L}}-Leu-{\small{D}}-Lys-{\small{L}}-Phe-$ and $-{\small{L}}-Ile-{\small{L}}-Met(SO)-{\small{L}}-NMe-Phe-{\small{L}}-Leu-{\small{D}}-Lys-{\small{L}}-Phe-$, respectively.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.89-97
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• 2015

The aim of this study was to investigate the involvement of dopaminergic receptors (DR) in behavioral sensitization, as measured by locomotor activity, and the over-expression of cocaine- and amphetamine-regulated transcript (CART) peptides after repeated administration of cocaine in mice. Repeated administrations of cocaine induced behavioral sensitization and CART over-expression in mice. The levels of striatal CART mRNA were significantly increased on the $3^{rd}$ day. CART peptides were over-expressed on the $5^{th}$ day in the striata of behaviorally sensitized mice. A higher proportion of $CART^+$ cells in the cocaine-treated mice were present in the nucleus accumbens (NAc) shell than in the dorsolateral (DL) part of caudate putamen (CP). The concomitant administration of both $D_1R$ and $D_2R$ antagonists, SCH 23390 ($D_1R$ selective) and raclopride ($D_2R$ selective), blocked cocaine induced-behavioral sensitization, CART over-expression, and cyclic adenosine 5'-monophosphate (cAMP)/ protein kinase A (PKA)/phospho-cAMP response element-binding protein (pCREB) signal pathways. SCH 23390 more predominantly inhibited the locomotor activity, CART over-expression, pCREB and PKA activity than raclopride. Cocaine induced-behavioral sensitization was also attenuated in the both $D_1R$ and $D_2R$ knockout (KO) mice, respectively. CART over-expression and activated cAMP/PKA/pCREB signal pathways were inhibited in the $D_1R$-KO mice, but not in the $D_2R$-KO mice. It is suggested that behavioral sensitization, CART over-expression and activated cAMP/PKA/pCREB signal pathways induced by repeated administration of cocaine could be more predominantly mediated by $D_1R$.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.2 no.2
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• pp.96-102
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• 2016

Apoptosis, a genetically determined process of programmed cell death, is considered a vital component of various processes including normal cell turnover, animal development, and tissue homeostasis. It has a crucial role in many medical disorders and hence the development of non-invasive imaging tool is highly demanded. Recently, we have developed a peptide-based radioactive probe (ApoPep-1) for apoptosis detection. In that work the potential of probe for apoptosis detection was verified, however in vivo stability of radiolabeled peptide was not enough to monitor apoptosis for extended period. In current study, we prepared cyclic ApoPep-1 peptides to improve the stability of origianl linear ApoPep-1 and carried out direct comparison studies in vitro and in vivo. A targeting efficacy of newly synthesized cyclic ApoPep-1 peptide for apoptosis was confirmed in acute myocardial infarct model.

• International Journal of Oral Biology
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• v.45 no.4
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• pp.211-217
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• 2020

Molecular mimicry is the most common mechanism that breaches self-tolerance. We previously identified autoantibodies to aquaporin-5 (AQP5) in the sera of patients with Sjögren's syndrome and found that the aquaporin of Prevotella melaninogenica (PmAqp), an oral commensal, is highly homologous to human AQP5. This study aimed to test whether PmAqp can induce anti-AQP5 autoantibodies via molecular mimicry. From the amino acid sequence of PmAqp, an immunizing peptide; i.e., PmE-L, was designed, which contained both the B cell epitope "E" and T cell epitope. C57BL/6 and BALB/c mice were subcutaneously immunized with linear or cyclic forms of PmE-L emulsified in incomplete Freund's adjuvant. The concentrations of the antibodies in sera were measured using enzyme-linked immunosorbent assays. Both linear and cyclic PmE-L induced high levels of antibodies against not only the immunized peptides but also autoantibodies against AQP5E and antibodies against PmE, a Pm homolog of AQP5E. In C57BL/6 mice; however, the cyclic form of PmE-L was more efficient than the linear form in inducing autoantibodies against AQP5E that contained a cyclic epitope. The levels of anti-PmE antibodies and anti-AQP5E autoantibodies showed a strong positive correlation (r = 0.95, p < 0.0005), suggesting molecular mimicry. Collectively, the mice produced anti-AQP5E autoantibodies in response to a PmAqp-derived peptide. This model proved to be useful for studying the mechanisms of autoantibody production by molecular mimicry.

• Korean Journal of Pharmacognosy
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• v.31 no.1
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• pp.45-50
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• 2000

The root of Pseudostellaria heterophylla Pax et Hoffm. (Caryophyllaceae) is a herbal medicine called Taejasam(太子蔘) and used as a good tonic in China that strengthens the functions of the lung and the stomach like Ginseng in Korea. It has been known to have the antitussive activity for tuberculosis, appetizing effect and antifatigue activity, and so on. Especially it has been known to generate body fluids for the severe thirst and the shortage of water in body after a febrile disease for a long time. Recently some components of cyclic peptides, pseudostellarins A,B,C,D,E,F,G, that inhibit the activity of tyrosinase, were separated from this root. In this report several biological activities including acute toxicity, analgesic activity, antifatigue activity, bile juice increasing activity, hepatoprotective activity and antiinflammatory activity were investigated. These results showed as such; $LD_{50}$ of methanol extracts was above 10,000 mg/kg. The analgesic effect was revealed in the writhing test using rats. The BuOH fractions showed a prominent antifatigue effect against immobilized stress, significant hepatoprotective activities against $CCl_4$ intoxication and inhibitory effect on carrageenin-induced edema in rat's paw.