Nitrogen Incorporation into Lignite Humic Acids during Microbial Degradation

Previous study showed that nitrogen content in lignite humic acids (HA) increased significantly during lignite biodegradation. In this paper we evaluated the factors responsible for the increased level of N in HA and the formation of new nitrogen compound following microbial degradation. When the ammonium sulfate concentration in lignite medium was < 0.5%, the N-content in HA was higher than that in the crude lignite humic acid (cHA); when the ammonium sulfate concentration was ≥ 0.5%, both the biodegraded humic acid (bHA) N-content and the content of bHA in lignite increased significantly, but at 2.0% no increase was observed. This indicated that HA incorporated N existing in the lignite medium, and more HA can incorporate more N with the increase of bHA amount in lignite during microbial degradation. CP/MAS ¹⁵N NMR analysis showed that the N incorporated into HA during biotransformation was in the form of free or ionized NH₂-groups in amino acids and sugars, as well as NH₄ ⁺. We propose nitrogen can be incorporated into HA biotically and abiotically. The high N content bHA has a potential application in agriculture since N is essential for plant growth.     

Soil Washing Enhanced by Humic Substances and Biodegradable Chelating Agents

Industrial timber treatment sites have resulted in widespread soil contamination by Cu, Cr, and As, presenting potential long-term liability and associated risks to human health and the environment. This study evaluated the roles of natural humic substances (lignite-derived humic substances, standard and commercially available humic acids) and biodegradable chelating agents (ethylenediamine-N,N-disuccinic acid (EDDS) and glutamic-N,N-diacetic acid (GLDA)) for soil washing. Batch kinetic experiments revealed that humic substances promoted Cu extraction at pH 8, but they were significantly adsorbed on the soil at pH 4, possibly posing impediment to soil remediation. The metal extraction by EDDS and GLDA was comparable to that of EDTA (ethylenediamine-tetraacetic acid), and it was more effective at pH 4 than pH 8, probably due to acidic dissolution of metal precipitates and oxides. Metal distribution analysis indicated that the carbonate fraction of Cu and the oxide fraction of As and Cr were mainly extracted, while the exchangeable fraction of Cu increased. The residual leachability tests showed that humic substances reduced the Cu and As leachability but the reduction was insufficient. In contrast, EDDS was able to reduce the leachate concentrations of Cu and As to below 5 mg L^?1, meeting the waste acceptance criteria for landfill disposal. Nevertheless, soil washing methods and remediation strategy may need further modifications to facilitate site restoration and promote soil recycling.     

Seasonal and Spatial Overlap between Cladocerans in Humic Lakes

Seasonal and vertical distribution, migratory patterns and reproductive effort in coexisting cladocerans were investigated in three humic lakes with different, but low phytoplankton abundances and varying fish predation pressure. Seasonal and vertical habitat or niche overlap varied, but were high within most pairs of species in all localities. Migration was conspicuous in presence of planktivorous fish, less so in the fish free lake. Despite algal densities below incipient limiting level (30–200 μg C I⁻¹) and a low ratio (3–10) of algal to cladoceran biomass, zooplankton distribution and reproductive parameters were not clearly related to algal biomass. Bacterial biomass equalled 10–50% of phytoplankton biomass, while detritus by far was the largest of the particulate compartements. It was concluded that with a possible exception of the early summer algal bloom, additional carbon sources (bacteria, detritus) are important to cladoceran nutrition in these humic lakes. A large share of N- and P-poor detritus in the diet would give zooplankton productivity limitation by food quality in terms of elemental composition rather than food quantity. This would permit coexistence even of species with rather high food overlap, but give low production rates for all species in agreement with the observations.     

Comparison of Humic Substance- and Fe(III)-Reducing Microbial Communities in Anoxic Aquifers

Humic substances can mediate electron transfer between microorganisms and Fe(III) minerals. Because it is unknown which microorganisms reduce humics in anoxic aquifers, we analyzed the diversity and physiological flexibility of Fe(III)-, humics-, and AQDS-reducers, which were present at up to 10⁶ cells g^?1. No significant differences in 16S rRNA gene based diversity were found between enrichment cultures reducing ferrihydrite, humics or AQDS. Even after repeated transfers many of the enrichments retained the ability to switch to other electron acceptors. This suggests that humics- and Fe(III)-reducing microorganisms in anoxic aquifers are rather versatile and able to reduce different extracellular electron acceptors.     

Study on the Interaction Between Nucleic Acids and Imidacloprid and Its Application

The determination of imidacloprid with DNA via a resonance light scattering (RLS) technique was developed. The RLS of DNA was remarkably quenched after adding imidacloprid in aqueous medium of pH 2.10. An RLS peak at 311 nm was found, and the quenched intensity of RLS at this wavelength was proportional to the concentration of imidacloprid. The linear range of the calibration curve was approximately 0.02–2 μg/mL with the detection limit (S/N = 3) of 0.02 ng/mL. The imidacloprid in river water, cucumbers, and apple samples was determined. The recovery rates were in the range of 91.9% to 95.20%, 97.2% to 111.3%, and 94.5% to 114.8%, respectively. The mechanism of the reaction between imidacloprid and DNA is also discussed.     

Analysis of salicylic acid in willow barks and branches by an electrochemical method

An electrochemical method for measuring free salicylic acid (SA) was optimized and used to detect its content in barks and branches of thirteen Salix species. We utilized square wave voltammetry method in combination with pencil lead, the detection limit of which was 1.7 ng/ml of salicylic acid. The highest contents of free SA were observed in the bark of S. laponum (3.0 mg/g fr wt) and in the branches of S. purpurea, cv. Nana (2.1 mg/g fr wt) and S. planifolia (2.2 mg/g fr wt). The technique utilized for determination of SA in willow tissues has a much broader dynamic range and lower limit of detection in comparison to both linear sweep and cyclic voltammetry because of its efficient discrimination of capacitance current. Published in Russian in Fiziologiya Rastenii, 2007, Vol. 54, No. 4, pp. 623–628. The text was submitted by the authors in English.     

Interaction between humic substances and carbohydrates in a Pampasic pond (Argentina)

Interaction between humic substances from a Pampasic pond and carbohydrates was studied. Determinations were performed by gel chromatography using radiolabeled glucose. The results showed that upon lowering the pH the interaction decreases in relation to the steric arrangement that causes the diminution of the accessibility of the available sites. Results of displacement experiments carried out by addition of unlabeled glucose, galactose, saccharose and starch, confirmed that the interaction occurs mainly through labile non specific bonds and is, to a certain degree, independent of the carbohydrate molecular weight involved. This revised version was published online in July 2006 with corrections to the Cover Date.     

芦丁与人血清白蛋白相互作用的紫外可见光谱特性研究

本文通过测定芦丁与HSA相互作用前后的紫外可见吸收光谱、圆二色性及人血清白蛋白(HSA)的荧光特性,研究了芦丁与HSA结合作用。结果表明,芦丁在紫外区有三个特征的吸收峰(264.0、285.5及354.5nm)、在330～300 nm及300～230 nm处显示圆二色性,HSA引起芦丁紫外可见吸收光谱波峰红移;芦丁与HSA相互作用后,不引起HSA二级结构的改变,但对其三级结构有影响,同时对HSA荧光激发及发生光谱最大峰位及幅度有影响。     

Synthesis, structural, spectroscopic and thermal characterization of cobalt complexes with 3- and 6-methylpicolinic acid. Voltammetric and spectrophotometric study in solution

Cobalt complexes of 3- and 6-methylpicolinic acid, namely [Co(3-Mepic)₃] (1) and [Co(6-Mepic)₂(H₂O)₂] · 2H₂O (2) were prepared and characterized by spectroscopic methods (IR, UV-Vis, NMR), their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA/DTA methods. Square-wave voltammetry showed that on mercury electrode the oxidation of 2 requires higher potential than the oxidation of complex anion [Co(3-Mepic)₃]⁻, the most probable product of the reduction of 1. The reduction of 1 and the oxidation of 2 depend on the kinetics of electron transfer and the electrode material. X-ray structural analysis revealed octahedral coordination polyhedron in both 1 and 2 and the same N,O-chelated coordination mode for both ligands. ¹³C, ¹H and ¹⁵N NMR spectroscopy confirmed that coordination mode of 3-methylpicolinic acid in 1 in DMSO solution. UV-Vis spectrophotometric measurements were used to study the complexation of cobalt with 3- and 6-methylpicolinic acid in aqueous solution and to determine the composition of the formed complexes by Job method of continuous variation. The stoichiometry of the complex with 3-methylpicolinic acid is 2:3, while it is 2:3 and 3:2 for the complex with 6-methylpicolinic acid, indicating the possibility of the formation of more than one complex species.     

Utilization of Uniformly Labeled 13C-Polyunsaturated Fatty Acids in the Synthesis of Long-Chain Fatty Acids and Cholesterol Accumulating in the Neonatal Rat Brain

Abstract: Polyunsaturated fatty acids are needed for normal neonatal brain development, but the degree of conversion of the 18-carbon polyunsaturated fatty acid precursors consumed in the diet to their respective 20-and 22-carbon polyunsaturates accumulating in the brain is not well known. In the present study, in vivo ¹³C nuclear magnetic resonance spectroscopy was used to monitor noninvasively the brain uptake and metabolism of a mixture of uniformly ¹³C-enriched 16-and 18-carbon polyunsaturated fatty acid methyl esters injected intragastrically into neonatal rats. In vivo NMR spectra of the rat brain at postnatal days 10 and 17 had larger fatty acid signals than in uninjected controls, but changes in levels of individual fatty acids could not be distinguished. One day after injection of the U-¹³C-polyunsaturated fatty acid mixture, ¹³C enrichment (measured by isotope ratio mass spectrometry) was similar in brain phospholipids, free fatty acids, free cholesterol, and brain aqueous extract; ¹³C enrichment remained high in the phospholipids and cholesterol for 15 days. ¹³C enrichment was similar in the main fatty acids of the brain within 1 day of injection but 15 days later had declined in all except arachidonic acid while continuing to increase in docosahexaenoic acid. These changes in ¹³C enrichment in brain fatty acids paralleled the developmental changes in brain fatty acid composition. We conclude that, in the neonatal rat brain, dietary 16-and 18-carbon polyunsaturates are not only elongated and desaturated but are also utilized for de novo synthesis of long-chain saturated and monounsaturated fatty acids and cholesterol.     

Interaction between glutamate dehydrogenase (GDH) and L-leucine catabolic enzymes: intersecting metabolic pathways

Branched-chain amino acids (BCAAs) catabolism follows sequential reactions and their metabolites intersect with other metabolic pathways. The initial enzymes in BCAA metabolism, the mitochondrial branched-chain aminotransferase (BCATm), which deaminates the BCAAs to branched-chain α-keto acids (BCKAs); and the branched-chain α-keto acid dehydrogenase enzyme complex (BCKDC), which oxidatively decarboxylates the BCKAs, are organized in a supramolecular complex termed metabolon. Glutamate dehydrogenase (GDH1) is found in the metabolon in rat tissues. Bovine GDH1 binds to the pyridoxamine 5′-phosphate (PMP)-form of human BCATm (PMP-BCATm) but not to pyridoxal 5′-phosphate (PLP)-BCATm in vitro. This protein interaction facilitates reamination of the α-ketoglutarate (αKG) product of the GDH1 oxidative deamination reaction. Human GDH1 appears to act like bovine GDH1 but human GDH2 does not show the same enhancement of BCKDC enzyme activities. Another metabolic enzyme is also found in the metabolon is pyruvate carboxylase (PC). Kinetic results suggest that PC binds to the E1 decarboxylase of BCKDC but does not effect BCAA catabolism. The protein interaction of BCATm and GDH1 promotes regeneration of PLP-BCATm which then binds to BCKDC resulting in channeling of the BCKA products from BCATm first half reaction to E1 and promoting BCAA oxidation and net nitrogen transfer from BCAAs. The cycling of nitrogen through glutamate via the actions of BCATm and GDH1 releases free ammonia. Formation of ammonia may be important for astrocyte glutamine synthesis in the central nervous system. In peripheral tissue association of BCATm and GDH1 would promote BCAA oxidation at physiologically relevant BCAA concentrations.     

Structural similarities and differences between H1- and H2-family DNA minihairpin loops: NMR studies of octameric minihairpins

TheDNA sequences 5′-d(CGC-AC-GCG)-3′ (HPAC), 5′-d(CGC-AA-GCG)-3′ (HPAA), 5′-d(CGC-TC-GCG)-3′ (HPTC), and 5′-d(CGC-CT-GCG)-3′ (HPCT), were studied by means of nmr spectroscopy. At low DNA concentration and no added salt all four molecules adopt a minihairpin structure, containing three Watson–Crick base pairs and a two-residue loop. The structure of the HPAC hairpin is based on quantitative distance restraints, derived by a full relaxation matrix approach (iterative relaxation matrix approach), together with torsion angles obtained from coupling constant analysis. The loop folding is of the H1-family type, characterized by continuous 3′-5′ stacking of the loop bases on the duplex stem. The structure of the HPAA hairpin is similar to that of HPAC, but is more flexible and has a lower thermodynamic stability (T_m 326 K vs 320 K). According to “weakly” distance-constrained simulations in water on the HPAC minihairpin, the typical H1-family loop folding remains intact during the simulation. However, residue-based R factors of simulated nuclear Overhauser effect spectroscopy spectra, free molecular dynamics simulations in vacuo, and unusual chemical shift profiles indicate partial destacking of the loop bases at temperatures below the overall melting midpoint. The dynamic nature of the loop bases gives insight into the geometrical tolerances of stacking between bases in H1-family minihairpin loops. The HPTC and HPCT minihairpins, both containing a pyrimidine base at the first position in the loop, adopt a H2-family type folding, in which the first loop base is loosely bound in the minor groove and the second loop base is stacked upon the helix stem. The thermal stability for these two hairpins corresponds to 327–329 K, but depends on local base sequence. Preference for the type of folding depends on a single substitution from a pyrimidine (H2 family) to a purine (H1 family) at the first position of the miniloop and is explained by differences in base stacking energies, steric size, and the number of possible candidates for hydrogen bonds in the minor groove. In view of newly collected data, previous models of the H1-family and H2-family hairpins had to be revised and are now compatible with the reported HPTC and HPAC structures. The structural difference between the refined structure of HPAC and HPTC show that a conversion between H1-family and H2-family hairpins is geometrically possible by a simple pivot point rotation of 270° along two torsion angles, thereby swiveling the first loop base from a stacked position in a H1-family folding toward a position in the minor groove in a H2-family folding. The second loop residue subsequently shifts to the position of the first base in a concerted fashion. © 1998 John Wiley & Sons, Inc. Biopoly 46: 375–393, 1998     

Solid-phase 31P NMR spectra of peat and mineral soils,humic acids and soil solution components: influence of iron and manganese

Solid-phase³¹P nuclear magnetic resonance (NMR) offers a direct means to determine the chemical environment of P present in soil and soil fractions. Iron is often a major component in soil and it has been thought that the presence of paramagnetic Fe and Mn in soil components is responsible for loss of resolution in NMR spectra. We have found that the resolution of signals in the solid-phase ³¹P NMR spectra of a Fe- and Mn-rich mineral soil was no worse than that for a series of four peat soils with a comparable concentration of P. Similarly, the resolution in the solid-phase ³¹P NMR spectra of the humic acid from the mineral soil was not much changed by extraction of the humic acid with acetylacetone in diethyl ether which removed around 40% of its Fe and 30% of its Mn. Removal of up to 50% of the Fe from organic rich, freeze-dried soil solutions from a soil catena with different land uses produced little change in spectral resolution. It was concluded that the limitations to resolution in solid-phase ³¹P NMR spectroscopy of soil humic substances do not stem from the presence of paramagnetic substances, but from the variable way P species are physically held in the amorphous milieu of the organic phase. This revised version was published online in June 2006 with corrections to the Cover Date.     

Structural differences between ribosomes of various eukaryotes: stability, density, mass, size and structure in solution of cytoplasmic ribosomes from Tetrahumena, Artemia and Euglena

Cytoplasmic ribosomal particles were isolated from the ciliated protozoa Tetrahymena pyriformis, the brine shrimp Artemia, and the flagellated alga Euglena gracilis; their stability, density, mass, size and structure in solution have been compared in identical conditions. The small and in particular the large subunits of Euglena ribosomes were less stable than the corresponding particles of the other eukaryotes. Equilibrium centrifugation of the ribosomes of the various species in CsCl density gradients revealed no difference in either their homogeneity or their buoyant density; so no differences were detected in this way in the ratio of their RNA to protein content or in their partial specific volume. Using analytical boundary sedimentation, the sedimentation coefficients s_20,w⁰ of the whole ribosomes were measured to be 81, 81 and 86 S, respectively. Photon correlation spectroscopy of laser light scattered by the whole ribosomes has yielded values for their diffusion coeffcient D_20,w⁰) of 1.51, 1.42 and 1.29 × 10⁻⁷ cm² s⁻¹, respectively; this corresponds to values for their hydrodynamic radius of 142, 151 and 166 Å, respectively. The data indicate also that the solvation of the ribosomes increases with their size and mass.So evidence has been obtained for differences in the size of various eukaryotic ribosomes, and even in the degree of compactness of their structure in solution.     

Interaction between the actions of taurine and angiotensin II

Summary. The amino acid, taurine, is an important nutrient found in very high concentration in excitable tissue. Cellular depletion of taurine has been linked to developmental defects, retinal damage, immundeficiency, impaired cellular growth and the development of a cardiomyopathy. These findings have encouraged the use of taurine in infant formula, nutritional supplements and energy promoting drinks. Nonetheless, the use of taurine as a drug to treat specific diseases has been limited. One disease that responds favorably to taurine therapy is congestive heart failure. In this review, we discuss three mechanisms that might underlie the beneficial effect of taurine in heart failure. First, taurine promotes natriuresis and diuresis, presumably through its osmoregulatory activity in the kidney, its modulation of atrial natriuretic factor secretion and its putative regulation of vasopressin release. However, it remains to be determined whether taurine treatment promotes salt and water excretion in humans with heart failure. Second, taurine mediates a modest positive inotropic effect by regulating [Na⁺]_i and Na⁺/Ca²⁺ exchanger flux. Although this effect of taurine has not been examined in human tissue, it is significant that it bypasses the major calcium transport defects found in the failing human heart. Third, taurine attenuates the actions of angiotensin II on Ca²⁺ transport, protein synthesis and angiotensin II signaling. Through this mechanism taurine would be expected to minimize many of the adverse actions of angiotensin II, including the induction of cardiac hypertrophy, volume overload and myocardial remodeling. Since the ACE inhibitors are the mainstay in the treatment of congestive heart failure, this action of taurine is probably very important. Received November 10, 1998, Accepted May 19, 1999     

Interaction between aromatic antibiotics and vitamins: 1H NMR study of heteroassociation of nicotinamide and anthracycline antitumor antibiotics

The interaction of the anthracycline antitumor antibotics daunomycin and novatrone with the vitamin nicotinamide has been studied by one-and two-dimensional ¹H NMR (500 MHz). Due to significant differences between the structures of the chromophores of interacting molecules, a two-site heteroassociation model has been developed, which implies the binding of one or several nicotinamide molecules to the chromophore of the antibiotic. The structural and thermodynamic parameters of the heteroassociation of nicotinamide with daunomycin and novatrone have been determined from the experimental concentration and temperature dependences of the ¹H NMR chemical shifts of the interacting molecules. The most favorable structures of the 1:1 nicotinamide-daunomycin and nicotinamide-novatrone heterocomplexes have been found using the molecular mechanics method (X-PLOR software) and analysis of induced proton chemical shifts. The results demonstrate that two nicotinamide molecules cannot simultaneously bind on one side of the chromophore of the daunomycin or novatrone. The 1:1 heterocomplexes of the vitamin with the antibiotics are mainly stabilized by the stacking of aromatic chromophores.     

Interrelations between the Nucleotide Context of Human Start AUG Codon,N-end Amino Acids of the Encoded Protein and Initiation of Translation

Abstract

It is known that the recognition of AUG triplet by eukaryotic ribosomes as a translation start site strongly depends on its nucleotide context. However, the relative significance of different context positions is not fully clear. In particular, it concerns the role of 3′-end part of the context located at the beginning of the protein-coding sequence. The significant bias observed in nucleotide frequencies in positions +4, +5, +6 (corresponding to the second codon of CDS) could result from different reasons and their contribution to start codon recognition and initiation of translation is under discussion. In this study, we conducted a comparative computational analysis of the human mRNA samples containing different nucleotides (adenine, guanine or pyrimidine) in the essential context position ?3. It was found that the presence of G in position +4 could be important for the context variant GnnAUG but not for AnnAUG. Interestingly, the second position of proteins encoded by mRNAs with AnnAUG context variant was specifically and significantly enriched with serine whereas the presence of GnnAUG context also correlated with a higher occurrence of alanine and glycine. It is likely that the efficiency of translation initiation process can depend on the interplay between 5′-context part, 3′-context part and the type of amino acid in the second position of the encoded protein.     

Relationships between 4-Hydroxy-2-nonenal, 2-Thiobarbituric Acid Reactive Substances and n-6 Polyunsaturated Fatty Acids in Refrigerated and Frozen Pork

The relationships between 4-hydroxy-2-nonenal (HNE), 2-thiobarbituric acid reactive substances (TBARS) and n-6 polyunsaturated fatty acids (n-6 PUFAs) were investigated for pork stored at 0, -20 and -80°C. A significant linear correlation was apparent between HNE and TBARS for the pork stored at each temperature. However, the n-6 PUFA content remained unchanged during storage.     

从人和动物血浆及红细胞膜脂肪酸谱探讨脂质代谢实验模型动物选取

目的比较大鼠、家兔和人血浆及红细胞膜脂肪酸谱的异同,为脂质代谢模型动物的选取提供可靠依据。方法采用氯仿-甲醇快速提取大鼠、家兔和人血浆及细胞膜中的脂肪,并用碱法甲基化,经薄层层析纯化的甲基酯用100 mm×0.25 mm气相色谱毛细管柱测定脂肪酸组成。结果血浆中总MUFA、9c18：1、9c12c18：2 n-6和α-18：3 n-3等脂肪酸含量较高;而红细胞膜中总PUFA、AA、22：4n-6、DPA和DHA等脂肪酸含量较高;人和大鼠16：0、18：0、18：1、α-18：3n-3、AA、EPA、DHA、MUFA、n-3PUFA和n-6/n-3值均较为接近,但和家兔存在显著差异。结论与家兔相比,大鼠和人血浆及红细胞膜脂肪酸谱较接近,因此,在选取脂质代谢实验动物时,应优先考虑大鼠为模型动物,以得到与人体实际更接近的结果。