Microwave driven wood liquefaction with glycols

Wood liquefaction with glycols using p-toluenesulfonic acid as the catalyst was carried out under microwave heating. With rapid heating and temperatures in the 190–210 °C range complete liquefaction was achieved in 7 min. Liquefaction efficiency was dependent on the choice of glycol. Simple glycols such as ethylene glycol and propylene glycol were more effective than higher analogues. The use of glycerol in mixtures with glycols showed a synergistic effect. Size exclusion chromatography was used to follow the gradual emergence of liquefaction products in solution as well as the recondensation products that start forming early in the reaction and precipitate from solution when molar masses of approx. 1 × 10⁴ g/mol are reached.     

Interaction of substrates and their analogs with adenosylcobalamine-dependent glycerol dehydratase]

The interaction of AdoCbl-dependent glycerol dehydratase with the substrates (glycerol, 1,2-propandiol, ethylene glycol) and their analogs (aliphatic diols) was studied kinetically. It was found that all the diols tested are competitive inhibitors of the enzyme with respect to substrates. The arrangement of hydroxyl groups in the molecule, the length of the carbohydrate chain and the nature of the substituent at the C-3 atom are essential for the binding of diol in the active center. The ternary enzyme-AdoCbl-substrate (analog) complexes are subjected to specific inactivation at a rate, which depends on the chemical structure of the substrate (analog). The constants for inactivation and dissociation of the ternary complexes were determined. It was shown that in contrast to the double complexes (enzyme-AdoCbl), the inactivation of the ternary complexes does not depend on oxygen. Some aspects of the mechanism of specific inactivation of glycerol dehydratase are discussed.     

The stimulating effect of glycols and their polymers on the tarsal receptors of blowflies

The rejection thresholds of Phormia regina Meigen for twenty-four glycols have been determined. A definite relationship between the concentration of the test material and the distribution of thresholds has been noted regularly in samples of flies selected at random from a population of known age which had been reared under standard conditions. The scattering of thresholds is normal with respect to the logarithm of concentration. Recalculation of the data of other workers reveals the same sort of relationship with other species of insects and the minnow Phoxinus. The underlying reason for the phenomenon is not known. The glycols in common with other series of homologous alipbatic compounds are rejected at logarithmically decreasing concentrations as the chain length is increased. In general the straight chain diols are more stimulating than the corresponding polyethylene and polypropylene glycols. This difference is related in some manner to the presence of ether linkages in the latter. Polypropylene glycols, with chains of three carbon atoms between the ether linkages are more stimulating than polyethylene glycols, where the spacing is -O-C-C-O-. Unipolymers are more stimulating than mixtures of homologues with the same average molecular weights. Polyethylene glycol 1540 is the largest molecule of measured molecular weight known to stimulate chemoreceptors. The introduction of a second terminal hydroxyl group into the straight hydrocarbon chain reduces the stimulating effect. Alcohols corresponding to the first three diols average about four times as stimulating as the latter while those corresponding to the higher diols average more than one hundred times as stimulating.     

On the mechanism of non-electrolyte permeation through lipid bilayers and through biomembranes

The temperature effects on the permeation of polyhydroxy alcohols through the lipid bilayers of liposomes with a great variety in chemical composition were studied. Although important differences in the permeability of the various lipid bilayers were observed, Arrhenius plots demonstrated that the activation energy is independent of the degree of unsaturation or the presence of cholesterol in the paraffin barriers. The activation energies found for the penetration of a bilayer with a liquid paraffin core are 14.3 kcal for glycol, 19.4 kcal for glycerol, and 20.8 kcal for erythritol. These values are in agreement with the energies that can be expected for complete dehydration of the permeant molecules. The idea that the activation energy is determined by the number of hydrogen bonds with water is supported by the finding that a series of different diols did demonstrate practically identical activation energies. Studies on a number of biological membranes demonstrated the same activation energies for the penetration of glycerol and erythritol as found in the experiments with liposomes. These facts support the view that both the lipid bilayers and the biological membranes are penetrated by single fully dehydrated molecules.     

Chemical modification and cross-linking of proteins by impurities in glycerol.

Impurities in glycerol are shown to cross-link bovine pancreatic ribonuclease and collagen and to eliminate the Soret band of the spectrum of myoglobin. Ethylene glycol behaves similarly. Aldehyde and peroxide are detected in impure glycerol. Glycerol may be purified by treatment with sodium borohydride, deionization and distillation in vacuo at as low a temperature as possible. Exposure of purified glycerol to air results in the reappearance of impurities.     

In vitro evaluation of ram sperm frozen with glycerol, ethylene glycol or acetamide

The aim was to assess the in vitro effect of glycerol, ethylene glycol or acetamide on frozen-thawed ram spermatozoa. Aliquots of each sixteen ejaculates from four rams of the Morada Nova breed were diluted in Tris-egg yolk with glycerol (5%), ethylene glycol (3% or 5%) or acetamide (3% or 5%) and frozen at -196°C. After thawing, progressive sperm motility was greater (P<0.05) in cryopreservation with glycerol 5% and ethylene glycol (3% or 5%) than with acetamide (3% or 5%). Acrosome integrity was greater (P<0.05) with ethylene glycol 5% than acetamide (3% or 5%). The percentage of sperm without oxidative stress was greater (P<0.05) with ethylene glycol (3% or 5%) than with acetamide (3% or 5%). Plasma membrane integrity was greater with glycerol 5% (P<0.05) than with the other cryoprotectants. Thus, it is concluded that glycerol 5% and ethylene glycol 3% or 5% protect ram sperm against the harmful effects of freezing and that glycerol 5% offers greater protection to sperm plasma membrane.     

Application of a high-level peracetic acid disinfection protocol to re-process antibiotic disinfected skin allografts

Skin allografts, derived from cadaveric donors, are widely used for the treatment of burns and ulcers. Prior to use in clinical situations, these allografts are disinfected using a cocktail of antibiotics and then cryopreserved. Unfortunately, this antibiotic disinfection procedure fails to decontaminate a significant proportion and these contaminated grafts can not be used clinically. We have investigated whether it is possible to apply a second, more potent disinfection procedure to these contaminated grafts and effectively to re-process them for clinical use. Cadaveric skin grafts, treated with antibiotics and cryopreserved, were thawed and a peracetic acid (PAA) disinfection protocol applied. The grafts were then preserved in a high concentration of glycerol or propylene glycol, and properties thought to be essential for successful clinical performance assessed. The cytotoxicity of the grafts was assessed using both extract and contact assays; damage to the skin collagen was assessed using a collagenase susceptibility assay and the capacity of the grafts to elicit an inflammatory response in vitro was assessed by quantifying the production of the pro-inflammatory cytokine TNF-alpha by human peripheral blood mononuclear phagocytes. PAA disinfection, in conjunction with either glycerol or propylene glycol preservation, did not render the grafts cytotoxic, pro-inflammatory, or increase their susceptibility to collagenase digestion. The rates of penetration of glycerol and propylene glycol into the re-processed skin were comparable to those of fresh skin. This study has demonstrated that PAA disinfection combined with immersion in high concentrations of either glycerol or propylene glycol was an effective method for re-processing contaminated skin allografts, and may justify their clinical use.     

The effect of glycols on the renaturation of soluble collagen

The effects of a number of related glycols and substituted glycols on the renaturation kinetics of acid-soluble calf-skin collagen have been investigated. Optical rotation recovery was monitored at a fixed temperature in the presence of perturbants and the initial rates of reaction were determined. The effects of perturbants on stability of the native protein are compared with their action in the renaturing systems. The relationship between initial recovery rates and fixed-time [alpha]-values is shown to be dependent upon the renaturation temperature. The influence of perturbant concentration on recovery rates is discussed in terms of present theories of the mechanism of collagen renaturation.     

Protectants used in the cryopreservation of microorganisms

The cryoprotective additives (CPAs) used in the frozen storage of microorganisms (viruses, bacteria, fungi, algae, and protozoa) include a variety of simple and more complex chemical compounds, but only a few of them have been used widely and with satisfactory results: these include dimethylsulfoxide (Me2SO), glycerol, blood serum or serum albumin, skimmed milk, peptone, yeast extract, saccharose, glucose, methanol, polyvinylpyrrolidone (PVP), sorbitol, and malt extract. Pairwise comparisons of the cryoprotective activity of the more common CPAs used in cryomicrobiology, based on published experimental reports, indicate that the most successful CPAs have been Me2SO, methanol, ethylene glycol, propylene glycol, and serum or serum albumin, while glycerol, polyethylene glycol, PVP, and sucrose are less successful, and other sugars, dextran, hydroxyethyl starch, sorbitol, and milk are the least effective. However, diols (as well as some other CPAs) are toxic for many microbes. Me2SO might be regarded as the most universally useful CPA, although certain other CPAs can sometimes yield better recoveries with particular organisms. The best CPA, or combination of CPAs, and the optimum concentration for a particular cryosensitive microorganism has to be determined empirically. This review aims to provide a summary of the main experimental findings with a wide range of additives and organisms. A brief discussion of mechanisms of CPA action is also included.     

Survival of vitrified sheep embryos in vitro and in vivo

The effects of the composition of vitrification media, the duration of exposure to the media and the stage of development were examined on the survival of vitrified Day-6 sheep embryos. Vitrification media that contained two cryoprotectants in equal molar concentrations were used. In Experiment 1, the effects of the types (glycerol + propylene glycol or glycerol + ethylene glycol) and concentrations (3.5 + 3.5 or 4.5 + 4.5 M) of cryoprotectants and the level of BSA supplementation (0.4 or 20%) were investigated in a 2 x 2 x 2 design. The embryos were exposed to vitrification media for 30 sec at 18 to 24 degrees C before vitrification. The in vitro survival rate was not affected by the level of BSA supplementation, but there was an interaction between the types and concentrations of cryoprotectants used (P<0.01). Embryos cryopreserved in mixtures of glycerol + propylene glycol survived better when the concentration of cryoprotectants was 3.5 M while the survival of embryos cryopreserved in mixtures of glycerol + ethylene glycol was higher at 4.5 M cryoprotectant concentration. In Experiments 2 and 3, the effect of the duration of exposure (15, 30, 60 or 120 sec) to vitrification media at 4 to 12 degrees C was investigated on the survival rate in vivo. Vitrification media contained 3.5 M glycerol + 3.5 M propylene glycol or 4.5 M glycerol + 4.5 M ethylene glycol in Experiments 2 and 3, respectively. The survival rate in vivo, increased when the duration of exposure to vitrification media was increased from 15 to 30 sec, but the viability declined when the duration of exposure was further increased to 60 (Experiment 3) or to 120 sec (Experiment 2). The effect of the stage of development was significant only in Experiment 1 (P = 0.032), but in all three experiments the rate of survival increased with advancing stages of development from late morulae to late blastocysts. The best result was achieved in Experiment 2, when embryos were exposed to a mixture of 3.5 M glycerol + 3.5 M propylene glycol for 30 or 60 sec. Under these conditions 52% (22 42 ) of rapidly cryopreserved sheep embryos developed into lambs. This result shows that a simple rapid procedure for the cryopreservation of sheep embryos can produce a survival rate comparable to that obtained using more complex traditional procedures.     

Effect of some permeating cryoprotectants on CASA motility results in cryopreserved bull spermatozoa

Computer-assisted sperm analyzers (CASA) have become the standard tool for evaluating sperm motility because they provide objective results for thousands of mammalian spermatozoa. Mammalian spermatozoa experience osmotic stress when the glycerol is added to the cells prior to freezing and removal from the cells after thawing. In order to minimize osmotic damage, cryoprotectants having lower molecular weights and greater membrane permeability than glycerol, were evaluated to determine their effectiveness for cryopreserving bull spermatozoa. The aim of this study was to compare the cryopreservation effects of low molecular weight cryoprotectants (ethylene glycol and methanol) to glycerol, on post-thaw CASA sperm parameters. Bull semen was diluted with tris-egg yolk extender containing 3% glycerol, 3, 2 and 1% ethylene glycol or 3, 2 and 1% methanol. Bull semen was frozen in 0.5 straws. Bull spermatozoa exhibited higher percentages (p<0.01) for total (Mot, 72.4%) and progressively (Prog, 29.5%) motilities when frozen in extender containing 3% glycerol compared to 3, 2 and 1% ethylene glycol or 3, 2 and 1% methanol. In conclusion, no advantages were found in using ethylene glycol or methanol to replace glycerol in bull semen freezing. Glycerol provided the best sperm characteristics for bull spermatozoa after freezing and thawing. The possibility of using ethylene glycol or methanol as permeating cryoprotectants for bull semen deserves further investigation, and these cryoprotectants should also be evaluated in extenders that contain disaccharides or cholesterol.     

Storage of Chinchilla lanigera Semen at 4°C for 24 or 72 h with Two Different Cryoprotectants

The objectives of this study were to: (a) test the functional activity of Chinchilla lanigera spermatozoa suspended in either glycerol or ethylene glycol, cooled to 4 degrees C, and stored for 24 or 72 h and (b) investigate, after these cooling periods, the effects of incubating sperm at 37 degrees C (for 4 h) upon sperm functional activity. The ejaculate was mixed with the cryoprotectant medium (at 1 M final concentration) and cooled to 4 degrees C. After warming, sperm motility, sperm viability, hypoosmotic swelling test results, and acrosomal integrity were significantly higher for samples containing ethylene glycol than for those in glycerol, stored for 24 or 72 h, and then assayed after 0 or 4 h incubation at 37 degrees C. A significant reduction of sperm motility and viability was detected only when the glycerol cryoprotectant agent was employed, compared to the fresh samples. These results clearly indicate that under our experimental conditions, ethylene glycol is a better protectant for sperm storage than glycerol.     

四种渗透性防冻剂在猕猴精子低温冷冻保存中对精子功能状态的影响

以冷冻精子的复苏运动度、荧光染料Hoechst 3 3 2 5 8检测的细胞膜完整率、异硫氰酸荧光素标记的花生凝集素 (FITC PNA)检测的顶体完整率作为精子功能状态的指标 ,对甘油、二甲亚砜、乙二醇和丙二醇 4种常用渗透性防冻剂在猕猴精子冷冻保存过程中的作用进行了比较。结果表明 :冷冻保存精子的复苏运动度 ,甘油 ( 4 7 3± 5 7% )和乙二醇 ( 4 4 8± 6 7% ) >二甲亚砜 ( 2 2 9± 0 9% ) >丙二醇 ( 0± 0 % ) ;细胞膜完整率 ,甘油 ( 5 4 8± 3 2 % )和乙二醇 ( 5 4 0± 6 7% ) >二甲亚砜 ( 3 7 5± 7 0 % ) >丙二醇 ( 2 8 3± 6 5 % ) ;顶体完整率 ,甘油 ( 82 2± 2 4 % )和乙二醇 ( 82 4± 2 4 % ) >二甲亚砜 ( 6 8 7± 5 7% )和丙二醇 ( 72 3±3 5 % ) (P <0 0 5 )。结果提示 :二甲亚砜和丙二醇 ,尤其是丙二醇并不适合猕猴精子的冷冻保存 ;而乙二醇具有和甘油相似的保护作用 ,是一种极具潜力的猕猴精子冷冻保存的渗透性防冻剂。     

Interaction of calf skin collagen with glycerol: linked function analysis

Glycerol stabilizes the triple-helical structure of solubilized calf skin collagen. The equilibrium melting temperature of the protein increased linearly from 38.0 degrees C in AS buffer (0.01 M NaOAc and 0.02 M NaCl, pH 4.0) to 43.0 degrees C in AS and 6 M glycerol buffer. To understand the thermodynamic basis of this effect on the equilibrium melting temperature and the glycerol inhibition of collagen self-association, the preferential interactions of native and denatured calf skin collagens in AS buffer containing 1.5, 3, and 4.5 M glycerol were measured with a precision densimeter. The results indicated that native collagen binds glycerol preferentially whereas denatured collagen neither binds nor repels glycerol. The preferential binding of glycerol by native collagen, when interpreted in terms of the three-component solution thermodynamics, suggests that the surface interaction of native collagen with glycerol is energetically more favorable than its interaction with water. By use of the Wyman linked function, the negative chemical potential change of collagen derived from its preferential binding of glycerol can account for both the glycerol stabilization of the triple-helical structure of collagen and the inhibition of in vitro self-association of monomers into fibrils.     

Incorporation of penetrating cryoprotectants in diluents for pellet-freezing ram spermatozoa

Glycerol may be toxic to frozen-thawed ram spermatozoa and reduce their fertilizing capacity. This study examined the cryoprotective effects of dimethyl sulphoxide (DMSO), ethylene glycol, glycerol and propanediol alone and in combinations with each other in Triscitrate-glucose diluents on the post-thaw motility and acrosome integrity of pellet-frozen ram spermatozoa. The 4 cryoprotectants were examined in diluents at 5 concentrations (0, 1.5, 3.0, 6.0, 12.0% v/v). Post-thaw motility of spermatozoa was higher in diluents containing ethylene glycol (1.5 to 6.0% v/v), glycerol (at all levels tested) and propanediol (1.5 and 3.0% v/v) than in diluents without cryoprotectant (P<0.001), but there was no effect of DMSO on post-thaw motility. Motility of spermatozoa was higher in diluents containing ethylene glycol or glycerol than DMSO or propanediol (P<0.001). In diluents containing the 4 cryoprotectants at 3 concentrations (1.5, 3.0, 6.0% v/v), better recovery of spermatozoa was found with the addition of 18.0 than 4.5% v/v egg yolk. Combinations of ethylene glycol and/or propanediol (0 to 6.0% v/v) with glycerol (0 to 6.0% v/v) in diluents were also examined. In the presence of glycerol at all levels tested, increasing levels of ethylene glycol and/or propanediol decreased motility and acrosome integrity of spermatozoa (P<0.001). We conclude that the compounds examined exert a cryoprotective effect on pellet-frozen ram spermatozoa, except for DMSO which had no effect. In this study, glycerol remained the single most effective cryoprotectant, and there was no enhancement of this cryoprotection by addition of the other compounds.     

Decrease of transport of some polyols in sickle cells

This paper reports the results of kinetic studies on the inward net-flux of small non-electrolytes (ethylene glycol, glycerol and erythritol) in sickle cells as compared to normal erythrocytes. Net transport rates were evaluated by turbidimetric measurements for ethylene glycol and glycerol and by hematocrit monitoring for erythritol. A 2-fold and 4-fold reduction in the permeability coefficient for ethylene glycol and glycerol, respectively, were found in sickle cells as compared to normal erythrocytes. In contrast, no significant changes in erythritol transport kinetics were observed. The dependence of glycerol permeability on temperature, pH and oxygenation is the same in both types of cells. A significant correlation was observed between glycerol permeability and cell density only for sickle cells. The results indicate that irreversible modifications of membrane proteins, responsible for the glycerol and ethylene glycol transport, do occur in sickle cells.     

An approach based on liquid chromatography/electrospray ionization-mass spectrometry to detect diol metabolites as biomarkers of exposure to styrene and 1,3-butadiene

Styrene and 1,3-butadiene are important intermediates used extensively in the plastics industry. They are metabolized mainly through cytochrome P450-mediated oxidation to the corresponding epoxides, which are subsequently converted to diols by epoxide hydrolase or through spontaneous hydration. The resulting styrene glycol and 3-butene-1,2-diol have been suggested as biomarkers of exposure to styrene and 1,3-butadiene, respectively. Unfortunately, poor ionization of the diols within electrospray mass spectrometers becomes an obstacle to the detection of the two diols by liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). We developed an LC/ESI-MS approach to analyze styrene glycol and 3-butene-1,2-diol by means of derivatization with 2-bromopyridine-5-boronic acid (BPBA), which not only dramatically increases the sensitivity of diol detection but also facilitates the identification of the diols. The analytical approach developed was simple, quick, and convincing without the need for complicated chemical derivatization. To evaluate the feasibility of BPBA as a derivatizing reagent of diols, we investigated the impact of diol configuration on the affinity of a selection of diols to BPBA using the established LC/ESI-MS approach. We found that both cis and trans diols can be derivatized by BPBA. In conclusion, BPBA may be used as a general derivatizing reagent for the detection of vicinal diols by LC/MS.     

Degradation of ethylene glycol and polyethylene glycols by methanogenic consortia.

Methanogenic enrichments capable of degrading polyethylene glycol and ethylene glycol were obtained from sewage sludge. Ethanol, acetate, methane, and (in the case of polyethylene glycols) ethylene glycol were detected as products. The sequence of product formation suggested that the ethylene oxide unit [HO-(CH2-CH2-O-)xH] was dismutated to acetate and ethanol; ethanol was subsequently oxidized to acetate by a syntrophic association that produced methane. The rates of degradation for ethylene, diethylene, and polyethylene glycol with molecular weights of 400, 1,000, and 20,000, respectively, were inversely related to the number of ethylene oxide monomers per molecule and ranged from 0.84 to 0.13 mM ethylene oxide units degraded per h. The enrichments were shown to best metabolize glycols close to the molecular weight of the substrate on which they were enriched. The anaerobic degradation of polyethylene glycol (molecular weight, 20,000) may be important in the light of the general resistance of polyethylene glycols to aerobic degradation.     

Partition of synaptic membranes in aqueous two-phase systems at subzero temperatures by using anti-freeze solvent

The freezing point of aqueous two-phase (liquid-liquid) systems containing water, dextran and poly(ethylene glycol) has been lowered by including glycerol. Biological membranes, obtained by fragmentation of a crude synaptosomal preparation from calf brain cortex, have been included in the two-phase systems. The effects of temperature and the concentration of glycerol on the partition of the membranes within the systems have been investigated. Considerable stabilisation of the membranes was noticed when they were partitioned at -10 degrees C compared with 0 degrees C. The influences of glycerol, ethylene glycol, N,N-dimethylformamide and tetrahydrofuran on the phase-forming properties of the systems and on enzyme activities are also presented. Possible use of the above systems for studies and separation of biological membranes are discussed.     

The ability of cryopreservatives to prevent motility loss and freeze-thaw damage to the acrosome of chicken spermatozoa

Proteolytic membrane digestion and motility were used to determine the effects of cryopreservatives and freezing on acrosomal damage and survival of chicken spermatozoa. None of the cryopreservatives, glycerol, DMSO, or ethylene glycol caused a decrease in proteolytic membrane digestion by the chicken spermatozoon before freezing. After rapid freezing, high levels (16 and 24%) of glycerol prevented significant freeze-thaw reductions in proteolytic digestion. High levels of ethylene glycol (16 and 24%) and DMSO (12 and 14%) significantly reduced the ability of frozen spermatozoa to completely digest the protein membrane. Motility after freezing was highest (63%) in 16% glycerol.Glycerol at high levels appeared to be the best cryopreservative under these conditions.