盾叶薯蓣地上部分的三个新甾体皂甙

从盾叶薯蓣Dioscorea zingiberensis Wright地上部分分离鉴定了四个甾体皂甙,经鉴定甙A为约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)]-β-D-葡萄吡喃糖甙;甙B为24α-羟基约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)]β-D-葡萄吡喃糖甙;甙C为约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)][β-D-葡萄吡喃糖基(1→4)]-β-D-葡萄吡喃糖基;甙D为约莫皂甙元-3-O-[α-L-鼠李吡喃糖基(1→2)][β-D-葡萄吡喃糖基(1→3)]-β-D-葡萄吡喃糖甙。前三者为新化合物,分别命名为盾叶皂甙A_1、A_2、A_3(zingiberoside A_1、A_2、A_3),其中盾叶皂甙A_2的甙元为一新甾体皂甙元,命名为盾叶皂甙元(zingiberogenin)。     

Metabolism of D-myo-inositol 1,3,4,5-tetrakisphosphate by rat liver, including the synthesis of a novel isomer of myo-inositol tetrakisphosphate.

1. We have studied the metabolism of Ins(1,3,4,5)P4 (inositol 1,3,4,5-tetrakisphosphate) by rat liver homogenates incubated in a medium resembling intracellular ionic strength and pH. 2. Ins(1,3,4,5)P4 was dephosphorylated to a single inositol trisphosphate product, Ins(1,3,4)P3 (inositol 1,3,4-trisphosphate), the identity of which was confirmed by periodate degradation, followed by reduction and dephosphorylation to yield altritol. 3. The major InsP2 (inositol bisphosphate) product was inositol 3,4-bisphosphate [Shears, Storey, Morris, Cubitt, Parry, Michell & Kirk (1987) Biochem. J. 242, 393-402]. Small quantities of a second InsP2 product was also detected in some experiments, but its isomeric configuration was not identified. 4. The Ins(1,3,4,5)P4 5-phosphatase activity was primarily associated with plasma membranes. 5. ATP (5 mM) decreased the membrane-associated Ins(1,4,5)P3 5-phosphatase and Ins(1,3,4,5)P4 5-phosphatase activities by 40-50%. This inhibition was imitated by AMP, adenosine 5'-[beta gamma-imido]triphosphate, adenosine 5'-[gamma-thio]triphosphate or PPi, but not by adenosine or Pi. A decrease in [ATP] from 7 to 3 mM halved the inhibition of Ins(1,3,4,5)P4 5-phosphatase activity, but the extent of inhibition was not further decreased unless [ATP] less than 0.1 mM. 6. Ins(1,3,4,5)P4 5-phosphatase was insensitive to 50 mM-Li+, but was inhibited by 5 mM-2,3-bisphosphoglycerate. 7. The Ins(1,3,4,5)P4 5-phosphatase activity was unchanged by cyclic AMP, GTP, guanosine 5'-[beta gamma-imido]triphosphate or guanosine 5'-[gamma-thio]triphosphate, or by increasing [Ca2+] from 0.1 to 1 microM. 8. Ins(1,3,4)P3 was phosphorylated in an ATP-dependent manner to an isomer of InsP4 that was partially separable on h.p.l.c. from Ins(1,3,4,5)P4. The novel InsP4 appears to be Ins(1,3,4,6)P4. Its metabolic fate and function are not known.     

A Pseudomonas stutzeri outer membrane protein inserts copper into N2O reductase

Among a set of frameshift mutagen (ICR-191; Polysciences, Inc.)-induced mutations that confer inability to grow anaerobically with N2O as the sole electron acceptor, one class was found that produced an inactive N2O reductase which lacked copper. All of these mutant strains failed to produce a 61,000-Mr protein located in the outer membrane. This protein, termed NosA, seems not to be responsible for bringing copper into the cell because the mutant strains and their parent were similarly sensitive to the copper content of the growth medium and no intermediate copper concentration in the medium permitted the mutant strains (nosA) to grow anaerobically with N2O as the sole electron acceptor. We conclude that NosA is necessary to insert copper into N2O reductase or to maintain it there.     

Photosensitized cleavage of dynein heavy chains. Cleavage at the V2 site by irradiation at 365 NM in the presence of oligovanadate

Irradiation of the outer-arm dynein ATPase from sea urchin sperm flagella at 365 nm in the presence of 50-200 microM vanadate (Vi) and 1 mM manganese acetate, in the absence of ATP, cleaves the alpha and beta heavy chains at a specific site, termed the V2 site, to form discrete peptides of Mr approximately 260,000 and 170,000 from the alpha chain and of Mr approximately 255,000 and 175,000 from the beta chain, with a yield of 80%. This cleavage at the V2 site is not correlated with any direct effect on the dynein ATPase activity. In the presence of 100 microM Vi, the half-times for cleavage of the alpha and beta chains are about 12 and 50 min, respectively. The rate of heavy chain cleavage shows a sigmoidal dependence upon Vi concentration, with half-maximal rate occurring at 58 +/- 7 microM, consistent with the chromophore responsible for cleavage being tri-vanadate. Addition of 10 microM ATP or ADP, or of 100 microM CTP or UTP, to the irradiation medium inhibits cleavage at the V2 site, and results in a slow cleavage occurring at the V1 site described previously. The peptides produced by sequential cleavage at the V2 and then the V1 sites indicate that the sites are separated by about 100,000 Da along the length of each heavy chain. Photoaffinity labeling with [alpha-32P] 8-azidoadenosine 5'-triphosphate (8-N3ATP) gives specific incorporation of 32P into both the Mr 255,000 and 175,000 peptides of the beta chain but into only the Mr 260,000 peptide of the alpha chain. These results suggest that V2 cleavage occurs on a loop of the heavy chain that forms part of the ATP-binding site, close to the locus of 8-N3ATP attachment.     

Estrogen influences dolichyl phosphate distribution among glycolipid pools in mouse uteri

The steroid hormone 17 beta-estradiol dramatically induces uterine N-linked glycoprotein assembly [Dutt, A., Tang, J.-P., Welply, J. K., & Carson, D. D. (1986) Endocrinology (Baltimore) 118, 661-673]. To determine the role that dolichyl phosphate availability plays in this induction, we studied the effects of estrogen priming on the content of dolichyl phosphate and the distribution of dolichyl phosphate among various glycolipids in uteri. Dolichol-linked saccharides were metabolically labeled to equilibrium with either [3H]glucosamine or [3H]mannose and extracted from primary explants of uterine tissue. The amount of dolichol-linked saccharide was calculated from the specific radioactivity determined for the corresponding sugar nucleotides extracted from the tissues. The major dolichol-linked saccharides identified were mannosylphosphoryldolichol (MPD), oligosaccharylpyrophosphoryldolichol (OSL), and N,N'-diacetylchitobiosylpyrophosphoryldolichol (CBL). Estrogen increased the levels of MPD and OSL 4-fold; however, CBL levels did not change. After 3 days of treatment, the levels of these glycolipids were very similar to those in uteri from pregnant mice. Remarkably, MPD constituted 90-95% of dolichol-linked saccharides detected under all conditions. The tissue contents of total dolichyl phosphate and alkali-labile dolichyl phosphate, presumably MPD, were estimated by liquid chromatography. The levels of alkali-labile dolichyl phosphate determined in this way were in good agreement with the values estimated for MPD by metabolic labeling; moreover, alkali-labile dolichyl phosphate constituted 50-98% of the total dolichyl phosphate pool. The variations in MPD content depended upon the steroid hormone influence, most notably that of estrogen.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of mutation in human cells by using an Epstein-Barr virus shuttle system.

We developed highly sensitive shuttle vector systems for detection of mutations formed in human cells using autonomously replicating derivatives of Epstein-Barr virus (EBV). EBV vectors carrying the bacterial lacI gene as the target for mutation were established in human cells and later returned to Escherichia coli for rapid detection and analysis of lacI mutations. The majority of the clonal cell lines created by establishment of the lacI-EBV vector show spontaneous LacI- frequencies of less than 10(-5) and are suitable for studies of induced mutation. The ability to isolate clonal lines represents a major advantage of the EBV vectors over transiently replicating shuttle vectors (such as those derived from simian virus 40) for the study of mutation. The DNA sequence changes were determined for 61 lacI mutations induced by exposure of one of the cell lines to N-nitroso-N-methylurea. A total of 33 of 34 lacI nonsense mutations and 26 of 27 missense mutations involve G X C to A X T transitions. These data provide support for the mutational theory of cancer.     

柚花头香化学成分的研究(一)

本文首次报道柚花的香气成分。作者利用憎水性树脂XAD-4吸附柚鲜花的头香,并以毛细管气相色谱和毛细管气相色谱-质谱-计算机联用方法研究头香的化学组分,分离鉴定了17个已知化学成分。它们是芳樟醇、β-蒎烯、β-水芹烯、橙花叔醇等。