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1.
Summary Thirty four plant species belonging to 9 families were grown on a sand soil with various levels of added Cd. The Cd content
of aerial parts of the plants (tc) was correlated to the soil Cd level (sc) in a double-logarithmic relationship: log (tc)=α+β log (sc). The regression coefficients α and β statistically differed among plant families. Plant families were classified into 3
groups based on the α values; (1) low accumulation, Leguminosae; (2) moderate accumulation, Gramineae, Liliaceae, Cucurbitaceae
and Umbelliferae; and (3) high accumulation, Chenopodiaceae, Cruciferae, Solanaceae and Compositae. Values of β also enabled
to discriminate the families into (1) Umbelliferae, Cucurbitaceae and Cruciferae in which Cd accumulation was promoted at
higher soil Cd levels, and. (2) the other families which were of the excluder type. 相似文献
2.
Małgorzata A. Broda Barbara Rzeszotarska 《International journal of peptide research and therapeutics》1998,5(5-6):441-443
Summary α,β-Dehydroamino acids are useful peptide modifiers. However, their stereoelectronic properties still remain insufficiently
recognized. Based on FTIR experiments in the range ofv
s(N-H), AI, AII andv
s(Cα=Cβ) and ab initio calculations with B3LYP/6–31G*, we studied the solution conformational preferences and the amide electron
density perturbation of Ac-ΔXaa-NHMe, where ΔXaa=ΔAla, (E)-ΔAbu, (Z)-ΔAbu, (Z)-ΔLeu, (Z)-ΔPhe and ΔVal. Each of these dehydroamides adopts a C5 structure, which in Ac-ΔAla-NHMe is fully extended and accompanied by the strong C5 hydrogen bond. Interaction with bond Cα=Cβ lessens the amidic resonance within the flanking amide groups. TheN-terminal C=O bond is noticeably shorter, both amide bonds are longer than the corresponding bonds in the saturated entities
and the N-terminal amide system is distorted. Ac-ΔAla-NHMe constitutes an exception. ItsC-terminal amide bond is shorter than the standard one and both amide systems are ideally planar. Ac-(E)-ΔAbu-NHMe shares stereoelectronic features with both Ac-ΔAla-NHMe and (Z)-dehydroamides. 相似文献
3.
G-matrix FT projection NMR spectroscopy was employed for resonance assignment of the 79-residue subunit c of the Escherichia coli F1F0 ATP synthase embedded in micelles formed by lyso palmitoyl phosphatidyl glycerol (LPPG). Five GFT NMR experiments, that is,
(3,2)D HNNCO, L-(4,3)D HNNC
αβ
C
α, L-(4,3)D HNN(CO)C
αβ
C
α, (4,2)D HACA(CO)NHN and (4,3)D HCCH, were acquired along with simultaneous 3D 15N, 13Caliphatic, 13Caromatic-resolved [1H,1H]-NOESY with a total measurement time of ∼43 h. Data analysis resulted in sequence specific assignments for all routinely
measured backbone and 13Cβ shifts, and for 97% of the side chain shifts. Moreover, the use of two G2FT NMR experiments, that is, (5,3)D HN{N,CO}{C
αβ
C
α} and (5,3)D {C
αβ
C
α}{CON}HN, was explored to break the very high chemical shift degeneracy typically encountered for membrane proteins. It is shown
that the 4D and 5D spectral information obtained rapidly from GFT and G2FT NMR experiments enables one to efficiently obtain (nearly) complete resonance assignments of membrane proteins.
Qi Zhang, Hanudatta S. Atreya, Douglas E. Kamen, Mark E. Girvin and Thomas Szyperski—New York Consortium on Membrane Protein
Structure. 相似文献
4.
P2X1 receptors, the major subtype of P2X receptors in the vascular smooth muscle, are essential for α,β-methylene adenosine 5′-triphosphate
(α,β-MeATP)-induced vasoconstriction. However, relative physiological significance of P2X1 receptor-regulated vasoconstriction in the different types of arteries in the rat is not clear as compared with α1-adrenoceptor-regulated vasoconstriction. In the present study, we found that vasoconstrictive responses to noncumulative
administration of α,β-MeATP in the rat isolated mesenteric arteries were significantly smaller than those to single concentration
administration of α,β-MeATP. Therefore, we firstly reported the characteristic of α,β-MeATP-regulated vasoconstrictions in
rat tail, internal carotid, pulmonary, mesenteric arteries, and aorta using single concentration administration of α,β-MeATP.
The rank order of maximal vasoconstrictions for α,β-MeATP (E
max·α,β-MeATP) was the same as that of maximal vasoconstrictions for noradrenaline (E
max·NA) in the internal carotid, pulmonary, mesenteric arteries, and aorta. Moreover, the value of (E
max·α,β-MeATP/E
max·KCl)/(E
max·NA/E
max·KCl) was 0.4 in each of the four arteries, but it was 0.8 in the tail artery. In conclusion, P2X1 receptor-mediated vasoconstrictions are equally important in rat internal carotid, pulmonary, mesenteric arteries, and aorta,
but much greater in the tail artery, suggesting its special role in physiological function. 相似文献
5.
Dongsu Choi Kobayashi Makoto Ali M. Quoreshi Laiye Qu 《Landscape and Ecological Engineering》2009,5(2):107-113
We investigated the effect of ectomycorrhizal colonization, charcoal and CO2 levels on the germination of seeds of Larix kaempferi and Pinus densiflora, and also their subsequent physiological activity and growth. The seeds were sown in brown forest soil or brown forest soil
mixed with charcoal, at ambient CO2 (360 μmol mol−1) or elevated CO2 (720 μmol mol−1), with or without ectomycorrhiza. The proportions of both conifer seeds that germinated in forest soil mixed with charcoal
were significantly greater than for seeds sown in forest soil grown at each CO2 level (P < 0.05; t-test). However, the ectomycorrhizal colonization rate of each species grown in brown forest soil mixed with charcoal was
significantly lower than in forest soil at each CO2 treatment [CO2] (P < 0.01; t-test). The phosphorus concentrations in needles of each seedling colonized with ectomycorrhiza and grown in forest soil were
greater than in nonectomycorrhizal seedlings at each CO2 level, especially for L. kaempferi seedlings (P < 0.05; t-test), but the concentrations in seedlings grown in brown forest soil mixed with charcoal were not increased at any CO2 level. Moreover, the maximum net photosynthetic rate of each seedling for light and CO2 saturation (P
max) increased when the seedlings were grown with ectomycorrhiza at 720 μmol mol−1 [CO2]. Ectomycorrhizal colonization led to an increase in the stem diameter of each species grown in each soil treatment at each
CO2 level. However, charcoal slowed the initial growth of both species of seedling, constraining ectomycorrhizal development.
These results indicate that charcoal strongly assists seed germination and physiological activity. 相似文献
6.
Eric Mossel Fernando Formaggio Giovanni Valle Marco Crisma Claudio Toniolo Mitsunobu Doi Toshimasa Ishida Quirinus B. Broxterman Johan Kamphuis 《International journal of peptide research and therapeutics》1998,5(2-3):223-225
Summary In order to obtain further information on the role played by phenyl ring position in the Cα-methylated α-amino acid side chain on peptide preferred conformation, the crystal-state structural preferences of Cα-methyl, Cα-phenylglycine peptides have been determined by X-ray diffraction. This study shows that either the fully extended conformation
or the β-bend/310-helical structures are adopted by peptides characterized by this Cα-methylated, β-branched, aromatic α-amino acid. 相似文献
7.
Integrins, a family of transmembrane heterodimeric polypeptides, mediate various biological responses including cell adhesion
and migration. In this report, we show that sphingosine-1-phosphate (S1P) activates integrin αvβ3 in endothelial cells (ECs) via the sphingosine-1-phosphate receptor subtype 1 (S1P1)-mediated signaling pathway. S1P treatment
results in the activation of integrin αvβ3 in the lamellipodia region of ECs, suggesting that integrin αvβ3 plays a critical role in the S1P-stimulated chemotactic response of ECs. Indeed, S1P treatment induces the association of
focal adhesion kinase (FAK) and cytoskeletal proteins with integrin αvβ3, the ligation of αv and β3 subunits, as well as enhances endothelial migration on vitronectin-coated substrata. Knockdown endothelial S1P1 receptor,
treatments with pertussis toxin or dominant-negative-Rho family GTPases abrogates the S1P-induced integrin αvβ3 activation in ECs. Consequently, these treatments markedly inhibit the S1P-induced endothelial migratory response on vitronectin-coated
substrata. Collectively, these data indicate that the S1P-mediated signaling via the S1P1/Gi/Rho GTPases pathway activates integrin αvβ3, which is indispensable for S1P-stimulated chemotactic response of ECs. 相似文献
8.
Stephen J. Headey Amelia Vom Jamie S. Simpson Martin J. Scanlon 《Biomolecular NMR assignments》2008,2(1):93-96
Ketopantoate reductase is an essential enzyme for pantothenate (vitamin B5) synthesis and a potential antibiotic target. Here we report the 15N and 1HN, 13C′, 13Cα and 13Cβ chemical shift assignments of the 34 kDa ketopantoate reductase in its apo state. 相似文献
9.
Mylonas I Schiessl B Jeschke U Vogl J Makrigiannakis A Kuhn C Kunze S Schulze S Kainer F Friese K 《Journal of molecular histology》2006,37(1-2):43-52
During human pregnancy the placenta produces a variety of proteins like steroid hormones and their receptors that are responsible for the establishment and ongoing of the feto-placental unit. Inhibins are dimeric glycoproteins, composed of an α-subunit and one of two possible β-subunits (β
A or β
B). Aims of the present study were the determination of the frequency and tissue distribution patterns of the inhibin/activin subunits in human placental tissue of normal pregnancies and pregnancies complicated with fetal growth restriction (IUGR). Slides of paraffin embedded placental tissue were obtained after delivery from patients diagnosed with IUGR (n = 6) and normal term placentas (n = 8). Tissue samples were fixed and incubated with monoclonal antibodies inhibin/activin-subunits -α, -β
A, -β
B. Intensity of immunohistochemical reaction on the slides was analysed using a semi-quantitative score and statistical analysis was performed (P<0.05). A significant lower expression of the inhibin-α subunit in IUGR extravillous trophoblast compared to normal pregnancies was observed, while the inhibin-α immunostaining was significantly upregulated in syncytiotrophoblast. Additionally, a significant down-regulation of inhibin-β
B subunit in extravillous trophoblast cells in IUGR syncytiotrophoblast cells was demonstrated. A co-localisation of inhibin-α and the β-subunits was also observed, suggesting a production and secretion of intact inhibin A and inhibin B. Although the precise role of these inhibin/activin subunits in human placenta and IUGR pregnancies is still unclear, they could be involved in autocrine/paracrine signalling, contributing to several aspects like angiogenesis and tissue remodelling. 相似文献
10.
Summary. A procedure for the synthesis of enantiopure β3-amino acids from proteinogenic α-amino acids, developed by our group a few years ago, has been modified to enable the production
of C-2 fully deuterated, C-protected β3-amino acids and, even more important, the synthesis of valuable deuterium labelled N(Boc)-protected chiral synthons, such as 2-aminoalcohols, 2-aminoiodides, and β3-amino nitriles. 相似文献
11.
Katherine E. S. Locock Graham A. R. Johnston Robin D. Allan 《Neurochemical research》2009,34(10):1698-1703
The incorporation of extra binding groups onto known ligands is a powerful tool for the development of more potent and selective
agents at target sites such as the GABA receptors. In the present work we have attempted to build on the activity of the know
potent GABAA agonist 4-ACP-3-CA and its cis and trans saturated analogues CACP and TACP. We have investigated reactions to add thiol substituents to the α,β-unsaturated system
of 4-ACP-3-CA. The reaction was successful with a limited number of thiols but gave products of mixed stereochemistry. The
resultant thioether amino acids were screened for activity at human recombinant α1β2 γ2L GABAA receptors. The most interesting derivative was the benzylthioether which acted as an antagonist with an IC50 of 42 μM for the inhibition of a GABA EC50 dose (50 μM). This study has shown that GABA analogues derived by thiol addition to 4-aminocyclopent-1-enecarboxylic acid display interesting antagonist activity at the α1β2γ2L GABAA receptor.
Special issue article in honour of Dr. Graham Johnston. 相似文献
12.
Glycolate oxidase (GO; EC 1.1.3.1) was purified from the leaves of three plant species:Amaranthus hypochondriacus L.(NAD-ME type C4 dicot),Pisum sativum L. (C3 species) andParthenium hysterophorus L. (C3–C4. intermediate). A flavin moiety was present in the enzyme from all the three species. The enzyme from the C4 plant had a low specific activity, exhibited lower KM for glycolate, and required a lower pH for maximal activity, compared to the C3 enzyme. The enzyme from the C4 species oxidized glyoxylate at <10% of the rate with glycolate, while the GO from the C3 plant oxidized glyoxylate at a rate of about 35 to 40% of that with glycolate. The sensitivity of GO from C4 plant to -hydroxypyridinemethane sulfonate, 2-hydroxy-3-butynoate and other inhibitors was less than that of the enzyme from C3 source. The properties of GO fromParthenium hysterophorus, were similar to those of the enzyme fromPisum sativum. The characteristics of glycolate oxidase from leaves of a C4 plant,Amaranthus hypochondriacus are different from those of the C3 species or the C3–C4 intermediate. 相似文献
13.
A truncated mutant α-amylase, Xa-S2, was obtained from Xanthomonas campestris wild type α-amylases (Xa-WT) through random mutagenesis that contained 167 amino acid residues (approx 65% shorter than that
of Xa-WT). Secondary structure prediction implied that Xa-S2, would be unable to form the whole (β/α)8-barrel catalytic domain and did not have the three conserved catalytic residues of wild type α-amylase, but it still displays
the starch-hydrolyzing activity. Xa-S2 was prepared, characterized and compared to the recombinant wild-type enzymes. The
K
m for starch was 32 mg/ml; activity was optimal at pH 6.2 and 30°C. In contrast, the K
m for starch of Xa-WT was 8 mg/ml and optimal enzyme activity was at pH 6.0–6.2 and 45–50°C. Our results suggested that Xa-S2
is a new amylase with a minimal catalytic domain for hydrolyzing substrates with of α-1,4-glucosidic bonds.
T. Ke and X. D. Ma contributed equally to this work 相似文献
14.
Atkins N Jones SM Guillette LJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2006,176(8):783-792
The southern snow skink Niveoscincus microlepidotus is a viviparous alpine lizard with biennial reproduction, in which embryos are fully developed before winter but parturition is delayed until spring. We aimed to determine whether, in this species, in vitro uterine preparations are responsive to arginine vasotocin (AVT) and prostaglandin (PGF2α) in autumn and spring, and whether pre-treatment with the β-adrenergic agonist isoproterenol decreases the effectiveness of AVT in stimulating uterine contractions. Using the spotted snow skink (Niveoscincus ocellatus), an annually breeding species, we aimed to determine influences of temperature and the β-adrenergic system upon the response to AVT in vivo. In both N. microlepidotus and N. ocellatus females are more responsive to AVT than to PGF2α, and that the response to AVT is decreased, but not prevented, by β-adrenergic stimulation. In N. microlepidotus, uteri are equally responsive in both seasons to the hormones administered. In N. ocellatus environmental conditions, specifically, temperature, modulate the response to AVT in vivo with the time to parturition increasing as temperature decreases. We conclude that in these viviparous squamates the endocrine cascade leading to parturition is modulated by the β-adrenergic system, and that this may reflect the mechanism by which the timing of parturition is tied to suitable environmental conditions. 相似文献
15.
A method for microperfusion of isolated segments of the midgut epithelium of Drosophila larvae has been developed to characterize cellular transport pathways and membrane transporters. Stereological ultrastructural
morphometry shows that this epithelium has unusually long tight junctions, with little or no lateral intercellular volume
normally found in most epithelia. Amplification of the apical and basal aspects of the cells, by ≈ 17-fold and ≈ 7-fold, respectively,
predicts an almost exclusively transcellular transport system for solutes. This correlates with the high lumen-negative transepithelial
potential (Vt) of 38 to 45 mV and high resistance (Rt) of 800 to 1400 Ω • cm2 measured by terminated cable analysis, in contrast to other microperfused epithelia like the renal proximal tubule. Several
blockers (amiloride 10−4 M, ouabain 10−4 M, bumetanide 10−4 M), K+-free solutions, or organic solutes such as D-glucose 10 mM or DL-alanine 0.5 mM failed to affect Vt or Rt. Bafilomycin-A1 (3 to 5 μM) decreased Vt by ≈ 40% and short-circuit current (Isc) by ≈ 50%, and decreased intracellular pH when applied from the basal side only, consistent with an inhibition of an electrogenic
V-H+-ATPase located in the basal membrane. Gradients of H+ were detected by pH microelectrodes close to the basal aspect of the cells or within the basal extracellular labyrinth. The
apical membrane is more conductive than the basal membrane, facilitating secretion of base (presumably HCO3−), driven by the basal V-H+-ATPase. 相似文献
16.
Floristic compositions, life forms, reproductive types for forage species, and their responses to desertification in Hunshandake desert were studied. 164 species, in 30 families and 94 genera, were identified with C3 (137 species), C4 (25 species), and CAM (2 species) photosynthesis. Of the 25 C4 species, 76 % were grasses and Chenopodiaceae species (hereafter chenopods). This suggests that the C4 species mainly occurred in a few families in the desert region. The reduction of C3 species and the increase of C4 species with desertification indicated that C4 species might have higher tolerance to environmental stresses (e.g. dry and poor soil). Relatively more hemicrytophyte and therophyte forms in the desert are related to the local temperate climate and vegetation dynamics. Relatively greater proportions of C4/C3 and clonal species/sexual species at mobile dune showed that the C4 species and clonal species could make greater contribution to sand land restoration in the Hunshandake desert. 相似文献
17.
18.
Photosynthetic pathway Types (C3, C4, and CAM) and life forms of native species from Hulunbeier rangelands, north China were studied. Of the total 258 species, 216 species in 132 genera and 42 families had C3 photosynthetic pathway, including dominant herbs, e.g. Stipa baicalensis Roshev. and Leymus chinensis (Trin.) Tzvel., Filifolium sibiricum Kitam. and Arudinella hirta (Thunb.) Koidz. 38 species in 28 genera and 10 families were found with C4 photosynthesis, and 4 species in 2 genera and 1 family had CAM photosynthetic pathway. The occurrence of C4 species was common in Gramineae and Chenopodiaceae, and the two families were leading ones within C4 plants. More than 52 % of the total 258 species were in H form, 21 % in Th form, 19 % in G form; the other life form Types, e.g. Ch, M, N, and HH, formed less than 3 %. 68 % of C4 species were in Th form and 24 % in H form, indicating that these Types were the dominant life forms for C4 species in the rangeland region. The occurrence of C4 species was closely related with plant habitats, disturbed lands had the highest C4 abundance (55 % of the total C4 species), followed by grasslands and sandy soil, and forests had the lowest C4 abundance (8 %). Hence the occurrence of C4 species could be efficient indicator for rangeland dynamics in Hulunbeier rangelands. 相似文献
19.
Minoru Morikawa Naoki Harada Gen-Ichiro Soma Takeshi Yoshida 《In vitro cellular & developmental biology. Plant》1990,26(7):682-690
Summary The human leukemic cells HL-60, U937, KG-1 and THP-1 incubated with transforming growth factor-β1 (TGF-β1) were studied by
examining cell surface antigens and macrophage-specific activities. The addition of 0.5 ng/ml (20 pM) of TGF-β1 with 1α,25-dihydroxyvitamin D3 [1α, 25(OH)2D3] induced more Leu-M3 (CD14)-positive cells (approximately 80%) than 5×10−8
M 1α,25(OH)2D3 alone did (30 to 50%), although original HL-60 cells did not express any Leu-M3 antigen at all. Tumor necrosis factor-α (TNF-α)
with TGF-β1 and 1α,25(OH)2D3 was found to potentiate the expression of these surface antigens. Furthermore, the phagocytic activity was also induced strongly.
The expression of CR3 (CD11b) antigen was also increased, and all Leu-M3-positive cells were found CR3-positive when HL-60,
U937, and THP-1 cells were treated with these stimulants. In contrast, CR3 but not Leu-M3 was induced in KG-1 cells after
the same treatment. This may indicate that the responsiveness of leukemic cells to TGF-β1 and 1α,25(OH)2D3 might vary depending on a differentiation stage of the target cells. Furthermore, K562 cells originated from a more undifferentiated
precursor, were not able to respond to these two inducers. These results suggested that some of TGF-β superfamily proteins
might represent potent modulators in hematopoiesis, especially in the development of monocytes-macrophages or their precursors. 相似文献
20.
The pH-sensitivity of transepithelial K+ transport was studied in vitro in isolated vestibular dark cell epithelium from the gerbil ampulla. The cytosolic pH (pH
iwas measured microfluorometrically with the pH-sensitive dye 2,7-bicarboxyethyl-5(6)-carboxyfluorescein (BCECF) and the equivalent short-circuit current (I
sc), which is a measure for transepithelial K+ secretion, was calculated from measurements of the transepithelial voltage (V
t)and the transepithelial resistance (R
t) in a micro-Ussing chamber. All experiments were conducted in virtually HCO
3
–
-free solutions. Under control conditions, pH
iwas 7.01±0.04 (n=18), V
twas 9.1±0.5 mV, R
t16.7±0.09 cm2, and I
sc was 587±30 A/cm2 (n=49). Addition of 20 mm propionate– caused a biphasic effect involving an initial acidification of pH
i, increase in V
tand I
sc and decrease in R
tand a subsequent alkalinization of pH
i, decrease of V
tand increase of R
t. Removal of propionate– caused a transient effect involving an alkalinization of pH
i, a decrease of V
tand I
sc and an increase in R
t. pH
iin the presence of propionate– exceeded pH
iunder control conditions. Effects of propionate – on V
t, R
tand I
sc were significantly larger when propionate– was applied to the basolateral side rather than to the apical side of the epithelium. The pH
i-sensitivityof I
sc between pH 6.8 and 7.5 was –1089 A/(cm2 · pH-unit) suggesting that K+ secretion ceases at about pH
i7.6. Acidification of the extracellular pH (pH
o)caused an increase of V
tand I
sc and a decrease of R
tmost likely due to acidification of pH
i. Effects were significantly larger when the extracellular acidification was applied to the basolateral side rather than to the apical side of the epithelium. The pH
osensitivity of I
sc between pH 7.4 and 6.4 was –155 A/(cm2 · pH unit). These results demonstrate that transepithelial K+ transport is sensitive to pH
iand pH
oand that vestibular dark cells contain propionate– uptake mechanism. Further, the data suggest that cytosolic acidification activates and that cytosolic alkalinization inactivates the slowly activating K+ channel (I
sK)in the apical membrane. Whether the effect of pH
ion the I
sK channel is a direct or indirect effect remains to be determined.The authors wish to thank Drs. Daniel C. Marcus, Zhjiun Shen and Hiroshi Sunose for helpful discussions. This work was supported by grants NIH-R29-DC01098 and NIH-R01-DC00212. 相似文献