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1.
Chapman H Kernan M Prisbe E Rohloff J Sparacino M Terhorst T Yu R 《Nucleosides, nucleotides & nucleic acids》2001,20(4-7):621-628
The practical synthesis of a mixed phenoxy-amidate derivative of PMPA with high oral bioavailability and favorable pharmacokinetics is described. The non-stereoselective synthetic route produces a 1:1 mixture of two diastereomers at phosphorous. Simulated moving bed chromatography using Chiralpak AS enabled kilo-scale isolation of the more potent diastereomer (GS-7340). The GS-7340 phosphorous chiral center was found to be (S) by X-ray crystallography. 相似文献
2.
《Nucleosides, nucleotides & nucleic acids》2013,32(4-7):1091-1098
PMPA, an acyclic nucleoside phosphonate analog, is a potent inhibitor of HIV. In the cells, PMPA is efficiently phosphorylated by intracellular kinases to produce PMPApp, the pharmacologically active metabolite. Despite its demonstrated antiviral potency, PMPA has limited cell permeability presumably resulting from the presence of two negative charges on the phosphonyl group. To enhance intracellular concentrations of PMPA, we developed a prodrug, selectively metabolized inside cells. GS-7340 (9-[R)-2-[[[[S)-1-(isopropoxycarbonyl)ethyl] amino] phenoxy-phosphinyl]-methoxy] propyl] adenine) is a prodrug which is orally bioavailable in dogs as the intact prodrug and has demonstrated anti-HIV activity in cell culture of over 1000-fold greater than that of PMPA. The metabolism of PMPA in peripheral blood mononuclear cells (PBMC), red blood cells (RBC) and plasma was examined following exposure of whole blood to PMPA or GS-7340 at concentrations similar to ones observed systemically following oral administration in dogs. Following 1 hour incubation with whole blood, GS-7340 was stable in plasma, produced high levels of PMPA and its phosphorylated metabolites in PBMC but not in RBC. No intact prodrug was present in PBMC. The only other species present in PBMC was monoalaninyl PMPA. The levels of PMPA and the phosphorylated metabolites were over 20 times greater than those after incubation with PMPA. The dog and human blood data were similar. The intracellular levels of PMPA and PMPApp were roughly proportional to GS-7340 over a 10-fold concentration range indicating a lack of saturability of uptake and phosphorylation. Since PMPApp is the species responsible for antiviral activity of PMPA, the high intracellular levels of PMPApp should be an important indicator of greater clinical efficacy of GS-7340. 相似文献
3.
PMPA, an acyclic nucleoside phosphonate analog, is a potent inhibitor of HIV. In the cells, PMPA is efficiently phosphorylated by intracellular kinases to produce PMPApp, the pharmacologically active metabolite. Despite its demonstrated antiviral potency, PMPA has limited cell permeability presumably resulting from the presence of two negative charges on the phosphonyl group. To enhance intracellular concentrations of PMPA, we developed a prodrug, selectively metabolized inside cells. GS-7340 (9-[(R)-2-[[[[(S)-1-(isopropoxycarbonyl)ethyl] amino] phenoxy-phosphinyl]-methoxy] propyl] adenine) is a prodrug which is orally bioavailable in dogs as the intact prodrug and has demonstrated anti-HIV activity in cell culture of over 1000-fold greater than that of PMPA. The metabolism of PMPA in peripheral blood mononuclear cells (PBMC), red blood cells (RBC) and plasma was examined following exposure of whole blood to PMPA or GS-7340 at concentrations similar to ones observed systemically following oral administration in dogs. Following 1 hour incubation with whole blood, GS-7340 was stable in plasma, produced high levels of PMPA and its phosphorylated metabolites in PBMC but not in RBC. No intact prodrug was present in PBMC. The only other species present in PBMC was monoalaninyl PMPA. The levels of PMPA and the phosphorylated metabolites were over 20 times greater than those after incubation with PMPA. The dog and human blood data were similar. The intracellular levels of PMPA and PMPApp were roughly proportional to GS-7340 over a 10-fold concentration range indicating a lack of saturability of uptake and phosphorylation. Since PMPApp is the species responsible for antiviral activity of PMPA, the high intracellular levels of PMPApp should be an important indicator of greater clinical efficacy of GS-7340. 相似文献
4.
《Nucleosides, nucleotides & nucleic acids》2013,32(4-7):1085-1090
The diastereomers of GS-7171, aryl phosphoramidate derivatives of the anti-HIV nucleotide analog 9-[2-R-(phosphonomethoxy)propyl]adenine (tenofovir, PMPA), were isolated by batch elution chromatography and continuous simulated moving bed chromatography. The absolute configuration of the more pharmacologically active diastereomer, GS-7340, was determined to be (R,S,S) by single crystal x-ray crystallography. 相似文献
5.
Chapman H Kernan M Rohloff J Sparacino M Terhorst T 《Nucleosides, nucleotides & nucleic acids》2001,20(4-7):1085-1090
The diastereomers of GS-7171, aryl phosphoramidate derivatives of the anti-HIV nucleotide analog 9-[2-R-(phosphonomethoxy)propyl]adenine (tenofovir, PMPA), were isolated by batch elution chromatography and continuous simulated moving bed chromatography. The absolute configuration of the more pharmacologically active diastereomer, GS-7340, was determined to be (R,S,S) by single crystal x-ray crystallography. 相似文献
6.
Mesophyll cells (MCs) and bundle-sheath cells (BSCs) of leaves of the C4 plant maize (Zea mays L.) were separated by cellulase digestion to determine the relative proportion of the glutamine synthetase (GS; EC 6.3.1.2)
or the NADH-glutamate dehydrogenase (GDH; EC 1.4.1.2) isoforms in each cell type. The degree of cross-contamination between
our MC and BSC preparations was checked by the analysis of marker proteins in each fraction. Nitrate reductase (EC 1.6.6.1)
proteins (110 kDa) were found only in the MC fraction. In contrast, ferredoxin-dependent glutamate synthase (Fd-GOGAT; EC
1.4.7.1) proteins (160 kDa) were almost exclusively present in the BSC fraction. These results are consistent with the known
intercellular distribution of nitrate reductase and Fd-GOGAT proteins in maize leaves and show that the cross-contamination
between our MC and BSC fractions was very low. Proteins corresponding to cytosolic GS (GS-1) or plastidic GS (GS-2) were found
in both the MC and BSC fractions. While equal levels of GS-1 (40 kDa) and GS-2 (44 kDa) polypeptides were present in the BSC
fraction, the GS-1 protein level in the MC fraction was 1.8-fold higher than the GS-2 protein pool. Following separation of
the GS isoforms by anion-exchange chromatography of MC or BSC soluble protein extracts, the relative GS-1 activity in the
MC fraction was found to be higher than the relative GS-2 activity. In the BSC fraction, the relative GS-1 activity was very
similar to the relative GS-2 activity. Two isoforms of GDH with apparent molecular weights of 41 kDa and 42 kDa, respectively,
were detected in the BSC fraction of maize leaves. Both GDH isoenzymes appear to be absent from the MC fraction. In the BSCs,
the level of the 42-kDa GDH isoform was 1.7-fold higher than the level of the 41-kDa GDH isoform. A possible role for GS-1
and GDH co-acting in the synthesis of glutamine for the transport of nitrogen is discussed.
Received: 25 January 2000 / Accepted: 30 March 2000 相似文献
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Analysis of an exopolysaccharide of Sphingomonas paucimobilis GS-1 (EPS/GS-1) with respect to its rheological properties, cross-linking ability with chrome alum and performance test at
75 ± 5°C revealed its strong suspending ability, shear thinning property, and thixotrophic nature which are required to impart
desirable rheology to drilling mud. The organism fulfilled all the specified requirements and its properties were superior
to those of currently-used XC polymer (a xanthan product) for oil drilling applications. However, EPS/GS-1 was unstable in
the presence of bentonite at 100 ± 5°C during performance tests, in contrast to XC polymer.
Received 14 April 1999/ Accepted in revised form 26 July 1999 相似文献
10.
The effect of CO2 concentration on the rate of photorespiratory ammonium excretion and on glutamine synthetase (GS) and carbonic anhydrase (CA) isoenzymes activities has been studied in Chlamydomonas reinhardtii cw-15 mutant (lacking cell wall) and in the high CO2-requiring double mutant cia-3/cw-15 (lacking cell wall and chloroplastic carbonic anhydrase). In cw-15 cells, both the extracellular (CAext) and chloroplastic (CAchl) CA activities increased after transferring cells from media bubbled with 5% CO2 in air (v/v, high-Ci cells) to 0.03% CO2 (low-Ci cells), whereas in cia-3/cw-15 cells only the CAext was induced after adaptation to low-Ci conditions and the CAchl activity was negligible. During adaptation to low-Ci conditions in the presence of 1 mM of l-methionine-D,L-sulfoximine (MSX), a specific inhibitor of GS activity, both mutant strains excreted photorespiratory ammonium into nitrogen free medium. In addition, the ammonium excretion rate by cw-15 in the presence of MSX was lower in cells grown and kept at 5% CO2 than in high-Ci cells adapted to 0.03% CO2. The double mutant cia-3/cw-15 excreted photorespiratory ammonium at a higher rate than did cw-15. Total GS activity (GS-1 plus GS-2) increased during adaptation to 0.03% CO2 in both strains of C. reinhardtii. However, only the activity GS-2, which is located in the chloroplast, increased during the adaptation to low CO2, whereas the cytosolic GS-1 levels remained similar in high and low-Ci cells. We conclude that: (1) cia-3/cw-15 cells lack chloroplastic CA activity; (2) in C. reinhardtii photorespiratory ammonium is refixed in the chloroplasts through the GS-2/GOGAT cycle; and (3) chloroplastic GS-2 concentration changes in response to the variation of environmental CO2 concentration. 相似文献
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Romano JE 《Theriogenology》1994,41(6):1273-1277
The object of this research was to study the effect of sterile service number on estrus duration in dairy goats. Twenty-four Nubian goats (20 nulliparous and 4 multiparous) were randomly assigned to 1 of 4 treatment groups (n = 6 animals per group). The following Groups were formed: no service (GS-0); 1 service (GS-1); 2 services (GS-2); 3 services (GS-3). Estrus was synchronized by using fluorogestone acetate intravaginal pessaries (40 mg) over a 12-d period plus 400 IU im pregnant mare serum gonadotropin (PMSG) at pessary removal. Estrus was detected by using a vasectomized buck at 6-h intervals over 5 d after pessary removal (at 0600, 1200, 1800 and 2400 h). In the GS-0 group the teaser was outfitted with an apron and was permitted to mount. In the GS-1, GS-2 and GS-3 groups, the teaser was permitted to mount and service 1, 2 and 3 times, respectively, within the first 12 h after initiation of estrus. The duration of estrus for the 4 groups (GS-0, GS-1, GS-2 and GS-3) was (mean +/- SD) 41.0 +/- 5.9, 24.0 +/- 5.4, 22.0 +/- 4.9 and 22.0 +/- 7.2 h, respectively. These results show differences between the serviced groups and the nonserviced group (P<0.01), but they fail to show differences among the serviced groups (P>0.05). It is concluded that sterile service shortens estrus duration and that service number (1, 2 or 3) does not affect estrus duration. 相似文献
14.
Thomas W. Becker Michel Caboche Elisa Carrayol Bertrand Hirel 《Plant molecular biology》1992,19(3):367-379
15.
The effects of GS-389, a novel tetrahydroisoquinoline analog, on isolated rat and mouse thoracic aorta rings, were investigated. Both GS-389 and papaverine induced endothelium-independent, concentration-dependent relaxations of the rat and mouse aortae precontracted with phenylephrine (PE). The GS-389-induced inhibition of the contractile response to PE was noncompetitive. The initial phasic contraction to PE elicited in Ca(2+)-free media was also attenuated by pretreatment with GS-389, indicating that GS-389 may interfere with the release of intracellular Ca2+ and/or the effects of intracellular Ca2+ release. GS-389 potentiated the vasodilatory effects of isoproterenol and sodium nitroprusside in rat and mouse aortae. GS-389 significantly increased cGMP levels in the rat aorta and inhibited cGMP phosphodiesterase from the rabbit brain. Methylene blue, but not propranolol, inhibited the vasodilatory effect of GS-389. These results suggest that the vasorelaxant effect of GS-389 may be due, at least in part, to inhibition of cGMP metabolism. 相似文献
16.
Anaerobic Oxidation of Toluene, Phenol, and p-Cresol by the Dissimilatory Iron-Reducing Organism, GS-15 总被引:36,自引:24,他引:12
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The dissimilatory Fe(III) reducer, GS-15, is the first microorganism known to couple the oxidation of aromatic compounds to the reduction of Fe(III) and the first example of a pure culture of any kind known to anaerobically oxidize an aromatic hydrocarbon, toluene. In this study, the metabolism of toluene, phenol, and p-cresol by GS-15 was investigated in more detail. GS-15 grew in an anaerobic medium with toluene as the sole electron donor and Fe(III) oxide as the electron acceptor. Growth coincided with Fe(III) reduction. [ring-14C]toluene was oxidized to 14CO2, and the stoichiometry of 14CO2 production and Fe(III) reduction indicated that GS-15 completely oxidized toluene to carbon dioxide with Fe(III) as the electron acceptor. Magnetite was the primary iron end product during toluene oxidation. Phenol and p-cresol were also completely oxidized to carbon dioxide with Fe(III) as the sole electron acceptor, and GS-15 could obtain energy to support growth by oxidizing either of these compounds as the sole electron donor. p-Hydroxybenzoate was a transitory extracellular intermediate of phenol and p-cresol metabolism but not of toluene metabolism. GS-15 oxidized potential aromatic intermediates in the oxidation of toluene (benzylalcohol and benzaldehyde) and p-cresol (p-hydroxybenzylalcohol and p-hydroxybenzaldehyde). The metabolism described here provides a model for how aromatic hydrocarbons and phenols may be oxidized with the reduction of Fe(III) in contaminated aquifers and petroleum-containing sediments. 相似文献
17.
Structure-based drug design has led to the introduction of three drugs — oseltamivir (GS-4104), zanamivir (GG-167) and peramivir (RWJ-270201) which target the enzyme neuraminidase, for treatment of influenza infections. Using comparative docking studies we propose that more potent molecules against neuraminidase can be obtained by appending extra positively charged substituents at the C5 position of the oseltamivir skeleton. This provides an additional interaction with the enzyme and may overcome the problem of resistance encountered with these drugs. To get an insight into the transport and absorption of oseltamivir — the ethyl ester prodrug (GS-4104) as well as its mechanism of action, we have carried out 1H, 13C, 31P NMR, DSC and TEM studies on GS-4104 with model membranes prepared from DMPC/DPPC/POPC. These studies reveal that interactions between GS-4104 and the membrane are both electrostatic (involving H-bonding) and hydrophobic (involving the hydrophobic chain and cyclohexene ring of GS-4104) in nature. The prodrug is seen to increase the fluidity as well as stabilize the bilayer phase of the membrane. This property may be responsible for preventing viral entry into the cells by preventing fusion of the virus outer coat with the cell membrane. 相似文献
18.
The ionic mechanism of action of a spin-labeled local anesthetic (SLA), 2-[N-methyl-N-(2,2,6,6-tetramethylpiperidonooxyl)]-ethyl 4-ethoxylbenzoate, was studied by means of voltage clamp technique with squid giant axons in comparison with the parent compound without spin label moiety, 2-(N,N-dimethyl)ethyl 4-ethoxylbenzoate (GS-01). Like other local anesthetics, they suppressed both sodium and potassium conductance increases. However, three remarkable differences have been noted between SLA and GS-01: (1) SLA is more effective than GS-01 in suppressing the sodium and potassium conductance increases; (2) SLA induces a potassium inactivation, whereas GS-01 is lacking this ability; (3) SLA has no effect on the time to peak sodium current, whereas GS-01 prolongs it. GS-01 resembles procaine with respect to (2) and (3) above. SLA will become a useful probe for the study of the molecular mechanism of local anesthetic aciton and of ionic channel function. 相似文献
19.
Silpa Narayanan Zhuo-Xun Wu Jing-Quan Wang Hansu Ma Nikita Acharekar Jagadish Koya Sabesan Yoganathan Shuo Fang Zhe-Sheng Chen Yihang Pan 《International journal of biological sciences》2021,17(10):2652
Tyrosine kinase inhibitors (TKIs) are important in managing lymphoid malignancies by targeting B-cell receptor signaling pathways. Entospletinib (GS-9973) is an oral, selective inhibitor of spleen tyrosine kinase (Syk), currently in the phase II clinical trials for the treatment of chronic lymphocytic leukemia. Syk is abundantly present in the cells of hematopoietic lineage that mediates cell proliferation, differentiation, and adhesion. In this current study, we evaluated the efficacy of GS-9973 to overcome multidrug resistance (MDR) due to the overexpression of the ABCG2 transporter in the non-small cell lung cancer (NSCLC) cell line, NCI-H460/MX20. In vitro, 3 μM of GS-9973 reversed the drug resistance of NCI-H460/MX20 cell line to mitoxantrone or doxorubicin. GS-9973, at 3 μM reverses ABCG2-mediated MDR by blocking ABCG2 efflux activity and downregulating ABCG2 expression at the protein level but did not alter the ABCG2 mRNA expression and subcellular localization of the ABCG2 protein compared to drug-resistant cells incubated with the vehicle. GS-9973 produced a moderate concentration-dependent increase in the ATPase activity of ABCG2 (EC50 = 0.42 µM) and molecular docking data indicated that GS-9973 had a high affinity (-10.226 kcal/mol) for the substrate-binding site of ABCG2. Finally, HPLC analysis proved that the intracellular concentration of GS-9973 is not significantly different in both parental and resistant cell lines. In conclusion, our study suggests that in vitro, GS-9973 in combination with certain anticancer drugs, represent a strategy to overcome ABCG2-mediated MDR cancers. 相似文献
20.
Ona Barauskas Amoreena C. CorsaRuth Wang Scott HluhanichDebi Jin Magdeleine HungHuiling Yang William E. Delaney IVBrian E. Schultz 《Biochimica et Biophysica Acta (BBA)/General Subjects》2014