Pub Date : 2014-02-21DOI: 10.2478/s11532-014-0514-6
Yaroslava Pushkarova, Y. Kholin
AbstractArtificial neural networks have proven to be a powerful tool for solving classification problems. Some difficulties still need to be overcome for their successful application to chemical data. The use of supervised neural networks implies the initial distribution of patterns between the pre-determined classes, while attribution of objects to the classes may be uncertain. Unsupervised neural networks are free from this problem, but do not always reveal the real structure of data. Classification algorithms which do not require a priori information about the distribution of patterns between the pre-determined classes and provide meaningful results are of special interest. This paper presents an approach based on the combination of Kohonen and probabilistic networks which enables the determination of the number of classes and the reliable classification of objects. This is illustrated for a set of 76 solvents based on nine characteristics. The resulting classification is chemically interpretable. The approach proved to be also applicable in a different field, namely in examining the solubility of C60 fullerene. The solvents belonging to the same group demonstrate similar abilities to dissolve C60. This makes it possible to estimate the solubility of fullerenes in solvents for which there are no experimental data
{"title":"A procedure for meaningful unsupervised clustering and its application for solvent classification","authors":"Yaroslava Pushkarova, Y. Kholin","doi":"10.2478/s11532-014-0514-6","DOIUrl":"https://doi.org/10.2478/s11532-014-0514-6","url":null,"abstract":"AbstractArtificial neural networks have proven to be a powerful tool for solving classification problems. Some difficulties still need to be overcome for their successful application to chemical data. The use of supervised neural networks implies the initial distribution of patterns between the pre-determined classes, while attribution of objects to the classes may be uncertain. Unsupervised neural networks are free from this problem, but do not always reveal the real structure of data. Classification algorithms which do not require a priori information about the distribution of patterns between the pre-determined classes and provide meaningful results are of special interest. This paper presents an approach based on the combination of Kohonen and probabilistic networks which enables the determination of the number of classes and the reliable classification of objects. This is illustrated for a set of 76 solvents based on nine characteristics. The resulting classification is chemically interpretable. The approach proved to be also applicable in a different field, namely in examining the solubility of C60 fullerene. The solvents belonging to the same group demonstrate similar abilities to dissolve C60. This makes it possible to estimate the solubility of fullerenes in solvents for which there are no experimental data\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"35 1","pages":"594-603"},"PeriodicalIF":0.0,"publicationDate":"2014-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75116102","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}
Pub Date : 2014-02-21DOI: 10.2478/s11532-014-0512-8
E. Gorodkiewicz, A. Sankiewicz, P. Laudański
AbstractAromatase (ARO) is an enzyme with potential diagnostic significance. Aberrant expression of aromatase in tissues is associated with a number of pathological conditions, including tumor of the breast, ovary, testes, liver, adrenal cortex and uterus, as well as endometriosis.Two methods for the highly selective determination of ARO concentration in human tissues by using of two different biosensors co-operating with the surface plasmon resonance imaging technique (SPRI) have been developed. One of the developed biosensors contains immobilised rabbit polyclonal antibody specific for aromatase (Y-ARO), while the other contains immobilized ARO inhibitor-exemestane (E-ARO). Both biosensors specifically bound ARO from analyzed samples. The analytically useful dynamic response range of both biosensors is between 0.3 and 5.0 ng mL−1. The detection limit (3S.D.) of both biosensors is 90 pg mL−1. Standard deviation of both biosensors is 1%. Recoveries of ARO spikes are between 97 and 108% for both biosensors under model conditions and for real samples. Albumin and alkaline phosphatase are tolerated for both biosensors up to 10,000 fold excess.
摘要:纤维素酶(ARO)是一种具有潜在诊断意义的酶。芳香化酶在组织中的异常表达与许多病理状况有关，包括乳腺、卵巢、睾丸、肝脏、肾上腺皮质和子宫的肿瘤，以及子宫内膜异位症。利用两种不同的生物传感器与表面等离子体共振成像技术(SPRI)合作，开发了两种高选择性测定人体组织中ARO浓度的方法。其中一种生物传感器含有固定化兔特异性芳香化酶多克隆抗体(Y-ARO)，另一种生物传感器含有固定化芳香化酶抑制剂依西美坦(E-ARO)。这两种生物传感器都能从分析的样品中特异性地结合ARO。两种生物传感器的分析有用的动态响应范围在0.3和5.0 ng mL−1之间。两种生物传感器的检测限(3sd)均为90 pg mL−1。两种生物传感器的标准偏差均为1%。在模型条件下和实际样品中，生物传感器的ARO峰值回收率在97 - 108%之间。白蛋白和碱性磷酸酶对这两种生物传感器的耐受性高达10,000倍。
{"title":"Surface plasmon resonance imaging biosensors for aromatase based on a potent inhibitor and a specific antibody: Sensor development and application for biological material","authors":"E. Gorodkiewicz, A. Sankiewicz, P. Laudański","doi":"10.2478/s11532-014-0512-8","DOIUrl":"https://doi.org/10.2478/s11532-014-0512-8","url":null,"abstract":"AbstractAromatase (ARO) is an enzyme with potential diagnostic significance. Aberrant expression of aromatase in tissues is associated with a number of pathological conditions, including tumor of the breast, ovary, testes, liver, adrenal cortex and uterus, as well as endometriosis.Two methods for the highly selective determination of ARO concentration in human tissues by using of two different biosensors co-operating with the surface plasmon resonance imaging technique (SPRI) have been developed. One of the developed biosensors contains immobilised rabbit polyclonal antibody specific for aromatase (Y-ARO), while the other contains immobilized ARO inhibitor-exemestane (E-ARO). Both biosensors specifically bound ARO from analyzed samples. The analytically useful dynamic response range of both biosensors is between 0.3 and 5.0 ng mL−1. The detection limit (3S.D.) of both biosensors is 90 pg mL−1. Standard deviation of both biosensors is 1%. Recoveries of ARO spikes are between 97 and 108% for both biosensors under model conditions and for real samples. Albumin and alkaline phosphatase are tolerated for both biosensors up to 10,000 fold excess.\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"97 1","pages":"557-567"},"PeriodicalIF":0.0,"publicationDate":"2014-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85911970","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}
Pub Date : 2014-02-21DOI: 10.2478/s11532-014-0518-2
R. Jasiński, Magda Ziółkowska, O. Demchuk, Agata Maziarka
Abstract[2+3] Cycloaddition reactions of the highly reactive (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone with (E)-2-R-nitroethenes proceed under mild conditions and yield mixtures of stereoisomeric 2-methyl-3-(3,4,5-trimethoxyphenyl)-4-nitro-5-R-isoxazolidines. The effect of regiospecificity of the cycloadditions may be accounted for by the theory of electrophilicity indexes. Stereoselectivity, however, is determined by a compilation of steric and secondary orbital effects.
摘要[2+3]高活性(Z)- c -(3,4,5-三甲氧基苯基)- n -甲基硝基酮与(E)-2- r -亚硝基苯基)在温和条件下进行环加成反应，得到立体异构体2-甲基-3-(3,4,5-三甲氧基苯基)-4-硝基-5- r -异恶唑烷的混合物。环加成的区域特异性可以用亲电性指数理论来解释。然而，立体选择性是由空间和次级轨道效应的综合决定的。
{"title":"Regio- and stereoselectivity of polar [2+3] cycloaddition reactions between (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone and selected (E)-2-substituted nitroethenes","authors":"R. Jasiński, Magda Ziółkowska, O. Demchuk, Agata Maziarka","doi":"10.2478/s11532-014-0518-2","DOIUrl":"https://doi.org/10.2478/s11532-014-0518-2","url":null,"abstract":"Abstract[2+3] Cycloaddition reactions of the highly reactive (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone with (E)-2-R-nitroethenes proceed under mild conditions and yield mixtures of stereoisomeric 2-methyl-3-(3,4,5-trimethoxyphenyl)-4-nitro-5-R-isoxazolidines. The effect of regiospecificity of the cycloadditions may be accounted for by the theory of electrophilicity indexes. Stereoselectivity, however, is determined by a compilation of steric and secondary orbital effects.\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"2 1","pages":"586-593"},"PeriodicalIF":0.0,"publicationDate":"2014-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80256710","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}
Pub Date : 2014-02-21DOI: 10.2478/s11532-014-0522-6
Alicja Gackowska, Maciej Przybyłek, W. Studziński, J. Gaca
Abstract2-Ethylhexyl 4-methoxycinnamate (EHMC) is one of the most commonly used sunscreen ingredient. In this study we investigated photodegradation of EHMC in the presence of such common oxidizing and chlorinating systems as H2O2, H2O2/HCl, H2O2/UV, and H2O2/HCl/UV. Reaction products were detected by gas chromatography with a mass spectrometric detector (GC-MS). As a result of experimental studies chloro-substituted 4-methoxycinnamic acid (4-MCA), 4-methoxybenzaldehyde (4-MBA) and 4-methoxyphenol (4-MP) were identified. Experimental studies were enriched with DFT and MP2 calculations. We found that reactions of 4-MCA, 4-MBA and 4-MP with Cl2 and HOCl were in all cases thermodynamically favorable. However, reactivity indices provide a better explanation of the formation of particular chloroorganic compounds. Generally, those isomeric forms of mono- and dichlorinated compounds which exhibits the highest hardness were identified. Nucleophilicity of the chloroorganic compounds precursors were examined by means of the Fukui function.
{"title":"Experimental and theoretical studies on the photodegradation of 2-ethylhexyl 4-methoxycinnamate in the presence of reactive oxygen and chlorine species","authors":"Alicja Gackowska, Maciej Przybyłek, W. Studziński, J. Gaca","doi":"10.2478/s11532-014-0522-6","DOIUrl":"https://doi.org/10.2478/s11532-014-0522-6","url":null,"abstract":"Abstract2-Ethylhexyl 4-methoxycinnamate (EHMC) is one of the most commonly used sunscreen ingredient. In this study we investigated photodegradation of EHMC in the presence of such common oxidizing and chlorinating systems as H2O2, H2O2/HCl, H2O2/UV, and H2O2/HCl/UV. Reaction products were detected by gas chromatography with a mass spectrometric detector (GC-MS). As a result of experimental studies chloro-substituted 4-methoxycinnamic acid (4-MCA), 4-methoxybenzaldehyde (4-MBA) and 4-methoxyphenol (4-MP) were identified. Experimental studies were enriched with DFT and MP2 calculations. We found that reactions of 4-MCA, 4-MBA and 4-MP with Cl2 and HOCl were in all cases thermodynamically favorable. However, reactivity indices provide a better explanation of the formation of particular chloroorganic compounds. Generally, those isomeric forms of mono- and dichlorinated compounds which exhibits the highest hardness were identified. Nucleophilicity of the chloroorganic compounds precursors were examined by means of the Fukui function.\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"5 1","pages":"612-623"},"PeriodicalIF":0.0,"publicationDate":"2014-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82220493","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}
Pub Date : 2014-02-21DOI: 10.2478/s11532-014-0515-5
M. Petrovic, I. Talian, Lenka Škantárová, A. Oriňak, D. Velic
AbstractThis paper dealt with the preparation and characterization of self — assembled monolayersSAM-s of 1-hexadecanethiole and mercapto acetic acid on the silver nanostructure and subsequently the immobilization with amino acid L-Tryptophane. In order to achieve it, we used the electrodeposition of silver onto nanostructured surface of paraffin impregnated graphite electrode (PIGE). Subsequently, we assembled SAM by choosing the 1-hexadecanethiole and mercaptoacetic acid. These two kinds of SAM underwent the functionalization by L-Tryptophan. The observations of silver on PIGE surfaces were performed by scanning electron microscope (SEM). For surface analysis of the SAM functionalized by L-tryphophan, the TOF-SIMS technique was chosen. Finally, the fragmented ions of the immobilized-L-Tryptophan SAM were determined on the basis of suggested residues and three-dimensional structure. The residues show that the ability of L-Tryptophan to build homogeneous structure is better by mercaptoacetic acid SAM structure than by 1-hexadecanethiol. It was observed that L-Tryptophan built compact surface, which, due its chemical properties, can represent very interesting side regarding biocompatibility, homochirality and robustness in the area of life science.
{"title":"TOF-SIMS surface analysis of L-Tryptophan self assembled monolayer","authors":"M. Petrovic, I. Talian, Lenka Škantárová, A. Oriňak, D. Velic","doi":"10.2478/s11532-014-0515-5","DOIUrl":"https://doi.org/10.2478/s11532-014-0515-5","url":null,"abstract":"AbstractThis paper dealt with the preparation and characterization of self — assembled monolayersSAM-s of 1-hexadecanethiole and mercapto acetic acid on the silver nanostructure and subsequently the immobilization with amino acid L-Tryptophane. In order to achieve it, we used the electrodeposition of silver onto nanostructured surface of paraffin impregnated graphite electrode (PIGE). Subsequently, we assembled SAM by choosing the 1-hexadecanethiole and mercaptoacetic acid. These two kinds of SAM underwent the functionalization by L-Tryptophan. The observations of silver on PIGE surfaces were performed by scanning electron microscope (SEM). For surface analysis of the SAM functionalized by L-tryphophan, the TOF-SIMS technique was chosen. Finally, the fragmented ions of the immobilized-L-Tryptophan SAM were determined on the basis of suggested residues and three-dimensional structure. The residues show that the ability of L-Tryptophan to build homogeneous structure is better by mercaptoacetic acid SAM structure than by 1-hexadecanethiol. It was observed that L-Tryptophan built compact surface, which, due its chemical properties, can represent very interesting side regarding biocompatibility, homochirality and robustness in the area of life science.\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"19 1","pages":"568-576"},"PeriodicalIF":0.0,"publicationDate":"2014-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75328161","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}
Pub Date : 2014-02-21DOI: 10.2478/s11532-014-0528-0
L. Lochmann, M. Janata
AbstractA review of reactions of organolithium compounds (RLi) with alkali metal alkoxides is presented. On the one hand, simple lithium alkoxides form adducts with RLi the reactivity of which differs only slightly from that of RLi. On the other hand, after mixing heavier alkali metal alkoxides (R’OM, M = Na, K, Rb, Cs) with RLi, a new system is formed, which has reactivity that dramatically exceeds that of the parent RLi. A metal interchange, according to the equation RLi + R’OM = RM + R’OLi, occurs in this system, giving rise to a superbase. This reaction is frequently used for the preparation of heavier alkali metal organometallic compounds. Similar metal interchange takes place between R’OM and compounds such as lithium amides and lithium enolates of ketones or esters, thus demonstrating the general nature of this procedure. Superbases react easily with many types of organic compounds (substrates), resulting in the formation of a heavier alkali metal derivative of the substrate (metalation). The metalated substrate can react in situ with an electrophile to yield the substituted substrate, a procedure that is frequently used in synthetic and polymer chemistry. An improved mechanism of metal interchange and reaction of superbases with substrates is proposed.
摘要综述了有机锂化合物(RLi)与碱金属烷氧化物的反应。一方面，简单的锂烷氧化物与RLi形成加合物，其反应活性与RLi仅略有不同。另一方面，较重的碱金属烷氧化物(R 'OM, M = Na, K, Rb, Cs)与RLi混合后，形成新的体系，其反应活性大大超过母体RLi。根据方程RLi + R 'OM = RM + R 'OLi，在该体系中发生了金属交换，产生了超碱。该反应常用于制备较重的碱金属有机金属化合物。类似的金属交换也发生在R 'OM和化合物之间，如锂酰胺和锂烯醇化酮或酯，从而证明了该过程的一般性质。超碱很容易与许多类型的有机化合物(底物)反应，导致底物形成较重的碱金属衍生物(金属化)。金属化底物可以在原位与亲电试剂反应生成取代底物，这一过程经常用于合成和聚合物化学。提出了一种改进的金属交换和超碱与底物反应机理。
{"title":"50 years of superbases made from organolithium compounds and heavier alkali metal alkoxides","authors":"L. Lochmann, M. Janata","doi":"10.2478/s11532-014-0528-0","DOIUrl":"https://doi.org/10.2478/s11532-014-0528-0","url":null,"abstract":"AbstractA review of reactions of organolithium compounds (RLi) with alkali metal alkoxides is presented. On the one hand, simple lithium alkoxides form adducts with RLi the reactivity of which differs only slightly from that of RLi. On the other hand, after mixing heavier alkali metal alkoxides (R’OM, M = Na, K, Rb, Cs) with RLi, a new system is formed, which has reactivity that dramatically exceeds that of the parent RLi. A metal interchange, according to the equation RLi + R’OM = RM + R’OLi, occurs in this system, giving rise to a superbase. This reaction is frequently used for the preparation of heavier alkali metal organometallic compounds. Similar metal interchange takes place between R’OM and compounds such as lithium amides and lithium enolates of ketones or esters, thus demonstrating the general nature of this procedure. Superbases react easily with many types of organic compounds (substrates), resulting in the formation of a heavier alkali metal derivative of the substrate (metalation). The metalated substrate can react in situ with an electrophile to yield the substituted substrate, a procedure that is frequently used in synthetic and polymer chemistry. An improved mechanism of metal interchange and reaction of superbases with substrates is proposed.\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"18 1","pages":"537-548"},"PeriodicalIF":0.0,"publicationDate":"2014-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83278224","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}
Pub Date : 2014-02-20DOI: 10.2478/s11532-014-0532-4
I. Călinescu, A. Gavrila, M. Ivopol, G. Ivopol, M. Popescu, Nectara Mircioaga
In this study, microwave assisted a hydrodistillation process (MWHD) of essential oils from lavender (Lavandula angustifolia Miller) was investigated. In order to examine any potential differences in essential oil extraction, the lavender flowers underwent enzymatic pretreatment.A 23 factorial design of experiments, combined with statistical methods of data analysis were used to optimize enzymatic pretreatment and to evaluate the influence of major variables (enzyme concentration, temperature and pH) on the performance of the microwave assisted extraction.Under optimal conditions, an extraction yield of 24 mg oil g−1 substrate was achieved (an increase by approximately 25% in comparison with the classic extraction conditions of conventional hydrodistillation).The main compounds of the essential oils obtained were analyzed and identified by gas chromatography coupled to mass spectrometry (GC-MS). Analyzing the data obtained indicated that the content of main compounds (linalool and linalyl acetate − 73%) was greater than that obtained by conventional extraction (67%).
研究了微波辅助加氢蒸馏法提取薰衣草精油的工艺条件。为了检查精油提取的任何潜在差异，薰衣草花进行了酶预处理。采用23因子实验设计，结合数据分析的统计方法，优化酶解预处理，评价酶浓度、温度、pH等主要变量对微波辅助提取效果的影响。在最佳条件下，油的提取率达到24 mg g - 1底物(与传统加氢蒸馏的经典提取条件相比，提高了约25%)。采用气相色谱-质谱联用技术(GC-MS)对所得精油的主要成分进行了分析鉴定。分析结果表明，其主要成分(芳樟醇和乙酸芳樟醇)的含量(- 73%)高于常规提取法(67%)。
{"title":"Microwave assisted extraction of essential oils from enzymatically pretreated lavender (Lavandula angustifolia Miller)","authors":"I. Călinescu, A. Gavrila, M. Ivopol, G. Ivopol, M. Popescu, Nectara Mircioaga","doi":"10.2478/s11532-014-0532-4","DOIUrl":"https://doi.org/10.2478/s11532-014-0532-4","url":null,"abstract":"In this study, microwave assisted a hydrodistillation process (MWHD) of essential oils from lavender (Lavandula angustifolia Miller) was investigated. In order to examine any potential differences in essential oil extraction, the lavender flowers underwent enzymatic pretreatment.A 23 factorial design of experiments, combined with statistical methods of data analysis were used to optimize enzymatic pretreatment and to evaluate the influence of major variables (enzyme concentration, temperature and pH) on the performance of the microwave assisted extraction.Under optimal conditions, an extraction yield of 24 mg oil g−1 substrate was achieved (an increase by approximately 25% in comparison with the classic extraction conditions of conventional hydrodistillation).The main compounds of the essential oils obtained were analyzed and identified by gas chromatography coupled to mass spectrometry (GC-MS). Analyzing the data obtained indicated that the content of main compounds (linalool and linalyl acetate − 73%) was greater than that obtained by conventional extraction (67%).","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"16 1","pages":"829-836"},"PeriodicalIF":0.0,"publicationDate":"2014-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74795758","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}
Pub Date : 2014-02-08DOI: 10.2478/s11532-014-0505-7
A. Gonţa, T. Lupascu, N. Timbaliuc, A. Meghea
AbstractAfter oxidation of tannins (Tannins 1–3) extracted from grape seeds, Tanoxil compounds with increased solubility and enhanced antioxidant activities were synthesized. In this research, ABTS+· assay and a chemiluminescence method were used for antioxidant measurement of hydrophilic compounds (Tanoxils 1–3).It was observed that the antioxidant activity (AA, %) is very similar for the three samples, while at the same time AA is quite high (93.16%–96.48%). The percentage of inhibition by ABTS+· is higher for Tanoxil 2 (96.4%) as compared to Tannin 2 compound (14.34%). Moreover, the total content (TCF) of carboxyl and phenolic groups was investigated. TCF values, determined for Tanoxil products, revealed a double (Tanoxil 1) or triple (Tanoxil 2) increase as compared to the value of the TCF of Tannin 1. Tanoxil products represent an interest for future research as they have a high AA (96.4%) and the content of acidic groups is significant (TCF, 0.191 meq g−1).
{"title":"Obtaining and characterizing modified tannins by physical-chemical methods","authors":"A. Gonţa, T. Lupascu, N. Timbaliuc, A. Meghea","doi":"10.2478/s11532-014-0505-7","DOIUrl":"https://doi.org/10.2478/s11532-014-0505-7","url":null,"abstract":"AbstractAfter oxidation of tannins (Tannins 1–3) extracted from grape seeds, Tanoxil compounds with increased solubility and enhanced antioxidant activities were synthesized. In this research, ABTS+· assay and a chemiluminescence method were used for antioxidant measurement of hydrophilic compounds (Tanoxils 1–3).It was observed that the antioxidant activity (AA, %) is very similar for the three samples, while at the same time AA is quite high (93.16%–96.48%). The percentage of inhibition by ABTS+· is higher for Tanoxil 2 (96.4%) as compared to Tannin 2 compound (14.34%). Moreover, the total content (TCF) of carboxyl and phenolic groups was investigated. TCF values, determined for Tanoxil products, revealed a double (Tanoxil 1) or triple (Tanoxil 2) increase as compared to the value of the TCF of Tannin 1. Tanoxil products represent an interest for future research as they have a high AA (96.4%) and the content of acidic groups is significant (TCF, 0.191 meq g−1).\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"44 1","pages":"757-762"},"PeriodicalIF":0.0,"publicationDate":"2014-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79380015","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}
Pub Date : 2014-02-01DOI: 10.2478/s11532-013-0376-3
A. Nosal-Wiercińska
AbstractThe results of the kinetic measurements of Bi(III) electroreduction on a mercury electrode in 1–8 mol dm−3 chlorate (VII) solutions and in the presence of cystine demonstrate a dependence of the process on the temperature. The applied electrochemical techniques (DC polarography, cyclic and SWV voltammetry) allowed for the determination of the kinetic and thermodynamic parameters and their correlation with water activity. The catalytic activity of cystine was confirmed by the decrease in overall enthalpies of activation. The changes in the values of ΔH≠ and ΔS0 for Bi(III) electroreduction in the presence of cystine with the increase of chlorate (VII) concentration showed that the mechanism is different in solutions with low water activity as compared to those with high water activity. Probably it is connected with a different structure of the activated complexes (Bi-Hg(SR)2), mediating electron transfer.
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Pub Date : 2014-02-01DOI: 10.2478/s11532-013-0359-4
V. Anishchenko, V. I. Rybachenko, K. Chotiy, A. Redko
AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.
{"title":"DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates","authors":"V. Anishchenko, V. I. Rybachenko, K. Chotiy, A. Redko","doi":"10.2478/s11532-013-0359-4","DOIUrl":"https://doi.org/10.2478/s11532-013-0359-4","url":null,"abstract":"AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.\u0000","PeriodicalId":9888,"journal":{"name":"Central European Journal of Chemistry","volume":"34 1","pages":"153-163"},"PeriodicalIF":0.0,"publicationDate":"2014-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76578095","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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