Effects of polyethylene oxide particles on the photo-physical properties and stability of FA-rich perovskite solar cells.

In this paper, we use Polyethylene Oxide (PEO) particles to control the morphology of Formamidinium (FA)-rich perovskite films and achieve large grains with improved optoelectronic properties. Consequently, a planar perovskite solar cell (PSC) is fabricated with additions of 5 wt% of PEO, and the highest PCE of 18.03% was obtained. This solar cell is also shown to retain up to 80% of its initial PCE after about 140 h of storage under the ambient conditions (average relative humidity of 62.5 ± 3.25%) in an unencapsulated state. Furthermore, the steady-state PCE of the PEO-modified PSC device remained stable for long (over 2500 s) under continuous illumination. This addition of PEO particles is shown to enable the tuning of the optoelectronic properties of perovskite films, improvements in the overall photophysical properties of PSCs, and an increase in resistance to the degradation of PSCs.

Development and validation of HPLC-MS2 methodology for the accurate determination of C4-C8 B-type flavanols and procyanidins.

Cocoa flavanols and procyanidins (CFs), natural dietary bioactives, have been studied extensively over the past two decades for their potential health benefits. Research on their safety and efficacy is critically dependent upon on the ability to reliably characeterize the research materials that are utilized, and with growing consumer availability of CF-based products, reliable methods for the detection of potential adulteration are of increasing importance. This research focused on the development of a high performance liquid chromatography-tandem mass spectrometry method (HPLC-MS2) using primary standards and 13C-labelled procyanidins as internal standards. The ability of MS2 detection to discriminate A- and B-type procyanidins was demonstrated. Method performances were validated for degrees of polymerization up to four in seven model food matrices. Accuracy ranged from 90.9 to 125.4% and precision was < 10% at lower concentrations. Finally, the method was applied to cocoa-based samples and compared to the AOAC 2020.05 analytical protocol, supporting the use of NIST 8403 as reference material for HPLC-MS2 analysis.

Barite as an industrial mineral in Nigeria: occurrence, utilization, challenges and future prospects.

Barite is a non-metallic mineral which is simply barium sulfate (BaSO4) and is largely used by the oil and gas industry as a weighting agent in drilling mud during drilling operations. The specific gravity of barite should range from 4.1 to 4.6 to be applicable as a drilling mud additive. This study considered the occurrence, utilization and challenges facing the mining of barite in Nigeria. It also discussed the global reserve, production and consumption of barite and types of barite ores and associated minerals in Nigeria. With the use of data from various ministries, departments and agencies involved in the records of operations within the Nigerian solid minerals sector, the nature of occurrence of barite in Nigeria has been reviewed. The various reported deposits areas have been elucidated while the associated minerals along with the quality reserve estimates have been discussed. Reported geochemical and geological studies of the barite mineralization in Nigeria show cream to grey, reddish-brown, whitish and pinkish varieties. The quality of the Nigerian barite is moderate to high. It is often associated with dolomite, fluorite, quartz, calcite, etc. The major impurities found in the mineral are iron oxide (goethite), quartz, and carbonates of magnesium, iron and calcium. Enumeration of the challenges facing the exploitation of the mineral has been revealed to include poor infrastructural development, safety and security, insufficient geophysical and geoscience data information and crude mining techniques. The barite production industry still has a huge potential for growth if these challenges are addressed.

Single-Laboratory Validation for the Determination of Cocoa Flavanols and Procyanidins (by Degree of Polymerization DP1-7) in Cocoa-Based Products by Hydrophilic Interaction Chromatography Coupled with Fluorescence Detection: First Action 2020.05.

BACKGROUND: Flavanols and procyanidins are complex bioactives found in many foods such as cocoa. As their consumption is associated with health benefits, cocoa flavanols and procyanidins are receiving increasing attention from consumers, industry, researchers, and regulators. OBJECTIVE: The objective of this study is to validate a method using hydrophilic interaction chromatography (HILIC) with fluorescence detection (FLD) and a commercially available reference material for the determination of flavanols and procyanidins (CF) in cocoa-based products. METHODS: Method performances were evaluated for cocoa matrices with CF content that ranged from 0.8 to 500 mg/g, which included low CF matrices (milk and dark chocolate, cocoa powder, and liquor) and high CF matrices (cocoa extract and dietary supplement products). The method was validated in a single-laboratory by determining sensitivity, selectivity, linearity, stability, robustness, accuracy, and precision for each of the matrices. RESULTS: The method was validated for cocoa matrices with CF content that ranged from 0.8 to 500 mg/g. Accuracy ranged from 86 to 99% and repeatability (RSDr) from 1.5 to 8.6% for CF. CONCLUSIONS: Analytical performances acquired through this single-laboratory validation study for a wide range of cocoa-based matrices demonstrate that this method is fit-for-purpose for the determination of flavanols and procyanidins in cocoa-based products. HIGHLIGHTS: Hydrophilic interaction chromatography (HILIC) with fluorescence detection was successfully used to determine total CF content in multiple product types. Single-laboratory method validation results demonstrate that the method is fit for purpose for cocoa-based matrices containing <0.8 to 500 mg/g of CF.

Reliable, accessible and transferable method for the quantification of flavanols and procyanidins in foodstuffs and dietary supplements.

Flavanols and procyanidins are plant-derived bioactives that are receiving increasing attention because of their potential health benefits. Analytical tools that can accurately identify and reproducibly quantify these bioactives are critical to researchers for test material characterization, as well as to the food industry and regulators, notably for product labeling. However, the chemical complexity of procyanidins, and the absence of analytical standards have prevented the development of methods that could serve the needs of these different sectors. This report describes the development and validation of a reliable, accessible and transferable method for the quantification of flavanol monomers and procyanidins in cocoa-derived dietary supplements and foodstuffs. To accomplish this, flavanols and procyandins from cocoa, one of the most studied dietary sources of these compounds, were used as a model system. To overcome limitations related to the absence of analytical standards, a cocoa extract was thoroughly characterized for use as a calibrant. It was then used in the development and validation of a method based on reliable and accessible instrumentation, namely HPLC coupled with fluorescence detection. The resulting method permitted the quantification of flavanols and procyanidins in amounts ranging from 2 to 500 mg g-1, with high precision (%RSD 0.2 to 1.9%) and accuracy (100.7 to 102.9%). The method was successfully applied to assess the flavanol and procyanidin content of different cocoa-based commercial products. Furthermore, the high precision of the methods showed the feasibility of using principal component analysis of flavanol and procyanidin profiles to discriminate cocoa-derived products by origin and manufacturing processes. A feature that offers advantages in monitoring product authenticity/adulteration. Overall, these findings support the application of this method for the routine analysis of cocoa flavanols and procyandins.

Wilms tumor protein recognizes 5-carboxylcytosine within a specific DNA sequence.

In mammalian DNA, cytosine occurs in several chemical forms, including unmodified cytosine (C), 5-methylcytosine (5 mC), 5-hydroxymethylcytosine (5 hmC), 5-formylcytosine (5 fC), and 5-carboxylcytosine (5 caC). 5 mC is a major epigenetic signal that acts to regulate gene expression. 5 hmC, 5 fC, and 5 caC are oxidized derivatives that might also act as distinct epigenetic signals. We investigated the response of the zinc finger DNA-binding domains of transcription factors early growth response protein 1 (Egr1) and Wilms tumor protein 1 (WT1) to different forms of modified cytosine within their recognition sequence, 5'-GCG(T/G)GGGCG-3'. Both displayed high affinity for the sequence when C or 5 mC was present and much reduced affinity when 5 hmC or 5 fC was present, indicating that they differentiate primarily oxidized C from unoxidized C, rather than methylated C from unmethylated C. 5 caC affected the two proteins differently, abolishing binding by Egr1 but not by WT1. We ascribe this difference to electrostatic interactions in the binding sites. In Egr1, a negatively charged glutamate conflicts with the negatively charged carboxylate of 5 caC, whereas the corresponding glutamine of WT1 interacts with this group favorably. Our analyses shows that zinc finger proteins (and their splice variants) can respond in modulated ways to alternative modifications within their binding sequence.

Structural basis for Klf4 recognition of methylated DNA.

Transcription factor Krüppel-like factor 4 (Klf4), one of the factors directing cellular reprogramming, recognizes the CpG dinucleotide (whether methylated or unmodified) within a specific G/C-rich sequence. The binding affinity of the mouse Klf4 DNA-binding domain for methylated DNA is only slightly stronger than that for an unmodified oligonucleotide. The structure of the C-terminal three Krüppel-like zinc fingers (ZnFs) of mouse Klf4, in complex with fully methylated DNA, was determined at 1.85 Å resolution. An arginine and a glutamate interact with the methyl group. By comparison with two other recently characterized structures of ZnF protein complexes with methylated DNA, we propose a common principle of recognition of methylated CpG by C2H2 ZnF proteins, which involves a spatially conserved Arg-Glu pair.

DNA recognition of 5-carboxylcytosine by a Zfp57 mutant at an atomic resolution of 0.97 Å.

The Zfp57 gene encodes a KRAB (Krüppel-associated box) domain-containing C2H2 zinc finger transcription factor that is expressed in early development. Zfp57 protein recognizes methylated CpG dinucleotide within GCGGCA elements at multiple imprinting control regions. In the previously determined structure of the mouse Zfp57 DNA-binding domain in complex with DNA containing 5-methylcytosine (5mC), the side chains of Arg178 and Glu182 contact the methyl group via hydrophobic and van der Waals interactions. We examined the role of Glu182 in recognition of 5mC by mutagenesis. The majority of mutants examined lose selectivity of methylated (5mC) over unmodified (C) and oxidative derivatives, 5-hydroxymethylcytosine, 5-formylcytosine, and 5-carboxylcytosine (5caC), suggesting that the side chain of Glu182 (the size and the charge) is dispensable for methyl group recognition but negatively impacts the binding of unmodified cytosine as well as oxidized derivatives of 5mC to achieve 5mC selectivity. Substitution of Glu182 with its corresponding amide (E182Q) had no effect on methylated DNA binding but gained significant binding affinity for 5caC DNA, resulting in a binding affinity for 5caC DNA comparable to that of the wild-type protein for 5mC. We show structurally that the uncharged amide group of E182Q interacts favorably with the carboxylate group of 5caC. Furthermore, introducing a positively charged arginine at position 182 resulted in a mutant (E182R) having higher selectivity for the negatively charged 5caC.