Flavour compounds affect protein structure: The effect of methyl anthranilate on bovine serum albumin conformation.

This study aims to understand possible effects of flavour compounds on the structure and conformation of endogenous proteins. Using methyl anthranilate (a grape flavour compound added to drinks, confectionery, and vape-liquids) and bovine serum albumin (BSA, a model serum protein) we designed experimental investigations using analytical ultracentrifugation, size exclusion chromatography small angle X-ray scattering, and fluorescence spectroscopy to reveal that methyl anthranilate spontaneously binds to BSA (ΔG°, ca. -21 KJ mol-1) which induces a conformational compactness (ca. 10 %) in the monomer structure. Complementary molecular modelling and dynamics simulations suggested the binding occurs at Sudlow II of BSA via establishment of hydrogen bonds with arginine409, lysine413 and serine488 leading to an increased conformational order in domains IA, IIB and IIIB. This work aims to set the foundation for future research on flavour-protein interactions and offer new sets of opportunities for understanding the effects of small compounds on protein structure.

Biochanin A impedes STAT3 activation by upregulating p38δ MAPK phosphorylation in IL-6-stimulated macrophages.

OBJECTIVE: IL-6-induced STAT3 activation is associated with various chronic inflammatory diseases. In this study, we investigated the anti-STAT3 mechanism of the dietary polyphenol, biochanin A (BCA), in IL-6-treated macrophages. METHODS: The effect of BCA on STAT3 and p38 MAPK was analyzed by immunoblot. The localization of both these transcription factors was determined by immunofluorescence and fractionation studies. The impact on DNA-binding activity of STAT3 was studied by luciferase assay. To understand which of the isoforms of p38 MAPK was responsible for BCA-mediated regulation of STAT3, overexpression of the proteins, site-directed mutagenesis, pull-down assays and computational analysis were performed. Finally, adhesion-migration assays and semi-quantitative PCR were employed to understand the biological effects of BCA-mediated regulation of STAT3. RESULTS: BCA prevented STAT3 phosphorylation (Tyr705) and increased p38 MAPK phosphorylation (Thr180/Tyr182) in IL-6-stimulated differentiated macrophages. This opposing modulatory effect of BCA was not observed in cells treated with other stress-inducing stimuli that activate p38 MAPK. BCA abrogated IL-6-induced nuclear translocation of phospho-STAT3 and its transcriptional activity, while increasing the cellular abundance of phospho-p38 MAPK. BCA-induced phosphorylation of p38δ, but not α, ß, or γ was responsible for impeding IL-6-induced STAT3 phosphorylation. Interestingly, interaction with phospho-p38δ masked the Tyr705 residue of STAT3, preventing its phosphorylation. BCA significantly reduced STAT3-dependent expression of icam-1 and mcp-1 diminishing IL-6-mediated monocyte adhesion and migration. CONCLUSION: This differential regulation of STAT3 and p38 MAPK in macrophages establishes a novel anti-inflammatory mechanism of BCA which could be important for the prevention of IL-6-associated chronic inflammatory diseases.

Macromolecular design of folic acid functionalized amylopectin-albumin core-shell nanogels for improved physiological stability and colon cancer cell targeted delivery of curcumin.

Nanogels have potential for encapsulating cancer therapeutics, yet their susceptibility to physiological degradation and lack of cellular specificity hinder their use as effective oral delivery vehicles. Herein, we engineered novel albumin-core with folic acid functionalized hyperbranched amylopectin shell-type nanogels, prepared through a two-step reaction and loaded with curcumin while the proteinaceous core was undergoing thermal gelation. The nanogels had a mean hydrodynamic diameter of ca. 90 nm and ζ-potential of ca. -24 mV. Encapsulation of curcumin within the nanogels was restored, up to ca. 0.05 mg mL-1, beyond which, a gradual increase in size and a decrease in ζ-potential was observed. The core-shell structures were resilient to in vitro physiological oral-gastrointestinal digestion owing to a liquid crystalline B- and V-type polymorphism in the polysaccharide shell, the latter being driven by the shell functionalization with folic acid. Additionally, these biocompatible nanogels restored stability of the encapsulated curcumin and exhibited augmented cellular uptake and retention specifically in folate receptor-positive HT29 human colon adenocarcinoma cells, inducing early-stage apoptosis. Novel insights from this study represent a promising platform for rational designing of future oral delivery systems that can surmount physiological barriers for delivering cancer therapeutics to colon cancer cells with improved stability and specificity.

Post-transcriptional regulation of C-C motif chemokine ligand 2 expression by ribosomal protein L22 during LPS-mediated inflammation.

Monocyte infiltration to the site of pathogenic invasion is critical for inflammatory response and host defence. However, this process demands precise regulation as uncontrolled migration of monocytes to the site delays resolution of inflammation and ultimately promotes chronic inflammation. C-C motif chemokine ligand 2 (CCL2) plays a key role in monocyte migration, and hence, its expression should be tightly regulated. Here, we report a post-transcriptional regulation of CCL2 involving the large ribosomal subunit protein L22 (RPL22) in LPS-activated, differentiated THP-1 cells. Early events following LPS treatment include transcriptional upregulation of RPL22 and its nuclear accumulation. The protein binds to the first 20 nt sequence of the 5'UTR of ccl2 mRNA. Simultaneous nuclear translocation of up-frameshift-1 protein and its interaction with RPL22 results in cytoplasmic degradation of the ccl2 mRNA at a later stage. Removal of RPL22 from cells results in increased expression of CCL2 in response to LPS causing disproportionate migration of monocytes. We propose that post-transcriptional regulation of CCL2 by RPL22 fine-tunes monocyte infiltration during a pathogenic insult and maintains homeostasis of the immune response critical to resolution of inflammation. DATABASES: Microarray data are available in NCBI GEO database (Accession No GSE126525).

Water-soluble vitamins for controlling starch digestion: Conformational scrambling and inhibition mechanism of human pancreatic α-amylase by ascorbic acid and folic acid.

The inhibition of human pancreatic α-amylase (HPA) enzyme activity can offer facile routes to ameliorate postprandial hyperglycemia in diabetes via control of starch digestion. The present study utilizes complementary experimental (starch digestion kinetics, fluorescence quenching, Förster resonance energy transfer and X-ray diffraction) and computational (molecular docking and dynamics simulation) methods to evaluate the HPA inhibitory activity of eight water-soluble vitamins, for the first time. In particular, ascorbic acid inhibited HPA activity via non-competitive antagonism from two allosteric sites, by channeling the inhibition towards the active site cavity via the triose-phosphate isomerase (TIM) barrel. In contrast, folic acid inhibited HPA activity by binding competitively to the active site cavity and decreasing the disorder in the neighboring loops 3 and 7, which are important mobile loops in HPA for starch digestion. The infusion of such biocompatible and nutritional water-soluble vitamins alongside starch may offer new avenues for diabetes management.

Structurally induced modulation of in vitro digestibility of amylopectin corn starch upon esterification with folic acid.

The present study aims to identify how structural modifications of amylopectin corn starch on esterification with folic acid (FA) affects its in vitro digestion. Small angle X-ray scattering (SAXS) confirmed that at low FA esterification (5-10%), the mesophase order showed the absence of any super-structural order. However, a discotic stacking of SF forming columnar hexagonal phases and columnar helical phases (with strong optical anisotropy) was observed upon increasing FA esterification (20-40%). X-ray diffraction (XRD) evidenced the development of a V and B-type molecular packing order in SF with increased FA esterification from 20 to 40%, with a consequential increase in the percentage of slow digestible starch (SDS) and resistant starch (RS). The slower digestion phenomenon displayed a dual-phase behavior, with digestion rates k1 > k2, where k2 being ca. 0.3 of k1. Stacking over packing order appeared to be more influential in limiting the enzymatic action. A k-means clustering analysis of the total digested starch and Fourier transform infrared (FTIR) spectroscopy peak ratios (1000/1022) cm-1 indicated that 0.04 level FA substitution was crucial for slower hydrolysis of SF. This study provides structural insights for developing starch-folic acid ester derivatives that could form building-block copolymers for future development of oral drug/nutraceutical delivery vehicles with tailored starch digestion properties.

Effect of repeated cycled crystallization on digestibility and molecular structure of glutinous Bora rice starch.

The effects of repeated cycled crystallization on the digestibility and molecular structure of glutinous Bora rice starch were investigated. Temperature cycle 4/45°C; cycle duration 5d; time interval of cycles 24h; and starch to water ratio 1:2 were found to be optimum for SDS (slow digestible starch) product development. The SDS content increased from 18.01±2.11% to 82.81±2.34%. An increase in the resistance to digestion, crystallinity, molecular weight, polydispersity and molecular order was observed in the optimal SDS product. Notably, the FT-IR peak at 947cm-1 and XRD peaks at 2θ≈13° and 20° in the optimal SDS product indicated the formation of V-type complexes even without the presence of co-polymers. Birefringence studies showed a loss of typical Maltese cross in the SDS product and revealed a reorientation of crystalline structures within starch granules, suggestive of imperfect crystallite development.

In silico approaches and proportional odds model towards identifying selective ADAM17 inhibitors from anti-inflammatory natural molecules.

ADAM metallopeptidase domain 17 (ADAM17) is an attractive target for the development of new anti-inflammatory drugs. We aimed to identify selective inhibitors of ADAM17 against matrix metalloproteinase enzymes (MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-13, and MMP-16) which have substantial structural similarity. Target proteins were docked with 29 anti-inflammatory natural molecule ligands and a known selective inhibitor IK682. The ligands were screened based on Lipinski rules, interaction with the ADAM17 active site cavity, and then ranked using the proportional odds model multinomial logistic regression. Silymarin was the most selective inhibitor of ADAM17 exhibiting H-bonding with Glu 406, Gly 349, Glu 398, Asn 447, Tyr 433, and Lys 432. Molecular dynamics simulations were carried out for 10ns. The root mean square deviation (RMSD), root mean squared fluctuations (RMSF), radius of gyration (Rg), solvent accessible surface area (SASA), and H-bonding indicated the induced metastability. A comparison of the principal component analysis revealed that the silymarin complex also explored lesser region compared to IK682 complex. A control study on ADAM17 protein (2OI0) is included. These observations present silymarin (widely present in plants such as milk thistle (Silybum maianum), wild artichokes (Cynara cardunculus), turmeric (Curcuma longa) roots, coriander (Coriandrum sativum) seeds, etc.) as a promising natural template for development of ADAM17 selective drugs.

Influence of bamboo shoot powder fortification on physico-chemical, textural and organoleptic characteristics of biscuits.

Bamboo shoot has attracted significant research and a commercial interest due to its many health-promoting bioactive compounds as well as its effectiveness in decreasing blood pressure, cholesterol and increasing appetite. As availability of fresh shoot is limited due to its seasonality there is need of incorporation of nutrients of shoot to any common food product which is easily available throughout year. Shoots of Bambusa balcooa variety were taken and edible parts were separated. Slices of shoot were boiled, dried, powdered, sieved, analysed for nutritional status and used for biscuit making. Bamboo shoot powder (BSP) was added in 0 % (control), 5, 10, and 15 % level in dry ingredients by replacing wheat flour and other ingredients were kept constant. Dough prepared are firstly analysed for basic characteristics. Then biscuits were prepared and analyzed for moisture, water activity, protein, fiber, fat, ash, phenolics, antioxidant activity, dimension, hardness, color and sensory acceptability. Variations were observed for fiber, antioxidant activity and phenolics from 1.08 to 1.97 %, 3.50 to 17.85 % and 0.45 to 4.19 mg/100 g respectively. Results showed that up to 10 % fortification level the biscuits were acceptable with improved functional and neutraceutical properties compared to the control.

Production and purification of anti-bacterial biometabolite from wild-type Lactobacillus, isolated from fermented bamboo shoot: future suggestions and a proposed system for secondary metabolite onsite recovery during continuous fermentation.

Wild-type lactobacillus isolated form Khorisa, a fermented bamboo shoot product of Assam, India were evaluated for production anti-bacterial secondary biometabolites, against Staphylococcus aureus. Submerged fermentation technique was used for the production of secondary anti-microbial biometabolite by a single wild-type lactobacillus strain, which tested positive for the release of anti-bacterial factor(s). Crude cell-free supernatant was obtained, followed by extraction in water-immiscible solvents viz., chloroform, hexane, petroleum ether. Chloroform extract of cell-free crude supernatant showed maximum yield (0.054 g/ml) and inhibited all indicator bacterial strains viz., Escherichia coli, Staphylococcus aureus, and Bacillus cereus. Yields of hexane and petroleum ether extract were 0.052 and 0.026 g/ml, respectively. Minimum lethal dose concentration assay of the chloroform extract showed LDmin values at 27, 1.68, and 1.68 mg/ml for E. coli, S. aureus, and B. cereus, respectively. Kill time for all the indicator bacterial strains were less than 12 h. The efficacy of the anti-bacterial substance seemed to depend on the presence of organic acids, particularly lactic acid. Conceptual-based suggestion for the development of an onsite secondary metabolites recovery system during continuous fermentation has also been attempted.

Antimicrobial and enzymatic antibrowning film used as coating for bamboo shoot quality improvement.

Edible films were prepared with varying proportion of alginate and starch in the ratio of 2:0(F1), 2:1(F2), 1:1(F3), 1:1.5(F4), 1:2(F5), 0:2(F6) with added carboxymethyl cellulose (15%, w/w of starch). The film F5 had superior barrier, mechanical and thermal properties over the other films. Water vapor permeability, moisture absorption, water solubility, breakage strength and elongation capacity of F5 film were reported as 1.21 × 10(-9)g/Pa h m, 9.37%, 40%, 977.3g and 14.62 mm respectively. However, surface characteristics showed the smooth and uniform film and thermal decomposition took place above 200 °C. The film forming solution of selected F5 film, added with antioxidant and antimicrobial extracts was coated on bamboo shoots and stored for 5 days. The film was successful in lowering the browning of bamboo shoots, and also successfully inhibited surface microbial load. Moreover, the moisture loss of coated shoot was less compared to uncoated.