共查询到20条相似文献,搜索用时 31 毫秒
1.
Satoshi Matsubara Satoshi Shiojiri Tozo Fujii Nobuo Ogawa Kikuko Imamura Kagari Yamagishi Koichi Koshimizu 《Phytochemistry》1977,16(7):933-937
(R)-(+)- and (S)-(?)-dihydrozeatins [(R)-(+)- and (S)-(?)-6-(4-hydroxy-3-methylbutylamino)purines, 1a and 1b] and their ribosides {(?)-6-[(R)-4-hydroxy-3-methylbutylamino]- and (?)-6-[(S)-4-hydroxy-3-methyl-butylamino]-9-β-D-ribofuranosylpurines, 3a and 3b} were synthesized and tested for their cytokinin activity by four bioassay systems, the growth of tobacco callus, the seed germination of lettuce, the fr. wt increase of excised radish cotyledons and the retardation of chlorophyll degradation in radish cotyledons. In tobacco callus bioassay, 1a was more active than 1b. The ribosides 3a and 3b were not less active than their corresponding aglycones 1a and 1b. In other bioassays used the activity followed the order: 1a >3a >1b >3b. In tobacco callus bioassay and lettuce seed germination, trans-zeatin [6-(4-hydroxy-3-methylbut-trans-2-enylamino)purine] showed stronger cytokinin activity than 1a. 相似文献
2.
J.G. Lammers Th.J. Liefkens J. Bus J. van der Meer 《Chemistry and physics of lipids》1978,22(4):293-305
The widely used partial synthesis of phospholipids via deacylation of naturally occurring phospholipids, followed by reacylation with fatty acid anhydrides, is accompanied by phosphoryl migration. The resulting mixture of α- and β-phospholipids was separated by short-column chromatography. Milder acylation procedures in which no phosphoryl migration occurs, were developed. 1,2-Dilinoleoyl-sn-glycero-3-phosphocholine was prepared in 50% yield by acylation of sn-glycero-3-phosphocholine (GPC) with N-linoleoylimidazole. Detailed NMR and infrared spectra of α- and β-phosphatidylcholines (PCs) and -ethanolamines (PEs) are reported and the differences between isomers discussed. 相似文献
3.
A.K. Banerjee B.J. Broughton T.S. Burton M.P.L. Caton A.J. Christmas E.C.J. Coffee K. Crowshaw M.A. Heazell K.A.J. Stuttle G.L. Watkins 《Prostaglandins & other lipid mediators》1978,16(4):541-554
The synthesis and gastrointestinal pharmacology of some 11-deoxyprostaglandin E1 analogues are described with results analysed for selectivity from side effects. 11-Deoxygenation reduced potency relative to PGE2 but, as has been reported for natural PGs, 15- or 16-methyl analogues were more potent than the unsubstituted parent compound in the order 16-methyl > 15-methyl > 16, 16-dimethyl. The results suggest that a complex interaction between C-15 and C-16 in methyl analogues affects their profile of activity, but that none of the modifications studied conferred a substantial potency or selectivity advantage over PGE2. 相似文献
4.
Videira PA Amado IF Crespo HJ Algueró MC Dall'Olio F Cabral MG Trindade H 《Glycoconjugate journal》2008,25(3):259-268
Several glycoconjugates are involved in the immune response. Sialic acid is frequently the glycan terminal sugar and it may
modulate immune interactions. Dendritic cells (DCs) are antigen-presenting cells with high endocytic capacity and a central
role in immune regulation. On this basis, DCs derived from monocytes (mo-DC) are utilised in immunotherapy, though many features
are ignored and their use is still limited. We analyzed the surface sialylated glycans expressed during human mo-DC generation.
This was monitored by lectin binding and analysis of sialyltransferases (ST) at the mRNA level and by specific enzymatic assays.
We showed that α2-3-sialylated O-glycans and α2-6- and α2-3-sialylated N-glycans are present in monocytes and their expression increases during mo-DC differentiation. Three main ST genes are committed
with this rearrangement: ST6Gal1 is specifically involved in the augmented α2-6-sialylated N-glycans; ST3Gal1 contributes for the α2-3-sialylation of O-glycans, particularly T antigens; and ST3Gal4 may contribute for the increased α2-3-sialylated N-glycans. Upon mo-DC maturation, ST6Gal1 and ST3Gal4 are downregulated and ST3Gal1 is altered in a stimulus-dependent manner.
We also observed that removing surface sialic acid of immature mo-DC by neuraminidase significantly decreased its endocytic
capacity, while it increased in monocytes. Our results indicate the STs expression modulates the increased expression of surface
sialylated structures during mo-DC generation, which is probably related with changes in cell mechanisms. The ST downregulation
after mo-DC maturation probably results in a decreased sialylation or sialylated glycoconjugates involved in the endocytosis,
contributing to the downregulation of one or more antigen-uptake mechanisms specific of mo-DC. 相似文献
5.
Calcium - how and why? 总被引:1,自引:0,他引:1
Jaiswal JK 《Journal of biosciences》2001,26(3):357-363
Calcium is among the most commonly used ions, in a multitude of biological functions, so much so that it is impossible to
imagine life without calcium. In this article I have attempted to address the question as to how calcium has achieved this
status with a brief mention of the history of calcium research in biology. It appears that during the origin and early evolution
of life the Ca2+ ion was given a unique opportunity to be used in several biological processes because of its unusual physical and chemical
properties. 相似文献
6.
Radosław Gniłka Antoni Szumny Agata Białońska Czesław Wawrzeńczyk 《Phytochemistry letters》2012,5(2):340-345
The effective method of isolation, separation and purification of (?)-α- and (+)-β-thujone (1a and 1b) from Thuja occidentalis was elaborated. Chemical (m-CPBA) and microbial Baeyer–Villiger oxidation of (?)-α- and (+)-β-thujone was carried out. Four new bicyclic δ-lactones (2a, 2b, 3a and 3b) with condensed cyclopropane ring were obtained. 相似文献
7.
Pereira AC Magalhães LG Gonçalves UO Luz PP Moraes AC Rodrigues V da Matta Guedes PM da Silva Filho AA Cunha WR Bastos JK Nanayakkara NP e Silva ML 《Phytochemistry》2011,72(11-12):1424-1430
(±)-Licarin A (1) was obtained by oxidative coupling, and its enantiomers, (?)-licarin A (2) and (+)-licarin A (3), were resolved by chiral HPLC. Schistosomicidal and trypanocidal activities of these compounds were evaluated in vitro against Schistosoma mansoni adult worms and trypomastigote forms of Trypanosoma cruzi. The racemic mixture (1) displayed significant schistosomicidal activity with an LC50 value of 53.57 μM and moderate trypanocidal activity with an IC50 value of 127.17 μM. On the other hand, the (?)-enantiomer (2), displaying a LC50 value of 91.71 μM, was more active against S. mansoni than the (+)-enantiomer (3), which did not show activity. For the trypanocidal assay, enantiomer 2 showed more significant activity (IC50 of 23.46 μM) than enantiomer 3, which showed an IC50 value of 87.73 μM. Therefore, these results suggest that (±)-licarin A (1) and (?)-licarin A (2) are promising compounds that could be used for the development of schistosomicidal and trypanocidal agents. 相似文献
8.
Synthetic 2′-hydroxy-3,4′,6′-trimethoxy-4-benzyloxychalcone (I) affords (±)-7,3′-di-O-methyleriodictyol (II) and 7,3′-di-O-methylluteolin (or velutin, VII) identical with natural samples. Similarly synthetic 2′-hydroxy-4,4′,6′-trimethoxy-3-benzyloxychalcone (X) gives natural (±)-7,4′-di-O-methyleriodictyol (XI) and 7,4′-di-O-methylluteolin (or pilloin, IX). However, attempts to partially etherify II with one mole of prenyl bromide to obtain the natural prenyl ether failed; only the corresponding diprenyloxychalcone (IV) was obtained. 相似文献
9.
Increased sialylation of cell surface glycoconjugates is among the key molecular changes associated with malignant transformation
and cancer progression. We investigated significance of linkage-specific sialylation changes in oral carcinogenesis. Tissue
and serum levels of total sialic acid (TSA), linkage-specific sialyltransferases (ST) and sialoproteins were analyzed from
patients with oral precancerous conditions (OPC) and oral cancer as well as the post-treatment follow-up blood samples of
oral cancer patients. TSA levels were measured using a spectrophotometric method. The linkage-specific lectins, Sambusus nigra (SNA) and Maackia amurensis (MAM) detects α2-6- and α2-3-linked sialic acid, respectively, were used to analyze ST activity and sialoproteins. Malignant
tissues showed significantly higher levels of TSA, reactivity of SNA and MAM, and α2,3-ST activity compared to the adjacent
normal tissues. α2,6-ST was also higher in malignant tissues. Similarly, the marker levels were higher in precancerous tissues
than their adjacent normal tissues. Serum levels of TSA, TSA/ total proteins, α2-6-sialoproteins and α2,6-ST were markedly
increased in untreated oral cancer patients compared to the controls and OPC as well as responder (CR) patients. Serum levels
of the markers were higher or comparable between untreated oral cancer patients and non-responders (NR). Serum levels of α2-3-sialylation
were elevated in non-responders compared with the responders. Further, the observed sialylation changes in tissue and serum
were found to be associated with various clinicopathological features and disease progression. Thus, the data suggest potential
utility of sialylation markers in early detection, prognostication and treatment monitoring of oral cancer. 相似文献
10.
Yukihiro Isoda Shogo Asanami Ken’ichi Takeo Yasunori Nitta 《Bioscience, biotechnology, and biochemistry》2013,77(12):3223-3229
Among 2,3-epoxypropyl α-d-glucopyranoside and 2,3-epoxypropyl α-maltooligosaccharides and the β-anomers, 2,3-epoxypropyl α-d-glucopyranoside (α-EPG) strongly inactivated the β-amylases [EC 3.2.1.2] of sweet potato, barley, and Bacillus, cereus, in addition to soybean β amylase [J. Biochem., 99, 1631 (1986)]. However, none of the compounds used inactivated any α-amylases [EC 3.2.1.1] of porcine pancreas, Aspergillus oryzae, or Bacillus amyloliquefaciens. Irreversible incorporation of 14C-labeled α-EPG into β-amylases was stoichiometric, i.e., one α-EPG per active site of the enzyme was bound, and the inactivations were almost complete. The results suggest that α-EPG is an affinity labeling reagent selective for β-amylase. Slow inactivations by the other compounds were also observed, depending on the difference of source of β amylase. 相似文献
11.
Lopatina T. V. Medvedeva N. I. Baikova I. P. Iskhakov A. S. Kazakova O. B. 《Russian Journal of Bioorganic Chemistry》2019,45(4):292-301
Russian Journal of Bioorganic Chemistry - A five-stage synthesis of azepanobetulin from betulin with a total yield of 47% has been carried out. The acylation of azepanobetulin with anhydrides or... 相似文献
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Jerzy Boryski Tomasz Ostrowski Bożenna Golankiewicz 《Nucleosides, nucleotides & nucleic acids》2013,32(7):1271-1280
Abstract Ribosylation of 3-methylguanine la was investigated by enzymatic and chemical methods. Compound la did not act as a substrate for purine nucleoside phosphorylase. N-2-Protected 3-methylguanines 4 and 6 underwent exclusive N-7 glycosylation by fusion and chloromercury methods to give 5 and 7. Fully acetylated 7-α-D-ribofuranoside 5 was also obtained by thermal transglycosylation of the corresponding 9-α-D-ribofuranoside 9. The reverse isomerization 5 → 9 did not occur. The differences in the relative stability towards acidic hydrolysis between 7- and 9-(α-D-ribofuranosyl)-3-methylguanines are distinctly higher than those described so far for the other 7-9 isomeric nucleosides. 相似文献
14.
Cong Jiang Ralph H. Baur James J. Dechter David C. Baker 《Nucleosides, nucleotides & nucleic acids》2013,32(2):123-146
Abstract Both 2-(α- and β-D-arabinofuranosyl) thiazole-4-carboxamides were synthesized from 2,3,5-tri-O-benzyl-1-O-(p-nitrobenzoyl)-D-arabinofuranose via the 1-cyano- and 1-thioamide sugars. Anomeric assignments were made based on 1H and 13C NMR, as well as on CD spectra. 相似文献
15.
Abstract Nitration of benzimidazole leads to the formation of the two isomeric 5,6- and 4,6(5,7)-dinitrobenzimidazoles, which may be isolated by fractional crystallization. The chloromercury salts of these were employed to synthesize the corresponding 1-β-D-ribofuranosides, unequivocally characterized by 1H NMR spectroscopy. Reference is made to the biological significance of these results. 相似文献
16.
Zhaomin Li Hui Peng Li Qin Jing Qi Xiaobing Zuo Jing-Yuan Liu Jian-Ting Zhang 《The Journal of biological chemistry》2013,288(44):31447-31457
Many proteins exist and function as homodimers. Understanding the detailed mechanism driving the homodimerization is important and will impact future studies targeting the “undruggable” oncogenic protein dimers. In this study, we used 14-3-3σ as a model homodimeric protein and performed a systematic investigation of the potential roles of amino acid residues in the interface for homodimerization. Unlike other members of the conserved 14-3-3 protein family, 14-3-3σ prefers to form a homodimer with two subareas in the dimeric interface that has 180° symmetry. We found that both subareas of the dimeric interface are required to maintain full dimerization activity. Although the interfacial hydrophobic core residues Leu12 and Tyr84 play important roles in 14-3-3σ dimerization, the non-core residue Phe25 appears to be more important in controlling 14-3-3σ dimerization activity. Interestingly, a similar non-core residue (Val81) is less important than Phe25 in contributing to 14-3-3σ dimerization. Furthermore, dissociating dimeric 14-3-3σ into monomers by mutating the Leu12, Phe25, or Tyr84 dimerization residue individually diminished the function of 14-3-3σ in resisting drug-induced apoptosis and in arresting cells at G2/M phase in response to DNA-damaging treatment. Thus, dimerization appears to be required for the function of 14-3-3σ. 相似文献
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《Cell communication & adhesion》2013,20(4-6):219-223
Gap junctions are composed of connexins that form transmembrane channels between adjacent cells. The C-terminal tail of connexin-43 (Cx43), the most widely expressed connexin member, has been implicated in the regulation of Cx43 channel gating. Interestingly, channel-independent processes regulated by Cx43 have also been postulated. In our studies to elucidate the mechanism of Cx43 channel gating by growth factors and to explore additional functions of gap junctions, we have identified three interacting partners of the C-terminal tail of Cx43 (Cx43CT). (i) the c-Src tyrosine kinase, which phosphorylates Cx43CT and is involved in G protein-mediated inhibition of Cx43 gap junctional communication, (ii) the ZO-1 ‘scaffold’ protein, which might recruit signaling proteins into Cx43-based gap junctions. (iii) microtubules (consisting of α/β-tubulin dimers), which extend with their distal ends to Cx43-based gap junctions, suggesting that Cx43 gap junctions may play a novel role in regulating microtubule stability in contacted cells. Here we show that Cx43 binds α-tubulin equally well as β-tubulin. In addition, we show that the second, but not the first, PDZ domain of ZO-1 binds directly to Cx43, and we confirm that the very C-terminal isoleucine residue of Cx43 is critical for ZO-1 binding. 相似文献
20.
Psurski M Błażewska K Gajda A Gajda T Wietrzyk J Oleksyszyn J 《Bioorganic & medicinal chemistry letters》2011,21(15):4572-4576
A series of 15 mostly new dialkoxyphosphoryl alkyl and aralkyl isothiocyanates were synthesized using two alternative strategies, and their in vitro antiproliferative activity against several cancer cell lines (including drug resistant) is here demonstrated. The IC50 values measured for the new compounds are within the range of 6.3-21.5 μM, and they are quite similar to the activity of two best and most extensively investigated natural benzyl isothiocyanate (A) and phenethyl isothiocyanate (B). Preliminary studies utilizing the cell cycle and reduced glutathione level analysis performed on A549 lung cancer cell line using representative compounds revealed important differences in the mechanism of action possibly correlated with their chemical properties. Hydrophobic compounds react mainly with the cytosolic glutathione reduced leading to its depletion, causing an oxidative stress and cell cycle arrest in G0/G1 phase. On the other hand, hydrophilic compounds cause moderate cell cycle arrest and massive cell death associated with moderate reduced glutathione depletion. These suggest that significant changes in the chemical structure of isothiocyanates, which do not lead to the significant changes in antiproliferative activity, but simultaneously cause a differences in the mechanism of action are possible. 相似文献