Anthocyanin pathway in rice (Oryza sativa L): identification of a mutant showing dominant inhibition of anthocyanins in leaf and accumulation of proanthocyanidins in pericarp

The present study has surveyed a collection of indica rice (Oryza sativa) lines for tissue-specific anthocyanin pigmentation pattern, which has also been used for a genetically meaningful classification. This classification helped predict probable genotypes of rice lines and, in the process, a leaf blade-specific dominant inhibitor of pigmentation (Ilb) was predicted and its presence later confirmed in two lines. We ascribe most tissue-specific accumulation of anthocyanins to the presence of a different set of Pl alleles. Cyanidin, as a major pigment, and peonidin, as a minor pigment, were detected in purple-pigmented tissues. Further, the floral organ-derived tissues always contained a higher level of anthocyanins and, correspondingly, a relatively increased proportion of peonidin. One line, N22B, with a brown pericarp was identified and shown to accumulate proanthocyanidins, but with no anthocyanins, in the pericarp. We propose that the accumulation of proanthocyanidins is due to a block in the anthocyanin biosynthetic pathway in rice at the anthocyanidin synthase-mediated conversion of leucoanthocyanidin to anthocyanidin.     

Haemanalysis: The relative astringency of proanthocyanidin polymers

Effects of MW, stereochemistry of monomer units, and B-ring oxidation pattern on relative astringency were studied. Efficiency of protein precipitation is primarily a function of proanthocyanidin polymer (condensed tannin) size and whereas oligomeric proanthocyanidins have a relative astringency less than tannic acid, polymeric proanthocyanidins of sufficiently high average MW (M_n～2500) are equally as efficient at precipitating haemoglobin.     

Methylation of anthocyanins by cell-free extracts of flower buds of Petunia hybrida

An O-methyltransferase activity which catalyses the methylation of anthocyanins was extracted from flowerbuds of Petunia hybrida. The methyltransferase uses S-adenosyl-l-methionine as methyl donor. Only anthocyanidin 3(p-coumaroyl)rutinosido-5-glucoside was methylated. No methylating activity towards anthocyanidins, anthocyanidin 3-glucosides, anthocyanidin 3-rutinosides, caffeic acid or p-coumaric acid could be detected.     

Association between melanopsin gene polymorphism (I394T) and pupillary light reflex is dependent on light wavelength

Background

Our aim was to determine the association between melanopsin gene polymorphism and pupillary light reflex under diverse photic conditions, including different intensities and wavelengths.

Methods

A total of 195 visually corrected subjects volunteered for investigation of the melanopsin gene of single nucleotide polymorphism (SNP) of rs1079610 (I394T). The genotype groups were TT (n = 126), TC (n = 55), and CC (n = 8), and 75 of the subjects, including subjects with TT (n = 34), TC (n = 33), and CC (n = 8) participated in our experiment. Three monochromatic lights with peak wavelengths of 465 nm (blue), 536 nm (green), and 632 nm (red) were prepared, and each light was projected to the subjects with five intensities, 12, 13, 14, 14.5 and 15 log photons/(cm² s), for one minute. The pupil size of the left eye was measured under each light condition after a 1-minute adaptation.

Results

The pupils of the TC + CC genotypes (n = 38) were significantly smaller than those of the TT genotype (n = 31) under a blue (463 nm) light condition with 15 log photons/(cm² s) (P < 0.05). In contrast, there were no significant differences under green (536 nm) and red (632 nm) light conditions. Conversely, relative pupil constrictions of the TC + CC genotypes were greater than those of the TT genotype under both blue and green conditions with high intensities (14.5 and 15 log photons/(cm² s)). In contrast, there were no significant differences between genotype groups in pupil size and relative pupilloconstriction under the red light conditions.

Conclusions

Our findings suggest that the melanopsin gene polymorphism (I394T) functionally interacts with pupillary light reflex, depending on light intensity and, particularly, wavelength, and that under a light condition fulfilling both high intensity and short wavelength, the pupillary light response of subjects with the C allele (TC + CC) is more sensitive to light than that of subjects with the TT genotype.     

Intramolecular electron transfer in the mixed-valence [Co(3,5-DTBCat)(3,5-DTBSQ)(bpy)] complex: Beyond valence tautomerism

The series of complexes [Co(Q)₂(bpy)]ⁿ (n = ?1, 0, +1) that can be derived by partial reduction or oxidation of complex 1, ls-Co(III) has been synthesized and studied. The results support the theoretical calculations which pointed to an intervalence transfer (IT) from the Cat^2? to the SQ^? ligand rather than a LMCT transition as the origin for the low-energy band transition centered at 2500 nm observed for 1, ls-Co(III).     

Anthocyanins and anthocyanidins in the flowers of Aconitum (Ranunculaceae)

The presence of anthocyanidins and anthocyanins were analyzed in flowers of 30 taxa of Aconitum. Delphinidin was detected as a major anthocyanidin from the hydrolysate of 29 taxa with violet and violet-blue flowers. Pelargonidin was identified as a major anthocyanidin in one taxon with white flowers (partially pale reddish purple; White group N155C by R.H.S. Colour Chart). This is the first reported detection of pelargonidin as a major anthocyanidin from Aconitum flowers. Pelargonidin was also found in ten taxa as a minor anthocyanidin, whereas cyanidin was detected from the flowers of all 30 taxa as a minor anthocyanidin.Two anthocyanins polyacylated by p-hydroxybenzoic acids, violdelphin and monodeacylcampanin were identified from 29 taxa with violet and violet-blue flowers as major anthocyanins. This is the first reported isolation of monodeacylcampanin from Aconitum flowers. The structures of these two anthocyanins were elucidated on the basis of Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS).     

Hyaluronic acid: a double-helical structure in the presence of potassium at low pH and found also with the cations ammonium, rubidium and caesium.

An anti-parallel double-helical structure is proposed for hyaluronic acid in the presence of the cations K ⁺, NH⁺₄, Rb⁺ and Cs⁺. In particular the crystalline phase containing potassium ions, and in a defined pH range, has been determined and refined against the X-ray diffraction amplitudes. The reflections in the diffraction pattern index on a tetragonal unit cell (a = b = 1.714 nm, c (fibre axis) = 3.28 nm) with observed systematic absences of the form h + k + l = 2n for general hkl reflections and l = 4n (where n is an integer) for 001 reflections. Two double-helical molecules pass through the unit cell at positions ($\text{1}\text{4}\text{,}\text{1}\text{4}\text{, 0}$) and ($\text{3}\text{4}\text{,}\text{3}\text{4}\text{, 0}$) as defined by space group I4₁22. Each chain forms a contracted (axial advance per disaccharide repeat of 0.82 nm) 4-fold left-handed helix which intertwines with a neighbouring chain of opposite polarity about a common axis. Features of the structure are the positioning of the carboxyl group toward the core of the double helix and the presence of hydrophobic and hydrophilic pockets between adjacent double helices. The state of protonation of the hyaluronate molecule is discussed in the light of the infrared evidence. Common physicochemical features of these four cations which promote this particular doublehelical conformation for hyaluronate are considered.     

Procyanidin B2 catabolism by human fecal microflora: Partial characterization of ‘dimeric’ intermediates

The catabolism by human fecal microflora of pure procyanidin B2 ((-)-epicatechin-4β → 8-(-)-epicatechin) has been investigated using a static in vitro culture model. For the first time, 24 catabolites were detected by LC-MS⁽ⁿ⁾ with M_r greater than 290 indicating that they could not have formed from just one of the epicatechin units in the procyanidin structure. Structures have been assigned on the basis of the fragmentation in the ion trap mass spectrometer and with regard to catabolic pathways known to occur in fecal microorganisms. Twenty of these ‘dimeric’ catabolites produced fragment ions characteristic of flavanols and/or proanthocyanidins. One catabolite was identified tentatively as either 6- or 8-hydroxy-procyanidin B2. Thirteen were characterized as having been microbially reduced in at least one of the epicatechin units. Five contained an apparently unmodified epicatechin unit but in at least one case this was shown to consist of the B-ring of the “upper” epicatechin unit and the A-ring of the “lower”. These ‘dimeric’ catabolites were detected up to 9 h after the start of the incubation and collectively accounted for ∼20% of the substrate.     

Mutation of His465 Alters the pH-dependent Spectroscopic Properties of Escherichia coli Glutamate Decarboxylase and Broadens the Range of Its Activity toward More Alkaline pH

Glutamate decarboxylase (GadB) from Escherichia coli is a hexameric, pyridoxal 5′-phosphate-dependent enzyme catalyzing CO₂ release from the α-carboxyl group of l-glutamate to yield γ-aminobutyrate. GadB exhibits an acidic pH optimum and undergoes a spectroscopically detectable and strongly cooperative pH-dependent conformational change involving at least six protons. Crystallographic studies showed that at mildly alkaline pH GadB is inactive because all active sites are locked by the C termini and that the 340 nm absorbance is an aldamine formed by the pyridoxal 5′-phosphate-Lys²⁷⁶ Schiff base with the distal nitrogen of His⁴⁶⁵, the penultimate residue in the GadB sequence. Herein we show that His⁴⁶⁵ has a massive influence on the equilibrium between active and inactive forms, the former being favored when this residue is absent. His⁴⁶⁵ contributes with n ≈ 2.5 to the overall cooperativity of the system. The residual cooperativity (n ≈ 3) is associated with the conformational changes still occurring at the N-terminal ends regardless of the mutation. His⁴⁶⁵, dispensable for the cooperativity that affects enzyme activity, is essential to include the conformational change of the N termini into the cooperativity of the whole system. In the absence of His⁴⁶⁵, a 330-nm absorbing species appears, with fluorescence emission spectra more complex than model compounds and consisting of two maxima at 390 and 510 nm. Because His⁴⁶⁵ mutants are active at pH well above 5.7, they appear to be suitable for biotechnological applications.     

Extracellular biosynthesis of silver nanoparticles: effects of shape-directing cetyltrimethylammonium bromide,pH, sunlight and additives

The work reported in this paper describes the preparation, morphology, stability and sensitivity of Ag-nanoparticles towards sunlight using Allium sativum, garlic extract for the first time. The synthesized silver particles show an intense surface plasmon resonance band in the visible region at 410 nm. The position of the wavelength maxima, blue and red shift, strongly depends on the sunlight and pH. TEM analysis revealed the presence of spherical, different size (from 5.0 to 30 nm) and garlic constituents bio-conjugated, stabilized and/or layered silver nanoparticles. The concentrations of garlic extract, cetyltrimethylammonium bromide, Ag⁺ ions and reaction time play vital roles for nucleus formation and the growth processes. Sulfur-containing biomolecules of extract, especially cysteine, are responsible for the reduction of Ag⁺ ions into metallic Ag⁰. The agglomeration number of the silver nanoparticles (N _Ag) and the average number of free electrons per particle (n _fe) are calculated and discussed.     

Syntheses, structures, and photoluminescent properties of four d metal-quinolinato coordination polymers with similar rod-like SBUs

Four M^II quinolinato complexes, [Zn₂(quin)₂(H₂O)₃]_n (1), [Zn(quin)(H₂O)₂]_n (2), [Zn(quin)(H₂O)]_n (3) and [Cd(quin)]_n (4) (H₂quin = 2,3-pyridinedicarboxylic acid or quinolinic acid), have been hydrothermally synthesized and structurally characterized. X-ray diffraction analyses reveal that all of these four complexes are constructed from similar rod-like SBUs, [M(quin)]_n (M = Zn or Cd). Complexes 1 and 2 have similar 1-D box-like chains but different packing structures; complex 3 has a 2-D grid-like network and complex 4 has an unusual 2-D bilayer structure. Due to the different structural features, these complexes exhibit different photoluminescent emissions: complex 1 at 439 nm (λ_ex = 345 nm), complex 2 at 428 nm (λ_ex = 360 nm), complex 3 at 508 nm (λ_ex = 304 nm) and complex 4 at 500 nm (λ_ex = 324 nm).     

Distribution pattern of anthocyanidins and anthocyanins in polygonaceous plants

Forty-six polygonaceous plants were examined regarding the nature and amount of anthocyanidins which were obtained as the HCl-hydrolyzate of leaf proanthocyanidins. All of the plants examined contained cyanidin in common in their hydrolyzed leafextracts. From this survey, at least three groups of plants may be distinguished; the first containing only cyanidin, the second delphinidin in addition to cyanidin and the third an unknown anthocyanidin (called PA-X) and cyanidin. Of the plants examined,Polygonum cuspidatum leaves yielded cyanidin in the largest amounf. There were no geographical and seasondl variations of the distribution pattern of pigments in the plants, and also no variation of anthocyanidin-types was observed in young and mature leaves. A further survey of anthocyanins in the plants revealed that delphinidin glycosides are present in the sepals ofPolygonum nepalense andP. thunbergii.     

Biosynthetic origin of the saw-toothed profile in δC and δΗ of n-alkanes and systematic isotopic differences between n-, iso- and anteiso-alkanes in leaf waxes of land plants

The n-fatty acids containing an even number of carbons (ECN-n-FAs) in higher plants are biosynthesised by repetitive addition of a two carbon unit from malonyl-ACP. The n-alkanes containing an odd number of carbon atoms (OCN-n-alkanes) are generally formed by the decarboxylation of ECN-n-FAs, but it is unknown how the less abundant even-carbon-numbered alkanes (ECN-n-alkanes) are biosynthesised in higher plants.There is a distinctive compositional pattern of incorporation of stable carbon (¹³C) and hydrogen (²H) isotopes in co-existing ECN- and OCN-n-alkanes in leaves of higher plants, such that the OCN n-alkanes are relatively enriched in ¹³C but relatively depleted in ²H against the ECN-n-alkanes. This is consistent with the OCN-n-fatty acids having a propionate precursor which is derived from reduction of pyruvate. A tentative pathway is presented with propionate produced by enzymatic reduction of pyruvate which is then thio-esterified with CoSH (coenzyme A thiol) in the chloroplast to form the terminal precursor molecule propionyl-CoA. This is then repetitively extended/elongated with the 2-carbon unit from malonyl-ACP to form the long chain OCN-n-fatty acids.The anteiso- and iso-alkanes in Nicotiana tabacum leaf waxes have previously been found to be systematically enriched in ¹³C compared with the n-alkanes by Grice et al. (2008). This is consistent with the isotopic composition of their putative respective precursors (pyruvate as precursor for n-alkanes, valine for iso-alkanes and isoleucine for anteiso-alkanes). The current study complements that of Grice et al. (2008) and looks at the distribution of hydrogen isotopes. The n-alkanes were found to be more enriched in deuterium (²H) than the iso-alkanes which in turn were more enriched than the anteiso-alkanes. We propose therefore that the depletion of ²H in the iso-alkanes, relative to the n-alkanes is the consequence of accepting highly ²H-depleted hydrogen atoms from NADPH during their biosynthesis. The anteiso-alkanes are further depleted again because there are three NADPH-derived hydrogen atoms in their precursor isoleucine, as compared with only one NADPH-derived hydrogen in valine, the precursor of the iso-alkanes.     

Proanthocyanidins Extracted from Rhododendron pulchrum Leaves as Source of Tyrosinase Inhibitors: Structure,Activity, and Mechanism

The objective of this study was to assess the structure, anti-tyrosinase activity, and mechanism of proanthocyanidins extracted from Rhododendron pulchrum leaves. Results obtained from mass spectra of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and high performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS) revealed that proanthocyanidins were complex mixtures of procyanidins, prodelphinidins, propelargonidins, and their derivatives, among which procyanidins were the main components. The anti-tyrosinase analysis results indicated that the mixtures were reversible and mixed competitive inhibitors of tyrosinase. Interactions between proanthocyanidins with substrate (L-tyrosine and 3,4-dihydroxyphenylalanine) and with copper ions were the important molecular mechanisms for explaining their efficient inhibition. This research would provide scientific evidence for the use of R. pulchrum leaf proanthocyanidins as new novel tyrosinase inhibitors.     

Probing the electronic structures and properties of neutral and charged arsenic sulfides (As n S(−1,0,+1), n = 1–7) using Gaussian-3 theory

The structures and energies of neutral and charged arsenic sulfides As _n S^(?1,0,+1) (n?=?1–7) were systematically investigated using the G3 method. The bonding properties and the stabilities of As _n S and their ions were discussed. The adiabatic electron affinities (AEAs) and adiabatic ionization potentials (AIPs) were presented. The ground-state structures of As _n S can be considered as the lowest-energy structure of neutral As _n+1 by replacing an As atom with a S atom, that is, “substitutional structure”, in which the feature of sulfur bonding is edge-bridging. The ground-state structures of As _n S⁺ tend to be derived from the lowest-energy structure of cation As _n ⁺ by attaching to a S atom, that is, “attaching structure”, in which the sulfur can be three-fold coordinated. There is no rule to be found for the ground-state structure of anion As _n S^?, in which the sulfur can be a terminal atom. There are odd-even alternations in both AEAs and AIPs as a function of size of As _n S. The dissociation energies of S, S^?, and/or S⁺ from neutral As _n S and their ions were calculated to examine their stabilities.     

Prediction of rumen degradability parameters of a wide range of forages and non-forages by NIRS

Kinetics of nutrient degradation in the rumen is an important component of feed evaluation systems for ruminants. The in situ technique is commonly used to obtain such dynamic parameters, but it requires cannulated animals and incubations last several days limiting its application in practice. On the other hand, feed industry relies strongly on NIRS to predict chemical composition of feeds and it has been used to predict nutrient degradability parameters. However, most of these studies were feedstuff specific, predicting degradability parameters of a particular feedstuff or category of feedstuffs, mainly forages or compound feeds and not grains and byproducts. Our objective was to evaluate the potential of NIRS to predict degradability parameters and effective degradation utilizing a wide range of feedstuffs commonly used in ruminant nutrition. A database of 809 feedstuffs was created. Feedstuffs were grouped as forages (FF; n=256), non-forages (NF; n=539) and of animal origin (n=14). In situ degradability data for dry matter (DM; n=665), CP (n=682) and NDF (n=100) were collected. Degradability was described in terms of washable fraction (a), slowly degradable fraction (b) and its rate of degradation (c). All samples were scanned from 1100 to 2500 nm using an NIRSystems 5000 scanning in reflectance mode. Calibrations were developed for all samples (ALL), FF and NF. Equations were validated with an external validation set of 20% of total samples. NIRS equations to predict the effective degradability and fractions a and b of DM, CP and NDF could be evaluated from being adequate for screening (r²>0.77; ratio of performance to deviation (RPD)=2.0 to 2.9) to suitable for quantitative purposes (r²>0.84; RPD=3.1 to 4.7), and some predictions were improved by group separation reducing the standard error of prediction. Similarly, the rate of degradation of CP (CP_c) and DM (DM_c) was predicted for screening purposes (RPD⩾2 and 2.5 for CP_c and DM_c, respectively). However, the rate of degradation of NDF was not predicted accurately (NDF_c: r²<0.75; RDP<2).     

Conformational studies on poly(N-δ-trimethyl-l-ornithine)

$\text{Poly}\text{(N-δ-}\text{trimethyl-}\text{l}\text{-ornithine}$), (Me₃Orn)_n, is usually not able to attain the α-helical conformation in aqueous solution independent of its pH value; however, it becomes α-helical at low concentrations of sodium perchlorate over a wide pH range according to the circular dichorism (c.d.) spectra. Cl^?, SO₄^2? and H₂PO₄^? do not induce α-helix formation. One can conclude that a distinct topology of the anions bound by the side chains is responsible for the α-helix-inducing effect of some water-structure-breaking anions such as perchlorate. This means that the anions are inserted between the ?N⁺ of the side groups shielding the positive charges repelling one another. The insertion of the anions requires that the water molecules surrounding the ions can be stripped off, which is easily possible if they are water-structure-breaking ones. At higher perchlorate concentrations, the c.d. spectrum changes. It is characterized by a negative shoulder near 208 nm and a pronounced minimum at ≈ 226 nm. With increasing temperature, the c.d. spectrum of the α-helix occurs. Finally the α-helix undergoes a conformational change to the random coil. The apparent transition enthalpy ΔH_vH is remarkably lower than that of the homologue (Me₃Lys)_n, obviously due to a lower cooperativity of the transition. In contrast to poly(l-ornithine), (Orn)_n, the c.d. spectrum of (Me₃Orn)_n remains almost unchanged after adding anionic surfactants such as sodium octyl sulphate (SOS) or sodium dodecyl sulphate (SDS). In organic solvents like methanol or isopropanol, in contrast to (Orn)_a and (Lys)_n, no α-helix formation occurs. However, in mixtures of these alcohols or dioxane with water, α-helix formation is induced by perchlorate, as in pure water. The thermal stability of the α-helix in these systems is increased.