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At least 811 records · Page 45Linked to original sources
PubMed1993

Protein sorting by high-performance liquid chromatography. I. Biomimetic interaction chromatography of recombinant human deoxyribonuclease I on polyionic stationary phases.

Chromatographic separations can be tailored to exploit specific interactions between a stationary phase ligand and a protein structural feature of interest. Variations in this feature then form the basis for sorting a mixture of closely related proteins into defined subpopulations. This report describes the sorting of variants of recombinant human deoxyribonuclease I (rhDNase) that differ in the occurrence of deamidation at a single residue. rhDNase, an enzyme that non-specifically hydrolyzes DNA, is glycosylated and exhibits considerable charge heterogeneity owing to the sialylation and phosphorylation of its N-linked oligosaccharides. This heterogeneity obscures the relatively subtle differences between deamidated and intact rhDNase, preventing separation on this basis in conventional ion-exchange HPLC. Published structural information on bovine DNase reveals that the analogous labile asparagine residue is involved in DNA binding, so stationary phases containing polyanionic ligands mimicking nucleic acids were employed to separate the deamidation variants of rhDNase. Electrostatically immobilized DNA, a "tentacle" cation exchanger (TCX) and immobilized heparin columns all resolved the deamidated and intact forms of rhDNase when operated at pH 4.5. The ligands of the TCX and heparin columns are sufficiently long, flexible and polyanionic to interact with rhDNase in a manner similar to DNA and to sort rhDNase variants on the basis of the charge difference of a single residue involved in that interaction. A non-hydrolyzable double-stranded oligonucleotide analogue of DNA was also synthesized and immobilized to an HPLC support. This column, operated at pH 6, where rhDNase is active, resolved the two isomeric products of deamidation of rhDNase, i.e., variants of the enzyme containing either aspartate or isoaspartate in lieu of asparagine at the deamidation site in rhDNase. This is the first reported separation of intact variants of a glycoprotein differing on the basis of these isomeric products of deamidation through the common cyclic imide mechanism.

Anions↗
PubMed1989

Effect of barbiturates on polyphosphoinositide biosynthesis and protein kinase C activity in synaptosomes.

Previously, it has been found that phenobarbital inhibited protein kinase C (PKC) and the enzymes of the metabolism of polyphosphoinositide, especially phosphatidylinositol 4-phosphate (PIP) kinase (PIP-kinase). As a continuation of these studies, a number of barbiturates (barbituric acid, barbital, butabarbital, pentobarbital, amobarbital, phenobarbital, secobarbital and hexobarbital) were tested for inhibition of these enzymes and also of phosphatidylinositol (PI) kinase (PI-kinase), in a synaptosomal preparation at pH 7.8 from the brain of rat. All compounds, except barbituric acid (and Na-barbital for PI-kinase) inhibited the three kinases. However, PKC was approximately 3-5 fold more sensitive to inhibition by the drugs (measured by Ki values) than PIP-kinase, which was 2- to 4-fold more sensitive than PI-kinase. The inhibitory potency of the drugs increased with their lipophilicity, although to a lesser degree than expected from the differences in partition coefficients; the largest deviation from a positive correlation (i.e. hexobarbital) may be the result of the blockade of an imide (-NH) group at one position of the barbituric ring. Concentrations of drugs (after correction for the greater than normal ionization (pH 7.8) of the drugs in the assays) necessary for half-maximal inhibition were well within, or smaller than, those reported necessary for in vitro blocking of nerves. The possibility, therefore, exists that the physiological effects of the barbiturates are, in part, the result of an inhibition of protein kinase C and PIP-kinase.

1-Phosphatidylinositol 4-Kinase↗
PubMed1992

Presence of autoantibodies to peptidyl-prolyl cis-trans isomerase (cyclosporin A-binding protein) in systemic lupus erythematosus.

Several autoantibodies against cytoplasmic or nuclear components of cells have been reported in autoimmune diseases. We report here a previously unrecognized autoantibody to peptidyl-prolyl cis-trans isomerase (PPIase) in patients with systemic lupus erythematosus (SLE). PPIase, which catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides, has recently been found to be identical to cyclophilin, a specific binding protein of a potent immunosuppressant, cyclosporin A. IgG and IgM anti-PPIase antibodies were detected in 40 and 20% of unselected patients with SLE, respectively, by ELISA. The reactivity of these sera was confirmed by immunoblotting experiments. Sera from rheumatoid arthritis patients showed no reactivity and 1 of 8 sera from systemic sclerosis patients and 1 of 25 sera from normal controls showed only weak reactivity. Unexpectedly, the anti-PPIase antibody was unable to inhibit PPIase activity, indicating that the autoantibody recognizes an epitope of PPIase which is different from the active site of PPIase. The levels of the anti-PPIase antibody in SLE patients correlated with remissions and flares of the disease. The anti-PPIase antibody was higher in patients with active SLE than those with inactive disease. The prevalence of the active stage of the disease was significantly higher in IgG anti-PPIase antibody-positive SLE patients as compared to antibody-negative SLE patients. These data define the presence of a new autoantibody against PPIase and its association with the activity and certain clinical manifestations in SLE.

Adult↗
PubMed1979

Metabolism of N-acetyl PGE2 carboxamide in the rat.

After intratracheal administration to rats, the bronchodilator N-acetyl PGE2 carboxamide was converted rapidly to PGE2 and 13,14-dihydro-15-keto-PGE2, the major plasma metabolite. Oxidation of the N-acetyl carboxamide by prostaglandin dehydrogenase and hydrolysis of the imide bond were demonstrated in vitro.

Animals↗
PubMed1982

Metabolism of the prostaglandin fertility regulator sulprostone in monkeys.

The prostaglandin imide analog sulprostone (I) was labeled with tritium in the phenoxy ring to trace the fate of the prostanoic acid portion of the molecule and with carbon-14 in the methanesulfonimide moiety to trace the fate of that portion of the molecule. Disposition was studied after intravenous administration to female cynomolgus monkeys. The excretion and plasma pharmacokinetics of total radioactivity indicated that the prostanoic acid and methanesulfonimide moieties were disposed of differently, implying that hydrolysis of sulprostone was extensive and that the hydrolysis products were treated independently. The urinary excretion of tritium (prostanoic acid) was consistent with that observed for other prostaglandins. The urinary excretion and plasma pharmacokinetics of carbon-14 were consistent with those expected for methanesulfonamide. Urinary metabolites identified in 0-2 hr urine included a trace amount of unchanged drug, methanesulfonamide, and two products of beta-oxidation - the tetranor and dihydrotetranor prostanoic acids.

Animals↗
PubMed1982

Hydrogen exchange kinetics of nucleic acids. Double and triple helices with Hoogsteen-type basepairs.

The kinetics of hydrogen-tritium exchange reaction have been followed by a Sephadex technique of a double-helical poly(ribo-2-methylthio-adenylic acid) . poly(ribouridylic acid) complex with the Hoogsteen-type basepair. Only one hydrogen in every 2-methylthio-adenine . uracil basepair has been found to exchange at a measurably slow rate, 0.023 s-1 (at 0 degrees C), which is, however, much greater than that for a double-helix with the Watson-Crick type A . U pair. The kinetics of hydrogen-tritium exchange were also examined by triple-helical poly(rU) . poly(rA) . poly(rU) which involves both the Watson-Crick and Hoogsteen basepairings. Here, three hydrogens in every U . A. U base triplet have been found to exchange at a relatively slow rate, 0.0116 s-1 (at 0 degrees C). The kinetics of hydrogen-deuterium exchange reactions of these polynucleotide helices have also been followed by a stopped-flow ultraviolet absorption spectrophotometry at various temperatures. On the basis of these experimental results, the mechanism of the hydrogen exchange reactions in these helical polynucleotides was discussed. In the triple helix, the rate-determining process of the slow exchange of the three (one uracil-imide and two adenine-amino) hydrogens is considered to be the opening of the Watson-Crick part of the U. A. U triplet. This opening is considered to take place only after the opening of the Hoogsteen part of the triplet.

Base Composition↗
PubMed1986

Chronic toxicity, reproductive, and teratogenic studies with oxamyl.

Oxamyl (methylN',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxam imidate; CAS 23135-22-0) was tested for oral toxicity in the rat and dog (90-day and 2-year feeding studies) and in the mouse (2-year feeding study). Teratogenic potential was evaluated in the rat and rabbit and functional reproductive capacity was studied in the rat in a one- and a three-generation reproduction study. Rats fed a diet containing oxamyl at 500 ppm showed clinical signs of cholinesterase inhibition and body weight loss within 2 days. Feeding of either 100 or 150 ppm oxamyl for 90 days produced a reduced rate of weight gain without other signs of response, and no effects were detected at 50 ppm. An oxamyl feeding period of 2 years also showed depressed body weight gains in rats fed either 100 or 150 ppm. Cholinesterase activity was depressed only during the first week of feeding and only in the 150-ppm group. All other indices of response, including the type and distribution of tumors, were similar in the test and control rats and it was concluded that the no-observed-effect level was 50 ppm (equivalent to approximately 5 mg/kg). Mice fed oxamyl at 100 ppm for 6 weeks showed signs of cholinesterase inhibition and some mortalities, so the dietary concentration was reduced to 75 ppm in the 2-year study. Body weights of mice fed oxamyl at 50 or 75 ppm were lower than controls during the first 6 months of the study. No other signs of a toxic response to oxamyl were seen in mice and a no-observed-effect level of 25 ppm (approximately 2.5 mg/kg) was assigned to this compound. No evidence of a tumorigenic response was obtained. Dogs fed oxamyl at 150 ppm for 2 years showed marginal increases in serum alkaline phosphatase activity and cholesterol concentration but no tissue pathology was seen. No evidence of cholinesterase inhibition was seen. It was concluded that the no-observed-effect level for oxamyl in the dog was 100 ppm (approximately 2.5 mg/kg). In the one- and three-generation reproduction studies, litter sizes were somewhat lower in rats fed oxamyl at 100 or 150 ppm oxamyl with normal values seen at 50 ppm. Weanling body weights were normal in rats in the 50-ppm group for three generations but were reduced in the one-generation study. Pup body weights were lower in rats in both the 100- or 150-ppm groups.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Deamidation of asparagine and glutamine residues in proteins and peptides: structural determinants and analytical methodology.

Non-enzymatic deamidation of asparagine and glutamine residues in proteins and peptides are reviewed by first outlining the well-described reaction mechanism involving cyclic imide intermediates, followed by a discussion of structural features which influence the reaction rate. The second and major part describes analytical techniques that allow studying deamidation in proteins using recombinant human growth hormone and recombinant hirudin as examples. Finally, the significance of non-enzymatic deamidation with respect to the production of pharmaceutical proteins is discussed.

Amino Acid Sequence↗
PubMed1994

A sensitive enzyme immunoassay for angiotensin II in serum.

A sensitive and specific enzyme immunoassay for measuring angiotensin II (AII) has been developed as a convenient alternative to a radioimmunoassay. An antiserum to AII was prepared using AII conjugated by carbodi-imide to rabbit serum albumin, and coated on to microwell plates. The labelled antigen was prepared from AII and horseradish peroxidase using the periodate method. This enzyme immunoassay was a simple two-step procedure: 0.1 ml of AII-extracted plasma was incubated for 1 h at 37 degrees C; and 1 ml of labeled AII was incubated for 1 h at 37 degrees C. Bound horseradish peroxidase activity was then determined using o-phenylenediamine as chromogen by measuring the absorbance at 492 nm. The lower detection limit of the assay was 3.5 pmol l-1. Between- and within-assay RSD values were 8.8-18.3% and 6.9-17%, respectively, for concentrations of 10-40 pmol l-1. The accuracy of the assay, determined by recovery and linearity experiments, was 89-106% for recovery and 91-126% for parallelism. The results obtained by the present ELISA method were well correlated with those obtained by an established radioimmunoassay (n = 10, r = 0.96, intercept = 0.9 and slope = 1.02). This assay is easy to perform, rapid and does not require radioisotopes; thus it could be widely applied in clinical laboratories.

Angiotensin II↗
PubMed1995

A stereocontrolled synthetic approach to glycopeptides corresponding to the carbohydrate-protein linkage region of cell-surface proteoglycans.

The glycopeptides 1 (Gly[O-beta-D-Xylp)-L-Ser-Gly-L-Glu) and 2 (Gly[O-[beta-D-GlcpA-(1-->3)-beta-D-Galp-(1-->3)-beta-D-Galp]-(1-- >4) -beta-D-Xylp)-L-Ser-Gly-L-Glu), carrying the core structure of serine-linked cell-surface proteoglycans were synthesized in a stereocontrolled manner. The carbohydrate key imidate xylosyl donors 3 and glycotetraosyl donors 4 and 5, as well as a tetrapeptide glycosyl acceptor 6, were coupled in the crucial glycosylation step. In these reactions, the application of either trimethylsilyl trifluoromethanesulfonate (TMSOTf) or borontrifluoride etherate (BF3-Et2O) as catalysts proved to be highly efficient. The serine linked glycopeptides 34, 36 and 37 thus obtained yielded target compounds 1 and 2 on complete deprotection.

Amino Acid Sequence↗
PubMed1996

Solution conformations of KNI-272, a tripeptide HIV protease inhibitor designed on the basis of substrate transition state: determined by NMR spectroscopy and simulated annealing calculations.

KNI-272, a highly selective and potent HIV protease inhibitor containing allophenylnorstatine [(2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], named Apns, has been studied in dimethylsulfoxide-d6 by NMR spectroscopy and simulated annealing calculations. 1H and 13C spectra showed the presence of two conformers characterized by the configuration of the imide bond between the Apns and Thz residues, i.e., trans and cis forms, respectively. Rotating frame Overhauser effect spectra revealed that the trans conformer is dominant. The solution structure calculated from the distance information resulting from nuclear Overhauser effects experiments is similar overall to those observed in the solid states, either as a single crystal or as complex with the protease. The results from both molecular dynamics simulations and experimental 13C longitudinal relaxation times indicate that the backbone of KNI-272 has a fairly rigid conformation.

Crystallography, X-Ray↗
PubMed1995

Photosensitization with derivatives of chlorin p6.

Biophysical and photobiological properties of three derivatives of chlorin p6 were examined. These agents can be considered as lysyl analogs of the aspartyl chlorin NPe6. Lysyl chlorin p6 diester (LCP) and the triester analog (LCP2) were readily accumulated by murine leukemia L1210 cells, localized in lysosomes, and were relatively inefficient photosensitizing agents in vitro. In contrast, lysyl chlorin e6 imide (LCI) was poorly accumulated, concentrated in mitochondrial and plasma membranes, but was more efficacious. LCI was the most effective agent with regard to photosensitization of a murine tumor in vivo, but all three agents caused substantially more toxicity than was observed with NPe6.

Animals↗
PubMed1996

Engineering of doubly antigenized immunoglobulins expressing T and B viral epitopes.

BACKGROUND: Concomitant with the advent of molecular biology techniques and the ability of immunoglobulins (Ig) to recognize proteins, carbohydrates, lipopeptides and nucleic acids, vaccinologists have taken advantage to develop a variety of prophylactic and therapeutic vaccine prototypes. Presentation of epitopes to the immune system by Ig molecules as a carrier platform offers several advantages: (i) long exposure of the antigen to antigen processing cells (APCs) by virtue of their long half life, (ii) lack of the immune response to self Ig, focusing the immune response to protective epitopes rather than irrelevant epitopes, (iii) it takes advantage of the properties of Fc fragment of various isotypes like crossing the placenta (IgG) or homing in epithelia (IgA), and (iv) targeting various antigens by virtue of their binding specificity. OBJECTIVES: This study was aimed to genetically and enzymatically engineer immunoglobulins (Igs) able to express and to deliver concomitantly immunodominant T and B viral epitopes. STUDY DESIGN: Using a genetic engineering approach we replaced the complementary determining region 3 (CDR3) and complementary determining region 2 (CDR2) of an anti-arsonate 91A3 mAb with the immunodominant HA110-120 T cell epitope and HA150-159 B cell epitope of hemagglutinin (HA) of influenza A/PR8 virus, respectively. The second doubly antigenized Ig (Ig-HA-Gal-B) was constructed on an Ig in which CDR3 was replaced with HA110-120 T cell epitope while the HA150-159 B cell epitope was enzymatically assembled through an imidic bond on the galactose (Gal) residues of the carbohydrate moiety. RESULTS AND CONCLUSIONS: Both genetically and genetically/enzymatically doubly antigenized Ig constructs (dAIg) were properly folded and they were able to activate peptide-specific T cells and to elicit anti-viral antibody response in mice. This demonstrates that the CDR loops as well as carbohydrate moieties of immunoglobulins represent permissive sites for grafting foreign epitopes without altering the structural integrity of immunoglobulins and the immunogenicity of the viral peptides.

Animals↗
PubMed2005

Novel biological therapies for the treatment of multiple myeloma.

The therapeutic management of multiple myeloma (MM) for the last several decades has mainly involved regimens based on use of glucocorticoids and cytotoxic chemotherapeutics. Despite progress in delineating the activity of such regimens, at either conventional or high doses, MM has remained an incurable disease, without substantial improvement in the median overall survival. This has sparked major interest in the development of novel therapies that in part capitalize on recent advances in our understanding of the biology of MM, including the molecular mechanisms by which MM cell-host bone marrow (BM) interactions regulate tumor-cell growth, survival, and drug resistance in the BM milieu. The development of in vitro and in vivo models of MM-stromal interactions has allowed not only for better characterization of these molecular phenomena but also for identification of specific therapeutic strategies to overcome these interactions and achieve an enhanced anti-MM effect, even against MM resistant to conventional therapies. Herein, we review the latest progress in the development of these novel anti-MM therapies, with major focus on therapies which have translated from preclinical evaluation to clinical application, including thalidomide and its more potent immunomodulatory (IMiD) derivatives, the first-in-class proteasome inhibitor bortezomib (formerly known as PS-341), and arsenic trioxide (As2O3).

Apoptosis Regulatory Proteins↗
PubMed2005

Preparation and characterization of RGD-immobilized chitosan scaffolds.

Chitosan scaffolds were modified with RGDS (Arg-Gly-Asp-Ser) in the present work via an imide-bond forming reaction between amino groups in chitosan and carboxyl groups in peptides. Successful immobilization was verified with FTIR spectroscopy, and the immobilized amount was determined to be on the order of 10(-12) mol/cm2 through analysis of the immobilized amino acids. Results of experiments of cell culture with rat osteosarcoma (ROS) cells demonstrated that RGDS immobilization could enhance the attachment of ROS cells onto the chitosan, resulting in higher cell density attached to the RGDS-modified scaffold than to the unmodified scaffold. It should be noted that only RGDS, but not other peptide such as RGES, is effective in enhancing cell attachment and possible proliferation. Experiments of in vitro mineralization indicated that there were more cells on the RGDS-modified scaffold than on the unmodified scaffold, which tended to form bone-like tissues. The results presented in this work suggest that immobilization of RGDS can make chitosan scaffolds more compatible for the culture of osteoblast-like cells and the regeneration of bone-like tissues.

Amino Acids↗
PubMed2004

Probing the ultra-high resolution structure of aldose reductase with molecular modelling and noncovalent mass spectrometry.

Aldose reductase, the first and rate-limiting enzyme of the polyol pathway, is a target for drug design for the treatment of diabetes complications. The structures of aldose reductase in complex with the cyclic imide inhibitors Fidarestat and Minalrestat were recently determined at ultra-high resolution (Proteins 2004, 55, 805). We have used the detailed structural information revealed at atomic resolution, including the assignment of protonation states for the inhibitors and active site residues, together with molecular modelling and noncovalent mass spectrometry to characterise the type and strength of the interactions between the enzyme and the inhibitors, and to attempt the design of novel potential inhibitors with enhanced binding energies of the complexes. The VC(50) values measured by mass spectrometry (accelerated voltage of ions needed to dissociate 50% of a noncovalent complex in the gas phase) for the aldose reductase inhibitors correlate with the IC(50) values (concentration of inhibitor giving 50% inhibition in solution) and with the electrostatic binding energies calculated between the active site residues Tyr48, His110 and Trp111 and the inhibitors, suggesting that electrostatic interactions play a major role in inhibitor binding. Our molecular modelling and design studies suggest that the replacement of the fluorine atom in Minalrestat's bromo-fluorobenzyl group with nitro, amide and carboxylate functional groups enhanced the predicted net binding energies of the complexes by 16%, 31% and 68%, respectively. When the carbamoyl group of Fidarestat was replaced with a nitro, 4-hydroxyl phenyl and carboxylate functional groups, the predicted net binding energies of the complexes were enhanced by 13%, 34% and 46%, respectively.

Aldehyde Reductase↗
PubMed2006

Synthesis and biological evaluation of new dipyrrolo[3,4-a:3,4-c]carbazole-1,3,4,6-tetraones, substituted with various saturated and unsaturated side chains via palladium catalyzed cross-coupling reactions.

The syntheses of a series of dipyrrolo[3,4-a:3,4-c]carbazole-1,3,4,6-tetraones, substituted in 10-position with saturated and unsaturated side chains, via palladium catalyzed cross-coupling reactions, are described. These compounds can be considered as granulatimide bis-imide analogues. Their inhibitory activity toward Chk1 kinase and their antiproliferative activities in vitro in four tumor cell lines are reported.

Animals↗