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Scalar couplings are a fundamental aspect of nuclear magnetic resonance (NMR) experiments and provide rich information about electron-mediated interactions between nuclei. 3 J couplings are particularly useful for determining molecular structure through the Karplus relationship, a mathematical formula used for calculating 3 J coupling constants from dihedral angles. In small molecules, scalar couplings are often determined through analysis of one-dimensional proton spectra. Larger proteins have typically required specialized multidimensional pulse programs designed to overcome spectral crowding and multiplet complexity. Here we present a generalized framework for fitting scalar couplings with arbitrarily complex multiplet patterns using a weak coupling model. The method is implemented in FitNMR and applicable to 1D, 2D, and 3D NMR spectra. To gain insight into the proton-proton coupling patterns present in protein side chains, we analyze a set of isolated amino acid 1D spectra. We show that the weak-coupling assumption is largely sufficient for fitting the majority of resonances, although there are notable exceptions. To enable structural interpretation of all couplings, we extend a self-consistent Karplus parameterization of side chain chi 1 to chi 2–4. An enhanced model of side chain motion incorporating rotamer statistics from the Protein Data Bank (PDB) is developed. Even without stereospecific assignments of the beta hydrogens, we find that two couplings are sufficient to exclude a single-rotamer model for all amino acids except proline. While most isolated amino acids show rotameric populations consistent with crystal structure statistics, beta-branched valine and isoleucine deviate substantially. [ABSTRACT FROM AUTHOR]

In recent years the road surface conditions in Pakistan have been getting worse day by day, like rutting, thermal cracking and increased resistance to many forms of traffic-induced stress can be seen. There should be more concern about durability. Polymer modification of bitumen has become the optimal technique in designing better performance of pavements. Working with polymer modified bitumen is an excellent solution to this and a lot of work with various polymers has either been done or in the pipeline. The advantage of polymer modification of bitumen is that offers enhancements in performance and durability, qualifying of pavement distress and reduced life cycle costs when it is differentiated to unmodified bitumen or hot mix bitumen surface dressings. This study considers the sustainable pavement method when recycled rubber is taken from window fittings in crumbed form is mixed with a hot bitumen mixture. The main objective was to inspect the impact of adding recycled crumbed rubber to the bitumen mixture. The dry process method was used in which four different crumb rubber contents (1%, 3%, 5% and 7% wt.) in the asphalt mixture were investigated. The working temperatures to mix the crumbed rubber in the hot bitumen were around 180 °C-190 °C. Considering the Marshall stability esteem and the volumetric properties, acomparative study was done amongst the unmodified bituminous mixture and whole bituminous concrete mixtures. The results introduced that crumb rubber is an added substance in the asphalt mixture, as all the results are inside the normal pre requisites. The crumb rubber addition to the asphalt mixture would loseits strength and quality. It would be more worried about the sturdiness of the asphalt mixture since the crumb rubber in asphalt content changed its properties and can be utilized in additional exploration. [ABSTRACT FROM AUTHOR]