Pseudocontact shifts (PCS) generated by paramagnetic metal ions present valuable long-range information in the study of protein structural biology by nuclear magnetic resonance (NMR) spectroscopy. Faithful interpretation of PCSs, however, requires complete immobilization of the metal ion relative to the protein, which is difficult to achieve with synthetic metal tags. We show that two histidine residues in sequential turns of an α-helix provide a binding site for a Co ion, which positions the metal ion in a uniquely well-defined and predictable location. Exchange between the bound and free cobalt is slow on the timescale defined by chemical shifts, but the NMR resonance assignments are nonetheless readily transferred from the diamagnetic to the paramagnetic NMR spectrum by an I S -exchange experiment. The double-histidine-Co motif offers a straightforward, inexpensive, and convenient way of generating precision PCSs in proteins.

Pseudocontact shifts (PCS) generated by paramagnetic metal ions contribute highly informative long-range structure restraints that can be measured in solution and are ideally suited to guide structure prediction algorithms in determining global protein folds. We recently demonstrated that PCSs, that are relatively small but of high quality, can be generated by a double histidine (dHis) motif in an -helix, which provides a well-defined binding site for a single Co 2+ ion. Here we show that PCSs of backbone amide protons generated by dHis-Co 2+ motifs positioned in four different -helices of a protein deliver excellent restraints to determine the three-dimensional (3D) structure of a protein in a way akin to the global positioning system (GPS). We demonstrate the approach with GPS-Rosetta calculations of the 3D structure of the C-terminal domain of the chaperone ERp29 (ERp29-C). Despite the relatively small size of the PCSs generated by the dHis-Co 2+ motifs, the structure calculations converged readily. Generating PCSs by the dHis-Co 2+ motif thus presents an excellent alternative to the use of lanthanide tags.

The aim of this work was to prepare novel electrospun polystyrene (PS) nanofibrous samples functionalization with acrylamide monomer (AAm) as promising nanoadsorbents by the use of nitrogen gas plasma. To investigate the performance evaluation of the samples for adsorbing cadmium (Cd2+) and nickel (Ni2+) ions, a series of tests in terms of ATR‐FTIR spectroscopy, FE‐SEM, water contact angle (WCA) measurements and atomic adsorption spectroscopy were carried out. The ATR‐FTIR results showed that nitrogen (N2) plasma was an efficient tool because of the formation of functionalized AAm‐PS nanofibrous samples by providing amide (−NCO) and amine (−NH−) groups onto their surfaces. The WCA measurements demonstrated that the N2 plasma‐modified samples in the presence of AAm had a lower contact angle of 42.8º than the other samples. Moreover, FE‐SEM micrpgraph images of AAm‐treated PS nanofibrous samples indicated that approperiate amount of the functional groups onto the samples surfaces were deposited. Afterwards, AAS analysis along with Langmuir and Freundlich's isotherm models revealed that a high adsorption of the ions was occurred at pH 5 in the order Cd2+ (10 mg g−1) > Ni2+ (4.9 mg g−1) by using the nanoadsorbents dosage 1 g L−1 and the metal ions concentration 25 mg L−1. In addition, the obtained results exhibited the Cd2+ and Ni2+ ions removal efficiencies (%R) were increased up to 96% and 94%, respectively with raising the nanoadsorbents dosage. Moreover, the equilibrium adsorption of the ions showed the best fitting by the Freundlich's model. Finally, the desorption of the optimized samples for regenerating them owing to the effective removal of the ions has been confirmed by applying the recyclability test. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42944.

Pseudocontact shifts (PCS) generated by paramagnetic metal ions present valuable long-range information in the study of protein structural biology by nuclear magnetic resonance (NMR) spectroscopy. Faithful interpretation of PCSs,h owever,r equires complete immobilization of the metal ion relative to the protein, which is difficult to achieve with synthetic metal tags.Weshowthat two histidine residues in sequential turns of an a-helix provide abinding site for aCo 2+ ion, whichp ositions the metal ion in au niquely well-defined and predictable location. Exchange between the bound and free cobalt is slow on the timescale defined by chemical shifts, but the NMR resonance assignments are nonetheless readily transferred from the diamagnetic to the paramagnetic NMR spectrum by an I z S z -exchange experiment. The double-histidine-Co 2+ motif offers as traightforward, inexpensive,a nd convenient wayofg enerating precision PCSs in proteins.

Super tough polyamide 6 was prepared by using SEBS and effect of SEBS-g-MA as a compatibilizer of PA6/SEBS matrix on mechanical properties was investigated. Thus super tough polyamide 6/graphene nanocomposites were produced using graphene nanosheets (GNs) through the melt compounding method. To compare the effectiveness of graphene, effects of graphite and carbon black (the other carbon structures) are also studied on the same matrix. The effects of graphene on crystallinity, improvements of morphology, and thermal and electrical properties of the nanocomposites were researched and compared with similar samples of graphite and carbon black. Due to the reaction between the maleic anhydride groups of SEBS and amine groups of nylon chains during the melt mixing process, super tough polyamide 6 was produced with high impact and tensile strength. The most important results of this study can be noted as an increase in the electrical conductivity and thermal stability by adding graphene to PA6/SEBS blend. Also the effect of graphene compatibility on PA6/SEBS/SEBS-g-MA blend was investigated with studying morphology.