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PubMed1988

Unique promotion of erythrophagocytosis by malondialdehyde.

Modification of the normal erythrocyte membrane by reagent malondialdehyde (MDA) promotes phagocytosis of red blood cells by human macrophages, a phenomenon previously shown to involve both IgG-dependent and IgG-independent mechanisms and to be demonstrable even at micromolar MDA concentrations. In the present studies, we demonstrate this effect using 1mM MDA prepared both by acid hydrolysis of malonaldehyde bis-(dimethyl acetal) and by enzymatic synthesis from 1,3-propanediol. Remarkably, we find that equimolar amounts of other mono- and dialdehydes fail to promote erythrophagocytosis despite similarity to MDA in size and structure and ability to cross link. Authentic MDA seems to be unique among small aldehydes in ability to promote erythrophagocytosis at low aldehyde concentration and, therefore, has a special biologic relevance among the great variety of peroxidation byproducts.

Aldehydes↗

PubMed2001

Effect of water activity and immobilization on fatty acid selectivity for esterification reactions mediated by lipases.

The effect of water activity (a(w)) and immobilization on fatty acid (FA) selectivity of Burkholderia (formerly Pseudomonas) cepacia, Rhizomucor miehei, Candida antarctica (type B), and Candida rugosa lipases in esterification reactions was determined. Studies were based on measuring ester formation in multicompetitive reaction mixtures containing either the homologous series of even carbon number n-chain saturated FA (C4-C18) or a series of n-chain (un)saturated FA (C18:X, where X = 0-3 double bonds) as cosubstrates with 1,3-propanediol in ter-butyl methyl ether at a(w) of 0.19, 0.69, and 0.90. Activity and FA selectively patterns were similar for free and Celite-adsorbed lipases in response to changes in a(w'), although specific effects were observed for selectivity of B. cepacia and C. rugosa lipases toward C16 and C4/C6 FA, respectively. Also, selectivity toward unsaturated C18:X FA as a group was modulated by changes in a(w) for three of the four lipase studied. Resin-fixed lipases from R. miehei and C. antarctica exhibited profound differences in activity and FA selectively in response to changes in a(w'), relative to free and Celite-bound forms. These findings suggest that FA selectivity for lipid modification is influenced by a(w) and immobilization, but that each lipase has a characteristic response to these factors in a manner that cannot be predicted.

Anion Exchange Resins↗

PubMed2003

Optknock: a bilevel programming framework for identifying gene knockout strategies for microbial strain optimization.

The advent of genome-scale models of metabolism has laid the foundation for the development of computational procedures for suggesting genetic manipulations that lead to overproduction. In this work, the computational OptKnock framework is introduced for suggesting gene deletion strategies leading to the overproduction of chemicals or biochemicals in E. coli. This is accomplished by ensuring that a drain towards growth resources (i.e., carbon, redox potential, and energy) must be accompanied, due to stoichiometry, by the production of a desired product. Computational results for gene deletions for succinate, lactate, and 1,3-propanediol (PDO) production are in good agreement with mutant strains published in the literature. While some of the suggested deletion strategies are straightforward and involve eliminating competing reaction pathways, many others suggest complex and nonintuitive mechanisms of compensating for the removed functionalities. Finally, the OptKnock procedure, by coupling biomass formation with chemical production, hints at a growth selection/adaptation system for indirectly evolving overproducing mutants.

Algorithms↗

PubMed2005

Estimating optimal profiles of genetic alterations using constraint-based models.

Metabolic engineering involves application of recombinant DNA methods to manipulate metabolic networks to improve cellular properties. It is critical that the genetic alterations be performed in an optimal manner to maximize profit. In addition to the product yield, productivity consideration is also critical, especially for the production of bulk chemicals such as 1,3-propanediol. In this work, we demonstrate that it is suboptimal from the standpoint of productivity to induce genetic alteration at the start of the production process. A bi-level optimization scheme is formulated to determine the optimal temporal flux profile for the manipulated reaction. In the first case study, an optimal flux in the reaction catalyzed by glycerol kinase is determined to maximize the glycerol production at the end of a 6-h batch cultivation of Escherichia coli under aerobic conditions. The final glycerol concentration is 30% higher for the optimal flux profile compared with having an active flux during the entire batch. The effect of the mass transfer coefficient on the optimal profile and the glycerol concentration is also determined. In the second case study, the anaerobic batch fermentation of the ldh(-) strain of Escherichia coli is considered. The optimal flux in the acetate pathway is determined to maximize the final ethanol concentration. The optimal flux results in higher ethanol concentration (11.92 mmol L(-1)) compared to strains with no acetate flux (8.36 mmol L(-1)) and fully active acetate flux (6.22 mmol L(-1)). We also examine the effects of growth inhibition due to high ethanol concentrations and variations in final batch time on ethanol production.

Algorithms↗

PubMed1996

Preparative electrophoresis on linear polyacrylamide-agarose composite gels.

A preparative method for isolating centigram quantities of high molecular weight polypeptide chains with high resolution and recovery uses linear polyacrylamide/agarose composite (LPAC) gels as electrophoretic media from which the polypeptides can be easily extracted. The composites are prepared in a manner yielding linear copolymers of acrylamide and 1-allyloxy-2,3-propanediol within 2% agarose gels. After electrophoresis in sodium dodecyl sulfate (SDS), protein bands were rapidly visualized for excision by briefly immersing the gel in cold 0.1 M KCl which precipitates the protein-associated SDS. The gel slices are then freeze-thawed to disrupt the agarose matrix and promote syneresis of fluid upon centrifugation. The polypeptides are then separated from the polyacrylamide in the supernatant solution by precipitating with either acidic isopropanol, trichloroacetic acid, ammonium sulfate or other general protein precipitants. As determined with polypeptide chains of fibrinogen and its cross-linked derivatives, recoveries were virtually complete (95.4% +/- 2.2%), and were independent of molecular weights over the range tested (10(4) --10(6)).

Electrophoresis, Agar Gel↗

PubMed2003

Ultrathin-layer sodium dodecyl sulfate disc electrophoresis of proteins in the range from 10 to 220 kDa in homogeneous, low-concentrated polyacrylamide gels.

This study describes an ultrathin-layer sodium dodecyl sulfate (SDS) disc electrophoresis in polyacrylamide gels of a thickness of only 150 microm. By use of 2-amino-2-methyl-1,3-propanediol/glycine instead of traditional Tris/HCl buffer in the resolving phase of the gel, proteins with a wide range of molecular sizes (10 kDa to over 220 kDa) are separated in unusually low-concentrated gels (4%T, 3.3%C). 2-Amino-2-methyl-1,3-propanediol in the resolving part of the gel contributes to stabilization of the pH value at 8.8, while glycine improves destacking as well as separation of small proteins from the bulk of stacked SDS. This method combines both the advantages of conventional slab-gel electrophoresis and capillary gel electrophoresis. It is easy to apply and well suited for all further miniaturization attempts.

Animals↗

PubMed2006

Mechanism of enantioseparation of DL-pantothenic acid in ligand exchange capillary electrophoresis using a diol-borate system.

Borate complexes formed in the ternary system at pH 9.2 containing borate, (S)-3-amino-1,2-propanediol (SAP), and DL-pantothenic acid (DL-PTA) were identified by 13C and 11B NMR, and it is confirmed that the binary complexes, [B(OH)2(SAP)], [B(SAP)2]+ [B(OH)2(D- or L-PTA)]2-, and [B(D- or L-PTA)2]3- (including [B(D-PTA)(L-PTA)]3-), and the ternary complexes, [B(SAP)(D- or L-PTA)]-, coexist at equilibrium in the ternary system. Thermodynamic experiments by variable-temperature 11B NMR revealed that the ternary complex, [B(SAP)(D-PTA)]-, is entropically more stable than [B(SAP)(L-PTA)]-. Because two geometrical isomers are possible for the respective ternary complexes, semi-empirical molecular orbital calculations were performed by PM5, PM3, and AM1 methods in order to obtain the optimized structures. It is indicated from the calculated heats of formation and experimentally obtained thermodynamic parameters that the (S)-isomer is more probable for the respective ternary complexes with D- and L-PTA. In the optimized structure of (S)-[B(SAP)(D-PTA)]- in water, the SAP and D-PTA ligands were oppositely oriented to form a rather linear structure, while the diastereomer, (S)-[B(SAP)(L-PTA)]-, had a folded structure. Because such a difference in the solvated structure of the ternary complexes can give a different electrophoretic velocity in CE, the enantioseparation of DL-PTA in CE is reasonably attributed to a difference in the observed electrophoretic mobility for the equilibrated ternary systems containing the respective ternary complexes.

Borates↗

PubMed2006

Chiral resolution of monosaccharides as 1-phenyl-3-methyl-5-pyrazolone derivatives by ligand-exchange CE using borate anion as a central ion of the chiral selector.

Six reducing monosaccharides (mannose, galactose, fucose, glucose, xylose, and arabinose) were derivatized with 1-phenyl-3-methyl-5-pyrazolone (PMP) and chiral resolution of these racemic PMP-monosaccharides was studied by ligand-exchange CE using borate anion as a central ion of the chiral selector and (S)-3-amino-1,2-propanediol (SAP) as a chiral selector ligand. PMP-mannose, PMP-galactose and PMP-fucose were successfully enantioseparated. Lowering the capillary temperature increased the resolution of PMP-mannose system, but decreased that of PMP-galactose and PMP-fucose systems. Whereas the maximum resolution was obtained at pH 8.9 in the PMP-mannose system, resolution increased gradually with pH in the PMP-galactose and PMP-fucose systems. Expecting the formation of the ternary borate complexes with SAP and PMP-monosaccharide in the CE experiments, the optimized structures of the borate diastereomers were obtained by semiempirical molecular orbital calculations to discuss the structural difference of the diastereomers in connection with the enantioseparation behaviors.

Anions↗

PubMed1994

Chemical mutagenesis testing in Drosophila. X. Results of 70 coded chemicals tested for the National Toxicology Program.

Seventy chemicals were tested for the ability to induce sex-linked recessive lethal (SLRL) mutations in postmeiotic and meiotic germ cells of male Drosophila melanogaster. As in the previous studies in this series, adult feeding was chosen as the first route of administration. If the compound failed to induce mutations by this route, injection exposure was used. Two chemicals, n-butane and propylene, were gaseous and therefore tested only by inhalation. One chemical (dimethylcarbamoyl chloride) was tested only by injection. Those chemicals that were mutagenic in the SLRL assay were further tested for the ability to induce reciprocal translocations. Sixteen of the 70 chemicals tested were mutagenic in the SLRL assay: 3-chloro-2-methylpropene, 3-(chloromethyl)pyridine HCl, dimethylcarbamoyl chloride, HC blue 1,3-iodo-1,2-propanediol, malaoxon, N,N'-methylene-bis-acrylamide, 4,4'-methylenedianiline 2HCl, ziram, cis-dichlorodiaminoplatinum II, 1,2-dibromoethane, dibromomannitol, 1,2-epoxypropane, glycidol, myleran, and toluene diisocyanate. The last seven also induced reciprocal translocations. A comparison of the results from the SLRL assay with other assays for mutagens and carcinogens suggests that the SLRL assay is highly specific, but poorly sensitive, both for mutagens and potential carcinogens.

Animals↗

PubMed1983

Glycerol transport and phosphorylation by rat hepatocytes.

The entry of glycerol into isolated rat hepatocytes appears to be catalyzed by a specific carrier. At a physiological concentration of 0.1 mM, glycerol utilization is rate limited by the permeation step. Intracellular glycerol is trapped by an excess of glycerol kinase, which has a higher apparent affinity for the substrate than that of the membrane carrier. The entry of glycerol into the hepatocytes is highly sensitive to inhibition by monoacetin and cytochalasin B, but not by DL-1,2-propanediol, erythritol, D-glucose, D-galactose, D-mannose, or D-fructose.

Animals↗

PubMed2002

Effect of a basic organic excipient on the dissolution of diclofenac salts.

Dissolution of diclofenac from compressed discs containing mixtures of a diclofenac salt and a basic excipient, in various w/w ratios, was examined. Two diclofenac salts, diclofenac deanol (DDNL) and diclofenac tert-butylamine, and the basic excipient 2-amino-2-methyl-1,3-propanediol (AMPD) were examined. Inclusion of the soluble basic excipient at high loadings enhanced the dissolution rate of diclofenac tert-butylamine fivefold; however, it retarded dissolution of the DDNL salt 40-fold in the weight fraction range 40-80% AMPD, despite the fact that AMPD is more than four times more soluble than DDNL. These findings were attributed to the solubilities of salts formed between diclofenac and the basic excipient used. The "salt conversion model" was developed to predict dissolution from mixtures of a salt of an ionizable drug and an ionizable excipient capable of forming a salt with the drug. Deviations from the model at high weight fractions of base and, in the case of the systems containing the more soluble drug, at low weight fractions of base were attributed to carrier-controlled dissolution. The present work illustrates that the solubility of potential salts, which may form between the drug and ionizable excipients present has an important influence on the dissolution of the drug from such compressed mixtures.

Crystallography, X-Ray↗

PubMed1982

Stereospecific metabolic reduction of ketones.

The stereospecificity of the metabolic reduction of arylalkylketones was investigated. The ketones, propiophenone (I), phenyl-acetone (III), and 1-phenyl-1,2-propanedione (V) were reduced in vitro and in vivo in rats and rabbits to the corresponding alcohols, 1-phenyl-1-propanol (II), 1-phenyl-2-propanol (IV), and 1-phenyl-1,2-propanediol (VIII), respectively. For the analysis, a capillary GLC method employing chiral derivatizing reagents for the resolution of these optically active alcohols was utilized. This study revealed that the metabolic reduction of each ketone produced the corresponding alcohol as a mixture of its enantiomers. With one exception, the mixtures obtained from all in vivo and in vitro reactions were shown to contain at least 70% of one isomer [S(-)-II, S(+)-IV, and erythro-VIII, respectively], with in vitro reduction showing the highest degree of stereospecificity (90-98%). The in vivo reduction of I by the rat was exceptional in that both optical isomers of II were recovered in equal proportions.

Alcohols↗

PubMed1984

Determination of the structure of a synthetic impurity in guaifenesin: modification of a high-performance liquid chromatographic method for phenylephrine hydrochloride, phenylpropanolamine hydrochloride, guaifenesin, and sodium benzoate in dosage forms.

An impurity present in all commercial guaifenesin-containing dosage forms examined was isolated and identified as 2-(2-methoxyphenoxy) 1,3-propanediol (VI). The eluant of a previously developed stability-indicating liquid chromatographic method for phenylephrine hydrochloride (I), phenylpropanolamine hydrochloride (II), and guaifenesin (III) was modified to yield a better separation between phenylpropanolamine and the impurity. The method was expanded to include sodium benzoate (IV), a preservative found in some liquid formulations.

Benzoates↗

PubMed1985

Dynamics of disinfection of selected preservatives against Escherichia coli.

Mathematical models were determined relating preservative concentration and D values (decimal reduction times at 25 degrees C; pH 6.9-7.1) against Escherichia coli in aqueous medium. Preservatives investigated were 2-bromo-2-nitro-1,3-propanediol (Bronopol), N-(hydroxymethyl)-N-(1,3-dihydroxymethyl-2, 5-dioxo-4-imidazolidinyl)-N'-(hydroxymethyl)urea (Germall II), phenethyl alcohol, and benzyl alcohol. Linear regression was used to determine D values [i.e., the time required for a particular concentration of preservative at a specified pH, temperature, and medium to cause a 90% reduction of viable organisms (E. coli)] from a number of concentrations of each preservative. Linear regression of the log D values versus the log of the concentration (a minimum of 4 concentrations per preservative) were used to derive power curves. Concentration exponents, eta values (the logarithmic values relating changes in rates of kill for specified changes in concentrations) and A values (extrapolated D values at 1% concentration), were determined. Correlation coefficients for these power fits ranged from -0.987 to -0.999. Plots depicting the closeness of fit of the models to the actual data are shown.

Culture Media↗

PubMed1986

2,3,5-Triphenyltetrazolium chloride as a novel tool in germicide dynamics.

A novel, colorimetric method using 2,3,5-triphenyltetrazolium chloride (TTC) in tandem with membrane filtration is described for the determination of death rates of Escherichia coli (E. coli) due to microbiocides. This method enables results to be obtained on the same day in contrast to the 18 h required by the accepted aerobic plate count method. The microbiocides investigated were the preservatives 2-bromo-2-nitro-1,3-propanediol (Bronopol), N-(hydroxymethyl)-N-(1,3-dihydroxymethyl-2,5- dioxo-4-imidazolidinyl)-N'-(hydroxymethyl)-urea (Germall II), phenethyl alcohol, and benzyl alcohol. D values (time required per log reduction of E coli) were determined by this method, and equations relating the D values to preservative concentrations were derived [i.e., eta values (the logarithmic values relating changes in rates of kill for specified changes in concentration) and A values (extrapolated D values at 1% concentration) were determined]. these equations are compared with those previously published using the accepted aerobic plate count method. The potential advantages of this method are that it has a broad range of application as TTC is reduced by a wide variety of microbes; the test is easily done; results can be achieved in one day; dead cells do not cause interference; test sensitivity can be increased by increasing the length of incubation time or by using membrane filtration in tandem with TTC reduction; and preservative inactivation may be achieved by filtration and flushing with an inactivator, or by adding neutralizers to the TTC broth.

Colorimetry↗

PubMed1989

Identification of components in iodinated glycerol.

Iodinated glycerol (CAS no. 5634-39-9), therapeutically used as an expectorant and source of organically bound iodine, was analyzed to determine the purity and composition of the chemical samples used in carcinogenicity and toxicity studies. The manufactured product is described by the patent and chemical literature as a mixture of two isomeric iodopropylideneglycerols (structures 1 and 2). The results of our studies, however, indicate that the two principal components of the product were 3-iodo-1,2-propanediol (IPD) and glycerol (GLY). Analyses from GC-MS (full scan electron impact) and carbon-13 nuclear magnetic resonance spectrometry provided conclusive identification of these components. The quantification of IPD and GLY in one of two samples of commercial product using GC-flame ionization detection indicated concentrations of 33 and 17%, respectively (Sample A). Similar concentrations were determined for a second sample from the same source (Sample B), which was a gratis sample procured approximately nine years after Sample A. Numerous minor components were also observed in these two samples. These components were tentatively identified as condensation products of glycerol and iodine-containing analogues. The iodopropylideneglycerol compounds, described in the patent, were not observed in either of the two samples.

Carbon Isotopes↗

PubMed1994

Methocarbamol degradation in aqueous solution.

The kinetics of the hydrolysis of methocarbamol to the corresponding diol guaifenesin in aqueous solution was studied. Methocarbamol was rather stable in acidic media but easily hydrolyzed in alkaline solution. The formation of an unknown compound, proved to be an isomer of methocarbamol [the 3-(2-methoxyphenoxy)-propanediol 2-carbamate] is involved. The amounts of methocarbamol and the two degradation products resulting from storage of methocarbamol in various buffer solutions over a pH range of 8.0 to 10.0 at 70-80 degrees C (ionic strength, 0.5 M), were followed as a function of time by a reversed-phase HPLC stability-indicating method to clarify the degradation pathway of methocarbamol in alkaline solutions. Analysis of the concentration-time profiles reveals that base-catalyzed methocarbamol hydrolysis proceeded mainly through the formation of its isomer. The observed degradation rates followed approximately pseudo-first-order kinetics at constant pH and temperature.

Drug Stability↗

PubMed2005

Use of automated direct sample introduction with analyte protectants in the GC-MS analysis of pesticide residues.

Automated large-volume direct sample introduction, or difficult matrix introduction (DMI), was investigated in the determination of 44 pesticide residues possessing a wide range of physico-chemical properties (volatility, polarity, pK(a)) in fruit-based baby food by means of gas chromatography-mass spectrometry (GC-MS) with a quadrupole mass analyzer. DMI has advantages over traditional injection because large volumes (up to 30 microL) of potentially dirty sample extracts can be injected into the GC-MS, but nonvolatile matrix components that would normally contaminate the inlet are removed after every injection. The extra matrix and glass surfaces involved in DMI, however, make the system more prone to the matrix-induced chromatographic enhancement effect, which adversely affects quantification of several pesticides. To overcome this problem, matrix-matched calibration standards and/or the use of analyte protectants were applied in the DMI approach, and the analysis of extracts was also compared before and after undergoing clean-up by dispersive solid-phase extraction. For best quantification, clean-up was still needed, and the combination of matrix-matching with analyte protectants gave the most reproducible results. Depending on the application, however, the addition of analyte protectants (a mixture of 3-ethoxy-1,2-propanediol, L-gulonic acid 3-lactone, and D-sorbitol) to sample extracts and calibration standards in solvent (non-matrix matched), gave satisfactory quantification for most of the 44 pesticides tested. The lowest calibration levels for 34 of the 44 pesticides were < or = 10 ng/g, which meets the standard required by the European Union Baby Food Directive (2003/13/EC).

Calibration↗