Mechanisms Associated with Superoxide Radical Scavenging Reactions Involving Phenolic Compounds Deduced Based on the Correlation between Oxidation Peak Potentials and Second-Order Rate Constants Determined Using Flow-Injection Spin-Trapping EPR Methods.

Flow-injection spin-trapping electron paramagnetic resonance (FI-EPR) methods that involve the use of 5,5-dimethyl-pyrroline--oxide (DMPO) as a spin-trapping reagent have been developed for the kinetic study of the O radical scavenging reactions occurring in the presence of various plant-derived and synthetic phenolic antioxidants (Aox), such as flavonoid, pyrogallol, catechol, hydroquinone, resorcinol, and phenol derivatives in aqueous media (pH 7.4 at 25 °C). The systematically estimated second-order rate constants () of these phenolic compounds span a wide range (from 4.

Acetylmelodorinol isolated from Sphaerocoryne affinis seeds inhibits cell proliferation and activates apoptosis on HeLa cells.

Background: Cervical cancer is a major global health concern with a high prevalence in low- and middle-income countries. Natural products, particularly plant-derived compounds, have shown immense potential for developing anticancer drugs. In this study, we aimed to investigate the anticancer properties of the pericarp and seeds of Sphaerocoryne affinis fruit on human cervical carcinoma cells (HeLa) and isolate the bioactive compound from the active fraction.

Spore-Forming Lactic Acid-Producing Bacterium Synthesizes and Excretes Spermidine into the Extracellular Space.

The effect of spermidine in extending healthy longevity has attracted attention. As people age, their ability to synthesize putrescine, the precursor of spermidine, declines, and its supplementation from the diet or gut bacteria is needed. Many bacteria synthesize spermidine, but no strains have been reported to excrete synthesized spermidine from the cells.

Development of Enzymatic Synthesis of γ-Glutamylcarnosine and Its Effects on Taste.

γ-Glutamyl peptides have amide bonds between the γ-carboxy group of glutamic acid and the amino group of amino acids or peptides. Some of these γ-glutamyl peptides are known as kokumi substances. Kokumi substances enhance the taste, mouthfulness, thickness, and continuity of the dish.

Effects of Extract on Lipopolysaccharide-Induced Inflammation via Suppression of NF-κB/MAPK Signaling and Nrf2 Activation.

has been extensively used as a nutrient herb in traditional Vietnamese remedies for the treatment of various diseases, especially inflammatory diseases. However, no detailed research has been conducted examining the molecular mechanisms involved in the suppression of inflammatory response. Here, we studied the effects of methanol extract on lipopolysaccharide (LPS)-induced inflammation using RAW 264.

Anti-Inflammatory Effects of Leaf Extract in Lipopolysaccharide-Induced RAW 264.7 Macrophages.

(L.) Thwaites was used as a traditional medicine to treat many inflammatory diseases for centuries. However, its effects on the inflammatory response are not yet characterized.

Nucleobase-involved native chemical ligation: a novel reaction between an oxanine nucleobase and N-terminal cysteine for oligonucleotide-peptide conjugation.

In bioconjugation chemistry, achieving a target-specific reaction for a non-modified amino acid is challenging. Here, we report a novel nucleobase-involved native chemical ligation (NbCL) that allows a site-specific oligonucleotide-peptide conjugation via a new S-N acyl transfer reaction between an oxanine nucleobase and N-terminal cysteine.

Silica-Supported Catalyst for Enantioselective Arylation of Aldehydes under Batch and Continuous-Flow Conditions.

A silica-supported 3-aryl H-BINOL-derived titanium catalyst exhibited high performance in the enantioselective arylation of aromatic aldehydes using Grignard and organolithium reagents not only under batch conditions but also under continuous-flow conditions. Even with a simple pipet reactor packed with the heterogeneous catalyst, the enantioselective production of chiral diarylmethanols could be achieved through a continuous introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The pipet reactor could be used repeatedly in different reactions without appreciable deterioration of the activity.

Entire-Dataset Analysis of NMR Fast-Exchange Titration Spectra: A Mg Titration Analysis for HIV-1 Ribonuclease H Domain.

This article communicates our study to elucidate the molecular determinants of weak Mg interaction with the ribonuclease H (RNH) domain of HIV-1 reverse transcriptase in solution. As the interaction is weak (a ligand-dissociation constant >1 mM), nonspecific Mg interaction with the protein or interaction of the protein with other solutes that are present in the buffer solution can confound the observed Mg-titration data. To investigate these indirect effects, we monitored changes in the chemical shifts of backbone amides of RNH by recording NMR H-N heteronuclear single-quantum coherence spectra upon titration of Mg into an RNH solution.

Aggregation property of glycyrrhizic acid and its interaction with cyclodextrins analyzed by dynamic light scattering, isothermal titration calorimetry, and NMR.

The structural properties of glycyrrhizic acid, a sweet-tasting constituent of Glycyrrhiza glabra, and its interaction with cyclodextrins were analyzed using dynamic light scattering, isothermal titration calorimetry, and NMR. The dynamic light scattering and NMR studies showed that glycyrrhizic acid forms a water-soluble aggregate that disperses upon the addition of γ-cyclodextrin. The high sweetness of glycyrrhizic acid can be closely correlated with this aggregation, because the multimers of glycyrrhizic acid can simultaneously bind to the sweet taste receptors on the human tongue.

How does hemoglobin generate such diverse functionality of physiological relevance?

The absolute values of the O2-affinities (P50, Klow, and Khigh) of hemoglobin (Hb) are regulated neither by changes in the static T-/R-quaternary and associated tertiary structures nor the ligation states. They are pre-determined and regulated by the extrinsic environmental factors such as pH, buffers, and heterotropic effectors. The effect and role of O2 on Hb are reversibly to drive the structural allosteric equilibrium between the T(deoxy)- and R(oxy)-Hb toward R(oxy)-Hb (the structural allostery).

Creation of a binuclear purple copper site within a de novo coiled-coil protein.

Although various kinds of metal binding proteins have been constructed by de novo design, the creation of a binuclear metal binding site remains especially challenging. The purple copper site in subunit II of COX, referred to as the Cu(A) site, has two copper ions bridged by two Cys residues. We constructed the Cu(A) site consisting of two Cys and two His residues in a de novo designed four-helical coiled-coil protein.

Solution structure and stability of the DNA undecamer duplexes containing oxanine mismatch.

Solution structures of DNA duplexes containing oxanine (Oxa, O) opposite a cytosine (O:C duplex) and opposite a thymine (O:T duplex) have been solved by the combined use of (1)H NMR and restrained molecular dynamics calculation. One mismatch pair was introduced into the center of the 11-mer duplex of [d(GTGACO(6)CACTG)/d(CAGTGX(17)GTCAC), X = C or T]. (1)H NMR chemical shifts and nuclear Overhauser enhancement (NOE) intensities indicate that both the duplexes adopt an overall right-handed B-type conformation.

Chemical identification and ethological function of soldier-specific secretion in Japanese subterranean termite Reticulitermes speratus (Rhinotermitidae).

We identified the soldier-specific compounds in the Japanese subterranean termite, Reticulitermes speratus, to clarify their ethological roles. Silica gel column chromatography separated one major soldier-specific compound in the hexane fraction accounting for 70-80% of the total amount of the fraction, while cuticular hydrocarbons constituted the rest. We identified the compound as β-selinene by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy.

T-quaternary structure of oxy human adult hemoglobin in the presence of two allosteric effectors, L35 and IHP.

The cooperative O(2)-binding of hemoglobin (Hb) have been assumed to correlate to change in the quaternary structures of Hb: T(deoxy)- and R(oxy)-quaternary structures, having low and high O(2)-affinities, respectively. Heterotropic allosteric effectors have been shown to interact not only with deoxy- but also oxy-Hbs causing significant reduction in their O(2)-affinities and the modulation of cooperativity. In the presence of two potent effectors, L35 and inositol hexaphosphate (IHP) at pH 6.

UV luminescent organic-capped ZnO quantum dots synthesized by alkoxide hydrolysis with dilute water.

A novel synthesis route to organic-capped and colloidal ZnO quantum dots (QDs) has been developed. Specifically, zinc-di-t-butoxide and zinc-di-n-butoxide are hydrolyzed by very dilute water (400-600 mass ppm) in hydrophilic benzylamine and polymerized to ZnO by dehydration and/or a butanol elimination reaction. Growth of the ZnO QDs and exchange of the surface capping ligand from the hydroxyl groups and/or benzylamine to the oleylamine occur by heating the colloidal solution after addition of the oleylamine at 100-180°C.

Creation of a type 1 blue copper site within a de novo coiled-coil protein scaffold.

Type 1 blue copper proteins uniquely coordinate Cu(2+) in a trigonal planar geometry, formed by three strong equatorial ligands, His, His, and Cys, in the protein. We designed a stable Cu(2+) coordination scaffold composed of a four-stranded α-helical coiled-coil structure. Two His residues and one Cys residue were situated to form the trigonal planar geometry and to coordinate the Cu(2+) in the hydrophobic core of the scaffold.

Identification of an antiamyloidogenic substance from mulberry leaves.

Fibrillar aggregates of amyloid beta-peptides are major constituents of the plaques found in the brains of patients with Alzheimer's disease, and have been implicated in the neurotoxicity of Alzheimer's. We previously reported that the methanol extract of mulberry leaves inhibits the formation of amyloid beta-peptide (1-42)-fibrils in vitro, and protects hippocampal neurons from amyloid beta-peptide (1-42)-induced cell death. In this study, we identified antiamyloidogenic substances, pheophorbide a, kaempferol -3-O-glucoside, and kaempferol -3-O-(6-malonyl) glucoside, from the methanol extract of mulberry leaves.

A cysteine residue near the propionate side chain of heme is the radical site in ascorbate peroxidase.

The radical scavenger 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO(*)) and the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were used in conjunction with mass spectrometry to identify the protein-based radical sites of the H(2)O(2)-tolerant ascorbate peroxidase (APX) of the red alga Galdieria partita and the H(2)O(2)-sensitive stromal APX of tobacco. A cysteine residue in the vicinity of the propionate side chain of heme in both enzymes was labeled with TEMPO(*) and DMPO in an H(2)O(2)-dependent manner, indicating that these cysteine residues form thiyl radicals through interaction of APX with H(2)O(2). TEMPO(*) bound to the cysteine thiyl radicals, and sulfinylated and sulfonylated them.

Flow-injection EPR investigation on OH radical scavenging activity of Gd(III) containing MRI contrast media.

The OH radical scavenging activity of a series of Gd(III) MRI contrast media, such as Gd(III)DTPA, Gd(III)BMA and Gd(III)DO3A, were evaluated by means of EPR spin trapping measurements. The second order reaction rate constant (k2) occurring between Gd(III)DTPA and OH radical was estimated to be 3.26 x 10(10) (M(-1)s(-1)), which was ten times larger than that of the free ligand DTPA (3.

1H NMR study on equilibrium between parallel G-quartet structures.

Structural transition of parallel G-quartet formed by d(TG4T) are induced by monovalent cations. In the presence of K+ ion, G-quartet takes a single conformation, while in the presence of Na+ ion, the equilibrium between more than three conformations were observed.

The roles of conserved amino acids on substrate binding and conformational integrity of ClpB N-terminal domain.

Escherichia coli heat shock protein ClpB disaggregates denatured protein in cooperation with the DnaK chaperone system. Several studies showed that the N-terminal domain is essential for the chaperone activity, but its role is still largely unknown. The N-terminal domain contains two structurally similar subdomains, and conserved amino acids Thr7 and Ser84 share the same position in two apparent sequence repeats.

Interaction of gymnemic acid with cyclodextrins analyzed by isothermal titration calorimetry, NMR and dynamic light scattering.

The physiological phenomenon that the antisweet taste effect of gymnemic acid (GA) is diminished by application of gamma-cyclodextrin (gamma-CD) to the mouth was evaluated at the molecular level using isothermal titration calorimetry, NMR and dynamic light scattering. These analyses showed that GA specifically binds to gamma-CD. Thermodynamic analysis using isothermal titration calorimetry revealed that the association constant of GA and gamma-CD is 10(5)-10(6) m(-1) with favorable enthalpy and entropy changes.

Pyrene is highly emissive when attached to the RNA duplex but not to the DNA duplex: the structural basis of this difference.

Through binding and fluorescence studies of oligonucleotides covalently attached to a pyrene group via one carbon linker at the sugar residue, we previously found that pyrene-modified RNA oligonucleotides do not emit well in the single-stranded form, yet the attached pyrene emits with a significantly high quantum yield upon binding to a complementary RNA strand. In sharp contrast, similarly modified pyrene-DNA probes exhibit very weak fluorescence both in the double-stranded and single-stranded forms. The pyrene-modified RNA oligonucleotides therefore provide a useful tool for monitoring RNA hybridization.

Relationship between temporary inhibition and structure of disulfide-linkage analogs of marinostatin, a natural ester-linked protein protease inhibitor.

A 12-residue marinostatin [MST(1-12): (1)FATMRYPSDSDE(12)] which contains two ester linkages of Thr(3)-Asp(9) and Ser(8)-Asp(11) strongly inhibits subtilisin. In order to study the relationship between the inhibitory activity, structure, and stability of MST, MST analogs were prepared by changing ester linkages to a disulfide linkages. The analogs without the disulfide linkage between 3 and 9 positions lost their inhibitory activity.