Pairwise interaction enthalpies of enantiomers of β-amino alcohols in DMSO + H2O mixtures at 298.15 K

The dilution enthalpies of enantiomers of six β-amino alcohols, namely (R)-(-)-2-amino-1-propanol versus (S)-(+)-2-amino-1-propanol, (R)-(-)-2-amino-1-butanol versus (S)-(+)-2-amino-1-butanol, and (R)-(-)-2-amino-1-pentanol versus (S)-(+)-2-amino-1-pentanol in dimethylsulfoxide (DMSO) + H(2)O mixtures (mass fractions of DMSO w = 0 to 0.3) have been determined respectively using an isothermal titration calorimeter (MicroCal ITC200, Northampton, MA, USA) at 298.15 K. According to the McMillan-Mayer theory, the corresponding homochiral enthalpic pairwise interaction coefficients (h(XX)) of the six amino alcohols have been calculated. It is found that across the whole studied composition range of mixed solvent, values of h(XX) for S-enantiomer are almost universally higher than those of R-enantiomer for each amino alcohol and that the variations of h(XX) depend largely on the composition of mixed solvent. The results were interpreted from the point of view of solute-solute interaction mediated by cosolvent DMSO, as well as competition equilibrium between hydrophobic-hydrophobic, hydrophilic-hydrophilic, and hydrophobic-hydrophilic interactions.     

Cytotoxicity of the MEIC reference chemicals in antioxidant-enriched, rat hepatoma-derived Fa32 cells

Since vitamin E increases the antioxidant status of cells, its influence on cytotoxicity was investigated. The neutral red uptake (NRU) inhibition effects of 39 MEIC reference chemicals were measured after treatment of rat hepatoma-derived Fa32 cells in the presence of vitamin E for 30 minutes. The results were quantified in terms of the NI50, the concentration of test compound required to reduce the NRU by 50%. Sodium chloride was the only chemical that was more toxic in the presence of vitamin E. This effect was related to the concentration of vitamin E in the cell culture medium. A vitamin E dose-related response was also observed for the decreased toxicity of paracetamol and caffeine. Glutathione levels were slightly increased in the presence of vitamin E, which could contribute to the protective effect of vitamin E. Of the remaining chemicals, 50% were less toxic in the presence of vitamin E, but the correlation with the acute human toxicity data of the MEIC study was not improved. The results imply that reactive oxygen species interfere with the toxicity of a high proportion of toxic chemicals. The assay described provides a quick and easy method for checking whether reactive oxygen species contribute to the toxicity of a chemical.     

Glutathione-dependent cytotoxicity of the chloroacetanilide herbicides alachlor, metolachlor, and propachlor in rat and human hepatoma-derived cultured cells

Alachlor, metolachlor, and propachlor are widely used chloroacetanilide herbicides. Their cytotoxicity in rat (Fa32) and human (Hep G2) hepatoma-derived cells was investigated, in connection with their influence on the endogenous glutathione (GSH) content, on the xenobiotic-metabolizing phase I enzymes 7-ethoxyresorufin O-deethylase (EROD) and 7-pentoxyresorufin O-depentylase (PROD), and phase II glutathione transferase (GST). The cytotoxicity was measured by the neutral red uptake inhibition assay. The following toxicity range was observed in both cell lines : propachlor>alachlor>metolachlor. When the endogenous GSH content was reduced by pretreatment of the cells with L-buthionine (S,R)-sulfoximine, the cytotoxicity of the herbicides increased strongly in both cell lines. EROD and PROD activities were dose-dependently increased to different degrees in Fa32, as was EROD in Hep G2, but no PROD activity was observed in these cells. The GSH content was not altered after 1 h treatment, and was approximately doubled after 24 h. GST activity was increased in Fa32 cells but not in Hep G2. A comparable cytotoxicity was observed for the investigated chloroacetanilides in both the rat and the human cell lines. Different interactions with xenobiotic-metabolizing phase I and II enzymes were observed, and GSH showed a protective effect against the acetanilides in both cell lines.     

Metabolic engineering of Escherichia coli for 1-butanol and 1-propanol production via the keto-acid pathways

Production of higher alcohols via the keto-acid intermediates found in microorganism's native amino-acid pathways has recently shown promising results. In this work, an Escherichia coli strain that produces 1-butanol and 1-propanol from glucose was constructed. The strain first converts glucose to 2-ketobutyrate, a common keto-acid intermediate for isoleucine biosynthesis. Then, 2-ketobutyrate is converted to 1-propanol through reactions catalyzed by the heterologous decarboxylase and dehydrogenase, or to 1-butanol via the chemistry involved in the synthesis of the unnatural amino acid norvaline. We systematically improved the synthesis of 1-propanol and 1-butanol through deregulation of amino-acid biosynthesis and elimination of competing pathways. The final strain demonstrated a production titer of 2 g/L with nearly 1:1 ratio of butanol and propanol.     

Close Correlation between Heat Shock Response and Cytotoxicity in Neurospora crassa Treated with Aliphatic Alcohols and Phenols

In Neurospora crassa the aliphatic alcohols methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, ethylene glycol, glycerol, and allyl alcohol and the phenolic compounds phenol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, sodium salicylate, and acetylsalicylic acid were analyzed with respect to their capacities to induce heat shock proteins (HSP) and to inhibit protein synthesis. Both the alcohols and phenols showed the greatest levels of HSP induction at concentrations which inhibited the overall protein synthesis by about 50%. The abilities of the different alcohols to induce the heat shock response are proportional to their lipophilicities: the lipophilic alcohol isobutanol is maximally inductive at about 0.6 M, whereas the least lipophilic alcohol, methanol, causes maximal induction at 5.7 M. The phenols, in general, show a higher capability to induce the heat shock response. The concentrations for maximal induction range between 25 mM (sodium salicylate) and 100 mM (resorcinol). Glycerol (4.1 M) shifted the concentration necessary for maximal HSP induction by hydroquinone from 50 to 200 mM. The results reveal that the induction of HSP occurs under conditions which considerably constrain cell metabolism. The heat shock response, therefore, does not represent a sensitive marker for toxicity tests but provides a good estimate for the extent of cell damage.     

Rhizomorph Formation in Fungi

The effect on growth and rhizomorph formation of 12 alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol, tert-butyl alcohol, 1-pentanol, iso-amyl alcohol, ethylene glycol and glycerol) at different concentrations has been examined for 2 isolates of Armillaria mellea (Vahl ex Fr.) Quél. and 1 of Clitocybe geotropa (Bull. ex Fr.) Quél. The fungi were cultivated for 28 days on a synthetic, liquid glucose medium with the alcohols as supplement. The following alcohols strongly stimulated growth and rhizomorph formation: ethanol, 1-propanol and 1-butanol. A great variation was demonstrated between the isolates in relation to rhizomorph production, morphology, and ability to be stimulated by different alcohols.     

Synthesis of Short-Chain Diols and Unsaturated Alcohols from Secondary Alcohol Substrates by the Rieske Nonheme Mononuclear Iron Oxygenase MdpJ

The Rieske nonheme mononuclear iron oxygenase MdpJ of the fuel oxygenate-degrading bacterial strain Aquincola tertiaricarbonis L108 has been described to attack short-chain tertiary alcohols via hydroxylation and desaturation reactions. Here, we demonstrate that also short-chain secondary alcohols can be transformed by MdpJ. Wild-type cells of strain L108 converted 2-propanol and 2-butanol to 1,2-propanediol and 3-buten-2-ol, respectively, whereas an mdpJ knockout mutant did not show such activity. In addition, wild-type cells converted 3-methyl-2-butanol and 3-pentanol to the corresponding desaturation products 3-methyl-3-buten-2-ol and 1-penten-3-ol, respectively. The enzymatic hydroxylation of 2-propanol resulted in an enantiomeric excess of about 70% for the (R)-enantiomer, indicating that this reaction was favored. Likewise, desaturation of (R)-2-butanol to 3-buten-2-ol was about 2.3-fold faster than conversion of the (S)-enantiomer. The biotechnological potential of MdpJ for the synthesis of enantiopure short-chain alcohols and diols as building block chemicals is discussed.     

Cystathionine pathway-dependent cytotoxicities of diethyl maleate and diamide in rat and human hepatoma-derived cell cultures

Glutathione (GSH) plays a role in many toxicologically important metabolic processes. It was previously established that L-buthionine S,R-sulphoximine (BSO), a specific inhibitor of (- glutamylcysteine synthetase, reduces the GSH content more efficiently in rat (Fa32) than in human (HEp-G2) hepatoma-derived cells. We therefore investigated whether the cystathionase inhibitor propargylglycine (PPG) could further decrease the BSO-induced GSH depletion in HEp-G2 cells. The influence of the cystathionine precursors N-acetylmethionine, methionine and homocysteine on the cytotoxicity of diethyl maleate (DEM) and diamide [1,1'-azobis(N,N-dimethylformamide)] was also investigated. PPG reduced the GSH content in both cell lines. A further GSH decrease in HEp-G2 was obtained when using a BSO + PPG combination containing relatively high concentrations of PPG. BSO diminished the toxicity of PPG. Homocysteine was the most efficacious of the tested cystathionine precursors in increasing the GSH content and reducing the cytotoxicity of DEM and diamide in Fa32 and HEp-G2 cells.     

Efficient and chemoselective N-acylation of 10-amino-7-ethyl camptothecin with poly(ethylene glycol)

A new poly(ethylene glycol) (PEG) conjugate of 10-amino-7-ethyl camptothecin, a potent antitumor analogue of camptothecin, has been synthesized and preliminary in vivo tests have been performed. Successful chemoselective N-acylation of 10-amino-7-ethyl camptothecin was accomplished using phenyl dichlorophosphate, a coupling reagent used in esterification of alcohols, while other coupling methods failed, due to the low nucleophilicity of the amino group in position 10. The conjugate was tested against P388 murine leukemia cell lines and resulted equipotent to CPT-11, a camptothecin analogue already in clinical use.     

Studies on the production of branched-chain alcohols in engineered Ralstonia eutropha

Wild-type Ralstonia eutropha H16 produces polyhydroxybutyrate (PHB) as an intracellular carbon storage material during nutrient stress in the presence of excess carbon. In this study, the excess carbon was redirected in engineered strains from PHB storage to the production of isobutanol and 3-methyl-1-butanol (branched-chain higher alcohols). These branched-chain higher alcohols can directly substitute for fossil-based fuels and be employed within the current infrastructure. Various mutant strains of R. eutropha with isobutyraldehyde dehydrogenase activity, in combination with the overexpression of plasmid-borne, native branched-chain amino acid biosynthesis pathway genes and the overexpression of heterologous ketoisovalerate decarboxylase gene, were employed for the biosynthesis of isobutanol and 3-methyl-1-butanol. Production of these branched-chain alcohols was initiated during nitrogen or phosphorus limitation in the engineered R. eutropha. One mutant strain not only produced over 180?mg/L branched-chain alcohols in flask culture, but also was significantly more tolerant of isobutanol toxicity than wild-type R. eutropha. After the elimination of genes encoding three potential carbon sinks (ilvE, bkdAB, and aceE), the production titer improved to 270?mg/L isobutanol and 40?mg/L 3-methyl-1-butanol. Semicontinuous flask cultivation was utilized to minimize the toxicity caused by isobutanol while supplying cells with sufficient nutrients. Under this semicontinuous flask cultivation, the R. eutropha mutant grew and produced more than 14?g/L branched-chain alcohols over the duration of 50?days. These results demonstrate that R. eutropha carbon flux can be redirected from PHB to branched-chain alcohols and that engineered R. eutropha can be cultivated over prolonged periods of time for product biosynthesis.     

Structure-Activity Relationship of Synthetic 2-Phenylnaphthalenes with Hydroxyl Groups that Inhibit Proliferation and Induce Apoptosis of MCF-7 Cancer Cells

In this study, six 2-phenylnaphthalenes with hydroxyl groups were synthesized in high yields by the demethylation of the corresponding methoxy-2-phenylnaphthalenes, and one 2-phenylnaphthalene with an amino group was obtained by hydrogenation. All of the 2-phenylnaphthalene derivatives were evaluated for cytotoxicity, and the structure-activity relationship (SAR) against human breast cancer (MCF-7) cells was also determined. The SAR results revealed that cytotoxicity was markedly promoted by the hydroxyl group at the C-7 position of the naphthalene ring. The introduction of hydroxyl groups at the C-6 position of the naphthalene ring and the C-4'' position of the phenyl ring fairly enhanced cytotoxicity, but the introduction of a hydroxyl group at the C-3'' position of the phenyl ring slightly decreased cytotoxicity. Overall, 6,7-dihydroxy-2-(4''-hydroxyphenyl)naphthalene (PNAP-6h) exhibited the best cytotoxicity, with an IC₅₀ value of 4.8 μM against the MCF-7 cell line, and showed low toxicity toward normal human mammary epithelial cells (MCF-10A). PNAP-6h led to cell arrest at the S phase, most likely due to increasing levels of p21 and p27 and decreasing levels of cyclin D1, CDK4, cyclin E, and CDK2. In addition, PNAP-6h decreased CDK1 and cyclin B1 expression, most likely leading to G₂/M arrest, and induced morphological changes, such as nuclear shrinkage, nuclear fragmentation, and nuclear hypercondensation, as observed by Hoechst 33342 staining. PNAP-6h induced apoptosis, most likely by the promotion of Fas expression, increased PARP activity, caspase-7, caspase-8, and caspase-9 expression, the Bax/Bcl-2 ratio, and the phosphorylation of p38, and decreased the phosphorylation of ERK. This study provides the first demonstration of the cytotoxicity of PNAPs against MCF-7 cells and elucidates the mechanism underlying PNAP-induced cytotoxicity.     

Effects of neutral salts and alcohols on the activity of Streptomyces caespitosus neutral protease

Streptomyces caespitosus neutral protease (ScNP) is one of the smallest metalloproteinase with a molecular mass of 14 kDa. Effects of solvent composition on ScNP activity were examined using a peptide substrate. The k(cat)/K(m) values of ScNP exhibited bell-shaped pH-dependence with the optimal pH of 6.4-7.0 and the pK(a) values of 5.0 +/- 0.1 and 8.3 +/- 0.1. ScNP activity increased in an exponential fashion with increasing [NaCl]. The relative k(cat)/K(m) value at 3.6 M NaCl to that at 0 M NaCl was 3.7, and the degree of the activation at x M NaCl was expressed as 1.2 (x) (x < 2.0) and 1.4(x) (x > 2.0). On the other hand, ScNP activity decreased with increasing concentrations of LiCl, KCl, NaBr, LiBr, KBr and NaClO(4). Alcohols inhibited ScNP activity with the IC(50) values, the concentration required for decreasing the activity at 50% of the maximum, of 0.77-6.54 M. The order of the inhibitory potency was 1-butanol, 2-methyl-1-propanol, 2-methyl-2-butanol > 2-methyl-2-propanol, 2-butanol, 1-propanol > 2-propanol > ethanol > methanol. The activities recovered completely by the dilution of alcohols, suggesting that the ScNP inhibition by alcohols is reversible. These characteristics of ScNP are compared with those of human matrix metalloproteinase 7 and thermolysin.     

Formation of higher alcohols and phenol by strains of zymomonas sp.

Strains of the bacteria Zymomonas sp. were studied for their ability to form higher alcohols. In a complex growth medium, six strains were shown to produce significant amounts of 1-propanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, pentanols, secondary hexyl-alcohols, and trace amounts of n-hexanol. When resting cells of these organisms were placed into a fermentation medium containing glucose and Tris-buffer, Z. mobilis 8938 produced increased levels of 1-butanol, and secondary hexyl-alcohols at concentrations of 13.5 mg/liter and 5.8 mg/liter, respectively. Another strain, Z. mobilis subsp. mobilis B 806, stimulated the formation of 1-propanol and 1-butanol at concentrations of 14.9 mg/liter and 23.52 mg/liter, respectively. Amino acids or amino acid precursors were then added to the fermentation medium. The presence of threonine and α-ketobutyric acid stimulated Z. mobilis 8938 to produce 82.6 mg/liter secondary hexyl-alcohols and 8.0 mg/liter n-hexanol, respectively. Isoleucine and valine increased the production of 2-methyl-1-butanol (394.0 mg/liter) and 3-methyl-1-butanol (113.4 mg/liter), respectively, by Z. mobilis subsp. mobilis B 806. Glutamine enhanced the formation of 2-methyl-2-butanol production to concentrations 38.8 mg/liter in Zymomonas strain B 806. Additional experiments suggested that higher alcohol production could also be accomplished in the absence of glucose when cells were allowed to metabolize the precursors only. The effect of aromatic amino acids on phenol production was determined using resting cells of Zymomonas sp. The maximum yield of phenol (111.6 mg/liter) was found by Zymomonas strain 8938 in the presence of tyrosine. The addition of phenylalanine also stimulated this strain to form 71.4 mg/liter of phenol.     

Growth of Methanogenic Bacteria in Pure Culture with 2-Propanol and Other Alcohols as Hydrogen Donors

Two types of mesophilic, methanogenic bacteria were isolated in pure culture from anaerobic freshwater and marine mud with 2-propanol as the hydrogen donor. The freshwater strain (SK) was a Methanospirillum species, the marine, salt-requiring strain (CV), which had irregular coccoid cells, resembled Methanogenium sp. Stoichiometric measurements revealed formation of 1 mol of CH₄ by CO₂ reduction, with 4 mol of 2-propanol being converted to acetone. In addition to 2-propanol, the isolates used 2-butanol, H₂, or formate but not methanol or polyols. Acetate did not serve as an energy substrate but was necessary as a carbon source. Strain CV also oxidized ethanol or 1-propanol to acetate or propionate, respectively; growth on the latter alcohols was slower, but final cell densities were about threefold higher than on 2-propanol. Both strains grew well in defined, bicarbonate-buffered, sulfide-reduced media. For cultivation of strain CV, additions of biotin, vitamin B₁₂, and tungstate were necessary. The newly isolated strains are the first methanogens that were shown to grow in pure culture with alcohols other than methanol. Bioenergetic aspects of secondary and primary alcohol utilization by methanogens are discussed.     

Production of Methyl Ketones from Secondary Alcohols by Cell Suspensions of C(2) to C(4)n-Alkane-Grown Bacteria

Nineteen new C(2) to C(4)n-alkane-grown cultures were isolated from lake water from Warinanco Park, Linden, N.J., and from lake and soil samples from Bayway Refinery, Linden, N.J. Fifteen known liquid alkane-utilizing cultures were also found to be able to grow on C(2) to C(4)n-alkanes. Cell suspensions of these C(2) to C(4)n-alkane-grown bacteria oxidized 2-alcohols (2-propanol, 2-butanol, 2-pentanol, and 2-hexanol) to their corresponding methyl ketones. The product methyl ketones accumulated extracellularly. Cells grown on 1-propanol or 2-propanol oxidized both primary and secondary alcohols. In addition, the activity for production of methyl ketones from secondary alcohols was found in cells grown on either alkanes, alcohols, or alkylamines, indicating that the enzyme(s) responsible for this reaction is constitutive. The optimum conditions for in vivo methyl ketone formation from secondary alcohols were compared among selected strains: Brevibacterium sp. strain CRL56, Nocardia paraffinica ATCC 21198, and Pseudomonas fluorescens NRRL B-1244. The rates for the oxidation of secondary alcohols were linear for the first 3 h of incubation. Among secondary alcohols, 2-propanol and 2-butanol were oxidized at the highest rate. A pH around 8.0 to 9.0 was found to be the optimum for acetone or 2-butanone formation from 2-alcohols. The temperature optimum for the production of acetone or 2-butanone from 2-propanol or 2-butanol was rather high at 60 degrees C, indicating that the enzyme involved in the reaction is relatively thermally stable. Metal-chelating agents inhibit the production of methyl ketones, suggesting the involvement of a metal(s) in the oxidation of secondary alcohols. Secondary alcohol dehydrogenase activity was found in the cell-free soluble fraction; this activity requires a cofactor, specifically NAD. Propane monooxygenase activity was also found in the cell-free soluble fraction. It is a nonspecific enzyme catalyzing both terminal and subterminal oxidation of n-alkanes.     

Purification, separation, and characterization of two molecular forms of D-1-amino-2-propanol:NAD+ oxidoreductase activity from extracts of Escherichia coli K-12.

D-1-Amino-2-propanol:NAD+ oxidoreductase activity, which catalyzes the second step in a pathway wherein L-threonine is converted to D-1-amino-2-propanol via the intermediate formation of aminoacetone, has been purified 500-fold from Escherichia coli K-12. Although the enzyme catalyzes the oxidation of certain diols as well as 1-amino-2-propanol, it is completely specific for the D-isomer of the amino alcohol and for NAD+. Two molecular forms (designated Form L and Form S) of the oxidoreductase, both of which are catalytically active, have been separated by gel filtration on Sephadex G-200; apparently, Form L is converted to Form S by dissociation (Form L leads to Form S). Molecular weight determinations indicate that the two forms of the enzyme are different not only in size but also in shape; Form L apparently is an asymmetric tetramer of Form S. The two molecular species have similar catalytic properties. Both exhibit the same pH optimum of 8.6, have nearly identical apparent Km values for substrate and cosubstrate, are equally sensitive to inhibition by p-mercuribenzoate and N-ethylmaleimide, and show the same specificity for cosubstrate. Neither form of the enzyme has an absolute requirement for added thiol compounds or divalent metal ions.     

Studies on the effect of alcohols on the chiral discrimination mechanisms of amylose stationary phase on the enantioseparation of nebivolol by HPLC

The chiral recognition mechanism of amylose CSPs has been described by achieving the enantiomeric resolution of (+/-)-nebivolol on Chiralpak AD and Chiralpak AD-RH columns with methanol, ethanol, 1-propanol, 2-propanol, 1-butanol as mobile phases at different flow rates. The energies of interactions of methanol, ethanol, 1-propanol, 2-propanol and 1-butanol with both phases were calculated. The (+)-RRRS enantiomer eluted first when using methanol, ethanol and 1-propanol, while the elution order was reversed when using 2-propanol and 1-butanol as the mobile phases. It has been concluded that the reversal elution order observed was due in part to the chiral cavities on the amylose CSP which were responsible for the bondings of different magnitude between chiral stationary phase and enantiomers, which are influenced with the type of alcohol used as mobile phase on the conformation of the 3,5-dimethyl phenyl carbamate moiety on the pyranose ring system of the amylose.     

Alcohols enhance caerulein-induced zymogen activation in pancreatic acinar cells

Activation of zymogens within the pancreatic acinar cell is an early feature of acute pancreatitis. Supraphysiological concentrations of cholecystokinin (CCK) cause zymogen activation and pancreatitis. The effects of the CCK analog, caerulein, and alcohol on trypsin and chymotrypsin activation in isolated pancreatic acini were examined. Caerulein increased markers of zymogen activation in a time- and concentration-dependent manner. Notably, trypsin activity reached a peak value within 30 min, then diminished with time, whereas chymotrypsin activity increased with time. Ethanol (35 mM) sensitized the acinar cells to the effects of caerulein (10(-10) to 10(-7) M) on zymogen activation but had no effect alone. The effects of ethanol were concentration dependent. Alcohols with a chain length of >or=2 also sensitized the acinar cell to caerulein; the most potent was butanol. Branched alcohols (2-propanol and 2-butanol) were less potent than aliphatic alcohols (1-propanol and 1-butanol). The structure of an alcohol is related to its ability to sensitize acinar cells to the effects of caerulein on zymogen activation.     

Several new substrates for Desulfovibrio vulgaris strain Marburg and a spontaneous mutant from it

The ability of Desulfovibrio vulgaris strain Marburg (DSM 2119) to oxidize alcohols was surveyed in the presence and absence of hydrogen-scavenging anaerobes, Acetobacterium woodii and Methanospirillum hungatei. In the presence of sulfate, D. vulgaris grew not only on ethanol, 1-propanol, and 1-butanol, but also on isobutanol, 1-pentanol, ethyleneglycol, and 1,3-propanediol. Metabolism of these alcohols was simple oxidation to the corresponding acids, except with the last two substrates: ethyleneglycol was oxidized to glycolate plus acetate, 1,3-propanediol to 3-hydroxypropionate plus acetate. Experimental evidence was obtained, suggesting that 2-methoxyethanol was not utilized by all the cells of strain marburg, but by a spontaneous mutant. 2-Methoxyethanol was oxidized to methoxyacetate by the mutant. Co-culture of strain Marburg plus A. woodii grew on ethanol, 1-propanol, 1-butanol, and 1,3-propanediol in the absence of sulfate. Co-culture of strain Marburg plus M. hungatei grew on ethanol, 1-propanol, and 1-butanol, but not on ethyleneglycol and 1,3-propanediol, Co-culture of the mutant plus A. woodii or M. hungatei did not grow on 2-methoxyethanol.     

Biphasic effects of alcohols on the phase transition of poly(L-lysine) between alpha-helix and beta-sheet conformations.

Poly(L-lysine) exists as a random-coil at neutral pH, an alpha-helix at alkaline pH, and a beta-sheet when the alpha-helix poly(L-lysine) is heated. The present Fourier-transform infrared (FTIR) study showed that short-chain alcohols (methanol, ethanol, and 2-propanol) partially transformed alpha-helix poly(L-lysine) to beta-sheet when their concentrations were low. At higher concentrations, however, these alcohols reversed the reaction, and the alcohol-induced beta-sheet was transformed back to alpha-helix structure. The reversal occurred at 1.40 M methanol, 0.96 M ethanol, and 0.55 M 2-propanol. The alcohol effects on the secondary structure were further investigated by circular dichroism (CD) on the thermally induced beta-sheet poly(L-lysine). Methanol, ethanol, and 1-propanol, but not 1-butanol, shifted the negative mean-residue ellipticity at 217 nm of the beta-sheet poly(L-lysine) to the positive side at low concentrations of the alcohols and to the negative side at high concentrations. With 1-butanol, only the positive-side shift was observed. The positive-side shift at low concentrations of alcohols indicates enhancement of the hydrophobic interactions among the side chains of the polypeptide in the beta-sheet conformation. The negative-side shift indicates a partial transformation to alpha-helix. The shift from the positive to negative side occurred at 7.1 M methanol, 4.6 M ethanol, and 3.1 M 1-propanol. The alcohol concentrations for the beta-to-alpha transition were higher in the CD study than in the IR study.(ABSTRACT TRUNCATED AT 250 WORDS)