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1.
The fluorinated thioether compounds [C6H4Br-2-(CH2SRF)] (SRF = SC6F5 (1), SC6F4-4-H (2), SC6H4-2-F (3), SC6H4-3-F (4), SC6H4-4-F (5)) were synthesized and the reactivity of (1) was explored with transition metal complexes of the group 10. The results obtained indicate that the reactivity of these ligands is strongly dependent on the oxidation state of the metal center on the complex. Thus, products of the coordination of Pd(II) and Pt(II) to the sulfur moiety were obtained and unequivocally characterized by single crystal X-ray diffraction analyses. While spectroscopic evidence indicates that reaction of the Pt(0) compound [Pt(PEt3)3] leads to the formation of C–Br activation products, it is worth noting that similar reactions with Ni(0) and Pd(0) compounds only afford complex mixtures that in most of the cases indicate desulfurization of the ligands and decomposition of the metallic starting materials.  相似文献   

2.
Gourlet, P., A. Vandermeers, P. Vertongen, J. Rathe, P. De Neef, J. Cnudde, M. Waelbroeck and P. Robberecht. Development of high affinity selective VIP1 receptor agonists. Peptides 18(10) 1539–1545, 1997.—The biological effects of VIP are mediated by at least two VIP receptors: the VIP1 and the VIP2 receptors that were cloned in rat, human and mice. As the mRNA coding for each receptor are located in different tissues, it is likely that each receptor modulates different functions. It is therefore of interest to obtain selective agonists for each receptor subtype. In the present work, we achieved the synthesis of two VIP1 receptor selective agonists derived from secretin and GRF. [R16]chicken secretin had IC50 values of binding of 1, 10,000, 20, and 3000 nM for the rat VIP1-, VIP2-, secretin- and PACAP receptors, respectively. This peptide, however, had a weaker affinity for the human VIP1 receptor (IC50 of 60 nM). The chimeric, substituted peptide [K15,R16,L27]VIP(1-7)/GRF(8-27) had IC50 values of binding of 1, 10,000, 10,000 and 30,000 nM for the rat VIP1-, VIP2-, secretin- and PACAP receptors, respectively. Furthermore, its also showed an IC50 of 0.8 nM for the human VIP1 receptor and a low affinity for the human VIP2 receptor. It is unlikely that this GRF analogue interacted with a high affinity to the pituitary GRF receptors as it did not stimulate rat pituitary adenylate cyclase activity. The two described analogues stimulated maximally the adenylate cyclase activity on membranes expressing each receptor subtype.  相似文献   

3.
Estrogenic potency of six triterpene glycosides, Holothurin A, Holotoxin A1, Frondoside A, Cucumarioside A2-2 and Cauloside C, that are natural products and semi-synthesized Ginsenoside-Rh2, were examined with yeast two-hybrid system, including expressed genes of human estrogen receptor, hER, the co-activator TIF2 and lacZ as a reporter gene. Only Ginsenoside-Rh2 exhibited significant moderate estrogenic activity in the concentration range of 10−7 to 10−6 M. Its effect was approximately 30% of the activity of 17β-estradiol applied at half-effective concentration. This indicates Ginsenosides-Rh2 is a weak phytoestrogen. The sea cucumber triterpene glycosides, Holothurin A, Holotoxin A1, Cucumarioside A2-2 and Frondoside A, and plant glycoside Cauloside C had no appreciable estrogenic activity. Data obtained by yeast two-hybrid assay reflect structure–activity relationship between tested compounds and 17β-estradiol. Only Ginsenoside-Rh2 has some similarity in chemical structure with 17β-estradiol that might explain affinity of this glycoside to the hER receptor.  相似文献   

4.
By reacting [(C5Me5)M(SRF)2] (forM = Ir, Rf = C6F5 (1a) or C6F4H-p (1b); for M = Rh, Rf = C6F5 (2a) or C6F4H-p (2a)) in toluene with Na[AuCl4], ionic binuclear compounds with the general formula [(C5Me5)M(μ-SRF)2AuCl2]Cl for M = Ir, R = C6F5 (3a) or C6F4H-p (3a); for M = Rh, RF = C6F5 (4a) or C6F4H-p (4b) can be obtained, together with small amounts of [(C5Me5)2Rh2(μ-SRF)(μ-Cl)2]Cl (RF = C6F5 (5a) or C6F4H-p (5b)) as by-products when 2a and 2b were used.  相似文献   

5.
The reaction of dilithiated o-carborane (closo-1,2-Li2-1,2-C2B10H10) with CuCl2 gives 1,1′-bis(o-carborane) (1), 1,3′-bis(o-carborane) (2) and 1,4′-bis(o-carborane) (3). Compound 2 (C4B20H22) crystallizes in the monoclinic space group P21/n with A = 6.9275(6), B = 9.7655(8), C = 12.356(1) Å, β = 90.028(2)° and Z = 2. The structure was solved by direct methods and refined to R = 0.048 and Rw = 0.074. Compound 3 (C4B20H22) crystallizes in the orthorhombic space group P212121 with A = 6.8854(5), B = 12.523(1), C = 19.847(1) Å and Z = 4. The structure was solved by direct methods and refined to R = 0.078 and Rw = 0.091. The coupling reaction of dilithiated m-carborane (closo-1,7-Li2-1,7-C2B10H10) with CuCl2 results in the formation of 1,1′-bis(m-carborane) (4) and tetra(m-carborane) (5).  相似文献   

6.
Addition of (Me3SiNHCH2CH2)2NH (H3[N3(TMS)]) or (Me3SiNH-o-C6H4)2NH (H3[ArN3(TMS)]) to a solution of TaMe5 yields [N3(TMS)]TaMe2 or [ArN3(TMS)]TaMe2, respectively. An X-ray study of [ArN3(TMS)]TaMe2 showed it to have an approximate trigonal bipyramidal structure in which the two methyl groups are in equatorial positions and the triamido ligand is approximately planar. Addition of (C6F5NHCH2CH2)2NH (H3[N3(C6F5)]) to TaMe5 yields first [(C6F5NCH2CH2)2NH]TaMe3, which then decomposes to [(C6F5NCH2CH2)2N]TaMe2. An X-ray study of [(C6F5NCH2CH2)2N]TaMe2 shows it to be approximately a trigonal bipyramid, but the C6F5 rings are oriented so that they lie approximately in the TaN3 plane and two ortho fluorines interact weakly with the metal. Trimethylaluminum attacks the central nitrogen atom in [N3(TMS)]TaMe2 to give [(Me3SiNCH2CH2)2NAlMe3]TaMe2, an X-ray study of which shows it to be a trigonal bipyramidal species similar to the first two structures, except that the C-Ta-C bond angle is approximately 30° smaller (106.6(12)°). Addition of B(C6F5)3 to [(C6F5NCH2CH2)2NH]TaMe3 yields {[(C6F5NCH2CH2)2NH]TaMe2}+ {B(C6F5)3Me}, the structure of which most closely resembles that of [(Me3SiNCH2CH2)2NAlMe3]TaMe2 in that the C-Ta-C angle is 102.0(6)°. The C6F5 rings in {[(C6F5NCH2CH2)2NH]TaMe2}+ are turned roughly perpendicular to the TaN3 plane, i.e. ortho fluorines do not interact with the metal in this molecule.  相似文献   

7.
In a search for novel analogues of β3-adrenoceptor (AR) agonists relaxing the bladder for treatment of urinary dysfunction, 2-[4-(2-{[(1S,2R)-2-hydroxy-2-(4-hydroxyphenyl)-1-methylethyl]amino}ethyl)phenoxy]-2-methylpropionic acids (1a–e), into which a fibrate-like structure had been incorporated, were synthesised. Compound 1a was found to be a selective β3-AR agonist in functional assays using the ferret detrusor (β3-AR), rat uterus (β2-AR), and rat atrium (β1-AR); β3: EC50=7.8 nM, β2: IC50=7,300 nM, β1: EC20=23,000 nM. The introduction of a chlorine atom or methyl substituent at the ortho-position on the phenyl ring of 1a further improved β3-AR selectivity. In an in vivo study, 1a lowered intrabladder pressure (ED50=31 μg/kg) in rats, without increasing heart rate, in keeping with the in vitro results. Consequently, it is proposed that 1a and its analogues (1b–e), possess β3-AR agonistic activity in the absence of undesirable β1- or β2-AR mediated actions, and may be useful for clinical treatment and pharmacological studies.  相似文献   

8.
Gourlet, P., P. De Neef, J. Cnudde, M. Waelbroeck and P. Robberecht. In vitro properties of a high affinity selective antagonist of the VIP1 receptor. Peptides 18(10) 1555–1560, 1997.—A selective high affinity VIP1 receptor antagonist [Acetyl-His1, D-Phe2, Lys15, Arg16, Leu17] VIP(3-7)/GRF(8-27) or PG 97-269 was synthesized, by analogy with recently obtained selective VIP1 receptor agonists. The properties of the new peptide were evaluated on Chinese hamster ovary (CHO) cell membranes expressing either the rat VIP1-, rat VIP2- or the human VIP2- recombinant receptors and on LoVo cell membranes expressing exclusively the human VIP1 receptor. The IC50 values of 125I-VIP binding inhibition by PG 97-269 were 10, 2000, 2 and 3000 nM on the rat VIP1-, rat VIP2-, human VIP1- and human VIP2 receptors, respectively. PG 97-269 had a negligible affinity for the PACAP I receptor type. It did not stimulate adenylate cyclase activity, but inhibited competitively effect of VIP on the VIP1 receptor mediated stimulation of adenylate cyclase activity. The Ki values were respectively of 15 ± 5 nM and 2 ± 1 nM for the rat and human VIP1 receptors. Thus the described molecule in the first reported VIP antagonist with an affinity in the nM range and with a high selectivity for the VIP1 receptor subclass. It may be useful for evaluation of the physiological role of VIP in rat and human tissues.  相似文献   

9.
《FEBS letters》1994,350(2-3):195-198
The H+-ATPase from chloroplasts, CF0F1, was isolated, purified and reconstituted into asolectin liposomes. The enzyme was brought either into the oxidized state or into the reduced state, and the rate of ATP synthesis was measured after energisation of the proteoliposomes with an acid—base transition ΔpH (pHin = 5.0, pHout = 8.5) and a K+/valinomycin diffusion potential, Δφ (K+in = 0.6 mM, K+out = 60 mM). A rate of 250 s−1 was observed with the reduced enzyme (85 s−1 in the absence of Δφ). A rate of 50 s−1 was observed with the oxidized enzyme under the same conditions (15 s−1 in the absence of Δφ). The reconstituted enzyme contained 2 ATPbound per CF0F1 and 1 ADPbound per CF0F1. Upon energisation the enzyme was activated and 0.9 ADP per CF0F1, was released. Binding of ADP to the active reduced enzyme was observed under different conditions. In the absence of phosphate the rate constant for ADP binding was 105 M−1·s−1 under energized and de-energized conditions. In the presence of phosphate the rate of ADP binding drastically increased under energized conditions, and strongly decreased under de-energized conditions.  相似文献   

10.
A new compound containing a cubane tungsten chalcogenide cluster [W43-Te)4(CN)12]6− and Ca2+ complex units has been prepared by the reaction of aqueous solution of K6[W43-Te)4(CN)12] · 5H2O with the solution of a Ca(NO3)2 and phen(1,10-phenanthroline) (1:2 molar ratio) in a solvent mixture of H2O/EtOH. The structure of [{Ca(phen)2(H2O)}{Ca(phen)(H2O)4}{Ca(phen)2(H2O)3}][W4Te4(CN)12] · 5H2O 1 has been determined by X-ray crystallography. Compound 1 contains [{Ca(phen)(H2O)4}{Ca(phen)2(H2O)3}][W43- Te)4(CN)12] units bridged by {Ca(phen)2(H2O)}2+ units to form an one-dimensional zigzag chain structure. Interestingly, compound 1 showed a heterogeneous catalytic activity in the transesterification of a range of esters with methanol under the mild conditions. Moreover, it can be reused without any loss of activity through 10 runs with ester.  相似文献   

11.
To investigate receptor selectivity and possible species selectivity of a number of NPY analogues and fragments, receptor binding studies were performed using cell lines and membranes of several species. NPY displays 4–25-fold higher affinity for the Y2 receptor than for the Y1 receptor. The affinity of [Leu31,Pro34]NPY is 7–60-fold higher for the Y1 receptor when compared with the Y2 subtype. Species selectivity within the Y2 receptors is demonstrated by PYY(3–36), NPY(2–36), NPY(22–36), and NPY(26–36). It is shown that NPY(22–36) is species selective for the human Y2 subtype (Ki of 0.3 nM) compared with the rabbit and rat Y2 receptor (Ki of 2 and 10 nM, respectively). PYY(3–36) displays highest affinity for the human and rabbit Y2 subtype (Ki of 0.03 and 0.17 nM). The screening of NPY analogues and fragments revealed that highest affinity for the human Y2 receptor is shown by NPY(2–36) and PYY(3–36). In addition, PYY(3–36) and NPY(2–36) are not only subtype selective, but also species selective.  相似文献   

12.
Two novel, weakly antiferromagnetically coupled, tetranuclear copper(II) complexes [Cu4(PAP)22-1,1-N3)22-1,3-N3)22-CH3OH)2(N3)4 (1) (PAP = 1,4-bis-(2′-pyridylamino)phthalazine) and [Cu4(PAP3Me)22-1,1-N3)22-1,3-N3)2(H2O)2(NO2)2]- (NO3)2 (2) (PAP3Me = 1,4-bis-(3′-methyl-2′-pyridyl)aminophthalazine) contain a unique structural with two μ2-1,1-azide intramolecular bridges, and two μ2-1,3-azide intermolecular bridges linking pairs of copper(II) centers. Four terminal azide groups complete the five-coordinate structures in 1, while two terminal waters and two nitrates complete the coordination spheres in 2. The dinuclear complexes [Cu2(PPD)(μ2-1,1-N3)(N3)2(CF3SO3)]CH3OH) (3) and [Cu2(PPD)(μ2-1,1-N3)(N3)2(H2O)(ClO4)] (4) (PPD = 3,6-bis-(1′-pyrazolyl)pyridazine) contain pairs of copper centers with intramolecular μ2-1,1-azid and pyridazine bridges, and exhibit strong antiferromagnetic coupling. A one-dimensional chain structure in 3 occurs through intermolecular μ2-1,1-azide bridging interactions. Intramolecular Cu-N3-Cu bridge angles in 1 and 2 are small (107.9 and 109.4°, respectively), but very large in 3 and 4 (122.5 and 123.2°, respectively), in keeping with the magnetic properties. 2 crystallizes in the monoclinic system, space group C2/c with a = 26.71(1), b = 13.51(3), c = 16.84(1) Å, β = 117.35(3)° and R = 0.070, Rw = 0.050. 3 crystallizes in the monoclinic system, space group P21/c with a = 8.42(1), b = 20.808(9), c = 12.615(4) Å, β = 102.95(5)° and R = 0.045, Rw = 0.039. 4crystallizes in the triclinic system, space group P1, with a = 10.253(3), b = 12.338(5), c = 8.072(4) Å, = 100.65(4), β = 101.93(3), γ = 87.82(3)° and R = 0.038, Rw = 0.036 . The magnetic properties of 1 and 2 indicate the presence of weak net antiferromagnetic exchange, as indicated by the presence of a low temperature maximum in χm (80 K (1), 65 K (2)), but the data do not fit the Bleaney-Bowers equation unless the exchange integral is treated as a temperature dependent term. A similar situation has been observed for other related compounds, and various approaches to the problem will be discussed. Magnetically 3 and 4 are well described by the Bleaney-Bowers equation, exhibiting very strong antiferromagnetic exchange (− 2J = 768(24) cm−1 (3); − 2J = 829(11) cm−1 (4)).  相似文献   

13.
The preparation and structure–activity relationships (SARs) of potent agonists of the human β3-adrenergic receptor (AR) derived from a 4-aminopiperidine scaffold are described. Examples combine human β3-AR potency with selectivity over human β1-AR and/or human β2-AR agonism. Compound 29s was identified as a potent (EC50=1 nM) and selective (greater than 400-fold over β1- with no β2-AR agonism) full β3-AR agonist with in vivo activity in a transgenic mouse model of thermogenesis.  相似文献   

14.
The biologically active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), regulates osteoblast proliferation and differentiation. Production of 1,25(OH)2D3 is catalysed by the enzyme 25-hydroxyvitamin D3-1-hydroxylase (CYP27B1). Though highly expressed in the kidney, the CYP27B1 gene is also expressed in non-renal tissues including bone. It is hypothesised that local production of 1,25(OH)2D3 by osteoblasts plays an autocrine or paracrine role. The aim of this study was to investigate what factors regulate expression of the CYP27B1 gene in osteoblast cells. ROS 17/2.8 osteoblast cells were transiently transfected with plasmid constructs containing the 5′-flanking sequence of the human CYP27B1 gene fused to a luciferase reporter gene. Cells were treated with either parathyroid hormone (PTH), 1,25(OH)2D3, transforming growth factor-beta (TGF-β) or insulin-like growth factor-1 (IGF-1) and luciferase activity was measured 24 h later. The results showed that 1,25(OH)2D3 did not alter expression of the reporter construct, however treatment with PTH, IGF-1 and TGF-β decreased expression by 18, 53 and 58% respectively. The repressive action of TGF-β was isolated to the region between −531 and −305 bp. These data suggest that expression of the 5′-flanking region for the CYP27B1 gene in osteoblast cells may be regulated differently to that previously described in kidney cells.  相似文献   

15.
Park M  Lin L  Thomas S  Braymer HD  Smith PM  Harrison DH  York DA 《Peptides》2004,25(12):2127-2133
It has been suggested that the F1-ATPase β-subunit is the enterostatin receptor. We investigated the binding activity of the purified protein with a labeled antagonist, β-casomorphin1–7, in the absence and presence of cold enterostatin. 125I-β-casomorphin1–7 weakly binds to the rat F1-ATPase β-subunit. Binding was promoted by low concentrations of cold enterostatin but displaced by higher concentrations. To study the relationship between binding activity and feeding behavior, we examined the ability of a number of enterostatin analogs to affect β-casomorphin1–7 binding to the F1-ATPase β-subunit. Peptides that suppressed food intake promoted β-casomorphin1–7 binding whereas peptides that stimulated food intake or did not affect the food intake displaced β-casomorphin1–7 binding. Surface plasmon resonance measurements show that the β-subunit of F1-ATPase binds immobilized enterostatin with a dissociation constant of 150 nM, where no binding could be detected for the assembled F1-ATPase complex. Western blot analysis showed the F1-ATPase β-subunit was present on plasma and mitochondrial membranes of rat liver and amygdala. The data provides evidence that the F1-ATPase β-subunit is the enterostatin receptor and suggests that enterostatin and β-casomorphin1–7 bind to distinct sites on the protein.  相似文献   

16.
Earthworm fibrinolytic enzyme II (EFE-II) from Eisenia fetida has a broad hydrolytic specificity for peptide bonds. Our experiments show that EFE-II can hydrolyze the specific chromogenic substrates of thrombin (Chromozym TH), trypsin (Chromozym TRY) and elastase (Chromozym ELA). The Michaelis–Menten constant (Km) for Chromozym ELA (245 μM) is much higher than those for the thrombin (90 μM) and trypsin (60 μM) substrates. On the other hand, EFE-II is inhibited most strongly by soybean trypsin inhibitor (SBTI), and weakly inhibited by elastinal, suggesting that EFE-II has a trypsin-like activity. Degradation of plasminogen (PLg) and fibrinogen by EFE-II was investigated after EFE-II had been immobilized onto 1,1′-carboryl-diimidazole (CDI)-activated Sepharose CL-6B. The immobilized EFE-II has 55–60% activity of the native enzyme with a higher thermal and pH resistance. EFE-II cleaves PLg at four hydrolytic sites: Lys77–Arg78, Arg342–Met343, Ala444–Ala445 and Arg557–Ile558. The site Arg557–Ile558 is also recognized and cleaved by tissue plasminogen activator (t-PA) and urokinase (UK), producing active plasmin. Cleaving Ala444–Ala445 released mini-plasmin with secondary activity to hydrolyze fibrin. Immobilized EFE-II degrades not only the A chain of fibrinogen in the C-terminal region (like human neutrophil elastase, HNE), but also in the N-terminal region at the Val21–Glu22 site.  相似文献   

17.
Insoluble Aβ1–42 is the main component of the amyloid plaque. We have previously demonstrated that exposure to low pH can confer the molten globule state on soluble Aβ1–42 in vitro [Biochem. J. 361 (2000) 547] and unfolding experiments with guadinine hydrochloride (GdnHCl) have now confirmed this observation. The molten globule state of the protein has many biological properties and understanding the mechanisms of its formation is an important step in devising a therapeutic strategy for Alzheimer's disease (AD). We therefore investigated the ability of a series of synthetic eight-residue peptides derived from Aβ1–42 to inhibit the acid-induced aggregation of Aβ1–42 and identified the potent peptides to be Aβ15–22, Aβ16–23 and Aβ17–24. A1-antichymotrypsin, a member of the serine proteinase inhibitor (serpin) family is another major component of the amyloid plaque. In the present study, we investigated the proteolytic activity of Aβ1–42 against casein at different pHs. Chemical modification of amino acid residues in Aβ1–42 indicated that serine and histidine residues, but not aspartic acid, are necessary for enzymatic activity, suggesting that it is a serine proteinase. Amino acid substitution studies indicate that glutamic acids at positions 11 and 22 participate indirectly in proteolysis and we surmise that amino acid residues 29–42 are required to stabilize the conformer. A study of metal ions suggested that Cu2+ affected the enzymatic activity, but Zn2+ and Fe2+ did not. Interestingly, Aβ14–21 and Aβ15–22 were the only peptides that inhibited the proteolytic activity of Aβ42. Therefore, Aβ15–22 may control both aggregation of Aβ1–42 at acidic pH and its proteolytic activity at neutral pH. Consequently, we suggest that it may be of use in the therapy of Alzheimer's disease.  相似文献   

18.
Vertongen, P., S. N. Schiffmann, P. Gourlet and P. Robberecht. Autoradiographic visualization of the receptor subclasses for Vasoactive Intestinal Polypeptide (VIP) in rat brain. Peptides 18(10) 1547–1554, 1997.—Vasoactive Intestinal Polypeptide (VIP) exerts its biological effects through interaction with two high affinity receptors named the VIP1- and the VIP2 receptors. Their messenger RNAs have been mapped in rat brain by in situ hybridization. A cyclic peptide (RO 25-1553) and a secretin analogue ([R16]chicken secretin) were identified as selective agonist peptides for the VIP2- and VIP1 receptors, respectively. The iodinated peptides retained the high affinity and selectivity of the unlabelled peptides and were used for the mapping of each receptor subclass in rat brain. VIP1 receptors were present in the cerebral cortex, the piriform cortex, the claustrum, the caudate-putamen, the dentate gyrus, the lateral amygdaloïd nucleus, the anteroventral thalamic nucleus, the rhomboïd nucleus, the supraoptic nucleus and the choroïd plexus. VIP2 receptors were present in the cerebral cortex, the claustrum, the caudate-putamen, the nucleus accumbens, the lateral septal nuclei, the bed nucleus of the stria terminalis, the basolateral amygdaloïd nucleus, the Ammon’s horn, the thalamic nuclei except some centromedial nuclei, the medial habenula, the suprachiasmatic nucleus, the periventricular nucleus, the mammilary nucleus, the superior colliculus and the choroïd plexus.  相似文献   

19.
灌水模式对冬小麦光合特性、水分利用效率和产量的影响   总被引:5,自引:0,他引:5  
试验于2013—2014和2014—2015年连续2个生长季在自动控制干旱棚内的隔离池中进行,拔节期设3个灌水梯度,灌水量分别为0(J_0)、37.5(J_1)、75 mm(J_2),扬花期设3个灌水梯度,灌水量分别为0(F_0)、37.5(F_1)、75 mm(F_2),灌浆期所有处理均按75 mm灌溉,共9个处理,研究不同灌溉模式对小麦中后期不同生育阶段植株生长、耗水量、水分利用效率、光合特性和产量构成因素的影响.结果表明:拔节期干旱(0和37.5 mm)显著降低了小麦扬花期的净光合速率和拔节后的叶面积,扬花期的灌水量直接影响扬花期后的旗叶净光合速率;拔节期干旱扬花期补水和扬花期干旱灌浆期补水都可以有效提高植株的干物质量;拔节期灌水量越多,全生育期耗水量越大;除J_1F_2外,全生育期灌水量越大,耗水量越大,产量也越高;J_1F_2处理产量和水分利用效率最高.扬花期充足的灌水量使J_1F_2处理具有较高的花后旗叶净光合速率,此期补偿性灌溉加快了干物质积累,也保证了较高的穗粒数,使其最终产量高于J_2F_2处理或与之持平,同时J_1F_2拔节期较低的灌水量降低了小麦生育中后期的耗水量,其水分利用效率也显著高于其他处理.综上,J_1F_2是小麦生育中期理想的水分处理组合.  相似文献   

20.
Hexacoordination of the neutral phosphorus compounds 4–6 is evidenced by their high field 31P NMR chemical shifts and is further substantiated by the crystal structure of 5 and 6.5 contains the potentially bis-chelating ligand Ar = (C6H3(CH2NMe2)2-2,6) and 6 the same ligand with a protonated amino group. In both cases the compounds exhibit slightly distorted octahedral geometry. In compound 5, only one NMe2 group is coordinated to the phosphorus atom with an N → P bond of 2.063 Å. In compound 6, the NMe2 group is coordinated to the phosphorus atom with an N → P bond of 2.007 Å while the dimethylammonium substituent is pointing away from the phosphorus atom forming a hydrogen bridge with two oxygen atoms. The fluxional behavior of these three novel six-coordinate phosphorus compounds was studied by dynamic 1H NMR spectroscopy.  相似文献   

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