@article {2591, title = {An evaluation of exchange-correlation functionals for the calculations of the ionization energies for atoms and molecules}, journal = {Journal of Electron Spectroscopy and Related Phenomena}, volume = {171}, number = {1-3}, year = {2009}, note = {ISI Document Delivery No.: 452BQTimes Cited: 6Cited Reference Count: 82Segala, Maximiliano Chong, Delano P.}, month = {Apr}, pages = {18-23}, type = {Article}, abstract = {In this paper, ionization energies of gas-phase atoms and molecules are calculated by energy-difference method and by approximate transition-state models with density functional theory (DFT). To determine the best functionals for ionization energies, we first study the H to Ar atoms. An approximation is used in which the electron density is first obtained from Kohn-Sham computations with an exchange-correlation potential V-xc known as statistical average of orbital potentials (SAOP), after which the energy is computed from that density with 59 different exchange-correlation energy functionals E-xc. For the 18 atoms, the best E-xc functional providing an average absolute deviation (AAD) of only 0.110 eV is one known as the Krieger-Chen-lafrate-Savin functional modified by Krieger, Chen, Iafrate, and Kurth, if one uses the spin-polarized spherical atom description. On the other hand, if one imposes the condition of integer-electrons, the best functional is the Becke 1997 functional modified by Wilson, Bradley, and Tozer, with an AAD of 0.107 eV, while several other functionals perform almost as well. For molecules, we can achieve an accuracy of AAD = 0.21 eV for valence VIPs of nonperhalo molecules with Delta E(V-xc = SAOP;PBEO) using integer-electron description. For perhalo molecules our best approach is Delta E(V-xc from either E-xc or SAOP;mPW1PW) with full symmetry to obtain an AAD = 0.24 eV. (c) 2009 Elsevier B.V. All rights reserved.}, keywords = {ADJUSTABLE-PARAMETERS, ASYMPTOTIC-BEHAVIOR, DFT, Energy-difference method, EXCITATION-ENERGIES, GENERALIZED GRADIENT APPROXIMATION, HE(II) PHOTOELECTRON-SPECTRA, Integer-electron, Ionization energy, models, ORBITAL MODEL POTENTIALS, ORGANIC-MOLECULES, PHOTO-ELECTRON SPECTRA, Slater-type orbitals, Spin-polarized spherical atom, STATISTICAL AVERAGE, TRANSITION-STATE}, isbn = {0368-2048}, url = {://000266515000002}, author = {Segala, M. and Chong, D. P.} } @article {2149, title = {Configurational entropy modulates the mechanical stability of protein GB1}, journal = {Journal of Molecular Biology}, volume = {379}, number = {4}, year = {2008}, note = {ISI Document Delivery No.: 314NITimes Cited: 10Cited Reference Count: 39Li, Hongbin Wang, Hui-Chuan Cao, Yi Sharma, Deepak Wang, Meijia}, month = {Jun}, pages = {871-880}, type = {Article}, abstract = {Configurational entropy plays important roles in defining the thermodynamic stability as well as the folding/unfolding kinetics of proteins. Here we combine single-molecule atomic force microscopy and protein engineering techniques to directly examine the role of configurational entropy in the mechanical unfolding kinetics and mechanical stability of proteins. We used a small protein, GB1, as a model system and constructed four mutants that elongate loop 2 of GB1 by 2, 5, 24 and 46 flexible residues, respectively. These loop elongation mutants fold properly as determined by far-UV circular dichroism spectroscopy, suggesting that loop 2 is well tolerant of loop insertions without affecting GB1{\textquoteright}s native structure. Our single-molecule atomic force microscopy results reveal that loop elongation decreases the mechanical stability of GB1 and accelerates the mechanical unfolding kinetics. These results can be explained by the loss of configurational entropy upon closing an unstructured flexible loop using classical polymer theory, highlighting the important role of loop regions in the mechanical unfolding of proteins. This study not only demonstrates a general approach to investigating the structural deformation of the loop regions in mechanical unfolding transition state, but also provides the foundation to use configurational entropy as an effective means to modulate the mechanical stability of proteins, which is of critical importance towards engineering artificial elastomeric proteins with tailored nanomechanical properties. (C) 2008 Elsevier Ltd. All rights reserved.}, keywords = {configurational entropy, DISULFIDE BONDS, FORCE, FORCE SPECTROSCOPY, FRAGMENT RECONSTITUTION, IMMUNOGLOBULIN BINDING DOMAIN, length, LOOP, MECHANICAL STABILITY, mechanical unfolding, MODULES, resistance, single molecule atomic force microscopy, SINGLE PROTEIN, SPECTROSCOPY, TITIN, TRANSITION-STATE}, isbn = {0022-2836}, url = {://000256815700018}, author = {Li, H. B. and Wang, H. C. and Cao, Y. and Sharma, D. and Wang, M.} } @article {5161, title = {Bridging the gap between proteins and nucleic acids: A metal-independent RNAseA mimic with two protein-like functionalities}, journal = {Journal of the American Chemical Society}, volume = {123}, number = {8}, year = {2001}, note = {ISI Document Delivery No.: 405LXTimes Cited: 74Cited Reference Count: 49}, month = {Feb}, pages = {1556-1563}, type = {Article}, abstract = {Two synthetically modified nucleoside triphosphate analogues (adenosine modified with an imidazole and uridine modified with a cationic amine) are enzymatically polymerized in tandem along a degenerate DNA library for the combinatorial selection of an RNAse A mimic. The selected activity is consistent with both electrostatic and general acid/base catalysis at physiological pH in the absence of divalent metal cations. The simultaneous use of two modified nucleotides to enrich the catalytic repertoire of DNA-based catalysts has never before been demonstrated and evidence of general acid/base catalysis at pH 7.4 for a DNAzyme has never been previously observed in the absence of a divalent metal cation or added cofactor, This work illustrates how the incorporation of protein-like functionalities in nucleic acids can bridge the gap between proteins and oligonucleotides underscoring the potential for using nucleic acid scaffolds in the development of new materials and improved catalysts for use in chemistry and medicine.}, keywords = {5{\textquoteright}-TRIPHOSPHATES, ADENOSINE, ANALOG, CATALYSIS, CLEAVAGE, CLEAVING DNA ENZYME, DERIVATIVES, IN-VITRO SELECTION, PHOSPHORYL-TRANSFER-REACTIONS, PORPHYRIN METALATION, TRANSITION-STATE}, isbn = {0002-7863}, url = {://000167162100002}, author = {Perrin,David M. and Garestier, T. and Helene, C.} }