Atomistic Modeling of Peptide Aggregation and β-Sheet Structuring in Corn Zein for Viscoelasticity

Technological challenges and future perspectives of plant-based meat analogues: From the viewpoint of proteins

The global demand for high-quality animal protein faces challenges, prompting a surge in interest in plant-based meat analogues (PBMA). PBMA have emerged as a promising solution, although they encounter technological obstacles. This review discusses the technological challenges faced by PBMA from the viewpoint of plant proteins, emphasizing textural, flavor, color, and nutritional aspects. Texturally, PBMA confront issues, such as deficient fibrous structure, chewiness, and juiciness. Addressing meat flavor and mitigating beany flavor in plant protein are imperative. Furthermore, achieving a distinctive red or pink meat color remains a challenge. Plant proteins exhibit a lower content of essential amino acids. Future research directions encompass (1) shaping myofibril fibrous structures through innovative processing; (2) effectively eliminating the beany flavor; (3) developing biotechnological methodologies for leghemoglobin and plant-derived pigments; (4) optimizing amino acid composition to augment the nutritional profiles. These advancements are crucial for utilization of plant proteins in development of high-quality PBMA.

Conformations of a highly expressed Z19 α-zein studied with AlphaFold2 and MD simulations

α-zeins are amphiphilic maize seed storage proteins with material properties suitable for a multitude of applications e.g., in renewable plastics, foods, therapeutics and additive manufacturing (3D-printing). To exploit their full potential, molecular-level insights are essential. The difficulties in experimental atomic-resolution characterization of α-zeins have resulted in a diversity of published molecular models. However, deep-learning α-zein models are largely unexplored. Therefore, this work studies an AlphaFold2 (AF2) model of a highly expressed α-zein using molecular dynamics (MD) simulations. The sequence of the α-zein cZ19C2 gave a loosely packed AF2 model with 7 α-helical segments connected by turns/loops. Compact tertiary structure was limited to a C-terminal bundle of three α-helices, each showing notable agreement with a published consensus sequence. Aiming to chart possible α-zein conformations in practically relevant solvents, rather than the native solid-state, the AF2 model was subjected to MD simulations in water/ethanol mixtures with varying ethanol concentrations. Despite giving structurally diverse endpoints, the simulations showed several patterns: In water and low ethanol concentrations, the model rapidly formed compact globular structures, largely preserving the C-terminal bundle. At ≥ 50 mol% ethanol, extended conformations prevailed, consistent with previous SAXS studies. Tertiary structure was partially stabilized in water and low ethanol concentrations, but was disrupted in ≥ 50 mol% ethanol. Aggregated results indicated minor increases in helicity with ethanol concentration. β-sheet content was consistently low (∼1%) across all conditions. Beyond structural dynamics, the rapid formation of branched α-zein aggregates in aqueous environments was highlighted. Furthermore, aqueous simulations revealed favorable interactions between the protein and the crosslinking agent glycidyl methacrylate (GMA). The proximity of GMA epoxide carbons and side chain hydroxyl oxygens simultaneously suggested accessible reactive sites in compact α-zein conformations and pre-reaction geometries for methacrylation. The findings may assist in expanding the applications of these technologically significant proteins, e.g., by guiding chemical modifications.

The Amphiphilic Property and Structure of β-Amyloid Peptide Contribute to Its Impacts on the Activities of Horseradish Peroxidase and Alkaline Phosphatase

Recent studies have found that β-amyloid (Aβ) oligomers may play much more important roles than amyloid plaques in the pathogenesis of Alzheimer's disease (AD). However, due to the complexity of Aβ, studying the structural basis of Aβ oligomer toxicity is challenging. Here, we assessed the amphiphilic property and β-hairpin structure of Aβ monomer. The potential impacts of Aβ oligomers and three sequence-modifying peptides on the enzyme activities of horseradish peroxidase (HRP) and alkaline phosphatase (ALP) were further evaluated. We demonstrated that Aβ oligomer possesses the ability to alter the activity of two enzymes. Moreover, modifications on the hydrophobic region and β-turn structure of Aβ monomer significantly alter its impacts on the enzyme activities. In addition, these modifications also change the bonding modes of Aβ monomers or oligomers binding to HRP, as assessed by molecular docking. All of these findings provide direct experimental evidence to reveal the critical roles of the amphiphilic property and β-sheet structure of Aβ monomer in its impacts on protein activity.

Technological interventions in improving the functionality of proteins during processing of meat analogs

Meat analogs have opened a new horizon of opportunities for developing a sustainable alternative for meat and meat products. Proteins are an integral part of meat analogs and their functionalities have been extensively studied to mimic meat-like appearance and texture. Proteins have a vital role in imparting texture, nutritive value, and organoleptic attributes to meat analogs. Processing of suitable proteins from vegetable, mycoproteins, algal, and single-cell protein sources remains a challenge and several technological interventions ranging from the isolation of proteins to the processing of products are required. The present paper reviews and discusses in detail various proteins (soy proteins, wheat gluten, zein, algal proteins, mycoproteins, pulses, potato, oilseeds, pseudo-cereals, and grass) and their suitability for meat analog production. The review also discusses other associated aspects such as processing interventions that can be adapted to improve the functional and textural attributes of proteins in the processing of meat analogs (extrusion, spinning, Couette shear cell, additive manufacturing/3D printing, and freeze structuring). '.

Formulation, Characterisation and Evaluation of the Antihypertensive Peptides, Isoleucine-Proline-Proline and Leucine-Lysine-Proline in Chitosan Nanoparticles Coated with Zein for Oral Drug Delivery

Isoleucine-Proline-Proline (IPP) and Leucine-Lysine-Proline (LKP) are food-derived tripeptides whose antihypertensive functions have been demonstrated in hypertensive rat models. However, peptides display low oral bioavailability due to poor intestinal epithelial permeability and instability. IPP and LKP were formulated into nanoparticles (NP) using chitosan (CL113) via ionotropic gelation and then coated with zein. Following addition of zein, a high encapsulation efficiency (EE) (>80%) was obtained for the NP. In simulated gastric fluid (SGF), 20% cumulative release of the peptides was achieved after 2 h, whereas in simulated intestinal fluid (SIF), ~90% cumulative release was observed after 6 h. Higher colloidal stability (39−41 mV) was observed for the coated NP compared to uncoated ones (30−35 mV). In vitro cytotoxicity studies showed no reduction in cellular viability of human intestinal epithelial Caco-2 and HepG2 liver cells upon exposure to NP and NP components. Administration of NP encapsulating IPP and LKP by oral gavage to spontaneously hypertensive rats (SHR) attenuated systolic blood pressure (SBP) for 8 h. This suggests that the NP provide appropriate release to achieve prolonged hypotensive effects in vivo. In conclusion, chitosan-zein nanoparticles (CZ NP) have potential as oral delivery system for the encapsulation of IPP and LKP.