Rechargeable batteries with high energy density, long cycle life, and low cost are considered key enablers for sustainable consumer electronics, electric vehicles (EVs), and smart grid energy storage. Lithium-ion batteries (LIBs) have been emerged

Zintl phases form hydrides either by incorporating hydride anions (interstitial hydrides) or by covalent bonding of H to the polyanion (polyanionic hydrides), which yields a variety of different compositions and bonding situations. Hydrides (deuterides) of SrGe, BaSi, and BaSn were prepared by hydrogenation (deuteration) of the CrB-type Zintl phases AeTt and characterized by laboratory X-ray, synchrotron, and neutron diffraction, NMR spectroscopy, and quantum-chemical calculations. SrGeD and BaSnD show condensed boatlike six-membered rings of Tt atoms, formed by joining three of the zigzag chains contained in the Zintl phase. These new polyanionic motifs are terminated by covalently bound H atoms with d(Ge-D) = 1.521(9) Å and d(Sn-D) = 1.858(8) Å. Additional hydride anions are located in Ae tetrahedra; thus, the features of both interstitial hydrides and polyanionic hydrides are represented. BaSiD retains the zigzag Si chain as in the parent Zintl phase, but in the hydride (deuteride), it is terminated by H (D) atoms, thus forming a linear (SiD) chain with d(Si-D) = 1.641(5) Å.

The far-ultraviolet band structure of tryptophan residues has been investigated in order to characterize their contributions to the spectral properties of proteins. Absorption spectra of 3-methylindole and indole-3acetic acid derivatives and the absorption and circular dichroism (CD) spectra of L-tryptophan and some derivatives were determined in various solvents at room temperature. Four types of CD spectra were found. All have intense positive ellipticity centered at about 223 nm, but have differing patterns of zero or negative ellipticity, in one or more bands, below about 215 nm. Simultaneous resolution of absorption and CD spectra into Gaussian components yields a consistent set of four bands in the !Bb region which is sufficient to describe every spectrum save one, while only one broad band is needed in the TSa region. Solvent effects and vicinal charge effects have been characterized. From our results, we are able to discount the possibility that parts of the observed CD spectra arise from coupling with the -* and tt-tt* transitions of carboxyl, amide, or ester moieties.

SynopsisThe osmotic, sedimentation, arid diffusion coefficients of sonicated sodium DNA in aqueous solutions which were rendered rigorously free of salts have been obtained iii order to study the polyelectrolyte effect on these parameters. Both native and heatdenatured DNA's were studied. All three parameters were forind to be independent of concentration between 2 and 10 mmole/l. The osmotic coefficient gives the fraction of counterions not immobilized by the polyelectrolyte potential, under conditions of equilibrium. The value (ca. 0.18) obtained for this fraction agrees very well with that, predicted by a theory of rodlike polyelectrolytes. A simplified model that permits the computation of fractions of mobile ions from sedimentation and diff iision coefficients, when applied to the experimental data, showed t,hat tinder these conditions of flow between 0.5 to 0.9 of counterions are not, immobilized. The experimental dat,a also showed that for native DNA the translation frictional coefficient seems to have different values in sedimentation and diffusion, which agrees with a finding reported for another saltfree polyelectrolyte. For denatured DNA, however, the valiies were found to be equal; no satisfactory explanation coiild be found for this difference of behavior.