灵芝孢子粉中氨基酸和微量元素的分析

本文用氨基酸自动分析仪测定了灵芝孢子粉中的19种氨基酸,其总含量为7.20g/100g,其中牛磺酸(含0.02g/100g)为作者首次测得。我们还用电感耦合等离子体发射光谱法(ICP-AES法)测定了灵芝孢子粉中14种微量元素和8种常量元素,其中Ge的含量为5.9mg/kg,Hg、As、Pb的含量依次为<0.01、1.5、2.2mg/kg,而P、Fe、Zn等有益元素的含量介于0.12×10~3mg/kg与6.22×10~3mg/kg之间。     

Preferred conformation of peptides rich in Ac8c,a medium-ring alicyclic Cα,α-disubstituted glycine

A complete series of terminally blocked, monodispersed homo-oligopeptides (to the pentamer level) from the sterically demanding, medium-ring alicyclic C^α,α-disubstituted glycine 1-aminocyclooctane-1-carb oxylic acid (Ac₈c), and two Ala/Ac₈c tripeptides, were synthesized by solution methods and fully characterized. The preferred conformation of all the oligopeptides was determined in deuterochloroform solution by IR absorption and ¹H-NMR. The molecular structures of the amino acid derivative Z-Ac₈c-OH, the dipeptide pBrBz- (Ac₈c)₂-OH and the tripeptide pBrBz-(Ac₈c)₃-OtBu were assessed in the crystal state by X-ray diffraction. Conformational energy computations were performed on the monopeptide Ac-Ac₈c-NHMe. Taken together, the results obtained strongly support the view that the Ac₈c residue is an effective β-turn and helix former. A comparison is also made with the conformational preferences of α-aminoisobutyric acid, the prototype of C^{α, α}-disubstituted glycines, and of the other members of the family of 1-aminocycloalkane-1-carboxylic acids (Ac_nc, with n=3, 5–7) investigated so far. The implications for the use of the Ac₈c residue in peptide conformational design are considered.     

“增收宝－3”中氨基酸成分

用日立８３５－５０型氨基酸分析仪对“增收宝－３”中游离的氨基酸进行了分析。结果表明其中含有１５种氨基酸,以脯氨酸含量最高。实验结果揭示,氨基酸可能是“增收宝－３”中抗逆增产的有效成分。     

蜂花粉抗脑衰老的实验动物研究

蜂花粉抗脑衰老的实验动物研究蒋滢,杨炳华,黄美英苏州医学院生化教研室苏州２１５００７２探索衰老机制,寻求延缓衰老的有效途径是生命科学中的重大问题,也是亟待解决的实际问题。脑是指挥全身一切活动的中枢,脑组织特别容易遭受自由基及活性氧的损伤,因此防治脑衰...     

Lactate dehydrogenase in abdominal muscle of crayfishOrconectes limosus and shrimpcrangon crangon (Decapoda: Crustacea): Properties and evolutionary relationship

In crayfishOrconectes limosus and shrimpCrangon crangon abdominal muscle, lactate dehydrogenase (LDH, EC 1.1.1.27) is encoded by one locus. No polymorphism was detected. The enzymes were purified to homogeneity. The specific activities for purified crayfish and shrimp LDHs were 472 and 414 μmol NADH min⁻¹ mg⁻¹, respectively, at 30°C. Their physicochemical and kinetic properties did not resemble fish (Gadus morhua) LDH-A₄ isoenzyme. Their amino acid composition indicated greater similarity to fish LDH-C₄ isoenzymes.     

Characterization of amino-acid transport in Ricinus communis roots using isolated membrane vesicles

The mechanism and specificity of amino-acid transport at the plasma membrane of Ricinus communis L. roots was investigated using membrane vesicles isolated by phase partitioning. The transport of glutamine, isoleucine, glutamic acid and aspartic acid was driven by both a pH gradient and a membrane potential (internally alkaline and negative), created artificially across the plasma membrane. This is consistent with transport via a proton symport. In contrast, the transport of the basic amino acids, lysine and arginine, was driven by a negative internal membrane potential but not by a pH gradient, suggesting that these amino acids may be taken up via a voltage-driven uniport. The energized uptake of all of the amino acids tested showed a saturable phase, consistent with carrier-mediated transport. In addition, the membrane-potential-driven transport of all the amino acids was greater at pH 5.5 than at pH 7.5, which suggests that there could be a direct pH effect on the carrier. Several amino-acid carriers could be resolved, based on competition studies: a carrier with a high affinity for a range of neutral amino acids (apart from asparagine) but with a low affinity for basic and acidic amino acids; a carrier which has a high affinity for a range of neutral amino acids except isoleucine and valine, but with a low affinity for basic and acidic amino acids; and a carrier which has a higher affinity for basic and some neutral amino acids but has a lower affinity for acidic amino acids. The existence of a separate carrier for acidic amino acids is discussed.Abbreviations PM plasma membrane - TPP⁺ tetraphenylphosphonium ion - pH pH gradient - membrane potential This work was supported by the Agricultural and Food Research Council and The Royal Society. We would like to thank Mrs. Sue Nelson for help with some of the membrane preparations.     

Phosphoryl amino acids: Common origin for nucleic acids and protein

A series of compounds (DAP-AA) composed of an amino acid (AA) and a dialkyl phosphoryl group (DAP) is the basic elements of life chemistry. Self-catalysis of DAP-AA gives the self-assembly oligopeptides, even in aqueous medium at 38°C. The oligo-nucleotides could also be assembled from nucleosides' phosphorylation by DAP-AA. DAP-AA acts as the energy source as well as the phosphoryl donor for the synthesis of nuclic Acids and protein. A general expression for the self assembly system is proposed.     

Nitrate fluxes in soybean seedling roots and their response to amino acids: an approach using 15N

This study was undertaken to determine which of the two NO₃^? fluxes (influx or efflux) across plasma membranes of root cells is the target of those amino acids which have been shown to inhibit net NO₃^? uptake (Muller & Touraine 1992, Journal of Experimental Botany 43 , 617–623). Parallel experiments were performed to mea-sure either the time course of ¹⁵NO₃^? release from roots of soybean seedlings previously labelled with this isotope into non-labelled solution, or the time course of ¹⁵N accumulation from labelled ¹⁵NO₃^? solution in non-labelled seedlings. Focusing on the fate of ¹⁵NO₃^? in the cytoplasmic compartment, a model is developed to describe the time courses of the accumulation and release of tracer across the plasma membranes of root cells. Both time courses can be described by the sum of an exponential plus a linear term. In our material, the linear part of the accumulation time course is obscured by the NO₃^? fluxes exiting the cytoplasm, and the curve thus appears to be quasilinear over several minutes. However, we show that the use of the net tracer accumulation rate during this time period as an estimate of NO₃^? influx does not provide accurate estimates of influx and efflux. By contrast, ¹⁵NO₃^? efflux analysis permits calculation of the unidirectional fluxes across plasma membranes of root cells and the kinetic parameters of the cytoplasmic NO₃^? pool. Under our experimental conditions, efflux accounted for 30 to 50% of influx, and the cytoplasmic NO₃^? content was found to be in the 70–400nmol g^?1 fw range. Using this methodology, the effect of amino acid accumulation on unidirectional fluxes of nitrate was then examined. Pretreatments of the seedlings with an amino acid which has been shown to inhibit net NO₃^? uptake led to concomitant decreases in net accumulation rates of ¹⁵NO₃^? and of reduced ¹⁵N in roots and total ¹⁵N in cotyledons. NO₃^? influx was markedly inhibited by these treatments, while NO₃^? efflux remained essentially unaffected, or even decreased. It is concluded that the target of the regulation of NO₃^? uptake by phloemtranslocated amino acids is the influx system.     

The impact of mycorrhizal colonization upon nitrogen source utilization and metabolism in seedlings of Eucalyptus grandis Hill ex Maiden and Eucalyptus maculata Hook

Analysis of soil solution from forest sites dominated by Eucalyptus grandis and Eucalyptus maculata indicates that soluble forms of organic nitrogen (amino acids and protein) are present in concentrations similar to those of mineral nitrogen (nitrate and ammonium). Experiments were conducted to determine the extent to which mycorrhizal associations might broaden nitrogen source utilization in Eucalyptus seedlings to include organic nitrogen. In isolation, species of ectomycorrhizal fungi from northern Australia show varying abilities to utilize mineral and organic forms of nitrogen as sole sources. Pisolithus sp. displayed strongest growth on NH₄⁺, glutamine and asparagine, but grew poorly on protein, while Amanita sp. grew well both on mineral sources and on a range of organic sources (e.g. arginine, asparagine, glutamine and protein). In sterile culture, non-mycorrhizal seedlings of Eucalyptus grandis and Eucalyptus maculata grew well on mineral sources of nitrogen, but showed no ability to grow on sources of organic nitrogen other than glutamine. In contrast, mycorrhizal seedlings grew well on a range of organic nitrogen sources. These observations indicate that mycorrhizal associations confer on species of Eucalyptus the ability to broaden their resource base substantially with respect to nitrogen. This ability to utilize organic nitrogen was not directly related to that of the fungal symbiont in isolation. Seedlings mycorrhizal with Pisolithus sp. were able to assimilate sources of nitrogen (in particular histidine and protein) on which the fungus in pure culture appeared to grow weakly. Experiments in which plants were fed ¹⁵N-labelled ammonium were undertaken in order to investigate the influence of mycorrhizal colonization on the pathway of nitrogen metabolism. In roots and shoots of all seedlings, ¹⁵N was incorporated into the amide group of glutamine, and label was also found in the amino groups of glutamine, glutamic acid, γ-aminobutyric acid and alanine. Mycorrhizal colonization appeared to have no effect on the assimilation pathway and metabolism of [¹⁵N]H₄⁺; labelling data were consistent with the operation of the glutamate synthase cycle in plants infected with either Pisolithus sp. (which in isolation assimilates via the glutamate synthase cycle) or Elaphomyces sp. (which assimilates via glutamate dehydrogenase). It is likely that the control of carbon supply to the mycorrhizal fungus from the host may have a profound effect on both the assimilatory pathway and the range of nitrogen sources that can be utilized by the association.     

Effects of Prostaglandin E2 and Capsaicin on Behavior and Cerebrospinal Fluid Amino Acid Concentrations of Unanesthetized Rats: A Microdialysis Study

Abstract: Prostaglandin E₂ (PGE₂) delivered to the spinal cord produces an increased sensitivity to noxious (hyperalgesia) and innocuous (allodynia) stimuli. The mechanisms that underlie this effect remain unknown, but a PGE₂-evoked enhancement of spinal neurotransmitter release may be involved. To address this hypothesis, we examined the effect of PGE₂ on CSF concentrations of amino acids and also the modulatory effect of PGE₂ on capsaicin-evoked changes of spinal amino acid concentrations using a microdialysis probe placed in the lumbar subarachnoid space. Amino acids were quantified using HPLC with fluorescence detection. Addition of 1 mM, but not 10 or 100 µM, PGE₂ to the perfusate for a 10-min period (flow rate, 5 µl/min) evoked an immediate increase (80–100%) in glutamate (Glu), aspartate (Asp), taurine (Tau), glycine (Gly), and γ-aminobutyric acid (GABA) concentrations. Similarly, capsaicin infusion (0.1–10 µM) induced a dose-dependent increase in Glu, Asp, Tau, Gly, GABA, and ethanolamine levels. Significant increases in amino acid levels evoked by PGE₂ or capsaicin were associated with a touch-evoked allodynia. The combination of PGE₂ (10 µM) and capsaicin (0.1 or 1.0 µM) at concentrations that individually had no effect together evoked a significant increase (60–100%) in Glu, Asp, Tau, Gly, and GABA concentrations and produced tactile allodynia. These data demonstrate that spinally delivered PGE₂ or capsaicin substantially elevates CSF concentrations of both excitatory and inhibitory amino acids. The capacity of PGE₂ to enhance and prolong capsaicin-evoked amino acid concentrations may be one of the mechanisms by which spinal PGE₂ produces hyperalgesia and allodynia.