A transmission electron microscope (TEM) study was made of the interphase boundary structure of delta plates precipitated from the gamma phase in alloy 718. A variety of interfacial defects were examined and identified. These results, together with available data obtained from bcc laths in fcc Ni-Cr alloys, were used to develop a method for predicting precipitate orientation relationships and boundary orientations. The method employs a geometric matching approach in three dimensions based upon the concept of near-coincidence sites. It is suggested that precipitates in a given system select an orientation relationship which produces the greatest areal density of near-coincidence sites and that the habit plane adopts an orientation that yields the greatest area of boundary containing contiguous near-coincidence sites.

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Few data are available about the effects of complexation of polyphenols with polysaccharide on their bioavailability. The complex of tea polyphenols (TP) with oat β-glucan was characterized by ultraviolet-visible spectrometry, Fourier transform infrared spectrometry, differential scanning calorimetry, atomic force microscopy, and solid-state (13)C NMR spectroscopy. The results indicated that the bonds which governed the interaction between TP and oat β-glucan were strong hydrogen bonds. The in vitro antioxidant activity of TP, β-glucan, their complex, and physical mixture was assessed using four systems, namely, DPPH(•), OH(•), and O(2)(•-) scavenging activities and reducing power. The complexation and blending of TP and β-glucan exhibited different impacts on the index of in vitro and in vivo antioxidant capacities. In the concentration range of 0.5-2.5 mg mL(-1), the complex had highest O(2)(•-) scavenging activity, whereas the highest OH(•) scavenging activity was found with the physical mixture. For antioxidant testing in vivo, there was no significant difference between the complex and the physical mixture in terms of glutathione peroxidase activity and levels of malondialdehyde and total antioxidant capacity in serums. However, the complex exhibited much higher activities of superoxide dismutase and glutathione peroxidase in livers than the physical mixture. The present study provided a deeper understanding of the influence of molecular interaction between TP and oat β-glucan on their antioxidant activities.

BackgroundIn the yeast Saccharomyces cerevisiae, as in every eukaryotic organism, the mRNA 5′-untranslated region (UTR) is important for translation initiation. However, the patterns and mechanisms that determine the efficiency with which ribozomes bind mRNA, the elongation of ribosomes through the 5′-UTR, and the formation of a stable translation initiation complex are not clear. Genes that are highly expressed in S. cerevisiae seem to prefer a 5′-UTR rich in adenine and poor in guanine, particularly in the Kozak sequence, which occupies roughly the first six nucleotides upstream of the START codon.ResultsWe measured the fluorescence produced by 58 synthetic versions of the S. cerevisiae minimal CYC1 promoter (pCYC1min), each containing a different 5′-UTR. First, we replaced with adenine the last 15 nucleotides of the original pCYC1min 5′-UTR—a theoretically optimal configuration for high gene expression. Next, we carried out single and multiple point mutations on it. Protein synthesis was highly affected by both single and multiple point mutations upstream of the Kozak sequence. RNAfold simulations revealed that significant changes in the mRNA secondary structures occur by mutating more than three adenines into guanines between positions −15 and −9. Furthermore, the effect of point mutations turned out to be strongly context-dependent, indicating that adenines placed just upstream of the START codon do not per se guarantee an increase in gene expression, as previously suggested.ConclusionsNew synthetic eukaryotic promoters, which differ for their translation initiation rate, can be built by acting on the nucleotides upstream of the Kozak sequence. Translation efficiency could, potentially, be influenced by another portion of the 5′-UTR further upstream of the START codon. A deeper understanding of the role of the 5′-UTR in gene expression would improve criteria for choosing and using promoters inside yeast synthetic gene circuits.Electronic supplementary materialThe online version of this article (doi:10.1186/s13036-017-0068-1) contains supplementary material, which is available to authorized users.

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BackgroundIn bacteria, transcription units can be insulated by placing a terminator in front of a promoter. In this way promoter leakage due to the read-through from an upstream gene or RNA polymerase unspecific binding to the DNA is, in principle, removed. Differently from bacterial terminators, yeast S. cerevisiae terminators contain a hexamer sequence, the efficiency element, that strongly resembles the eukaryotic TATA box i.e. the promoter sequence recognized and bound by RNA polymerase II.ResultsBy placing different yeast terminators (natural and synthetic) in front of the CYC1 yeast constitutive promoter stripped of every upstream activating sequences and TATA boxes, we verified that the efficiency element is able to bind RNA polymerase II, hence working as a TATA box. Moreover, terminators put in front of strong and medium-strength constitutive yeast promoters cause a non-negligible decrease in the promoter transcriptional activity.ConclusionsOur data suggests that RNA polymerase II molecules upon binding the insulator efficiency element interfere with protein expression by competing either with activator proteins at the promoter enhancers or other RNA polymerase II molecules targeting the TATA box. Hence, it seems preferable to avoid the insulation of non-weak promoters when building synthetic gene circuit in yeast S. cerevisiae.Electronic supplementary materialThe online version of this article (doi:10.1186/s13036-016-0040-5) contains supplementary material, which is available to authorized users.

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