Stimulation of tarsal receptors of the blowfly by aliphatic aldehydes and ketones

Rejection of eight aldehydes, eight ketones, five secondary alcohols, and 3-pentanol has been studied in the blowfly Phormia regina Meigen. The data agree with results previously reported for normal alcohols and several series of glycols in showing a logarithmic increase in stimulating effect with increasing chain length. The order of increasing effectiveness among the different species of compounds thus far investigated is the following: polyglycols, diols, secondary alcohols, iso-alcohols, normal alcohols, ketones, iso-aldehydes, normal aldehydes. Curves relating the logarithms of threshold concentration to the logarithms of chain length for diols, alcohols, aldehydes, and ketones show inflections in the 3 to 6 carbon range. Above and below the region of inflection the curves are nearly rectilinear. The slopes for the upper limbs (smaller molecules) are of the order of -2; for the lower limbs, about -10. Comparisons of the threshold data with numerical values for molecular weights, molecular areas and volumes, oil-water distribution coefficients, activity coefficients, standard free energies, vapor pressures, boiling points, melting points, dipole moments, dielectric constants, and degree of association are discussed briefly, and it is concluded that none of the comparisons serves to bring the data from the several series and from the two portions of each series into a single homogeneous system. A qualitative comparison with water solubilities shows fewer discrepancies. It is suggested that the existence of a combination of aqueous and lipoid phases at the receptor surface would fit best with what is presently known about the relationship between chemical structure and stimulating effect in contact chemoreception. In this hypothesis the smaller and more highly water-soluble compounds are envisaged as gaining access to the receptors partly through the aqueous phase, the larger molecules predominantly through the lipoid phase.     

Bacterial Utilization of Ether Glycols

A soil bacterium capable of using oligo- and polyethylene glycols and ether alcohols as sole sources of carbon for aerobic growth was isolated. The effects of substituent groups added to the ether bonds on the acceptability of the compounds as substrates were studied. Mechanisms for the incorporation of two-carbon compounds were demonstrated by the observation that acetate, glyoxylate, ethylene glycol, and a number of the tricarboxylic acid cycle intermediates served as growth substrates in minimal media. The rate of oxidation of the short-chained ethylene glycols by adapted resting cells varied directly with increasing numbers of two-carbon units in the chains from one to four. The amount of oxygen consumed per carbon atom of oligo- and polyethylene glycols was 100% of theoretical, but only 67% of theoretical for ethylene glycol. Resting cells oxidized oligo- and polyethylene glycols with 2 to 600 two-carbon units in the chains. Longer chained polyethylene glycols (up to 6,000) were oxidized at a very slow rate by these cells. Dehydrogenation of triethylene glycol by adapted cells was observed, coupling the reaction with methylene blue reduction.     

Regioselective synthesis of ethoxylated glycoside esters using beta-glucosidase in supersaturated solutions and lipases in organic solvents

Three ethoxylated glycosides, tetraethylene glycol beta-D-glucoside, tetraethylene glycol beta-D-xyloside, and methoxy triethyleneglycol beta-D-glucoside, were prepared via almond beta-glucoside-catalyzed (trans)glycosylation carried out in supersaturated solutions of glucose or p-nitrophenyl beta-D-xyloside and the respective polyethylene glycols. The products were isolated and further modified by enzymatic esterification with Candida antarctica and Mucor miehei lipases. The latter enzyme showed a much greater selectivity for the primary hydroxyl group on the polyethylene glycol chain of the glucoside substrate, thus enabling us to obtain exclusively the corresponding monoester, omega-O-oleoyl tetraethylene glycol beta-D-glucoside. Novozyme was used for the preparative synthesis of two other monoesters, 6-O-oleoyl (methoxy triethyleneglycol) beta-D-glucoside and omega-O-oleoyl tetraethylene glycol beta-D-xyloside. Two diesters, di-oleoyl tetraethylene glycol beta-D-glucoside and tetraethylene-bis(6-0-oleoyl glucoside) were also synthesized in good yields using this lipase. Copyright 1998 John Wiley & Sons, Inc.     

Enzymatic transformations in supersaturated substrate solutions: I. A general study with glycosidases

The results of an initial study of enzymatic catalysis in metastable supersaturated solutions of carbohydrates are presented. It has been shown that such solutions, formed in the presence of small amounts of water and alcohol as plasticizers, are sufficiently stable under ambient conditions to enable enzymatic transformations of substrates. A partial phase diagram for a system consisting of glucose, water, and (poly)ethylene glycol was constructed to identify the regions which are most suitable for biotransformations. It was confirmed that the glass transition in this system occurred below the reaction temperature at any given composition of the constituent components. Several glycosidases were found to be catalytically active in this medium and the activity of beta-glucosidase from almond was determined at several compositions of the reaction mixture and related to the corresponding regions of the phase diagram. The synthetic utility of the system was illustrated by glucosylation of several alpha,omega-alkyldiols, short-chain polyethylene glycols, and hydroxyalkyl and glyceryl monoacrylates.     

Modelling Studies of Crystalline PEEK

Abstract

The x-ray diffraction spectrum of the engineering thermoplastic poly (aryl-ether-ether-ketone), commonly known as PEEK, has been reported in the literature. The unit cell dimensions are consistent with two aryl units per unit cell, while the chemical repeat has three, suggesting that there is not a strict lateral register between chains. The polymer chain packing of crystalline PEEK has been investigated using lattice energy calculations and it is concluded that lateral chain ordering effects are rather unimportant in determining the crystal structure. The crystallographic equivalence of ether and ketone linkages arises due to essentially random chain stacking.     

Analysis of the catalytic domain of the lysin of the lactococcal bacteriophage Tuc2009 by chimeric gene assembling

Abstract Dye-linked alcohol dehydrogenase from Rhodopseudomonas acidophila strain M402, able to oxidize polyethylene glycols, was purified to homogeneity. The monomeric enzyme, having a molecular mass of 72 kDa, contains one PQQ and one haem c per enzyme molecule. In other respects also, the enzyme is very similar to the type I quinohaemoprotein alcohol dehydrogenases known to occur in Comamonas testosteroni, Comamonas acidovorans , and Pseudomonas putida species. However, dissimilarities exist with respect to the isoelectric points and the substrate specificities. On reinvestigating the substrate specificity of the C. testosteroni enzyme, it also appeared to exhibit good activity towards polyethylene glycols. Based on what has been reported for the polyethylene glycol-oxidizing alcohol dehydrogenase of Sphingomonas macrogoltabidus , this enzyme is quite different from that of R. acidophila . Keywords: Polyethylene glycol dehydrogenase activity; Alcohol dehydrogenase; PQQ; Haem c ; Rhodopseudomonas acidophila     

Availability of Energy in Ester and Ether Derivatives of Glycols by Growing Chicks

Biological availability of 33 esters, 17 ethers and 2 acetals of ethanediol, 1,2-propanediol, 1,3-butanediol and 1,4-butanediol was compared by mini-test with chicks. Chicks can utilize esters of ethanediol, 1,2-propanediol and 1,3-butanediol with acetic acid and fatty acids of carbon chain length from 5 to 12 with more improved palatability than that of free acids, while availability of esters of these glycols with propionic and butyric acids was low. Esters of 1,4-butanediol and ether derivatives of these glycols was not available, except ethyl ether of di-ethanediol which was partially available. Acetacetal of ethanediol was partially available but n-butyracetal was not.     

An analysis of the relationship between solubility and stimulating effect in tarsal chemoreception

The rejection thresholds of the blowfly Phormia regina Meigen for a selected series of substituted aliphatic hydrocarbons have been determined and an analysis made of the effect on stimulation of increasing the number of like substitutions from one to two, of the interaction of different types of substituent, and of the position of the substituent in the molecule. The order of stimulating efficiency (reciprocal of rejection threshold) of the functional groups which have been studied is: Br > Cl ? CH₃ ? CHO > C=O > OH. There is a consistent decrease in stimulating effect following the introduction of a second hydroxyl group. The introduction of a second C=O has little effect. Introduction of a second halogen is generally followed by a decrease in threshold. Two different species of functional group, one of which tends to increase water solubility and the other to decrease it, tend to counter-balance each other. A single oxygen-containing functional group on the end of the molecule or two of these groups which are terminal reduce the stimulating effect less than when one or more of such groups are subterminal or located elsewhere within the molecule. Branching of the carbon chain decreases effectiveness. Sulfur and oxygen linkages also decrease effectiveness. In general, the length of the free alkyl group largely determines the stimulating effectiveness. Its power is modified to varying degrees by the nature of the attached polar groups. Of all chemical properties examined, solubility alone agrees consistently with the foregoing data. Threshold varies directly with the molar solubility of the compounds in water. The fact that the threshold values for individual compounds are frequently different from those which would be expected solely on the basis of the correlation between threshold and solubility in water suggests that other factors are also concerned in stimulation. These have not yet been identified.     

Long-chain triazolyl acids as inhibitors of osteoclastogenesis

Saturated fatty acids (e.g., palmitic acid) are known to moderately inhibit the development of osteoclasts in vitro. In pursuit of more effective inhibitors of osteoclastogenesis we explored two new classes of palmitic acid analogues containing either an ether or triazolyl group at various positions along the chain. The compounds were evaluated for their ability to inhibit the formation of osteoclasts in primary mouse bone marrow cultures. The oxyacids were generally prepared by condensation of the appropriate alkyl halides and diols, followed by Jones oxidation. The triazolyl acids were prepared by copper-catalysed click chemistry between alkyl azides and acetylenic acids, or with the appropriately-protected azides and alkynes, followed by deprotection and oxidation. The oxyacids were little more effective than palmitic acid, but the triazolyl analogues were much more effective osteoclastogenesis inhibitors, especially when the triazole was distant from the acid unit.     

Epoxide hydrolase activity of Chryseomonas luteola for the asymmetric hydrolysis of aliphatic mono-substituted epoxides

Asymmetric hydrolysis of a homologous range of straight chain 1,2-epoxyalkanes was achieved using whole cells of Chryseomonas luteola. Depending on the chain length, hydrolyses of the racemic epoxides afforded optically active epoxides and diols with varying degrees of optical purity. In the case of 1,2-epoxyoctane, the enantiomeric excess of the remaining (S)-epoxide and formed (R)-diol was excellent (ees > 98% and eep = 86%). This is the first report of a bacterial epoxide hydrolase with such unusual enantioselectivity for terminal mono-substituted epoxides bearing no directing group on the chiral C-2 carbon. Benzyl glycidyl ether and the 2,2-disubstituted epoxide, 2-methyl-1,2-epoxyheptane, were hydrolysed, but no enantioselectivity was observed. © Rapid Science Ltd. 1998     

Decrease in intestinal permeability to polyethylene glycol 1000 during development in the pig

Changes in intestinal permeability during postnatal development in the pig were investigated by using different-sized polyethylene glycols in the Mr 766-1338 range (polyethylene glycol 1000) as permeability probes. Pigs of varying age, newborn (Oh), 36-45 h old and 22-28 days old, were gavage fed polyethylene glycol 1000 together with the macromolecular markers bovine serum albumin, ovalbumin or FITC-labelled dextran 70,000. The 4-h blood serum concentrations of the different markers were determined and taken as an estimate of their intestinal transmission. In the newborn pigs, high serum levels of polyethylene glycols were obtained, concomitant with high serum levels of bovine serum albumin and FITC-dextran. After intestinal macromolecular closure in the 36-45 h-old pigs, lower serum polyethylene glycol levels were found, especially of those with a Mr greater than 1100 Da. In the 22-28 days-old pigs, polyethylene glycol levels were reduced to one-tenth or less of those in the 36-45 h-old pigs, with the levels decreasing markedly with increasing molecular size. These results show that there is a correlation between the intestinal permeability of polyethylene glycols, especially those larger than 1100, and macromolecules in the newborn pig around intestinal closure, suggesting that such polyethylene glycols traverse the gut by the macromolecular route. During later development, further intestinal maturation results in a markedly reduced permeability to polyethylene glycol 1000.     

Cross-linked glucose isomerase crystals as a liquid chromatographic separation material

Cross-linked crystals of glucose isomerase (CLGI) were characterized as a liquid chromatographic separation material. The experiments were done with crystals having an average diameter of 83 μm. Porosity (epsilon(p)) and pore size distribution of the CLGI crystals were measured with size exclusion chromatography using D(2)O and polyethylene glycols as probes. CLGI material was capable of separating <1000 g/mol polyethylene glycols. Fifty two percent (epsilon(p) = 0.47) of the total crystal volume was in pores. Pore size measurement showed that CLGI crystals were microporous material, having an average apparent pore diameter of 29 +/- 0.08 ?. CLGI material separated n-alcohols C(1) to C(8) based on the hydrophobic interaction between the protein material and the carbon chain of the alcohols. Height equivalent to a theoretical plate (HETP, in millimeters) ranged from 1.6 to 0.89 for the C(1) to C(7) n-alcohol series. Despite the large crystal size, CLGI as a chirally active phase effectively separated D- and L-arabitol (R(s) = 0.58) and showed potential for chiral separation of amino acids.     

Precipitation of collagens by polyethylene glycols

Types I, II, and III collagens are readily precipitated at neutral pH by polyethylene glycols (PEG). As the molecular weight fraction of the polyethylene glycols increases, they become more effective as precipitants on a weight basis. The amount of PEG required for precipitation depends on the pH, the ionic strength, and the nature of the buffer or salts present. In tissue culture media, low concentrations of collagens and procollagens may be quantitatively precipitated and readily collected by low-speed centrifugation. Polyethylene glycol precipitation can be used to obtain collagens and procollagens from tissue culture media at either analytical or preparative scale, and since the polyethylene glycols do not bind to collagens, the precipitates may be further analyzed directly by chromatographic or electrophoretic methods.     

Lipase-catalyzed polycondensations: effect of substrates and solvent on chain formation,dispersity, and end-group structure

The effects of substrates and solvent on polymer formation, number-average molecular weight (M(n)), polydispersity, and end-group structure for lipase-catalyzed polycondensations were investigated. Diphenyl ether was found to be the preferred solvent for the polyesterification of adipic acid and 1,8-octanediol giving a M(n) of 28 500 (48 h, 70 degrees C). The effect of varying the alkylene chain length of diols and diacids on the molecular weight distribution and the polymer end-group structure was assessed. A series of diacids (succinic, glutaric, adipic, and sebacic acid) and diols (1,4-butanediol, 1,6-hexanediol, and 1,8-octanediol) were polymerized in solution and in bulk. It was found that reactions involving monomers having longer alkylene chain lengths of diacids (sebacic and adipic acid) and diols (1,8-octanediol and 1,6-hexanediol) give a higher reactivity than reactions of shorter chain-length diacids (succinic and glutaric acid) and 1,4-butanediol. The bulk lipase-catalyzed condensation reactions were feasible, but the use of diphenyl ether gave higher M(n) values (42,400 g/mol in 3 days at 70 degrees C). The polydispersity varied little over the conditions studied giving values 相似文献   

Hemoglobin precipitation by polyethylene glycols leads to underestimation of membrane pore sizes

The size of pores formed in the plasma membrane by various substances is frequently determined using polyethylene glycols as osmotic protectants. In this work, we have found that the size of pores formed by saponin in the red blood cell membrane determined by hemolysis versus molecular weight of polyethylene glycol was different to that estimated by light dispersion of cell suspensions. After complete swelling of cells induced by saponin in semiisotonic salt media containing 150 mOsm PEG-4000 or PEG-3000, a significant increase in the light absorbance at 640 nm was developed resulting from the formation of hemoglobin precipitates. Easily sedimenting aggregates were also formed when the supernatant of lysed cells was added to the equiosmotic solutions of polyethylene glycols with molecular weight higher than 1000. We suggest that the real size of large pores could be underestimated due to the phenomenon of hemoglobin precipitation by polyethylene glycols.     

Degradation of alkylphenol ethoxylates by Pseudomonas sp. strain TR01.

An alkylphenol ethoxylate-degrading bacterium was isolated from activated sludge of a municipal sewage treatment plant by enrichment culture. This organism was found to belong to the genus Pseudomonas; since no corresponding species was identified, we designated it as Pseudomonas sp. strain TR01. This strain had an optimal temperature and pH of 30 degrees C and 7, respectively, for both growth and the degradation of Triton N-101 (a nonylphenol ethoxylate in which the average number of ethylene oxide [EO] units is 9.5). The strain was unable to mineralize Triton N-101 but was able to degrade its EO chain exclusively. The resulting dominant intermediate was identified by normal-phase high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry as a nonylphenol ethoxylate with 2 mol of EO units. A carboxylated metabolite, [(nonylphenoxy)ethoxy]acetic acid, was detected by gas chromatography-mass spectrometry. This bacterium also metabolized alcohol ethoxylates with various numbers of EO units but not polyethylene glycols whatever their degree of polymerization. By oxygen consumption assay, the alkyl group or arene corresponding to the hydrophobic part of alcohol ethoxylates or alkylphenol ethoxylates was shown to contribute to the induction of the metabolic system of the EO chain of Triton N-101, instead of the EO chain itself, which corresponds to its hydrophilic part. Thus, the isolated pseudomonad bacterium has unique substrate assimilability: it metabolizes the EO chain only when the chain linked to bulky hydrophobic groups.     

Olfactory responses of blowflies to aliphatic aldehydes

The response of the blowfly Phormia regina to stimulation by aldehydes in the vapor phase has been studied by means of a specially designed olfactometer. The median rejection threshold and the maximum acceptance threshold were selected as criteria of response. For both acceptance and rejection the distribution of thresholds in the population is normal with respect to the logarithm of concentration. When thresholds are expressed as molar concentrations, the values decrease progressively as chain length is increased. There is no attraction beyond decanal and no rejection beyond dodecanal. When thresholds are expressed as activities, most members of the aldehyde series are approximately equally stimulating at rejection and equally stimulating at acceptance. The relationship is most exact over the middle range of chain lengths. There is a tendency for the terminal members to stimulate at higher activities. These relationships are in close agreement with those which were found earlier to apply to the normal aliphatic alcohols. The similarity between the relative actions of the members of the two series suggests that the relation of equal olfactory stimulation at equal thermodynamic activities by homologous aliphatic compounds at least for homologues of intermediate chain length may be of rather general application in olfaction.     

Preparation and properties of a novel class of polyhydroxyalkanoate copolymers

Polyhydroxyalkanoates (PHAs) are biodegradable aliphatic polyesters, known to be produced by many common microorganisms. Nodax is a recently introduced family of PHA copolymers comprising 3-hydroxybutyrate units and a relatively small amount of other medium chain length 3-hydroxyalkanoate (mcl-3HA) comonomers with side groups of at least three carbon units or more. There are several different grades of copolymers available, depending on the average molecular weight, average mcl-3HA content within the copolymer, and side group chain length of the chosen mcl-3HA unit. PHA copolymers with different mcl-3HA types and contents can be made either by bacterial fermentation or by chemical synthesis. The incorporation of mcl-3HA units into PHAs effectively lowers the crystallinity and T(m) in a manner similar to the effect of alpha-olefins in linear low-density polyethylene. The T(m) can be lowered well below the thermal decomposition temperature of PHAs to make this material much easier to process. The reduced crystallinity provides the ductility and toughness required for many practical applications. The mcl-3HA content regulates the T(m) and crystallinity of copolymer almost independently of the branch size, as long as more than three carbons are present in the side group. On the other hand, the side group chain length of the mcl-3HA has a profound effect on the flexibility of copolymer.     

Triester wax: a novel neutral lipid from the skin of the rhino mutant mouse.

A novel class of neutral lipids has been isolated from the skin of the rhino mutant mouse and has been characterized as a triester wax. The lipid, on saponification and transesterification, yielded fatty acids, omega-hydroxy fatty acids and 1,2-alkane diols. These products were identified by gas-liquid and thin-layer chromatography, infrared, nuclear magnetic resonance and mass spectroscopy, combined gas-liquid chromatography and mass spectrometry and chemical methods. Fatty acids were found to be predominantly of even chain length between C14 and C36 with highest concentration at C22 : 1. Hydroxy fatty acid methyl esters (trimethylsilyl ether derivatives) showed the presence of only three components in the relative abundance of 9: 70 : 21. The structure of the major component was established as 34-hydroxytetratricont-25-enoic acid and the other two components were characterized as 32-hydroxyditricont-23-enoic and 36-hydroxyhexatricont-27-enoic acids. In addition to these omega-9 unsaturates, other isomers having unsaturation at omega-7 and omega-8 were also present in small amounts. The 1,2-alkane diols were predominantly saturated in the range of C16-C24.     

Energetics of intrachain salt-linkage formation in collagen

The energy of formation of salt linkages between Arg or Lys with Asp or Glu in a polypeptide chain having the collagen fold have been estimated using the fully empirical energy minimization scheme AMBER. The polypeptide was considered both in an isolated and a hydrated triple helical state. The collagen fold associated with a one-bonded triple helical conformation allows intrachain salt linkages having stabilization energies of 60-100 kcal when the reacting residues are separated by no more than two intervening residues. The amino end of one side chain always approaches the carboxyl end of the other side chain, and simultaneously approaches the carbonyl oxygen of the intervening backbone residue. The salt linkage conformation and the backbone conformation of the isolated collagen fold in vacuo are maintained when the molecules are in a hydrated triple helix. These results are compatible with a fold-forming role for salt linkages, especially in proline poor regions, during collagen polypeptide synthesis, and with the persistence of intrachain salt linkages throughout molecular and fibril assembly.