Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The molecular area, collapse pressure, and surface potential of gangliosides obtained by different methods were systematically compared in monolayers at the air-water interface. Different values of these parameters are obtained depending on the purification procedure employed for the isolation of pure gangliosides. This is due to impurities (such as peptidaceous material) that remain in different amounts in the various preparations and that modify the ganglioside surface behavior. Routine purity checking by HPTLC analysis of gangliosides usually fails to reveal these impurities. On the other hand, even if the monolayer technique cannot identify the nature or amount of contaminants, it is extremely sensitive to reveal alterations of the surface molecular parameters caused by relatively small amounts of other components coextracted with the ganglioside or adventitiously introduced with the solvents or subphases employed. This is a serious problem for the obtention of correct and reproducible values of such important parameters as the molecular area of gangliosides, their electrostatic potential in oriented interfaces, and their interactions with other lipids and proteins. A procedure leading to consistent molecular parameters that remain reproducible after several repurification cycles is to perform an alkaline treatment on previously purified gangliosides species with NaOH, this is followed by dialysis against bidistilled water, rechromatography on DEAE-Sephadex A25, silicic acid or Iatrobeads, and Sephadex LH-20 columns; repurified gangliosides are stored in chloroform-methanol-0.01 M NaOH (60:30:4.5).
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PMID:Molecular parameters of gangliosides in monolayers: comparative evaluation of suitable purification procedures. 193 17

Euthanasia of chickens, young and mature rats, and mice was assessed using chloroform, carbon dioxide and ether. Behavioural patterns were recorded to give some indication of the stress involved. Carbon dioxide induced collapse faster (11.2 +/- 0.4 s) than chloroform (18.9 +/- 0.4 s) or ether (greater than 60 s). With regard to the time taken to death, in carbon dioxide mice had the shortest time (48 +/- 10 s) and mature rats had the longest time (135 +/- 10 s). In chloroform, the only difference was the delayed onset of death (127 +/- 10 s) in the chicken. Behavioural patterns were similar for the chicken in carbon dioxide and chloroform, except for wing flapping, even when unconscious, in carbon dioxide. Chloroform is recommended as more aesthetically acceptable for euthanasia of chickens. Carbon dioxide is recommended for the euthanasia of both rats and mice, considering behavioural criteria. Ether is unsuitable as a euthanasia method as it is dangerous, slow acting and an irritant.
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PMID:The behaviour of chickens, mice and rats during euthanasia with chloroform, carbon dioxide and ether. 312 35

Incubation of 2'-chloro-2'-deoxy[3'-3H]uridine 5'-diphosphate ([3'-3H]ClUDP) with Escherichia coli ribonucleotide reductase (RDPR) and use of thioredoxin-thioredoxin reductase as reductants result in release of 4.7 equiv of 3H2O/equiv of B1 protomer, concomitant with enzyme inactivation. Inactivation is accompanied by the production of 6 equiv of inorganic pyrophosphate [Stubbe, J. A., & Kozarich, J.W. (1980) J. Am. Chem. Soc. 102, 2505-2507] and by the release of uracil as previously shown [Thelander, L., Larsson, A., Hobbs, J., & Eckstein, F. (1976) J. Biol. Chem. 251, 1398-1405]. Reisolation of RDPR by Sephadex chromatography and analysis by scintillation counting indicate that 0.96 equiv of 3H is bound per protomer of the B1 subunit of the inactivated enzyme. Incubation of [5'-3H]ClUDP with RDPR followed by similar analysis indicates that 4.6 mol of 3H is bound per protomer of the B1 subunit of the inactivated enzyme. No 3H2O is released, and 6 equiv of inorganic pyrophosphate is produced during the inactivation. RDPR is protected against inactivation when dithiothreitol (DTT) is used as a reductant in place of thioredoxin-thioredoxin reductase. Incubation of [5'-3H]ClUDP with RDPR and DTT results in the isolation of CHCl3-extractable material that exhibits infrared absorptions at 1710 and 1762 cm-1. The infrared spectrum and the NMR spectrum of the CHCl3-extracted material are very similar to model compounds prepared by the interaction of 2-methylene-3(2H)-furanone with ethanethiol. Incubation of ribonucleoside-triphosphate reductase (RTPR) from Lactobacillus leichmannii with [3'-3H]ClUTP and 3 mM DTT also results in time-dependent 3H2O release concomitant with enzyme inactivation. Reisolation of the inactive protein by Sephadex chromatography followed by radiochemical analysis indicates that 0.4 equiv of 3H is bound covalently per mol of inactivated enzyme. Similar studies with [5'-3H]ClUTP indicate that 2.9 equiv of 3H is bound covalently per mol of inactivated enzyme. No 3H2O is released. High concentrations of DTT protect the enzyme against inactivation. Extraction of the enzymatic reaction mixture with CHCl3 and analysis of the isolated products result in an infrared spectrum and an NMR spectrum remarkably similar to those observed with the E. coli RDPR. Data presented are consistent with the proposal that both the E. coli and L. leichmannii enzymes are able to catalyze the breakdown of the appropriate 2'-chloro-2'-deoxynucleotide to a 3'-keto-2'-deoxynucleotide that can collapse to form the reactive sugar intermediate 2-methylene-3(2H)-furanone.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Mechanism of inactivation of Escherichia coli and Lactobacillus leichmannii ribonucleotide reductases by 2'-chloro-2'-deoxynucleotides: evidence for generation of 2-methylene-3(2H)-furanone. 639 38

The general anesthetics chloroform and halothane inhibit ATP synthesis in rat liver mitochondria, in the millimolar concentration range (1-12 mM), in parallel with a reduction of respiratory control and the ratio of ATP produced to oxygen consumed. In these effects, halothane and chloroform are similar to classical, protonophoric, uncouplers. The rate of ADP-stimulated respiration or the rate of uncoupler-stimulated respiration is not affected. Like classical uncouplers, halothane and chloroform also stimulate mitochondrial ATPase activity. However, the extent of stimulation by these agents is larger than by protonophoric uncouplers and, more significantly, ATPase activity stimulated by carbonylcyanide m-chlorophenylhydrazone is further stimulated by these agents. In the presence of the Ca2+ chelator EGTA, halothane and chloroform have no measurable effect on the magnitude of the proton electrochemical potential, delta mu H. In the absence of EGTA these anesthetics have a small effect on delta mu H, apparently due to stimulation of Ca2+ cycling. Under these conditions the membrane potential is decreased while delta pH is increased, but the total value of delta mu H is only slightly decreased. The uncoupling activity of the anesthetics is the same in the presence of absence of EGTA. Thus, in contrast to protonophoric uncouplers, the uncoupling effect of general anesthetics does not depend on the collapse of delta mu H. In the same concentration range in which anesthetics uncouple oxidative phosphorylation both halothane and chloroform increase membrane fluidity, as measured by the partitioning of the hydrophobic spin probe 5-doxyldecane. These findings suggest a role for intramembrane processes in energy conversion that is not dependent on the bulk delta mu H.
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PMID:Uncoupling of oxidative phosphorylation in rat liver mitochondria by general anesthetics. 657 86

Physicochemical analysis and Monte Carlo simulations were used to identify structural features which prevent oral absorption of HBED, a potent iron chelator. In water the dominant conformations of HBED involve the hydrophobic collapse of the two aromatic rings. These conformations are favored in polar media because they expose the polar phenolic hydroxy groups to the solvent and partially shield the nonpolar aromatic rings. In a less polar solvent such as chloroform, a symmetrical H-bond network between the carboxylates and the amines dominates the conformational space. This leads to the exposure of the phenolic hydroxy groups to the solvent, which is unfavorable for solvation. The low solubility of HBED in nonpolar solvents was confirmed experimentally by determination of the partition coefficients in octanol, chloroform, and cyclohexane and may explain the poor membrane permeability of this compound. The high conformational stability which disfavors partitioning into phospholipids is mainly due to the symmetrical H-bond network. Potentiometric titrations of a monoester of HBED in MeOH/water indicate that the protonation sequence was changed compared to that of the parent compound, suggesting that the symmetrical H-bond network was disrupted. Conformational analysis in chloroform confirmed that, in contrast to HBED, no symmetric interaction between the carboxylate and the nitrogen amines is possible in the half-ester and a variety of conformations which allow partial shielding of the polar phenolic OH groups are energetically possible. This theoretical model predicting a better solubility of the half-esters in nonpolar solvents was supported by the large increase in the partition coefficients in octanol, chloroform, and cyclohexane measured experimentally. The high absorbability predicted by physicochemical and computer simulation methods was corroborated by in vivo experiments in marmoset monkeys where the monoethyl ester derivative of HBED was well-absorbed orally while the parent compound was nearly ineffective in the same model.
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PMID:Improving the oral bioavailability of the iron chelator HBED by breaking the symmetry of the intramolecular H-bond network. 1078 Sep 2

Raman spectroscopy is used to examine the effect of mobile phase composition on the orientation of octadecyl-bonded silica-based reversed-phase liquid chromatographic (RPLC) stationary phase ligands. The effect of ligand bonding density is also investigated. The present experimental set-up utilizes a direct, noninvasive, on-column approach to examine the solvent dependent conformational behavior of the bonded ligands under flow-rate and back pressure conditions similar to those used during conventional RPLC measurements. Neat, single-component, mobile phase solvents including water, acetonitrile, methanol and chloroform are used to investigate the hypothesized collapsing and extension of stationary phase ligands with changes in mobile phase composition. No evidence of phase collapse was observed upon changing the mobile phase composition from an organic to an aqueous content. Also, Raman spectroscopic measurements allowed the differentiation between associated and free acetonitrile solvent.
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PMID:Characterization of C18-bonded liquid chromatographic stationary phases by Raman spectroscopy: the effect of mobile phase composition. 1084 87

Fractionation and reconstitution techniques were used to study the contribution of endogenous flour lipids to the quality of semisweet (Rich Tea-type) biscuits. Biscuit flour was defatted with chloroform and baked with bakery fat but without endogenous lipid addition. Semisweet biscuits baked from defatted flour were flatter, denser, and harder and showed collapse of gas cells during baking when compared with control biscuits. Defatted flour semisweet doughs exhibited a different rheological behavior from the control samples showing higher storage and loss moduli (G' and G' ' values), that is, high viscoelasticity. Functionality was restored when total nonstarch flour lipids were added back to defatted flour. Both the polar and nonpolar lipid fractions had positive effects in restoring flour quality, but the polar lipid fraction was of greatest benefit. Both fractions were needed for complete restoration of both biscuit quality and dough rheological characteristics.
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PMID:Effects of endogenous flour lipids on the quality of semisweet biscuits. 1256 72

EXPERIMENTS DESIGNED TO CHARACTERIZE AN UNIDENTIFIED TRANSMISSIBLE AGENT BROUGHT FORTH THE FOLLOWING FINDINGS: The cytopathology consisted of the formation of intranuclear globules, collapse of the involved nuclei, and the extrusion of nuclear materials. The relatively dormant primary human amnion cells were less susceptible than the rapidly growing cell lines. Similarly, the slowly multiplying ribose variants were less susceptible than their corresponding parent cell lines. Interferon-like activity was released from infected cells. Infectivity was readily demonstrated following storage at 0-4 degrees C for at least 8 months or at 37 degrees C for at least 2 weeks. Freeze-thawing, however, markedly reduced or completely destroyed its infectivity. Infectivity was destroyed completely by ether and chloroform; partially by desoxycholate, and not affected by trypsin, papain, RNAse, DNAse, hyaluronidase, lysozyme, lecithinase, or pancreatic lipase. The rate of inactivation by 0.025 per cent formalin was much slower than that of vaccinia and herpes viruses. Its synthesis was suppressed by 5-fluorodeoxyuridine. This suppression was not reversed by thymidine and/or uracil. Heat-stable neutralizing antibody could not be demonstrated in 379 human and animal serums, in human gamma globulins, or in serums from animals "immunized" with this agent. Heat-labile inhibitors (lipoprotein-like) capable of inhibiting the infectivity of this agent were demonstrated in 154 of the 157 serums tested. Experimental evidence indicated the non-identity of this ubiquitous inhibitor and the properdin system. The non-infectious complex between this agent and the ubiquitous serum inhibitor may be dissociated (hence, become infectious) by simple dilution. Repeated attempts to reisolate a similar agent have not been successful. We have hypothesized that this agent is a virus consisting of DNA wrapped in a surface coat rich in lipid, and suggest that this virus be referred to tentatively as a lipovirus.
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PMID:The biological, immunological, and physicochemical characterization of a transmissible agent capable of inducing DNA and thymine degradation in cultured human cells. 1387 2

The effects of small neutral molecules on the liquid-crystalline ordering of dimyristoyl-phosphatidylcholine (DMPC)/dihexanoyl-phosphatidylcholine (DHPC) bicelles (q = 3.0 and 3.5) were studied via 2H, 31P, and 13C variable-temperature NMR. The addition of chloroform (up to approximately 90 mM, with a lipid concentration of approximately 120 mM) was observed to reduce the temperature onset of bicelle ordering by up to approximately 10 degrees C, likely resulting from the depression of the DMPC phase transition temperature. The temperature for the collapse of the bicelle phase was also significantly reduced; the observed effects amount to a downward shift in temperature (and reduction in range) of the liquid-crystalline portion of the bicelle phase diagram with increasing dopant concentration. Other model dopants (e.g., tetrahydrofuran and benzene) yielded smaller effects. Additionally, the variable bicelle alignment permitted the characterization of the ordering of chloroform molecules within the lipid phase.
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PMID:Effects of small neutral molecules on phospholipid bicelle ordering. 1537 58

The configuration state and spectral properties of sandwiched thulium bisphthalocyanine (TmPc2) molecule in Langmuir films and Langmuir-Blodgett (LB) films were investigated by using the surface pressure-area (pi-A) isotherm and UV-Vis absorption spectra. The experimental results indicated that the sandwiched thulium bisphthalocyanine molecules form well-ordered stable monolayer films on the water/air interface, and the sandwiched thulium bisphthalocyanine molecules take the face to face orientation for the macrocycles and edge-on configuration in pure films, with the collapse pressure being 56 mN x m(-1). But the sandwiched thulium bisphthalocyanine molecules take the face-on configuration in the sandwiched thulium bisphthalocyanine films mixed with arachidic acid (AA), and the collapse pressure is more than 60 mN x m(-1). The sandwiched thulium bisphthalocyanine molecule could form well stable Langmuir films on sub-phase surface. The mixed TmPc2/arachidic acid not only could form well stable Langmuir films, but also could be transferred to solid substrate and deposited LB multilayers. In the chloroform solution and LB films of sandwiched thulium bisphthalocyanine, the UV-Vis absorption spectra have two absorption bands, namely Soret-bands and Q-bands. The electron orbit of sandwiched metal bisphthalocyanines was calculated by using absorption spectra VEH (Valence effective Hamiltonian) theory, and the electron transition orbit corresponding to the absorption peaks was analyzed. The Soret absorption band has two absorption peaks that are correlated with the electron orbital transitions of 184-187* and 178-186, and four absorption peaks of the Q absorption band are correlated with the electron orbital transitioned of 186-189*, 190* and 185-187*, 188*. In the LB films, the absorption peaks were red-shifted compared with those in the solution because of the interaction of molecules. The interaction of intra-layer molecules was stronger than that of interlayer molecules.
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PMID:[Spectrum properties of Thulium bisphthalocyanine Langmuir-Blodgett films]. 1847 37


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