Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PYRROLIDONES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1998

The unusually slow unfolding rate causes the high stability of pyrrolidone carboxyl peptidase from a hyperthermophile, Pyrococcus furiosus: equilibrium and kinetic studies of guanidine hydrochloride-induced unfolding and refolding.

To elucidate the energetic features of the anomalously high-level stabilization of a hyperthermophile pyrrolidone carboxyl peptidase (PfPCP) from a hyperthermophilic archaeon, Pyrococcus furiosus, equilibrium and kinetic studies of the guanidine hydrochloride (GuHCl)-induced unfolding and refolding were carried out with CD measurements at 220 nm in comparison with those from the mesophile homologue (BaPCP) from Bacillus amyloliquefaciens. The mutant protein of PfPCP substituted with Ser at both Cys142 and Cys188 (PfC142/188S) was used. The GuHCl unfolding for PfC142/188S and BaPCP was reversible. It was difficult to obtain the equilibrated unfolding curve of the hyperthermophile proteins at temperatures below 50 degreesC and pH 7, because of the remarkably slow rate of the unfolding. The unfolding for PfC142/188S attained equilibrium after 7 days at 60 degreesC, resulting in the coincidence between the unfolding and refolding curves. The Gibbs energy change of unfolding, DeltaGH2O (56.6 kJ/mol), for PfC142/188S at 60 degreesC and pH 7 was dramatically higher than that (7.6 kJ/mol) for BaPCP at 40 degreesC and pH 7. The unfolding and refolding kinetics for PfC142/188S and BaPCP at both 25 and 60 degreesC at pH 7 were approximated as a single exponential. The rate constant in water (kuH2O) of the unfolding reaction for PfC142/188S (1.6 x 10(-)15 s-1) at 25 degreesC and pH 7 was drastically reduced by 7 orders of magnitude compared to that (1.5 x 10(-)8 s-1) for BaPCP, whereas the refolding rates (krH2O) in water for PfC142/188S (9.3 x 10(-)2 s-1) and BaPCP (3.6 x 10(-)1 s-1) at 25 degreesC and pH 7 were similar. These results indicate that the greater stability of the hyperthermophile PCP was characterized by the drastically slow unfolding rate.

Circular Dichroism↗
PubMedDate not supplied

Synthesis, characterization, and preliminary biological study of poly(3-(tert-butoxycarbonyl)-N-vinyl-2-pyrrolidone).

Poly(3-(tert-butoxycarbonyl)-N-vinyl-2-pyrrolidone) has been synthesized and characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, NMR spectroscopy, and thermal analysis. The polymer is a chemically amplified photoresist. Arrays of lines with 25 microm width and 25 microm spacing were successfully patterned with this polymer by photolithography. Rat fibroblast cells were seeded on these patterned surfaces as well as the smooth glass surface. Phase contrast microscopy showed that cells on the patterned surfaces were strongly aligned and elongated along the grooves as compared to randomly spreading on the smooth surface. Since controlling cell orientation is critical for the development of advanced forms of tissue repair and cell engineering therapies, for example, peripheral nerve repair, production of tendon and ligament substitutes in vitro, and control of microvascular repair, the described polymer may be useful for applications in tissue reconstruction.

Animals↗
PubMedDate not supplied

Removal of high phenol concentrations with adapted activated sludge in suspended form and entrapped in calcium alginate /cross-linked poly(N-vinyl pyrrolidone) hydrogels.

The present work evaluates the aerobic removal of 0.25-2 g/L of phenol by adapted activated sludge in batch and continuous reactors, in suspended form and trapped in polymeric hydrogel beads of calcium alginate(1%) and cross-linked poly(N-vinyl pyrrolidone), x-PVP (4%). The mechanical and chemical resistance of the entrapping hydrogel was also evaluated in three different media: (I) rich in phosphate and ammonium ions; (II) using alternate P and N sources, and (III) without nutrients. The adapted consortium removed phenol concentrations up to 2 g/L more efficiently in the immobilized systems. A decrease in phenol removal rate was observed as the food/microorganisms (F/M) ratio increased. A zero-order kinetics was observed with phenol concentrations > 1 g/L and a first-order kinetics at concentrations < 1 g/L. The best response (100% removal) was in the continuous reactors using type II medium, with a hydraulic residence time (HRT) of 12.5 h, an influent pH = 5, and an F/M ratio below 0.25. The immobilizing matrix deteriorated after 170 h of use in continuous reactors, especially with media I and II, probably due to the attrition forces, to chemical weakness of the material, and to the pressure of the bacterial growth inside the bead.

Alginates↗
PubMedDate not supplied

High-throughput purification of combinatorial libraries II: Automated separation of single diastereomers from a 4-amido-pyrrolidone library containing intentional diastereomer pairs.

A 4-amido-pyrrolidone library that was intentionally synthesized as pairs of diastereomers was produced by solution-phase parallel syntheses and purified by an automated high-throughput purification system. A total of 2592 4-amido-pyrrolidinones were ultimately isolated as single diastereomers from a matrix of 1920 syntheses. After the four-step synthesis and HPLC purification, the average yield of a single diastereomer was 36.6%. The average chemical purity was >90%, and the average diastereomeric purity was >87%. The choice of chiral amines used to make amides with heterocyclic acid chlorides had a dramatic effect on success. Analysis of the relationship between amines used for synthesis and the diastereomeric separation showed that amides made from chiral 1,2-amino alcohols gave superior separation to amides from chiral morpholines. The presence of a hydrogen bond donor on the amide side chain seems to be required for a better diastereomeric separation.

Journal Article↗
PubMed2000

Synthesis and characterization of water-soluble silver(I) complexes with L-histidine (H2his) and (S)-(-)-2-pyrrolidone-5-carboxylic acid (H2pyrrld) showing a wide spectrum of effective antibacterial and antifungal activities. Crystal structures of chiral helical polymers [Ag(Hhis)]n and ([Ag(Hpyrrld)]2)n in the solid state.

Two water-soluble, silver(I) complexes showing a wide spectrum of effective antibacterial and antifungal activities, i.e., ([Ag(Hhis)].0.2EtOH)2 (1; H2his = L-histidine) and [Ag(Hpyrrld)]2 (3; H2pyrrld = (S)-(-)-2-pyrrolidone-5-carboxylic acid) were prepared. In aqueous solution 1 and 3 were present as dimers, whereas in the solid state they were polymers. Crystallization of 1 by slow evaporation and/or vapor diffusion gave water-insoluble crystals of [Ag(Hhis)]n (2) showing modest antimicrobial activities. The complex 1 in the solid state is a polymer formed by intermolecular hydrogen-bonding interactions between dimeric [Ag(Hhis)]2 cores, while 2 is a different polymer without a core complex. X-ray crystallography revealed that 2 was a left-handed helical polymer consisting of a bent, 2-coordinate silver(I) atom bonding to the Namino atom of one Hhis- ligand and the N pi atom of a different Hhis- ligand. Of particular note is the fact that Ocarboxyl atoms do not participate in the coordination. X-ray crystallography also revealed that 3 was a left-handed helical polymer formed by self-assembly of dimeric [Ag(Hpyrrld)]2 cores with an intramolecular metal(I)-metal(I) interaction (Ag-Ag distance, 2.9022(7) A). The FT-IR and the solid-state 13C and 15N NMR spectra showed that the dimeric core of 1 was formed through Ag-N bonds, while that of 3 was formed through Ag-O bonds. The molecular ions of 1 and 3 were detected by the positive-ion electrospray ionization (ESI) mass spectrometry. For 1-3, characterization by elemental analysis, TG/DTA, FT-IR, and variable-temperature solid-state 13C NMR and room-temperature 15N NMR measurements was performed, and for 1 and 3, that by solution molecular weight measurements and solution (109Ag, 1H, and 13C) NMR spectroscopies was also carried out. The antibacterial and antifungal activities of 1 and 3 were remarkable and comparable to those of the previous silver(I)-N-heterocycle complexes.

Anti-Bacterial Agents↗
PubMed2005

Organocatalytic regio- and asymmetric C-selective S(N)Ar reactions-stereoselective synthesis of optically active spiro-pyrrolidone-3,3'-oxoindoles.

The first example of catalytic enantioselective nucleophilic aromatic substitution of beta-dicarbonyl compounds is presented. An O-benzoylated cinchona alkaloid derivative catalyst gave a selective C-arylation reaction compared to, e.g., the corresponding benzylated catalyst which provided a 1:1 mixture of the C- and O-arylation products. The reaction proceeds well for various aromatic compounds with different 1,3-dicarbonyl compounds, and the optically active products are obtained in very high yields and with up to 92% ee. One further scope of the organocatalytic enantioselective nucleophilic aromatic substitution reaction is demonstrated by the synthesis of the optically active spiro-pyrrolidone-3,3'-oxoindole structure.

Journal Article↗
PubMed2005

5,5-Dimethyl-2-pyrrolidone-N-oxyl formation in electron spin resonance studies of electrolyzed NaCl solution using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trapping agent.

Electrolyzed oxidizing (EO) water has recently generated much interest as a disinfectant in the food industry. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) is a spin trapping agent widely used in the electron spin resonance (ESR) characterization of oxygen-centered free radicals. The reaction between electrolyzed water, collected from the anode side of a two-chamber electrolyzer, and DMPO was investigated by ESR spectroscopy. Addition of DMPO to EO water generated an ESR spectrum identical to that of 5,5-dimethyl-2-pyrrolidone-N-oxyl (DMPOX), suggesting that a compound from EO water oxidized DMPO with the formation of DMPOX. To further investigate the electrolytically generated compound that oxidized DMPO, aqueous solutions of different sodium salts (sodium chloride, sodium citrate, and sodium iodide) with similar conductivities were electrolyzed. The DMPOX signal was not detected in the electrolyzed sodium citrate sample, suggesting that DMPOX formation in the electrolyzed NaCl sample might be due to an electrolytically generated chlorine species. A low DMPOX signal was also observed from the electrolyzed NaI sample, suggesting that a similar species obtained through the electrolysis of I- can also oxidize DMPO. Hypochlorous acid is proposed to oxidize the spin trap DMPO with the formation of DMPOX. In a neutral pH environment, electrolyzed water also oxidized DMPO to DMPOX. This is consistent with the DMPOX formation in the reaction of chlorine water (containing HOCl and Cl2) or sodium hypochlorite with DMPO.

Cyclic N-Oxides↗
PubMed1985

Stereoselectivity of muscarinic receptors in vivo and in vitro for oxotremorine analogues. N-[4-(tertiary amino)-2-butynyl]-5-methyl-2-pyrrolidones.

The enantiomers of three 5-methyl-2-pyrrolidone analogues of the muscarinic agent oxotremorine (1) were synthesized. The pyrrolidine derivative (R)-13 was an antagonist to carbachol in the guinea pig ileum and also showed central and peripheral antimuscarinic activity in vivo. It was more potent and more selective than atropine in antagonizing the central effects of 1. The dimethylamino analogue (R)-14 and the trimethylammonium salt (R)-15 were potent agonists in the guinea pig ileum. (R)-14 showed both central muscarinic (hypothermia) and central antimuscarinic activity (antagonism of oxotremorine-induced tremor) in vivo. The R enantiomers of 13-15 were considerably more potent than the S enantiomers in vivo and in vitro irrespective of whether agonist or antagonist activity was measured. From a comparison of the contribution of the methyl group at the chiral center to the overall affinities, it is suggested that agonists and antagonists in this series bind in an essentially identical manner to the muscarinic receptor.

Abdominal Muscles↗
PubMed2004

Discovery of 4-substituted pyrrolidone butanamides as new agents with significant antiepileptic activity.

(S)-alpha-ethyl-2-oxopyrrolidine acetamide 2 (levetiracetam, Keppra, UCB S.A.), a structural analogue of piracetam, has recently been approved as an add-on treatment of refractory partial onset seizures in adults. This drug appears to combine significant efficacy and high tolerability due to a unique mechanism of action. The latter relates to a brain-specific binding site for 2 (LBS for levetiracetam binding site) that probably plays a major role in its antiepileptic properties. Using this novel molecular target, we initiated a drug-discovery program searching for ligands with significant affinity to LBS with the aim to characterize their therapeutic potential in epilepsy and other central nervous system diseases. We systematically investigated the various positions of the pyrrolidone acetamide scaffold. We found that (i) the carboxamide moiety on 2 is essential for affinity; (ii) among 100 different side chains, the preferred substitution alpha to the carboxamide is an ethyl group with the (S)-configuration; (iii) the 2-oxopyrrolidine ring is preferred over piperidine analogues or acyclic compounds; (iv) substitution of positions 3 or 5 of the lactam ring decreases the LBS affinity; and (v) 4-substitution of the lactam ring by small hydrophobic groups improves the in vitro and in vivo potency. Six interesting candidates substituted in the 4-position have been shown to be more potent antiseizure agents in vivo than 2. Further pharmacological studies from our group led to the selection of (2S)-2-[(4R)-2-oxo-4-propylpyrrolidin-1-yl]butanamide 83alpha (ucb 34714) as the most interesting candidate. It is approximately 10 times more potent than 2 as an antiseizure agent in audiogenic seizure-prone mice. A clinical phase I program has been successfully concluded and 83alpha will commence several phase II trials during 2003.

Acoustic Stimulation↗
PubMed2002

Influence of hydrogen bonding in the activation of nucleophiles: PhSH-(catalytic) KF in N-methyl-2-pyrrolidone as an efficient protocol for selective cleavage of alkyl/aryl esters and aryl alkyl ethers under nonhydrolytic and neutral conditions.

The nucleophilicity of arenethiols can be augmented via hydrogen bonding with "naked" halide anion. The activity of the halide anions follow the order F(-) >> Cl(-) approximately Br(-) approximately I(-) and is dependent on the countercation (Bu(4)N approximately Cs approximately K > Na >> Li). The solvent plays an important role in nucleophilic activation as well as regeneration of the effective nucleophile (e.g. ArS(-)) and those with high dielectric constant, high molecular polarizability, high donor number (DN), and low acceptor number (AN) are the most effective. Selective deprotection of alkyl/aryl esters and aryl alkyl ethers can be achieved under nonhydrolytic and neutral conditions by the treatment with thiophenol in 1-methyl-2-pyrrolidone (NMP) in the presence of a catalytic amount of KF. Aryl esters are selectively deprotected in the presence of alkyl esters and alkyl methyl ethers during intramolecular competitions.

Journal Article↗
PubMed2005

Synthesis of 4-aryl-2-pyrrolidones and beta-aryl-gamma-amino-butyric acid (GABA) analogues by Heck arylation of 3-pyrrolines with arenediazonium tetrafluoroborates. Synthesis of (+/-)-rolipram on a multigram scale and chromatographic resolution by semipreparative chiral simulated moving bed chromatography.

We report herein a new, practical, and economic synthesis of the phosphodiesterase inhibitor Rolipram on a multigram scale as well as the synthesis of new 4-aryl pyrrolidones and beta-aryl-gamma-amino butyric acids (GABA derivatives) employing an efficient Heck-Matsuda arylation of 3-pyrroline with aryldiazonium tetrafluoroborates. Racemic Rolipram was resolved into its enantiomers using chiral simulated moving bed chromatography having the low-cost microcrystalline cellulose triacetate as a chiral stationary phase.

Borates↗
PubMed2005

Single-chain mechanical property of poly(N-vinyl-2-pyrrolidone) and interaction with small molecules.

The single-chain nanomechanical properties of poly(N-vinyl-2-pyrrolidone) (PVPr) and povidone-iodine (PVPr-I2) under different solution conditions have been investigated by using an atomic force microscopy based technique-single-molecule force spectroscopy. The force-extension curve (force curve) of PVPr in water is markedly deviated from that obtained in ethanol or tetrahydrofuran, suggesting a different interaction between PVPr and the solvents. Moreover, we have comparatively studied the force signals of PVPr-I2 and PVPr in an aqueous solution of KI or KI3 and found that only KI3 influences the elastic property of PVPr dramatically. These experimental results indicate that there exists a specific interaction between PVPr and KI3, which is also supported by Fourier transform infrared data. By the integration of the deviated area between the force curve and the modified freely jointed chain fitting curve, we estimate that the energy needed to destroy the interaction between PVPr and water is 5.3 kT and between PVPr and KI3 is 3.6 kT per repeating unit, respectively.

Journal Article↗
PubMed2005

DFT study of the monomers and dimers of 2-pyrrolidone: equilibrium structures, vibrational, orbital, topological, and NBO analysis of hydrogen-bonded interactions.

A computational study of the monomers and hydrogen-bonded dimers of 2-pyrrolidone was executed at different DFT levels and basis sets. The above dimeric complexes were treated theoretically to elucidate the nature of the intermolecular hydrogen bonds, geometry, thermodynamic parameters, interaction energies, and charge transfer. The processes of dimer formation from monomers and concerted reactions of double proton transfer were considered. The evolution of geometry, vibrational frequencies, charge distribution, and AIM properties in going from monomers to dimers was systematically followed. The solvent effects upon dimer formation were investigated in terms of the self-consistent reaction field (SCRF Onsager model). For the monomers and three dimers, vibrational frequencies were calculated and the changes in frequencies of the vibrations most sensitive to complexation were discussed. The orbital interactions were shown to lengthen the X-H (X = N, O) bond and lower its vibrational frequency (a red shift). To better understand the nature of the corresponding intermolecular interactions, we performed natural bond orbital (NBO) analysis. Topological analysis of electron density at bond critical points (BCP) was executed for complex molecules using the Bader's atoms in molecules (AIM) theory. The interaction energies were calculated, and the basis set superposition errors (BSSE) were estimated systematically. Satisfactory correlations between the structural parameters, interaction energies, and electron density characteristics at BCP were found.

Journal Article↗
PubMed2006

Broadband dielectric study of dynamics of poly(vinyl pyrrolidone)-ethylene glycol oligomer blends.

Broadband dielectric measurements for blends of poly(vinyl pyrrolidone) (PVP) and ethylene glycol oligomer (EGO) from 0 to 40 wt % PVP were carried out at 25 degrees C in the frequency range from 20 Hz to 20 GHz. The EGOs used in this study were ethylene glycol (EG), diethylene glycol (2EG), and PEG400 (MW = 400). For the PVP-EG, -2EG, and -PEG400 blends, relaxation processes caused by the motion of EGO in the GHz range and the micro-Brownian motion of the PVP chain at 10 kHz-1 MHz were observed. Although the PVP-EGO blend is miscible, relaxation processes caused by the molecular motion of EGO and the local chain motion of PVP were observed individually. The relaxation time of the local chain motion of PVP showed a strong PVP concentration dependence and a solvent viscosity dependence, which are similar to those reported so far for the solutions in nonpolar solvents.

Journal Article↗
PubMed1999

Chemical stability of peptides in polymers. 1. Effect of water on peptide deamidation in poly(vinyl alcohol) and poly(vinyl pyrrolidone) matrixes.

This paper examines the effect of water content, water activity, and glass transition temperature (T(g)) on the deamidation of an asparagine-containing hexapeptide (VYPNGA; Asn-hexapeptide) in lyophilized poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) at 50 degrees C. The rate of Asn-hexapeptide deamidation increases with increasing water content or water activity and, hence, decreasing T(g). The rate of deamidation is more sensitive to changes in these parameters in PVA than in PVP. Deamidation is clearly evident in the glassy state in both formulations. In the glassy state, the peptide is more stable in PVA than in PVP formulations but is less stable in the rubbery state. No single variable (water content, water activity, or T(g)) could account for the variation in deamidation rates in PVA and PVP formulations. Deamidation rates were correlated with the degree of plasticization by water (distance of T(g) from the dry intrinsic glass transition temperature); coincident curves for the two polymers were obtained with this correlation. Deamidation in PVA and PVP was closely correlated with the extent of water-induced plasticization experienced by the formulation relative to its glass transition at 50 degrees C, suggesting that the physical state of formulations could be used to predict chemical stability.

Adsorption↗
PubMed2005

Photochemical preparation of poly(N-vinyl-2-pyrrolidone)-stabilized platinum colloids and their deposition on titanium dioxide.

Preparation processes for Pt-deposited TiO(2) (Pt/TiO(2)) by the synthesis of Pt nanoparticles and their deposition were pursued by transmission electron microscopy, extended X-ray absorption fine structure, UV-vis spectroscopy, and Fourier transform infrared spectroscopic studies. Colloidal dispersions of Pt particles stabilized by poly(N-vinyl-2-pyrrolidone) (PVP) were photochemically synthesized in aqueous ethanol solution. The average diameter of Pt particles was estimated to be 2.0 +/- 0.5 nm, which was almost unchanged by changing the reducing agent from ethanol to methanol and 2-propanol. The PVP-stabilized Pt particles were distributed over a TiO(2) surface only by mixing the Pt colloidal dispersions and TiO(2). CO was chemically coordinated on the Pt particles on a TiO(2) surface after heat treatment was carried out in an O(2) flow at 673 K to completely remove the residual PVP on Pt/TiO(2). Hydrogen reduction at 473 K did not increase the amount of CO adsorbed on Pt sites. The Pt/TiO(2) catalyst after the oxidation treatment showed higher activity for CO photooxidation than that obtained for pure TiO(2) catalyst. The CO photooxidation rate was not unchanged by the H(2) reduction.

Journal Article↗
PubMed2005

Surfactant--polymer aggregates formed by sodium dodecyl sulfate, poly(N-vinyl-2-pyrrolidone), and poly(ethylene glycol).

The interaction of sodium dodecyl sulfate (SDS) in aqueous solution with poly(N-vinyl-2-pyrrolidone) (M(w) = 55,000 g/mol) in the presence of poly(ethylene glycol) (M(w) = 8000 g/mol) is investigated by electrical conductivity, zeta potential measurements, viscosity measurements, fluorescence spectroscopy, and small-angle X-ray scattering (SAXS). The results indicate that SDS-polymer interaction occurs at low surfactant concentration, and its critical aggregation concentration is fairly dependent on polymer composition. The polymer-supported micelles have average aggregation numbers dependent on surfactant concentration, are highly dissociated when compared with aqueous SDS micelles, and have zeta potentials that increase linearly with the fraction of PVP at constant SDS concentration. The analysis of the SAXS measurements indicated that the PVP/PEG/SDS system forms surface-charged aggregates of a cylindrical shape with an anisometry (length to cross-section dimension ratio) of about 3.0.

Journal Article↗
PubMed2006

High-quality luminescent tellurium nanowires of several nanometers in diameter and high aspect ratio synthesized by a poly (vinyl pyrrolidone)-assisted hydrothermal process.

Large-scale selective synthesis of uniform single crystalline tellurium nanowires with a diameter of 4-9 nm, and microbelts with a width of 250-800 nm and tens of micrometers in length, can be realized by a poly (vinyl pyrrolidone) (PVP)-assisted hydrothermal process. The formation of tellurium nanowires and nanobelts in the presence of PVP is strongly dependent on the reaction conditions such as temperature, the amount of PVP, and reaction time. The results demonstrated that the keys for selective synthesis of Te nanobelts and nanowires are to modulate the growth rates of (100), (101), and (110) planes in the presence of PVP and to precisely control the reaction kinetics. High-quality luminescent ultrathin t-Te nanowires with a diameter of 4-9 nm display strong luminescent emission in the blue-violet region. This approach provides a facile route for the production of high-quality tellurium nanostructures with an interesting optical property. Furthermore, the synthesized ultrathin nanowires with deep blue color and nanobelts in gray color by this approach can be well dispersed in water or ethanol, making it possible for further engineering of their surfaces to prepare other hybrid core-shell nanostructures.

Journal Article↗