Group Contributions (group + contribution)

Distribution by Scientific Domains

Terms modified by Group Contributions

  • group contribution method

  • Selected Abstracts


    Genome-wide Characterization of Long Terminal Repeat -retrotransposons in Apple Reveals the Differences in Heterogeneity and Copy Number between Ty1 -copia and Ty3 -gypsy Retrotransposons

    JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2008
    Hai-Yue Sun
    Abstract The conserved domains of reverse transcriptase (RT) genes of Ty1- copia and Ty3- gypsy groups of long terminal repeat (LTR) retrotransposons were isolated from the Malus domestica genome using degenerate oligonucleotide primers. Sequence analysis showed that 45% of Ty1- copia and 63% of Ty3- gypsy RT sequences contained premature stop codons and/or indels disrupting the reading frame. High heterogeneity among RT sequences of both Ty1- copia and Ty3- gypsy group retrotransposons was observed, but Ty3- gypsy group retrotransposons in the apple genome are less heterogeneous than Ty1- copia elements. Retrotransposon copy number was estimated by dot blot hybridizations for Ty1- copia (,5 000) and Ty3- gypsy (,26 000). All elements of the two types of LTR retrotransposons comprise approximately 38% of the M. domestica genome, with the Ty3- gypsy group contribution being higher (33.5%) than the Ty1- copia one (4.6%). Transcription was not detected by reverse transcription-polymerase chain reaction for either Ty1- copia or Ty3- gypsy retrotransposons in the leaves of plants in vitro or in leaf explants cultured on medium supplemented with high concentration benzylaminopurine. This research reveals the differences in heterogeneity and copy number between Ty1- copia and Ty3- gypsy retrotransposons in the apple genome. Ty1- copia retrotransposon has higher heterogeneity than Ty3- gypsy retrotransposon, but the latter has a higher copy number, which implies that Ty3- gypsy retrotransposons may play a more important role in the apple genome evolution. [source]


    Effect of sulfonic group on solubility parameters and solubility behavior of poly(2,6-dimethyl-1,4-phenylene oxide)

    POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2007
    Chunli Gong
    Abstract An investigation on the effect of sulfonic group on solubility parameters and solubility behavior of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is presented. Sulfonated PPO (SPPO) was prepared using chlorosulfonic acid as a sulfonating agent. The structure of SPPO was confirmed by FT-IR, and the ion exchange capacity (IEC) of SPPO was accurately determined by conductometric titration and 1H-NMR. The three-dimensional solubility parameters of SPPO defined by Hansen were estimated by group contribution, and this approach was used to obtain the three coordinates of a solubility parameter in terms of: a dispersion part ,d, a polar part ,p and a hydrogen bonding part ,h. The theoretical predications of solubility behavior were characterized using "soluble sphere" in three-dimensional space. The estimated results were in accordance with the solubility experiments in different solvents. Copyright © 2006 John Wiley & Sons, Ltd. [source]


    Molar group contributions to the heat of combustion,

    FIRE AND MATERIALS, Issue 3 2002
    Richard N. Walters
    Experimental results for the gross heat of combustion of over 140 commercial and developmental polymers and small molecules of known chemical structure were used to derive additive molar group contributions to the heat of combustion. The materials examined contained carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, chlorine, fluorine and silicon in linear, branched and cyclic structures. Values for the molar group contributions were summed and divided by the molecular weight of the molecule or polymer repeat unit to yield the gross heat of combustion as determined by oxygen bomb calorimetry. This new method provides an accurate single step method for calculating the heat of combustion. The average relative error of the calculated gross heats of combustion is 2.8%. Published in 2002 by John Wiley & Sons, Ltd. [source]


    Group contribution prediction of surface charge density profiles for COSMO-RS(Ol)

    AICHE JOURNAL, Issue 12 2007
    Tiancheng Mu
    Abstract A new method for predicting the surface charge density distribution (, profile) and cavity volume of molecules based on group contributions was developed. The original , profiles used for the regression were obtained using Gaussian 03 B3LYP/6-311G(d,p). In total 1363 , profiles were used for the regression of group parameters. Group definitions are identical to those used previously for boiling point estimation. Original and estimated , profiles were used to predict activity coefficients at infinite dilution and VLE data of binary systems using the COSMO-RS(Ol) model. The results were compared with the experimental data stored in the Dortmund Data Bank. In many cases the results were of comparable accuracy. However, for a few compounds, poor results were obtained, in particular for conjugated components like nitrobenzenes. The method offers a fast and reliable generation of , profiles to be used with COSMO-RS(Ol) within its range of applicability. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]


    Classical QSAR Modeling of Anti-HIV 2,3-Diaryl-1,3-thiazolidin-4-ones

    MOLECULAR INFORMATICS, Issue 5 2005
    Kunal Roy
    Abstract Cytoprotection and cytotoxicity data of anti-HIV 2,3-diaryl-1,3-thiazolidin-4-ones were subjected to QSAR study using Fujita-Ban type analysis and a mixed approach based on Hansch and Fujita-Ban analyses. Apart from appropriate indicator and integer variables encoding different group contributions, different physicochemical variables like hydrophobicity (,) and steric (molar refractivity) parameters of aryl ring substituents of the compounds were used as predictor variables. Furthermore, Wang-Ford charges of the common atoms of the compounds calculated from molecular electrostatic potential surface of AM1 optimized geometries of the compounds and various topological parameters were used as additional descriptors. The variables for the multiple regression analyses were selected based on principal component factor analysis, and generated equations were statistically validated using leave-one-out technique and predicting the activity data of test set compounds. The statistical qualities of the equations for cytoprotection data (explained variance ranging 64.5,80.3%, leave-one-out predicted variance ranging 44.3,59.4%) are better than those for cytotoxicity data (explained variance ranging 59.7,60.6%, leave-one-out predicted variance ranging 52.4,54.4%). The analysis explores the structural and physicochemical requirements of the compounds for cytoprotection and cytotoxicity. [source]


    Classical QSAR Modeling of CCR5 Receptor Binding Affinity of Substituted Benzylpyrazoles

    MOLECULAR INFORMATICS, Issue 6 2004
    Thomas Leonard
    Abstract CCR5 receptor binding affinity of a series of substituted benzylpyrazole derivatives was subjected to QSAR study using Fujita-Ban type analysis and a mixed approach based on Hansch and Fujita-Ban analyses. Apart from appropriate indicator variables encoding different group contributions, different physicochemical variables like hydrophobicity (,), electronic (Hammett ,) and steric (molar refractivity, STERIMOL values) parameters of phenyl ring substituents of the benzyl moiety of the compounds were used as predictor variables. Additionally, Wang-Ford charges of the common atoms of the compounds calculated from molecular electrostatic potential surface of AM1 optimized geometries of the compounds and various topological parameters were used as additional descriptors. The variables for the multiple regression analyses were selected based on principal component factor analysis and generated equations were statistically validated using leave-one-out technique and predicting the binding affinities of test set compounds. The analysis explores the substitutional requirements of the phenyl nucleus of the benzylpyrazole moiety of the compounds for effective binding with CCR5 receptor. [source]


    TORT DECISIONS AND CAMPAIGN DOLLARS

    POLITICS & POLICY, Issue 2 2000
    Eric N. Waltenburg
    There has recently been growing concern over the massive infusion of special interest dollars in state judicial elections. Commentators worry that these contributions may undermine the public's confidence in the operation and impartiality of the judicial system, or worse, "buy" the decision of the successful judicial candidate. The purpose of this analysis is to determine the extent to which there is good cause to worry. It examines contribution patterns for, and the decisional behavior of, the state supreme court justices on the Alabama, Kentucky, and Ohio courts who have had electoral contests in the 1990s. Results indicate that worries over the American bench being "for sale" have some traction. Under electoral pressures, the justices do appear to position themselves to appeal more to their contributors. This effect is not enduring, however. Whatever relationships exist between contributions to judicial candidates and their decisional behavior are short-term. Following his or her election, a justice's decision-making shows no signs of being influenced by interest group contributions. [source]