Structure,composition and functional properties of storage proteins extracted from bambara groundnut (Vigna subterranea) landraces

Bambara groundnut is a protein‐rich traditional legume. In this study, storage proteins were isolated from three bambara landraces. Bambara protein revealed four major protein bands: one broad band at 55 kDa, two medium bands at 62 kDa and 80 kDa and a high molecular weight (HMW) protein at 141 kDa. The vicilin (7S) subunits with molecular weight of 55 kDa and 62 kDa were major fractions in bambara storage proteins. Bambara proteins showed two endothermic peaks ranging from 64 to 69 °C and 76 to 90 °C, respectively. Bambara protein isolates had well‐defined tertiary and secondary structures, respectively, at pH 3.0, and this well‐defined structure decreased slightly at higher pH values. The isolates revealed a strong secondary structure dominated by α‐helical conformation. Foaming capacities of bambara proteins were dependent on pH with maximum percentage FC observed at pH 3.0, while the emulsion activity increased with increasing pH for all the isolates. Vicilin (7S) fraction seems to be the major storage protein fraction of bambara. Bambara proteins could serve as excellent ingredients for the formulation of food foams and emulsions.     

The synthesis and photophysicochemical behaviour of novel water-soluble cationic indium(III) phthalocyanine

The syntheses and characterization of 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) and quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) are described. The ground state electronic absorption spectra, photophysics and photochemistry of both dyes in DMSO as well as that of the quaternized compound in aqueous solution are also presented. A comparison of the photophysical and photochemical parameters of the two dyes revealed that quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) was a better photosensitizer than its unquaternized counterpart. The quantum yield values of fluorescence (Φ_F), triplet state formation (Φ_T) and singlet oxygen formation (Φ_Δ) for the cationic dye were found to be 0.03, 0.68 and 0.66 respectively in DMSO; these values were higher than those for 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III), which exhibited values of 0.02, 0.66 and 0.63, respectively in DMSO. The values for the cationic dye in aq. solution were 0.02, 0.59 and 0.56 respectively, suggesting that the water-soluble quaternized 2,3-octakis-(3-pyridyloxyphthalocyaninato) indium(III) offers potential as a photosensitizer in photodynamic therapy treatment.     

Development and sensory acceptability of crackers made from the big-eye fish (Brachydeuterus auritus)

The big-eye (Brachydeuterus auritus), which is present in a large biomass in the Gulf of Guinea, is generally considered an underutilized fish species. In an attempt to add value, it was used to complement cassava starch (Manihot esculenta Crantz) to produce fish crackers. Three levels of fish (40%, 50%, and 60%) and three levels of starch (60%, 50%, and 40%) were used in the formulations. Proximate analyses and sensory evaluations were carried out. The protein, fat, and ash contents increased with an increase in the proportion of fish. The sensory evaluation tests showed that the most acceptable formulations for the crackers were obtained using 50% fish/50% starch and 40% fish/60% starch combinations. The linear expansion of the fried crackers increased with the increased proportion of fish. Production of fish crackers, apart from its appeal for increasing protein intake, has the potential to support a small regional snack factory in a developing economy.     

Fungi and mycotoxins in cowpea (Vigna unguiculata L) on Nigerian markets

ABSTRACT

In this study, 81 samples of two cowpea varieties (brown: 54; white: 27) collected from various markets in southwestern Nigeria were examined for fungal and mycotoxin contamination. Moulds belonging to Aspergillus, Fusarium, and Penicillium were recovered from 99% of the samples. In both cowpea varieties, Aspergillus (52–53%) dominated Fusarium (29–30%) and Penicillium (17–20%). The interactive effect of cowpea variety and sampled location was significant (p = .013) on the occurrence of Fusarium species. Aflatoxins were detected in one brown and two white cowpea samples at concentrations reaching 209 and 84 µg/kg, respectively. Additionally, beauvericin was found in two samples of each cowpea variety, albeit at low concentrations. Cowpea presents as an alternative vegetable protein source to groundnuts in household nutrition with respect to mycotoxin contamination. Simple techniques to prevent mycotoxins in dry cowpeas are discussed.     

Computational Evolution of Beta-2-Microglobulin Binding Peptides for Nanopatterned Surface Sensors

The bottom-up design of smart nanodevices largely depends on the accuracy by which each of the inherent nanometric components can be functionally designed with predictive methods. Here, we present a rationally designed, self-assembled nanochip capable of capturing a target protein by means of pre-selected binding sites. The sensing elements comprise computationally evolved peptides, designed to target an arbitrarily selected binding site on the surface of beta-2-Microglobulin (β2m), a globular protein that lacks well-defined pockets. The nanopatterned surface was generated by an atomic force microscopy (AFM)-based, tip force-driven nanolithography technique termed nanografting to construct laterally confined self-assembled nanopatches of single stranded (ss)DNA. These were subsequently associated with an ssDNA–peptide conjugate by means of DNA-directed immobilization, therefore allowing control of the peptide’s spatial orientation. We characterized the sensitivity of such peptide-containing systems against β2m in solution by means of AFM-based differential topographic imaging and surface plasmon resonance (SPR) spectroscopy. Our results show that the confined peptides are capable of specifically capturing β2m from the surface–liquid interface with micromolar affinity, hence providing a viable proof-of-concept for our approach to peptide design.     

Beta dielectric dispersion in natural rubber latex

The dielectric dispersion of natural rubber latex has been investigated over a frequency range of 0.1–100 MHz and at six temperatures from 20° to 70°C. A computer analysis of the dispersion data showed that the Cole–Cole structural equation gave a better fit than the Debye. The large values of the Cole-Cole α spread parameter suggest heterogeneity of structure in rubber latex. The latex viscosity and the relaxation time were both found to be influenced by changes in temperature. Application of the Arrhenius temperature equation to the data yielded a mean activation enthalpy of 32.6 ± 2.8 kJ/mol for the relaxation process.     

Influence of extraction methods on functional properties of protein concentrates prepared from South African bambara groundnut landraces

Functional properties of protein concentrates prepared from three bambara groundnut landraces using acid precipitation and salt solubilisation methods were evaluated. The protein content of bambara grains (26–27%) was similar for the three landraces. The acid precipitation gave a much higher yield of protein concentrates (52%), which were also high in protein (79%) compared to the salt solubilisation method (yield: 25%, protein content: 57%). Functional properties of proteins were more influenced by the methods of preparation rather than the landraces. Protein concentrate prepared by salt solubilisation method showed higher emulsifying (63–66%), foaming (53–57%), water (1.4–2.0 mg mL^?1) and oil absorption properties (2.2–2.6 mg mL^?1) than the acid‐precipitated concentrates (53–57%, 63–66%, 2.0–2.7 mg mL^?1, 1.4–1.7 mg mL^?1). The foaming capacity and stability of all the protein concentrates decreased with increasing pH from 3 to 8. Salt solubilisation may be the most appropriate method for the enhanced functionality and utilisation of bambara groundnuts’ protein concentrates.     

四元复合薄膜的形成特征、摩擦特性和耐腐蚀性能

在工程应用中增强材料的腐蚀磨损性能是至关重要的。采用电沉积技术,研究从氯化物槽池中得到的Zn-Al-SnO 2-TiO 2（Zn-Al-Sn-Ti）复合薄膜的结构、电氧化性能。采用扫描电子显微镜联合能谱仪、光学显微镜和X射线衍射,研究薄膜的微观结构。采用动电位极化技术,研究在3.65%Na Cl溶液中薄膜的电化学氧化和腐蚀行为,并采用原子力显微镜对其进行表征。采用高钻石硬扫描显微硬度测试仪和CERT往复滑动仪,研究电沉积薄膜的硬度和磨损行为。结构发现,成功获得了共沉积的复合材料和粒子,并得到了均匀、精细的嵌入颗粒结构以及改善的微观力学性能。所制备的四元薄膜的耐腐蚀性、硬度和稳定的耐磨性得到显著提高。