Characterization of a CXCR4 antagonist TIQ-15 with dual tropic HIV entry inhibition properties.

The chemokine co-receptors CXCR4 and CCR5 mediate HIV entry and signal transduction necessary for viral infection. However, to date only the CCR5 antagonist maraviroc is approved for treating HIV-1 infection. Given that approximately 50% of late-stage HIV patients also develop CXCR4-tropic virus, clinical anti-HIV CXCR4 antagonists are needed. Here, we describe a novel allosteric CXCR4 antagonist TIQ-15 which inhibits CXCR4-tropic HIV-1 infection of primary and transformed CD4 T cells. TIQ-15 blocks HIV entry with an IC50 of 13 nM. TIQ-15 also inhibits SDF-1α/CXCR4-mediated cAMP production, cofilin activation, and chemotactic signaling. In addition, TIQ-15 induces CXCR4 receptor internalization without affecting the levels of the CD4 receptor, suggesting that TIQ-15 may act through a novel allosteric site on CXCR4 for blocking HIV entry. Furthermore, TIQ-15 did not inhibit VSV-G pseudotyped HIV-1 infection, demonstrating its specificity in blocking CXCR4-tropic virus entry, but not CXCR4-independent endocytosis or post-entry steps. When tested against a panel of clinical isolates, TIQ-15 showed potent inhibition against CXCR4-tropic and dual-tropic viruses, and moderate inhibition against CCR5-tropic isolates. This observation was followed by a co-dosing study with maraviroc, and TIQ-15 demonstrated synergistic activity. In summary, here we describe a novel HIV-1 entry inhibitor, TIQ-15, which potently inhibits CXCR4-tropic viruses while possessing low-level synergistic activities against CCR5-tropic viruses. TIQ-15 could potentially be co-dosed with the CCR5 inhibitor maraviroc to block viruses of mixed tropisms.

The Toxoplasma glucan phosphatase TgLaforin utilizes a distinct functional mechanism that can be exploited by therapeutic inhibitors.

Toxoplasma gondii is an intracellular parasite that generates amylopectin granules (AGs), a polysaccharide associated with bradyzoites that define chronic T. gondii infection. AGs are postulated to act as an essential energy storage molecule that enable bradyzoite persistence, transmission, and reactivation. Importantly, reactivation can result in the life-threatening symptoms of toxoplasmosis. T. gondii encodes glucan dikinase and glucan phosphatase enzymes that are homologous to the plant and animal enzymes involved in reversible glucan phosphorylation and which are required for efficient polysaccharide degradation and utilization. However, the structural determinants that regulate reversible glucan phosphorylation in T. gondii are unclear. Herein, we define key functional aspects of the T. gondii glucan phosphatase TgLaforin (TGME49_205290). We demonstrate that TgLaforin possesses an atypical split carbohydrate-binding-module domain. AlphaFold2 modeling combined with hydrogen-deuterium exchange mass spectrometry and differential scanning fluorimetry also demonstrate the unique structural dynamics of TgLaforin with regard to glucan binding. Moreover, we show that TgLaforin forms a dual specificity phosphatase domain-mediated dimer. Finally, the distinct properties of the glucan phosphatase catalytic domain were exploited to identify a small molecule inhibitor of TgLaforin catalytic activity. Together, these studies define a distinct mechanism of TgLaforin activity, opening up a new avenue of T. gondii bradyzoite biology as a therapeutic target.

Modulation in Techno-Functional, Textural Properties, In Vitro Starch Digestibility and Macromolecular-Structural Interactions of Pasta with Potato (Solanum tuberosum L.).

The replacement of semolina with potato flour (PF) and potato mash (PM) at different levels was assessed for its effects on pasta quality. The results showed that the addition of PF and PM increased the pasting viscosity of the blends; in addition, PF enhanced the functional properties, while PM reduced them. The minimum cooking time decreased with PF and PM, while the PF pasta exhibited a higher cooking loss (5.02 to 10.44%) than the PM pasta, which exhibited a lower cooking loss. The pasta with PF and PM showed an increase in the total phenolic and flavonoid content, with reduced in vitro digestibility as confirmed by Fourier transform infrared spectroscopy. The PF pasta exhibited lower lightness and higher yellowness than the PM pasta, and its firmness and toughness also modulated owing to the complex interaction between potato starches and the gluten protein matrix, as evident from scanning electron microscopy. Sensory data revealed that pasta containing 30% PF and 16% PM was highly acceptable.

Cereal bar functionalised with non-conventional alfalfa and dhaincha protein isolates: quality characteristics, nutritional composition and antioxidant activity.

The utilization of conventional protein sources like gluten, soy, dairy proteins, and nuts in the development of protein-enriched cereal bars presents a challenge for their consumption by the population suffering from celiac and other food protein allergies. In the present investigation, protein-rich cereal bars were developed using non-conventional protein isolates (alfalfa and dhiancha (API & DPI) and were evaluated for their quality attributes, nutritional composition, and bioactive potential. The incorporation of protein isolates increased the weight, density, and non-enzymatic browning and decreased the water activity in the bars. The hardness of the bar increased with the addition of protein isolates; however, reduced hardness was observed at 7.5 and 10% levels of API. Supplementation with protein isolates enhanced the protein content (7.83-16.71%), total phenols (1642-4956 GAE µg/g), total flavonoids (268-984 QE µg/g), DPPH radical scavenging activity (96.38-114.82 TEAC µmol/100 g) and reducing power (1926-3586 AAE µg/g) of the bars. Cereal bars maintained good sensory score and overall acceptability at 10 and 5% level of incorporation of API and DPI respectively.

Cooperative Kinetics of the Glucan Phosphatase Starch Excess4.

Glucan phosphatases are members of a functionally diverse family of dual-specificity phosphatase (DSP) enzymes. The plant glucan phosphatase Starch Excess4 (SEX4) binds and dephosphorylates glucans, contributing to processive starch degradation in the chloroplast at night. Little is known about the complex kinetics of SEX4 when acting on its complex physiologically relevant glucan substrate. Therefore, we explored the kinetics of SEX4 against both insoluble starch and soluble amylopectin glucan substrates. SEX4 displays robust activity and a unique sigmoidal kinetic response to amylopectin, characterized by a Hill coefficient of 2.77 ± 0.63, a signature feature of cooperativity. We investigated the basis for this positive kinetic cooperativity and determined that the SEX4 carbohydrate-binding module (CBM) dramatically influences the binding cooperativity and substrate transformation rates. These findings provide insights into a previously unknown but important regulatory role for SEX4 in reversible starch phosphorylation and further advances our understanding of atypical kinetic mechanisms.

Dynamics of Germination Behaviour, Protein Secondary Structure, Technofunctional Properties, Antinutrients, Antioxidant Capacity and Mineral Elements in Germinated Dhaincha.

RESEARCH BACKGROUND: Dhaincha (Sesbania aculeata) is a forage legume primarily used for green manuring and animal feed. Good nutritional profile of dhaincha makes it a potential alternative legume in human nutrition. However, the presence of high amount of antinutrients poses a problem in its utilisation for food applications. The present investigation intends to germinate dhaincha seeds at different time-temperature regimes and to evaluate the process of germination to ascertain optimal conditions and improve its potential for utilisation. EXPERIMENTAL APPROACH: Dhaincha seeds were germinated at 24, 28 and 32 °C for 24, 48 and 72 h. Germination characteristics and germination loss, spectral characteristics, technofunctionality, antinutrients, bioactive constituents, antioxidant capacity and mineral element content of germinated dhaincha were evaluated. Optimal balance of technobiofunctionality of germinated dhaincha seeds was validated by principal component analysis. RESULTS AND CONCLUSIONS: Sprout length and germination loss increased with the higher germination temperature and prolonged germination time. Seeds showed similar germination rate at 28 and 32 °C and it was markedly higher than at 24 °C. Germination for 24 h resulted in mild conformational changes in the secondary structure of proteins, whereas germination for 48 and 72 h exhibited major conformational changes in the ß-sheets, resulting in the improvement in the hydration and foaming properties. Progression of germination (72 h) caused the decrease of tannin (24.47%), phytic acid (16.38%) and saponin (24.58%) mass fractions, and of trypsin inhibitor (40.33%) and lectin activity (62.50%). Slight decrease of DPPH˙ (3.7%) and ABTS˙+ (18.5%) values was also observed, whereas total flavonoid content (36.14%) and metal chelating activity (26.76%) increased. Total phenolics, FRAP, and reducing power decreased after 24 h, followed by a gradual increase. Zinc extractability increased drastically with germination. Germination at 28 °C for 72 h resulted in higher reduction of antinutrients with optimal retention of antioxidant activity and better functional characteristics, as validated by principal component analysis. NOVELTY AND SCIENTIFIC CONTRIBUTION: Dhaincha is an unknown crop in Europe, and even in Asia it is predominantly used as green manure and animal feed. This research demonstrated that the intervention in germination can transform dhaincha into a promising crop for food industry. Germinated dhaincha exhibited enhanced technobiofunctionality for utilisation in various food formulations.

Enhancement of Digestibility of Nutrients (In vitro), Antioxidant Potential and Functional Attributes of Wheat Flour Through Grain Germination.

Wheat grains were germinated at different time (12, 24, 36, and 48 h) and temperature (25, 30, and 35°C) to enhance the functionality of resultant flour. Results revealed that an increase in germination time and temperature enhanced the in vitro digestibility of starch (10.35-42.30 %) and proteins (6.31-44.02 %) owing to their depolymerization by hydrolytic enzymes. Total phenolic and flavonoid content of wheat during germination at variable conditions were enhanced significantly (p < 0.05) from 3.62 to 5.54 mg GAE/g and 32.06 to 54.33 mg QE/100 g, respectively. Germination at elevated temperature (35°C) for a prolonged time (48 h) increased the DPPH RSA by 58.85 %, reducing power by 80.40 % and metal chelating activity by 112.26 % as a result of the structural breakdown of bound phenolics. Increased activity of hydrolytic enzymes also results in a continuous reduction in the viscosity and lightness values of wheat flour. Tailored germination, therefore, can be offered as a tool to increase the nutrient digestibility and bioactive potential of wheat thus resulting in producing the naturally modified flour with enhanced functionality.

Ferric Heme Superoxide Reductive Transformations to Ferric Heme (Hydro)Peroxide Species: Spectroscopic Characterization and Thermodynamic Implications for H-Atom Transfer (HAT).

A new end-on low-spin ferric heme peroxide, [(PIm )FeIII -(O22- )]- (PIm -P), and subsequently formed hydroperoxide species, [(PIm )FeIII -(OOH)] (PIm -HP) are generated utilizing the iron-porphyrinate PIm with its tethered axial base imidazolyl group. Measured thermodynamic parameters, the ferric heme superoxide [(PIm )FeIII -(O2⋅- )] (PIm -S) reduction potential (E°') and the PIm -HP pKa value, lead to the finding of the OO-H bond-dissociation free energy (BDFE) of PIm -HP as 69.5 kcal mol-1 using a thermodynamic square scheme and Bordwell relationship. The results are validated by the observed oxidizing ability of PIm -S via hydrogen-atom transfer (HAT) compared to that of the F8 superoxide complex, [(F8 )FeIII -(O2.- )] (S) (F8 =tetrakis(2,6-difluorophenyl)porphyrinate, without an internally appended axial base imidazolyl), as determined from reactivity comparison of superoxide complexes PIm -S and S with the hydroxylamine (O-H) substrates TEMPO-H and ABNO-H.

Heme-FeIII Superoxide, Peroxide and Hydroperoxide Thermodynamic Relationships: FeIII-O2•- Complex H-Atom Abstraction Reactivity.

Establishing redox and thermodynamic relationships between metal-ion-bound O2 and its reduced (and protonated) derivatives is critically important for a full understanding of (bio)chemical processes involving dioxygen processing. Here, a ferric heme peroxide complex, [(F8)FeIII-(O22-)]- (P) (F8 = tetrakis(2,6-difluorophenyl)porphyrinate), and a superoxide complex, [(F8)FeIII-(O2•-)] (S), are shown to be redox interconvertible. Using Cr(η-C6H6)2, an equilibrium state where S and P are present is established in tetrahydrofuran (THF) at -80 °C, allowing determination of the reduction potential of S as -1.17 V vs Fc+/0. P could be protonated with 2,6-lutidinium triflate, yielding the low-spin ferric hydroperoxide species, [(F8)FeIII-(OOH)] (HP). Partial conversion of HP back to P using a derivatized phosphazene base gave a P/HP equilibrium mixture, leading to the determination of pKa = 28.8 for HP (THF, -80 °C). With the measured reduction potential and pKa, the O-H bond dissociation free energy (BDFE) of hydroperoxide species HP was calculated to be 73.5 kcal/mol, employing the thermodynamic square scheme and Bordwell relationship. This calculated O-H BDFE of HP, in fact, lines up with an experimental demonstration of the oxidizing ability of S via hydrogen atom transfer (HAT) from TEMPO-H (2,2,6,6-tetramethylpiperdine-N-hydroxide, BDFE = 66.5 kcal/mol in THF), forming the hydroperoxide species HP and TEMPO radical. Kinetic studies carried out with TEMPO-H(D) reveal second-order behavior, kH = 0.5, kD = 0.08 M-1 s-1 (THF, -80 °C); thus, the hydrogen/deuterium kinetic isotope effect (KIE) = 6, consistent with H-atom abstraction by S being the rate-determining step. This appears to be the first case where experimentally derived thermodynamics lead to a ferric heme hydroperoxide OO-H BDFE determination, that FeIII-OOH species being formed via HAT reactivity of the partner ferric heme superoxide complex.

Synthesis and biological evaluation of 5'-C-methyl nucleotide prodrugs for treating HCV infections.

Nucleotide prodrugs are of great clinical interest for treating a variety of viral infections due to their ability to target tissues selectively and to deliver relatively high concentrations of the active nucleotide metabolite intracellularly. However, their clinical successes have been limited, oftentimes due to unwanted in vivo metabolic processes that reduce the quantities of nucleoside triphosphate that reach the site of action. In an attempt to circumvent this, we designed novel nucleosides that incorporate a sterically bulky group at the 5'-carbon of the phosphoester prodrug, which we reasoned would reduce the amounts of non-productive PO bond cleavage back to the corresponding nucleoside by nucleotidases. Molecular docking studies with the NS5B HCV polymerase suggested that a nucleotide containing a 5'-methyl group could be accommodated. Therefore, we synthesized mono- and diphosphate prodrugs of 2',5'-C-dimethyluridine stereoselectively and evaluated their cytotoxicity and anti-HCV activity in the HCV replicon assay. All four prodrugs exhibited anti-HCV activity with IC50 values in the single digit micromolar concentrations, with the 5'(R)-C-methyl prodrug displaying superior potency relative to its 5'(S)-C-methyl counterpart. However, when compared to the unmethylated prodrug, the potency is poorer. The poorer potency of these prodrugs may be due to unfavorable steric interactions of the 5'-C-methyl group in the active sites of the kinases that catalyze the formation of active triphosphate metabolite.

Heme-Cu Binucleating Ligand Supports Heme/O2 and FeII-CuI/O2 Reactivity Providing High- and Low-Spin FeIII-Peroxo-CuII Complexes.

The focus of this study is in the description of synthetic heme/copper/O2 chemistry employing a heme-containing binucleating ligand which provides a tridentate chelate for copper ion binding. The addition of O2 (-80 °C, tetrahydrofuran (THF) solvent) to the reduced heme compound (PImH)FeII (1), gives the oxy-heme adduct, formally a heme-superoxide complex FeIII-(O2•-) (2) (resonance Raman spectroscopy (rR): νO-O, 1171 cm-1 (Δ18O2, -61 cm-1); νFe-O, 575 cm-1 (Δ18O2, -24 cm-1)). Simple warming of 2 to room temperature regenerates reduced complex 1; this reaction is reversible, as followed by UV-vis spectroscopy. Complex 2 is electron paramagnetic resonance (EPR)-silent and exhibits upfield-shifted pyrrole resonances (δ 9.12 ppm) in 2H NMR spectroscopy, indicative of a six-coordinate low-spin heme. The coordination of the tethered imidazolyl arm to the heme-superoxide complex as an axial base ligand is suggested. We also report the new fully reduced heme-copper complex [(PImH)FeIICuI]+ (3), where the copper ion is bound to the tethered tridentate portion of PImH. This reacts with O2 to give a distinctive low-temperature-stable, high-spin (S = 2, overall) peroxo-bridged complex [(PImH)FeIII-(O22-)-CuII]+ (3a): λmax, 420 (Soret), 545, 565 nm; δpyrr, 93 ppm; νO-O, 799 cm-1 (Δ18O2, -48 cm-1); νFe-O, 524 cm-1 (Δ18O2, -23 cm-1). To 3a, the addition of dicyclohexylimidazole (DCHIm), which serves as a heme axial base, leads to low-spin (S = 0 overall) species complex [(DCHIm)(PImH)FeIII-(O22-)-CuII]+ (3b): λmax, 425 (Soret), 538 nm; δpyrr, 10.2 ppm; νO-O, 817 cm-1 (Δ18O2, -55 cm-1); νFe-O, 610 cm-1 (Δ18O2, -26 cm-1). These investigations into the characterization of the O2-adducts from (PImH)FeII (1) with/without additional copper chelation advance our understanding of the dioxygen reactivity of heme-only and heme/Cu-ligand heterobinuclear system, thus potentially relevant to O2 reduction in heme-copper oxidases or fuel-cell chemistry.

Impact of Feed Moisture on Microstructure, Crystallinity, Pasting, Physico-Functional Properties and In Vitro Digestibility of Twin-Screw Extruded Corn and Potato Starches.

The effect of extrusion feed moisture (FM) on the microstructure, pasting, physico-functional properties and in vitro starch digestibility (IVSD) of corn and potato starches was investigated using scanning electron microscopy (SEM), X-ray diffractometry and a rapid visco-analyser. Starches were extruded at 14, 18 and 22% FM with an extrusion temperature of 100 °C and a screw speed of 100 rpm. Extruded starches showed lower L* (lightness) values and higher a* and b* values than native starches. An increase in FM increased the L* values and decreased the a* and b* values of extruded starches. Extrusion resulted in complete destruction and reduced crystallinity of the starch structure. Extruded starches showed a lower water absorption index (WAI), peak viscosity (PV), final viscosity (FV), breakdown viscosity (BDV) and setback viscosity (SBV) with a higher water solubility index (WSI) and IVSD than native starches. FM showed a negative correlation with the WSI and IVSD and a positive correlation with the WAI, PV, FV, BDV and SBV of extruded starches.

In vitro nutrient digestibility and antioxidative properties of flour prepared from sorghum germinated at different conditions.

Germination can be used as a bio-processing practice to enhance the digestibility of nutrient and improve the bioactive compounds and rheological properties of food grains. In the present study, effect of germination time 12, 24, 36 and 48 h and temperature 25, 30 and 35 °C on carbohydrate profile, enzyme activity, in vitro nutrient digestibility, antioxidant activity, bioactive components and rheological characteristics of sorghum was examined. As time and temperature for germination progressed, it considerably enhance the activity of diastase enzyme and also the sugar content by hydrolysis of starch and further enhance the in vitro digestibility of starch by 10.50-36.25%. Germinated sorghum had high in vitro protein digestibility and it ranges from 57.50 to 77.91% as compared to native sorghum (54.09%). Germination of sorghum for longer time period at elevated conditions appreciably improve the antioxidant activity by 4.24-52.96%, total phenolic content and flavonoid content by 1.60-4.09 mgGAE/g and 60.30-94.03 mgQE/100 g, respectively Similarly reducing power increased from 29.27 to 47.19 µg AAE/g and metal chelating activity enhanced 19.48-52.09% as period for germination goes from 12 to 48 h and temperature from 25 to 35 °C. Increased enzyme activity during germination degrades the starch and thus lowers down the peak and final viscosity of sorghum. Increased enzymatic activity and higher antioxidant activity also lower down the lightness value by 12.48% while a* was increased by 6.78%. Germination of sorghum thus offers a tool to increase the nutrient digestibility and bioactive potential of sorghum without any chemical or genetic engineering.

Oligomerization and carbohydrate binding of glucan phosphatases.

Glucan phosphatases are a unique subset of the phosphatase family that bind to and dephosphorylate carbohydrate substrates. Family members are found in diverse organisms ranging from single-cell red algae to humans. The nature of their functional oligomerization has been a source of considerable debate. We demonstrate that the human laforin protein behaves aberrantly when subjected to Size Exclusion Chromotography (SEC) analysis due to interaction with the carbohydrate-based matrix. This interaction complicates the analysis of laforin human disease mutations. Herein, we show that SEC with Multi-Angle static Light Scattering (SEC-MALS) provides a method to robustly define the oligomerization state of laforin and laforin variants. We further analyzed glucan phosphatases from photosynthetic organisms to define if this interaction was characteristic of all glucan phosphatases. Starch EXcess-four (SEX4) from green plants was found to lack significant interaction with the matrix and instead exists as a monomer. Conversely, Cm-laforin, from red algae, exists as a monomer in solution while still exhibiting significant interaction with the matrix. These data demonstrate a range of oligomerization behaviors of members of the glucan phosphatase family, and establish SEC-MALS as a robust methodology to quantify and compare oligomerization states between different proteins and protein variants in this family.

Cereal starch nanoparticles-A prospective food additive: A review.

Starch is one of the most abundant biopolymers in nature and is typically isolated from plants in the form of micro-scale granules. Raw starch has limited applications due to its innate disadvantages such as poor solubility in cold water, tendency to retrograde and high viscosity once it is gelatinized. Therefore, some degree of modification is required to enhance its functionality. Starch nanoparticle is one of the products of such modification. Chemical, enzymatic, and physical treatments are used for the preparation of starch nanoparticles and to study their granular and molecular structures. Characterization of starch nanoparticles on the size distribution, crystalline structure, and physical properties in relation to the starch sources and preparation methods can be done using various characterization tools e.g. Scanning Electron Microscopy, Transmission Electron Microscopy, Atomic Florescence Microscopy, etc. Starch nanoparticles can be used as a food additive as it has adverse range of uses in food such as emulsion stabilizer, fat replacer, Thickener, or rheology modifier etc.

Patterns of Systemic and Cervicovaginal Fluid Inflammatory Cytokines throughout Pregnancy.

OBJECTIVE: This study describes the normal variations in serum and cervicovaginal fluid (CVF) cytokine levels throughout pregnancy. STUDY DESIGN: This multicenter, prospective study examined trimester-specific maternal serum and CVF cytokines (interleukin [IL]-1α, IL-1ß, IL-6, IL-8, IL-10, tumor necrosis factor-α, and C-reactive protein [CRP]). A two-factor linear mixed modeling approach compared cytokine distribution, while pairwise comparisons evaluated differences over time. RESULTS: Trimester-specific serum cytokine data were available for 288, 243, and 221 patients, whereas CVF cytokine data were available for 273, 229, and 198 patients. CVF had significantly higher concentrations of IL-1α, IL-1ß, IL-6, IL-8, and matrix metalloproteinase-8 (p < 0.001), irrespective of the trimester. At all time points, IL-10 and CRP concentrations were higher in serum than CVF (p < 0.001). Serum IL-10 increased significantly throughout pregnancy (p < 0.001). CONCLUSION: Differences in cytokine distribution across different biological fluids are evident throughout pregnancy. These findings provide a framework for examining patterns of changes in cytokines throughout pregnancy.

Effect of pregelatination on rheology, cooking and antioxidant activity of pasta.

The present study explores the possibility of using twin screw extruder for preparation of pregelatinized pasta. The effects of extrusion parameters feed moisture (28 and 32%), barrel temperature (60-105 °C) and screw speed (100-200 rpm) on pregelatinized pasta were investigated. Prepared pasta was analysed for quality characteristics in terms of cooking quality, degree of gelatinization, color, texture, pasting properties, bioactive composition. Results indicated that higher screw speed improved the cooking quality of pasta and decreased gruel solid loss. Degree of gelatinization revealed positive relation with temperature and feed moisture. Extrusion conditions, altered the color of pasta, a decrease in L*, increase in a* and b* values was observed. Higher peak viscosity was observed at lower barrel temperature and feed moisture. A significant retention in total phenolic content and flavonoid content was observed with higher feed moisture. Extrusion leads to increase in antioxidant activity and firmness upon increasing screw speed and feed moisture.

Critical Aspects of Heme-Peroxo-Cu Complex Structure and Nature of Proton Source Dictate Metal-O(peroxo) Breakage versus Reductive O-O Cleavage Chemistry.

The 4H+/4e- reduction of O2 to water, a key fuel-cell reaction also carried out in biology by oxidase enzymes, includes the critical O-O bond reductive cleavage step. Mechanistic investigations on active-site model compounds, which are synthesized by rational design to incorporate systematic variations, can focus on and resolve answers to fundamental questions, including protonation and/or H-bonding aspects, which accompany electron transfer. Here, we describe the nature and comparative reactivity of two low-spin heme-peroxo-Cu complexes, LS-4DCHIm, [(DCHIm)F8FeIII-(O22-)-CuII(DCHIm)4]+, and LS-3DCHIm, [(DCHIm)F8FeIII-(O22-)-CuII(DCHIm)3]+ (F8 = tetrakis(2,6-difluorophenyl)-porphyrinate; DCHIm = 1,5-dicyclohexylimidazole), toward different proton (4-nitrophenol and [DMF·H+](CF3SO3-)) (DMF = dimethyl-formamide) or electron (decamethylferrocene (Fc*)) sources. Spectroscopic reactivity studies show that differences in structure and electronic properties of LS-3DCHIm and LS-4DCHIm lead to significant differences in behavior. LS-3DCHIm is resistant to reduction, is unreactive toward weakly acidic 4-NO2-phenol, and stronger acids cleave the metal-O bonds, releasing H2O2. By contrast, LS-4DCHIm forms an adduct with 4-NO2-phenol, which includes an H-bond to the peroxo O-atom distal to Fe (resonance Raman (rR) spectroscopy and DFT). With addition of Fc* (2 equiv overall required), O-O reductive cleavage occurs, giving water, Fe(III), and Cu(II) products; however, a kinetic study reveals a one-electron rate-determining process, ket = 1.6 M-1 s-1 (-90 °C). The intermediacy of a high-valent [(DCHIm)F8FeIV═O] species is thus implied, and separate experiments show that one-electron reduction-protonation of [(DCHIm)F8FeIV═O] occurs faster (ket2 = 5.0 M-1 s-1), consistent with the overall postulated mechanism. The importance of the H-bonding interaction as a prerequisite for reductive cleavage is highlighted.

A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex-The Product of the Reaction of Nitrogen Monoxide (·NO(g)) with a Ferric-Superoxide Species.

Peroxynitrite (-OON═O, PN) is a reactive nitrogen species (RNS) which can effect deleterious nitrative or oxidative (bio)chemistry. It may derive from reaction of superoxide anion (O2•-) with nitric oxide (·NO) and has been suggested to form an as-yet unobserved bound heme-iron-PN intermediate in the catalytic cycle of nitric oxide dioxygenase (NOD) enzymes, which facilitate a ·NO homeostatic process, i.e., its oxidation to the nitrate anion. Here, a discrete six-coordinate low-spin porphyrinate-FeIII complex [(PIm)FeIII(-OON═O)] (3) (PIm; a porphyrin moiety with a covalently tethered imidazole axial "base" donor ligand) has been identified and characterized by various spectroscopies (UV-vis, NMR, EPR, XAS, resonance Raman) and DFT calculations, following its formation at -80 °C by addition of ·NO(g) to the heme-superoxo species, [(PIm)FeIII(O2•-)] (2). DFT calculations confirm that 3 is a six-coordinate low-spin species with the PN ligand coordinated to iron via its terminal peroxidic anionic O atom with the overall geometry being in a cis-configuration. Complex 3 thermally transforms to its isomeric low-spin nitrato form [(PIm)FeIII(NO3-)] (4a). While previous (bio)chemical studies show that phenolic substrates undergo nitration in the presence of PN or PN-metal complexes, in the present system, addition of 2,4-di-tert-butylphenol (2,4DTBP) to complex 3 does not lead to nitrated phenol; the nitrate complex 4a still forms. DFT calculations reveal that the phenolic H atom approaches the terminal PN O atom (farthest from the metal center and ring core), effecting O-O cleavage, giving nitrogen dioxide (·NO2) plus a ferryl compound [(PIm)FeIV═O] (7); this rebounds to give [(PIm)FeIII(NO3-)] (4a).The generation and characterization of the long sought after ferriheme peroxynitrite complex has been accomplished.

Bioactive components and functional properties of biologically activated cereal grains: A bibliographic review.

Whole grains provide energy, nutrients, fibers, and bioactive compounds that may synergistically contribute to their protective effects. A wide range of these compounds is affected by germination. While some compounds, such as ß-glucans are degraded, others, like antioxidants and total phenolics are increased by means of biological activation of grains. The water and oil absorption capacity as well as emulsion and foaming capacity of biologically activated grains are also improved. Application of biological activation of grains is of emerging interest, which may significantly enhance the nutritional, functional, and bioactive content of grains, as well as improve palatability of grain foods in a natural way. Therefore, biological activation of cereals can be a way to produce food grains enriched with health-promoting compounds and enhanced functional attributes.