Structural and optical properties of amorphous Si-Ge-Te thin films prepared by combinatorial sputtering.

The lack of order in amorphous chalcogenides offers them novel properties but also adds increased challenges in the discovery and design of advanced functional materials. The amorphous compositions in the Si-Ge-Te system are of interest for many applications such as optical data storage, optical sensors and Ovonic threshold switches. But an extended exploration of this system is still missing. In this study, magnetron co-sputtering is used for the combinatorial synthesis of thin film libraries, outside the glass formation domain. Compositional, structural and optical properties are investigated and discussed in the framework of topological constraint theory. The materials in the library are classified as stressed-rigid amorphous networks. The bandgap is heavily influenced by the Te content while the near-IR refractive index dependence on Ge concentration shows a minimum, which could be exploited in applications. A transition from a disordered to a more ordered amorphous network at 60 at% Te, is observed. The thermal stability study shows that the formed crystalline phases are dictated by the concentration of Ge and Te. New amorphous compositions in the Si-Ge-Te system were found and their properties explored, thus enabling an informed and rapid material selection and design for applications.

Peptide mapping and disulfide bond analysis of myeloid progenitor inhibitory chemokine and keratinocyte growth factor by matrix-assisted laser desorption ionization mass spectrometry.

Peptide mapping and matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) were conducted to characterize the human genome-based recombinant proteins. Accurate mass values for the deleted forms of the myeloid progenitor inhibitory factor chemokine (MPIF-1d23), and the keratinocyte growth factor (KGF-2d33) were measured as 8848.55 +/- 0.25 and 16,175.87 +/- 0.89 Da, respectively. The mass accuracy of delayed ion extraction MALDI-MS measurements was within 20 ppm of the cDNA predicted value. Reduction and alkylation of the chemokine showed the presence of six cysteine residues and three disulfide bonds. Additional confirmation of disulfide bonding among the cysteine residues of the chemokine was demonstrated by identifying the RP-HPLC separated tryptic and endoprotease Glu-C peptides. Three methionine residues of the chemokine were identified by MALDI-MS of its cyanogen bromide (CNBr) cleavage products. The KGF-2d33 growth factor, however, lacked the disulfide bonding between the two-cysteine residues and contained two free sulfhydryl groups. Direct analysis of the growth factor CNBr digest showed 7542.99, 4993.4, and 3107.7 Da peptides, which identified the methionine residues. Peptide mapping mass spectrometry indicated that host-specific posttranslational modifications had not influenced the gene expression work.