The behaviour of water structure-makers and breakers is of practical importance in protein folding in aqueous solution (G. Nemethy, Angew. Chem., Intl. Ed. Engl., 1967, 6, 195), but the mechanism for this process is not fully understood (K. A. T. Silverstein, A. D. J. Haymet and K. A. Dill, J. Am. Chem. Soc., 1998, 120, 3166). A computer simulation has been developed, of water structure around solutes, using only hydrogen bond geometry data rather than traditional forcefield methods. The simulation builds networks of hydrogen bonded water around structure-makers such as sulfate and phosphate, but not around structure-breakers such as urea and guanidinium. We have tested the software with a preliminary set of 17 varying solutes and our results are generally consistent with existing practical data
水结构制造者和破坏者的行为在水溶液中蛋白质折叠中具有实际意义(G. Nemethy, Angew.)。化学。, Intl。艾德,心血管病。(K. A. T. Silverstein, A. D. J. Haymet和K. A. Dill, J. Am.)。化学。Soc。， 1998, 120, 3166)。计算机模拟了溶质周围的水结构，只使用氢键几何数据，而不是传统的力场方法。该模拟在硫酸盐和磷酸盐等结构生成物周围构建了氢键水网络，但没有在尿素和胍等结构破坏物周围构建。我们对软件进行了17种不同溶质的初步测试，结果与现有的实际数据基本一致
{"title":"Geometry-based simulation of the hydration of small molecules","authors":"T. H. Plumridge, G. Steel, R. Waigh","doi":"10.1039/B003723K","DOIUrl":"https://doi.org/10.1039/B003723K","url":null,"abstract":"The behaviour of water structure-makers and breakers is of practical importance in protein folding in aqueous solution (G. Nemethy, Angew. Chem., Intl. Ed. Engl., 1967, 6, 195), but the mechanism for this process is not fully understood (K. A. T. Silverstein, A. D. J. Haymet and K. A. Dill, J. Am. Chem. Soc., 1998, 120, 3166). A computer simulation has been developed, of water structure around solutes, using only hydrogen bond geometry data rather than traditional forcefield methods. The simulation builds networks of hydrogen bonded water around structure-makers such as sulfate and phosphate, but not around structure-breakers such as urea and guanidinium. We have tested the software with a preliminary set of 17 varying solutes and our results are generally consistent with existing practical data","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"26 1","pages":"36-41"},"PeriodicalIF":0.0,"publicationDate":"2000-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85852101","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 concentration profiles of suspensions of cylindrical rods in a gravitational field are calculated within Onsager theory and its Parsons-Lee extension. The calculated profiles are very sensitive to the aspect ratio, for a given volume of the rods.
{"title":"Sedimentation equilibria of colloidal hard rod dispersions","authors":"R. Allen, D. Goulding, J. Hansen","doi":"10.1039/A905089B","DOIUrl":"https://doi.org/10.1039/A905089B","url":null,"abstract":"The concentration profiles of suspensions of cylindrical rods in a gravitational field are calculated within Onsager theory and its Parsons-Lee extension. The calculated profiles are very sensitive to the aspect ratio, for a given volume of the rods.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"33 1","pages":"30-33"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76225393","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}
Ab initio calculations of the excited state properties of a portion of the light harvesting 2 complex consisting of a supermolecule of two B850 bacteriochlorophyll (BChl), one B800 BChl, and one rhodopin glucoside carotenoid show significant mixing between the BChl and carotenoid states. Calculation of the B800–B850 coulombic coupling, through the transition density cube method, both with and without the carotenoid reveal that the carotenoid affects an increase in the B800–B850 coupling via an indirect (superexchange) mechanism. This carotenoid-mediated coupling explains a portion of the difference between the B800–B850 energy transfer rate determined experimentally and through traditional (Forster) calculations.
{"title":"Carotenoid mediated B800–B850 coupling in LH2","authors":"B. Krueger, G. Scholes, I. Gould, G. Fleming","doi":"10.1039/A903172C","DOIUrl":"https://doi.org/10.1039/A903172C","url":null,"abstract":"Ab initio calculations of the excited state properties of a portion of the light harvesting 2 complex consisting of a supermolecule of two B850 bacteriochlorophyll (BChl), one B800 BChl, and one rhodopin glucoside carotenoid show significant mixing between the BChl and carotenoid states. Calculation of the B800–B850 coulombic coupling, through the transition density cube method, both with and without the carotenoid reveal that the carotenoid affects an increase in the B800–B850 coupling via an indirect (superexchange) mechanism. This carotenoid-mediated coupling explains a portion of the difference between the B800–B850 energy transfer rate determined experimentally and through traditional (Forster) calculations.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"13 1","pages":"34-40"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87133754","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}
Qiao Chen, Chang-Woo Lee, D. Frankel, N. Richardson
Both R- and S-phenylglycine and a quantitatively well defined mixture of the two enantiomers have been studied on Cu{110} surfaces. At saturation coverage, the molecules form well ordered, chiral structures with a chiral unit cell which ensures that the LEED patterns of the two enantiomers are readily differentiated. Comparison is made with analogous structures observed for the non-chiral species glycine and R-, S-alanine adsorbed on Cu{110}.
在Cu{110}表面上研究了R-和s -苯基甘氨酸以及两种对映体的定量明确的混合物。在饱和覆盖下，分子形成有序的手性结构，具有手性单位细胞，确保两个对映体的LEED模式易于区分。并与Cu{110}吸附的非手性物质甘氨酸和R-， s -丙氨酸的类似结构进行了比较。
{"title":"The formation of enantiospecific phases on a Cu{110} surface","authors":"Qiao Chen, Chang-Woo Lee, D. Frankel, N. Richardson","doi":"10.1039/A905986E","DOIUrl":"https://doi.org/10.1039/A905986E","url":null,"abstract":"Both R- and S-phenylglycine and a quantitatively well defined mixture of the two enantiomers have been studied on Cu{110} surfaces. At saturation coverage, the molecules form well ordered, chiral structures with a chiral unit cell which ensures that the LEED patterns of the two enantiomers are readily differentiated. Comparison is made with analogous structures observed for the non-chiral species glycine and R-, S-alanine adsorbed on Cu{110}.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"9 1","pages":"41-44"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75039071","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}
R. Wüstneck, P. Enders, N. Wüstneck, U. Pison, R. Miller, D. Vollhardt
The stress relaxation process in spread dipalmitoyl phosphatidyl glycerol (DPPG) monolayers was investigated by using the pendant drop technique as a microfilm balance in combination with the axisymmetric drop shape analysis. The stress relaxation caused by a transient drop volume change was analysed by a new model, which takes into account material inhomogeneity by means of a distribution of relaxation γ. The surface pressure decay in the DPPG monolayers at 35 and 40 °C is governed by 2 main relaxation γ. One is of the order of 20 s, the other one is in the range of 200-600 s. The pi/A isotherms, the surface dilational modulus, and the higher relaxation γ are influenced by temperature and by the presence of electrolyte in the subphase; 0.15 mol dm-3 NaCl yields a smaller area demand per molecule in the monolayer. Harmonic oscillation experiments were carried out and the dilational elasticities and viscosities were determined for different frequencies in the range between the two main relaxation γ. Both, elasticities and viscosities, depend on frequency. The surface rheological behaviour is structural viscous, i.e. high viscosities at small frequencies, which decrease at faster deformations. The results are related to the surface dilational rheological behaviour of DPPC monolayers
{"title":"Surface dilational behaviour of spread dipalmitoyl phosphatidyl glycerol monolayers","authors":"R. Wüstneck, P. Enders, N. Wüstneck, U. Pison, R. Miller, D. Vollhardt","doi":"10.1039/A906516D","DOIUrl":"https://doi.org/10.1039/A906516D","url":null,"abstract":"The stress relaxation process in spread dipalmitoyl phosphatidyl glycerol (DPPG) monolayers was investigated by using the pendant drop technique as a microfilm balance in combination with the axisymmetric drop shape analysis. The stress relaxation caused by a transient drop volume change was analysed by a new model, which takes into account material inhomogeneity by means of a distribution of relaxation γ. The surface pressure decay in the DPPG monolayers at 35 and 40 °C is governed by 2 main relaxation γ. One is of the order of 20 s, the other one is in the range of 200-600 s. The pi/A isotherms, the surface dilational modulus, and the higher relaxation γ are influenced by temperature and by the presence of electrolyte in the subphase; 0.15 mol dm-3 NaCl yields a smaller area demand per molecule in the monolayer. Harmonic oscillation experiments were carried out and the dilational elasticities and viscosities were determined for different frequencies in the range between the two main relaxation γ. Both, elasticities and viscosities, depend on frequency. The surface rheological behaviour is structural viscous, i.e. high viscosities at small frequencies, which decrease at faster deformations. The results are related to the surface dilational rheological behaviour of DPPC monolayers","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"87 1","pages":"50-61"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89211648","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}
We discuss a sufficient condition for the determination of the angle parameter of the complex dilatation transformation that is often used for the location of dynamical resonances. We show, as one example, that the proposed condition yields the exact value of this angle parameter for the case of a harmonic potential. The formulation of the sufficient condition permits it to be used for general potentials. We illustrate the utility of the proposed method by calculating the location of the resonance supported by a potential introduced in a model study by Moiseyev, Certain and Weinhold. The results obtained are very close to, but more accurate than, those previously reported, and they are obtained with less computational effort.
{"title":"A sufficient condition for the angle parameter of the complex dilatation transformation","authors":"Meishan Zhao, S. Rice","doi":"10.1039/A900479C","DOIUrl":"https://doi.org/10.1039/A900479C","url":null,"abstract":"We discuss a sufficient condition for the determination of the angle parameter of the complex dilatation transformation that is often used for the location of dynamical resonances. We show, as one example, that the proposed condition yields the exact value of this angle parameter for the case of a harmonic potential. The formulation of the sufficient condition permits it to be used for general potentials. We illustrate the utility of the proposed method by calculating the location of the resonance supported by a potential introduced in a model study by Moiseyev, Certain and Weinhold. The results obtained are very close to, but more accurate than, those previously reported, and they are obtained with less computational effort.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"66 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81960462","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. Gleeson, T. Nuver, J. Lourenço, A. Moutinho, J. Los, A. Kleyn
We have measured the energy and angular distribution of the ions emitted from a perfluoropolyether liquid polymer surface due to an incident 320 eV Ar+ beam. The anion distributions are comprised almost exclusively of F?. Substantial amounts of high-energy F? recoils are produced, which can be attributed to multiple-collision processes. The production of these high-energy recoils indicates a very open surface structure, which allows hard (small impact parameter) collisions between Ar+ and individual functional groups of the polymer. Scattered Ar+ is only observed for small total scattering angles.
我们测量了320 eV Ar+束入射下全氟聚醚液体聚合物表面发射离子的能量和角分布。阴离子分布几乎完全由F?组成。大量的高能F?产生后坐力，这可归因于多次碰撞过程。这些高能后坐力的产生表明了一个非常开放的表面结构，这使得Ar+和聚合物的单个官能团之间的硬(小冲击参数)碰撞成为可能。散射Ar+仅在小的总散射角下观测到。
{"title":"Ion sputtering as a probe of liquid surfaces","authors":"M. Gleeson, T. Nuver, J. Lourenço, A. Moutinho, J. Los, A. Kleyn","doi":"10.1039/A907932G","DOIUrl":"https://doi.org/10.1039/A907932G","url":null,"abstract":"We have measured the energy and angular distribution of the ions emitted from a perfluoropolyether liquid polymer surface due to an incident 320 eV Ar+ beam. The anion distributions are comprised almost exclusively of F?. Substantial amounts of high-energy F? recoils are produced, which can be attributed to multiple-collision processes. The production of these high-energy recoils indicates a very open surface structure, which allows hard (small impact parameter) collisions between Ar+ and individual functional groups of the polymer. Scattered Ar+ is only observed for small total scattering angles.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"19 1","pages":"80-85"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85249084","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}
B. Shen, Y. Chun, J. Zhu, Ying Wang, Zhen‐Long Wu, J. Xia, Qin-hua Xu
Due to the interaction with support, KNO3 loaded on zeolite NaY began to decompose near 513 K, much lower than that unsupported. Through a special redox process, moreover, the KNO3 can be mainly decomposed at 673 K while the liberation of NOx is suppressed more than 90%.
{"title":"Environmentally benign decomposition of potassium nitrate on zeolites","authors":"B. Shen, Y. Chun, J. Zhu, Ying Wang, Zhen‐Long Wu, J. Xia, Qin-hua Xu","doi":"10.1039/A902666E","DOIUrl":"https://doi.org/10.1039/A902666E","url":null,"abstract":"Due to the interaction with support, KNO3 loaded on zeolite NaY began to decompose near 513 K, much lower than that unsupported. Through a special redox process, moreover, the KNO3 can be mainly decomposed at 673 K while the liberation of NOx is suppressed more than 90%.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"136 1","pages":"9-14"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79594790","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}
Hydrogen bonded complexes of formic acid with one and two molecules of water have been studied using multiconfigurational SCF and second-order perturbation theory (CASSCF/CASPT2). Equilibrium geometries in the ground electronic state, SO, and vertical S1�S0 transition energies have been calculated for the three 1 : 1 complexes, and four 1 : 2 conformers found. The most stable conformers are the six-membered ring structures for the 1 : 1 and 1 : 2 complexes in agreement with previous calculations. All vertical transitions are blue-shifted with respect to the corresponding monomer transition.
{"title":"Ab initio study of the π*â†n electronic transition in formic acid?(water)n (n = l, 2) hydrogen bonded complexes","authors":"G. Velardez, J. Heully, J. Beswick, J. Daudey","doi":"10.1039/A904105B","DOIUrl":"https://doi.org/10.1039/A904105B","url":null,"abstract":"Hydrogen bonded complexes of formic acid with one and two molecules of water have been studied using multiconfigurational SCF and second-order perturbation theory (CASSCF/CASPT2). Equilibrium geometries in the ground electronic state, SO, and vertical S1â†�S0 transition energies have been calculated for the three 1 : 1 complexes, and four 1 : 2 conformers found. The most stable conformers are the six-membered ring structures for the 1 : 1 and 1 : 2 complexes in agreement with previous calculations. All vertical transitions are blue-shifted with respect to the corresponding monomer transition.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"82 1","pages":"24-29"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74938136","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}
Dissipative particle dynamics simulations are presented of the self assembly of surfactant bilayers. The effect of changes in the chain length and stiffness of the surfactants on the properties of the model membranes are studied. We observe that changes of the stiffness have significant effects if these changes are made close to the head group of the surfactant. If, on the other hand, changes are made at the end of the tail of the surfactant, the properties of the bilayer are similar to the properties of a bilayer consisting of flexible chains.
{"title":"Simulating the self-assembly of model membranes","authors":"M. Venturoli, B. Smit","doi":"10.1039/A906472I","DOIUrl":"https://doi.org/10.1039/A906472I","url":null,"abstract":"Dissipative particle dynamics simulations are presented of the self assembly of surfactant bilayers. The effect of changes in the chain length and stiffness of the surfactants on the properties of the model membranes are studied. We observe that changes of the stiffness have significant effects if these changes are made close to the head group of the surfactant. If, on the other hand, changes are made at the end of the tail of the surfactant, the properties of the bilayer are similar to the properties of a bilayer consisting of flexible chains.","PeriodicalId":20106,"journal":{"name":"PhysChemComm","volume":"54 1","pages":"45-49"},"PeriodicalIF":0.0,"publicationDate":"1999-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80749209","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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