Molecular architecture and electrical properties in evaporated films of cobalt phthalocyanine.

Thin films of cobalt phthalocyanine (CoPc) were deposited onto solid substrates through physical vapor deposition (PVD) by thermal evaporation up to 60 nm thick to determine their molecular architecture and electrical properties. The growth was monitored using UV-Vis absorption spectroscopy, revealing a linear increase for absorbance versus thickness. PVD films were found in the crystalline alpha phase and with the CoPc molecules forming ca. 45 degrees in relation to the substrate surface. The film surface was fairly homogeneous at the micro and nanoscales, with the roughness at ca. 3 nm. DC and AC electrical measurements were carried out for devices built with distinct structures. Perpendicular contact was established by depositing 60 nm CoPc PVD films between indium tin oxide (ITO) and Al, forming a sandwich-type structure (ITO/CoPc/Al). The current versus DC voltage curve indicated a Schottky diode behavior with a rectification factor of 4.2. The AC conductivity at low frequencies increased about 2 orders of magnitude (10(-9) to 10(-7) S/m) with increasing DC bias (0 to 5 V) and the dielectric constant at 1 kHz was 3.45. The parallel contact was obtained by depositing 120 nm CoPc PVD film onto interdigitated electrodes, forming an IDE-structured device. The latter presented a DC conductivity of 5.5 x 10(-10) S/m while the AC conductivity varied from 10(-9) to 10(-1) S/m between 1 Hz and 1 MHz, respectively, presenting no dependence on DC bias. As proof-of-principle, the IDE-structured device was applied as gas sensor for trifluoroacetic acid (TFA).

Fibronectin modulates interleukin 6 and fibronectin synthesis of human glomerular mesangial cells in culture.

In this paper we report that fibronectin (FN) and its proteolytic 120-kD fragment regulate synthesis and secretion of interleukin 6 (IL-6) and of FN by human glomerular mesangial cells. While intact FN and a fragment derived from the heparin-binding domain had no effect on IL-6 secretion, the 120-kD FN fragment containing the cell attachment site stimulated secretion by 40-fold. The same FN fragment reduced FN secretion and the steady state mRNA level by 80%. The intact FN showed only a weak inhibitory effect (+/- 30%); the 30-kD fragment containing the heparin-binding domain had no effect. The effects of the 120-kD FN were inhibited by the peptide RGDS, implying participation of the cell attachment site in signal transduction. An antibody to the alpha-chain of VLA-3 mimicked the effect of the 120-kD FN, whereas an antibody to the alpha-chain of VLA-5 was partly inhibitory. Taken together, the data suggest that FN by interacting with its receptors differentially regulates the protein synthesis of glomerular mesangial cells, promoting IL-6 secretion and inhibiting FN synthesis.

Expression of the complement regulator factor C8 binding protein on human glomerular cells protects them from complement-mediated killing.

The complement-regulatory factor C8 binding protein (C8bp) was first identified on human erythrocyte membranes by its affinity for the complement component C8 and its ability to inhibit lysis by homologous complement. Cultured human glomerular mesangial or epithelial cells (GEC) expressed C8bp on the cell surface and in the cytoplasm. Following stimulation of the glomerular cells with interleukin 1 beta, C5b-9 or with endotoxin, a transient, protein synthesis-independent increase in C8bp surface expression was seen. Blocking of C8bp function with F(ab)2 fragment of an antibody to C8bp rendered GEC susceptible to complement-mediated killing, indicating that C8bp contributes to the cellular defense against complement attack.

Induction of matrix protein synthesis in human glomerular mesangial cells by the terminal complement complex.

Exposure of human glomerular mesangial cells (GMC) in culture to sublytic doses of the terminal complement proteins C5b-8 and C5b-9 caused a transient increase in abundance of mRNA specific for collagen type IV and fibronectin; mRNA of laminin was not affected. Since C5b-9 is found deposited in inflamed or sclerotic areas we propose that stimulation of matrix protein synthesis by C5b-9 might contribute to the development of glomerular sclerosis.