Kinetics of L-type pyruvate kinase (EC 2.7.1.40) catalysed reaction between phosphoenolpyruvate (PEP) and ADP was analysed under steady-state conditions and the interac- tion of both substrates with the enzyme was characterized proceeding from bi-substrate kinetic mechanism of this process. Cooperative regulation of the rate of this process by one of the substrates, PEP, was taken into consideration by using a sequential ligand binding model. It was found that two PEP molecules may bind with similar affinity with the tetrameric enzyme (3 0 mM), K = while the effectiveness of the binding of the next two substrate molecules is enhanced through cooperative interaction between the enzyme subunits, which decreases the dissociation constant of the enzyme-substrate complex approximately 10 times.
{"title":"Kinetic analysis of cooperativity of phosphorylated L-type pyruvate kinase","authors":"I. Faustova, J. Järv","doi":"10.3176/chem.2006.4.01","DOIUrl":"https://doi.org/10.3176/chem.2006.4.01","url":null,"abstract":"Kinetics of L-type pyruvate kinase (EC 2.7.1.40) catalysed reaction between phosphoenolpyruvate (PEP) and ADP was analysed under steady-state conditions and the interac- tion of both substrates with the enzyme was characterized proceeding from bi-substrate kinetic mechanism of this process. Cooperative regulation of the rate of this process by one of the substrates, PEP, was taken into consideration by using a sequential ligand binding model. It was found that two PEP molecules may bind with similar affinity with the tetrameric enzyme (3 0 mM), K = while the effectiveness of the binding of the next two substrate molecules is enhanced through cooperative interaction between the enzyme subunits, which decreases the dissociation constant of the enzyme-substrate complex approximately 10 times.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86954467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
U. Stirna, I. Sevastyanova, Maria Misane, U. Cabulis, I. Beverte
By transesterifying rapeseed oil with tr iethanolamine or glycerol, polyols with a hydroxyl number of 290-310 mg KOH/g were synthesized. Water-blown rigid polyurethane foams (PUFs) with an isocyanate index of 150-250 were obtained from rapeseed oil polyols. Studies on the effect of the concentration of potassium oleate, the cyclotrimerization catalyst of isocyanate groups, on the conversion degree of isocyanate groups were carried out using FTIR spectroscopy. The optimal physical and mechanical properties of the obtained PUFs were achieved at an isocyanate index of 150-200. Water-blown PUFs from rapeseed polyols, in contrast to water-blown PUFs from petrochemical polyols, are characterized by quite high hydrophobicity.
{"title":"Structure and properties of polyurethane foams obtained from rapeseed oil polyols","authors":"U. Stirna, I. Sevastyanova, Maria Misane, U. Cabulis, I. Beverte","doi":"10.3176/chem.2006.2.07","DOIUrl":"https://doi.org/10.3176/chem.2006.2.07","url":null,"abstract":"By transesterifying rapeseed oil with tr iethanolamine or glycerol, polyols with a hydroxyl number of 290-310 mg KOH/g were synthesized. Water-blown rigid polyurethane foams (PUFs) with an isocyanate index of 150-250 were obtained from rapeseed oil polyols. Studies on the effect of the concentration of potassium oleate, the cyclotrimerization catalyst of isocyanate groups, on the conversion degree of isocyanate groups were carried out using FTIR spectroscopy. The optimal physical and mechanical properties of the obtained PUFs were achieved at an isocyanate index of 150-200. Water-blown PUFs from rapeseed polyols, in contrast to water-blown PUFs from petrochemical polyols, are characterized by quite high hydrophobicity.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"146 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73550320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The structure formation in acid promoted polycondensation and particularly in alkaline post-treatment with urea was studied by ¹³C NMR spectroscopy in the three-step synthesis of urea- formaldehyde resins. Trishydroxymethyl urea was identified as the constituent of the mixture of hydroxylmethylated urea derivatives obtained in alkaline conditions. The formation of methylenes linked to secondary or tertiary amino groups occu rs only in acidic conditions by branching chains in the reaction with mono- and 1,3-bishydroxymethyl urea. Bishydroxymethyl groups do not take part in acid promoted polycondensation. The final structure of resins depends mostly on the migration of formaldehyde from bishydroxymethyl groups to urea with formation of mono- hydroxymethyl urea as the first preferred compound. A greater amount of oligomers with methylenes adjacent to secondary amino groups and containing singly bonded urea is a sign of a thorough heat treatment. A steady content of methylenes linked to tertiary amino groups is observed in heat treatment and ageing of resins.
{"title":"Structure formation in urea-formaldehyde resin synthesis","authors":"P. Christjanson, T. Pehk, K. Siimer","doi":"10.3176/chem.2006.4.04","DOIUrl":"https://doi.org/10.3176/chem.2006.4.04","url":null,"abstract":"The structure formation in acid promoted polycondensation and particularly in alkaline post-treatment with urea was studied by ¹³C NMR spectroscopy in the three-step synthesis of urea- formaldehyde resins. Trishydroxymethyl urea was identified as the constituent of the mixture of hydroxylmethylated urea derivatives obtained in alkaline conditions. The formation of methylenes linked to secondary or tertiary amino groups occu rs only in acidic conditions by branching chains in the reaction with mono- and 1,3-bishydroxymethyl urea. Bishydroxymethyl groups do not take part in acid promoted polycondensation. The final structure of resins depends mostly on the migration of formaldehyde from bishydroxymethyl groups to urea with formation of mono- hydroxymethyl urea as the first preferred compound. A greater amount of oligomers with methylenes adjacent to secondary amino groups and containing singly bonded urea is a sign of a thorough heat treatment. A steady content of methylenes linked to tertiary amino groups is observed in heat treatment and ageing of resins.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82984521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A method for the activation of a cellulose-based matrix resulting in obtaining active primary amino groups via a long spacer arm was developed. The method is based on coupling pentaethylenehexamine (PEHA) to the polymeric matrix through epoxy groups. It was shown that modification of cellulose with PEHA is a straightforward and convenient procedure that has the advantages of high coupling efficiency. The primary amino group density on the carrier surf ace can be easily adjusted by changing the content of epoxy groups in the matrix or by altering the amount of PEHA in the reaction mixture. The lectins Concanavalin A and Wheat Germ Agglutinin were employed as ligands for the immobilization onto the PEHA-activated carrier using glutaraldehyde. It was shown that the spacer arm affected ligand coupling kinetics as well as the chromatographic behaviour of the adsorbents obtained. Covalent immobilization of enzyme glucoamylase on PEHA-activated cellulose was done. It was found that covalent binding via glutaraldehyde offers satisfactorily stable and active preparations.
{"title":"Activation of cellulose-based carriers with pentaethylenehexamine ","authors":"J. Aniulyte, J. Bryjak, J. Liesienė","doi":"10.3176/chem.2006.2.02","DOIUrl":"https://doi.org/10.3176/chem.2006.2.02","url":null,"abstract":"A method for the activation of a cellulose-based matrix resulting in obtaining active primary amino groups via a long spacer arm was developed. The method is based on coupling pentaethylenehexamine (PEHA) to the polymeric matrix through epoxy groups. It was shown that modification of cellulose with PEHA is a straightforward and convenient procedure that has the advantages of high coupling efficiency. The primary amino group density on the carrier surf ace can be easily adjusted by changing the content of epoxy groups in the matrix or by altering the amount of PEHA in the reaction mixture. The lectins Concanavalin A and Wheat Germ Agglutinin were employed as ligands for the immobilization onto the PEHA-activated carrier using glutaraldehyde. It was shown that the spacer arm affected ligand coupling kinetics as well as the chromatographic behaviour of the adsorbents obtained. Covalent immobilization of enzyme glucoamylase on PEHA-activated cellulose was done. It was found that covalent binding via glutaraldehyde offers satisfactorily stable and active preparations.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"66 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88354920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The bating of pelts after using peracetic aci d for deliming was studied. It was established that the commonly used enzymes, which are active in alkaline media, acted weakly in such pelts: they did not remove scud and hair remnants from the grain of pelt satisfactorily. Enzyme preparations LITHUDAC L and Novo Bate WB, which are active in acid media, can be used for bating such pelts. These enzymes clean the grain of pelt well and do not affect the collagen of pelt markedly.
{"title":"Bating of pelts after deliming with peracetic acid","authors":"V. Valeika","doi":"10.3176/chem.2006.2.06","DOIUrl":"https://doi.org/10.3176/chem.2006.2.06","url":null,"abstract":"The bating of pelts after using peracetic aci d for deliming was studied. It was established that the commonly used enzymes, which are active in alkaline media, acted weakly in such pelts: they did not remove scud and hair remnants from the grain of pelt satisfactorily. Enzyme preparations LITHUDAC L and Novo Bate WB, which are active in acid media, can be used for bating such pelts. These enzymes clean the grain of pelt well and do not affect the collagen of pelt markedly.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90537742","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The purpose of the study was to establish if ozonation can be used to enhance the process of purifying wastewater from the yeast industry. The results of the experiments indicate that ozonation can be used in the tertiary treatment of yeast wastewater for the reduction of colour, odour, and the overall concentration of contaminants. During ozonation, the biodegradability of the wastewater increased; therefore it is possible to include ozonation into the combined purification process simultaneously with anaerobic and aerobic bio-oxidation. In addition, the application of ozonation as a pre-treatment method for anaerobic digestion of excess sludge from wastewater treatment plants was studied. Ozonation of the excess sludge resulted in a reduction of the sludge amount and increased the solubility of sludge organic matter. Although the solubility of sludge increased, the process of anaerobic mesophilic digestion was not improved.
{"title":"Possibilities of using ozone for the treatment of wastewater from the yeast industry","authors":"Viktoria Blonskaja, I. Kamenev, S. Zub","doi":"10.3176/chem.2006.1.03","DOIUrl":"https://doi.org/10.3176/chem.2006.1.03","url":null,"abstract":"The purpose of the study was to establish if ozonation can be used to enhance the process of purifying wastewater from the yeast industry. The results of the experiments indicate that ozonation can be used in the tertiary treatment of yeast wastewater for the reduction of colour, odour, and the overall concentration of contaminants. During ozonation, the biodegradability of the wastewater increased; therefore it is possible to include ozonation into the combined purification process simultaneously with anaerobic and aerobic bio-oxidation. In addition, the application of ozonation as a pre-treatment method for anaerobic digestion of excess sludge from wastewater treatment plants was studied. Ozonation of the excess sludge resulted in a reduction of the sludge amount and increased the solubility of sludge organic matter. Although the solubility of sludge increased, the process of anaerobic mesophilic digestion was not improved.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"72 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86871644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Danilkin, Mihkel Kerikmäe, A. Kirillov, A. Lust, Arno Ratas, Lilli Paama, V. Seeman
The false-dose effects are investigated in the thermoluminescent detectors of ionizing radiation based on Li2B4O7:Mn,Si. To reveal the mechanism of daylight sensitivity, thermo- luminescence, EPR, and luminescence excitation studies and technological experiments were undertaken. A 400 nm light was shown to be most effective to store the dose and to excite the luminescence band near 600 nm. A charge-transfer complex of a casual titanium impurity is supposed to be responsible for daylight false-dose storage. Another mechanism of a false-dose storage is supposed to be caused by a thermally induced stress, which yields a high-temperature thermoluminescence of Li2B4O7:Mn,Si detectors. Increasing the temperature of the sintering of tablets eliminates both false-dose effects. Possible models of energy storage are discussed.
{"title":"Thermoluminescent dosimeter Li2B4O7:Mn,Si – a false-dose problem","authors":"M. Danilkin, Mihkel Kerikmäe, A. Kirillov, A. Lust, Arno Ratas, Lilli Paama, V. Seeman","doi":"10.3176/chem.2006.3.01","DOIUrl":"https://doi.org/10.3176/chem.2006.3.01","url":null,"abstract":"The false-dose effects are investigated in the thermoluminescent detectors of ionizing radiation based on Li2B4O7:Mn,Si. To reveal the mechanism of daylight sensitivity, thermo- luminescence, EPR, and luminescence excitation studies and technological experiments were undertaken. A 400 nm light was shown to be most effective to store the dose and to excite the luminescence band near 600 nm. A charge-transfer complex of a casual titanium impurity is supposed to be responsible for daylight false-dose storage. Another mechanism of a false-dose storage is supposed to be caused by a thermally induced stress, which yields a high-temperature thermoluminescence of Li2B4O7:Mn,Si detectors. Increasing the temperature of the sintering of tablets eliminates both false-dose effects. Possible models of energy storage are discussed.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74342394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The intrinsic gas-phase acidities of CB 4XnH5-nH and CB5XnH6-n (X ≡ F, Cl or CF3) were calculated using the DFT B3LYP method at the 6-311+G** level. For comparison also the 6-31+G* basis set was used for fluorinated species. The results of the two calculation levels correlated satisfactorily. As the most favourable protonation site of these anions, the facet on the opposite side from the carbon-peaked polyhedron was found. When ordering the substituent groups in terms of increasing acidity of the carboranes, the order F < Cl < CF 3 was obtained.
{"title":"Some small weakly coordinating anions based on carboranes","authors":"Lauri Lipping, I. Koppel, I. Koppel, I. Leito","doi":"10.3176/chem.2006.3.03","DOIUrl":"https://doi.org/10.3176/chem.2006.3.03","url":null,"abstract":"The intrinsic gas-phase acidities of CB 4XnH5-nH and CB5XnH6-n (X ≡ F, Cl or CF3) were calculated using the DFT B3LYP method at the 6-311+G** level. For comparison also the 6-31+G* basis set was used for fluorinated species. The results of the two calculation levels correlated satisfactorily. As the most favourable protonation site of these anions, the facet on the opposite side from the carbon-peaked polyhedron was found. When ordering the substituent groups in terms of increasing acidity of the carboranes, the order F < Cl < CF 3 was obtained.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83100372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A computerized database on rate and equilibrium constants of chemical reactions was created. Two versions of the database, one limited to the pKa data, which employs the graphical display of the structures, and the other that enables systematic withdrawal of data selected by several conditions over all 14 main reaction types, are represented. The algorithm for statistical treatment of large sets of data to create and check mathematical models for their chemical interpretation was modified and refined. The software has been used for the treatment of large sets of data on solvent and subtituent effects and can be employed for the prognosis of new data not yet studied experimentally.
{"title":"Computerized database and software for retrieval, processing, and prognosis of rate and equilibrium constants of chemical reactions","authors":"V. Palm, N. Palm, T. Tenno","doi":"10.3176/chem.2006.1.01","DOIUrl":"https://doi.org/10.3176/chem.2006.1.01","url":null,"abstract":"A computerized database on rate and equilibrium constants of chemical reactions was created. Two versions of the database, one limited to the pKa data, which employs the graphical display of the structures, and the other that enables systematic withdrawal of data selected by several conditions over all 14 main reaction types, are represented. The algorithm for statistical treatment of large sets of data to create and check mathematical models for their chemical interpretation was modified and refined. The software has been used for the treatment of large sets of data on solvent and subtituent effects and can be employed for the prognosis of new data not yet studied experimentally.","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2006-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83898212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Comparative semiempirical, ab initio, and DFT study of interactions between polypyrrole pentamer dication and some anions","authors":"P. Burk, I. Rauk, T. Tamm","doi":"10.3176/chem.2005.2.04","DOIUrl":"https://doi.org/10.3176/chem.2005.2.04","url":null,"abstract":"","PeriodicalId":20551,"journal":{"name":"Proceedings of the Estonian Academy of Sciences. Chemistry","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2005-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72980492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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