Investigation of Ni2MnAl-based shape memory alloys

In this thesis, crystallographic, magnetic and elastic properties of Ni2MnAl based shape memory alloys have been investigated. Crystallographic investigations of the completely disordered Ni2Mn1.2Alo.8 have been carried out using neutron diffraction. The structure of the high temperature phase has been determined. A tool for approaching solutions of triclinic unit cell symmetries has been developed and applied on the experimental results of the low temperature phase. The analysis suggests structural contributions of monoclinic symmetry. Magnetic properties of completely disordered Ni2MnxAl2_x for x = 1.0, 1.1, ..., 1.4 have been investigated at temperatures of 5K 350K and magnetic fields up to 5T. Strain-stress measurements have been carried out on Ni2Mni.2Al0.8- Young’s modulus has been determined for the temperatures T — 25°C, 75°C and 125°C.  </p

Great Offset Difference Internuclear Selective Transfer

Carbon–carbon dipolar recoupling sequences are frequently used building blocks in routine magic-angle spinning NMR experiments. While broadband homonuclear first-order dipolar recoupling sequences mainly excite intra-residue correlations, selective methods can detect inter-residue transfers and long-range correlations. Here, we present the great offset difference internuclear selective transfer (GODIST) pulse sequence optimized for selective carbonyl or aliphatic recoupling at fast magic-angle spinning, here, 55 kHz. We observe a 3- to 5-fold increase in intensities compared with broadband RFDR recoupling for perdeuterated microcrystalline SH3 and for the membrane protein influenza A M2 in lipid bilayers. In 3D (H)COCO(N)H and (H)CO(CO)NH spectra, inter-residue carbonyl–carbonyl correlations up to about 5 Å are observed in uniformly 13C-labeled proteins

Sensitivity-Enhanced Four-Dimensional Amide–Amide Correlation NMR Experiments for Sequential Assignment of Proline-Rich Disordered Proteins

Proline is prevalent in intrinsically disordered proteins (IDPs). NMR assignment of proline-rich IDPs is a challenge due to low dispersion of chemical shifts. We propose here new sensitivity-enhanced 4D NMR experiments that correlate two pairs of amide resonances that are either consecutive (NH_<i>i</i>–1, NH_<i>i</i>) or flanking a proline at position <i>i</i>–1 (NH_<i>i</i>–2, NH_<i>i</i>). The maximum 2-fold enhancement of sensitivity is achieved by employing two coherence order-selective (COS) transfers incorporated unconventionally into the pulse sequence. Each COS transfer confers an enhancement over amplitude-modulated transfer by a factor of √2 specifically when transverse relaxation is slow. The experiments connect amide resonances over a long fragment of sequence interspersed with proline. When this method was applied to the proline-rich region of B cell adaptor protein SLP-65 (pH 6.0) and α-synuclein (pH 7.4), which contain a total of 52 and 5 prolines, respectively, 99% and 92% of their nonprolyl amide resonances have been successfully assigned, demonstrating its robustness to address the assignment problem in large proline-rich IDPs

Interdomain Dynamics Explored by Paramagnetic NMR

An ensemble-based approach is presented to explore the conformational space sampled by a multidomain protein showing moderate interdomain dynamics in terms of translational and rotational motions. The strategy was applied on a complex of calmodulin (CaM) with the IQ-recognition motif from the voltage-gated calcium channel Ca_v1.2 (IQ), which adopts three different interdomain orientations in the crystal. The N60D mutant of calmodulin was used to collect pseudocontact shifts and paramagnetically induced residual dipolar couplings for six different lanthanide ions. Then, starting from the crystal structure, pools of conformations were generated by free MD. We found the three crystal conformations in solution, but four additional MD-derived conformations had to be included into the ensemble to fulfill all the paramagnetic data and cross-validate optimally against unused paramagnetic data. Alternative approaches led to similar ensembles. Our “ensemble” approach is a simple and efficient tool to probe and describe the interdomain dynamics and represents a general method that can be used to provide a proper ensemble description of multidomain proteins

Simplified Preservation of Equivalent Pathways Spectroscopy

Inspired by the recently proposed transverse mixing optimal control pulses (TROP) approach for improving signal in multidimensional magic-angle spinning (MAS) NMR experiments, we present simplified preservation of equivalent pathways spectroscopy (SPEPS). It transfers both transverse components of magnetization that occur during indirect evolutions, theoretically enabling a √2 improvement in sensitivity for each such dimension. We compare SPEPS transfer with TROP and cross-polarization (CP) using membrane protein and fibril samples at MAS of 55 and 100 kHz. In three-dimensional (3D) (H)CANH spectra, SPEPS outperformed TROP and CP by factors of on average 1.16 and 1.69, respectively, for the membrane protein, but only a marginal improvement of 1.09 was observed for the fibril. These differences are discussed, making note of the longer transfer time used for CP, 14 ms, as compared with 2.9 and 3.6 ms for SPEPS and TROP, respectively. Using SPEPS for two transfers in the 3D (H)CANCO experiment resulted in an even larger benefit in signal intensity, with an average improvement of 1.82 as compared with CP. This results in multifold time savings, in particular considering the weaker peaks that are observed to benefit the most from SPEPS

Simplified Preservation of Equivalent Pathways Spectroscopy

Inspired by the recently proposed transverse mixing optimal control pulses (TROP) approach for improving signal in multidimensional magic-angle spinning (MAS) NMR experiments, we present simplified preservation of equivalent pathways spectroscopy (SPEPS). It transfers both transverse components of magnetization that occur during indirect evolutions, theoretically enabling a √2 improvement in sensitivity for each such dimension. We compare SPEPS transfer with TROP and cross-polarization (CP) using membrane protein and fibril samples at MAS of 55 and 100 kHz. In three-dimensional (3D) (H)CANH spectra, SPEPS outperformed TROP and CP by factors of on average 1.16 and 1.69, respectively, for the membrane protein, but only a marginal improvement of 1.09 was observed for the fibril. These differences are discussed, making note of the longer transfer time used for CP, 14 ms, as compared with 2.9 and 3.6 ms for SPEPS and TROP, respectively. Using SPEPS for two transfers in the 3D (H)CANCO experiment resulted in an even larger benefit in signal intensity, with an average improvement of 1.82 as compared with CP. This results in multifold time savings, in particular considering the weaker peaks that are observed to benefit the most from SPEPS

Simplified Preservation of Equivalent Pathways Spectroscopy

Inspired by the recently proposed transverse mixing optimal control pulses (TROP) approach for improving signal in multidimensional magic-angle spinning (MAS) NMR experiments, we present simplified preservation of equivalent pathways spectroscopy (SPEPS). It transfers both transverse components of magnetization that occur during indirect evolutions, theoretically enabling a √2 improvement in sensitivity for each such dimension. We compare SPEPS transfer with TROP and cross-polarization (CP) using membrane protein and fibril samples at MAS of 55 and 100 kHz. In three-dimensional (3D) (H)CANH spectra, SPEPS outperformed TROP and CP by factors of on average 1.16 and 1.69, respectively, for the membrane protein, but only a marginal improvement of 1.09 was observed for the fibril. These differences are discussed, making note of the longer transfer time used for CP, 14 ms, as compared with 2.9 and 3.6 ms for SPEPS and TROP, respectively. Using SPEPS for two transfers in the 3D (H)CANCO experiment resulted in an even larger benefit in signal intensity, with an average improvement of 1.82 as compared with CP. This results in multifold time savings, in particular considering the weaker peaks that are observed to benefit the most from SPEPS

Static and Dynamic Wetting Behavior of Drops on Impregnated Structured Walls by Molecular Dynamics Simulation

Nanoscale drops on structured walls with which they interact through dispersive forces are investigated by molecular dynamics simulation. The drops are in the impregnation wetting regime, and the influence of the structures on the static and the dynamic wetting properties is studied. Drops of different size are simulated on six different walls which vary in the structure size and the wall morphology. Due to the nanoscale structure, there is a deviation of the interfacial tensions between the fluid and the wall from the value which would be observed on a macroscopic length scale. This phenomenon leads to contact angles which are greater than those predicted by the Cassie model. Accounting for the deviation of the interfacial tensions, the Cassie model is confirmed for drops on homogeneously structured walls, but it is shown to be inadequate for inhomogeneously structured walls. The dynamics of drop spreading is analyzed. It is observed that the presence of the wall structure poses hurdles to the spreading dynamics. The speed of spreading slows down with increasing structure size. The mechanism of drop spreading is observed to happen via the formation of local liquid protrusions of the drop and subsequent broadening of the protrusions. In the stable state, drop configurations are found which break the symmetry imposed by the wall geometry

Sensitivity-Enhanced Four-Dimensional Amide–Amide Correlation NMR Experiments for Sequential Assignment of Proline-Rich Disordered Proteins

Proline is prevalent in intrinsically disordered proteins (IDPs). NMR assignment of proline-rich IDPs is a challenge due to low dispersion of chemical shifts. We propose here new sensitivity-enhanced 4D NMR experiments that correlate two pairs of amide resonances that are either consecutive (NH_<i>i</i>–1, NH_<i>i</i>) or flanking a proline at position <i>i</i>–1 (NH_<i>i</i>–2, NH_<i>i</i>). The maximum 2-fold enhancement of sensitivity is achieved by employing two coherence order-selective (COS) transfers incorporated unconventionally into the pulse sequence. Each COS transfer confers an enhancement over amplitude-modulated transfer by a factor of √2 specifically when transverse relaxation is slow. The experiments connect amide resonances over a long fragment of sequence interspersed with proline. When this method was applied to the proline-rich region of B cell adaptor protein SLP-65 (pH 6.0) and α-synuclein (pH 7.4), which contain a total of 52 and 5 prolines, respectively, 99% and 92% of their nonprolyl amide resonances have been successfully assigned, demonstrating its robustness to address the assignment problem in large proline-rich IDPs

¹H-¹⁵N chemical shift changes of specific residues in comparison to the chemically denatured state.

<p>Selected regions of 2D [¹H,¹⁵N]-HSQCs with decreasing temperature: 298 K (red), 288 K (blue), 278 K (green), 268 K (maroon), and 260 K (purple). The unfolded state of ubiquitin was obtained by addition of 8 M urea at pH 2 (shown in thick grey).</p