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1.
Time-course studies of the uptake of L-[methyl 14C]-methionine have shown rapid uptake by Ailanthus altissima cells when fed at weekly stages throughout the growth cycle. The radio-label from [14C]-methionine was shown to be incorporated into 1-methoxycanthin-6-one with the highest level of incorporation being achieved with cells fed late in the growth phase. 相似文献
2.
Summary The regio- and stereoselective biotransformation of bicyclo (3. 2. 0) hept-2-en-6-one by the NADH-dependent Baeyer-Villiger monooxygenase from camphorgrownPseudomonas putida NCIMB 10007 has been shown to yield a chiral lactone not accessible by curently-used biocatalysts. The biotransformation can be conductedin vitro using two alternative coupled enzyme systems (alcohol dehydrogenase and monooxygenase: formate dehydrogenase and monooxygenase) within situ recycling of NAD+/NADH. 相似文献
3.
13C enrichments at C-3, C-4, C-5 and C-6 of canthin-6-one from cell cultures of Ailanthus altissima supplemented with [1-13C], [2-13C] and [1,2-13C] acetate, give evidence of the involvement of ketoglutarate as an intact precursor in the biosynthetic pathway. 相似文献
4.
The uptake of l-[methylene-14C]-tryptophan from culture medium into root organs of Cinchona ledgeriana and the subsequent incorporation of the radiolabel into quinine and quinidine is reported. In addition, feeding unlabelled l-tryptophan at levels of 500mg/l to the cultures results in a 5-fold increase in the yields of both quinoline alkaloids. 相似文献
5.
Héctor S. Barra Carlos E. Argaran˜a 《Biochemical and biophysical research communications》1982,108(2):654-657
Spermine, spermidine and putrescine produce dose dependent stimulation of the invitro tubulinyl-tyrosine carboxypeptidase. Maximal stimulation was obtained with spermine, spermidine or putrescine at 0.06 mM, 1 mM and 6 mM, respectively. At higher concentrations, the enzyme activity was inhibited. The enzyme was also activated by Mg++; the concentration formaximal effect was 4–6 mM. The stimulation produced by optimal concentration of each amine was unaffected by Mg++ up to 2 mM; higher concentration of Mg++ showed inhibitory effect. At optimal Mg++ concentration, the carboxypeptidase activity was inhibited by increasing amine concentration. The amines at 0.5 or 5 mM did not produce any effect on the incorporation of tyrosine catalyzed by tubulin tyrosine ligase. 相似文献
6.
A. Frisch H. Levkowitz A. Loyter 《Biochemical and biophysical research communications》1976,72(1):138-145
Tunicamycin, a glucosamine-containing antibiotic inhibited the conjugation process of Tetrahymena pyriformis. Sexual pairing was prevented completely when 1.5 μg/ml of tunicamycin was added to a mixture of the two mating types. Tunicamycin caused preferential inhibition of glycoprotein synthesis in Tetrahymena pyriformis. At 1.5 μg/ml and 6 μg/ml tunicamycin inhibited by 40% and 60% respectively [3H]-glucosamine incorporation into material precipitated by ethanol, while it did not affect [14C]-leucine incorporation. Cell division was also inhibited when the drug was added either to the regular growth medium or to the starvation medium. 相似文献
7.
Jack D. Anderson Roland K. Robins Ganapathi R. Revankar 《Nucleosides, nucleotides & nucleic acids》2013,32(5):853-863
Abstract The synthesis of pyrazolo[3,4-d]pyrimidine ribonucleoside 3′, 5′-cyclic phosphates related to cAMP, cIMP and cGMP has been achieved for the first time. Phosphorylation of 4-amino-6-methylthio-1-β-D-ribo-furanosylpyrazolo[3,4-d]pyrimidine (1) with POCl3 in trimethyl phosphate gave the corresponding 5′-phosphate (2a). DCC mediated intramolecular cyclization of 2a gave the corresponding 3′, 5′-cyclic phosphate (3a), which on subsequent dethiation provided the cAMP analog 4-amino-1-β-D-ribofuranosylpyrazolo[3, 4-d]pyrimidine 3′, 5′-cyclic phosphate (3b). A similar phosphorylation of 6-methylthio-1-β-D-ribofuranosylpyrazolo[3, 4-d]pyrimidin-4(5H)-one (5), followed by cyclization with DCC gave the 3′, 5′-cyclic phosphate of 5 (9a). Dethiation of 9a with Raney nickel gave the cIMP analog 1-β-D-ribofuranosylpyrazolo[3, 4-d]pyrimidin-4(5H)-one 3′, 5′-cyclic phosphate (9b). Oxidation of 9a with m-chloroperoxy benzoic acid, followed by ammonolysis provided the cGMP analog 6-amino-1-β-D-ribofuranosylpyrazolo [3, 4-d] pyrimidin-4(5H)-one 3′, 5′-cyclic phosphate (7). The structural assignment of these cyclic nucleotides was made by UV and H NMR spectroscopic studies. 相似文献
8.
Abstract 6-(3-methyl-2-butenylamino)-2-methylthio-9-(β-D-ribofuranosyl)purine (1) is a naturally occurring nucleoside with potent cytokinin activity. It has been isolated and identified in the t-RNA of E. coli,1,2 the t-RNA from wheat germ3,4 and from Staphylococcus epidermidis.5 In addition, compound 1 has been found in t-RNA species corresponding to each of six amino acids whose codons start with uridine, i.e., t-RNACys 相似文献
9.
Direct somatic embryogenesis on immature zygotic embryos in vitro has been confirmed for Trifolium pratense and extended to T. resupinatum and T. subterraneum. For all species direct embryo cloning can be achieved on an appropriate basal medium supplemented with 1gl–1 yeast extract and 0.05 mgl–1 BAP. Basal medium/sucrose formulation, level of yeast extract and level of BAP affected the nature of in vitro responses. In particular, for T. pratense and T. subterraneum lowering of the yeast extract level suppressed embryoid initiation, and raising of the BAP level stimulated formation of nodular morphogenic callus. For T. resupinatum alteration of the basal medium/sucrose formulation changed the tissue site of embryoid initiation from hypocotyl to cotyledons or both. Control of embryoid initiation is briefly discussed.Abbreviation BAP
6-benzylaminopurine 相似文献
10.
《Insect Biochemistry》1986,16(1):17-23
The synthesis of [4-14C]cholesta-4,6-dien-3-one and [4-14C]3β-hydroxy-5α-cholestan-6-one is described. Both [4-14C]cholest-4-en-3-one and [4-14C]cholesta-4,6-dien-3-one were not incorporated significantly into ecdysteroids compared to [1α,2α-3H]cholesterol in fifth instar and maturing adult female Schistocerca gregaria. Similarly, [4-14C]3β-hydroxy-5α-cholestan-6-one was not incorporated significantly in the latter system. The results suggest that none of the three 14C-substrates are intermediates in ecdysteroid biosynthesis from cholesterol, although possible complications from permeability barriers cannot be discounted. [4-14C, 7-3H]7-dehydrocholesterol has been synthesized and incorporated into ecdysteroids in adult female Schistocerca gregaria and in Spodoptera littoralis pupae. Although approximately half the tritium was eliminated during ecdysteroid synthesis in S. gregaria, there was essentially complete retention of the tritium in Spodoptera. The results support the direct incorporation of 7-dehydrocholesterol into ecdysteroids and not via cholesterol. A possible explanation for the loss of appreciable tritium in S. gregaria is discussed. 相似文献
11.
A. Földesi T. V. Maltseva J. Chattopadhyaya 《Nucleosides, nucleotides & nucleic acids》2013,32(6-7):1377-1378
Abstract We have recently shown1 the usefulness of 2H, 13C-labelled 2′-deoxynu-cleoside building blocks for structural studies via relaxation time measurements. The synthesis of phosphoramidite blocks 11 and 12 for their site-specific incorporation (indicated by underlines) into the d5′(1C2G3 A 4 T 5 T 6 A 7 A 8 T 9C10G)2 3′ is briefly described for studying the T1 and T1[sgrave] relaxations of 2H and 13C at specific deuterated carbons in a large molecule. 相似文献
12.
《Journal of molecular biology》2021,433(23):167279
Several molecular mechanisms are involved in the genetic code interpretation during translation, as codon degeneration for the incorporation of rare amino acids. One mechanism that stands out is selenocysteine (Sec), which requires a specific biosynthesis and incorporation pathway. In Bacteria, the Sec biosynthesis pathway has unique features compared with the eukaryote pathway as Ser to Sec conversion mechanism is accomplished by a homodecameric enzyme (selenocysteine synthase, SelA) followed by the action of an elongation factor (SelB) responsible for delivering the mature Sec-tRNASec into the ribosome by the interaction with the Selenocysteine Insertion Sequence (SECIS). Besides this mechanism being already described, the sequential events for Sec-tRNASec and SECIS specific recognition remain unclear. In this study, we determined the order of events of the interactions between the proteins and RNAs involved in Sec incorporation. Dissociation constants between SelB and the native as well as unacylated-tRNASec variants demonstrated that the acceptor stem and variable arm are essential for SelB recognition. Moreover, our data support the sequence of molecular events where GTP-activated SelB strongly interacts with SelA.tRNASec. Subsequently, SelB.GTP.tRNASec recognizes the mRNA SECIS to deliver the tRNASec to the ribosome. SelB in complex with its specific RNAs were examined using Hydrogen/Deuterium exchange mapping that allowed the determination of the molecular envelopes and its secondary structural variations during the complex assembly. Our results demonstrate the ordering of events in Sec incorporation and contribute to the full comprehension of the tRNASec role in the Sec amino acid biosynthesis, as well as extending the knowledge of synthetic biology and the expansion of the genetic code. 相似文献
13.
Production of canthin-6-one alkaloids by cell suspension cultures of Brucea javanica (L.) Merr. 总被引:1,自引:0,他引:1
Karin C. -S. Liu Shi-Lin Yang Margaret F. Roberts J. David Phillipson 《Plant cell reports》1990,9(5):261-263
Cell suspension cultures of Brucea javanica (L.) Merr. were used to determine culture growth characteristics and production of canthin-6-one alkaloids. The major alkaloids produced were canthin-6-one, 11-hydroxycanthin-6-one, 5-methoxycanthin-6-one and 11-methoxycanthin-6-one. Alkaloids were synthesised throughout the 36 day growth cycle of the cells with maximum amounts within the cells occurring between days 20 to 28; approximately 10% of the alkaloids were in the medium at day 24 rising to 45% at day 32. 相似文献
14.
15.
Summary A two step continuous aerobic process is proposed for treating cane sugar stillage. In the first step the original stillage is used for growing aCandida utilis and the supernatant of this process is used for feeding the second step where aPaecilomyces strain is grown without addition of nutrients. A total reduction of COD of 87% and a mixed biomass output of 2.3–2.6 gl-1h-1 are attained. 相似文献
16.
Leonidas Kiriasis Wolfgang Pfleiderer 《Nucleosides, nucleotides & nucleic acids》2013,32(7):1345-1358
Abstract Model reactions with 2-methylthiopteridin-4,7(3H,8H)-diones (3-5) and 4-benzyloxy-8-methyl-2-thiopteridin-7(8H)-one (11) showed that peracid oxidations lead to the corresponding 2-methylsulfonyl-6-oxo derivatives 8, 9, 10 and 12. The structurally analogous pteridine-N-8-ribosides 19-21 and 26 revealed the same behaviour, which allowed the synthesis of 8-β-D-ribofuranosylleu-copterin (30) from 4-benzyloxy-8-(2,3,5-tri-O-benzoyl-β-D-ribofu-ranosyl)-2-methylthio-pteridi-7(8H)-one (26) via the intermediates 27-29. The newly synthesized compounds have been characterized by elemental analysis and UV spectra. 相似文献
17.
Boaz Avron Robert N. Deutsch David Mirelman 《Biochemical and biophysical research communications》1982,108(2):815-821
Cysts of Entamoeba invadens obtained under axenic culture conditions have been reported to be similar to cysts of the human intestinal parasite E histolytica both in morphology and chitin presence in their wails. Mature E. invadens cyst forms, isolated from cultures following discontinuous Percoll gradient sedimentation were resistant (>80%) to detergent treatment. Addition of chitin synthesis inhibitors such as Polyoxin D and Nikkomycin (50 μg/ml) to cultures in encystation media markedly inhibited (>85%) the formation of detergent resistant cysts and prevented the incorporation of radiolabeled chitin precursor N-acetyl[3H]glucosamine. These findings suggest that chitin synthesis inhibitors may serve as drugs which specifically block the life cycle of the Entamoeba parasite. 相似文献
18.
Summary A method has been developed for rapid mondtoring of lipid production in the intact yeast cells ofRhodotorula
gracilis using1H NMR spectroscopy. 相似文献
19.
Unlabelled cadaverine did not diminish the incorporation into anabasine of 14C from L-[U-14C] lysine supplied to hairy root cultures of Nicotiana nesperis, despite causing a stimulation of anabasine production. The finding is discussed in the context of previous observations indicating that free cadaverine is not an intermediate in the biosynthesis of anabasine from lysine. 相似文献
20.
The molecular conformation of d1-8-isotestosterone has been determined crystallographically. Crystals of the title compound belong to the space group P21/c with a = 11.449(4), b = 10.962(4), c = 25.860(5) , β = 100.95(4)0, with two molecules in the asymmetric unit. The structure has been refined to a final R value of 0.052 for 2227 reflections. Unlike testosterone, which is a flat molecule, its 8-isomer has a folded conformation. The conformations of the ring-B in the two crystallographically independent molecules (A and B) correspond to the twist form and differ significantly from one another. 相似文献