Abstract  Microemulsions prepared using 1-decanol, oleic acid or oleyl alcohol as oils, Transcutol and 1,2-hexanediol as surfactant mixture and phosphate buffer pH 6.0 as aqueous phase were studied to verify the effect of the oils on pig-skin permeation and accumulation of acyclovir (ACV). Pseudoternary phase diagrams were constructed in the absence and in the presence of ACV. ACV-containing microemulsions had a restricted area of existence compared to those without the drug. A cationic charge-inducing agent, L-alanine benzyl ester, was added to the formulations to prepare positively-charged microemulsions. Full-thickness pig ear skin was used for ACV permeation experiments using positively-andnegatively-charged microemulsions and a control suspension. The presence of oleyl alcohol or oleic acid increased the flux but not the drug skin accumulation compared to a control suspension, while the use of the cationic charge-inducing agent had no influence on the formulation performance. A two-fold increase in ACV accumulation was found using the microemulsions containing 1-decanol, maintaining intact the structure of the stratum corneum, as demonstrated by the DSC analysis. Microemulsions containing 1-decanol could significantly optimize drug targeting, maintaining the structure of the stratum corneum intact.

Abstract  Lactobacillus reuteri metabolises glycerol efficiently to form 3-hydroxypropionic acid (3-HP) and 1,3-propanediol (1,3PDO) by the same mechanism as that for 1,2-propanediol (1,2PDO) conversion to propionic acid and propanol via its propanediol utilization (pdu) pathway. Pdu enzymes are encoded by the pdu-operon, which also contain genes encoding the shell proteins of the microcompartment housing the metabolic pathway. In this work the selectivity and kinetics of the reactions catalysed by L. reuteri DSM20016 Pdu enzymes glycerol dehydratase (GDH), 1,3-propanediol oxidoreductase (PduQ) and coenzyme-A acylating propionaldehyde dehydrogenase (PduP), produced recombinantly, was investigated against corresponding substrates of different chain lengths. Glycerol dehydratase exhibited activity against C2-C4 polyols, with the highest activity against glycerol and 1,2-propanediol (1,2-PDO). A double mutant of the pduC gene of GDH (PduC-S302A/Q337A) was constructed that displayed lowered activity against glycerol and 1,2PDO but extended the substrate range upto C6-diol. The best substrate for both PduQ and PduP was 3-hydroxypropanal (3HPA), although PduP exhibited nearly 10-fold higher specific activity. The enzymes also showed some activity against C3-C10 aliphatic aldehydes, with PduP having higher relative activity. Subsequently, transformation of polyols using whole cells of L. reuteri containing the wild type- and mutated GDH, respectively, confirmed the reduced activity of the mutant against glycerol and 1,2PDO, but its activity against longer substrates was negligible. In contrast, recombinant Escherichia coli BL21(DE3) cells harboring the GDH variant converted diols with up to C6 carbon chain length to their respective aldehydes, suggesting that the protein shell of the microcompartment in L. reuteri posed a barrier to the passage of longer chain substrate.

Abstract  The viscosities of three polyols and three saccharides, all in the non-crystalline state, have been studied. Two of the polyols (2-methyl-1,4-butanediol and 1,2,3-butanetriol) were studied under dry conditions, the third (1,2,3,4-butanetetrol) was studied as a function of relative humidity (RH), including under dry conditions, and the saccharides (glucose, raffinose, and maltohexaose) were studied as a function of RH. The mean viscosities of the polyols under dry conditions range from 1.5  ×  10⁻¹ to 3.7  ×  10¹ Pa s, with the highest viscosity being that of the tetrol. Using a combination of data determined experimentally here and literature data for alkanes, alcohols, and polyols with a C₃ to C₆ carbon backbone, we show (1) there is a near-linear relationship between log₁₀ (viscosity) and the number of hydroxyl groups in the molecule, (2) that on average the addition of one OH group increases the viscosity by a factor of approximately 22 to 45, (3) the sensitivity of viscosity to the addition of one OH group is not a strong function of the number of OH functional groups already present in the molecule up to three OH groups, and (4) higher sensitivities are observed when the molecule has more than three OH groups. Viscosities reported here for 1,2,3,4-butanetetrol particles are lower than previously reported measurements using aerosol optical tweezers, and additional studies are required to resolve these discrepancies. For saccharide particles at 30 % RH, viscosity increases by approximately 2–5 orders of magnitude as molar mass increases from 180 to 342 g mol⁻¹, and at 80 % RH, viscosity increases by approximately 4–5 orders of magnitude as molar mass increases from 180 to 991 g mol⁻¹. These results suggest oligomerization of highly oxidized compounds in atmospheric secondary organic aerosol (SOA) could lead to large increases in viscosity, and may be at least partially responsible for the high viscosities observed in some SOA. Finally, two quantitative structure–property relationship models (Sastri and Rao, 1992; Marrero-Morejón and Pardillo-Fontdevila, 2000) were used to predict the viscosity of alkanes, alcohols, and polyols with a C₃–C₆ carbon backbone. Both models show reasonably good agreement with measured viscosities for the alkanes, alcohols, and polyols studied here except for the case of a hexol, the viscosity of which is underpredicted by 1–3 orders of magnitude by each of the models.

Abstract  The key regulatory step in the biosynthesis of abscisic acid (ABA), a hormone central to the regulation of several important processes in plants, is the oxidative cleavage of the 11,12 double bond of a 9-cis-epoxycarotenoid. The enzyme viviparous14 (VP14) performs this cleavage in maize (Zea mays), making it a target for the rational design of novel chemical agents and genetic modifications that improve plant behavior through the modulation of ABA levels. The structure of VP14, determined to 3.2-Å resolution, provides both insight into the determinants of regio- and stereospecificity of this enzyme and suggests a possible mechanism for oxidative cleavage. Furthermore, mutagenesis of the distantly related CCD1 of maize shows how the VP14 structure represents a template for all plant carotenoid cleavage dioxygenases (CCDs). In addition, the structure suggests how VP14 associates with the membrane as a way of gaining access to its membrane soluble substrate.

Abstract  Supercritical adsorption isotherms were measured for eicosane and 1,2-hexanediol on activated carbon and chromosorb 101 at 324.2K and 11.45 MPa. Adsorption isotherms of both solutes on activated carbon have typical shapes and can be modelled by Langmuir or Freundlich equations. For chromosorb 101 the equilibrium loadings are a linear function of the concentration of the solute in the fluid phase. These results suggest that for chromosorb 101 a partition of the solute between two immiscible phases rather than adsorption occurs. (c) 2005 Elsevier B.V. All rights reserved.

Abstract  In this study, the hydrogels composed of polyvinylpyrrolidone (PVP), kappa-carrageenan (kappa C), and 1,2-hexanediol (HD) were prepared by gamma-ray irradiation. The radiation dose was 25 kGy and the concentration of kappa C was 3 wt%. The physical properties of the hydrogels were investigated as a function of the concentrations of PVP and HD. The gel content and the tensile strength increased with increasing PVP concentration due to the crosslinking between the pyrrolidone molecules and decreased with increasing HD concentration. The degree of swelling was inversely proportional to the gel content because the highly crosslinked hydrogels had a tighter structure, hence reducing their water absorption. The antibacterial tests indicated that the hydrogels containing HD had antibacterial activity.

Abstract  The paper presents the results of viscosity measurements performed on 1,2-hexanediol in water and n-, s- and t-butanol solutions in the whole range of concentrations, at different temperatures. The activation energy for viscous flow of the solutions and the viscosity excess, were determined.

Abstract  Solubilities of 1-hexanol, or 1,2-hexanediol, or 2-hydroxypropanoic acid ethyl ester, or 2-hydroxyhexanoic acid ethyl ester in supercritical CO2 have been measured at T=(311, 318, and 323, or 328)K in the pressure range from 1 MPa to 8 MPa. The measurements have been performed using a flow-type equipment coupled with a novel analytical procedure. An accurate correlation method for the solubility of low volatile substances in supercritical CO2 based on the equilibrium condition for the solute has I,een proposed and successfully applied for the interpolation of our experimental results. (C) 1998 Academic Press.

Abstract  Dilatometric measurements of excess molar volumes. V-E and excess partial molar volumes, (V) over bar (E)(i) have been made for binary mixtures of acetonitrile with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 20 degreesC over the entire composition range. V-E for acetonitrile + 1,2-ethanediol and 1,2-propanediol mixtures are negative over the entire range of mole fractions and positive values are obtained for all remaining mixtures. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through O-H . . .N-C hydrogen bonding. From the experimental results. VF were calculated and correlated by Redlich-Kister type function in terms of mole fractions. The excess partial molar volumes were extrapolated to zero concentration to obtain the limiting values at infinite dilution, (V) over bar (/E,o)(i).

Abstract  The paper proposes a new method for amino acid determination which can be applied for amino acid profiling in solutions for parenteral nutrition. The MEKC method based on a mixed micellar system was developed for the separation of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate (AQC) derivatized amino acids. Background electrolyte was based on tris-borate buffer with high alkaline pH. Sodium dodecyl sulfate micelles were modified using 1,2-hexanediol as a co-surfactant. The effect of the modifier on amino acid migration was studied with respect to hydrophobicity of the analytes. The modifier appeared to be suitable to improve the separation of AQC-tagged amino acids without an adverse effect on buffer ionic strength or EOF velocity. The method was successfully validated and applied for amino acid profiling in medicinal preparations for parenteral nutrition. The results obtained were compared with a reference chromatographic method (amino acid analyser).

Abstract  UNLABELLED: Preservative agents determining the shelf life of cosmetic products must have effective antimicrobial activity while meeting safety requirements for topical use. In this study, we determined the antimicrobial activity of 1,2-hexanediol against several Gram-positive and Gram-negative bacteria. Antimicrobial susceptibility tests have shown that 1,2-hexanediol exhibits broad-spectrum activity against Gram-positive and Gram-negative bacteria with MICs of 0·5-2% (v/v). The bactericidal concentration of 1,2-hexanediol was ranging from 1 to 2 × MIC as demonstrated by time-kill curve assay. A membrane depolarization assay showed that 1,2-hexanediol disrupted the cytoplasmic membrane potential. A checkerboard assay indicated that the effective concentration of 1,2-hexanediol was reduced up to 0·25-0·5 × MIC when combined with macelignan and octyl gallate against Gram-positive bacteria. However, this combination was not effective against Gram-negative bacteria. A turbidity reduction assay demonstrated that the combination of a high concentration of 1,2-hexanediol with food-grade antimicrobial compounds could trigger lytic activity towards Bacillus cereus cells. The remaining cell turbidity was 24·6 and 22·2% when 2% of 1,2-hexanediol was combined with 8 mg l(-1) octyl gallate or with 32 mg l(-1) macelignan respectively. This study showed that food-grade antimicrobial compounds may be used in combination with 1,2-hexanediol to increase its efficacy as a preservative agent in cosmetics.

SIGNIFICANCE AND IMPACT OF THE STUDY: The antimicrobial activity of 1,2-hexanediol against Gram-positive and Gram-negative bacteria was potentiated with food-grade antimicrobials including xanthorrhizol, macelignan, panduratin A and octyl gallate, which have already been reported to display anti-inflammatory and other beneficial activities related to cosmetics. Therefore, the combination of 1,2-hexanediol and these food-grade antimicrobial agents would have benefits not only for increasing the antimicrobial activity but also in cosmetics use.

Abstract  In this study, we investigated a novel series of micelle modifiers useful to alter selectivity in micellar electrokinetic capillary chromatography (MEKC). These modifiers were alkyl polyalcohols, including 1-octanol, 1,2-octanediol, 1,2,3-octanetriol, 1,2-hexanediol, and 1,2-butanediol, which act as class I organic modifiers in that their effects are on the sodium dodecyl sulfate (SDS) micelle rather than the surrounding aqueous phase. This characteristic allows the alkyl polyols to effect resolution when applied at concentrations as low as 20 mM (0.25% v/v) by altering the selectivity observed with SDS without a modifier. The effects of the alkyl polyols on the critical micelle concentration of SDS, electroosmotic flow, and electrophoretic mobility of the SDS micelle are presented. These modifiers had little impact on the migration time window at the concentrations explored. Changes in selectivity induced by the alkyl polyols for a large set of model compounds are presented. Trends indicate that solutes capable of forming hydrogen bonds tend to decrease their interactions with the micellar phase while nonhydrogen bonding solutes increase their interactions upon addition of the modifiers. The solvation parameter model was used to characterize the induced changes in selectivity. This model suggests that even though the modifiers are structurally similar, each produced a unique set of system constants. It was also demonstrated that the addition of alkyl polyols improved the correlation between the partition coefficients of SDS and water to 1-octanol and water. The usefulness of the alkyl polyols was demonstrated by examining their effects on the separation of 11 priority phenols.

Abstract  The urinary metabolites of 2,5-dimethylhexane (2,5-DMH) in male Fischer 344 rats, administered the hydrocarbon by gavage, included 2,5-dimethyl-1-hexanoic acid, 2,5-dimethyl-1,2-hexanediol, 2,5-dimethyl-1,5-hexanediol, 2,5-dimethyl-2,5-hexanediol and 2,5-dimethyl-5-hydroxy-1-hexanoic acid. Metabolism favored the formation of the diols. The metabolites were identified using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). Histopathologic examination revealed moderate hyaline droplet formation in the renal proximal tubule.

Abstract  Dichloro or chloro ruthenium(III) complexes with polyaminopolycarboxylato ligands were synthesized (ligands: ethylenediaminetetraacetate (edta), N,N-dimethylethylenediamine-N,N'-diacetate (N,N'-Me(2)edda), and nitrilotriacetate (nta)). Magnetic moments of these ruthenium(III) complexes are about 2. So they are low spin complexes. The oxidation of olefines (cyclohexene, styrene or 1-hexene) catalyzed by these ruthenium(III) complexes in the presence of hydrogen peroxide has been studied: catalyst, polyaminopolycarboxylatoruthenium(III) complex (1.0 x 10(-3) mol dm(-3)); substrate, olefin (0.2 mol dm(-3)); co-oxidizing reagent, hydrogen peroxide (0.75 mol dm(-3)); solvent, 1,4-dioxane-water (1:1 (v/v)). The chloro Hedta ruthenium complex ([RuCl(Hedta)](-)) was the most effective catalyst for the oxidation under these conditions. The main product of this reaction was diol (yield:48%, 1,2-cyclohexanediol; 68%, 1-phenyl-1,2-ethanediol; 6.5%, 1,2-hexanediol). Since UV/visible spectrum of the edta complex in the presence of hydrogen peroxide shows the formation of the oxoruthenium(V) complex, the oxoruthenium(V) species is supposed to be the active species.

Abstract  A correct description of the aerosol's phases is required to determine its gas/particle partitioning, its reactivity and its water uptake and release. In this study, we investigate organic/electrolyte interactions of ammonium sulfate, nitrate and sodium chloride with substances containing carboxylic acids (COOH) and hydroxyl (OH) functional groups. As organic model compounds, we chose polyols with different OH/CHn (n = 0-3) ratios-namely, glycerol, 1,4-butanediol, and 1,2-hexanediol-as well as PEG 400 and a mixture of dicarboxylic acids consisting of malic, malonic, maleic, glutaric, and methylsuccinic acid. Bulk solubility and water activity measurements of these model systems together with a survey of literature data showed that NaCl is a salting-out agent for alcohols and organic acids whereas ammonium nitrate and sulfate exhibited salting-in and salting-out tendencies depending on the nature and number of functional groups as well as on the concentration of the solution. All investigated salts induce a liquid-liquid phase separation in the 1,2-hexanediol/water system. Considering the composition of the tropospheric aerosol, such phase separations might indeed occur frequently when particles in the atmosphere are exposed to varying relative humidity. To complement the bulk experiments, we investigated single particles consisting of ammonium sulfate and dicarboxylic acids as well as of ammonium sulfate and PEG 400 in an electrodynamic balance. Whereas the relative humidities of total deliquescence as well as the water uptake and release of the fully deliquesced particles are in good agreement with the bulk results and represent thermodynamic equilibrium, the water uptake before full deliquescence shows significant deviations. These deviations may be caused by morphological effects.

Abstract  Dilatometric measurements of excess molar volumes and excess partial molar volumes have been made for binary mixtures of N, N-dimethylformamide with 1,2-ethanediol, 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol at 20 degrees C over the entire composition range. The results are explained in terms of dissociation of the self-associated 1,2-alkanediol molecules and the formation of aggregates between unlike molecules through C = O ... 3H-O hydrogen bonding. Further, the effects of difference in chain lengths and steric factors on molecular interactions are also examined. From the experimental results, excess molar volumes were calculated and correlated by a Redlich-Kister type function in terms of mole fractions.

Abstract  The substrate scope of the flavoprotein alditol oxidase (AldO) from Streptomyces coelicolor A3(2), recombinantly produced in Escherichia coli, was explored. While it has been established that AldO efficiently oxidizes alditols to D-aldoses. this study revealed that the enzyme is also active with a broad range of aliphatic and aromatic alcohols. Alcohols containing hydroxy groups at the C-1 and C-2 positions like 1,2,4-butanetriol (K(m) =170 mM, k(cat) = 4.4 s(-1)), 1,2-pentanediol (K(m) = 52 mM, k(cat) = 0.85 s(-1)) and 1,2-hexanediol (K(m) = 97 mM, k(cat) = 2.0 s(-1)) were readily accepted by AIM Furthermore, the enzyme was highly enantioselective for the oxidation of 1,2-diols [e.g.. for 1-phenyl-1,2-ethanediol the (R)-enantiomer was preferred with all E-value of 74]. For several diols the oxidation products were determined by GC-MS and NMR. Interestingly. for all tested 1,2-diols the products were found to be the alpha-hydroxy acids instead of the expected alpha-hydroxy aldehydes. Incubation of (R)-1-phenyl-1,2-ethanediol with (18)O-labelled water (H(2)(18)O) revealed that a second enzymatic oxidation step occurs via the hydrate product intermediate. The relaxed Substrate specificity. excellent enantioselectivity, and independence of coenzymes make AldO an attractive enzyme for the preparation of optically pure 1,2-diols and alpha-hydroxy acids.

Abstract  The polyol dehydrogenase PDH-11300 from Deinococcus geothermalis was cloned, functionally expressed in Escherichia coli and biochemically characterized. The enzyme showed the highest activity in the oxidation of xylitol and 1,2-hexanediol and had an optimum temperature of 45 °C. The enzyme exhibited a T⁶⁰₅₀-value of 48.3 °C. The T⁶⁰₅₀ is the temperature where 50% of the initial activity remains after incubation for 1h. In order to elucidate the structural reasons contributing to thermostability, the substrate-binding loop of PDH-11300 was substituted by the loop-region of a homolog enzyme, the galactitol dehydrogenase from Rhodobacter sphaeroides (PDH-158), resulting in a chimeric enzyme (PDH-loop). The substrate scope of this chimera basically represented the average of both wild-type enzymes, but surprisingly the T⁶⁰₅₀ was noticeably increased by 7 °C up to 55.3 °C. Further mutations in the active site led to identification of residues crucial for enzyme activity. The cofactor specificity was successfully altered from NADH to NADPH by an Asp55Asn mutation, which is located at the NAD⁺ binding cleft, without influencing the catalytic properties of the dehydrogenase.

Abstract  From the Rhodobacter sphaeroides mutant D a galactitol dehydrogenase (GDH) was isolated and characterized in an earlier investigation (1). The enzyme expressed activity with a wide spread substrate spectrum, like sugars, sugar alcohols, secondary alcohols or the corresponding ketones and it can be used for the production of the rare sugar L-tagatose by regioselective oxidation of galactitol (2). This study focuses on the preparation of optically pure aliphatic diols by oxidation of one enantiomer or stereospecific reduction of keto-alcohols and diketones. The oxidation of 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol and 1,2-hexanediol occurred highly specific with the S-enantiomer leaving the R-enantiomer of the diols in the reaction vessel. Also (S)-1,2,6-hexanetriol was oxidized by GDH to 1,6-dihydroxy-2-hexanone. The Km values of these reactions decreased with increasing length of the carbon chain. Reduction of hydroxyacetone or 1-hydroxy-2-butanone resulted in an excess of 93% (S)-1,2-propanediol and more than 98% of (S)-1,2-butanediol, respectively. The diketone 2,3-hexanedione was only reduced to (2R,3S)-2,3-hexanediol, one of the possible four configurations. The wide substrate spectrum on one hand and the selectivity in the reaction on the other hand make GDH a very interesting enzyme for the production of optically pure building blocks in the chemical synthesis of bioactive compounds.