SummaryWe performed density functional calculations to examine the effects of solvation, hydrogen bonding, backbone conformation, and the side chain on 15 N chemical shielding in proteins. We used Nmethylacetamide (NMA) and N-formyl-alanyl-X (with X being one of the 19 naturally occurring amino acids excluding proline) as model systems. In addition, calculations were performed for selected fragments from protein GB3. The conducting polarizable continuum model was employed to include the effect of solvent in the density functional calculations. Our calculations for NMA show that the augmentation of the polarizable continuum model with the explicit water molecules in the first solvation shell has a significant influence on isotropic 15 N chemical shift but not as much on the chemical shift anisotropy. The difference in the isotropic chemical shift between the standard β-sheet and α-helical conformations ranges from 0.8 ppm to 6.2 ppm depending on the residue type, with the mean of 2.7 ppm. This is in good agreement with the experimental chemical shifts averaged over a database of 36 proteins containing >6100 amino acid residues. The orientation of the 15 N chemical shielding tensor as well as its anisotropy and asymmetry are also in the range of values experimentally observed for peptides and proteins.

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Summary We performed density functional calculations of backbone 15N chemical shielding tensors in selected helical residues of protein G. Here we describe a computationally efficient methodology to include most of the important effects in the calculation of chemical shieldings of backbone 15N. We analyzed the role of long-range intra-protein electrostatic interactions by comparing models with different complexity in vacuum and in charge field. Our results show that the dipole moment of the α-helix can cause significant deshielding of 15N; therefore, it needs to be considered when calculating 15N chemical shielding. We found that it is important to include interactions with the side chains that are close in space when the charged form for ionizable side chains is adopted in the calculation. We also illustrate how the ionization state of these side chains can affect the chemical shielding tensor elements. Chemical shielding calculations using a 8-residue fragment model in vacuum and adopting the charged form of ionizable side chains yield a generally good agreement with experimental data.

Ionic skin with a high performance has been extensively explored due to its ability to convert external stimuli into obvious electrical signals for wearable electronics and intelligent detection. However, due to the unmatched Young's moduli between the elastic substrate and the conductive layer, rapidly manufacturing durable ionic skin with ultrasensitivity over a wide range of pressures is still a great challenge. Here, we report a new strategy of 3D printing polymerizable deep eutectic solvent (PDES) for the manufacture of highly sensitive bioinspired ionic skin over a wide range of pressures via photopolymerization shrinkage formed submicrometer-scale protrusions on bioinspired skin structures. The 3D patterned poly(PDES) ionic skin (interlocked pyramid type with submicrometer protrusions) can realize "all-in-one" ability with high transparency, compressibility, and intrinsic conductivity, displaying ultrabroad range pressures (0.6 Pa−2 MPa) with superhigh sensitivity (348.28 KPa −1 ) and high electrical durability (at 0.35 MPa for 45 000 cycles). Furthermore, these excellent abilities allow as-prepared ionic skins to serve as visually detected pressure sensors for precision instruments, providing great potential in flexible wearable monitoring equipment and human-computer interaction.