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Salmonoid cathelicidin (termed CATH_BRALE) is a fish-derived antimicrobial peptide (AMP) isolated from Brachymystax lenok. In this study, CATH_BRALE was expressed in Chlamydomonas reinhardtii as a format of three repeats (3×CATH_BRALE) attached with hemagglutinin (HA) and 6×His at its C-terminus, producing a recombinant peptide with a molecular weight of ∼18 kDa. The recombinant 3×CATH_BRALE-HA-6×His remains to be expressed stably in Chlamydomonas cells even after passaging continuously for five months and yields up to 0.21% of the total Chlamydomonas soluble proteins. 3×CATH_BRALE-HA-6×His showed broad-spectrum antibacterial activity against bacteria, with MIC values ranging from 40 to 50 µg/ml for Gram-negative bacteria and 30–40 µg/ml for Gram-positive bacteria. This recombinant peptide had strong thermostability and pH stability, and its antibacterial activity was rarely altered when temperature and pH are changed. It resisted to the digestion of several tested proteases to certain extents. Besides, 3×CATH_BRALE-HA-6×His is biologically safe as it did not hemolyze rat erythrocytes nor caused cytotoxicity on Vero, BHK21, HEK293, and MDBK cells. Its antibacterial action was achieved by penetrating the cell membrane to disrupt the membrane of the target bacterial cell. In sum, our data showed that C. reinhardtii can be used as a heterologous expression host to produce biologically active CATH_BRALE. [Display omitted] • A multimer termed 3 ×CATH_BRALE was stably expressed in Chlamydomonas reinhardtii. • C. reinhardtii-derived 3 ×CATH_BRALE showed a wide spectrum of antibacterial activity. • C. reinhardtii-derived 3 ×CATH_BRALE was tolerant of temperature, pH, and proteinases. • C. reinhardtii-derived 3 ×CATH_BRALE was not toxic to mammalian and human cells. • C. reinhardtii-derived 3 ×CATH_BRALE permeabilizes the bacterial cell membrane. [ABSTRACT FROM AUTHOR]

The nozzle-head intersection of a nuclear steam generator (SG) has gained great attention due to its special location and prone to cracks. For the purpose of estimating and ensuring the integrity of the SG structure, the fracture evaluation of nozzle-head intersection after a period of operation needs to be analyzed under a variety of loading conditions. In this paper, stress intensity factors (SIFs) of external surface cracks postulated at the nozzle-head intersection of a SG subjected to pressure, bending, and thermal loadings are evaluated using finite element method. Comparing to the SIFs of cracked pipe described in the RSE-M code, it is found that SIF calculation method of cracked pipe can be conservatively applied to the external surface cracks at the nozzle-head intersection of the SG. Using the conservative SIF solution, the fatigue crack growth and fracture assessment of the postulated cracks are evaluated according to the RSE-M code considering the material aging. Finally, the critical crack size and allowable initial crack size for the life of 40 years are given for the nozzle-head intersection of the SG. • The SIF solution of pipe in RSE-M can be conservatively used to the external surface cracks at the nozzle-head intersection. • The initial size of a *2 c = 10*30 mm will be unsafefor 40 years life with RT NDT = 50 °C using the conservative method. • The conservative critical crack size and allowable initial crack size are given for the life of 40 years with various RT NDT. [ABSTRACT FROM AUTHOR]