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At least 775 records · Page 43Linked to original sources
PubMed1982

Butyricin 7423 and the membrane H+ -ATPase of Clostridium pasteurianum.

The bacteriocin butyricin 7423 inhibited the activity of the membrane H+ -ATPase (BFoF1) of vegetative cells of Clostridium pasteurianum but not that of its soluble BF1 component. In vitro studies with the H+-ATPases of mutant strains selected for diminished sensitivity sensitivity (a) to butyricin 7423 and (b) to dicyclohexylcarbodi-imide, confirmed that butyricin 7423 interacts with the BFo component of this enzyme complex. Even so, certain other mutant strains displaying decreased sensitivity to butyricin 7423 possessed H+-ATPases which in vitro showed undiminished sensitivity to inhibition by the bacteriocin. Furthermore, from the changes in intracellular ATP concentration and in the rates and net extent of efflux of intracellular 86Rb+ ions that were provoked by exposure of the parent and several of the mutant strains to butyricin 7423, it was concluded that its primary bactericidal action was not attributable to stoichiometric inhibition of the membrane H+-ATPase. High extracellular concentrations of K+ ions enabled Cl. pasteurianum to survive exposure to low concentration of this membrane active bacteriocin.

Adenosine Triphosphatases↗
PubMed1980

Electron microscopic immunocytochemical localization of intracellular antigens in cultured cells: the EGS and ferritin bridge procedures.

A new primary fixative, ethyldimethylaminopropyl carbodi-imide-glutaraldehyde-Tris, has been combined with the use of saponin for membrane permeabilization to yield a procedure which preserves ultrastructural morphology, yet retains a cytoplasmic matrix permeable to globulin molecules. This allows pre-embedding localization of intracellular protein antigens in cultured cells by fluorescence or electron microscopy. A further combination of these methods with the 'ferritin bridge' techniqe has allowed discrete localization which is quantifiable. Together, these methods yield an overall technique which provides high quality ultrastructural morphological preservation and precise antigen localization. Examples of the localization of alpha 2-macroglobulin, actin, SV40 T-antigen, tubulin and p60src are demonstrated. Extension of these methods from cultured cells to intact tissue should be possible without major changes.

Actins↗
PubMed1988

Construction of protocellular structures under simulated primitive earth conditions.

We have developed experimental approaches for the construction of protocellular structures under simulated primitive earth conditions and studied their formation and characteristics. Three types of envelopes; protein envelopes, lipid envelopes, and lipid-protein envelopes are considered as candidates for protocellular structures. Simple protein envelopes and lipid envelopes are presumed to have originated at an early stage of chemical evolution, interaction mutually and then evolved into more complex envelopes composed of both lipids and proteins. Three kinds of protein envelopes were constructed in situ from amino acids under simulated primitive earth conditions such as a fresh water tide pool, a warm sea, and a submarine hydrothermal vent. One protein envelope was formed from a mixture of amino acid amides at 80 degrees C using multiple hydration-dehydration cycles. Marigranules, protein envelope structures, were produced from mixtures of glycine and acidic, basic and aromatic amino acids at 105 degrees C in a modified sea medium enriched with essential transition elements. Thermostable microspheres were also formed from a mixture of glycine, alanine, valine, and aspartic acid at 250 degrees C and above. The microspheres did not form at lower temperatures and consist of silicates and peptide-like polymers containing imide bonds and amino acid residues enriched in valine. Amphiphilic proteins with molecular weights of 2000 were necessary for the formation of the protein envelopes. Stable lipid envelopes were formed from different dialkyl phospholipids and fatty acids. Large, stable, lipid-protein envelopes were formed from egg lecithin and the solubilized marigranules. Polycations such as polylysine and polyhistidine, or basic proteins such as lysozyme and cytochrome c also stabilized lipid-protein envelopes.

Amino Acids↗
PubMed1994

New radiolucent head fixation made of engineering plastics for intraoperative CT scanning.

A newly developed head fixation for intraoperative computerized tomographic (IOCT) scanning is presented. The system is developed based on the head holder of multipurpose head frame and is made of two kinds of advanced engineering material; carbon fiber reinforced plastic for head holder and frames, polyamide-imide polymer for joints, screws, and head pin. Clinical tests including autoclaving and sterilization were performed and revealed all materials had sufficient strength for clinical use. This fixation system enables us to increase the efficacy of IOCT scanning during open-field neurosurgery.

Artifacts↗
PubMed1990

Sulfhydryl-reactive heavy metals increase cell membrane K+ and Ca2+ transport in renal proximal tubule.

The cellular mechanisms by which nephrotoxic heavy metals injure the proximal tubule are incompletely defined. We used extracellular electrodes to measure the early effects of heavy metals and other sulfhydryl reagents on net K+ and Ca2+ transport and respiration (QO2) of proximal tubule suspensions. Hg2+, Cu2+, and Au3+ (10(-4)M) each caused a rapid net K+ efflux and a delayed inhibition of QO2. The Hg2(+)-induced net K+ release represented passive K+ transport and was not inhibited by barium, tetraethylammonium, or furosemide. Both Hg2+ and Ag+ promoted a net Ca2+ uptake that was nearly coincident with the onset of the net K+ efflux. A delayed inhibition of ouabain-sensitive QO2 and nystatin-stimulated QO2, indicative of Na+, K(+)-ATPase inhibition, was observed after 30 sec of exposure to Hg2+. More prolonged treatment (2 min) of the tubules with Hg2+ resulted in a 40% reduction in the CCCP-uncoupled QO2, indicating delayed injury to the mitochondria. The net K+ efflux was mimicked by the sulfhydryl reagents pCMBS and N-ethylmale-imide (10(-4) M) and prevented by dithiothreitol (DTT) or reduced glutathione (GSH) (10(-4) M). In addition, both DTT and GSH immediately reversed the Ag(+)-induced net Ca2+ uptake. Thus, sulfhydryl-reactive heavy metals cause rapid, dramatic changes in the membrane ionic permeability of the proximal tubule before disrupting Na+, K(+)-ATPase activity or mitochondrial function. These alterations appear to be the result of an interaction of the metal ions with sulfhydryl groups of cell membrane proteins responsible for the modulation of cation permeability.

Animals↗
PubMed1990

Structure activity relationships of imido N-alkyl semicarbazones, thiosemicarbazones and acethydrazones as hypolipidemic agents in rodents.

A series of nitrogen substituted N-butan-3-one derivatives of cyclic imides (phthalimide, substituted phthalimide, o-benzosulfimide, 1,8-naphthalimide, 2,3-dihydrophthalazine-1,4-dione and diphenimide) and their semicarbazone, thiosemicarbazone and acethydrazone derivatives were investigated for hypolipidemic activity in rodents. These compounds were generally potent hypolipidemic agents, lowering serum cholesterol levels on an average of 37% and serum triglyceride levels on an average of 29% after 16 days dosing at 20 mg/kg day intraperitoneally (I.P.) in mice. Several analogs, most notably the semicarbazone and acethydrazone derivatives of 1-N-(1,8-naphthalimido)-butan-3-one, demonstrated improved hypocholesterolemic activity relative to their ketone precursors. Similarly, the acethydrazone derivatives generally resulted in improved hypotriglyceridemic activity in each series of 2-(3-oxobutyl)-2,3-dihydrophthalazone-1,4-dione analogs tested. The thiosemicarbazones in mice generally resulted in a loss in hypolipidemic activity. Select compounds, 1-N-3-methylphthalimido butan-3-semicarbazone (Ig) and 1-(4-methoxyphthalazine-1(2H)-one)yl butan-3(N-acetyl)hydrazone (IVg), at 10 mg/kg/day orally administered to rats demonstrated potent hypolipidemic activity after 14 days. These compounds lowered liver, small intestine mucosa and aorta wall tissue lipids, e.g. cholesterol and triglycerides, and raised fecal excretion of cholesterol moderately and of triglyceride significantly. Rat serum lipoprotein fractions after treatment for 14 days showed that the two agents lowered VLDL cholesterol and raised HDL cholesterol content.

Animals↗
PubMed1999

Peptidyl-prolyl cis-trans isomerases, a superfamily of ubiquitous folding catalysts.

Cyclosporine A therapy for prophylaxis against graft rejection revolutionized human organ transplantation. The immunosuppressant drugs cyclosporin A (CsA), FK506 and rapamycin block T-cell activation by interfering with the signal transduction pathway. The target proteins for CsA and FK506 were found to be cyclophilins and FK506-binding proteins, (FKBPs), respectively. They are unrelated in primary sequence, although both are peptidyl-prolyl cis-trans isomerases catalyzing the interconversion of peptidylprolyl imide bonds in peptide and protein substrates. However, the prolyl isomerase activity of these proteins is not essential for their immunosuppressive effects. Instead, the specific surfaces of the cyclophilin-CsA and FKBP-FK506 complexes mediate the immunosuppressive action. Moreover, the natural cellular functions of all but a few remain elusive. In some cases it could be demonstrated that prolyl isomerization is the rate-limiting step in protein folding in vitro, but many knockout mutants of single and multiple prolyl isomerases were viable with no detectable phenotype. Even though a direct requirement for in vivo protein folding could not be demonstrated, some important natural substrates of the prolyl isomerases are now known, and they demonstrate the great variety of prolyl isomerization functions in the living cell: (i) A human cyclophilin binds to the Gag polyprotein of the human immunodeficiency virus-1 (HIV-1) virion and was found to be essential for infection with HIV to occur, probably by removal of the virion coat. (ii) Together with heat shock protein (HSP) 90, a member of the chaperone family, high molecular weight cyclophilins and FKBPs bind and activate steroid receptors. This example also demonstrates that prolyl isomerases act together with other folding enzymes, for example the chaperones, and protein disulfide isomerases. (iii) An FKBP was found to act as a modulator of an intracellular calcium release channel. (iv) Along with the cyclophilins and FKBPs, a third class of prolyl isomerases exist, the parvulins. The human parvulin homologue Pin1 is a mitotic regulator essential for the G2/M transition of the eukaryotic cell cycle. These findings place proline isomerases at the intersection of protein folding, signal transduction, trafficking, assembly and cell cycle regulation.

Bacterial Proteins↗
PubMed2005

[Infliximab. Role in the treatment of psoriasis].

Psoriasis is one of the immune-mediated inflammatory diseases (IMIDs), in whose pathogenesis Th1-mediated immune responses are considered crucial. Infliximab is a chimeric monoclonal antibody directed against the Th1-cytokine TNF-alpha that has already been approved for the therapy of psoriatic arthritis (in combination with methotrexate). In clinical studies, infliximab has proved safe and effective in treating plaque-type psoriasis. In 80% of treated patients, the Psoriasis Area and Severity Index (PASI) decreased after 10 weeks by > or =75%. Infliximab is expected to be approved as second-line therapy in Germany this year for the treatment of psoriasis vulgaris.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2006

Pesticide detoxifying functions of N-halamine fabrics.

Halamine structures incorporated on polyester/cotton fabrics were able to detoxify oxime carbamate pesticides that contain thio bonds rapidly upon contact. The reaction was endothermic, and the detoxification rate was in first order to concentrations of the pesticides. Aldicarb was degraded in a much faster rate than that of methomyl by the halamine fabrics. The reactivity of halamine structures was different, and imide halamine was more reactive than amine halamine. The detoxification was an oxidative reaction on the sulfur atom existing in both aldicarb and methomyl. The same halamine structures were unable to effectively react with carbaryl and carbofuran, which are aromatic carbamates and do not contain any thio bonds.

Aldicarb↗
PubMed1999

Natural and synthetic double-stranded DNA binding studies of macrocyclic tetraamine zinc(II) complexes appended with polyaromatic groups.

The characteristic binding mode of zinc(II) complexes of macrocyclic tetraamines (1,4,7,10-tetraazacyclododecane, cyclen) appended with one or two arylmethyl group(s) [(4-quinolyl)methyl-, 1,7-bis(4-quinolyl)methyl-, (1-naphthyl)methyl-, 1,7-bis(1-naphthyl)methyl-, and (9-acridinyl)methyl-cyclen] to double-stranded calf thymus DNA and synthetic DNAs [poly(dA)-poly(dT), poly(dA-dT)2, poly(dI).poly(dC), poly(dI-dC)2, poly(dG) poly(dC), and poly(dG-dC)2] has been examined by spectrophotometric methods, Tm measurement, and inhibition of these DNA-directed transcriptions in vitro. Various hypochromic and bathochromic effects on the pendant aromatic absorption spectra of the complexes were observed in titration with the native and synthetic DNA. The binding constants Kapp (=[bound cyclen derivatives]/[unbound cyclen derivatives][DNA phosphates] M(-1)), at 25 degrees C in 10 mM EPPS (pH 8.0) containing 0.1 M Na+, were determined and compared with those of the corresponding Zn2+ -free ligands. The results showed that the Zn2+ -cyclen complexes interact with the DNA more strongly than the corresponding diprotonated ligands, leading to a stronger stacking of the pendant aromatic rings. The binding of Zn2+ -(9-acridinyl)methyl-cyclen to calf thymus DNA was competed by an AT-selective, minor groove binder, distamycin, but not by a major groove binder, methyl green. In an unusual interaction of excess Zn2+ -(9-acridinyl)methyl-cyclen with poly(dA).poly(dT), the Zn2+ -cyclen moiety went into the minor groove to make coordination bonds with the deprotonated imides of the thymines, resulting in disruption of the poly(dA).poly(dT) duplex. Thymine-containing DNA-directed transcription with Escherichia coli RNA polymerase in vitro was inhibited by the Zn2+ -(9-acridinyl)methyl-cyclen. The 50% inhibition concentrations of the transcription (IC50) were 22-45 microM with poly(dA).poly(dT) or poly(dA-dT)2 as templates, while with poly(dG-dC)2 as a template the IC50 value was 110 microM.

Amines↗
PubMed2005

6-O-sulfo sialylparagloboside and sialyl Lewis X neo-glycolipids containing lactamized neuraminic acid: synthesis and antigenic reactivity against G159 monoclonal antibody.

Synthesis and antigenic reactivity of 6-O-sulfo sialylparagloboside (SPG) and sialyl Lewis X (sLeX) neo-glycolipids containing lactamized neuraminic acid are described. The suitably protected GlcNAc-beta (1-->3)-Gal-beta (1-->4)-GlcOSE derivative was glycosylated with NeuTFAc-alpha (2-->3)-Gal imidate to give NeuTFAc-alpha (2-->3)-Galbeta (1-->4)-GlcNAc-beta (1-->3)-Gal-beta (1-->4)-GlcOSE pentasaccharide. The partial N,O-deacylation in the NeuTFAc-alpha (2-->3)-Gal part afforded N-deacetylated SPG derivative which was converted to the desired oligosaccharide containing lactamized neuraminic acid. Similar treatment of the sLeX hexasaccharide derivative, NeuTFAc-alpha (2-->3)-Gal-beta (1-->4) [Fuc-alpha (1-->3)]-GlcNAc-beta (1-->3)-Gal-beta (1-->4)-GlcOSE, gave the key hexasaccharide intermediate containing lactamized neuraminic acid. These suitably protected SPG and sLex oligosaccharides were converted stepwise into the desired neo-glycolipids (GSC-551 and GSC-552) by the coupling with 2-(tetradecyl)hexadecanol, 6-O-sulfation at C-6 of the GlcNAc residure, and complete deprotection. Both lactamized-sialyl 6-O-sulfo SPG (GSC-551) and sLex (GSC-552) neo-glycolipids were clearly recognized with G159 monoclonal antibody showing that both the lactamized neuraminic acid and the 6-O-sulfate at C-6 of GlcNAc would be involved in the G159-defined determinant. However, the Fuc residue and the lipophilic (ceramide) part may not be critical for this recognition.

Antibodies, Monoclonal↗
PubMed2006

A chemical synthesis of UDP-LacNAc and its regioisomer for finding 'oligosaccharide transferases'.

A chemical synthesis of uridine 5'-diphospho-N-acetyllactosamine (Galbeta(1-->4)GlcNAc-UDP; UDP-LacNAc) and Galbeta(1-->3)GlcNAc-UDP is described. Coupling of the disaccharide imidate derivatives with dibenzylphosphate gave the corresponding 1-phosphates, which were condensed with UMP-imidazolate to give the target UDP-oligosaccharides after purification by anion exchange HPLC and gel filtration column chromatography. Using this methodology a variety of oligosaccharide nucleotide analogues can be synthesized. These UDP-oligosaccharides may be useful for finding so-called ;oligosaccharide transferases', the glycosyltransferases which transfer the oligosaccharide moiety onto glycosyl acceptors.

Hexosyltransferases↗
PubMed1985

Methyl purple, an exceptionally sensitive monitor of chloroplast photosystem I turnover: physical properties and synthesis.

Methyl purple is a recently introduced quinone-imide redox dye that has been shown to be an exceptionally sensitive monitor of photosystem I activity in chloroplasts. This compound has a wide range of potential applications for studies of photosynthetic electron transfer and photosynthetic bioenergetics, but the physical properties of the compound must first be established rigorously. The specific molar absorption coefficients of both the anionic and protonated forms of methyl purple have been determined. The oxidation-reduction midpoint potential of methyl purple over the pH range 3 to 12 was also determined by polarographic methods, and the effect of pH on the visible absorption spectrum is reported. A detailed procedure for the synthesis of methyl purple is given.

Chemical Phenomena↗
PubMed1990

Covalent immobilization of proteins and peptides for solid-phase sequencing using prepacked capillary columns.

The use of prepacked capillary columns for immobilizing proteins and peptides for solid-phase Edman degradation is described. Capillary tubes with an internal volume of about 30 microliters are filled with glass beads bearing isothiocyanato groups (DITC-glass), aminophenyl groups (AP-glass), or aminoethylaminopropyl groups (AEAP-glass) and are sealed with porous plugs. Proteins or peptides in appropriate buffers are introduced into the columns by capillary action and are covalently coupled to the glass beads, either by reaction of lysine side-chain amino groups with DITC-glass, by carbodi-imide-mediated reaction of carboxyl groups with AP-glass, or by reaction of homoserine lactone groups with AEAP-glass. Optimization of attachment conditions is described. The capillary columns are loaded into the sequencer and, when sequencing has been completed, are discarded. This technique greatly simplifies polypeptide immobilization and is suitable for microsequencing (less than 50-1000 pmol) or macrosequencing (1-50 nmol).

Amino Acid Sequence↗
PubMed1978

Studies of fluoride-preactivated rabbit liver adenylyl cyclase.

Rabbit liver adenylyl (ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1) cyclase was stimulated by preincubation with F- and Mg2+ and the stimulation persisted despite extensive washing and/or detergent solubilization. Optimum preactivation conditions were found to be 4 mM NaF and 2 mM MgCl2; higher or lower concentrations produced submaximum stimulation regardless of preincub ation time. In addition to an enhanced catalytic acticity, the activated enzyme also exhibited different responses to Ca2+ and Cu2+ when compared to the basal enzyme. ATP caused a time-dependent inhibition that could be partially prevented or reversed by F-, but was not completely reversed by washing. This inhibition was not observed when 5'-adenosine(beta, gamma-imide) triphosphate blocks inhibition by ATP. The results support, but do not prove, the proposed molecular basis of F- activation which entails a phosphorylation-dephosphorylation mechanism.

Adenosine Triphosphate↗
PubMed1988

Structure-activity relationships of pyrimidines as dihydroorotate dehydrogenase inhibitors.

The activity of dihydroorotate dehydrogenase (DHO-dehase) has been reported to decrease both in vitro and in vivo in hepatocellular carcinomas. DHO-dehase, the fourth enzyme of the de novo pyrimidine biosynthetic pathway, is a mitochondrial enzyme which is both a potential rate-limiting reaction in the de novo pyrimidine biosynthetic pathway and a potential therapeutic target for tumor inhibitors. This paper reports results on a series of pyrimidine analogs of dihydroorotate (DHO) and orotic acid (OA) as inhibitors of DHO-dehase. The enzyme test results established that the intact amide and imide groups of the pyrimidine ring and the 6-carboxylic acid are required for significant enzyme inhibition. The testing of several functional groups similar in characteristics to that of the carboxylic acid, such as sulfonamide, tetrazole and phosphate, indicated that the carboxylic acid group is preferred by the enzyme. Using various 5-substituted OA and DHO derivatives, it was shown that there is a steric limitation of a methyl group at this position. The compound D,L-5-trans-methyl DHO (7) (Ki of 45 microM) was both an inhibitor and a weak substrate for the enzyme, demonstrating that mechanism-based enzyme inhibitors should be effective. The testing results further suggest that a negatively charged enzyme substituent may be present near the 5-position of the pyrimidine ring and that there may be an enzyme-substrate metal coordination site near the N-1 and carboxylic acid positions of the pyrimidine ring. The combined testing results were then used to define both conformational and steric substrate enzyme binding requirements from which a model was proposed for the binding of DHO and OA to the DHO-dehase active site.

Dihydroorotate Oxidase↗
PubMed1996

Inhibition of topoisomerase II by ICRF-193, the meso isomer of 2,3-bis(2,6-dioxopiperazin-4-yl)butane. Critical dependence on 2,3-butanediyl linker absolute configuration.

The bis(2,6-dioxopiperazine)s are a structurally and mechanistically unique class of topoisomerase II inhibitors that do not bind DNA and that do not stabilize topoisomerase II-DNA strand passing intermediates ("cleavable complexes"). The most effective topoisomerase II inhibitor in the bis(2,6-dioxopiperazine) series is ICRF-193 (meso or S*, R* isomer), with a meso 2,3-butanediyl linker connecting the dioxopiperazine rings. The two enantiomeric diastereomers, (R,R) and (S,S), of ICRF-193 possessing the two optically active 2,3-butanediyl linkers have been prepared from their respective optically pure 2,4-diaminobutanes via 2,3-diaminobutane-N,N,N',N'-tetraacetic acid, esterification, and imide formation. Both in vivo and in vitro assays for catalytic inhibition of topoisomerase II were employed to show that the (S,S)- and (R,R)-isomers are almost inactive as topoisomerase II inhibitors. The data indicate that the meso stereochemistry of the alkanediyl linker is crucial for activity and provides additional evidence that the cytotoxicity of the bis(2,6-dioxopiperazine)s is due to their ability to inhibit topoisomerase II.

Animals↗
PubMed1986

Stereocontrolled routes to cis-hydroxyamino sugars, Part VII: Synthesis of daunosamine and ristosamine.

The nitrogen of an allylic amine can serve as the fulcrum for stereocontrolled delivery of oxygen to an adjacent trigonal site, and cis-hydroxyamino sugars can thus be prepared. Methods for achieving the complementary procedure, namely, control of the delivery of nitrogen to an adjacent site by an allylic oxygen, are described. For example, treatment of methyl 2,3,6-trideoxy-alpha-L-erythro-hex-2-enopyranoside with trichloroacetonitrile gave an imidate ester which reacted with iodonium dicollidine perchlorate to give 2-trichloromethyl-(methyl 2,3,4,6-tetradeoxy-2-iodo-alpha-L-altropyranosido)-[3,4-d]-2-oxazo line. Exhaustive reductive dehalogenation of this product followed by hydrolysis led to methyl N-acetyl-alpha-L-ristosaminide. An analogous series of reactions was used to prepare the corresponding daunosaminide.

Hexosamines↗