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Joint failure, which causes leakage in bridge decks as well as deterioration in girders and substructures, is one of the most common concerns in highway bridges. Therefore, link slabs have been considered as a preventive maintenance method in eliminating these joints. This paper presents a pilot project that constructed the link slab system in Maryland, U.S., with modified bearings to improve its durability and reduce maintenance costs. Compared with the traditional bearing replacement design for the link slab systems, this project proposes a more economical method by removing the anchor bolts and restricting sliding plates of the fixed bearings at both abutments to match the designed boundary conditions while avoiding the high cost of jacking girders and replacing bearings. Furthermore, numerical analysis and structural health monitoring were conducted and validated to investigate the effectiveness of the link slab design with various high performance concrete materials. After the one-year monitoring period, the link slab system is verified to be in fully functional condition and the bearing modification design is verified to be effective.

The binding mode of a conformationally locked NC(O)N planar system with deoxyribonucleic acid (DNA) is investigated using various spectroscopic and enzymatic assays. Compound 1 and its four different salts (comp. 2-5) were prepared for this purpose. They showed certain changes in their respective DNA-compound complex at ground state and excited state as measured by UV-vis and fluorescence emission spectra. The Stern-Volmer quenching constant (KSV) for the neutral species (1) is found 8545 M(-1), whereas, for its salts 2, 3, 4 and 5 the quenching constants were 33510 M(-1), 11352 M(-1), 19693 M(-1) and 27270 M(-1) respectively. Nevertheless, the binding constant values remain comparable in neutral and salt forms except for 5. To elucidate the reason we took their CD spectra and ran a topoisomerase I (Topo I) assay. These experimental data revel the fact that compound 1 (neutral form) binds at the minor groove of DNA, whereas, its salt (2) has an extended intercalating property.

Because Congo red (CR) can bind to critical intermediate structural forms of amyloid beta (Aβ), it has been suggested as a potential therapeutic agent against neurodegenerative disorders such as Alzheimer’s disease. In this study, the interaction of CR with Aβ12–28 was investigated by use of isothermal titration calorimetry (ITC). Studies conducted between 15 and 35 °C show that binding of CR to Aβ12–28 was strongly dependent on temperature, with a decrease in CR–Aβ12–28 complexation as temperature increases, presumably because of conformational changes within Aβ12–28 at the highest temperatures, that conceal the CR binding sites. In fact, no CR binding was observed at 35 °C. The binding of CR to Aβ12–28 was associated with favorable changes in both enthalpy and entropy that resulted in binding constants (K) of between 105 and 106 M −1. An early (and more intense) entropy-driven CR disaggregation phase (K ~107–108 M −1) was observed before the onset of CR–Aβ12–28 complexation. Only CR disaggregation was observed at 35 °C. These results may provide further insights into the ability of CR to inhibit Aβ toxicity in neurodegenerative diseases.

Thermodynamic properties of complexes of Congo Red (CR) dye with amyloid  (A) peptides were studied by both absorption spectroscopy and isothermal titration calorimetry (ITC). Based on the absorption spectrum for the formation of CR-Aβ complexes in phosphate buffered saline solution (pH 7.4), van’t Hoff plots over a temperature range of 10oC to 70oC were created for CR-Aβ1-40, -Aβ12-28, and -Aβ1-42. The plot for CRAβ12-28 complex showed a relatively linear feature within the given temperature range with H = –10.1 0.6 kJ/mol and S = + 0.128  0.002 kJ/(mol K). However, the plot for CR-Aβ1-40 and CR-Aβ1-42 complexes exhibited two distinct linear regions with opposite slopes centered at a specific temperature, Ts, which was 54.7  0.2℃ and 34.8  0.2℃, respectively. The ITC experiments conducted at 25℃in water exhibited quite a different situation from the above mentioned spectroscopic approach. The ITC studies yielded a H of –85.3  0.2 kJ/mol for the CR-Aβ12-28 complex with negative entropy change –0.152 kJ/mol K). For CR-Aβ1-40, the ITC studies indicated the presence of two binding sites with H1 = –81.8  0.3 kJ/mol and H2 = –119.5  0.2 kJ/mol with K1 = 5.5  0.7  10 6 M -1 and K2 = 6.9  2.4  10 8 M -1 , respectively. These binding constants are consistent with the model suggested by several studies. Both binding sites showed negative entropy changes suggesting that the formation of the complex is enthalpically driven. The disagreement in thermochemical values between two different methods confirmed that the enthalpy and entropy are heavily dependent on temperature and buffer/salt environment, and may involve inherently different reaction paths.

A series of thio- and selenopyrylium analogues of 2,4-di(4-dimethylaminophen-yl)-6-methylthiopyrylium iodide were prepared in five steps from 4-dimethylaminophenyl-propargyl aldehyde and the corresponding lithium acetylide. When bound to DNA, all of the dyes absorb at wavelengths >600 nm, which avoids the hemoglobin band I maximum at 575 nm. The binding of the series of dyes to double-stranded DNA was examined spectrophotometrically and by isothermal titration calorimetry to determine binding constants, by a topoisomerase I DNA unwinding assay, by competition dialysis with [poly(dGdC)] 2 and [poly(dAdT)] 2 , and by ethidium bromide displacement studies to examine propensities for intercalation, and by circular dichroism studies. The dyes were found to show mixed binding modes.

A topoisomerase I DNA unwinding assay has been used to determine the relative DNA-binding affinities of a model pair of homologous naphthalene diimides. Binding affinity data were corroborated using calorimetric (ITC) and spectrophotometric (titration and Tm) studies, with substituent size playing a significant role in binding. The assay was also used to investigate the mode of binding adopted by several known DNA-binding agents, including SYBR Green and PicoGreen. Some of the compounds exhibited unexpected binding modes.

The DNA binding characteristics of a series of homologous 2,6-disubstituted anthraquinone threading intercalators bearing one to four ethylene glycol units in their side chains have been studied. Binding constants were measured via surface plasmon resonance (SPR). These compounds bind to an AT-rich hairpin with slightly higher affinity than to a GC-rich hairpin. The binding constants decrease as the length of the side chain increases.

© 2013 McKnight, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Insights into the Relative DNA Binding Affinity and Preferred Binding Mode of Homologous Compounds Using Isothermal Titration Calorimetry (ITC)

Insights into the Relative DNA Binding Affinity and Preferred Binding Mode of Homologous Compounds Using Isothermal Titration Calorimetry (ITC)

A combination of isothermal titration calorimetry (ITC), topoisomerase I DNA unwinding assays, and ethidium bromide displacement studies were employed to investigate the binding of a homologous series of naphthalene diimides (NDI) to DNA. Our results suggest that the nature of the substituent plays a significant role in both the preferred binding mode and relative binding affinity of the compounds of this study. Only intercalative-type binding (K=15±3×10(6)M(-1)) was observed for the NDI with the smallest substituent (trimethyl-ethylamino), while larger members of the series (diethylmethyl-, dipropylmethyl- and dibutylmethyl-ethylamino substituents) adopted an additional binding mode of higher affinity (K(1)=31-78×10(6)M(-1)).

The DNA binding efficacy and preferred mode of binding of a series of rhodamine-related chalcogenoxanthylium dyes was investigated by isothermal titration calorimetry (ITC) using ctDNA, [poly(dCdG)] 2 and [poly(dAdT)] 2 , and by a topoisomerase I DNA unwinding (Topo I) assay. The dyes of this study showed tight binding to ctDNA with binding constants, K b , on the order of 10 6 –10 7 M −1 . The ITC and Topo I assay studies suggested that the 9-substituent has a strong impact on binding modes ranging from an apparent preference for intercalation with a 9-2-thienyl substituent (similar binding to [poly(dCdG)] 2 and [poly(dAdT)] 2 , re-supercoiling of DNA in the Topo I assay at −5 M dye), to mixed binding modes with 9-phenyl derivatives (2- to 3-fold preference for binding to [poly(dAdT)] 2 , re-supercoiling of DNA in the Topo I assay at ∼2 × 10 −5 M dye), to minor groove binding in a 9-(2-thienyl-5-diethylcarboxamide) derivative (strong preference for binding to [poly(dAdT)] 2 , did not show complete re-supercoiling in the Topo I assay). No binding to ctDNA was observed in one derivative with a 9-(3-thienyl-2-diethylcarboxamide) substituent, which cannot be co-planar with the xanthylium core. In series of dyes where the chalcogen atom was varied, the selenoxanthylium derivatives had 2- to 3-fold higher values of K b than the corresponding xanthylium, thioxanthylium, or telluroxanthylium derivatives, which all showed comparable values of K b . The chalcogen atom appeared to have little influence on binding mode.

The "View now" link directs to the finding aid only. Please email wvrhcref@mail.wvu.edu or call 304-293-3536 for more information about accessing collection A&M 3461 Ruel Foster, Professor of English, Papers, 1906-2000. Papers of Ruel Foster, a former professor of English and Chairman of the English Department, West Virginia University. Includes material related to author Thomas Wolfe (box 6); an extensive series of correspondence with acclaimed Appalachian writer Jesse Stuart (boxes 1-3 and 8); and letters from Helen Pancake, mother of Breece D'J Pancake (box 6). Also includes records related to the publication of Foster's book on Jesse Stuart in Twayne's United States Author Series, a photographic portrait of Jesse Stuart, and other records related to Stuart. There is also a manuscript by author Davis Grubb of his stage adaptation of his novel "The Night of the Hunter" with signed manuscript cover letter to Foster by Grubb discussing this adaptation, with reference to actress Lillian Gish.