Nitric oxide-mediated vasorelaxation effects of anti-angiotensin I-converting enzyme (ACE) peptide from Styela clava flesh tissue and its anti-hypertensive effect in spontaneously hypertensive rats

In our previous study, an anti-angiotensin I converting enzyme (ACE) peptide (Ala-His-Ile-Ile-Ile, MW: 565.3 Da) was isolated from Styela clava flesh tissue. In this study the fractions obtained during the isolation process and the finally purified peptide were examined to see if they had vasorelaxation effects in isolated rat aortas, and then the peptide was investigated for anti-hypertensive effect in spontaneously hypertensive rats (SHRs). The induction of vasorelaxation in the rat aortas was observed with the isolated fractions and the peptide from the enzymatic hydrolysate of S. clava flesh tissue and could be markedly blocked by pretreatment with the nitric oxide synthase (NOS) inhibitor, N^G-nitro-l-arginine methyl ester (l-NAME). In human endothelial cells, NO synthesis was found to be increased and eNOS phosphorylation was upregulated when the cells were cultured with the purified peptide. Furthermore, systolic blood pressure was reduced by administration of the potent vasorelaxation peptide in SHRs.     

Coumaroyl quinic acid derivatives and flavonoids from immature pear (Pyrus pyrifolia nakai) fruit

Fourteen compounds were isolated from 60% ethanol extracts of immature pear (Pyrus pyrifolia Nakai cv. Chuhwangbae) fruit using Amberlite XAD-2 column HPLC with guided DPPH radical scavenging assay. Based on MS and NMR analysis, the isolated compounds were identified as 5-O-trans-caffeoyl quinic acid methyl ester (1), malaxinic acid (2), 5-O-trans-p-coumaroyl quinic acid methyl ester (3), 5-O-cis-p-coumaroyl quinic acid methyl ester (4), 5-O-trans-p-coumaroyl quinic acid (5), trans-p-coumaric acid (6), methyl cis-p-coumarate (7), methyl trans-p-coumarate (8), 3,5-O-dicaffeoyl quinic acid (9), (-)-epicatechin (10), (S)-(+)-2-cis-abscisic acid (11), isorhamnetin 3-O-β-d-galacto-pyranoside (12), isorhamnetin-3-O-β-d-glucopyranoside (13), and isorhamnetin 3-O-α-l-rhamnopyranosyl (1→6)-O-β-d-glucopyranoside (14). Six compounds (1, 2, 6, 9, 10, and 13) were identified previously, but other compounds (3–5, 7, 8, 11, 12, and 14) were isolated for the first time from pear.     

Large-scale isolation of highly pure malaxinic acid from immature pear (Pyrus pyrifolia Nakai) fruit

Malaxinic acid [4-(O-β-d-glucopyranosyl)-3-(3′-methyl-2′-butenyl)benzoic acid; MA] is one of the main compounds contained in pear fruit. The antifungal, antibacterial, and anticancer effects of MA have been reported. However, additional evaluations on the biological activity of MA have not been fully performed due to the lack of an MA standard. Therefore, in the present study, we established a large-scale isolation method to obtain highly pure MA from immature pear (Pyrus pyrifolia Nakai) fruit. The EtOAc-soluble acidic fraction (134.75 g) of pear fruit (18 kg fresh wt.) 60% EtOH extract (1,081.9 g) was purified by Amberlite XAD-2 (H₂O/EtOH, stepwise), Diaion HP-20 (H₂O/MeOH, stepwise), and Sephadex LH-20 (80% MeOH) column chromatographies. Then, the fractions containing MA were finally purified by high performance liquid chromatography using an Amide RP-C16 column on semi-preparative scale. The isolated MA (793 mg) was >99% pure, and total recovery was estimated to be 61.7%.     

Effect of cooling rate on the surface resistivity of polymer/multi‐walled carbon nanotube nanocomposites

In this study, ethylene‐vinyl acetate copolymer (EVA) and polystyrene (PS) were melt‐mixed with multi‐walled carbon nanotube (CNT) (MWCNT), respectively. The effect of mixing time, rotor speed, and cooling rate on surface resistivity was investigated. EVA/MWCNT and PS/MWCNT nanocomposites with percolation threshold <1 wt% of MWCNT were prepared using conventional melt‐compounding method. When fast cooling was applied for these nanocomposites, a surface resistivity of 10⁶ Ω/square was obtained at around 7 wt% of MWCNT for EVA and 10⁵ Ω/square at around 3.5 wt% of MWCNT for PS. However, when slow cooling was applied, a surface resistivity of 10⁶ Ω/square was obtained at 0.75 wt% of MWCNT for EVA and 10⁵ Ω/square at around 0.5 wt% of MWCNT for PS. To the best of our knowledge, this is the first report which recognizes the importance of cooling rate on the surface resistivity of polymer/MWCNT nanocomposites. This finding may be potential to the commercialization of the CNT‐based polymer nanocomposites. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Effects of crosslinking agents on the physical properties of polyimide/amino‐functionalized graphene oxide hybrid films

The effects of crosslinking agents (crosslinkers) on polyimide (PI)/graphene oxide (GO) hybrid films were extensively investigated. The surface of GO was modified with amino groups using 4‐aminobenzylamine to improve compatibility with pyromellitic dianhydride/4,4′‐oxydianiline PI, and two kinds of crosslinkers were used: tris(4‐aminophenyl)amine and 1,3,5‐triazine‐2,4,6‐triamine (melamine). The mechanical, thermal and optical properties of the PI hybrid films were investigated. In particular, the transparency and physical properties of the PI hybrid films containing amino‐functionalized GO with homogeneous dispersion were improved. As the content of the crosslinker increased, a crosslinking network was formed between the PI chains, and the stiffness of the hybrid films was increased. The glass transition temperature, heat resistance and mechanical properties were also enhanced. The PI hybrids prepared with a rigid crosslinker exhibited higher optical transparency due to the reduction of the intermolecular charge transfer interactions with increasing interchain spacing between the PI chains. © 2018 Society of Chemical Industry     

Effective hole‐injection characteristics of organic light‐emitting diodes due to fluorinated self‐assembled monolayer embedded as a buffer layer

The electrical and optical properties of organic light‐emitting diodes (OLEDs) are demonstrated by varying the length of the alkyl chain of a fluorinated self‐assembled monolayer (F‐nSAM). OLEDs containing F‐nSAMs that have a long alkyl chain length were found to exhibit excellent properties in terms of current density, luminance, turn‐on voltage, etc. The obtained current density at 6 V, which was the highest measurement voltage, was up to about 36 times higher for an OLED including an F‐12SAM thin film with the longest chain length than for an OLED including only an indium tin oxide (ITO) substrate. With regard to luminance characteristics depending on voltage, the luminance was about 13 times higher for the OLED including the F‐12SAM thin film than for the OLED including only the ITO substrate. Also, the turn‐on voltage of the OLED including the F‐12SAM thin film was decreased by approximately 1 V compared to that of the OLED including only the ITO substrate. Although F‐nSAMs with alkyl chains have insulating film properties, F‐nSAMs with long alkyl chains exhibited good electrical and optical properties because of an improvement in the hole‐injection barrier due to a large positive shift of the vacuum level and smooth carrier injection resulting from a high contact angle due to strong hydrophobic properties caused by the good alignment properties of F‐nSAMs resulting from strong van der Waals forces between the molecules due to the long alkyl chains. © 2019 Society of Chemical Industry     

A study of HC reduction with hydrocarbon adsorber systems

Hydrocarbon adsorber is considered as a promising technology to reduce cold start HCs in automotive exhaust gas. In this study, three in-line adsorber systems were tried to reduce the cold start emission. To check the basic characteristics of adsorber converters, surface areas, TPD and TPA were examined after a hydrothermal aging. Also idle engine bench was used to find the adsorption and desorption capabilities of the adsorber systems at cold start. Finally a practicability of the adsorber systems for the LEV achievement was checked with FTP test on a 2.0 D M/T vehicle. The results of this study indicate that hydrocarbon adsorber system is one of the promising passive technologies to meet the ULEV regulation.