Characterization and antioxidant activities of marine pepsin soluble collagen from the skin of yellow goosefish Lophius litulon

Characteristics and antioxidant activities of pepsin-soluble collagen （PSC） from yellow goosefish （Lophius litulon） skins were investigated. PSC was characterized as a type I collagen, and its imino acid content was 193 residues/1 000 residues. PSC＇s denaturation temperature was -17.56℃ and Fourier transform infrared spectra confirmed the presence of triple helices. Solubility analysis showed good solubility at acidic pH （1-6） or low NaCl concentrations （≤2%）. PSC showed scavenging activity against hydroxyl radicals and superoxide anions in a concentration-dependent manner. Furthermore, PSC could protect D-galactose-induced skin aging by significantly controlling malondialdehyde formation and improving the activity of superoxide dismutase, glutathione peroxidase, catalase, glutathione, and hydroxyproline. PSC may be a promising antioxidant in appropriate applications.

Investigation of the solubility and dispersion degree of calf skin collagen in ionic liquids

The dissolution of collagen in ionic liquids(ILs)was highly dependent on the polarity of ILs,which was influenced by their sorts and concentrations.Herein,the solubility and dispersion degree of collagen in two sorts of ILs,namely 1-ethyl-methylimidazolium tetrafluoroborate([EMIM][BF4])with low polarity and 1-ethyl-3-methylimidazolium acetate([EMIM][Ac])with high polarity in a concentration range from 10% to 70% at 10℃ were investigated.When 150 mg of collagen was added to 30 mg of ILs,the minimum soluble collagen concentration was 0.02 mg/mL in 70%[EMIM][BF4]with lowest polarity and the maximum was 3.57 mg/mL in 70%[EMIM][Ac]with highest polarity,which indicates that soluble collagen and insoluble collagen fibers were both present.For insoluble collagens,differential scanning calorimetry showed that the thermal-stability was weakened when increasing the ILs concentration and polarity,and the fiber arrangement was looser with a more uniform lyophilized structure,observed by atomic force microscopy and scanning electron microscopy.For soluble collagens,electrophoresis patterns and Fourier transform infrared spectroscopy showed that no polypeptide chain degradation occurred during dissolution,but the thermal denaturation temperature decreased by 0.26℃~7.63℃ with the increase of ILs concentrations,measured by ultra-sensitive differential scanning calorimetry.Moreover,the aggregation of collagen molecules was reduced when ILs polarity was increased as determined by fluorescence measurements and dynamic light scattering,which resulted in an increased loose fiber arrangement observed by atomic force microscopy.If the structural integrity of collagen needs to be retained,then the ILs sorts and concentrations should be considered.

Characterization of acid-and pepsin-soluble collagens from spines and skulls of skipjack tuna(Katsuwonus pelamis)

Acid-soluble collagen(ASC) and pepsin-soluble collagen(PSC) from the spine(ASC-SP and PSC-SP) and skull(ASC-SK and PSC-SK) of the skipjack tuna, Katsuwonus pelamis, were successfully isolated and characterized. The yields of ASC-SP, PSC-SP, ASC-SK and PSC-SK were(2.47 ± 0.39)%,(5.62 ± 0.82)%,(3.57 ± 0.40)%, and(6.71 ± 0.81)%, respectively, on the basis of dry weight. The four collagens contained Gly(330.2-339.1 residues/1 000 residues) as the major amino acid, and their imino acid contents were between 168.8 and 178.2 residues/1 000 residues. Amino acid composition, SDS-PAGE, and FTIR investigations confirmed that ASC-SP and ASC-SK were mainly composed of type I collagen, and had higher contents of high-molecular weight cross-links than those of PSC-SK and PSC-SP. The FTIR investigation also certified all the collagens had triple helical structure. The denaturation temperatures of ASC-SK, PSC-SK, ASC-SP, and PSC-SP were 17.8, 16.6, 17.6, and 16.5 °C, respectively. All isolated collagens were soluble at acidic pH(1-5) and lost their solubilities when the NaCl concentration was above 2%(W/V). The isolated collagens from the spines and skulls of skipjack tuna could serve as an alternative source of collagens for further application in food, cosmetic, biomedical, and pharmaceutical industries.

Extraction of soluble collagen and its feasibility in the palaeodietary research

In current palaeodietary research, gelatinization is the main method to extract insoluble collagen （ISC） from ancient bones. However, the degradation products of ISC, i.e., soluble collagen （SC）, is often neglected and abandoned. In this work, we try to separate the extracts of ancient bones using gel chromatography and compare the contents of carbon and nitrogen, atomic C/N ratio, and stable carbon and nitrogen isotopic values of the extracts from three peaks to determine which peak can be at- tributed to SC. At last, the potential application of SC in palaeodietary research is discussed based on the comparison of stable isotopic values between ISC and SC. Among the three peaks, the second with the retention time between 17.5 min and 27.5 min had the most broad peak shape, indicating that the molecular weights of proteins collected were most variable. Besides, the contents of carbon and nitrogen and atomic C/N ratio of extracts in this peak were closest to the corresponding ISC. Based on the above, we conclude that the extract in second peak is SC. More important, the δ13c and δ15N values of ISC and SC are very similar. For ISC and SC with atomic C/N ratios within the normal range （2.9-3.6）, the mean difference of δ13C value was only （0.3±0.2）%o （n=2） while δ15N value was （0.6±0.1）‰ （n=2）. Although the atomic C/N ratios of some SC are slightly be- yond the normal range, the mean differences of δ13C and δ15N values were still only （0.4±0.1）‰and （0.3±0）‰ （n=2） respec- tively. These isotopic differences are quite below the isotope fractionation in one trophic level δ13C values of 1‰-1.5‰ and 615N values of 3‰-5‰）, suggesting that SC had great application potentials in palaeodietary research.