93 research outputs found
Creation and control of a two-dimensional electron liquid at the bare SrTiO3 surface
Many-body interactions in transition-metal oxides give rise to a wide range
of functional properties, such as high-temperature superconductivity, colossal
magnetoresistance, or multiferroicity. The seminal recent discovery of a
two-dimensional electron gas (2DEG) at the interface of the insulating oxides
LaAlO3 and SrTiO3 represents an important milestone towards exploiting such
properties in all-oxide devices. This conducting interface shows a number of
appealing properties, including a high electron mobility, superconductivity,
and large magnetoresistance and can be patterned on the few-nanometer length
scale. However, the microscopic origin of the interface 2DEG is poorly
understood. Here, we show that a similar 2DEG, with an electron density as
large as 8x10^13 cm^-2, can be formed at the bare SrTiO3 surface. Furthermore,
we find that the 2DEG density can be controlled through exposure of the surface
to intense ultraviolet (UV) light. Subsequent angle-resolved photoemission
spectroscopy (ARPES) measurements reveal an unusual coexistence of a light
quasiparticle mass and signatures of strong many-body interactions.Comment: 14 pages, 4 figures, supplementary information (see other files
Ultrafast charge transfer processes accompanying KLL Auger decay in aqueous KCl solution
X-ray photoelectron spectroscopy (XPS) and KLL Auger spectra of aqueous KCl
solution were measured for the K and Cl edges. While the XPS spectra of
potassium and chloride have similar structures, both exhibiting only weak
satellite structures near the main line, the Auger spectra of these
isoelectronic ions differ dramatically. A very strong satellite peak was found
in the K KLL Auger spectrum at the low kinetic energy side of the D
state. Using equivalent core models and ab initio calculations this spectral
structure was assigned to electron transfer processes from solvent water
molecules to the solvated K cation. Contrary to the potassium case, no
extra peak was found in the KLL Auger spectrum of solvated Cl indicating on
a strong dependence of the underlying processes on ionic charge. The observed
charge transfer processes are suggested to play an important role in charge
redistribution following single and multiple core-hole creation in atomic and
molecular systems placed into an environment
Bacterial β-Glucosidase Reveals the Structural and Functional Basis of Genetic Defects in Human Glucocerebrosidase 2 (GBA2)
Human glucosylcerebrosidase 2 (GBA2) of the CAZy family GH116 is responsible for the breakdown of glycosphingolipids on the cytoplasmic face of the endoplasmic reticulum and Golgi apparatus. Genetic defects in GBA2 result in spastic paraplegia and cerebellar ataxia, while cross-talk between GBA2 and GBA1 glucosylceramidases may affect Gaucher disease. Here, we report the first three-dimensional structure for any GH116 enzyme, Thermoanaerobacterium xylanolyticum TxGH116 β-glucosidase, alone and in complex with diverse ligands. These structures allow identification of the glucoside binding and active site residues, which are shown to be conserved with GBA2. Mutagenic analysis of TxGH116 and structural modeling of GBA2 provide a detailed structural and functional rationale for pathogenic missense mutations of GBA2
Chitin Research Revisited
Two centuries after the discovery of chitin, it is widely accepted that this biopolymer is an important biomaterial in many aspects. Numerous studies on chitin have focused on its biomedical applications. In this review, various aspects of chitin research including sources, structure, biosynthesis, chitinolytic enzyme, chitin binding protein, genetic engineering approach to produce chitin, chitin and evolution, and a wide range of applications in bio- and nanotechnology will be dealt with
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