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Host defense peptides (HDPs), a class of conserved components of animal innate immune system, possess direct antimicrobial activities against invading pathogens and broadly participate in boosting and modulating host immune responses. Cathelicidins is an important family of HDPs that has been identified exclusively in vertebrates. Considering the relatively conserved innate immune system between invertebrates and vertebrates, it is speculated that HDPs from vertebrates may also possess modulating functions on invertebrate innate immune system. In the present study, two novel cathelicidins (As-CATH4 and 5), which had been identified from the Chinese alligator in our previous study, were employed to investigate their functions as novel peptide immunostimulants in Chinese mitten crab. As-CATH4 and 5 exhibited potent, broad-spectrum, and rapid antimicrobial activities against all the tested aquatic pathogenic bacteria. Unlike traditional antibiotics, they target on bacterial cell membrane, induce membrane permeabilization and cell disruption, and ultimately result in cell death. The antimicrobial effect is far more rapid than traditional antibiotics. Therefore they are unlikely to induce bacteria resistance. After the crabs were administered with As-CATH4 and 5, the activities of lysozyme, acid phosphatase and alkaline phosphatase were significantly enhanced, which indicated that the immune system of crabs could be activated by As-CATH4 and 5. In bacteria challenge test, As-CATH4 and 5 could significantly decrease the bacterial numbers in crabs, and increase the survival rates of crabs in both pre-stimulation and co-stimulation groups. All of the results above indicated the great potential of As-CATH4 and 5 as novel peptide immunostimulants in the crab aquaculture. [ABSTRACT FROM AUTHOR]

Highland barley is one of the hull-less barleys that contains high amounts of β-glucan. A detailed sequence analysis is needed to support the application of the β-glucan from highland barley. The β-conformation and 1 → 3/1 → 4 linkages were confirmed using nuclear magnetic resonance (NMR) spectroscopy. Monosaccharide analysis was accomplished with high-performance anion exchange chromatography (HPAEC) coupled to pulsed amperometric detection (PAD) and showed that glucose (G) was the dominant sugar component of this β-glucan. HPAEC-PAD was applied with on-line electrospray ion - to quadrupole time – of – flight mass spectrometry (Q/TOF-MS) to sequence oligosaccharides enzymatically derived from this β-glucan. More than 20 oligosaccharides were observed in the partially digested β-glucan mixture and their degree of polymerization (dp), confirmed by MS analysis, ranged from dp 2 to dp 20. The sequences of oligosaccharide dp2 – dp7 in the digested product mixture were unambiguously determined with MS/MS. Based on the sequence analysis of these oligosaccharides, G1→3G1→4G and G1→3G1→4G1→4G were determined to be the major repeating blocks of this β-glucan, and they were interspersed with homogeneous 1 → 4 linked domains with different lengths. The ratio of 1 → 3 and 1 → 4 linkages in the β-glucan was approximately 1:3. [ABSTRACT FROM AUTHOR]