Transcriptomic analysis of large yellow croaker (Larimichthys crocea) reveals the suppression of the inflammatory response from Cryptocaryon irritans infection

Large yellow croaker (Larimichthys crocea) is the most productive marine fish in China. Cryptocaryon irritans is an extremely destructive parasite that causes great economic losses in large yellow croaker aquaculture industry. Therefore, it is very necessary to study the immune response of large yellow croaker in response to C. irritans infection. In this study, the transcriptomic profiles of large yellow croaker were sequenced and analyzed in the brain and head kidney at 72 h after C. irritans infection. Cytokines and chemokines related terms were significantly enriched based on the GO enrichment of down-regulated differentially expressed genes (DEGs) from the head kidney. Meanwhile, cytokine-cytokine receptor interaction was significantly enriched based on the KEGG enrichment of up-regulated DEGs from the brain and down-regulated DEGs from the head kidney, respectively. Moreover, the majority of inflammation-related DEGs were significantly up-regulated in the brain, but distinctly down-regulated in the head kidney. These results showed that the brain and head kidney might play different roles against C. irritans infection, and the inflammatory response of large yellow croaker may be restrained during C. irritans infection. Taken together, the transcriptomic analyses will be helpful to more comprehensively understand the immune mechanism of teleost against C. irritans infection, and provide a theoretical basis for the prevention and treatment of Cryptosporidiosis.

Novel Ca-Chelating Peptides from Protein Hydrolysate of Antarctic Krill (Euphausia superba): Preparation, Characterization, and Calcium Absorption Efficiency in Caco-2 Cell Monolayer Model

Antarctic krill (Euphausia superba) is the world's largest resource of animal proteins and is thought to be a high-quality resource for future marine healthy foods and functional products. Therefore, Antarctic krill was degreased and separately hydrolyzed using flavourzyme, pepsin, papain, and alcalase. Protein hydrolysate (AKH) of Antarctic krill prepared by trypsin showed the highest Ca-chelating rate under the optimized chelating conditions: a pH of 8.0, reaction time of 50 min, temperature of 50 °C, and material/calcium ratio of 1:15. Subsequently, fourteen Ca-chelating peptides were isolated from APK by ultrafiltration and a series of chromatographic methods and identified as AK, EAR, AEA, VERG, VAS, GPK, SP, GPKG, APRGH, GVPG, LEPGP, LEKGA, FPPGR, and GEPG with molecular weights of 217.27, 374.40, 289.29, 459.50, 275.30, 300.36, 202.21, 357.41, 536.59, 328.37, 511.58, 516.60, 572.66, and 358.35 Da, respectively. Among fourteen Ca-chelating peptides, VERG presented the highest Ca-chelating ability. Ultraviolet spectrum (UV), Fourier Transform Infrared (FTIR), and scanning electron microscope (SEM) analysis indicated that the VERG-Ca chelate had a dense granular structure because the N-H, C=O and -COOH groups of VERG combined with Ca2+. Moreover, the VERG-Ca chelate is stable in gastrointestinal digestion and can significantly improve Ca transport in Caco-2 cell monolayer experiments, but phytate could significantly reduce the absorption of Ca derived from the VERG-Ca chelate. Therefore, Ca-chelating peptides from protein hydrolysate of Antarctic krill possess the potential to serve as a Ca supplement in developing healthy foods.

Angiotensin-I-Converting Enzyme (ACE)-Inhibitory Peptides from the Collagens of Monkfish (Lophius litulon) Swim Bladders: Isolation, Characterization, Molecular Docking Analysis and Activity Evaluation

The objective of this study was to isolate and characterize collagen and angiotensin-I-converting enzyme (ACE)-inhibitory (ACEi) peptides from the swim bladders of monkfish (Lophius litulon). Therefore, acid-soluble collagen (ASC-M) and pepsin-soluble collagen (PSC-M) with yields of 4.27 ± 0.22% and 9.54 ± 0.51%, respectively, were extracted from monkfish swim bladders using acid and enzyme methods. The ASC-M and PSC-M contained Gly (325.2 and 314.9 residues/1000 residues, respectively) as the major amino acid, but they had low imino acid content (192.5 and 188.6 residues/1000 residues, respectively) in comparison with collagen from calf skins (CSC) (216.6 residues/1000 residues). The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) patterns and ultraviolet (UV) absorption spectrums of ASC-M and PSC-M illustrated that they were mainly composed of type I collagen. Subsequently, three ACEi peptides were isolated from a PSC-M hydrolysate prepared via a double-enzyme system (alcalase + neutrase) and identified as SEGPK (MHP6), FDGPY (MHP7) and SPGPW (MHP9), with molecular weights of 516.5, 597.6 and 542.6 Da, respectively. SEGPK, FDGPY and SPGPW displayed remarkable anti-ACE activity, with IC50 values of 0.63, 0.94 and 0.71 mg/mL, respectively. Additionally, a molecular docking assay demonstrated that the affinities of SEGPK, FDGPY and SPGPW with ACE were -7.3, -10.9 and -9.4 kcal/mol, respectively. The remarkable ACEi activity of SEGPK, FDGPY and SPGPW was due to their connection with the active pockets and/or sites of ACE via hydrogen bonding, hydrophobic interaction and electrostatic force. Moreover, SEGPK, FDGPY and SPGPW could protect HUVECs by controlling levels of nitric oxide (NO) and endothelin-1 (ET-1). Therefore, this work provides an effective means for the preparation of collagens and novel ACEi peptides from monkfish swim bladders, and the prepared ACEi peptides, including SEGPK, FDGPY and SPGPW, could serve as natural functional components in the development of health care products to control hypertension.

Molecular characterization and expression of twenty interleukin-17 transcripts in the common Chinese cuttlefish (Sepiella japonica) in response to Vibrio harveyi infection

The common Chinese cuttlefish (Sepiella japonica) is an essential species for stock enhancement by releasing juveniles in the East China Sea now. S. japonica is susceptible to bacterial diseases during parental breeding. In vertebrates, Interleukin-17 (IL-17) cytokine family plays critical roles in both acute and chronic inflammatory responses. In Cephalopoda, few studies have been reported on IL-17 genes so far. In this study, twenty IL-17 transcripts obtained from S. japonica were divided into eight groups (designated as Sj_IL-17-1 to Sj_IL-17-8). Multiple alignment analysis showed that IL-17s in S. japonica and human both contained four β-folds (β1-β4), except for Sj_IL-17-6 with two β-folds (β1 and β2), and the third and fourth β-folds of Sj_IL-17-5 and Sj_IL-17-8 were longer than those of other Sj_IL-17. Protein structure and conserved motifs analysis demonstrated that Sj_IL-17-5 and Sj_IL-17-6 displayed different protein structure with respect to other six Sj_IL-17 proteins. The homology and phylogenetic analysis of amino acids showed that Sj_IL-17-5, Sj_IL-17-6 and Sj_IL-17-8 had low homology with the other five Sj_IL-17s. Eight Sj_IL-17 mRNAs were ubiquitously expressed in ten examined tissues, with dominant expression in the hemolymph. qRT-PCR data showed that the mRNA expression levels of Sj_IL-17-2, Sj_IL-17-3, Sj_IL-17-6, and Sj_IL-17-8 were significantly up-regulated in infected cuttlefishes, and Sj_IL-17-2, Sj_IL-17-6, Sj_IL-17-7, and Sj_IL-17-8 mRNAs Awere significantly up-regulated after bath infection of Vibrio harveyi, suggesting that certain Sj_IL-17s were involved in the immune response of S. japonica against V. harveyi infection. These results implied that Sj_IL-17s were likely to have distinct functional diversification. This study aims to understand the involvement of Sj_IL-17 genes in immune responses of cuttlefish against bacterial infections.

Antioxidant Peptides from Monkfish Swim Bladders: Ameliorating NAFLD In Vitro by Suppressing Lipid Accumulation and Oxidative Stress via Regulating AMPK/Nrf2 Pathway

In this study, we investigate the ameliorating functions of QDYD (MSP2), ARW (MSP8), DDGGK (MSP10), YPAGP (MSP13) and DPAGP (MSP18) from monkfish swim bladders on an FFA-induced NAFLD model of HepG2 cells. The lipid-lowering mechanisms revealed that these five oligopeptides can up-regulate the expression of phospho-AMP-activated protein kinase (p-AMPK) proteins to inhibit the expression of the sterol regulatory element binding protein-1c (SREBP-1c) proteins on increasing lipid synthesis and up-regulating the expression of the PPAP-α and CPT-1 proteins on promoting the β-oxidation of fatty acids. Moreover, QDYD (MSP2), ARW (MSP8), DDGGK (MSP10), YPAGP (MSP13) and DPAGP (MSP18) can significantly inhibit reactive oxygen species' (ROS) production, promote the activities of intracellular antioxidases (superoxide dismutase, SOD; glutathione peroxidase, GSH-PX; and catalase, CAT) and bring down the content of malondialdehyde (MDA) derived from lipid peroxidation. Further investigations revealed that the regulation of these five oligopeptides on oxidative stress was achieved through activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway to raise the expression levels of the heme oxygenase 1 (HO-1) protein and downstream antioxidant proteases. Therefore, QDYD (MSP2), ARW (MSP8), DDGGK (MSP10), YPAGP (MSP13) and DPAGP (MSP18) could serve as candidate ingredients to develop functional products for treating NAFLD.

Marine Bioactive Peptides-Structure, Function and Application

Marine organisms live in harsh marine habitats, causing them to have significantly different and more diverse proteins than those of terrestrial organisms [...].

Eighteen Novel Bioactive Peptides from Monkfish (Lophius litulon) Swim Bladders: Production, Identification, Antioxidant Activity, and Stability

In the study, papain was chosen from five proteases to hydrolyze proteins of monkfish swim bladders for effectively utilizing monkfish (Lophius litulon) processing byproducts, and the hydrolysis conditions of papain were optimized as hydrolysis temperature of 65 °C, pH 7.5, enzyme dose 2.5% and time 5 h using single-factor and orthogonal experiments. Eighteen peptides were purified from the swim bladder hydrolysate of monkfish by ultrafiltration and gel permeation chromatography methods and identified as YDYD, QDYD, AGPAS, GPGPHGPSGP, GPK, HRE, GRW, ARW, GPTE, DDGGK, IGPAS, AKPAT, YPAGP, DPT, FPGPT, GPGPT, GPT and DPAGP, respectively. Among eighteen peptides, GRW and ARW showed significant DPPH· scavenging activities with EC₅₀ values of 1.053 ± 0.003 and 0.773 ± 0.003 mg/mL, respectively; YDYD, QDYD, GRW, ARW and YPAGP revealed significantly HO· scavenging activities with EC₅₀ values of 0.150 ± 0.060, 0.177 ± 0.035, 0.201 ± 0.013, 0.183 ± 0.0016 and 0.190 ± 0.010 mg/mL, respectively; YDYD, QDYD, ARW, DDGGK and YPAGP have significantly O2-· scavenging capability with EC₅₀ values of 0.126 ± 0.0005, 0.112 ± 0.0028, 0.127 ± 0.0002, 0.128 ± 0.0018 and 0.107 ± 0.0002 mg/mL, respectively; and YDYD, QDYD and YPAGP showed strong ABTS⁺· scavenging ability with EC₅₀ values of 3.197 ± 0.036, 2.337 ± 0.016 and 3.839 ± 0.102 mg/mL, respectively. YDYD, ARW and DDGGK displayed the remarkable ability of lipid peroxidation inhibition and Ferric-reducing antioxidant properties. Moreover, YDYD and ARW can protect Plasmid DNA and HepG2 cells against H₂O₂-induced oxidative stress. Furthermore, eighteen isolated peptides had high stability under temperatures ranging from 25-100 °C; YDYD, QDYD, GRW and ARW were more sensitive to alkali treatment, but DDGGK and YPAGP were more sensitive to acid treatment; and YDYD showed strong stability treated with simulated GI digestion. Therefore, the prepared antioxidant peptides, especially YDYD, QDYD, GRW, ARW, DDGGK and YPAGP from monkfish swim bladders could serve as functional components applied in health-promoting products because of their high-antioxidant functions.

Novel angiotensin-converting enzyme inhibitory peptides from tuna byproducts—milts: Preparation, characterization, molecular docking study, and antioxidant function on H2O2-damaged human umbilical vein endothelial cells

To prepare peptides with high angiotensin-converting enzyme (ACE) inhibitory (ACEi) activity, Alcalase was screened from five proteases and employed to prepare protein hydrolysate (TMH) of skipjack tuna (Katsuwonus pelamis) milts. Subsequently, 10 novel ACEi peptides were isolated from the high-ACEi activity TMH and identified as Tyr-Asp-Asp (YDD), Thr-Arg-Glu (TRE), Arg-Asp-Tyr (RDY), Thr-Glu-Arg-Met (TERM), Asp-Arg-Arg-Tyr-Gly (DRRYG), Ile-Cys-Tyr (ICY), Leu-Ser-Phe-Arg (LSFR), Gly-Val-Arg-Phe (GVRF), Lys-Leu-Tyr-Ala-Leu-Phe (KLYALF), and Ile-Tyr-Ser-Pro (IYSP) with molecular weights of 411.35, 404.41, 452.45, 535.60, 665.69, 397.48, 521.61, 477.55, 753.91, and 478.53 Da, respectively. Among them, the IC₅₀ values of ICY, LSFR, and IYSP on ACE were 0.48, 0.59, and 0.76 mg/mL, respectively. The significant ACEi activity of ICY, LSFR, and IYSP with affinities of −7.0, −8.5, and −8.3 kcal/mol mainly attributed to effectively combining with the ACEi active sites through hydrogen bonding, electrostatic force, and hydrophobic interaction. Moreover, ICY, LSFR, and IYSP could positively influence the production of nitric oxide (NO) and endothelin-1 (ET-1) secretion in human umbilical vein endothelial cells (HUVECs) and weaken the adverse impact of norepinephrine (NE) on the production of NO and ET-1. In addition, ICY, LSFR, and IYSP could provide significant protection to HUVECs against H₂O₂ damage by increasing antioxidase levels to decrease the contents of reactive oxide species and malondialdehyde. Therefore, the ACEi peptides of ICY, LSFR, and IYSP are beneficial functional molecules for healthy foods against hypertension and cardiovascular diseases.

Preparation, Characterization, and Cytoprotective Effects on HUVECs of Fourteen Novel Angiotensin-I-Converting Enzyme Inhibitory Peptides From Protein Hydrolysate of Tuna Processing By-Products

To effectively utilize skipjack tuna (Katsuwonus pelamis) processing by-products to prepare peptides with high angiotensin-I-converting enzyme (ACE) inhibitory (ACEi) activity, Neutrase was selected from five kinds of protease for hydrolyzing skipjack tuna dark muscle, and its best hydrolysis conditions were optimized as enzyme dose of 1.6%, pH 6.7, and temperature of 50°C using single factor and response surface experiments. Subsequently, 14 novel ACEi peptides were prepared from the high ACEi protein hydrolysate and identified as TE, AG, MWN, MEKS, VK, MQR, MKKS, VKRT, IPK, YNY, LPRS, FEK, IRR, and WERGE. MWN, MEKS, MKKS, and LPRS displayed significantly ACEi activity with IC₅₀ values of 0.328 ± 0.035, 0.527 ± 0.030, 0.269 ± 0.006, and 0.495 ± 0.024 mg/mL, respectively. Furthermore, LPRS showed the highest increasing ability on nitric oxide (NO) production among four ACEi peptides combining the direct increase and reversing the negative influence of norepinephrine (NE), and MKKS showed the highest ability on directly decreasing and reversing the side effects of NE on the secretion level of endothelin-1 (ET-1) among four ACEi peptides. These findings demonstrate that seafood by-product proteins are potential ACEi peptide sources and prepared ACEi peptides from skipjack tuna dark muscle, which are beneficial components for functional food against hypertension and cardiovascular diseases.

Preparation, Identification, Molecular Docking Study and Protective Function on HUVECs of Novel ACE Inhibitory Peptides from Protein Hydrolysate of Skipjack Tuna Muscle

To prepare bioactive peptides with high angiotensin-I-converting enzyme (ACE)-inhibitory (ACEi) activity, Alcalase was selected from five kinds of protease for hydrolyzing Skipjack tuna (Katsuwonus pelamis) muscle, and its best hydrolysis conditions were optimized using single factor and response surface experiments. Then, the high ACEi protein hydrolysate (TMPH) of skipjack tuna muscle was prepared using Alcalase under the optimum conditions of enzyme dose 2.3%, enzymolysis temperature 56.2 °C, and pH 9.4, and its ACEi activity reached 72.71% at 1.0 mg/mL. Subsequently, six novel ACEi peptides were prepared from TMPH using ultrafiltration and chromatography methods and were identified as Ser-Pro (SP), Val-Asp-Arg-Tyr-Phe (VDRYF), Val-His-Gly-Val-Val (VHGVV), Tyr-Glu (YE), Phe-Glu-Met (FEM), and Phe-Trp-Arg-Val (FWRV), with molecular weights of 202.3, 698.9, 509.7, 310.4, 425.6, and 606.8 Da, respectively. SP and VDRYF displayed noticeable ACEi activity, with IC₅₀ values of 0.06 ± 0.01 and 0.28 ± 0.03 mg/mL, respectively. Molecular docking analysis illustrated that the high ACEi activity of SP and VDRYF was attributed to effective interaction with the active sites/pockets of ACE by hydrogen bonding, electrostatic force, and hydrophobic interaction. Furthermore, SP and VDRYF could significantly up-regulate nitric oxide (NO) production and down-regulate endothelin-1 (ET-1) secretion in HUVECs after 24 h treatment, but also abolish the negative effect of 0.5 μM norepinephrine (NE) on the generation of NO and ET-1. Therefore, ACEi peptides derived from skipjack tuna (K. pelamis) muscle, especially SP and VDRYF, are beneficial components for functional food against hypertension and cardiovascular diseases.

Twelve Antioxidant Peptides From Protein Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Roe Prepared by Flavourzyme: Purification, Sequence Identification, and Activity Evaluation

For using aquatic by-products to manufacture high-value products, Skipjack tuna (Katsuwonus pelamis) roes were degreased, pretreated with microwave, and hydrolyzed using five proteases. The protein hydrolysate (TRPH) generated using Flavourzyme displayed the strongest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. Twelve antioxidative peptides were prepared from TRPH by ultrafiltration and chromatography methods and determined to be SGE, VDTR, AEM, QDHKA, TVM, QEAE, YEA, VEP, AEHNH, QEP, QAEP, and YVM with molecular weights of 291.24, 489.50, 349.41, 597.59, 349.44, 475.42, 381.36, 343.37, 606.58, 372.35, 443.42, and 411.49 Da, respectively. AEM, QDHKA, YEA, AEHNH, and YVM presented the strongest scavenging activity on DPPH radical (EC₅₀ values of 0.250±0.035, 0.279±0.017, 0.233±0.012, 0.334±0.011, and 0.288±0.015 mg/ml, respectively), hydroxyl radical (EC₅₀ values of 0.456±0.015, 0.536±0.021, 0.476 ± 0.051, 0.369 ± 0.052, and 0.413 ± 0.019 mg/ml, respectively), and superoxide anion free radical (EC₅₀ values of 0.348 ± 0.018, 0.281 ± 0.013, 0.305 ± 0.022, 0.198 ± 0.011, and 0.425 ± 0.021 mg/ml, respectively). Moreover, AEM, QDHKA, YEA, AEHNH, and YVM presented high lipid peroxidation inhibition ability, Ferric-reducing power, and significant protective function on H₂O₂-induced Chang liver cells. Therefore, AEM, QDHKA, YEA, AEHNH, and YVM could be natural antioxidant ingredients used in pharmaceutical and functional products.

Purification, Identification, Activity Evaluation, and Stability of Antioxidant Peptides from Alcalase Hydrolysate of Antarctic Krill (Euphausia superba) Proteins

For utilizing the largest source of marine proteins, Antarctic krill (Euphausia superba) proteins were defatted and hydrolyzed separately using pepsin, alcalase, papain, trypsin, and netrase, and alcalase hydrolysate (EPAH) showed the highest DPPH radical (DPPH·) and hydroxyl radical (HO·) scavenging activity among five hydrolysates. Using ultrafiltration and chromatography methods, fifteen antioxidant peptides were purified from EPAH and identified as Asn-Gln-Met (NQM), Trp-Phe-Pro-Met (WFPM), Gln-Asn-Pro-Thr (QNPT), Tyr-Met-Asn-Phe (YMNF), Ser-Gly-Pro-Ala (SGPA), Ser-Leu-Pro-Tyr (SLPY), Gln-Tyr-Pro-Pro-Met-Gln-Tyr (QYPPMQY), Glu-Tyr-Glu-Ala (EYEA), Asn-Trp-Asp-Asp-Met-Arg-Ile-Val-Ala-Val (NWDDMRIVAV), Trp-Asp-Asp-Met-Glu-Arg-Leu-Val-Met-Ile (WDDMERLVMI), Asn-Trp-Asp-Asp-Met-Glu-Pro-Ser-Phe (NWD-DMEPSF), Asn-Gly-Pro-Asp-Pro-Arg-Pro-Ser-Gln-Gln (NGPDPRPSQQ), Ala-Phe-Leu-Trp-Asn (AFLWA), Asn-Val-Pro-Asp-Met (NVPDM), and Thr-Phe-Pro-Ile-Tyr-Asp-Tyr-Pro-Gln (TFPIYDPQ), respectively, using a protein sequencer and ESI/MS. Among fifteen antioxidant peptides, SLPY, QYPPMQY and EYEA showed the highest scavenging activities on DPPH· (EC₅₀ values of 1.18 ± 0.036, 1.547 ± 0.150, and 1.372 ± 0.274 mg/mL, respectively), HO· (EC₅₀ values of 0.826 ± 0.027, 1.022 ± 0.058, and 0.946 ± 0.011 mg/mL, respectively), and superoxide anion radical (EC₅₀ values of 0.789 ± 0.079, 0.913 ± 0.007, and 0.793 ± 0.056 mg/mL, respectively). Moreover, SLPY, QYPPMQY and EYEA showed strong reducing power, protective capability against H₂O₂-damaged plasmid DNA, and lipid peroxidation inhibition ability. Furthermore, SLPY, QYPPMQY, and EYEA had high stability under temperatures lower than 80 °C, pH values ranged from 6-8, and simulated GI digestion for 180 min. The results showed that fifteen antioxidant peptides from alcalase hydrolysate of Antarctic krill proteins, especially SLPY, QYPPMQY and EYEA, might serve as effective antioxidant agents applied in food and health products.

Antioxidant Peptides from the Protein Hydrolysate of Monkfish (Lophius litulon) Muscle: Purification, Identification, and Cytoprotective Function on HepG2 Cells Damage by H2O2

In the work, defatted muscle proteins of monkfish (Lophius litulon) were separately hydrolyzed by pepsin, trypsin, and in vitro gastrointestinal (GI) digestion methods, and antioxidant peptides were isolated from proteins hydrolysate of monkfish muscle using ultrafiltration and chromatography processes. The antioxidant activities of isolated peptides were evaluated using radical scavenging and lipid peroxidation assays and H2O2-induced model of HepG2 cells. In which, the cell viability, reactive oxygen species (ROS) content, and antioxidant enzymes and malondialdehyde (MDA) levels were measured for evaluating the protective extent on HepG2 cells damaged by H2O2. The results indicated that the hydrolysate (MPTH) prepared using in vitro GI digestion method showed the highest degree of hydrolysis (27.24 ± 1.57%) and scavenging activity on a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (44.54 ± 3.12%) and hydroxyl radical (41.32 ± 2.73%) at the concentration of 5 mg protein/mL among the three hydrolysates. Subsequently, thirteen antioxidant peptides (MMP-1 to MMP-13) were isolated from MPTH. According to their DPPH radical and hydroxyl radical scavenging activity, three peptides with the highest antioxidant activity were selected and identified as EDIVCW (MMP-4), MEPVW (MMP-7), and YWDAW (MMP-12) with molecular weights of 763.82, 660.75, and 739.75 Da, respectively. EDIVCW, MEPVW, and YWDAW showed high scavenging activities on DPPH radical (EC50 0.39, 0.62, and 0.51 mg/mL, respectively), hydroxyl radical (EC50 0.61, 0.38, and 0.32 mg/mL, respectively), and superoxide anion radical (EC50 0.76, 0.94, 0.48 mg/mL, respectively). EDIVCW and YWDAW showed equivalent inhibiting ability on lipid peroxidation with glutathione in the linoleic acid model system. Moreover, EDIVCW, MEPVW, and YWDAW had no cytotoxicity to HepG2 cells at the concentration of 100.0 µM and could concentration-dependently protect HepG2 cells from H2O2-induced oxidative damage through decreasing the levels of reactive oxygen species (ROS) and MDA and activating intracellular antioxidant enzymes of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). These present results indicated that the protein hydrolysate and isolated antioxidant peptides from monkfish muscle, especially YWDAW could serve as powerful antioxidants applied in the treatment of some liver diseases and healthcare products associated with oxidative stress.

Gelatin and Antioxidant Peptides from Gelatin Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Scales: Preparation, Identification and Activity Evaluation

For full use of fish by-products, scale gelatin (TG) and antioxidant peptides (APs) of skipjack tuna (Katsuwonus pelamis) were prepared, and their properties were characterized using an amino acid analyzer, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier transform infrared spectroscopy (FTIR), electrospray ionization mass spectrometers (ESI-MS), and radical scavenging assays. The results indicate that TG with a yield of 3.46 ± 0.27% contained Gly (327.9 ± 5.2 residues/1000 residues) as the major amino acid and its imino acid content was 196.1 residues/1000 residues. The structure of TG was more unstable than that of type I collagen from scales of skipjack tuna (TC) and TG was more suitable for preparation of hydrolysate by protease than mammalian gelatins. Therefore, TG was separately hydrolyzed under five proteases (pepsin, papain, trypsin, neutrase, and alcalase) and ten APs (TGP1–TGP10) were isolated from the alcalase-hydrolysate. Among them, TGP5, TGP7, and TGP9 with high antioxidant activity were identified as His-Gly-Pro-Hyp-Gly-Glu (TGP5), Asp-Gly-Pro-Lys-Gly-His (TGP7) and Met-Leu-Gly-Pro-Phe-Gly-Pro-Ser (TGP9), respectively. Furthermore, TGP5, TGP7, and TGP9 exhibited a high radical scavenging capability on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC₅₀ values of 1.34, 0.54, and 0.67 mg/mL, respectively), hydroxyl radical (EC₅₀ values of 1.03, 0.41, and 0.74 mg/mL, respectively), and superoxide anion radical (EC₅₀ values of 1.19, 0.71, and 1.59 mg/mL, respectively). These results suggest that three APs (TGP5, TGP7, and TGP9), especially TGP7, have a strong antioxidant activity and could act as potential antioxidant ingredients applied in functional products.

Antioxidant Peptides from the Protein Hydrolysate of Spanish Mackerel (Scomberomorous niphonius) Muscle by in Vitro Gastrointestinal Digestion and Their In Vitro Activities

For the full use of Spanish mackerel (Scomberomorous niphonius) muscle to produce antioxidant peptides, the proteins of Spanish mackerel muscle were separately hydrolyzed under five kinds of enzymes and in vitro gastrointestinal digestion, and antioxidant peptides were isolated from the protein hydrolysate using ultrafiltration and multiple chromatography methods. The results showed that the hydrolysate (SMPH) prepared using in vitro GI digestion showed the highest degree of hydrolysis (27.45 ± 1.76%) and DPPH radical scavenging activity (52.58 ± 2.68%) at the concentration of 10 mg protein/mL among the six protein hydrolysates, and 12 peptides (SMP-1 to SMP-12) were prepared from SMPH. Among them, SMP-3, SMP-7, SMP-10, and SMP-11 showed the higher DPPH radical scavenging activities and were identified as Pro-Glu-Leu-Asp-Trp (PELDW), Trp-Pro-Asp-His-Trp (WPDHW), and Phe-Gly-Tyr-Asp-Trp-Trp (FGYDWW), and Tyr-Leu-His-Phe-Trp (YLHFW), respectively. PELDW, WPDHW, FGYDWW, and YLHFW showed high scavenging activities on DPPH radical (EC₅₀ 1.53, 0.70, 0.53, and 0.97 mg/mL, respectively), hydroxyl radical (EC₅₀ 1.12, 0.38, 0.26, and 0.67 mg/mL, respectively), and superoxide anion radical (EC₅₀ 0.85, 0.49, 0.34, and 1.37 mg/mL, respectively). Moreover, PELDW, WPDHW, FGYDWW, and YLHFW could dose-dependently inhibit lipid peroxidation in the linoleic acid model system and protect plasmid DNA (pBR322DNA) against oxidative damage induced by H₂O₂ in the tested model systems. In addition, PELDW, WPDHW, FGYDWW, and YLHFW could retain their high activities when they were treated under a low temperature (<60 °C) and a moderate pH environment (pH 5–9). These present results indicate that the protein hydrolysate, fractions, and isolated peptides from Spanish mackerel muscle have strong antioxidant activity and might have the potential to be used in health food products.

Identification and Active Evaluation of Antioxidant Peptides from Protein Hydrolysates of Skipjack Tuna (Katsuwonus pelamis) Head

For the full use of fish by-products to produce antioxidant peptides, skipjack tuna (Katsuwonus pelamis) heads generated during can processing were defatted and hydrolyzed using the in vitro gastrointestinal (GI) digestion (pepsin–trypsin system) method and six antioxidant peptides (P1 to P6) were purified from the head hydrolysate (KPH) using ultrafiltration and serial chromatography methods. Six isolated peptides (P1 to P6) were identified as Val-Glu-Glu (VEE, P1), Trp-Met-Phe-Asp-Trp (WMFDW, P2), Asp-Ala-Gly-Pro-Tyr-Gly-Pro-Ile (DAGPYGPI, P3), Trp-Met-Gly-Pro-Tyr (WMGPY, P4), Glu-Arg-Gly-Pro-Leu-Gly-Pro-His (ERGPLGPH, P5), and Glu-Met- Gly-Pro-Ala (EMGPA, P6), respectively, using a protein sequencer and electrospray ionization-mass spectrometer. Among skipjack tuna head hydrolysates, fractions, and six isolated peptides (P1 to P6), WMFDW (P2), WMGPY (P4), and EMGPA (P6) showed the highest radical scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH) (EC₅₀ values of 0.31, 0.33, and 0.46 mg/mL for WMFDW, WMGPY, and EMGPA, respectively), hydroxyl (EC₅₀ values of 0.30, 0.43, and 0.52 mg/mL for WMFDW, WMGPY, and EMGPA, respectively), and superoxide anion (EC₅₀ values of 0.56, 0.38, and 0.71 mg/mL for WMFDW, WMGPY, and EMGPA, respectively). Moreover, WMFDW, WMGPY, and EMGPA showed strong capability in reducing power and lipd peroxidation inhibition in the linoleic acid system. In addition, WMFDW, WMGPY, and EMGPA can retain strong antioxidant activity at temperatures lower than 60 °C and pH values ranged from 5 to 9. The results showed that six isolated peptides (P1 to P6) from skipjack tuna heads, especially WMFDW, WMGPY, and EMGPA, might be applied in health care products acting as powerful antioxidant agents.

Four Antioxidant Peptides from Protein Hydrolysate of Red Stingray (Dasyatis akajei) Cartilages: Isolation, Identification, and In Vitro Activity Evaluation

In the work, water-soluble proteins of red stingray (Dasyatis akajei) cartilages were extracted by guanidine hydrochloride and hydrolyzed using trypsin. Subsequently, four antioxidant peptides (RSHP-A, RSHP-B, RSHP-C, and RSHP-D) were isolated from the water-soluble protein hydrolysate while using ultrafiltration and chromatographic techniques, and the amino acid sequences of RSHP-A, RSHP-B, RSHP-C, and RSHP-D were identified as Val-Pro-Arg (VPR), Ile-Glu-Pro-His (IEPH), Leu-Glu-Glu--Glu-Glu (LEEEE), and Ile-Glu-Glu-Glu-Gln (IEEEQ), with molecular weights of 370.46 Da, 494.55 Da, 647.64 Da, and 646.66 Da, respectively. VPR, IEPH, LEEEE, and IEEEQ exhibited good scavenging activities on the DPPH radical (EC50 values of 4.61, 1.90, 3.69, and 4.01 mg/mL, respectively), hydroxyl radical (EC50 values of 0.77, 0.46, 0.70, and 1.30 mg/mL, respectively), superoxide anion radical (EC50 values of 0.08, 0.17, 0.15, and 0.16 mg/mL, respectively), and ABTS cation radical (EC50 values of 0.15, 0.11, 0.19, and 0.18 mg/mL, respectively). Among the four isolated antioxidant peptides, IEPH showed the strongest reducing power and lipid peroxidation inhibition activity, but LEEEE showed the highest Fe2+-chelating ability. The present results suggested that VPR, IEPH, LEEEE, and IEEEQ might have the possibility of being an antioxidant additive that is used in functional food and pharmaceuticals.

Eight Collagen Peptides from Hydrolysate Fraction of Spanish Mackerel Skins: Isolation, Identification, and In Vitro Antioxidant Activity Evaluation

A previous report indicated that collagen hydrolysate fraction (F7) from Spanish mackerel (Scomberomorous niphonius) skins showed high reducing power and radical scavenging activities on 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (EC50 value of 1.57 mg/mL) and hydroxyl (EC50 value of 1.20 mg/mL). In this work, eight peptides were isolated from F7 and identified as Gly-Pro-Tyr (GPY, 335.31 Da), Gly-Pro-Thr-Gly-Glu (GPTGE, 459.47 Da), Pro-Phe-Gly-Pro-Asp (PFGPD, 531.52 Da), Gly-Pro-Thr-Gly-Ala-Lys (GPTGAKG, 586.65 Da), Pro-Tyr-Gly-Ala-Lys-Gly (PYGAKG, 591.69 Da), Gly-Ala-Thr-Gly-Pro-Gln-Gly (GATGPQG, 586.61 Da), Gly-Pro-Phe-Gly-Pro-Met (GPFGPM, 604.73 Da), and Tyr-Gly-Pro-Met (YGPM, 466.50 Da), respectively. Among them, PFGPD, PYGAKG, and YGPM exhibited strong radical scavenging activities on DPPH (EC50 values of 0.80, 3.02, and 0.72 mg/mL for PFGPD, PYGAKG, and YGPM, respectively), hydroxyl (EC50 values of 0.81, 0.66, and 0.88 mg/mL for PFGPD, PYGAKG, and YGPM, respectively), superoxide anion (EC50 values of 0.91, 0.80, and 0.73 mg/mL for PFGPD, PYGAKG, and YGPM, respectively), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) cation (EC50 values of 0.86, 1.07, and 0.82 mg/mL for PFGPD, PYGAKG, and YGPM, respectively) in a positive concentration-activity relationship. Furthermore, PFGPD, PYGAKG, and YGPM could effectively reduce Fe3+ to Fe2+ and inhibit lipid peroxidation. Hence, eight collagen peptides from hydrolysate of Spanish mackerel skins might be served as antioxidant candidates for various industrial applications.

Preparation and Characterization of Gelatin and Antioxidant Peptides from Gelatin Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Bone Stimulated by in vitro Gastrointestinal Digestion

In China, a large amount of fish bones are produced during the processing of tuna cans production. For full use of those by-products, gelatin (STB-G) with a yield of 6.37 ± 0.64% was extracted from skipjack tuna (Katsuwonus pelamis) bone using water at 60 °C for 8 h. Amino acid analysis showed that STB-G contained Gly (340.3 residues/1000 residues) as the major amino acid and its imino acid content was 177.3 residues/1000 residues. Amino acid composition, SDS-PAGE, and Fourier transform infrared (FTIR) spectrum investigations confirmed that the physicochemical properties of STB-G were similar to those of type I collagen from skipjack tuna bone (STB-C), but partial high molecular weight components of STB-G were degraded during the extraction process, which induced that the gelatin was easier to be hydrolyzed by protease than mammalian gelatins and was suitable for preparation of hydrolysate. Therefore, STB-G was hydrolyzed under in vitro gastrointestinal digestion (pepsin-trypsin system) and five antioxidant peptides were purified from the resulted hydrolysate (STB-GH) and identified as GPDGR, GADIVA, GAPGPQMV, AGPK, and GAEGFIF, respectively. Among the gelatin hydrolysate, fractions, and isolated peptides, GADIVA and GAEGFIF exhibited the strongest scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC50 0.57 and 0.30 mg/mL), hydroxyl radical (EC50 0.25 and 0.32 mg/mL), superoxide anion radical (EC50 0.52 and 0.48 mg/mL), and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical (EC50 0.41 and 0.21 mg/mL). Moreover, GADIVA and GAEGFIF showed a high inhibiting ability on lipid peroxidation in a linoleic acid model system. The strong activities of five isolated peptides profited by their small molecular sizes and the antioxidant amino acid residues in their sequences. These results suggested that five isolated peptides (STP1⁻STP5), especially GADIVA and GAEGFIF, might serve as potential antioxidants applied in health food industries.

Preparation, Identification, and Activity Evaluation of Eight Antioxidant Peptides from Protein Hydrolysate of Hairtail (Trichiurus japonicas) Muscle

In this report, protein of hairtail (Trichiurus japonicas) muscle was separately hydrolyzed using five kinds of proteases (alcalase, trypsin, neutrase, pepsin, and papain), and the papain- and alcalase-hydrolysates showed higher 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH•) and hydroxyl radical (HO•) scavenging activity than other three protease hydrolysates. Therefore, the protein hydrolysate of hairtail muscle (HTP) was prepared using binary-enzymes hydrolysis process (papain + alcalase). Subsequently, eight antioxidant peptides were purified from HTP using membrane ultrafiltration and chromatography technology, and their amino acid sequences were identified as Gln-Asn-Asp-Glu-Arg (TJP1), Lys-Ser (TJP2), Lys-Ala (TJP3), Ala-Lys-Gly (TJP4), Thr-Lys-Ala (TJP5), Val-Lys (TJP6), Met-Lys (TJP7), and Ile-Tyr-Gly (TJP8) with molecular weights of 660.3, 233.0, 217.1, 274.1, 318.0, 245.1, 277.0, and 351.0 Da, respectively. TJP3, TJP4, and TJP8 exhibited strong scavenging activities on DPPH• (EC₅₀ 0.902, 0.626, and 0.663 mg/mL, respectively), HO• (EC₅₀ 1.740, 2.378, and 2.498 mg/mL, respectively), superoxide anion radical (EC₅₀ 2.082, 2.538, and 1.355 mg/mL, respectively), and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical (EC₅₀ 1.652, 0.831, and 0.586 mg/mL, respectively). Moreover, TJP3, TJP4, and TJP8 showed higher reducing power and inhibiting ability on lipid peroxidation in a linoleic acid model system. These results suggested that eight isolated peptides (TJP1 to TJP8), especially TJP3, TJP4, and TJP8 might serve as potential antioxidants applied in the pharmaceutical and health food industries.

Physicochemical properties of acid- and pepsin-soluble collagens from the cartilage of Siberian sturgeon

To look for the collagen alternatives of mammalian cartilages from aquatics and their by-products, acid-soluble collagen (ASC-SC) and pepsin-soluble collagen (PSC-SC) were extracted from cartilages of Siberian sturgeon (Acipenser baerii) with yields of 27.13 ± 1.15 and 14.69 ± 0.85% on dry weight basis. ASC-SC and PSC-SC had glycine as the major amino acid with the contents of 326.8 and 327.5 residues 1000 residues^-1, and their contents of proline and hydroxyproline were 205.9 and 208.0 residues 1000 residues^-1. ASC-SC and PSC-SC comprised type I collagen ([α1(I)]₂α2(I)) and type II collagen ([α1(II)]₃) on the literatures and results of amino acid composition, SDS-PAGE pattern, UV, and FTIR spectra. Meanwhile, FTIR spectra data indicated that there were more hydrogen bonds in ASC-SC and more intermolecular crosslinks in PSC-SC. The maximum transition temperature (T_max) of the ASC (28.3 °C) and PSC (30.5 °C) was lower than those of collagens from mammalian cartilages (> 37 °C). ASC-SC and PSC-SC showed high solubility in the acidic pH ranges and the solubility decreased in the presence of NaCl at concentrations above 3%. Zeta potential studies indicated that both ASC-SC and PSC-SC exhibited a net zero charge at pH 6.30 and 6.32. SEM results indicated that ASC-SC and PSC-SC presented irregular dense sheet-like film linked by random-coiled filaments. Therefore, collagens from Siberian sturgeon cartilages might be the suitable alternatives of the collagens of mammal cartilages as functional ingredient to treat some diseases.

Physicochemical and Antioxidant Properties of Acid- and Pepsin-Soluble Collagens from the Scales of Miiuy Croaker (Miichthys Miiuy)

In this report, acid-soluble collagen (ASC-MC) and pepsin-soluble collagen (PSC-MC) were extracted from the scales of miiuy croaker (Miichthys miiuy) with yields of 0.64 ± 0.07% and 3.87 ± 0.15% of dry weight basis, respectively. ASC-MC and PSC-MC had glycine as the major amino acid with the contents of 341.8 ± 4.2 and 344.5 ± 3.2 residues/1000 residues, respectively. ASC-MC and PSC-MC had lower denaturation temperatures (32.2 °C and 29.0 °C for ASC-MC and PSC-MC, respectively) compared to mammalian collagen due to their low imino acid content (197.6 and 195.2 residues/1000 residues for ASC-MC and PSC-MC, respectively). ASC-MC and PSC-MC were mainly composed of type I collagen on the literatures and results of amino acid composition, SDS-PAGE pattern, ultraviolet (UV) and Fourier-transform infrared spectroscopy (FTIR) spectra. The maximum solubility of ASC-MC and PSC-MC was appeared at pH 1⁻3 and a sharp decrease in solubility was observed when the NaCl concentration was above 2%. Zeta potential studies indicated that ASC-MC and PSC-MC exhibited a net zero charge at pH 6.66 and 6.81, respectively. Furthermore, the scavenging capabilities on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, hydroxyl radical, superoxide anion radical and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical of ASC-MC and PSC-MC were positively correlated with their tested concentration ranged from 0 to 5 mg/mL and PSC-MC showed significantly higher activity than that of ASC-MC at most tested concentrations (p < 0.05). In addition, the scavenging capability of PSC-MC on hydroxyl radical and superoxide anion radical was higher than those of DPPH radical and ABTS radical, which suggested that ASC-SC and PSC-SC might be served as hydroxyl radical and superoxide anion radical scavenger in cosmeceutical products for protecting skins from photoaging and ultraviolet damage.

Preparation, Physicochemical and Antioxidant Properties of Acid- and Pepsin-Soluble Collagens from the Swim Bladders of Miiuy Croaker (Miichthys miiuy)

Collagen is one of the most useful biomaterials and widely applied in functional food and cosmetics. However, some consumers have paid close attention to the safety of mammalian collagens because of the outbreaks of bovine spongiform encephalopathy (BSE), foot-and-mouth disease (FMD), and other prion diseases. Therefore, there is a strong demand for developing alternative sources of collagen, with one promising source being from the process by-products of commercial fisheries. In this report, acid-soluble collagen (ASC-SB) and pepsin-soluble collagen (PSC-SB) from swim bladders of miiuy croaker (Miichthys miiuy) were isolated with yields of 1.33 ± 0.11% and 8.37 ± 0.24% of dry swim bladder weight. Glycine was the major amino acid present, with a content of 320.5 (ASC-SB) and 333.6 residues/1000 residues (PSC-SB). ASC-SB and PSC-SB had much lower denaturation temperatures compared to mammalian collagen, a consequence of low imino acid contents (196.7 and 199.5 residues/1000 residues for ASC-SB and PSC-SB, respectively). The data of amino acid composition, SDS-PAGE pattern, UV and FTIR spectra confirmed that ASC-SB and PSC-SB were mainly composed of type I collagen. FTIR spectra data indicated there were more hydrogen bonding and intermolecular crosslinks in ASC-SB. These collagens showed high solubility in the acidic pH ranges and low NaCl concentrations (less than 2%). The Zeta potential values of ASC-SB and PSC-SB were 6.74 and 6.85, respectively. ASC-SB and PSC-SB presented irregular, dense, sheet-like films linked by random-coiled filaments under scanning electron microscopy. In addition, ASC-SB and PSC-SB could scavenge DPPH radical, hydroxyl radical, superoxide anion radical, and ABTS radical in a dose-dependent manner. Overall, the results indicate that collagens from the swim bladders of miiuy croaker are a viable substitute for mammalian collagen, with potential functional food and cosmeceutical applications.

Bioactive Peptides from Cartilage Protein Hydrolysate of Spotless Smoothhound and Their Antioxidant Activity In Vitro

In the experiment, crude proteins from spotless smoothhound (Mustelus griseus), cartilages were isolated by HCl-Guanidine buffer, and its hydrolysate was prepared using trypsin at pH 8.0, 40 °C with a total enzyme dose of 2.5%. Subsequently, three antioxidant peptides were purified from the hydrolysate using membrane ultrafiltration, anion-exchange chromatography, gel filtration chromatography, and reverse phase high-performance liquid chromatography. The amino acid sequences of isolated peptides were identified as Gly-Ala-Glu-Arg-Pro (MCPE-A); Gly-Glu-Arg-Glu-Ala-Asn-Val-Met (MCPE-B); and Ala-Glu-Val-Gly (MCPE-C) with molecular weights of 528.57, 905.00, and 374.40 Da, respectively, using protein amino acid sequence analyzer and mass spectrum. MCPE-A, MCPE-B and MCPE-C exhibited good scavenging activities on 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH•) (EC₅₀ 3.73, 1.87, and 2.30 mg/mL, respectively), hydroxyl radicals (HO•) (EC₅₀ 0.25, 0.34, and 0.06 mg/mL, respectively), 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid radicals (ABTS⁺•) (EC₅₀ 0.10, 0.05, and 0.07 mg/mL, respectively) and superoxide anion radicals (O2−•) (EC₅₀ 0.09, 0.33, and 0.18 mg/mL, respectively). MCPE-B showed similar inhibiting ability on lipid peroxidation with butylated hydroxytoluene (BHT) in a linoleic acid model system. Furthermore, MCPE-A, MCPE-B, and MCPE-C could protect H₂O₂-induced HepG2 cells from oxidative stress by decreasing the content of malonaldehyde (MDA) and increasing the levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione reductase (GSH-Rx). Glu, Gly, Met, and Pro in their sequences and low molecular weight could be attributed to the antioxidant activities of three isolated peptides. These results suggested that GAERP (MCPE-A), GEREANVM (MCPE-B), and AEVG (MCPE-C) from cartilage protein hydrolysate of spotless smoothhound might serve as potential antioxidants and be used in the pharmaceutical and health food industries.

Cloning, Characterization, and Expression Profile of Estrogen Receptor in Common Chinese Cuttlefish, Sepiella japonica

Sex steroid hormones are widely detected in molluscs and play important roles in sex determination, gonadal tissue maturation, and gametogenesis. Nevertheless, the signaling pathways of sex steroids in cephalopod have not yet been clearly elucidated. In the present study, a full-length sequence encoding the estrogen receptor (ER) was isolated from common Chinese cuttlefish, Sepiella japonica. The sjER cDNA clone was found to contain 1,788 nucleotides including a 1,470 bp open reading frame encoding 489 amino acid (aa) residues. The deduced ER protein consisted of six nuclear receptor characteristic domains. Based on a phylogenetic analysis, the ER DNA-binding domain and ligand-binding domain are highly conserved compared to other mollusc ERs. Highest aa identities were found for sjER with common octopus (Octopus vulgaris) ER (89%) and pacific oyster (Crassostrea gigas) ER (61%). Tissue expression analysis confirmed that sjER was widely distributed among tissues and predominantly expressed in the brain, liver, gonad (testis and ovary), and other accessory sexual gland (nidamental gland). The ER expression was temporally upregulated in the brain, liver, and ovary during the early sexual maturation period in S. japonica, which is coincident with the fluctuation of ovary estradiol content. These suggest that sjER may be involved in regulating the reproductive cycle of S. japonica. A fusion protein transient transfections assay showed that sjER was mainly located in the nucleus, suggesting a possible orthodox working mechanism of S. japonica ER in the nucleus through a ligand-dependent activation of specific gene transcription.

Identification and Expression Profile of the Gonadotropin-Releasing Hormone Receptor in Common Chinese Cuttlefish, Sepiella japonica

Gonadotropin-releasing hormone (GnRH) plays a vital role in the regulation of reproduction through interaction with a specific receptor (the GnRH receptor). In this study, the GnRH receptor gene from the cuttlefish Sepiella japonica (SjGnRHR) was identified and characterized. The cloned full-length SjGnRHR cDNA was 1,468 bp long and contained a 1,029 bp open reading frame encoding 342 amino acid residues, 8 bp of 5' untranslated regions (UTR), and 431 bp of 3' UTR. The putative protein was predicted to have a molecular weight of 38.75 kDa and an isoelectric point of 9.47. In addition, this protein was identified as belonging to the rhodopsin-type (class A) G protein-coupled receptor family. The predicted amino acid sequence contained two N-linked glycosylation sites and 18 phosphorylation sites. Multiple sequence alignment, phylogenetic tree analysis, and three-dimensional structure modeling were conducted to clarify SjGnRHR bioinformatics characteristics. In vitro SjGnRHR expression was carried out using HEK293 cells and the pEGFP-N1 plasmid, to verify the transmembrane properties of this protein. The interaction between the S. japonica GnRH receptor and its ligand was clarified using internalization analysis. SjGnRHR transcriptional quantification confirmed the wide distribution of SjGnRHR in various S. japonica mature tissues. In addition, the transcriptional profile of SjGnRHR in the female brain and ovary during gonadal development was analyzed. Results indicate that GnRHR may be involved in diverse S. japonica physiological functions, especially in the control of reproduction.

Molecular cloning, expression analysis and cellular localization of an LFRFamide gene in the cuttlefish Sepiella japonica

Neuropeptides are important regulators of physiological processes in metazoans, such as feeding, reproduction, and heart activities. In this study, an LFRFamide gene was identified from the cuttlefish Sepiella japonica (designated as SjLFRFamide). The full-length sequence of SjLFRFamide cDNA has 841bp, and the open reading frame contains 567bp encoding 188 amino acids, which shared high similarity with precursor SOFaRP2 from Sepia officinalis. The deduced SjLFRFamdie precursor protein contains a signal peptide and four different FLPs (FMRFamide-like peptides): one pentapeptide (TIFRFamide), two hexapeptides (NSLFRFamide and GNLFRFamide) and one heptapeptide (PHTPFRFamide). Multiple sequence alignment showed that SjLFRFamide contains rather conserved mature peptides, which all ended in FRF. The phylogenetic analysis suggests that SjLFRFamide belongs to the LFRFamide subfamily. The tissue distribution analysis through quantitative real-time PCR method showed that SjLFRFamide mRNA is significantly expressed in the brain, and slight trace are detected in female nidamental gland and accessory nidamental gland. In situ hybridization assay of the brain indicated that SjLFRFamide is transcribed in several different functional lobes, suggesting SjLFRFamide might associate with multiple physiological regulations, such as feeding, chromatophore regulation and reproduction. This is the first study describing LFRFamide in S. japonica, which might have great importance for cuttlefish artificial breeding.

Identification and analysis of HSP70 from Sepiella maindroni under stress of Vibrio harveyi and Cd(2.)

The 70-kDa heat shock proteins (HSP70) play crucial roles in protecting cells against environmental stresses, such as heat shock, heavy metals and pathogenic bacteria. The full-length HSP70 cDNA of Sepiella maindroni (designated as SmHSP70, GenBank accession no. KJ739788) was 2109 bp, including an ORF of 1950 bp encoding a polypeptide of 649 amino acids with predicted pI/MW 5.24/71.30 kDa, a 62 bp-5'-UTR and a 97 bp-3'-UTR. BLASTp analysis and phylogenetic relationship strongly suggested that the amino acid sequence was a member of HSP70 family. Multiple sequence alignment revealed that SmHSP70 and other known HSP70 were highly conserved, especially in the regions of HSP70 family signatures, the bipartite nuclear targeting sequence, ATP/GTP-binding site motif and 'EEVD' motif. Time-dependent mRNA expression of SmHSP70 in the liver was recorded by quantitative real-time RT-PCR after Vibrio harveyi injection and Cd(2+) exposure. The results indicated that SmHSP70 played a significant role in mediating the environmental stress and immune response against pathogens.

Influence of Amino Acid Compositions and Peptide Profiles on Antioxidant Capacities of Two Protein Hydrolysates from Skipjack Tuna (Katsuwonus pelamis) Dark Muscle

Influence of amino acid compositions and peptide profiles on antioxidant capacities of two protein hydrolysates from skipjack tuna (Katsuwonus pelamis) dark muscle was investigated. Dark muscles from skipjack tuna were hydrolyzed using five separate proteases, including pepsin, trypsin, Neutrase, papain and Alcalase. Two hydrolysates, ATH and NTH, prepared using Alcalase and Neutrase, respectively, showed the strongest antioxidant capacities and were further fractionated using ultrafiltration and gel filtration chromatography. Two fractions, Fr.A3 and Fr.B2, isolated from ATH and NTH, respectively, showed strong radical scavenging activities toward 2,2-diphenyl-1-picrylhydrazyl radicals (EC₅₀ 1.08% ± 0.08% and 0.98% ± 0.07%), hydroxyl radicals (EC₅₀ 0.22% ± 0.03% and 0.48% ± 0.05%), and superoxide anion radicals (EC₅₀ 1.31% ± 0.11% and 1.56% ± 1.03%) and effectively inhibited lipid peroxidation. Eighteen peptides from Fr.A3 and 13 peptides from Fr.B2 were isolated by reversed-phase high performance liquid chromatography, and their amino acid sequences were determined. The elevated antioxidant activity of Fr.A3 might be due to its high content of hydrophobic and aromatic amino acid residues (181.1 and 469.9 residues/1000 residues, respectively), small molecular sizes (3–6 peptides), low molecular weights (524.78 kDa), and amino acid sequences (antioxidant score 6.11). This study confirmed that a smaller molecular size, the presence of hydrophobic and aromatic amino acid residues, and the amino acid sequences were the key factors that determined the antioxidant activities of the proteins, hydrolysates and peptides. The results also demonstrated that the derived hydrolysates and fractions from skipjack tuna (K. pelamis) dark muscles could prevent oxidative reactions and might be useful for food preservation and medicinal purposes.

Purification and characterization of three antioxidant peptides from protein hydrolyzate of croceine croaker (Pseudosciaena crocea) muscle

Three antioxidant peptides were purified from protein hydrolysate of croceine croaker (Pseudosciaena crocea) muscle prepared using pepsin and alcalase, and identified as Tyr-Leu-Met-Ser-Arg (PC-1), Val-Leu-Tyr-Glu-Glu (PC-2), and Met-Ile-Leu-Met-Arg (PC-3) with molecular weights of 651.77, 668.82, and 662.92Da, respectively. PC-1 exhibited the highest scavenging activities on DPPH (EC50 1.35mg/ml), superoxide (EC50 0.450mg/ml), and ABTS (EC50 0.312mg/ml) radicals, but PC-2 exhibited the strongest hydroxyl radical scavenging activity (EC50 0.353mg/ml) among the three peptides. PC-1 also showed effective inhibition on lipid peroxidation in the model system. The good activities of isolated peptides might be benefit from the smaller size and hydrophobic and/or aromatic amino acids within their sequences.

Antioxidant and functional properties of collagen hydrolysates from Spanish mackerel skin as influenced by average molecular weight

In the current study, the relationships between functional properties and average molecular weight (AMW) of collagen hydrolysates from Spanish mackerel (Scomberomorous niphonius) skin were researched. Seven hydrolysate fractions (5.04 ≤ AMW ≤ 47.82 kDa) from collagen of Spanish mackerel skin were obtained through the processes of acid extraction, proteolysis, and fractionation using gel filtration chromatography. The physicochemical properties of the collagen hydrolysate fractions were studied by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), gel filtration chromatography, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The results indicated that there was an inverse relationship between the antioxidant activities and the logarithm of the AMW of the hydrolysate fractions in the tested AMW range. However, the reduction of AMW significantly enhanced the solubility of the hydrolysate fractions, and a similar AMW decrease of the hydrolysate fractions negatively affected the emulsifying and foaming capacities. This presented as a positive correlation between the logarithm of AMW and emulsion stability index, emulsifying activity index, foam stability, and foam capacity. Therefore, these collagen hydrolysates with excellent antioxidant activities or good functionalities as emulsifiers could be obtained by controlling the effect of the digestion process on the AMW of the resultant hydrolysates.

Isolation and characterization of collagen and antioxidant collagen peptides from scales of croceine croaker (Pseudosciaena crocea)

Acid soluble collagen (ASC) from scales of croceine croaker (ASC-C) was successfully isolated with the yield of 0.37% ± 0.08% (dry weight basis), and characterized as type I collagen on the basis of amino acid analysis and electrophoretic pattern. The antioxidant hydrolysate of ASC-C (ACH) was prepared through a two-stage in vitro digestion (4-h trypsin followed by 4-h pepsin), and three antioxidant peptides (ACH-P1, ACH-P2, and ACH-P3) were further isolated from ACH using ultrafiltration, gel chromatography, and RP-HPLC, and their amino acid sequences were identified as GFRGTIGLVG (ACH-P1), GPAGPAG (ACH-P2), and GFPSG (ACH-P3). ACH-P1, ACH-P2, and ACH-P3 showed good scavenging activities on hydroxyl radical (IC₅₀ 0.293, 0.240, and 0.107 mg/mL, respectively), DPPH radical (IC₅₀ 1.271, 0.675, and 0.283 mg/mL, respectively), superoxide radical (IC₅₀ 0.463, 0.099, and 0.151 mg/mL, respectively), and ABTS radical (IC₅₀ 0.421, 0.309, and 0.210 mg/mL, respectively). ACH-P3 was also effectively against lipid peroxidation in the model system. The antioxidant activities of three collagen peptides were due to the presence of hydrophobic amino acid residues within the peptide sequences. The collagen peptides might be used as antioxidant for the therapy of diseases associated with oxidative stress, or reducing oxidative changes during storage.

Purification and characterisation of a novel antioxidant peptide derived from blue mussel (Mytilus edulis) protein hydrolysate

Protein derived from blue mussel (Mytilus edulis) was hydrolysed using four kinds of proteases (pepsin, papain, neutrase and alcalase), and the neutrase hydrolysate (BNH) obtained by 3-h hydrolysis exhibited the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity compared to other hydrolysates. By using ultrafiltration, gel filtration chromatography and reversed phase high performance liquid chromatography (RP-HPLC), a novel antioxidant peptide (BNH-P7) was isolated from BNH, and its amino acid sequence was identified as YPPAK (Tyr-Pro-Pro-Ala-Lys) with molecular weight of 574 Da. BNH-P7 exhibited good scavenging activity on DPPH radical, hydroxyl radical, and superoxide anion radical with EC(50) of 2.62, 0.228, and 0.072 mg/ml, respectively. BNH-P7 was also effectively against lipid peroxidation in a linoleic acid model system. The high activity of BNH-P7 was due to the small size and the presence of antioxidant and hydrophobic amino acid residues (Tyr and Pro) within its sequence.

Preparation and evaluation of antioxidant peptides from ethanol-soluble proteins hydrolysate of Sphyrna lewini muscle

To get high yield of ethanol-soluble proteins (EP) and the antioxidant peptides from Sphyrna lewini muscle, orthogonal experiments (L(9)(3)(4)) were applied to optimize the best extraction conditions and enzyme hydrolysis conditions. The yield of EP reached 5.903±0.053% under the optimum conditions of ethanol concentration 90%, solvent to material ratio 20:1, extraction temperature of 40°C and extraction time of 80min. The antioxidant SEPH (EP hydrolysate of S. lewini muscle) was prepared by using papain under the optimum conditions of enzymolysis time 2h, total enzyme dose 1.2%, enzymolysis temperature 50°C and pH 6, and its DPPH radical scavenging activity reached 21.76±0.42% at the concentration of 10mg/ml. Two peptides (F42-3 and F42-5) were isolated from SEPH by using ultrafiltration, anion-exchange chromatography, gel filtration chromatography and RP-HPLC. The structures of F42-3 and F42-5 were identified as Trp-Asp-Arg and Pro-Tyr-Phe-Asn-Lys with molecular weights of 475.50Da and 667.77Da, respectively. F42-3 and F42-5 exhibited good scavenging activity on hydroxyl radical (EC(50) 0.15mg/ml and 0.24mg/ml), ABTS radical (EC(50) 0.34mg/ml and 0.12mg/ml), and superoxide anion radical (EC(50) 0.09mg/ml and 0.11mg/ml), but moderate DPPH radical (EC(50) 3.63mg/ml and 4.11mg/ml). F42-3 and F42-5 were also effectively against lipid peroxidation in the model system and peroxyl free radical scavenging in β-carotene linoleic acid assay. Their high activities were due to the smaller size and the presence of antioxidative amino acids within the peptide sequences.

[Determination of 8 trace elements in mantle muscle and cuttlebone of Sepiella maindroni by ICP-MS using microwave digestion for sample preparation]

An inductively coupled plasma mass spectrometry (ICP-MS) for determination of the contents of 8 trace elements in mantle muscle and cuttlebone of Sepiella maindroni after microwave digestion of the sample has been developed. Satisfactory linearity of working curves for the 8 elements was obtained, giving all their correlation coefficients over 0.997 3. The precision of measurement ranges from 2.4% to 8.7% in terms of relative standard deviation. The recoveries and the limits of detection are in the range of 96.5%-106.3% and 0.002-0.032 microg x L(-1), respectively. It was indicated that the proposed method had the advantages of simplicity, speediness and sensitivity. The results showed that the mantle muscle and cuttlebone of Sepiella maindroni contained rich trace elements Zn and Cu, but the contents of Cd and As are higher than the limits of Chinese Pharmacopoeia, Green Trade Standard for Importing and Exporting Medicinal Plant and Preparation and U.S. Food and Drug Standard. Furthermore, our study provides new scientific foundation for the quality control, culture, general application, resource utilization and exporting of Sepiella maindroni.

Risk for occupational injury of handicapped workers in Taiwan

The current study investigated occupational risk of handicapped workers relative to nonhandicapped workers and used the standardized mortality ratio as an index that handicapped workers were at elevated risk for occupational injury. A total of 6,327 records of disabling occupational injuries beyond first aid treatment from January to December, 1999 were collected and analyzed. The ratio of the standardized mortality ratio of the handicapped vs nonhandicapped workers indicated that occupational injury risk of handicapped workers must be seriously examined for the reasons for this unexpectedly high occupational risk.

A comparison of seven visual fatigue assessment techniques in three data-acquisition VDT tasks

We compared 7 methods of measuring visual fatigue--accommodation power, visual acuity, pupil diameter, critical fusion frequency (CFF), eye movement velocity, subjective rating of visual fatigue, and task performance--for their sensitivity to visual load. In the experiment, 10 participants performed a monitoring task at 2 viewing distances, read articles under 2 levels of screen contrast, and tracked visual targets at 2 different speeds. The same measurement techniques, excluding pupil diameter and eye movement velocity, were compared by extending the task time from 20 to 60 min with the same VDT tasks to test for possible improvement in sensitivity. The results indicated that sensitivities of accommodation power, visual acuity, and CFF were greatly improved by a longer task period, but these 3 measurement techniques did not distinguish among tasks. Pupil diameter, eye movement velocity, and subjective rating of visual fatigue were sensitive in differentiating tracking from reading and monitoring tasks. Eye movement velocity and subjective rating were sensitive to the changes in target velocity of the tracking task. Although task performance was not directly comparable to other measurement techniques, it helped to ensure that participants maintained the same performance level by devoting more resources to the high-load conditions. Actual or potential applications of this research include using some of these assessment techniques for the design of adaptive displays.

Ratings of 830 jobs on 45 characteristics: factor and cluster analyses into age-enhanced, age-neutral and age-counteracted, and age-impaired categories

The current study measured the critical elements of jobs and characterized the jobs' suitability for aging workers based on ratings of those elements. The sample consisted of 830 job titles collected by the Employment and Vocational Training Administration in Taiwan. For each job the ratings of 45 specific variables, falling into three major classes, were factor analyzed, using principal components analysis with varimax rotation. A nine-factor solution explained 50.1% of the variance. Using a nonhierarchical clustering procedure, 830 jobs were classified into three homogeneous clusters which were significantly different on nine factors except for Manual Dexterity. Mapping the ratings on the 9 factors and the characteristics of aging workers, the four job clusters were defined as Age-enhanced, Age-neutral, and Age-counteracted, and Age-impaired to describe the suitability for aging workers.

Aiming accuracy of the line of gaze and redesign of the gaze-pointing system

The current experiment tested the aiming accuracy of the eye for targets at nine different positions and of two different sizes. The left eye was tracked to record the line of gaze with an infrared eye-monitoring device. For each subject, horizontal shift, vertical shift, standard deviations of the X and Y coordinates, and 95th percentile of the horizontal and vertical shifts from the nine target centers were calculated to indicate the precision, accuracy, and possible design limits of the gaze points. Analysis showed that the target's position had a strong effect on the vertical shift, standard deviations of the Y coordinate, and 95th percentile of the vertical shift. The effect of target size was not significant on any of the dependent measures. The research findings have important implications for the redesign of the gaze-pointing device. Visual targets appearing below the horizontal line of sight should be larger than those above. Based on the 95th percentile of the horizontal and vertical shifts, targets should be approximately 2.0 degrees wide and 2.4 degrees long above or coinciding with the horizontal line of gaze and 2.6 degrees wide and 3.9 degrees (cm) long below the horizontal line of gaze.

Differential threshold of length and response criterion for inspecting irregular objects

This research investigated human visual sensitivity and bias in inspecting irregular objects. A preliminary study was conducted using the method of constants to determine the threshold value for judgment of size. A factorial experiment was conducted using payoffs, rate of defective items, and detectability in the signal-detection theory as the factors. In total, eight experimental conditions were tested. 10 college students were recruited as subjects. Each subject was asked to compare 40 teapot shapes to a standard teapot shape under eight experimental conditions. Defective shapes were generated by lengthening the vertical dimension of a standard teapot shape by a factor of 1.01 and 1.04 for 'low' and 'high' detectability. The decision time and responses of 'identical' or 'different' were collected under all experimental conditions. Analysis indicates that the decision-making strategy used to inspect this irregular object was very close to maximizing the accuracy of decision-making by considering the rate of defective items. This result is different from most research findings in signal-detection theory in which responses of human beings are similar to degraded Bayes optimizers. The standard deviation of the signal distribution was about 1.30 and 1.41 times that of the noise distributions for 'low' and 'high' detectability.

Speed and accuracy of eye-gaze pointing

The current experiment examined the speed-accuracy trade-off of saccadic movement between two targets. Ten subjects looked alternately at two targets as fast and as accurately as possible for 2 min. under different conditions of target size, distance between targets, and direction of eye movement. Saccadic movement of the left eye was tracked and recorded with an infrared eye monitoring device to compute the starting position, ending position, and duration of each saccadic movement. Eye-movement time was significantly related to target size and distance between targets, but the speed-accuracy trade-off was significantly different from that predicted by Fitts' Law. Reaction time was not significantly changed by the direction of eye movement.

Task analysis for computer-aided design (CAD) at a keystroke level

The purpose of this research was to develop a new model to describe and predict a computerized task. AutoCAD was utilized as the experimental tool to collect operating procedure and time data at a keystroke level for a computer aided design (CAD) task. Six undergraduate students participated in the experiment. They were required to complete one simple and one complex engineering drawing. A model which characterized the task performance by software commands and predicted task execution time using keystroke-level model operators was proposed and applied to the analysis of the dialogue data. This task parameter model adopted software commands, e.g. LINE, OFFSET in AutoCAD, to describe the function of a task unit and used up to five parameters to indicate the number of keystrokes, chosen function for a command and ways of starting and ending a command. Each task unit in the task parameter model can be replaced by a number of primitive operators as in the keystroke level model to predict the task execution time. The observed task execution times of all task units were found to be highly correlated with the task execution times predicted by the keystroke level model. Therefore, the task parameter model was proved to be a usable analytical tool for evaluating the human-computer interface (HCI).