Unbiased Immunization Strategy Yielding Specific Nanobodies against Macadamia Allergen of Vicilin-like Protein for Immunoassay Development

Macadamia nut contains important food allergens that potentially cause allergic reactions with severe adverse effects in infants and adults. Reliable and accurate detection of macadamia is critical to avoid allergic reactions. However, knowledge on macadamia allergen is scarce and a reliable detection method has not been reported, yet. In this study, an unbiased immunization and selection strategy was employed to select nanobodies (Nbs) recognizing specifically macadamia allergen, as well as to establish a detection method to unveil a macadamia protein contamination. An alpaca was immunized with a crude protein extract of macadamia followed by construction of a Nb library from its lymphocytes. The panning and screening of this immune Nb repertoire resulted in the selection of six target-specific Nbs. Nb-mediated immuno-capturing combined with mass spectrometry allowed us to identify the target as the macadamia vicilin-like antimicrobial peptides 2-3 (MiAMP2), a novel food allergenic protein abbreviated as Mac i 1. Later on, an immunoassay of a heterologous sandwich ELISA method based on the selected Nb-pairs was established, providing a linear response in the range of 0.442-2,800 μg/mL and with a limit of detection of 27.1 ng/mL. The dedicated immunoassay has been verified by detecting the antigen spiked in food samples. Our study provided evidence for the successful application of the unprejudiced strategy to retrieve Nbs against a priori undefined macadamia allergen. These target-specific Nbs were used to design a highly reliable and effective immunoassay.

Optimization of hexametaphosphate-assisted extraction and functional characterization of palm kernel cake protein

Response surface methodology was applied to study the optimization of palm kernel cake protein (PKCP) hexametaphosphate-assisted extraction. The optimum PKCP yield (28.37%) when extracted using 1.50% sodium hexametaphosphate (SHMP) of pH 10, at 50 °C, and the 1:70 (w/v) ratio of cake-to-solvent was significantly ( P < 0.05) higher than the protein yield from an alkaline (pH 10) extraction (8.12 ± 0.24%). Differential scanning calorimetry (DSC) analysis showed a higher denatured temperature (99.78 °C) for PKCP as compared with alkaline extracted one (96.96 °C), suggesting that a less denatured protein population is obtained. Electrophoresis of the PKCP revealed that the protein has 11 bands with MW ranging from 2.11 to 83.19 kDa. Relative to soy protein isolate, PKCP showed higher surface hydrophobicity (165.96 vs. 51.51), better solubility at pH 7 (87.65% vs. 41.21%), oil-binding capacity (7.73 vs. 2.96 g/g) and emulsifying activity (178.50 vs. 32.57 m2/g), but lower water-binding capacity (0.36 vs. 11.70 g/g), emulsifying stability (32.24% vs. 43.08%), foaming capacity (20.8% vs. 100.0%) and foam stability (3.80 vs. 19.20 ml). PKCP contained the highest amount of glutamic acid (16.86 g/100 g protein) and followed by arginine (10.78 g/100 g protein). With respect to the 1991 standard of the FAO/WHO for preschool children, PKCP’s essential amino acid profile showed deficiencies. Therefore, it can be used as a complementary protein source by supplementing with a tryptophan-rich source, as this was the limiting amino acid.

Optimized protein extraction methods for proteomic analysis of Rhizoctonia solani

Rhizoctonia solani (Teleomorph: Thanatephorus cucumeris, T. praticola) is a basidiomycetous fungus and a major cause of root diseases of economically important plants. Various isolates of this fungus are also beneficially associated with orchids, may serve as biocontrol agents or remain as saprophytes with roles in decaying and recycling of soil organic matter. R. solani displays several hyphal anastomosis groups (AG) with distinct host and pathogenic specializations. Even though there are reports on the physiological and histological basis of Rhizoctonia-host interactions, very little is known about the molecular biology and control of gene expression early during infection by this pathogen. Proteamic technologies are powerful tools for examining alterations in protein profiles. To aid studies on its biology and host pathogen interactions, a two-dimensional (2-D) gel-based global proteomic study has been initiated. To develop an optimized protein extraction protocol for R. solani, we compared two previously reported protein extraction protocols for 2-D gel analysis of R. solani (AG-4) isolate Rs23. Both TCA-acetone precipitation and phosphate solubilization before TCA-acetone precipitation worked well for R. solani protein extraction, although selective enrichment of some proteins was noted with either method. About 450 spots could be detected with the densitiometric tracing of Coomassie blue-stained 2-D PAGE gels covering pH 4-7 and 6.5-205 kDa. Selected protein spots were subjected to mass spectrometric analysis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Eleven protein spots were positively identified based on peptide mass fingerprinting match with fungal proteins in public databases with the Mascot search engine. These results testify to the suitability of the two optimized protein extraction protocols for 2-D proteomic studies of R. solani.

Proximate composition of Karkadeh (Hibiscus sabdariffa) seeds and some functional properties of seed protein isolate as influenced by pH and NaCl

Seeds of an inbred line (B-11-90) of Karkadeh (Hibiscus sabdariffa) were investigated for their proximate composition (AOAC methods), nitrogen solubility and protein isolate (Karkadeh seed protein isolates [KSPI]) functional properties (standard methods). The fat and protein contents of the seeds were 22.43% and 32.46%, respectively. Nitrogen solubility was good in both water and 1.0 M NaCl at alkaline pH rather than at acidic pH, with better solubility at higher pH levels in water than in 1.0 M NaCl. The functional properties of the KSPI were as follows: water absorption capacity, 181 ml/100 g; fat absorption capacity, 110 ml/100 g; bulk density, 0.77 g/ml; and apparent viscosity (at 20 degrees C), 13.42 cps. KSPI showed a maximum foaming capacity at pH 12 and 1.6 M NaCl, a maximum emulsification capacity at pH 11 and 1.8 M NaCl, and a weaker foam stability at neutral pH than at acidic or alkaline pH, with a better foam stability at alkaline pH. The foam stability was considerably improved by treatment with 1.6 M NaCl.