Novel linear poly(NIPA‐co‐CL) copolymers have been synthesized by radical copolymerization of N‐isopropylacrylamide (NIPA) and 2‐methylene‐1,3‐dioxepane (MDO). The structure of copolymers was confirmed by 1H NMR and IR spectroscopy. Cross‐linked poly(NIPA‐co‐CL) hydrogels have also been prepared in toluene using N,N′‐methylenebisacrylamide as cross‐linking agent. The hydrogels thus obtained exhibit good temperature response and are biodegradable in the presence of proteinase K.
Temperature influence on the enzymatic degradation by proteinase K of poly(NIPA‐co‐CL) hydrogel (G‐60). 相似文献
In previous work, purification procedures and zymogram analysis conducted with supernatants of crude extracts from aerobic
mycelium of the YR-1 strain of Mucor circinelloides isolated from petroleum-contaminated soils indicated the existence of only one soluble alcohol oxidase (sAO) activity. In
the present work enzymatic activity of alcohol oxidase (AO) was also detected in the mixed membrane fraction (MMF) of a high-speed
centrifugation procedure after drastic ballistic cellular homogenization to break the mycelium from strain YR-1. When mycelial
cells were gently broken by freezing the mycelium with liquid nitrogen, smashing in a mortar, and submitting the samples to
an isopycnic sucrose gradients (10–60% sucrose), AO activity was detected in particular and discrete fractions of the gradient,
showing specific density values quite different from the density of peroxisomes. The results suggest that there could be a
different intracellular pattern of distribution of the microsomal fraction in aerobically grown mycelium depending on the
carbon source used in the culture media, including alcohols and hydrocarbons, but not in glucose. In working with particulate
fractions, we found two AO activities: a new membrane alcohol oxidase (mAO) activity and the sAO. Both activities appear to
be located in the inner of the cells in specific compartments different from the peroxisomes, so mAO could be in the membrane
of these compartments and sAO in the lumen of the vesicles. We also assayed other enzymatic activities involved in hydrocarbon
biodegradation to establish its intracellular location and other enzymatic activities such as peroxidase to use them as intracellular
markers of different organelles. In the case of monooxygenase, the first enzymatic step in the hydrocarbon biodegradation
pathway, its location was in the same fractions where AOs were located, suggesting the existance of a specific organelle that
contains the enzymatic activities involved in hydrocarbon biodegradation. 相似文献
Different soluble NAD+-dependent alcohol dehydrogenase (ADH) isozymes were detected in cell-free homogenates from aerobically grown mycelia of YR-1
strain of Mucor circinelloides isolated from petroleumcontaminated soil samples. Depending on the carbon source present in the growth media, multiple NAD+-dependent ADHs were detected when hexadecane or decane was used as the sole carbon source in the culture media. ADH activities
from aerobically or anaerobically grown mycelium or yeast cells, respectively, were detected when growth medium with glucose
added was the sole carbon source; the enzyme activity exhibited optimum pH for the oxidation of different alcohols (methanol,
ethanol, and hexadecanol) similar to that of the corresponding aldehyde (≈7.0). Zymogram analysis conducted with partially
purified fractions of extracts from aerobic mycelium or anaerobic yeast cells of the YR-1 strain grown in glucose as the sole
carbon source indicated the presence of a single NAD+-dependent ADH enzyme in each case, and the activity level was higher in the yeast cells. ADH enzyme from mycelium grown in
different carbon sources showed high activity using ethanol as substrate, although higher activity was displayed when the
cells were grown in hexadecane as the sole carbon source. Zymogram analysis with these extracts showed that this particular
strain of M. circinelloides has four different isozymes with ADH activity and, interestingly, one of them, ADH4, was identified also as phenanthrene-diol-dehydrogenase,
an enzyme that possibly participates in the aromatic hydrocarbon biodegradation pathway. 相似文献
To determine if compounds added during trichloroethylene (TCE) degradation could reduce the loss of enzyme activity or increase
enzyme recovery, different compounds serving as energy and carbon sources, pH buffers, or free radical scavengers were tested.
Formate and formic acid (reducing power and a carbon source), as well as ascorbic acid and citric acid (free radical scavengers)
were added during TCE degradation at a concentration of 2 mM. A saturated solution of calcium carbonate was also tested to
address pH concerns. In the presence of formate and methane, only calcium carbonate and formic acid had a beneficial effect
on enzyme recovery. The calcium carbonate and formic acid both reduced the loss of enzyme activity and resulted in the highest
levels of enzyme activity after recovery. 相似文献
Transient state swelling behavior and swelling kinetics of novel stimuli-responsive polyglycerol hydrogels were studied at 293, 310 and 333 K. Depending on temperature, Fickian or anomalous diffusion behavior was observed. Mechanical properties of the hydrogels in the swollen and dry states were investigated and the average molecular weight between crosslinks was calculated. To assess the potential for biodegradation of hydrogels, initial swelling behavior in phosphate buffered saline (PBS) solution and mass loss profiles as a function of degradation time were investigated over a period of 30 days. All swelling behavior, mechanical properties and degradations were clearly affected by the degree of cross-linking. The hydrophilicity and biodegradability of polyglycerol hydrogels make them suitable for pharmaceutical, biomedical and biotechnological applications. They could potentially serve as a substitute for common fossil-based hydrogels such as poly(ethylene glycol) and poly(vinyl alcohol) hydrogels. 相似文献
The radiation-induced polymerization of ethyl vinyl ether was studied in n-pentane and neopentane solutions under super-dry conditions. The free ion yields of these solvents are reported to be 0.16 and 1.0, respectively. The rate of polymerization in neopentane was about twice as fast as in n-pentane. The dose-rate dependence of the rate of polymerization was found to be nearly 0.50 in both solutions. It seems clear that the free solvent ions do, indeed contribute to the initiation. Regenerative chain transfer to monomer played a more important role in n-pentane than in neopentane as revealed by the molecular weight of the polymers. 相似文献
Abstract On behalf of the Umweltbundesamt the Fraunhofer Gesellschaft has developed a software system (SAR-system) comprising more than 90 estimation models for endpoints relevant in environmental risk assessment. These estimation models are based on the approach of quantitative structure-activity relationships (QSAR). All models were checked for their validity and application range. In the last months the Umweltbundesamt started to test the applicability of some models concerning the endpoints fish acute toxicity, daphnia acute toxicity and ready (i.e., ultimate) biodegradability in the daily routine of the notification procedure. For testing these models the corresponding confidential data given in the dossiers of substances notified 1993 in Germany, were used. We were able to make calculations for 36% of the notified substances. For the remaining 64% of the chemicals it was impossible to accomplish SAR estimations due to several reasons, e.g., ionic structure of the compounds. Different results for the applicability of the mentioned endpoints are obtained. The predictions of the fish and Daphnia toxicity are in sufficient agreement with the experimental results, in case of the fish toxicity we receive 58% agreement, for the Daphnia toxicity 56% The corresponding values which were obtained in the US EPA/E.C. Joint Project on the evaluation of (quantitative) structure activity relationships were 82.3% and 70.9% About 300 different models were used for the calculations of these endpoints within the framework of the EPA/EC project. The SAR-system presented here contains 8 models for estimating the fish toxicity and 6 models for the Daphnia toxicity. For the prediction of the biodegradability the results obtained with the SAR-system are rather poor and have to be improved. Meanwhile the SAR-system is commercially available and can be ordered at the Fraunhofer Institute for Environmental Chemistry and Ecotoxicology, Schmallenberg (Germany). 相似文献
Abstract The behaviour of the three phenoxyacetic acid herbicides 2,4-D, 2,4,5-T and MCPA during underground passage and bankfiltration was tested in a model system consisting of laboratory filter columns filled with natural underground materials. Different redox environments were reproduced by operating the filters with natural aerobic and anaerobic groundwater. In the presence of oxygen, biodegradation of the three herbicides started after a lag phase. Under sulfate reducing conditions, no degradation could be observed. To assess the factors that may influence microbial degradation in the anaerobic environment, the concentration of herbicides, the time and the nutrient content were varied, but this did not increase degradation. The maximum retention of the herbicides in the filters was 30%, mainly due to adsorption to the filter material. 相似文献
We have used fluorescence spectroscopy to study photoinduced biodegradation of ortho-cresol, para-cresol and mixture of them
in water when excited by different UV radiation sources. We show that the efficiency of photolysis for both the individual
isomers and the mixture of cresols is higher for excitation by radiation at λ ∼ 222 nm. Pre-irradiation of aqueous cresol
solutions slows down subsequent biodegradation. Using a combination of UV irradiation and the strain Penicillium tardum H-2
for utilization of the cresol mixture led to complete degradation of para-cresol and partial degradation of ortho-cresol.
Spectral and chromatographic study of the qualitative composition of the metabolites formed during biodegradation of para-cresol
showed that preparatory metabolism of such compounds occurs both through oxidation of the methyl group with formation of 4-hydroxybenzoic
acid and through hydroxylation with formation of 4-methylcatechol.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 250–255, March–April, 2008. 相似文献