bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cloning and Expression of Cytochrome P450 Enzymes Catalyzing the Conversion of Tyrosine to p-Hydroxyphenylacetaldoxime in the Biosynthesis of Cyanogenic Glucosides in Triglochin maritima
Authors: Nielsen John Strikart , Møller Birger Lindberg 
Published: July 2002

Abstract
Two cDNA clones encoding cytochrome P450 enzymes belonging to the CYP79 family have been isolated fromTriglochin maritima. The two proteins show 94% sequence identity and have been designated CYP79E1 and CYP79E2. Heterologous expression of the native and the truncated forms of the two clones inEscherichia coli demonstrated that both encode multifunctional N-hydroxylases catalyzing the conversion of tyrosine to p-hydroxyphenylacetaldoxime in the biosynthesis of the two cyanogenic glucosides taxiphyllin and triglochinin in T. maritima. This renders CYP79E functionally identical to CYP79A1 from Sorghum bicolor, and unambiguously demonstrates that cyanogenic glucoside biosynthesis in T. maritima and S. bicolor is catalyzed by analogous enzyme systems withp-hydroxyphenylacetaldoxime as a free intermediate. This is in contrast to earlier reports stipulatingp-hydroxyphenylacetonitrile as the only free intermediate in T. maritima.l-3,4-Dihydroxyphenyl[3-14C]Ala (DOPA) was not metabolized by CYP79E1, indicating that hydroxylation of the phenol ring at the meta position, as required for triglochinin formation, takes place at a later stage. In S. bicolor, CYP71E1 catalyzes the subsequent conversion ofp-hydroxyphenylacetaldoxime top-hydroxymandelonitrile. When CYP79E1 from T. maritima was reconstituted with CYP71E1 and NADPH-cytochrome P450 oxidoreductase from S. bicolor, efficient conversion of tyrosine to p-hydroxymandelonitrile was observed.
Regulation of Carbonic Anhydrase Expression by Zinc, Cobalt, and Carbon Dioxide in the Marine Diatom Thalassiosira weissflogii
Authors: Lane Todd W. , Morel François M.M. 
Published: July 2002

Abstract
TWCA1 is the major Zn-requiring isoform of carbonic anhydrase (CA) in the marine diatom Thalassiosira weissflogii. We have examined the roles that trace metals and CO2 play in the regulation of TWCA1 expression over ranges of concentrations that bracket those encountered in the marine environment. Both steady-state levels of TWCA1 and the kinetics of induction were measured by western analysis. TWCA1 levels correlated well with cellular CA activity levels. TWCA1 was induced at a low CO2 concentration but the level of induction, as determined by western analysis, was dependent on the availability of Zn. Co effectively substituted for Zn in regulating TWCA1 expression and promoting TWCA1 activity. Upon shift from low to high CO2, the concentration of TWCA1 decreased. The expression of TWCA1 is diel cycle regulated, and cellular TWCA1 decreased during the dark phase. These results provide the basis for studying the expression of CA in field populations and, taken together with previous radiolabeling studies, provide strong evidence of in vivo metal substitution of Co for Zn in a CA. Our data also support the conclusion that TWCA1 plays a central role in carbon acquisition inT. weissflogii.
Ionic and Osmotic Effects of NaCl-Induced Inactivation of Photosystems I and II in Synechococcus sp.
Authors: Allakhverdiev Suleyman I. , Sakamoto Atsushi , Nishiyama Yoshitaka , Inaba Masami , Murata Norio 
Published: July 2002

Abstract
We report here that osmotic effects and ionic effects are both involved in the NaCl-induced inactivation of the photosynthetic machinery in the cyanobacteriumSynechococcus sp. PCC 7942. Incubation of the cyanobacterial cells in 0.5 m NaCl induced a rapid and reversible decline and subsequent slow and irreversible loss of the oxygen-evolving activity of photosystem (PS) II and the electron transport activity of PSI. An Na+-channel blocker protected both PSII and PSI against the slow, but not the rapid, inactivation. The rapid decline resembled the effect of 1.0 m sorbitol. The presence of both an Na+-channel blocker and a water-channel blocker protected PSI and PSII against the short- and long-term effects of NaCl. Salt stress also decreased cytoplasmic volume and this effect was enhanced by the Na+-channel blocker. Our observations suggested that NaCl had both osmotic and ionic effects. The osmotic effect decreased the amount of water in the cytosol, rapidly increasing the intracellular concentration of salts. The ionic effect was caused by an influx of Na+ ions through potassium/Na+ channels that also increased concentrations of salts in the cytosol and irreversibly inactivated PSI and PSII.
The Calcium Rhythms of Different Cell Types Oscillate with Different Circadian Phases
Authors: Wood Nicola T. , Haley Ann , Viry-Moussaı̈d Martine , Johnson Carl H. , van der Luit Arnold H. , Trewavas Anthony J. 
Published: July 2002

Abstract
Transgenic tobacco (Nicotiana plumbaginifolia) seedlings containing the Ca2+-sensitive luminescent protein aequorin have been shown to exhibit circadian variations in cytosolic calcium. Concomitant measurements of cytosolic and nuclear calcium show that circadian variations in the cytoplasm are not expressed in the nucleus. To investigate whether all cells of transgenic seedlings contribute equally to circadian variations in cytosolic calcium, different promoters eliciting different expression patterns have been placed upstream of aequorin and used for transformation. The circadian peak occurred at different times in the three transgenic lines constructed. Luminescence imaging of these transgenic lines indicated that aequorin was differentially accumulated among the main tissues and cells of the seedlings and overcoat technology with applied epidermal strips indicated that the surface cell layers contribute the vast majority of luminescent light. We conclude that the Ca2+rhythmicities of cells and tissues oscillate with distinct differences in phase, that this might represent different underlying cellular control mechanisms and that these observations have significant implications for our understanding and study of Ca2+mediated signal transduction in plant cells.
Proteins with β‐(thienopyrrolyl)alanines as alternative chromophores and pharmaceutically active amino acids
Authors: Budisa Nediljko , Alefelder Stefan , Bae Jae Hyun , Golbik Ralph , Minks Caroline , Huber Robert , Moroder Luis 
Published: July 2002

AbstractL‐β‐(Thieno[3,2‐b]pyrrolyl)alanine and L‐β‐(thieno[2,3‐b]pyrrolyl)alanine are mutually isosteric and pharmaceutically active amino acids that mimic tryptophan with the benzene ring in the indole moiety replaced by thiophene. Sulfur as a heteroatom causes physicochemical changes in these tryptophan surrogates that bring about completely new properties not found in the indole moiety. These synthetic amino acids were incorporated into recombinant proteins in response to the Trp UGG codons by fermentation in a Trp‐auxotrophic Escherichia coli host strain using the selective pressure incorporation method. Related protein mutants expectedly retain the secondary structure of the native proteins but show significantly changed optical and thermodynamic properties. In this way, new spectral windows, fluorescence, polarity, thermodynamics, or pharmacological properties are inserted into proteins. Such an engineering approach by translational integration of synthetic amino acids with a priori defined properties, as shown in this study, proved to be a novel and useful tool for protein rational design.
Multicomponent and High-Pressure Effects on Droplet Vaporization
Authors: Aggarwal S. K. , Mongia H. C. 
Published: July 2002

Abstract
This paper deals with the multicomponent nature of gas turbine fuels under high-pressure conditions. The study is motivated by the consideration that the droplet submodels that are currently employed in spray codes for predicting gas turbine combustor flows do not adequately incorporate the multicomponent fuel and high-pressure effects. The quasi-steady multicomponent droplet model has been employed to investigate conditions under which the vaporization behavior of a multicomponent fuel droplet can be represented by a surrogate pure fuel droplet. The physical system considered is that of a multicomponent fuel droplet undergoing quasi-steady vaporization in an environment characterized by its temperature, pressure, and composition. Using different vaporization models, such as infinite-diffusion and diffusion-limit models, the predicted vaporization history and other relevant properties of a bicomponent droplet are compared with those of a surrogate single-component fuel droplet over a range of parameters relevant to gas turbine combustors. Results indicate that for moderate and high-power operation, a suitably selected single-component (50 percent boiling point) fuel can be used to represent the vaporization behavior of a bicomponent fuel, provided one employs the diffusion-limit or effective-diffusivity model. Simulation of the bicomponent fuel by a surrogate fuel becomes increasingly better at higher pressures. In fact, the droplet vaporization behavior at higher pressures is observed to be more sensitive to droplet heating models rather than to liquid fuel composition. This can be attributed to increase in the droplet heatup time and reduction in the volatility differential between the constituent fuels at higher pressures. For ignition, lean blowout and idle operations, characterized by low pressure and temperature ambient, the multicomponent fuel evaporation cannot be simulated by a single-component fuel. The validity of a quasi-steady high-pressure droplet vaporization model has also been examined. The model includes the nonideal gas behavior, liquid-phase solubility of gases, and variable thermo-transport properties including their dependence on pressure. Predictions of the high-pressure droplet model show good agreement with the available experimental data over a wide range of pressures, implying that quasi-steady vaporization model can be used at pressures up to the fuel critical pressure.
Challenges in Deep Water Experiments: Hybrid Approach
Authors: Stansberg Carl Trygve , Ormberg Harald , Oritsland Ola 
Published: July 2002

Abstract
An overview of challenges within hydrodynamic verification of deep-water offshore structures is given first. The role of model testing in the verification, as well as a range of relevant measured responses, are discussed. Various solutions for experimental verification of deep-water structures are considered. In particular, the combination of model tests with truncated set-up and computer simulations—the hybrid approach—is discussed. Two basic groups of hybrid methods are identified: Active (on-line) and passive (off-line). Most published works are on passive systems, of which a particular method is described. Case study examples with this procedure are reviewed and discussed, and future challenges are commented.
All-Polymer Optoelectronic Devices
Authors: Ho Peter K. H. , Stephen D. , Thomas  , Friend Richard H. , Tessler Nir 
Published: July 2002

Composites of nanoparticles and conjugated polymers that exhibit composition-tunable optical constants have been developed for use in semiconducting photonic structures. For example, the 550-nanometer wavelength in-plane refractive index of poly(p-phenylenevinylene)–silica composites can be tailored over the range of 1.6 to 2.7, allowing efficient distributed Bragg reflectors and waveguides to be fabricated. Low levels of chemical doping improve electrical conductivity through these structures without detriment to their photonic properties. Exemplifying these concepts, all-polymer microcavities and microcavity light-emitting diodes were demonstrated. Appropriate confinement of photons and electron-hole pairs in these organic semiconductor-based structures can be achieved.
Safety and Pharmacokinetics of Once-Daily Regimens of Soft-Gel Capsule Saquinavir plus Minidose Ritonavir in Human Immunodeficiency Virus-Negative Adults
Authors: Kilby J. Michael , Sfakianos Greg , Gizzi Nick , Siemon-Hryczyk Peggy , Ehrensing Eric , Oo Charles , Buss Neil , Saag Michael S. 
Published: July 2002

ABSTRACT
Human immunodeficiency virus type 1 (HIV-1) protease inhibitors have dramatically improved treatment options for HIV infection, but frequent dosing may impact adherence to highly active antiretroviral treatment regimens (HAART). Previous studies demonstrated that combined therapy with ritonavir and saquinavir allows a decrease in frequency of saquinavir dosing to twice daily. In this study, we evaluated the safety and pharmacokinetics of combining once-daily doses of the soft-gel capsule (SGC) formulation of saquinavir (saquinavir-SGC) and minidose ritonavir. Forty-four healthy HIV-negative volunteers were randomized into groups receiving once-daily doses of saquinavir-SGC (1,200 to 1,800 mg) plus ritonavir (100 to 200 mg) or a control group receiving only saquinavir-SGC (1,200 mg) three times daily. Saquinavir-SGC alone and saquinavir-SGC–ritonavir combinations were generally well tolerated, and there were no safety concerns. Addition of ritonavir (100 mg) to saquinavir-SGC (1,200 to 1,800 mg/day) increased the area under the concentration-time curve (AUC) for saquinavir severalfold, and the intersubject peak concentration in plasma and AUC variability were reduced compared to those achieved with saquinavir-SGC alone (3,600 mg/day), while trough saquinavir levels (24 h post-dose) were substantially higher than the 90% inhibitory concentration calculated from HIV-1 clinical isolates. Neither increasing the saquinavir-SGC dose to higher than 1,600 mg nor increasing ritonavir from 100 to 200 mg appeared to further enhance the AUC. These results suggest that an all once-daily HAART regimen, utilizing saquinavir-SGC plus a more tolerable low dose of ritonavir, may be feasible. Studies of once-daily saquinavir-SGC (1,600 mg) in combination with ritonavir (100 mg) in HIV-infected patients are underway.
Differential Removal of Thymidine Nucleotide Analogues from Blocked DNA Chains by Human Immunodeficiency Virus Reverse Transcriptase in the Presence of Physiological Concentrations of 2′-Deoxynucleoside Triphosphates
Authors: Meyer Peter R. , Matsuura Suzanne E. , Schinazi Raymond F. , So Antero G. , Scott Walter A. 
Published: July 2002

ABSTRACTRemoval of 2′,3′-didehydro-3′-deoxythymidine-5′-monophosphate (d4TMP) from a blocked DNA chain can occur through transfer of the chain-terminating residue to a nucleotide acceptor by human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). ATP-dependent removal of either d4TMP or 3′-azido-3′-deoxythymidine-5′-monophosphate (AZTMP) is increased in AZT resistant HIV-1 RT (containing D67N/K70R/T215F/K219Q mutations). Removal of d4TMP is strongly inhibited by the next complementary deoxynucleoside triphosphate (50% inhibitory concentration [IC50] of ∼0.5 μM), whereas removal of AZTMP is much less sensitive to this inhibition (IC50of >100 μM). This could explain the lack of cross-resistance by AZT-resistant HIV-1 to d4T in phenotypic drug susceptibility assays.
Effect of a Bis-Benzyl Polyamine Analogue on
Pneumocystis carinii
Authors: Merali Salim , Sarić Muhamed , Chin Kevin , Clarkson Allen B. 
Published: July 2002

ABSTRACT

Pneumocystis carinii
is the causative agent of
P. carinii
pneumonia (PCP), an opportunistic infection associated with AIDS and other immunosuppressed conditions. Although polyamine metabolism of this fungus has been shown to be a chemotherapeutic target, this metabolism has not been thoroughly investigated. Reported here is the effect of one polyamine analogue,
N
,
N
′-bis{3-[(phenylmethyl)amino]propyl}-1,7-diaminoheptane (BBS), on
P. carinii
. BBS inhibits the growth of
P. carinii
in culture, but at concentrations higher than those required to inhibit the growth of other pathogens. However, BBS is at least as active in an animal model of PCP as in other models of diseases studied. BBS causes some reduction in
P. carinii
polyamine content and polyamine biosynthetic enzyme activities, but the effect is less than that observed with other pathogens and very much less than the effect of the polyamine biosynthesis inhibitor
dl
-α-difluoromethylornithine. BBS enters
P. carinii
cells via a polyamine transporter, unlike all other cells that have been studied.
P. carinii
cells do not remove the benzyl groups of BBS, as is reported for mammalian cells. The most likely mode of action is displacement of natural polyamines. Overall, the activity of BBS provides further evidence that polyamines and polyamine metabolism are rational targets for the development of drugs to treat PCP. Because the details of BBS-
P. carinii
interaction differ from those of other cells studied, polyamine analogues may provide a highly specific treatment for PCP.
Single-Dose Pharmacokinetics of Amprenavir, a Human Immunodeficiency Virus Type 1 Protease Inhibitor, in Subjects with Normal or Impaired Hepatic Function
Authors: Veronese Laurence , Rautaureau Jacques , Sadler Brian M. , Gillotin Catherine , Petite Jean-Pierre , Pillegand Bernard , Delvaux Michel , Masliah Claude , Fosse Sandrine , Lou Yu , Stein Daniel S. 
Published: July 2002

ABSTRACT

Amprenavir (141W94) is extensively metabolized by P450 cytochromes, specifically, CYP3A4. Because hepatic insufficiency reduces P450-mediated metabolism, the concentrations in plasma of drugs metabolized through this pathway are often increased in subjects with liver disease. Following administration of a single, oral dose of 600 mg of amprenavir, pharmacokinetic parameters were determined for 10 subjects with severe cirrhosis, 10 subjects with moderate cirrhosis, and 10 healthy volunteers. Model-independent methods for determining the area under the plasma concentration-time curve (AUC) from time zero to infinity (AUC
0–∞
) showed an increase in amprenavir AUC
0–∞
of 2.5-fold in the group with moderate cirrhosis and 4.5-fold in the group with severe cirrhosis compared with that in the control group of healthy volunteers (
P
< 0.05). AUC
0–∞
was linearly related to the severity of liver disease, as assessed by the Child-Pugh score. Of the laboratory data used to calculate the Child-Pugh score, only the mean total bilirubin concentration showed a significant relationship with AUC
0–∞
. The relationship between the total bilirubin concentration and the AUC
0–∞
of amprenavir was well characterized by a simple
E
max
model, suggesting that the total bilirubin concentration may be a useful parameter for predicting the amprenavir AUC in subjects with hepatic insufficiency. Finally, the sera of cirrhotic subjects showed significant decreases in the levels of α
1
-acid glycoprotein, the primary plasma binding protein for amprenavir. On the basis of the results of this study, for an exposure equivalent to a clinical dose of 1,200 mg twice daily in subjects without cirrhosis, subjects with Child-Pugh scores of 5 to 8 should receive a twice-daily 450-mg dose of amprenavir, and subjects with Child-Pugh scores of 9 to 15 should receive a twice-daily 300-mg dose of amprenavir.
Pharmacokinetic Interaction between Amprenavir and Clarithromycin in Healthy Male Volunteers
Authors: Brophy Donald F. , Israel Debra S. , Pastor Antonio , Gillotin Catherine , Chittick Greg E. , Symonds William T. , Lou Yu , Sadler Brian M. , Polk Ron E. 
Published: July 2002

ABSTRACT

The P450 enzyme, CYP3A4, extensively metabolizes both amprenavir and clarithromycin. To determine if an interaction exists when these two drugs are coadministered, the pharmacokinetics of amprenavir and clarithromycin were investigated in healthy adult male volunteers. This was a Phase I, open-label, randomized, balanced, multiple-dose, three-period crossover study. Fourteen subjects received the following three regimens: amprenavir, 1,200 mg twice daily over 4 days (seven doses); clarithromycin, 500 mg twice daily over 4 days (seven doses); and the combination of the above regimens over 4 days (seven doses of each drug). Twelve subjects completed all treatments and the follow-up period. The erythromycin breath test (ERMBT) was administered at baseline, 2 h after the final dose of each of the three regimens and at the first follow-up visit. Coadministration of clarithromycin and amprenavir significantly increased the mean amprenavir AUC
ss
,
C
max,ss
, and
C
min,ss
by 18, 15, and 39%, respectively. Amprenavir had no significant effect on the AUC
ss
of clarithromycin, but the median
T
max,ss
for clarithromycin increased by 2.0 h, renal clearance increased by 34%, and the AUC
ss
for 14-(
R
)-hydroxyclarithromycin decreased by 35% when it was given with amprenavir. Amprenavir and clarithromycin reduced the ERMBT result by 85 and 67%, respectively, and by 87% when the two drugs were coadministered. The baseline ERMBT value did not correlate with clearance of amprenavir or clarithromycin. A pharmacokinetic interaction occurs when amprenavir and clarithromycin are coadministered, but the effects are not likely to be clinically important, and coadministration does not require a dosage adjustment for either drug.
Genome-Wide Expression Patterns in
Saccharomyces cerevisiae
: Comparison of Drug Treatments and Genetic Alterations Affecting Biosynthesis of Ergosterol
Authors: Bammert Gary F. , Fostel Jennifer M. 
Published: July 2002

ABSTRACT

Enzymes in the ergosterol-biosynthetic pathway are the targets of a number of antifungal agents including azoles, allylamines, and morpholines. In order to understand the response of
Saccharomyces cerevisiae
to perturbations in the ergosterol pathway, genome-wide transcript profiles following exposure to a number of antifungal agents targeting ergosterol biosynthesis (clotrimazole, fluconazole, itraconazole, ketoconazole, voriconazole, terbinafine, and amorolfine) were obtained. These profiles were compared to the transcript profiles of strains containing deletions of one of the late-stage ergosterol genes:
ERG2
,
ERG5
, or
ERG6
. A total of 234 genes were identified as responsive, including the majority of genes from the ergosterol pathway. Expression of several responsive genes, including
ERG25
,
YER067W
, and
YNL300W
, was also monitored by PCR over time following exposure to ketoconazole. The kinetics of transcriptional response support the conditions selected for the microarray experiment. In addition to ergosterol-biosynthetic genes, 36 mitochondrial genes and a number of other genes with roles related to ergosterol function were responsive, as were a number of genes responsive to oxidative stress. Transcriptional changes related to heme biosynthesis were observed in cells treated with chemical agents, suggesting an additional effect of exposure to these compounds. The expression profile in response to a novel imidazole, PNU-144248E, was also determined. The concordance of responsive genes suggests that this compound has the same mode of action as other azoles. Thus, genome-wide transcript profiles can be used to predict the mode of action of a chemical agent as well as to characterize expression changes in response to perturbation of a metabolic pathway.