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PubMed2006

Facile, alternative route to lubeluzole, its enantiomer, and the racemate.

Lubeluzole [(S)-9] has been synthesized by a convergent synthesis, alkylation of N-methyl-N-piperidin-4-yl-1,3-benzothiazol-2-amine (4) with (+)-(R)-1-chloro-3-(3,4-difluorophenoxy)propan-2-ol [(+)-(R)-8] being the key step. Alcohol (+)-(R)-8 was obtained from commercially available (R)-epichlorohydrin [(R)-6], while the thiazole derivative 4 was easily obtained starting from N-protected piperidin-4-one (1) in a three-step procedure. The same method was used in order to obtain both the (R)-stereoisomer of lubeluzole [(R)-9] and its racemate [(RS)-9]. Overall yields ranged from 20% to 35%. The enantiomeric excess values for (S)-9 and (R)-9 were 97% and 94% respectively, as analyzed by chiral HPLC.

Cardiovascular Agents↗
PubMed2006

Self-assembly of multinuclear complexes with enantiomerically pure chiral binaphthoxy imine ligands: effect of the alkyl spacer connecting two binaphthyl units on the metal binding.

Metal complexing behavior of enantiomerically pure alpha,omega-diiminoalkanes possessing the two terminal binaphthyl units (L1 and L2) was studied. The ligands L1 and L2 were prepared by the reaction of optically pure 2'-butoxy-3-formyl-2-hydroxy-1,1'-binaphthyl with propane and pentane diamines. Reactions of L1 and L2 with equimolar amount of Cu(OAc)2 afforded quantitatively multinuclear complexes 1. The structure of 1 was confirmed by MALDI-TOF MS spectroscopy, X-ray single-crystal-structure analysis, and UV/vis and CD spectroscopic analyses. The reaction of L1 having a 1,3-propanediyl spacer resulted in the formation of a self-assembled product, which was assigned as enantiopure trinuclear circular helicate 1a, while the ligand having a 1,5-pentanediyl spacer L2 gave a different self-assembled product, dinuclear side-by-side complex 1b. The circular dichroism (CD) spectrum of 1a in solution showed intense Cotton effects in both the pi-pi* transition of the naphthalene units and the LMCT region of the N,O-chelate moieties. The CD spectrum of 1b was completely different from that of 1a; in particular the Cotton effects in the LMCT region were very weak, contrary to those of 1a. These results suggest that 1a retains some chirality induced on the N,O-chelating moieties even in solution, while the induced chirality on the N,O-chelating moieties in 1b is not very significant, being consistent with the consequences of the X-ray single-crystal-structure studies.

Journal Article↗
PubMed2006

Highly diastereoselective synthesis of enantiopure naphthylaminoalcohols with analgesic properties.

The diastereoselective synthesis via Grignard reaction of enantiopure analgesic naphthylaminoalcohols has been performed. The chiral racemic key intermediate 3-dimethylamino-2-methyl-1-(naphthalen-2-yl)propan-1-one and enantiomers were prepared and transformed into the desired compounds by addition of the organometallic reagent. The chemical characterization of all diastereoisomers was accomplished by 1H NMR and HPLC analyses and the absolute configuration assigned by CD spectroscopy. The in vitro and in vivo profile has also been evaluated.

Alcohols↗
PubMed1992

Measurement of the (R)- and (S)-isomers of warfarin in patients undergoing anticoagulant therapy.

An achiral/chiral high-performance liquid chromatographic system for the analysis of total warfarin together with the (R)- and (S)-enantiomers in clinical samples has been developed. The achiral analysis is achieved using a C8 column, which is coupled to a chiral stationary phase, alpha 1-acid glycoprotein (AGP), thereby allowing for analysis of warfarin isomers without interfering serum peaks. A 0.015 M phosphate buffer mobile phase with 15% v/v propan-2-ol (pH 7.0) was used on the C8/AGP system. UV analysis at 308 nm was used for quantitation of total warfarin on the C8 column and fluorescence (excitation 300 nm, emission 390 nm) detection was employed for isomer quantitation on the AGP. Retention time of total warfarin on the C8 column was 5.95 min, while that of the (S)- and (R)-warfarin on the AGP column was 10.38 and 12.69 min, respectively. Peak resolution of the warfarin isomers was 1.64. All serum samples were subjected to solid-phase extraction. Data from two patients in a single dose study indicate that a two-compartmental model could represent the warfarin concentration-time data with enterohepatic circulation. In some patients studied during steady state therapy, concentrations of (S)-warfarin were greater than (R)-warfarin indicating that the clearance of the former is slower in these patients.

Chromatography, High Pressure Liquid↗
PubMed1995

Stereochemical aspects of the hydration of trans-anethole epoxide in the rat.

Racemic trans-anethole epoxide [1-(4'-methoxyphenyl)-propane-1,2-oxide] was incubated with water, buffers, and rat liver microsomes and cytosol and the stereochemistry of the diols produced was determined by HPLC as their dicamphanyl esters. The diol metabolites were isolated by HPLC from the urine of rats administered [1'-14C] trans-anethole and their stereochemistry determined after derivatization to their camphanyl esters. The stereochemical course of the metabolism of trans-anethole by rat liver microsomes and cytosol is discussed.

Allylbenzene Derivatives↗
PubMed2004

Infrared absorption features of gaseous isopropyl carbocations.

C3H7+ ions were formed in the cell of a Fourier transform ion cyclotron resonance mass spectrometer and assayed by their multi-photon dissociation (MPD) behavior, triggered by the absorption of tunable IR radiation from a free-electron laser source providing a high fluence. The derived experimental IRMPD spectrum, which reflects the active vibrational modes of the ion, was compared with the IR spectra calculated for the optimized structures of the most-stable species on the C3H7+ potential energy surface, namely, a chiral iC3H7+ ion of C2 symmetry and an asymmetric corner-protonated cyclopropane, cC3H7+. The significant features in the IRMPD spectra of both the unlabeled and the perdeuterated ions obtained by ionization and fragmentation of isobutane or 2-chloro[D7]propane confirm the presence of the isopropyl cation, the ground-state isomer, whose IR spectroscopic features can thus be comparatively checked in the gas phase and in condensed superacid media. Details of the IRMPD features are suggested to result from the nearly barrierless interconversion of the two C2 enantiomers.

Absorption↗
PubMed1985

Isolation and characterization of an Fc receptor from neonatal rat small intestine.

Receptors for the Fc region of IgG from neonatal rat intestinal brush borders were solubilized using 3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propane sulfonate and purified by affinity chromatography. Analysis of IgG-binding material by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions reveals two components with apparent Mr of 41 000-50 000 and 15 000. The larger component is glycosylated and may dimerize, giving a 100-110-kDa band on nonreduced gels. Both proteins are localized in the proximal small intestine, where IgG is specifically taken up during the first three weeks of neonatal life, and disappear when specific transport stops after weaning. Electron irradiation of brush borders shows that the functional unit for IgG binding has a molecular weight in situ of 110 kDa. These data suggest that a dimer of the 41-50-kDa protein together with the 15 kDa and other proteins may mediate intestinal transport of maternal IgG.

Animals↗
PubMed1993

Large, detergent-resistant complexes containing murine antigens Thy-1 and Ly-6 and protein tyrosine kinase p56lck.

A number of human and mouse leukocyte surface (glyco)proteins anchored in a membrane via glycosylphosphatidylinositol (GPI) moiety have been previously shown to be noncovalently associated with protein tyrosine kinases (Science 1991. 254: 1016; J. Biol. Chem. 1992. 267: 12317). Here we show that two murine antigens of this group, Thy-1 and Ly-6, implicated in the activation of the T cells, are associated with each other, with the kinase p56lck and with several of potential kinase substrates in very large, detergent-resistant complexes, the size of which is between 50 and 200 nm, as determined by ultrafiltration and gel chromatography. Experiments on simultaneous solubilization of mixed human and mouse cells rule out that the observed complexes are artifacts induced by the detergent. Complexes of similar composition and properties were obtained when either detergents Brij-58, Nonidet-P40 or 3-[(3-cholamidopropyl)-dimethylammonio]- 1-propane-sulfonate (Chaps) were used for solubilization of the cells, while octylglucoside at least partially dissociated them. These "GPI-complexes" may be essential for the well-known signal-transducing capacity of Thy-1 and Ly-6.

Animals↗
PubMed2005

Transient T cell accumulation in lymph nodes and sustained lymphopenia in mice treated with FTY720.

FTY720 (2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride) is an orally available immunomodulatory agent that induces severe peripheral blood lymphopenia. Most studies of these lymphopenic effects have been limited to short-term exposure to FTY720. FTY720 alters the ability of lymphocytes to respond to sphingosine-1-phosphate (S1P) through S1P receptors, particularly S1P1. FTY720 affects different leukocyte populations and their trafficking through major lymphoid organs. We show the dynamics of CD4 T, CD8 T, and B lymphocyte recirculation in all major lymphoid compartments during 21-day FTY720 treatment of normal C57BL/6 mice. Following a transient increase in peripheral lymph nodes and Peyer's patches, lymphocyte recirculation reaches a new steady state. Other lymphoid organs show transient changes in lymphocyte composition with various patterns. At 21 days of FTY720 treatment, total body lymphocyte content is reduced by 20% and blood lymphocytes by 80%. Modeling suggests that the new steady state is due to a combination of reduced naive lymphocyte release from the thymus and a transient reduction of lymphocyte egress from lymph nodes. Our data indicate that the commonly held belief that FTY720 blocks lymphocyte egress from lymph nodes cannot fully explain the lymphocyte dynamics observed with prolonged treatment.

Animals↗
PubMed1988

Immobilized pH gradients: effect of salts, added carrier ampholytes and voltage gradients on protein patterns.

Salts formed from strong acids and bases (e.g. NaCl, Na2SO4, Na2HPO4), present in a protein sample applied to an immobilized pH gradient (IPG) gel, induce protein modification (oxidation of iron moiety in hemoglobin) already at low levels (5 mM) and irreversible denaturation (precipitation) at higher levels (greater than 50 mM). This effect is due to production of strongly alkaline cationic and strongly acidic anionic boundaries formed by the splitting of the salt's ion constituents, as the protein zone is not and can not be buffered by the surrounding gel until it physically migrates into the gel matrix. Substitution of "strong" salts in the sample zone with salts formed by weak acids and bases, e.g.. Tris-acetate, Tris-glycinate, Good's buffers such as (N-[2-acetamido]-2-iminodiacetic acid (ADA), (2-[(2-amino-2-oxoethyl)-amino] ethanesulfonic acid (ACES), (3-[N-morpholino]propane sulfonic acid (MOPS), essentially abolishes both phenomena, oxidation and irreversible denaturation. Suppression of "strong" salt's effects is also achieved by adding, to the sample zone, carrier ampholytes in amounts proportional to the salt present (e.g. by maintaining a salt: carrier ampholytes molar ratio of at least 1:1). This suppression is due to the strong buffering power of the added carrier ampholytes, able to counteract drastic pH changes in the two moving boundaries. A reduction of these deleterious effects of strong salts is also achieved when the IPG run is performed at low voltage for a prolonged time (4 h at 500 V instead of only 1 h at 500 V, before switching to high-voltage settings). Guidelines are given for trouble-free IPG operations.

Ampholyte Mixtures↗
PubMed1992

Elimination of sample diffusion and lateral band spreading in isoelectric focusing employing ready-made immobilized pH gradient gels.

A simple procedure for the elimination of lateral sample as well as band spreading in precast, ready-made immobilized pH gradient gels is described. Round or rectangular holes are punched in the dry polyacrylamide gels prior to rehydration. The generated wells proved suitable for application of samples containing surfactants such as Nonidet P-40 or 3-[(3-cholamidopropyl) dimethylammonio]-1- propane-sulfonate (CHAPS). Lateral band spreading and precipitation of samples containing up to 9.5 M urea could be completely eliminated by this method.

Cholic Acids↗
PubMedDate not supplied

Native polyacrylamide gel electrophoresis of membrane proteins: glutaminase detection after in situ specific activity staining.

A new procedure for the analysis and detection of phosphate-activated glutaminase (EC 3.5.1.2) by native electrophoresis has been developed. The method is based on the in situ detection of glutaminase activity in two different systems of native polyacrylamide gradient gels, containing 3-(3-cholamidopropyl)-dimethyl-ammonio-1-propane sulfonate (CHAPS) or Triton X-100 as nondenaturant detergents. Crude Triton X-100 extracts of mitochondria were resolved by electrophoresis. The enzyme was specifically revealed by incubation of the gel with glutamine and coupling the oxidation of the glutamate formed to the reduction of a tetrazolium dye, in the presence of glutamate dehydrogenase trapped in a 1% agar solid overlay. Both Ehrlich ascitic cell and mouse kidney glutaminases were resolved by native electrophoresis and specifically detected with the activity staining. Moreover, the redox-cycling staining was tested in solution, showing linearity with the amount of glutamate or glutaminase activity present. The method described could be a useful tool for native polyacrylamide gel electrophoresis of membrane proteins.

Animals↗
PubMedDate not supplied

Molecular modeling of acrylamide derivatives: the case of N-acryloylaminoethoxyethanol versus acrylamide and trisacryl.

Molecular mechanics (for evaluation of total energies of individual structures of monomers and oligomers) and molecular dynamics (for evaluating dynamic dependencies of structural features) were used for obtaining information on some unique chemical behavior of a novel N-substituted acrylamide (N-acryloylaminoethoxyethanol; AAEE) vs. conventional acrylamide and trisacryl (N-acryloyl-2-amino-2-hydroxymethyl-1,3-propane diol, an extremely hydrophilic derivative; Tris-A). As free monomers, Tris-A degrades with zero-order and acrylamide with first-order kinetics, whereas AAEE is highly resistant to hydrolysis. It is found that Tris-A (and its dideoxy derivative) is constantly forming hydrogen bonds between the -OH groups and the carbonyl of the amido group (bond distances of 1.64 to 1.70 A); this activates a mechanism of "N-O acyl transfer" which leads to quick degradation of the amido bond even under mildly alkaline conditions. Conversely, AAEE (which also contains an omega-OH group increasing its hydrophilicity) has no tendency to form H-bonds with the amido carbonyl, thus being resistant to the above degradation mechanism. In fact, the oxygen in the ethoxy moiety of the N-substituent chain acts as a preferential partner for H-bond formation with the omega-OH group. In the oligomeric state, it is found that Tris-A (tetrameric and dodecameric structures were simulated) tends to form inter-residue H-bonds (approximately parallel to the growing chain) competing with the intra-residue H-bonds (folding onto the amido carbonyl and approximately perpendicular to the oligomer chain), thus greatly increasing its stability.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylamide↗
PubMed1994

Gel polymerization in detergents: conversion efficiency of methylene blue vs. persulfate catalysis, as investigated by capillary zone electrophoresis.

Four types of detergents are commonly used in biochemical analysis of proteins and polypeptides: neutral, e.g., Triton X-100, Nonidet P-40; anionic, typically sodium dodecyl sulfate (SDS); cationic, e.g., cetyltrimethylammonium bromide CTAB), and zwitterionic, e.g., sulfobetaine 3-12 and 3[(3-cholamido-propyl) dimethyl-ammonio]-1-propane sulfonate (CHAPS). These detergents are utilized not only in the protein solubilization step, but also in the polyacrylamide gel matrix in which subsequent electrophoretic separation is carried out. The conversion efficiency of monomers into the growing polymer, in the presence of the four types of detergents, was assessed by capillary zone electrophoresis (CZE) in a micellar system comprising 100 mM SDS, by extracting unreacted monomers from the gel phase and quantifying the peaks separated by CZE. Two different catalyst systems were evaluated: the standard persulfate-N,N,N',N'-tetramethylethylenediamine (TEMED) couple and a mixture comprising methylene blue in presence of the redox couple sodium toluene sulfinate and diphenyliodonium chloride. In the chemically initiated system (persulfate), there was a strong inhibition of polymerization, decreasing in the following order: CTAB > sulfobetaine 3-12 > SDS > CHAPS > Triton X-100 (e.g., in 10 mM CTAB 100% inhibition was experienced). On the contrary, in photopolymerization (as driven by methylene blue) good conversion of monomers into the growing polymer (> 95%) was always obtained, independent of the nature of the detergent present in the polymerization step.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonium Sulfate↗
PubMed1996

Purification of thermamylase in multicompartment electrolyzers with isoelectric membranes: the problem of protein solubility.

The main alpha-amylase from Bacillus licheniformis (called thermamylase because of its resistance to high temperatures, 90 degrees C) has been subjected to purification by isoelectric focusing in multicompartment electrolyzers with isoelectric membranes. The enzyme tended to precipitate, producing severe smears in proximity of its pI value (7.18). Solubility could not be ameliorated by any of the known means typically adopted in isoelectric focusing and compatible with enzyme activity, such as addition of neutral and zwitterionic surfactants (e.g., Nonidet, 3-[(3-cholamidopropyl)dimethylammonio]-1-propane-sulfonate, up to 2%), mixed hydro-organic solvents (glycerol, ethylene glycol, propylene glycol) and addition of zwitterions unable to form micelles, such as taurine. However, addition of sugars, notably saccharose, sorbitol, and, to a lesser extent, sorbose, greatly improved protein solubility in the pI proximity. The improvement was dramatic if these sugars were admixed with 0.2 M taurine. Additionally, the increment of solubility (which occurred when reaching a level of 40% of the different sugars) was accompanied by a large pI shift, typically reducing the pI value by as much as 0.4 pH units (e.g., from a pI of 7.18 in the absence of additives to a pI of 6.80 in presence of a mixture of 40% sucrose and 0.2 M taurine, the best solubilizer in all the series investigated). This apparent pI shift was not due to a change of pH gradient caused by the presence of additives, since pH measurements in the absence as well as presence of additives gave identical results. The results are explained by the theory of Timasheff and Arakawa on stabilization of protein structure by solvents: sugars (at ca. 1 M concentration) and zwitterions such as taurine belong to class I stabilizers, characterized by negative binding to proteins and by increasing the surface tension of water. As a result, the protein is in a state of "superhydration", which might prevent binding to Immobilines in the gel matrix and might alter some pKs on the protein surface. In solutions of 40% saccharose and 0.2 M taurine, thermamylase could be successfully purified to a single isoelectric and isoionic band in the multicompartment electrolyzer.

Bacillus↗
PubMed1997

Preparative two-dimensional gel electrophoresis of membrane proteins.

Electrophoretic techniques, and especially two-dimensional gel electrophoresis (2-DE), have provided an indispensable set of tools for the separation of complex protein mixtures as well as for the identification of protein-protein interactions. Nevertheless, after its introduction more than twenty years ago and even with recent technical developments, the separation of integral and peripheral membrane proteins, in amounts sufficient for microsequencing, is still a difficult task. Lipids present in the membrane as well as the low solubility of hydrophobic membrane proteins result in protein aggregation both on the sample application point and on isoelectric focusing. As a consequence many proteins do not enter the first or second dimension of 2-DE. Here we describe the modification of a protocol using a combination of 3-[(3-cholamidopropyl)-dimethylammonio]-1-propane sulfonate (CHAPS), chaotropic agents (thiourea, urea), Tris base and reducing agents (1,4-dithioerythritol) to improve solubilization of integral and peripheral membrane proteins. Preparative amounts of membrane proteins (up to 2 mg) were loaded during reswelling of dry immobilized pH gradients and the resulting Coomassie staining patterns were largely superimposable with silver-stained gels obtained from identical samples (4 microg). This indicates that the recovery of proteins from the sample is not significantly compromised by the scale-up procedure. A direct application of this method for the characterization and identification of membrane proteins from cellular organelles is described in another paper in this issue (I. Fialka et al., Electrophoresis 1997, 18, 2582-2590).

Animals↗
PubMed1998

Molecular imprint polymers as highly selective stationary phases for open tubular liquid chromatography and capillary electrochromatography.

Chiral separations employing molecular imprint polymer (MIP) stationary phases in both open tubular liquid chromatography (OT-LC) and capillary electrochromatography (OT-CEC) are demonstrated. MIPs are highly crosslinked polymers containing spatial and functionality memory of template molecules which provide a higher degree of selectivity when used as stationary phases for chromatographic separations. Thin films of molecular imprinted polymers bonded to the inner walls of 25 microm ID fused-silica capillaries were prepared using an in situ polymerization technique developed in our laboratory that allows the use of conventional fused-silica capillaries with polyimide outer coatings. The success rate in preparing such open tubular columns was about 70%. Methacrylic acid and 2-vinyl pyridine were chosen as functional monomers, and either ethylene dimethacrylate or trimethylol propane trimethacrylate was used as the crosslinker. Toluene was employed as the porogen. Effects of polymerization conditions on column preparation and chromatographic performance were studied. Enantiomeric separations of D- and L-dansyl phenylalanines were achieved in both OT-LC and OT-CEC modes with good selectivity and efficiencies. Both types of separations may be performed on the same column using a single commercial instrument.

Capillary Action↗
PubMed1980

Mutagenicity of 2- and 3-carbon halogenated compounds in the Salmonella/mammalian-microsome test.

Short-chain, 2- and 3- carbon halogenated hydrocarbons were tested for mutagenicity for Salmonella typhimurium strain TA 100 both with and without the presence of S-9. Without exception, all brominated derivatives were more mutagenic than the chlorinated derivatives, usually by a substantial order of magnitude. 2-Fluoroethanol, the only fluorinated compound tested, showed little or no mutagenic activity up to 100 micromole per plate concentration. Two highly purified propane derivatives containing a halogen atom on each of the three carbons showed little or no direct mutagenic activity. A third trihalogenated compound with a halogen atom on each carbon atom showed some direct mutagenic activity, probably due to impurities. However, all three trihalogenated compounds were highly active mutagens following S-9 activation. The presence of a double bond in the case of 1, 2, 3-trichloropropene resulted in a higher level of direct mutagenic activity than 1, 2, 3-trichloropropane, but activation with S-9 resulted in a further increase in mutagenic activity with the former compound. On the other hand, S-9 caused a substantial decrease in mutagenic activity of most compounds containing a double bond. With the presence of an alcoholic group in a compound, the addition of S-9 caused variable responses, increasing the number of his+ revertant colonies due to 2, 3-dibromopropanol but had little or no effect with five other compounds containing an alcoholic group. Evidence is also presented that the position of a double bond in relation to the halogen atoms may influence mutagenic activity.

Biotransformation↗