Application of OXITEST for Prediction of Shelf-Lives of Selected Cold-Pressed Oils.

Introduction: Due to the enhanced awareness of consumers concerning healthy foods, homemade expeller-pressed oils have become popular worldwide. However, an extended storage period may lead to oxidization of the oil and exposure to hazardous byproducts by consumers. Methods: In this study, 10 pressed oil samples prepared from common oilseeds using a small-scale expeller oil press were analyzed by OXITEST with a sample amount of 5 g of oil and an oxygen pressure of 800 kPa under accelerated conditions for shelf-life projections. The oil properties were investigated, including the recovery, smoke point, acid value, iodine value, "fatty acid composition, and contents of pigments and tocopherols". Results: The autoxidation reaction of various expeller-pressed oils under an accelerated testing system followed zero-order Arrhenius kinetics (R 2 > 0.99). Shelf-lives of the pressed oils at 25°C were estimated by extrapolation to range 105~1,089 days. The obtained shelf-lives were significantly correlated with log induction period (IP) values (r > 0.81, p < 0.05) and unsaturated fatty acids (UFAs) (r < -0.69, p < 0.05), but not with the iodine value, acid value, or smoke point. Scatter diagrams between shelf-lives and UFAs suggested that these pressed oils could be grouped by two linear regression curves (r > 0.98, p < 0.05). The predictive equations using multiple linear regression are presented herein, with predictor variables of UFAs and an unspecified item involving potential influencing factors such as tocopherol contents (r > 0.88, p < 0.05). Conclusions: Our findings first revealed that the UFA portion was partially correlated with the shelf-lives of selected expeller-pressed seed oils as estimated by the OXITEST. The derived equations can be applied for shelf-life predictions of expeller-pressed oils stored under dark ambient conditions based on the fatty acid profile.

Lrp, a global regulator, regulates the virulence of Vibrio vulnificus.

BACKGROUND: An attenuated mutant (designated NY303) of Vibrio vulnificus, which causes serious wound infection and septicemia in humans, was isolated fortuitously from a clinical strain YJ016. This mutant was defective in cytotoxicity, migration on soft agar and virulence in the mouse. The purpose of this study was to map the mutation in this attenuated mutant and further explore how the gene thus identified is involved in virulence. METHODS: The whole genome sequence of mutant NY303 determined by next-generation sequencing was compared with that of strain YJ016 to map the mutations. By isolating and characterizing the specific gene-knockout mutants, the gene associated with the phenotype of mutant NY303 was identified. This gene encodes a global regulator, Lrp. A mutant, YH01, deficient in Lrp was isolated and examined in vitro, in vivo and ex vivo to find the affected virulence mechanisms. The target genes of Lrp were further identified by comparing the transcriptomes, which were determined by RNA-seq, of strain YJ016 and mutant YH01. The promoters bound by Lrp were identified by genome footprinting-sequencing, and those related with virulence were further examined by electrophoretic mobility shift assay. RESULTS: A mutation in lrp was shown to be associated with the reduced cytotoxicity, chemotaxis and virulence of mutant NY303. Mutant YH01 exhibited a phenotype resembling that of mutant NY303, and was defective in colonization in the mouse and growth in mouse serum, but not the antiphagocytosis ability. 596 and 95 genes were down- and up-regulated, respectively, in mutant YH01. Many of the genes involved in secretion of the MARTX cytotoxin, chemotaxis and iron-acquisition were down-regulated in mutant YH01. The lrp gene, which was shown to be negatively autoregulated, and 7 down-regulated virulence-associated genes were bound by Lrp in their promoters. A 14-bp consensus sequence, mkCrTTkwAyTsTG, putatively recognized by Lrp was identified in the promoters of these genes. CONCLUSIONS: Lrp is a global regulator involved in regulation of cytotoxicity, chemotaxis and iron-acquisition in V. vulnificus. Down-regulation of many of the genes associated with these properties may be responsible, at least partly, for loss of virulence in mutant NY303.

Re-examination of chromogenic quantitative assays for determining flavonoid content.

Flavonoids in plants have gained worldwide attention because of their benefits for human health. This study compared three analytical procedures commonly used for determining flavonoid content in plant samples in terms of chromogenic relationships and the reaction products of different flavonoid structures by means of using flavonoid standards with flavone, flavonol, flavanone, flavanol, and isoflavone and analytes such as phenolic acids commonly found in plant extracts. Procedure A produced a stable color reaction between 3-hydroxy-4-keto-flavonoids (flavonols) and 5-hydroxyflavones and was highly sensitive. Procedure B produced color reactions among most of the flavonoids, but the reaction products had different colors and faded over time. Procedure B also produced a color reaction with caffeic and chlorogenic acid. Procedure C was the most sensitive. It produced a color reaction and, like procedure A, could be used to quantify flavonols and 5-hydroxyflavones, but also showed color reaction toward caffeic and chlorogenic acid. On the basis of the results, the current three procedures are not satisfactory for determining all of the types of flavonoid. Two issues needed to be clarified before a promising determination of flavonoid content could be performed with chromogenic assays. The first is a survey of the literature to screen the possible predominant component of flavonoid in analytes. The other is guided by the predominant flavonoid; a promising calibration curve for flavonoid detection can be established on the basis of the selection of an appropriate method and a chemical standard with an equivalent dose response to the predominant flavonoid.

Crystal structure of Get4-Get5 complex and its interactions with Sgt2, Get3, and Ydj1.

Get3, Get4, and Get5 in Saccharomyces cerevisiae participate in the insertion of tail-anchored proteins into the endoplasmic reticulum membrane. We elucidated the interaction between Get4 and Get5 and investigated their interaction with Get3 and a tetratricopeptide repeat-containing protein, Sgt2. Based on co-immunoprecipitation and crystallographic studies, Get4 and Get5 formed a tight complex, suggesting that they constitute subunits of a larger complex. In contrast, although Get3 interacted physically with the Get4-Get5 complex, low amounts of Get3 co-precipitated with Get5, implying a transient interaction between Get3 and Get4-Get5. Sgt2 also interacted with Get5, although the amount of Sgt2 that co-precipitated with Get5 varied. Moreover, GET3, GET4, and GET5 interacted genetically with molecular chaperone YDJ1, suggesting that chaperones might also be involved in the insertion of tail-anchored proteins.