Effects of pH and salt concentration on freeze-thaw fractionation of soymilk protein.

BACKGROUND: The two major storage proteins of soymilk are the globulins 7S and 11S. Freeze-thaw fractionation is a simple method for separating these proteins in raw soymilk. In this study, we assessed the freeze-thaw fractionation ability of raw soymilk under various pH (4.3-11.6) conditions and added salt (sodium chloride) concentrations (0.00-0.67 mol L-1). RESULTS: We successfully achieved fractionation within a pH range of 5.8-6.7 and when the salt concentration was 0.22 mol L-1 or lower. Analysis of particle size distribution and microscopic examination of soymilk revealed no direct correlation between particle size and freeze-thaw fractionation ability. Interestingly, it was confirmed that the ranges of zeta potential values associated with successful freeze-thaw fractionation in raw soymilk remained consistent across different pH and salt concentration conditions. These ranges were between -23 and -28 mV at pH levels ranging from 5.8 to 6.7 and between -18 and -29 mV at added salt concentrations ranging from 0 to 0.22 mol L-1. CONCLUSION: The pH and salt concentration in raw soymilk markedly influence the freeze-thaw fractionation process. We confirmed that the range of zeta potential values where fractionation was possible remained consistent under various pH and salt concentration conditions. These findings suggest that the zeta potential value might serve as an indicator for evaluating the freeze-thaw fractionation ability of raw soymilk. © 2024 Society of Chemical Industry.

Synthesis of [1]Benzothieno[3,2- b][1]benzothiophene Derivatives via Successive Iodocyclization/Photocyclization of Alkynes.

A new synthetic method for [1]benzothieno[3,2- b][1]benzothiophene derivatives (BTBTs) was developed. The present method consists of iodocyclization of 1,2-bis(2-methylthiophenyl)ethynes and photolysis of 3-iodo-(2-methylthiophenyl)benzo[ b]thiophenes. With 1,2-bis(2-methylthiophenyl)ethynes treated with I2/PhI(OAc)2 in CH2Cl2 at room temperature, selective cyclization at sulfur took place to give 3-iodo-(2-methylthiophenyl)benzo[ b]thiophenes in good yields. Irradiation of the iodinated benzo[ b]thiophenes with a high-pressure Hg lamp (>290 nm) provided BTBTs in good yields. Furthermore, the present method was applied to the synthesis of bis[1]benzothieno[2,3- d;2',3'- d']benzo[1,2- b;4,5- b']dithiophene (BBTBDT).

Angiotensin II increases sperm phagocytosis by neutrophils in vitro: A possible physiological role in the bovine oviduct.

This study aimed to investigate the possible effects of the vasoactive peptide angiotensin II (ANG II), secreted by bovine oviduct epithelial cells, on the in vitro phagocytic activity of polymorphonuclear leukocytes, specifically neutrophils, towards sperm. The measured concentrations of ANG II in oviduct flushes and conditioned medium from primary bovine oviduct epithelial culture ranged from 10(-10) to 10(-11) M. In our experiments, neutrophils were incubated for 2 hr with ANG II (0, 10(-11) , 10(-10) , 10(-9) , and 10(-8) M). Phagocytosis and superoxide production were then assessed by co-incubation of these neutrophils with sperm pretreated to induce capacitation, revealing a dose-dependent increase in both metrics by ANG II. This stimulatory effect of ANG II was eliminated by losartan, an angiotensin receptor type 1 (AGTR1) antagonist. ANG II also suppressed neutrophil transcription of angiotensin converting enzyme-1 (ACE) and AGTR1, but not AGTR2, suggesting the involvement of the AGTR1 receptor-mediated pathway in the response to sperm. Scanning electron microscopy further revealed that incubation of neutrophils with ANG II stimulated the formation of DNA-based extracellular traps for sperm entanglement. The addition of prostaglandin E2 at concentrations found in the oviduct suppressed the ANG II-stimulated phagocytic activity of neutrophils towards sperm. Thus the physiological levels of ANG II stimulate neutrophil phagocytosis of sperm in vitro, and suggest that an angiotensin/prostaglandin E2 system may fine-tune the local immune response that fosters sperm survival in the bovine oviduct. Mol. Reprod. Dev. 83: 630-639, 2016. © 2016 Wiley Periodicals, Inc.

Endothelin-1 downregulates sperm phagocytosis by neutrophils in vitro: A physiological implication in bovine oviduct immunity.

The oviduct is an active contractile tube that provides the proper environment for sperm transport, capacitation and survival. Oviductal contractions are regulated by autocrine/paracrine secretion of several factors, such as prostaglandins (PGs) and endothelin-1 (EDN-1). We have previously shown that during the preovulatory stage, sperm are exposed to polymorphonuclear neutrophils (PMNs) in the bovine oviduct, and the bovine oviduct epithelial cells (BOECs) secrete molecules including PGE2 that suppress sperm phagocytosis by PMNs in vitro. In this study, we investigated the possible effects of EDN-1 on the phagocytic activity of PMNs toward sperm. The local concentrations of EDN-1 in oviduct fluid and BOEC culture medium ranged from 10(-10) to 10(-11) M as determined by EIA. Phagocytosis and superoxide production were assayed by co-incubation of sperm pretreated to induce capacitation with PMNs exposed to EDN-1 (0, 10(-11), 10(-10), 10(-9), and 10(-8) M) for 2 h. EDN-1 suppressed dose dependently (10(-11) to 10(-8) M) the phagocytic activity for sperm and superoxide production of PMNs in response to capacitated sperm. Moreover, this suppression was eliminated by an ETB receptor antagonist (BQ-788). EDN-1 suppressed mRNA expression of EDN-1 and ETB but not ETA receptors in PMNs, suggesting the ETB receptor-mediated pathway. Scanning electron microscopic observation revealed that incubation of PMNs with EDN-1 (10(-9) M) completely suppressed the formation of DNA-based neutrophil extracellular traps for sperm entanglement. The results provide evidence indicating that EDN-1 may be involved in the protection of sperm from phagocytosis by PMNs in the bovine oviduct, supporting sperm survival until fertilization.

Proposal of mechanism of the freeze-thaw fractionation of 7S and 11S globulins in soymilk.

The mechanism underlying the freeze-thaw fractionation of 7S and 11S globulins in soymilk was investigated. Freeze-thawed soymilk demonstrated an increased particle size compared with raw soymilk. Further, when defatted raw soymilk was freeze-thawed, it was fractionated into 7S (supernatant) and 11S (precipitate) globulins, similar to what is found with freeze-thaw of raw soymilk. When raw soymilk samples with different ratios of 11S/7S were freeze-thawed, the 11S-deficient variety showed no precipitate. The addition of sodium sulphite or sodium dodecyl sulphate also inhibited precipitate formation after freeze-thawing, resulting in no fractionation. These results suggest that the fractionation is due to selective precipitation of aggregates of 11S globulins and/or 11S globulins and lipid complexes, in which the protein molecules interact through disulphide bonds and/or hydrophobic interactions.

Multiple SecA molecules drive protein translocation across a single translocon with SecG inversion.

SecA is a translocation ATPase that drives protein translocation. D209N SecA, a dominant-negative mutant, binds ATP but is unable to hydrolyze it. This mutant was inactive to proOmpA translocation. However, it generated a translocation intermediate of 18 kDa. Further addition of wild-type SecA caused its translocation into either mature OmpA or another intermediate of 28 kDa that can be translocated into mature by a proton motive force. The addition of excess D209N SecA during translocation caused a topology inversion of SecG. Moreover, an intermediate of SecG inversion was identified when wild-type and D209N SecA were used in the same amounts. These results indicate that multiple SecA molecules drive translocation across a single translocon with SecG inversion. Here, we propose a revised model of proOmpA translocation in which a single catalytic cycle of SecA causes translocation of 10-13 kDa with ATP binding and hydrolysis, and SecG inversion is required when the next SecA cycle begins with additional ATP hydrolysis.

Elastic layer-structured metal organic frameworks (ELMs).

Elastic layer-structured metal organic frameworks (ELMs) having flexible two-dimensional structure show a gate phenomenon in sorption/desorption of simple gas molecules. The gate phenomenon is accompanied by expansion/shrinkage of the layers. The gas sorption/desorption is not based on a physical adsorption, but on a chemical reaction, which includes high cooperativity. The cooperative reaction could be analyzed thermodynamically. The gate phenomenon showed advantages in separation of CO2 from mixed gases and in storage of CH4 owing to easy release of absorbed molecules.