Specific ions effect on aggregation behaviors and structural changes of amyloid fibrils from rice glutelin

Metal ions have been considered as an important factor on fibrils assembly. Herein, a comprehensive analysis of specific ions effect on fibril formation and structural changes was investigated. The addition of ions (except Zn2+) accelerated the aggregation kinetics of rice glutelin fibrils (RGFs) from 0.93 to 1.28-2.19 h-1. In addition, the fibrillization rate followed the order of NH4+ > Li+ > Na+ > K+ > Cu2+ > Mg2+ > Ca2+ > Zn2+. The highest yield and length of fibrils were observed with Ca2+, probably due to the ionic bridging effect and hydrated capacity of Ca2+. However, Cu2+ reduced the fibrils yield, which was attributable to the fact that Cu2+ disrupted β-sheet structure and inhibited the transition of monomer to fibrils. The polymorphism of fibrils was observed with different salts, and the light metals presented a superior effect on fibrils formation than heavy metals. Overall, this work will provide a further information into how to tune the structure of RGFs using various ions.

Effect of phlorotannin extracts from Ascophyllum nodosum on the textural properties and structural changes of Apostichopus japonicus

In this work, phlorotannin extracts (PhTEs) were isolated from Ascophyllum nodosum. The effects of PhTEs on the textural properties, structural changes and oxidation level of Apostichopus japonicus (A. japonicus) were investigated. The results showed that thermal treatment could lead to the dissolution of TCA-soluble peptides and free hydroxyproline and promote the degradation of A. japonicus. The chemical compositional changes and texture profile analysis results indicated that PhTEs could effectively inhibit the degradation of A. japonicus and improve the hardness and chewiness of A. japonicus. Analysis of multiple spectroscopic methods suggested that the secondary and tertiary conformations tended to be stable after PhTEs were added. In addition, electron spin resonance results indicated that PhTEs could reduce the oxidation level of A. japonicus. These results suggest that the degradation of A. japonicus during mild heat treatment can be regulated by PhTEs, which provides insights for quality control in A. japonicus heat treatment.

The in-silico study of the structural changes in the Arthrobacter globiformis choline oxidase induced by high temperature

BACKGROUND

Choline oxidase, a flavoprotein, is an enzyme that catalyzes the reaction which converts choline into glycine betaine. Choline oxidase started its journey way back in 1933. However, the impact of the high temperature on its structure has not been explored despite the long history and availability of its crystal structure. Both choline oxidase and its product, glycine betaine, have enormous applications spanning across multiple industries. Understanding how the 3D structure of the enzyme will change with the temperature change can open new ways to make it more stable and useful for industry.

PROCESS

This research paper presents the in-silico study and analysis of the structural changes of A. globiformis choline oxidase at temperatures from 25 °C to 60 °C. A step-wise process is depicted in Fig. 1.

RESULTS

Multiple sequence alignment (MSA) of 11 choline oxidase sequences from different bacteria vs Arthrobacter globiformis choline oxidase showed that active site residues are highly conserved. The available crystal structure of A. globiformis choline oxidase with cofactor Flavin Adenine Dinucleotide (FAD) in the dimeric state (PDB ID: 4MJW)1 was considered for molecular dynamics simulations. A simulated annealing option was used to gradually increase the temperature of the system from 25 °C to 60 °C. Analysis of the conserved residues, as well as residues involved in Flavin Adenine Dinucleotide (FAD) binding, substrate binding, substate gating, and dimer formationwas done. At high temperatures, the formation of the inter-chain salt bridge between Arg50 and Glu63 was a significant observation near the active site of choline oxidase.

CONCLUSION

Molecular dynamics studies suggest that an increase in temperature has a significant impact on the extended Flavin Adenine Dinucleotide (FAD) binding region. These changes interfere with the entry of substrate to the active site of the enzyme and make the enzyme inactive.

Structural changes of layer-by-layer self-assembled starch-based nanocapsules in the gastrointestinal tract: Implications for their M cell-targeting delivery and transport efficiency

Characterizing the structural changes of cell-targeting delivery carriers in gastrointestinal tract (GIT) is crucial for understanding their effectiveness in cell targeting and transport. Herein, RGD peptide-grafted carboxymethyl starch (CMS) and cationic quaternary ammonium starch (QAS) were utilized to fabricate quintet-layered nanocapsules loaded with ovalbumin (OVA). The aim was to improve delivery and transportation efficiency, specifically targeting M cells. The research analyzed the impact of pH and enzyme variations in GIT on the structure of nanocapsules, interactions between carriers and the release behavior of OVA. Results showed that the size of nanocapsules increased from 229.2 to 479.8 nm and the zeta potential decreased from -1.08 to -33.33 mV during oral delivery. This was evident in TEM images, showing a more relaxed core-shell structure. Isothermal titration calorimetry and molecular dynamic simulation indicated that pH changes primarily affected the electrostatic interaction between carriers. Increasing pH led to reduced affinity constants, and around 84.42 % of OVA was successfully delivered to M cells. Moreover, the transport efficiency of nanocapsules to M cells was five times greater than that of Caco-2 cells. This suggests the feasibility of developing a nanocapsules delivery system capable of adapting to pH changes in GIT by regulating electrostatic interactions between carriers.

Effects of conjugated interactions between Perilla seed meal proteins and different polyphenols on the structural and functional properties of proteins

The study aims to perform alkali-induced covalent modification of perilla seed meal protein (PSMP) using different polyphenols: gallic acid (GA), protocatechuic acid (PCA), caffeic acid (CA), apigenin (API) and luteolin (LU). Covalent binding between different polyphenols and PSMP was found to occur, with PSMP-LU showing the highest binding rate of 90.89 ± 1.37 mg/g; the fluorescence spectrum of PSMP-CA showed a maximum blue shift of Δ13.4 nm; the solubility increased from 69.626 ± 1.39 % to 83.102 ± 0.98 %. In order to better understand how these covalent conjugates, stabilize -carotene in emulsions, they were utilized as emulsifiers in an emulsion delivery method. The work further reveals the formation of PSMP-polyphenol conjugates and develops a novel emulsification system to deliver readily decomposable functional factors, providing a potential scenario for the application of PSMP and bioactive conjugates.

Inhibition mechanism of rice glutelin on extruded starch digestion: From the structural properties of starch and enzyme activity

To increase the anti-digestion ability of extruded rice starch (ERS), the influence of rice glutelin (RG) on digestive and structural characteristics of ERS were investigated. The resistant starch content increased from 4.49 % to 18.08 % as the RG content increased, while the digestion rate and digestion velocity constant were reduced by the incorporation of RG. Morphological observations showed that ERS was adhered and encapsulated by RG, and the specific area of starch granules were decreased after the addition of RG. The results of XRD and FTIR suggested that the long-range and short-range orders of ERS were improved due to the complexation with RG. The thickness of crystalline of ERS was increased while its amorphous region thickness was reduced by the supplementation with RG. The 1H NMR and 13C NMR data revealed that the branching degree and double helix content of ERS was increased by 46.24 % and 52.67 % when RG content reached to 12 %. Additionally, the addition of RG altered the molecular weight and chain length distribution of ERS. The α-amylase activity and glucoamylase activity was inhibited by RG. These results could provide a valuable basis for the application of RG in extruded rice starchy foods with lower glycemic index.

Sulfonamides stimulate ROS formation upon glycation of human carbonic anhydrase II

Advanced glycation end products are the most important species of glycation pathway, and cause disorders such as oxidative stress and diabetes. Sulfonamide compounds, which are generally known as widespread inhibitors, are potential agents used in different drug products, which can readily enter biological matrices. In the present work, the structure and activity of human carbonic anhydrase II studied in the presence of glucose as well as four sulfonamide agents from different views. These included enzyme kinetics, free lysine content, fluorescence spectroscopy, circular dichroism, and ROS measurement. Our results indicated that upon glycation, the structure of HCA II collapses and 8 to 13 lysine residues will be more available based on ligand incubation. Secondary and tertiary structural changes were also observed in the presence and absence of sulfonamide agents using fluorescence and circular dichroism methods, respectively. These spectroscopic data also showed a remarkable increase in hydrophobicity and decrease in α-helix contents during glycation, especially after 35 days of incubation. ROS assay was studied in the presence of glucose and sulfonamide compounds, that demonstrated the role of sulfonamide compounds in ROS formation in the presence of glucose in a synergistic manner. Overall, our data indicated that sulfonamides act as a stimulant factor upon prolonged interaction with HCA II and may intensify the complications of some disorders, such as diabetes and other conformational diseases.

Enhanced properties of non-starch polysaccharide and protein hydrocolloids through plasma treatment: A review

Hydrocolloids are important ingredients in food formulations and their modification can lead to novel ingredients with unique functionalities beyond their nutritional value. Cold plasma is a promising technology for the modification of food biopolymers due to its non-toxic and eco-friendly nature. This review discusses the recent published studies on the effects of cold plasma treatment on non-starch hydrocolloids and their derivatives. It covers the common phenomena that occur during plasma treatment, including ionization, etching effect, surface modification, and ashing effect, and how they contribute to various changes in food biopolymers. The effects of plasma treatment on important properties such as color, crystallinity, chemical structure, rheological behavior, and thermal properties of non-starch hydrocolloids and their derivatives are also discussed. In addition, this review highlights the potential of cold plasma treatment to enhance the functionality of food biopolymers and improve the quality of food products. The mechanisms underlying the effects of plasma treatment on food biopolymers, which can be useful for future research in this area, are also discussed. Overall, this review paper presents a comprehensive overview of the current knowledge in the field of cold plasma treatment of non-starch hydrocolloids and their derivatives and highlights the areas that require further investigation.

Changes in physicochemical and structural properties of pea protein during the high moisture extrusion process: Effects of carboxymethylcellulose sodium and different extrusion zones

This study investigated effects of carboxymethylcellulose sodium (CMC) on the conformational evolution of pea protein during the high moisture extrusion process. The morphological observation showed that the addition of CMC facilitated the formation of fibrous structure of pea protein. In comparison with the pea protein in the melting zone and extrudate, the combination of CMC increased the denaturation enthalpy of pea protein by 2.09 % and 2.34 %. Compared with the material in the mixing zone, the degree of grafting between CMC and pea protein in the die was enhanced by 98.95 %. In general, the supplementation of CMC depressed the exposure of hydrophobic groups in the pea protein. In the extrusion barrel, the CMC increased the unfolding of protein molecular chains while it promoted the refolding of protein chains in the die. For the extrudate, the addition of CMC decreased the contents of α-helix and β-sheet of pea protein by 9.67 % and 6.93 % while the contents of β-turn and random coil were increased, leading to changes in the molecular weight distribution of protein molecules. In conclusion, these results provided new strategies toward producing the high-quality pea protein-based meat analogues by adding CMC.

Approach to anaerobic bio-degradation of natural and synthetic fabrics: Physico-chemical study of the alteration processes

In this paper, the mesophilic Biochemical Methane Potential of several fabrics was assessed at different Total Solid concentrations (1-4%TS). Physico-chemical techniques were applied to explore the arising structural changes on fibers during the anaerobic digestion process. Additionally, the modified Gompertz model was used to assess and compare the AD performance of the fabrics. In cellulose-based fibers the production of biogas was enhanced thanks to the easy solubilization of acetate, which is generated upon partial breakage of cellulose bonds. The crystallinity of vegetal fibers decreased significantly from day 19. The highest methane yields were attained for silk and wool fabrics at the lowest TS concentrations. Conformational changes in fibroin and keratin were detected. The highest degrees of degradation were observed in solid samples with lower solid concentrations. Accordingly, the maximum methane yields were reported in the reactors operating with lower TS.

Effects of covalent conjugation with quercetin and its glycosides on the structure and allergenicity of Bra c p from bee pollen

Profilin family members are potential pan-allergens in foods, presenting public health hazards. However, studies on the allergenicity modification of profilin allergens are limited. Herein, quercetin and its glycosides (isoquercitrin and rutin) were applied to modify the allergenicity of a profilin allergen (Bra c p) from Brassica campestris bee pollen. Results showed that only quercetin can be closely covalently bound to Bra c p among the three, and the binding site was located at the Cys98 residue. After covalently conjunction, the relative content of α-helix structure in Bra c p was reduced by 40.05%, while random coil was increased by 42.89%; moreover, the Tyr and Phe residues in Bra c p were masked. These structural changes could alter the conformational antigenic epitopes of Bra c p, resulting in its allergenicity reduction. Our findings might provide a technical foundation for reducing the allergenicity of bee pollen and foods containing profilin family allergens.

Convergence of Income Inequality in OECD Countries Since 1870: A Multi-Method Approach with Structural Changes

This paper aims to examine convergence of income inequality in 21 OECD countries using several empirical techniques. In particular, we have used a new panel stationarity test, which allows for structural changes and cross-sectional dependence to examine the stochastic convergence of income inequality. We also employed a time series approach, residual augmented least squares-Lagrange multiplier unit root test. The empirical results show evidence for absolute, conditional, and sigma convergence. The conditional convergence test results suggest that countries are converging, but conditional on the two structural factors-economic and population growth. The stochastic convergence test results indicate the existence of convergence at the country-specific level. The results further confirm the existence of convergent clubs among OECD countries.

Tolerance mechanisms to aluminum in popcorn inbred lines involving aluminum compartmentalization and ascorbate-glutathione redox pathway

Inbred line 11-133 of popcorn showed the lowest apoplast Al and total Al concentrations and Al-lumogallion complex, associated with a more efficient antioxidant system, mainly due to glutathione metabolism. Popcorn (Zea mays L. var. everta) is largely intended for human consumption. About 40% of the world's arable soils are acidic. In soils acidic, aluminum (Al) ionizes producing the trivalent cation, which is highly toxic to plants. Hence, this work aimed to: (1) evaluate the Al toxicity sites and its effect on the structure of the root tips, (2) quantify Al concentrations in the apoplast and symplast of the roots, and (3) to elucidate the modulation on the activity of antioxidant enzymes and metabolites of the ascorbate-glutathione cycle in two popcorn inbred lines (ILs) 11-133 and 11-60, classified as tolerant and sensitive to this metal, respectively. Aluminum toxicity did not affect the shoot growth; however, there was a yellowing of the oldest leaf blade only in 11-60. The better performance of 11-133 is related to lower apoplastic and total Al concentrations and Al accumulation in the root associated with a lower fluorescence of Al-lumogallion complex at the root tip, indicating the presence of mechanisms of chelation with this metal. Consequently, this IL showed less change in root morphoanatomy and lower reactive oxygen species and malondialdehyde content, which are associated with a more efficient enzymatic and non-enzymatic system, mainly due to the higher content of the glutathione metabolite and the higher activities of superoxide dismutase, monodehydroascorbate reductase, dehydroascorbate reductase, γ-glutamylcysteine synthetase, and glutathione peroxidase enzymes. Thus, these findings illustrated above indicate how internal mechanisms of detoxification respond to Al in popcorn, which can be used as tolerance biomarkers.

Introducing comprehensive multiphase NMR for the analysis of food: Understanding the hydrothermal treatment of starch-based foods

Cooking is essential for preparing starch-based food, however thermal treatment promotes the complexation of biopolymers, impacting their final properties. Comprehensive Multiphase (CMP) NMR allows all phases (liquids, gels, and solids) to be differentiated and monitored within intact samples. This study acts as a proof-of-principle to introduce CMP-NMR to food research and demonstrate its application to monitor the various phases in spaghetti, black turtle beans, and white long-grain rice, and how they change during the cooking process. When uncooked, only a small fraction of lipids and structurally bound water show any molecular mobility. Once cooked, little "crystalline solid" material is left, and all components exhibit increased molecular dynamics. Upon cooking, the solid-like components in spaghetti contains signals consistent with cellulose that were buried beneath the starches in the uncooked product. Thus, CMP-NMR holds potential for the study of food and related processes involving phase changes such as growth, manufacturing, and composting.

Aluminum promotes changes in rice root structure and ascorbate and glutathione metabolism

In acidic soil, aluminum (Al) ionizes into trivalent cation and becomes highly toxic to plants. Thus, the objectives of this work were (i) to evaluate the Al concentration and identify sites of Al toxicity and its effect on the structure on rice root tips and (ii) to elucidate the adjustments involved in the activities/contents of enzymes/compounds in the roots against Al. For this, two genotypes with contrasting Al tolerance were used. Our results showed that the root length of the tolerant genotype was not affected after Al exposure. We also observed that both the genotypes used strategies to avoid Al uptake, such as the overlap of P and Al in the tolerant genotype and the presence of border cells in the sensitive genotype, which proved inefficient. In the tolerant genotype, other external Al detoxification mechanisms may have contributed to the lower Al concentration in roots and lower fluorescence of the Al-lumogallion complex. Additionally, both genotypes present the activation of key enzymes to decrease oxidative stress, such as CAT, POX, APX, and DHAR, and a more reducing redox environment, mainly due to the increase in the AA/DHA ratio. However, higher total ascorbate, AA, total glutathione, and GSH contents associated with higher SOD, GPX, and GR activities contributed to the reduction of oxidative stress in the tolerant genotype after Al exposure. Furthermore, there was a strong association between the sensitive genotype to Al concentration, O2 •- content, and MDA amount; therefore, these traits can be used as sensitivity indicators in Al studies.

Effects of sulfur poisoning on physicochemical properties and performance of MnO2/AlNi-PILC for toluene catalytic combustion

AlNi pillared clay (AlNi-PILC) was synthesized firstly, and then MnO₂ was supported via wetness impregnation from nitrate precursors. Sulphation was performed by in-situ decomposing ammonium sulfate with different concentrations over MnO₂/AlNi-PILC. Catalysts before and after sulfur poisoning were characterized by XRD, N₂ adsorption/desorption, HRTEM, XPS, H₂-TPR and NH₃-TPD. MnO₂/AlNi-PILC exhibited high catalytic activity, allowing the complete toluene combustion. Structure of the catalyst was obviously damaged after sulfur poisoning. (001) crystal plane strength of AlNi-PILC was decreased significantly. Meanwhile, the specific surface area and pore volume reduced with increase of sulfate concentration. Sulfur species were readily formed on the surface of poisoned catalyst and deposited in the pore structure of AlNi-PILC, which resulted in significant impacts on the structural stability, acidity and the number of active species. These changes were responsible for the decreased catalytic performance.

Metformin use and brain atrophy in nondemented elderly individuals with diabetes

OBJECTIVE

There is a shred of growing evidence demonstrating that diabetic patients are at higher risk of developing Alzheimer's disease compared to the general population. The previous investigation showed the protective effect of metformin for delaying dementia in diabetic patients. However, there are limited data on the effect of metformin on structural changes. This study aims to investigate the effect of metformin on hippocampal and cortical volumes in non-demented diabetic individuals.

METHOD

We entered 157 non-demented diabetic subjects including 89 mild cognitive impairment (MCI), and 68 cognitively healthy individuals from Alzheimer's disease Neuroimaging Initiative (ADNI) which were then categorized as metformin users and non-users. We used the ANCOVA model for measuring the association between metformin use and hippocampal and cortical volumes.

RESULTS

Among 157 subjects with a mean age of 71.8 (±7.7) included in this study, 76 individuals were stratified as metformin users. Results of the univariate model indicate that metformin users had a higher right (p = 0.003) and left parietal lobe volume (p = 0.004). Moreover, the volume of left cingulate was higher in those who used metformin compared to those not used it (p = 0.027). Our results were also significant for the right frontal lobe and indicated that metformin users had higher volume (p = 0.035). There were no significant differences in the hippocampus, occipital, and temporal regions.

CONCLUSION

Our findings showed the protective effects of metformin on brain volumes in non-demented elderly individuals with diabetes. Comparing the groups show strong enough results regarding the lower atrophy in metformin users.

Structural changes in the Russian health care system: do they match European trends?

ВACKGROUND: In the last two decades, health care systems (HCS) in the European countries have faced global challenges and have undergone structural changes with the focus on early disease prevention, strengthening primary care, changing the role of hospitals, etc. Russia has inherited the Semashko model from the USSR with dominance of inpatient care, and has been looking for the ways to improve the structure of service delivery. This paper compares the complex of structural changes in the Russian and the European HCS.

METHODS

We address major developments in four main areas of medical care delivery: preventive activities, primary care, inpatient care, long-term care. Our focus is on the changes in the organizational structure and activities of health care providers, and in their interaction to improve service delivery. To describe the ongoing changes, we use both qualitative characteristics and quantitative indicators. We extracted the relevant data from the national and international databases and reports and calculated secondary estimates. We also used data from our survey of physicians and interviews with top managers in medical care system.

RESULTS

The main trends of structural changes in Russia HCS are similar to the changes in most EU countries. The prevention and the early detection of diseases have developed intensively. The reduction in hospital bed capacity and inpatient care utilization has been accompanied by a decrease in the average length of hospital stay. Russia has followed the European trend of service delivery concentration in hospital-physician complexes, while the increase in the average size of hospitals is even more substantial. However, distinctions in health care delivery organization in Russia are still significant. Changes in primary care are much less pronounced, the system remains hospital centered. Russia lags behind the European leaders in terms of horizontal ties between providers. The reasons for inadequate structural changes are rooted in the governance of service delivery.

CONCLUSION

The structural transformations must be intensified with the focus on strengthening primary care, further integration of care, and development of new organizational structures that mitigate the dependence on inpatient care.

Structure and chemistry of enzymatic active sites that play a role in the switch and conformation mechanism

Enzymes, which are biological molecules, are constructed from polypeptide chains, and these molecules are activated through reaction mechanisms. It is the role of enzymes to speed up chemical reactions that are used to build or break down cell structures. Activation energy is reduced by the enzymes' selective binding of substrates in a protected environment. In enzyme tertiary structures, the active sites are commonly situated in a "cleft," which necessitates the diffusion of substrates and products. The amino acid residues of the active site may be far apart in the primary structure owing to the folding required for tertiary structure. Due to their critical role in substrate binding and attraction, changes in amino acid structure at or near the enzyme's active site usually alter enzyme activity. At the enzyme's active site, or where the chemical reactions occur, the substrate is bound. Enzyme substrates are the primary targets of the enzyme's active site, which is designed to assist in the chemical reaction. This chapter elucidates the summary of structure and chemistry of enzymes, their active site features, charges and role of water in the structures to clarify the biochemistry of the enzymes in the depth of atomic features.

Insight into IgG/IgE binding ability, in vitro digestibility and structural changes of shrimp (Litopenaeus vannamei) soluble extracts with thermal processing

The effects of six kinds of thermal processing on soluble protein recovery, potential allergenicity, in vitro digestibility and structural characteristics of shrimp soluble proteins were evaluated. Obtained results confirmed soluble protein recovery and IgG/IgE reactivity of shrimp soluble extracts were markedly suppressed by various thermal treatments with enhanced digestibility depended on the extent and type of heating applied, which correlated well with the structural alterations and modification. The maximum reduction of IgG/IgE-binding capacity and digestive stability were observed in the autoclaved shrimps because of unfolding of protein and hydrophobic residues exposed. Notably, tropomyosin (TM) and sarcoplasmic calcium-binding protein (SCP) were still IgG/IgE-reactive in various heat-processed shrimps, even higher IgG reactivity were found in heat-treated shrimps TM according to TM antiserum western-blotting and indirect ELISA results. Shrimp TM and SCP maintains its IgE/IgG-binding capacity after various cooking methods, thus most probably initiating allergic sensitization to both raw and cooked shrimps.

Modelling and assessment of plasticizer migration and structure changes in hydrophobic starch-based films

The structures of starch and starch-based materials determine additives migration from material matrix. Propionylated starch derived from waxy, normal, G50 and G80 starch were selected as the matrix, the amylose effect on plasticizer (triacetin) migration as well as structural changes in hydrophobic starch-based films were discussed. The constant (k₁) of first-order rate and initial release rate (V₀) of triacetin migration were consistent with the increment of amylose content. Meanwhile, diffusion model disclosed that Fick's second law was apposite to characterize the short-term migration of triacetin, and larger diffusion coefficient (D) values of short- and long-term migration were also found in films with higher amylose content, indicating that amylose-formed structures were in favor of triacetin migration. In comparison of propionylated amylopectin, Van der Waals's interactions between propionylated amylose and triacetin were easier to be weakened with the migration of triacetin, which promoted the decrease of wavenumber of C-O-C, and enlarged the inter-planner spacing of crystalline structures, promoting the formation of amorphous structures and wrinkles and embossments in films with higher amylose content. This work confirmed that regulating the structures of starch were effective to control the migration behavior of additives from starch-based films.

Effects of apple polyphenols and hydroxypropyl-β-cyclodextrin inclusion complexes on the oxidation of myofibrillar proteins and microstructures in lamb during frozen storage

This study aimed to evaluate the effect of inclusion complexes (ICs) on the oxidative stability of myofibrillar proteins (MPs) and microstructures in lamb during frozen storage. The inclusion process between apple polyphenols (APs) and hydroxypropyl-β-cyclodextrin (HP-β-CD) was verified using Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and the antioxidant activity of APs. Results showed that the sensitivity of MPs to oxidation improved after 40 weeks. The ICs (0.2-1.6 mg/mL) significantly reduced the carbonyl content, particle size aggregation, protein degradation, fluorescence quenching effect, and decreased the α-helix contents loss of MPs. Additionally, the changes in protein oxidation showed a correlation with the microstructure of muscles, and the addition of 1.6 mg/mL IC remarkably improved the structure of muscle tissues while that of 3.2 mg/mL IC was detrimental to the structural properties. Overall, the exertion of antioxidant activity significantly influenced the cryoprotective effect of ICs on frozen lamb meat.

Controlling plasticizer migration based on crystal structure and micromorphology in propionylated starch-based food packaging nanocomposites

Migration of additives is an important issue for proper application in food packaging. In this work, propionylated waxy and normal starch-based nanocomposites (PW-N and PN-N) with two different amylopectin content were immersed in distilled water, and structural changes and migration mechanism of plasticizer (triacetin) were discussed in detail. Results showed that when immersion time was prolonged to 150 h, small crystals of PN-N disappeared, and amorphous structures formed gradually in PW-N and PN-N. Exfoliated structures still remained in PW-N with prolonged immersion time, while exfoliated structures gradually formed from intercalated ones in PN-N, and the peak representing d001 (d-spacing) at q = 1.70 nm^-1 faded. The migration mechanism of triacetin obeyed the first-order kinetic model and Fick's law; furthermore, in comparison with PW-N, PN-N showed a larger diffusion coefficient (D₂ = 12.13 μm²·h^-1). These results contributed to expanding the application of starch-based nanocomposites in future environmentally friendly food packaging.

Exploration of physicochemical properties and molecular interactions between cellulose and high-amylose cornstarch during extrusion processing

Incorporating fiber at high levels (>10%) into direct-expanded products with acceptable texture is challenging. Fundamental explanations for the interaction of starch and fiber and the cause of expansion reduction need further understanding for the effective incorporation of fiber into expanded products. This study aims to explain how cellulose content impacts the physicochemical properties of starch-based extrudates and the long-range and short-range molecular changes of starch. Mixtures of cornstarch (50% amylose) and cellulose were extruded using a co-rotating twin-screw extruder. Thermal and pasting properties of the raw mixtures were evaluated, and the physicochemical properties and microstructure of extrudates were determined. Long-range and short-range molecular changes of starch-cellulose mixtures before and after extrusion were observed by X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. The expansion ratio of extrudates reduced significantly as the cellulose content increased and had a strong negative correlation with crystallinity. Cell structures of starch-cellulose extrudates had a smaller and more uniform pore size but possessing a more ruptured matrix. FTIR spectra suggested that there was no covalent bonding interaction between starch and fiber after extrusion. Extrusion reduced the overall crystallinity compared to the raw mixtures. XRD showed that the crystallinity of the starch-cellulose extrudates increased as the cellulose content increased, and the XRD peaks representing cellulose remained unchanged. Cellulose could interfere with starch chain reassociation through intermolecular hydrogen bonding during the expansion process. Phase separation of starch and cellulose is likely to occur at high cellulose content, which could be another reason for the reduced expansion.

Effect of non-covalent binding of phenolic derivatives with scallop (Patinopecten yessoensis) gonad protein isolates on protein structure and in vitro digestion characteristics

The present study was aimed to investigate the effects of non-covalent interactions between scallop gonad protein isolates (SGPIs) and different concentrations (20, 120 and 240 μmol/g, protein basis) of four phenolic compounds, such as (-)-epigallocatechin gallate (EGCG), epicatechin 3-gallate (ECG), epigallocatechin (EGC), and catechin (C), regarding the structural and functional properties of the complex. Total sulfhydryl and surface hydrophobicity in SGPIs decreased by nearly 72% and 65% with 240 μmol/g EGCG, similar but less appreciable changes were produced by EGC, ECG and C. Fluorescence quenching and thermodynamic parameters suggested that hydrogen bond and van der Waals dominated the interaction process between SGPIs and EGCG, and the interaction was further studied by molecular docking. Moreover, EGCG-treated SGPIs digests exerted higher ABTS+• scavenging activity than that of ECG and EGC-treated SGPIs. These findings are helpful to reveal the binding mechanism of phenolics and SGPIs, and provide a theoretical basis for the application of SGPIs-phenolic complexes as functional food additives.

Understanding the deterioration of fresh brown rice noodles from the macro and micro perspectives

The microbial compositions, quality characteristics, and structural changes in fresh brown rice noodles (FBRN) during storage were investigated. Total plate count and mold and yeast counts increased while the pH decreased during storage. Metagenomic sequencing revealed that the microbial composition of FBRN changed throughout storage. A comprehensive investigation of the variation in lipid content demonstrated that hydrolytic rancidity was responsible for lipid deterioration. LF-NMR showed an increase in the proportion of bound water and a decrease in the proportion of free water in FBRN. Moreover, significant changes in edible qualities were observed. The cooking loss increased three-fold and noodles hardness reduced by approximately 23%. Further, the high initial aldehyde content of FBRN diminished almost completely, while that of alcohols and esters increased, leading to significant flavor deterioration. The correlation and factor analysis suggested that the TPC and MY counts could be used as key indicators of FBRN deterioration.

Conformational dynamics in interleukin 17A and 17F functional complexes is a key determinant of receptor A affinity and specificity

The proinflammatory cytokines IL-17A and IL-17F have been identified as key drivers of a range of human inflammatory diseases, such as psoriasis, which has led to several therapeutic antibodies targeted at IL-17A. The two cytokines have been shown to tightly associate as functional homo and hetero dimers, which induce signalling via the formation of a cell surface signalling complex with a single copy of both IL-17RA and IL-17RC. Striking differences in affinity have been observed for IL-17RA binding to IL-17AA, IL-17AF and IL-17FF, however, the functional significance and molecular basis for this has remained unclear. We have obtained comprehensive backbone NMR assignments for full length IL-17AA (79%), IL-17AF (93%) and IL-17FF (89%), which show that the dimers adopt almost identical backbone topologies in solution to those observed in reported crystal structures. Analysis of the line widths and intensities of assigned backbone amide NMR signals has revealed striking differences in the conformational plasticity and dynamics of IL-17AA compared to both IL-17AF and IL-17FF. Our NMR data indicate that a number of regions of IL-17AA are interconverting between at least two distinct conformations on a relatively slow timescale. Such conformational heterogeneity has previously been shown to play an important role in the formation of many high affinity protein-protein complexes. The locations of the affected IL-17AA residues essentially coincides with the regions of both IL-17A and IL-17F previously shown to undergo significant structural changes on binding to IL-17RA. Substantially less conformational exchange was revealed by the NMR data for IL-17FF and IL-17AF. We propose that the markedly different conformational dynamic properties of the distinct functional IL-17 dimers plays a key role in determining their affinities for IL-17RA, with the more dynamic and plastic nature of IL-17AA contributing to the significantly tighter affinity observed for binding to IL-17RA. In contrast, the dynamic properties are expected to have little influence on the affinity of IL-17 dimers for IL-17RC, which has recently been shown to induce only small structural changes in IL-17FF upon binding.

Effects of age differences in memory formation on neural mechanisms of consolidation and retrieval

Episodic memory decline is a hallmark of cognitive aging and a multifaceted phenomenon. We review studies that target age differences across different memory processing stages, i.e., from encoding to retrieval. The available evidence suggests that age differences during memory formation may affect the quality of memory representations in an age-graded manner with downstream consequences for later processing stages. We argue that low memory quality in combination with age-related neural decline of key regions of the episodic memory network puts older adults in a double jeopardy situation that finally results in broader memory impairments in older compared to younger adults.

Effects of conserved Arg20, Glu74 and Asp77 on the structure and function of a tau class glutathione S-transferase in rice

The relative position of domains is critical for enzymatic properties of tau class glutathione S-transferases, and altering the position of linker far away from the active center affects catalytic property. Glutathione S-transferases (GSTs) are a family of phase II detoxification enzymes whose main function is to improve plant resistance to stresses. To understand the structural effects of tau class GSTs on their function, using OsGSTU17 as an example, we predicted the residues involved in the interactions between its domains and linker region. We further detected the structural changes in mutants and the corresponding changes in terms of substrate activity and kinetic parameters. Four pairs of residues, including Ala14 and Trp165, Arg20 and Tyr154, Glu74 and Arg98, Asp77 and Met87, forming hydrogen bonds and salt bridges were found to play important roles in maintaining the relative position between the domains and linker region inside the protein. The hydrogen bond between Trp165 and Ala14 affected the structural stability has been demonstrated in our previous study. The mutant R20A lost almost all catalytic activity. Interestingly, the mutant E74A exhibited a significant decrease in activity towards 7-chloro-4-nitrobenzo-2-oxa-1, 3-diazole, 1-chloro-2, 4-dinitrobenzene and 4-nitrobenzyl chloride, while its activity towards substrate cumene hydroperoxide remained unchanged. Compared with other mutants, the mutant D77A exhibited decreased affinity to its substrates and increased activity towards 1-chloro-2, 4-dinitrobenzene and cumene hydroperoxide, but its thermodynamic stability did not change significantly. The relative position of individual domain was critical for enzymatic properties, and the linker which is far away from the active site could change the enzymatic properties of GSTs via altering the relative position of the individual domain. Our results provide insights into the relationship between structure and function of tau class GSTs.

Ultrasonic treatment increased functional properties and in vitro digestion of actomyosin complex during meat storage

We investigated the effects of ultrasonic treatment (400 W, 20 kHz, 45.52 W/L) and storage time (0 d, 3 d, 7 d and 10 d) on functional properties, structural changes and in vitro digestion of actomyosin complex isolated from vacuum-packed pork. As storage time increased, turbidity, surface hydrophobicity, active sulfhydryl and total sulfhydryl of actomyosin complex increased, while protein solubility decreased. Ultrasonic treatment increased surface hydrophobicity, protein solubility and active sulfhydryl content but decreased turbidity and total sulfhydryl content compared with the control. Ultrasonic treatment caused a reduction in α-helix content on 0 day and the fluorescence intensity of tryptophan and tyrosine residues. It increased pancreatin digestibility of actomyosin complex and the number of peptides of smaller than 1 kDa. However, it decreased the number of peptides. The findings provide a new insight into the application of appropriate ultrasonic treatment to promote meat digestibility.

Modulating the in vitro digestibility of chemically modified starch ingredient by a non-thermal processing technology of ultrasonic treatment

Chemically modified starch (RS4) was commercially available as a food ingredient, however, there was a lack of knowledge on how ultrasonic treatment (non-thermal technology) modulated the enzymatic resistance of RS4. In this study, structural change of RS4 during ultrasonic treatment and its resulting digestibility was investigated. Results from scanning electron microscopy, particle size analysis, chemical composition analysis, X-ray diffraction, differential scanning calorimetry, and Fourier transform infrared spectroscopy showed that ultrasonic treatment remained the granule morphology, increased the apparent amylose content, reduced the particle size, destroyed the crystalline structure, decreased the helical orders, but enhanced the short-range molecular orders of ultrasonic-processed RS4. In vitro digestibility analysis showed that the total content of rapidly digestible starch and slowly digestible starch was increased, whereas the content of resistant starch was decreased. Overall, ultrasonic treatment substantially reduced the enzymatic resistance of RS4, indicating that RS4 was not stability against the non-thermal processing technology of ultrasonic treatment.

Structural and operational redesigning of patient-centered ambulatory care pharmacy services and its effectiveness during the COVID-19 pandemic

BACKGROUND

The newly emerged coronavirus pandemic (COVID-19) has collapsed the entire global health care system. Due to these settings, a lot of strategic changes are adopted by healthcare facilities to ensure continuity in patient-centered services.

OBJECTIVE

This study aims to evaluate the effectiveness of structural and operational changes made in ambulatory care pharmacy services during the COVID-19 pandemic.

METHODS

A retrospective comparative study was conducted to evaluate the impact and effectiveness of patient-centered interventions and consequent access to medication management care within Johns Hopkins Aramco Health Care ambulatory care pharmacy services during the COVID-19 pandemic by comparing patient-centered key performance indicators before and during COVID-19 pandemic for a total of 4 months.

RESULTS

As a result of the structural and operational changes made in patient-centered ambulatory care pharmacy services during the COVID-19 pandemic, a 48% prescriptions requests and 90% prescriptions fills are increased through online health portal application. A three-fold increase in the pharmacy call center utilization resulted in around 10% abandoned calls. In the number of physical visits to ambulatory care pharmacies, a 37% reduction was also noted. The decrease in staff schedule efficiency and an increase in average prescription waiting time were also noticed. The prescription collection through remote area pick up locations, and medication home delivery services were successful during COVID-19 pandemic as supported by statistical data.

CONCLUSION

The access to ambulatory care pharmacy services during COVID-19 pandemic has been successfully maintained via medication home delivery, remote area pickup locations, pharmacy call-center consultations and refill requests, online health portal application services, and other measures, while reducing the number of physical visits to the JHAH hospital/clinic to ensure compliance with infection control and prevention measures.

Structural Changes and Quality of Women's Labour in India

The primary objective of this paper is to look at the trends and pattern of changes in women's employment structure over years (1983-2018) consequent upon the structural changes in the Indian economy. It also attempts to analyse the quality of women's labour in terms of select parameters. The study finds that there is neither quantitative nor qualitative improvement in women's employment over time on account of structural changes in the economy. There is no 'U' curve of female labour supply in response to GDP growth and expansion of female literacy, implying that economic growth has not generated adequate jobs for women. It also signifies that women's entry or exit of labour market is influenced by non-economic factors also. There is no major occupational diversification in women's employment despite structural shift of the economy from primary to tertiary sector. Agriculture is still the leading sector in women's employment. The study further reveals that the quality of women's labour is poor. Overcrowding of workforce in agriculture largely as wage labourers, lower earnings, poor literacy levels, large-scale informal employment and most self-employment in the form of unpaid work are indications of women's disadvantaged position in the labour market.

Investigation of the effect of oxidation on the structure of β-lactoglobulin by high resolution mass spectrometry

In this work, high-resolution mass spectrometry was used to identify the oxidation sites and forms of β-lactoglobulin (β-Lg) induced by hydrogen peroxide with 1.5% concentration, and the influence of oxidation sites on the structure of β-Lg was discussed from the molecular level. Twelve kinds of oxidation products and 36 oxidation sites were identified, including sulfoxidation in sulfur-containing amino acid residue, hydroxylation in aromatic group residue, deamination in amino-containing amino acid etc. The destruction of hydrogen bonds and disulfide bonds in β-Lg caused by oxidation is the main factor causing its structural changes, which were manifested in the decrease of β-sheet component and increase of β-turns and random coil contents, intrinsic fluorescence intensity and surface hydrophobicity. In addition, several peptides as potential oxidative markers were found to be capable of monitoring the degree of oxidation of β-Lg. In short, this work provided insights into structural changes of β-Lg by oxidation.

In vitro efficacy of Elephantorrhiza elephantina root extracts against adult Paramphistomum cervi in goats

Elephantorrhiza elephantina is a medicinally important plant whose roots are used to control gastrointestinal parasites in goats. The use of plant-based anthelmintics as potential alternatives to synthetic anthelmintics in controlling gastrointestinal worms in ruminants is a promising area of research. The study was carried out to ascertain the efficacy of E. elephantina in controlling goat trematodes. Standard procedures were used to quantify the phytochemicals in the water, ethanol and methanol root extracts of E. elephantina. The quantitative phytochemical analysis revealed that alkaloids (93.24 ± 1.68%), condensed tannins (450.52 ± 0.15 mg CE/g), flavonoids (803.93 ± 0.13 mg QE/g), phenols (476.11 ± 0.37 mg GAE/g) and saponins (83.28 ± 1.72%) were present in E. elephantina root extracts. Paramphistomum cervi adult worms recovered from the rumen of freshly slaughtered goats were used. In vitro screening of ethanol, methanol and water extracts of E. elephantina for potential anthelmintic activity against adult P. cervi worm motility showed time and dose-dependent significant effects. Ethanol extracts showed a highly significant (P < 0.05) inhibition of motility (86.67 and 96.67%) at concentrations 7.5 and 15 mg/mL respectively, after 12 h of treatment, while methanol and water extracts exhibited a significant (P < 0.05) inhibition of motility (96.67 and 66.67% respectively) at concentration of 15 mg/mL 16 h post-exposure. Our findings confirm the efficacy of E. elephantina in controlling goat trematodes.

Treatment of retinopathy of prematurity (ROP) outside International Classification of ROP (ICROP) guidelines

AIM

To evaluate the incidence and clinical indications for which eyes were treated for retinopathy of prematurity (ROP) outside the guidelines set by International Classification of ROP (ICROP).

METHODS

Medical records of the patients treated at a single tertiary care ophthalmology hospital for ROP from January 2016 to December 2019 were retrospectively analysed to evaluate the indications for which they were treated.

RESULTS

Out of 241 eyes, 33 eyes (13.7%) were treated outside the guidelines. The reasons for the treatment outside the guidelines were structural changes (n = 24, 72.7%), persistent stage 3 ROP that did not show any sign of regression for 6 weeks (n = 7, 21.2%) and active ROP with fellow eye being treated (n = 2, 6.1%). The recorded specific structural changes were tangential traction with temporal vessel straightening concerning for macular distortion and ectopia (n = 5, 15.2%), and stage 3 neovascularisation or ridge with anteroposterior traction with risk of progression to stage 4 disease (n = 19, 57.6%). Pre-plus disease was present in 11 eyes (33.3%).After the treatment, ROP stages regressed and retinal vessels grew either until the ora or at least into zone III in all the treated eyes. None of the eyes showed worsening of structural changes after treatment. The mean follow-up of the patients was 12.4 ± 11.7 months.

CONCLUSION

Experts occasionally recommend treatment in eyes with disease milder than type 1 ROP. This study may help paediatric retinal practitioners in decision-making in borderline cases.

Evaluation of the applicability of existing (Q)SAR models for predicting the genotoxicity of pesticides and similarity analysis related with genotoxicity of pesticides for facilitating of grouping and read across: An EFSA funded project

To facilitate the practical implementation of the guidance on the residue definition for dietary risk assessment, EFSA has organized an evaluation of applicability of existing in silico models for predicting the genotoxicity of pesticides and their metabolites, including literature survey, application of QSARs and development of Read Across methodologies. This paper summarizes the main results. For the Ames test, all (Q)SAR models generated statistically significant predictions, comparable with the experimental variability of the test. The reliability of the models for other assays/endpoints appears to be still far from optimality. Two new Read Across approaches were evaluated: Read Across was largely successful for predicting the Ames test results, but less for in vitro Chromosomal Aberrations. The worse results for non-Ames endpoints may be attributable to the several revisions of experimental protocols and evaluation criteria of results, that have made the databases qualitatively non-homogeneous and poorly suitable for modeling. Last, Parent/Metabolite structural differences (besides known Structural Alerts) that may, or may not cause changes in the Ames mutagenicity were identified and catalogued. The findings from this work are suitable for being integrated into Weight-of-Evidence and Tiered evaluation schemes. Areas needing further developments are pointed out.

Structural changes and band gap tunability with incorporation of n-butylammonium iodide in perovskite thin film

The current work presents structural change and band gap tunability using hybrid organic-inorganic perovskite with the incorporation of long chain ammonium halide. Thin films of MAPbI3 with different ratio of n-butylammonium iodide (BAI) have been successfully deposited on the substrate using a single step coating technique. X-ray diffraction scans revealed the transition of the 3D structure of MAPbI3 to quasi-2D perovskite structure when BAI loading increase with a crystallite size range approximately 16 nm. This structural changeis reflected in the band gap as it increased from 1.59 eV for bulk crystal MAPbI3 to 2.13 eV for BAI and MAPbI3 ratio of 1:1. Correspondingly, photoluminescence measurement showed a blue shift in perovskite emission due to the transition of 3D to 2D layered structure perovskite. Raman spectra confirm that all fabricated films are of pristine quality and no corresponding degradation peaks of PbI2 is observed. These characteristics are important to address the single step deposition method of hybrid perovskite for perovskite solar cells application.

Temperature dependence Raman spectroscopy and DFT calculations of Bi2(MoO4)3

This work reports a theoretical and experimental study on the electronic and vibrational properties of Bi₂(MoO₄)₃. First-principle calculations were applied to increase the understanding on the properties of the chemical composition through the energy bands. The conduction band minimum (CBM) is found at the high symmetric Γ-point, while the valence-band maximum (VBM) is located between the Z and the Γ-points. Therefore, these facts confirm that the Bi₂(MoO₄)₃ crystal is a semiconductor compound with an indirect band-gap of about 2.1 eV. Moreover, lattice dynamic properties were calculated using density functional perturbation theory (DFPT) in order to assign the experimental Raman bands. In addition, we performed temperature-dependent Raman spectroscopic studies in the Bi₂(MoO₄)₃ crystals to obtain information on structural changes induced by effects of the temperature change. From the changes observed in the Raman spectra phase transitions at ∼ 668 and 833 K were inferred, with the last one possibly related to the disorder due to the heating process.

The Arabidopsis cryptochrome 2 I404F mutant is hypersensitive and shows flavin reduction even in the absence of light

The cryptochrome photoreceptor mutant cry2I404F exhibits hyperactivity in the dark, hypersensitivity in different light conditions, and in contrast to the wild-type protein, its flavin chromophore is reducible even in the absence of light. Plant cryptochromes (cry) are blue-light photoreceptors involved in multiple signaling pathways and various photomorphogenic responses. One biologically hyperactive mutant of a plant cryptochrome that was previously characterized is Arabidopsis cry1L407F (Exner et al. in Plant Physiol 154:1633-1645, 2010). Protein sequence alignments of different cryptochromes revealed that L407 in cry1 corresponds to I404 in cry2. Point mutation of Ile to Phe in cry2 in this position created a novel mutant. The present study provided a baseline data on the elucidation of the properties of cry2I404F. This mutant was still able to bind ATP-triggering conformational changes, as confirmed by partial tryptic digestion and thermo-FAD assays. Surprisingly, the FAD cofactor of cry2I404F was reduced by the addition of reductant even in the absence of light. In vivo, cry2I404F exhibited a cop phenotype in the dark and hypersensitivity to various light conditions compared to cry2 wild type. Overall, these data suggest that the hypersensitivity to red and blue light and hyperactivity of this novel mutant in the dark can be mostly accounted to structural alterations brought forth by the Ile to Phe mutation at position 404 that allows reduction of the flavin chromophore even in the absence of light.

Mitigation of isoquercitrin on β-lactoglobulin glycation: Insight into the mechanisms by mass spectrometry and interaction analysis

Formation of advanced glycation end products (AGEs) on foods imposes threats to human health after intaking. This research firstly evaluated the inhibition of isoquercitrin on β-lactoglobulin (β-Lg) glycation, the mechanisms were elucidated by fluorescence spectroscopy, Orbitrap MSⁿ and molecular docking. Fluorescence spectra indicated that isoquercitrin effectively alleviated the formation of AGEs, it could stabilize the conformation structure of glycated β-Lg (G-β-Lg), change the micro-environment in the vicinity of chromophores. SDS-PAGE analysis revealed the suppressed cross-linking of G-β-Lg induced by isoquercitrin. The number of glycation site detected on G-β-Lg was reduced from ten to eight after the addition of isoquercitrin, and the relative glycation degree of substitution of per site (RGDSP) of most glycation sites were also greatly decreased. As indicated by intermolecular interaction, isoquercitrin quenched the fluorescence of β-Lg via a static mechanism, and their combination is an endothermic processing mainly derived by hydrophobic interaction, hydrogen bonds, and van der Waals forces. Isoquercitrin interacted with β-Lg to form an equimolar complex, and one hydrogen bond was formed between isoquercitrin and Lys69 (4.96 Å). Above results proved that isoquercitrin can be a promising anti-glycation agent used in food system to prevent the formation of harmful glycation products.

Adsorption behaviors of Cu2+, Zn2+ and Cd2+ onto proteins, humic acid, and polysaccharides extracted from sludge EPS: Sorption properties and mechanisms

To clarify the adsorption behaviors of typical heavy metals onto sludge extracellular polymeric substances (EPS), the adsorption capacities and mechanisms, as well as the contributions of the different EPS components (proteins, humic acids and polysaccharides), to the adsorption of Zn²⁺, Cu²⁺ and Cd²⁺ were separately explored. Overall, proteins exhibited a relatively high adsorption capacity for the three metals ions, followed by humic acid, whereas least for polysaccharides. The adsorption of Cu²⁺ and Cd²⁺ onto proteins, humic acid and polysaccharides fit well to the Freundlich isotherm, whereas Langmuir model was the best fit for Zn²⁺ bindings onto polysaccharides/humic acid. The binding of Cu²⁺, Zn²⁺ and Cd²⁺ onto the three EPS components was exothermically favorable, and significant electrostatic interactions were observed for the heavy metals sorption onto humic acid and proteins. In addition, the effect of metal ions sorption on the spectrum of the proteins, polysaccharides and humic acid was also explored.

Polyvinyl alcohol degradation by Bacillus cereus RA23 from oil sludge sample

A novel polyvinyl alcohol (PVA)-degrading strain Bacillus cereus RA23 was isolated from an oil sludge sample and environmental factors affecting its PVA degradation efficiency were optimized in detail. Inorganic nitrogen source, ammonium chloride (NH4Cl), was found to be the best nitrogen source and enhanced the PVA degradation rate greatly. The optimal medium for PVA biodegradation consisted of (g/L) PVA 1, NH4Cl 1, K2HPO4 1.6, MgSO4·7H2O 0.05, FeSO4·6H2O 0.02, CaCl2 0.05, NaCl 0.02. The optimal temperature and pH for PVA biodegradation by strain RA23 was 28 °C and 7.0, respectively, and 85% of 0.1% PVA was degraded after 5 days under these conditions. FTIR studies showed that the carboxylic acids (possibly including aldehyde or ketone) could be the intermediate product of PVA biodegradation. The investigation of strain RA23 for PVA degradation will provide important information to facilitate the removal of wastewater pollution in industrial zones.

Crystalline morphology of thermoplastic starch/talc nanocomposites induced by thermal processing

A structural study about the changes induced by plasticization of native corn starch was carried out in this work. The influence of talc nanoparticles presence during starch thermal processing was also evaluated. Macroscopic observation of the granules appearance evolution during melt-mixing and thermo-compression was supported by a theoretical description related to these processing methods. Melt-mixing induced a polymorphic transformation from A- to V_h-type and a reduction in the degree of crystallinity. Homogenous appearance of the plasticized starch was in accordance to the disruption of granules integrity, evidenced by SEM. This observation agreed to the distinctive XRD pattern of plasticized starch from unprocessed granules. Talc incorporation did not require the adjustment of processing parameters in order to obtain a homogenous thermoplastic material, with an adequate particles distribution within the matrix. Regardless talc presence, plasticized starch presented a V_h-type crystalline structure. Thermo-compression led to particles alignment promoted by talc laminar morphology.

Mechanical and structural properties of human aortic and pulmonary allografts do not deteriorate in the first 10 years of cryopreservation and storage in nitrogen

The aortic and pulmonary allograft heart valves (AHV) are used in the cardiac surgery for replacing the impaired semilunar valves. They are harvested from donor hearts and cryostored in tissue banks. The expiration period was set to 5 years arbitrarily. We hypothesized that their mechanical and structural properties do not deteriorate after this period. A total of 64 human AHV (31 aortic and 33 pulmonary) of different length of cryopreservation (fresh, 0-5, 5-10, over 10 years) were sampled to different tissue strips (artery, leaflet, ventriculo-arterial junction) and tested by tensile test with loading velocity 10 mm/min until tissue rupture. Neighbouring regions of tissue were processed histologically and evaluated for elastin and collagen area fraction. The results were evaluated statistically. In aortic AHV, the physical deformation response of wall samples to stress did not changed significantly neither during the process of cryopreservation nor during the first 10 years of storage. In pulmonary AHV, the ultimate strain dropped after 5 years of cryopreservation indicating that pulmonary artery was significantly less deformable at the time of rupture. On the other hand, the ultimate stress was equal during the first 10 years of cryostorage. The changes in collagen and elastin amount in the tissue samples were not associated with mechanical impairment. Neither elasticity, stiffness and solidity nor morphology of aortic and pulmonary AHV did not change reasonably with cryopreservation and in the first 10 years of cryostorage. This evidence suggests that the expiration period might be extended in the future.

Designing and construction of novel variants of Chondroitinase ABC I to reduce aggregation rate

Chondroitinase ABC I (cABC I) can degrade inhibitory molecules for axon regrowth at the site of damage after spinal cord injury (SCI). One of the main problems in the practical application is the possibility of structural changes that lead to the inactivation of the enzyme. In current work, three variants of cABC I was designed and constructed by manipulation of a short helix conformation (Gln⁶⁷⁸-Leu⁶⁷⁹-Ser⁶⁸⁰-Gln⁶⁸¹); where Gln residues were converted to Glu. According to the enzyme kinetics studies, the catalytic efficiency of the Q681E and double mutant (Q678E/Q681E) increases in comparison with WT enzyme; while that of Q678E decreases. It was also shown that the rate of the inactivation of the enzyme variants over time is greater in WT and Q678E variants than that of the Q681E and double mutant. Negative values of entropy change of thermal inactivation measurements; demonstrate that inactivation of the WT and Q678E variants are mainly originated from aggregation. These observations can be explained by considering the repulsive electrostatic interaction between enzyme molecules that prevents protein aggregation over time. It is concluded that increasing the solubility of the Q681E and double mutant via favorable interactions of surface-exposed charged residues with dipole momentum of water molecules accompanied by the presence of intermolecular repulsive electrostatic interaction leads to decreasing the rate of aggregation in both long-term storage and heat-induced structural changes.

Mechanical and structural properties of human aortic and pulmonary allografts do not deteriorate in the first 10 years of cryopreservation and storage in nitrogen

The aortic and pulmonary allograft heart valves (AHV) are used in the cardiac surgery for replacing the impaired semilunar valves. They are harvested from donor hearts and cryostored in tissue banks. The expiration period was set to 5 years arbitrarily. We hypothesized that their mechanical and structural properties do not deteriorate after this period. A total of 64 human AHV (31 aortic and 33 pulmonary) of different length of cryopreservation (fresh, 0-5, 5-10, over 10 years) were sampled to different tissue strips (artery, leaflet, ventriculo-arterial junction) and tested by tensile test with loading velocity 10 mm/min until tissue rupture. Neighbouring regions of tissue were processed histologically and evaluated for elastin and collagen area fraction. The results were evaluated statistically. In aortic AHV, the physical deformation response of wall samples to stress did not changed significantly neither during the process of cryopreservation nor during the first 10 years of storage. In pulmonary AHV, the ultimate strain dropped after 5 years of cryopreservation indicating that pulmonary artery was significantly less deformable at the time of rupture. On the other hand, the ultimate stress was equal during the first 10 years of cryostorage. The changes in collagen and elastin amount in the tissue samples were not associated with mechanical impairment. Neither elasticity, stiffness and solidity nor morphology of aortic and pulmonary AHV did not change reasonably with cryopreservation and in the first 10 years of cryostorage. This evidence suggests that the expiration period might be extended in the future.

Low-pH induced structural changes, allergenicity and in vitro digestibility of lectin from black turtle bean (Phaseolus vulgaris L.)

Lectin was incubated in corresponding acidic buffers (pH 1.0-3.5) for a certain period (0.5, 1, 2, 4, 8, 12 and 24 h) at 25 °C. Low-pH induced changes in structure, allergenicity and in vitro digestibility of lectin from black turtle bean (Phaseolus vulgaris L.) were investigated in the present study. Results indicated that the alteration in structure was a progressive unfolding process mainly depending on pH environment, and the treated lectin attained a stable state at 8 h. Electrophoretic, dynamic light scattering (DLS) and size exclusion chromatography (SEC) analyses suggested that lectin monomers appeared in the solutions of pH < 2.0. Differential scanning calorimetry (DSC) confirmed that thermal stability of lectin weakened in low pH environments. Furthermore, ELISA and in vitro digestion assay showed allergenicity and digestibility significantly decreased with the structural alterations. These results showed low-pH treatments have great potential to reduce the damage of legumes protein consumption.

Protein G selects two binding sites for carbon nanotube with dissimilar behavior; a molecular dynamics study

BACKGROUND

Study of nanostructure-protein interaction for development of various types of nano-devices is very essential. Among carbon nanostructures, carbon nanotube (CNT) provides a suitable platform for functionalization by proteins. Previous studies have confirmed that the CNT induces changes in the protein structure.

METHODS

Molecular dynamics (MD) simulation study was employed to illustrate the changes occurring in the protein G (PGB) in the presence of a CNT. In order to predict the PGB surface patches for the CNT, Autodock tools were utilized.

RESULTS

Docking results indicate the presence of two different surface patches with diverse amino acids: the dominant polar residues in the first (PGB-CNT1) and the aromatic residues in the second (PGB-CNT2) surface patch. Displacement of amino acids in the PGB-CNT2 complex occurred during the simulation and it caused an increase in its stability at the end of simulation. The amino acids' displacements diminished the PGB α-helix structure by breakage of hydrogen bonds and generated more transient structures. Principal component analysis determined that the interaction of the CNT with the second surface patch of the PGB raised the extent and modes of the PGB motions. In contrast, insignificant structural changes induced in the PGB while the CNT bonded through the first surface patch.

CONCLUSION

Even though neither of the PGB-CNT complexes could prevent structural changes in the PGB, development of the PGB-CNT1 complex induce slight structural changes in its fragment of crystallizable receptor (FCR). Dissimilar structural changes induced in the PGB-CNT complexes are possibly related to various characteristics of the PGB binding sites.

Improvement of kinetic properties and thermostability of recombinant Lepidium draba peroxidase (LDP) upon exposed to osmolytes

In this study, effects of different concentrations of glycine and D-sorbitol were analyzed on the activity and thermostability of recombinant Lepidium draba peroxidase (LDP). Based on the results, activity of the enzyme increased in the presence of various concentrations of these osmolytes. Maximum activity was detected for the enzyme in the presence of 300 mM glycine and 600 mM sorbitol. In presence of the aforementioned doses of osmolytes, enzyme affinity for substrate (3,3',5,5'-tetramethylbenzidine and H₂O₂) and V_max increased. According to the results, enzyme stability improved against temperature and H₂O₂. Furthermore, structural changes of the enzyme upon exposure to the osmolytes were revealed by the use of far-UV circular dichroism and fluorescence methods. The results showed, whereas the secondary structure of the enzyme was not significantly changed upon exposed to the osmolytes, the fluorescence studies revealed microenvironment of the aromatic residues dramatically affected by them. Overall, it may be speculated, structural changes of the enzyme upon exposed to the osmolytes, lead to the improvement of its kinetic properties and stability that can be benefit for using of it in in vitro applications.