FTIR spectroscopy was used to investigate the effects of extremely low frequency (50 Hz) electromagnetic field and of microwaves at 900 MHz on the secondary structure of a typical protein, the lysozyme, evaluating the bioprotective effectiveness of trehalose. Lysozyme in D2O solution (60 mg/ml) was exposed to 50 Hz frequency electromagnetic field at 180 μT. The FTIR spectra indicated an increase of CH2 group at 1921 and 1853 cm−1 after 3 h of exposure. Such effect was not observed after the addition of trehalose (150 mg/mL) at the same exposure conditions. Lysozyme dissolved in D2O at the concentration of 100 mg/mL was exposed up to 4 h to 900 MHz mobile phone microwaves at 25 mA/m. A significant increase in intensity of the amide I vibration band in the secondary structure of the protein was observed after 4 h exposure to microwaves. This effect was inhibited by the presence of trehalose at the concentration of 150 mg/mL. Fourier self-deconvolution spectral analysis of lysozyme in D2O solution after exposure to microwaves revealed an increase in intensity of the conformational components of amide I mode, particularly of β-sheet and turn that can be attributed to disorder and unfolding processes of the protein.
{"title":"Electromagnetic Fields Effects on the Secondary Structure of Lysozyme and Bioprotective Effectiveness of Trehalose","authors":"E. Calabrò, S. Magazù","doi":"10.1155/2012/970369","DOIUrl":"https://doi.org/10.1155/2012/970369","url":null,"abstract":"FTIR spectroscopy was used to investigate the effects of extremely low frequency (50 Hz) electromagnetic field and of microwaves at 900 MHz on the secondary structure of a typical protein, the lysozyme, evaluating the bioprotective effectiveness of trehalose. Lysozyme in D2O solution (60 mg/ml) was exposed to 50 Hz frequency electromagnetic field at 180 μT. The FTIR spectra indicated an increase of CH2 group at 1921 and 1853 cm−1 after 3 h of exposure. Such effect was not observed after the addition of trehalose (150 mg/mL) at the same exposure conditions. Lysozyme dissolved in D2O at the concentration of 100 mg/mL was exposed up to 4 h to 900 MHz mobile phone microwaves at 25 mA/m. A significant increase in intensity of the amide I vibration band in the secondary structure of the protein was observed after 4 h exposure to microwaves. This effect was inhibited by the presence of trehalose at the concentration of 150 mg/mL. Fourier self-deconvolution spectral analysis of lysozyme in D2O solution after exposure to microwaves revealed an increase in intensity of the conformational components of amide I mode, particularly of β-sheet and turn that can be attributed to disorder and unfolding processes of the protein.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82609475","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 Stern-Volmer constant is specified for the luminescence quenched by reversible ionization of excited molecules. The exergonic branch of the Rehm-Weller free energy dependence of this constant is known to be a plateau determined by irreversible ionization being under diffusion control. In the endergonic region the ionization is reversible and competes with the irreversible in-cage recombination of ions and their escape from the cage. At strong Coulomb attraction the latter phenomenon is shown to be negligible compared to the former that determines the shape and location of the descending branch of the Rehm-Weller curve. At weaker Coulomb attraction (at higher solvent polarity), this curve turns down at larger endergonicity. The experimental data obtained in solvents of different polarities are put in order and in full accordance with present theory.
{"title":"Fluorescence Quenching by Reversible Charge Separation Followed by Ions Recombination and Their Separation Suppressed by Coulomb Attraction","authors":"A. Burshtein, A. Doktorov","doi":"10.1155/2012/962594","DOIUrl":"https://doi.org/10.1155/2012/962594","url":null,"abstract":"The Stern-Volmer constant is specified for the luminescence quenched by reversible ionization of excited molecules. The exergonic branch of the Rehm-Weller free energy dependence of this constant is known to be a plateau determined by irreversible ionization being under diffusion control. In the endergonic region the ionization is reversible and competes with the irreversible in-cage recombination of ions and their escape from the cage. At strong Coulomb attraction the latter phenomenon is shown to be negligible compared to the former that determines the shape and location of the descending branch of the Rehm-Weller curve. At weaker Coulomb attraction (at higher solvent polarity), this curve turns down at larger endergonicity. The experimental data obtained in solvents of different polarities are put in order and in full accordance with present theory.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89386426","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 emergence of putative Hammett equation in mid 1930s was a boon to physical-organic chemists to elucidate the reaction mechanisms of several organic reactions. Based on the concept of this equation several hundreds of papers have emerged in chemical literature in the last century on the effect of structure, on reactivity, and very few on thermodynamic stability and kinetic reactivity of intermediates. In this article an attempt is made to explain the effect of hetero atom on Hammett’s reaction constant (ρ) taking the dissociation equilibriums of benzoic acids, dithiobenzoic acids, phenols, and thiophenols.
{"title":"Effect of Hetero Atom on the Hammett’s Reaction Constant () from the Physical Basis of Dissociation Equilibriums of (Dithio) Benzoic Acids and (Thio) Phenols and Its Application to Solvolysis Reactions and Some Free Radical Reactions","authors":"Jagannadham Vandanapu, S. Rachuru","doi":"10.1155/2012/598243","DOIUrl":"https://doi.org/10.1155/2012/598243","url":null,"abstract":"The emergence of putative Hammett equation in mid 1930s was a boon to physical-organic chemists to elucidate the reaction mechanisms of several organic reactions. Based on the concept of this equation several hundreds of papers have emerged in chemical literature in the last century on the effect of structure, on reactivity, and very few on thermodynamic stability and kinetic reactivity of intermediates. In this article an attempt is made to explain the effect of hetero atom on Hammett’s reaction constant (ρ) taking the dissociation equilibriums of benzoic acids, dithiobenzoic acids, phenols, and thiophenols.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76674494","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}
This paper describes the ordering degree of anionic, cationic, and zwitterionic surfactants with the increase of their packing density on Ge substrate by using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy. This work shows new insights on the conformational order of sodium dodecyl sulfate (SDS), N-hexadecyl-N-N-dimethyl-3-ammonio-1-propane-sulfonate (HPS), hexadecyl-trimethylammonium bromide (CTAB), and dodecyl trimethylammonium bromide (DTAB). DFT and semiempirical calculations are also performed in order to evaluate the effect of headgroup hydration and counterion. The CH2 asymmetric and symmetric stretching bands for the SDS molecule show a shift of 1.7 and 0.9 cm−1 to higher frequencies as the packing density increases, while it is observed a shift of 2.6 and 2.7 cm−1 for the HPS molecule, respectively. The DTAB molecule shows a shift of 4.5 cm−1 to lower frequencies for both CH2 asymmetric and symmetric stretching bands as the packing density increases, indicating the decrease of gauche conformations and the increase of all-trans conformations over the aliphatic chain.
本文利用傅里叶变换红外衰减全反射(FTIR-ATR)光谱研究了阴离子、阳离子和两性离子表面活性剂随其在Ge衬底上堆积密度的增加而产生的有序度。这项工作对十二烷基硫酸钠(SDS)、n -十六烷基- n - n -二甲基-3-氨-1-丙烷磺酸盐(HPS)、十六烷基-三甲基溴化铵(CTAB)和十二烷基三甲基溴化铵(DTAB)的构象顺序有了新的认识。为了评价头基水化和反离子的效果，还进行了DFT和半经验计算。SDS分子的CH2不对称和对称拉伸带随着填充密度的增加而向更高频率移动1.7和0.9 cm−1，而HPS分子的CH2不对称和对称拉伸带分别为2.6和2.7 cm−1。DTAB分子的CH2不对称和对称伸展带随着填充密度的增加向更低频率移动4.5 cm−1，表明脂肪链上的间扭构象减少，全反式构象增加。
{"title":"Infrared Spectroscopy of Anionic, Cationic, and Zwitterionic Surfactants","authors":"R. Viana, A. D. Silva, A. S. Pimentel","doi":"10.1155/2012/903272","DOIUrl":"https://doi.org/10.1155/2012/903272","url":null,"abstract":"This paper describes the ordering degree of anionic, cationic, and zwitterionic surfactants with the increase of their packing density on Ge substrate by using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy. This work shows new insights on the conformational order of sodium dodecyl sulfate (SDS), N-hexadecyl-N-N-dimethyl-3-ammonio-1-propane-sulfonate (HPS), hexadecyl-trimethylammonium bromide (CTAB), and dodecyl trimethylammonium bromide (DTAB). DFT and semiempirical calculations are also performed in order to evaluate the effect of headgroup hydration and counterion. The CH2 asymmetric and symmetric stretching bands for the SDS molecule show a shift of 1.7 and 0.9 cm−1 to higher frequencies as the packing density increases, while it is observed a shift of 2.6 and 2.7 cm−1 for the HPS molecule, respectively. The DTAB molecule shows a shift of 4.5 cm−1 to lower frequencies for both CH2 asymmetric and symmetric stretching bands as the packing density increases, indicating the decrease of gauche conformations and the increase of all-trans conformations over the aliphatic chain.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84547238","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}
In theoretical studies of chemical reactions involving multiple potential energy surfaces (PESs) such as photochemical reactions, seams of intersection among the PESs often complicate the analysis. In this paper, we review our recipe for exploring multiple PESs by using an automated reaction path search method which has previously been applied to single PESs. Although any such methods for single PESs can be employed in the recipe, the global reaction route mapping (GRRM) method was employed in this study. By combining GRRM with the proposed recipe, all critical regions, that is, transition states, conical intersections, intersection seams, and local minima, associated with multiple PESs, can be explored automatically. As illustrative examples, applications to photochemistry of formaldehyde and acetone are described. In these examples as well as in recent applications to other systems, the present approach led to discovery of many unexpected nonadiabatic pathways, by which some complicated experimental data have been explained very clearly.
{"title":"Exploring Multiple Potential Energy Surfaces: Photochemistry of Small Carbonyl Compounds","authors":"S. Maeda, K. Ohno, K. Morokuma","doi":"10.1155/2012/268124","DOIUrl":"https://doi.org/10.1155/2012/268124","url":null,"abstract":"In theoretical studies of chemical reactions involving multiple potential energy surfaces (PESs) such as photochemical reactions, seams of intersection among the PESs often complicate the analysis. In this paper, we review our recipe for exploring multiple PESs by using an automated reaction path search method which has previously been applied to single PESs. Although any such methods for single PESs can be employed in the recipe, the global reaction route mapping (GRRM) method was employed in this study. By combining GRRM with the proposed recipe, all critical regions, that is, transition states, conical intersections, intersection seams, and local minima, associated with multiple PESs, can be explored automatically. As illustrative examples, applications to photochemistry of formaldehyde and acetone are described. In these examples as well as in recent applications to other systems, the present approach led to discovery of many unexpected nonadiabatic pathways, by which some complicated experimental data have been explained very clearly.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89992354","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}
L. Bytautas, J. Bowman, Xinchuan Huang, A. Varandas
{"title":"Accurate Potential Energy Surfaces and Beyond: Chemical Reactivity, Binding, Long-Range Interactions, and Spectroscopy","authors":"L. Bytautas, J. Bowman, Xinchuan Huang, A. Varandas","doi":"10.1155/2012/679869","DOIUrl":"https://doi.org/10.1155/2012/679869","url":null,"abstract":"","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73944746","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. Ebrahimi, M. Habibi-Khorassani, F. B. Akher, Abdolkarim Farrokhzadeh
The effects of substituents on the N⋯HF interactions in the X-pyridazine⋯(HF)𝑛 (X = N(CH3)2, NHCH3, NH2, C2H5, CH3, OCH3, OH, CN, OF, NO2, F, Br, Cl, and 𝑛=1,2) complexes have been studied at the B3LYP/6-311
{"title":"The N⋯HF Interactions in the X-Pyridazine⋯ (HF) Complexes: Substituent Effects and Energy Components","authors":"A. Ebrahimi, M. Habibi-Khorassani, F. B. Akher, Abdolkarim Farrokhzadeh","doi":"10.1155/2012/362608","DOIUrl":"https://doi.org/10.1155/2012/362608","url":null,"abstract":"The effects of substituents on the N⋯HF interactions in the X-pyridazine⋯(HF)𝑛 (X = N(CH3)2, NHCH3, NH2, C2H5, CH3, OCH3, OH, CN, OF, NO2, F, Br, Cl, and 𝑛=1,2) complexes have been studied at the B3LYP/6-311","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85510721","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}
1 Institute of Chemical Engineering and High Temperature Chemical Processes-Patras, FORTH, 26500 Patras, Greece 2 Institute of Food Technology, Faculty of Agriculture, University of Belgrade, 11080 Belgrade, Serbia 3 Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany 4Department of Material Science and Engineering and Canadian Centre for Electron Microscopy, McMaster University, Hamilton ON, Canada L8S4M1
{"title":"Advances in Electrocatalysis","authors":"M. Jakšić, Wolfgang Schmickleer, G. Botton","doi":"10.1155/2012/180604","DOIUrl":"https://doi.org/10.1155/2012/180604","url":null,"abstract":"1 Institute of Chemical Engineering and High Temperature Chemical Processes-Patras, FORTH, 26500 Patras, Greece 2 Institute of Food Technology, Faculty of Agriculture, University of Belgrade, 11080 Belgrade, Serbia 3 Institute of Theoretical Chemistry, Ulm University, 89081 Ulm, Germany 4Department of Material Science and Engineering and Canadian Centre for Electron Microscopy, McMaster University, Hamilton ON, Canada L8S4M1","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72592353","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}
Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR) involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes) has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed.
{"title":"Fundamental Mechanistic Understanding of Electrocatalysis of Oxygen Reduction on Pt and Non-Pt Surfaces: Acid versus Alkaline Media","authors":"N. Ramaswamy, S. Mukerjee","doi":"10.1155/2012/491604","DOIUrl":"https://doi.org/10.1155/2012/491604","url":null,"abstract":"Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR) involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes) has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88326140","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}
Theoretical analysis corresponding to the diffusion and kinetics of substrate and product in an amperometric biosensor is developed and reported in this paper. The nonlinear coupled system of diffusion equations was analytically solved by Homotopy perturbation method. Herein, we report the approximate analytical expressions pertaining to substrate concentration, product concentration, and current response for all possible values of diffusion and kinetic parameters. The numerical solution of this problem is also reported using Scilab/Matlab program. Also, we found excellent agreement between the analytical results and numerical results upon comparison.
{"title":"Analytical Expressions Pertaining to the Concentration of Substrates and Product in Phenol-Polyphenol Oxidase System Immobilized in Laponite Hydrogels: A Reciprocal Competitive Inhibition Process","authors":"K. Indira, Lakshmanan Rajendran","doi":"10.1155/2012/212818","DOIUrl":"https://doi.org/10.1155/2012/212818","url":null,"abstract":"Theoretical analysis corresponding to the diffusion and kinetics of substrate and product in an amperometric biosensor is developed and reported in this paper. The nonlinear coupled system of diffusion equations was analytically solved by Homotopy perturbation method. Herein, we report the approximate analytical expressions pertaining to substrate concentration, product concentration, and current response for all possible values of diffusion and kinetic parameters. The numerical solution of this problem is also reported using Scilab/Matlab program. Also, we found excellent agreement between the analytical results and numerical results upon comparison.","PeriodicalId":7371,"journal":{"name":"Advances in Physical Chemistry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78568954","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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