The success of hybrid organic-inorganic perovskites (HOIP) in photovoltaic applications is based on their high power conversion efficiencies, up to 23.3%, in combination with seemingly
Aspergillus niger glucoamylases GI and GII (E.C. 3.2.1.3) were isolated from a commercial enzyme preparation by ammonium sulfate precipitation followed by DEAE-cellulose ion exchange chromatography. Both enzymes consist of a single glycosylated polypeptide chain. The molecular weights of GI and GII were determined by sedimentation equilibrium ultracentrifugation to 52,000 and 46,000, respectively, and by molecular sieving to 65,000 and 55,000. The amino acid compositions of GI and GII were very similar. Furthermore, the N-terminal amino acid sequence of the intact GI and GII as well as of their cyanogen fragments were identical, suggesting great homology in the primary structure of the two forms. In addition the digests of GI and GII produced respectively by Armillaria mellea protease, Staphylococcus aureus V8 protease, and submaxilla~ protease were analyzed by high pressure gel permeation chromatography. The elution profiles were also consistent with GI and GII having similar polypeptide chains. However, digestion with carboxypeptidase Y showed different C-terminal residues of the two forms. 1. INTRODUCTION Glucoamylase (l,4-aD -glucan glucohydrolase, E.C. 3.2.1.3) catalyzes the release of Dglucose from the non-reducing end of starch, glycogen and gluco-oligosaccharides. Although the ct-i,6-glucosidic linkages are cleaved less readily than the a-l,4-glucosidic linkages (17, 28, 38), the debranching capacity of glucoamylases is sufficient to make them important in the industrial production of glucose from starch, a Abbreviations: GI and GII denote two forms of glucoamylase.
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Carboxypeptidase Y from bakers' yeast has been purified in high yields by affinity chromatography. The affinity gel was prepared by coupling the specific inhibitor p-aminobenzylsuccinic acid via an azo linkage to Sepharoseglycyl-tyrosine. This affinity gel was able to bind carboxypeptidase Y specifically and quantitatively from a crude yeast autolysate. The isolated enzyme appeared homogeneous by gel electrophoresis and ultracentrifugation, while isoelectric focusing revealed the presence of two components with isoelectric points of pH 3.56 and 3.66, respectively. Small differences in amino acid composition and enzymatic properties between the enzyme from danish yeast and the corresponding enzyme isolated from Fleichmann yeast suggested the existence of more than one form of this enzyme.
The discovery of lead-based organicinorganic perovskite materials for optoelectronic applications has triggered a revolution in photovoltaic material research. Despite their exceptional material properties such as strong light absorption, long charge carrier lifetimes in combination with high carrier mobility, and low production costs, their long-term instability, and the toxicity of lead currently hamper their deployment at an industrial scale. [1] To overcome this drawback, double perovskites with the general formula A 2 1+ M 1+ M′ 3+ X 6 have been proposed as candidate materials providing leadfree alternatives in the vastly expanding research field of perovskites. One of the first materials investigated in this branch of the perovskite catalog is Cs 2 AgBiBr 6 , demonstrating high stability in devices [2,3] and low effective carrier masses [4] with the long carrier recombination lifetimes Lead-free double perovskites have great potential as stable and nontoxic optoelectronic materials. Recently, Cs 2 AgBiBr 6 has emerged as a promising material, with suboptimal photon-to-charge carrier conversion efficiency, yet well suited for high-energy photon-detection applications. Here, the optoelectronic and structural properties of pure Cs 2 AgBiBr 6 and alkalimetal-substituted (Cs 1−x Y x) 2 AgBiBr 6 (Y: Rb + , K + , Na + ; x = 0.02) single crystals are investigated. Strikingly, alkali-substitution entails a tunability to the material system in its response to X-rays and structural properties that is most strongly revealed in Rb-substituted compounds whose X-ray sensitivity outperforms other double-perovskite-based devices reported. While the fundamental nature and magnitude of the bandgap remains unchanged, the alkali-substituted materials exhibit a threefold boost in their fundamental carrier recombination lifetime at room temperature. Moreover, an enhanced electron-acoustic phonon scattering is found compared to Cs 2 AgBiBr 6. The study thus paves the way for employing cation substitution to tune the properties of double perovskites toward a new material platform for optoelectronics.
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