Lp Andersson

Diamond-like carbon films produced in a butane plasma☆

Abstract Diamond-like carbon films produced in an r.f. butane plasma were characterized by X-ray photoemission analysis of the deposits. It was confirmed that films produced at low deposition rates were more diamond-like than films produced at high deposition rates. An investigation of the electrical properties of the films showed that the low deposition rate films were highly insulating whereas the high deposition rate films were conducting.

Electrical Defects in Silicon Introduced by Sputtering and Sputter‐Etching

Sputtering a gold contact on n‐silicon or sputter‐etching the silicon surface prior to deposition of gold results in a Schottky barrier which shows a barrier height which depends on the sputtering voltage and time, and is lower than a corresponding barrier obtained by evaporation of a gold contact. On p‐silicon a sputtered gold contact also shows a barrier height influenced by the sputtering conditions. The modifications of the barrier height are caused by a thin positively charged layer formed in the semiconductor near the metal‐semiconductor junction. During sputter etching the silicon surface is subject to bombardment by Ar ions with energies of about the sputtering voltage. If this voltage is high enough charged centers will be introduced. These centers are also observed after sputter deposition at high voltage. We found that damage is caused by etching at 500V but not at 100V. This indicates that the damage found after sputter deposition was caused by rebounded Ar atoms.

Properties and coating rates of diamond-like carbon films produced by R.F. glow discharge of hydrocarbon gases

Abstract We studied the properties of films produced by cracking various hydrocarbon gases in an r.f. glow discharge. Mass spectrometry studies and optical spectroscopy of the glow discharge were performed during the experiments. We found that the production rates for the films increased with the molecular weight for gases having the same structural form, e.g.C4H10 had a higher coating rate than CH4 under the same plasma conditions. Also the sputter-etch rate of the films depended on both the substrate material and the hydrocarbon gas used. Films several microns thick were manufactured onto steel substrates and showed a microhardness of more than 3000 kgf mm-2.

Improved preparation of the integral membrane proteins of human red cells, with special reference to the glucose transporter

Human red cell membranes were isolated and partially stripped of peripheral proteins by gel filtration of hemolysates on a Sepharose CL-4B column at pH 8 connected in tandem to a Sepharose CL-6B column at pH 10.5. The eluted material was washed by centrifugations, once at pH 10.5 and twice at pH 12. In this way, water-soluble proteins and peripheral membrane proteins were thoroughly removed, and 0.2 g of integral membrane proteins could be prepared within 10 h from 0.2 litre of red cells. The exposure to high pH did not lower the D-glucose transport activity, and electrophoretically pure glucose transport protein could be isolated from this preparation. Gel filtration in sodium dodecyl sulfate separated the integral membrane components into four fractions, one of them containing 4.5-material; gel electrophoresis showed about 14 zones and two-dimensional electrophoresis resolved up to 100 mostly minor components, among which the glucose transporter focused around pH 7. However, purified glucose transporter focused around pH 8. Glucose and nucleoside transport proteins were co-purified in active form on DEAE-cellulose and a fraction isolated by adsorption to Mono Q was used for immunization of mice and production of monoclonal antibodies. One hybridoma produced antibodies that reacted with material in the 4.5-region, possibly the glucose transport protein, and not with band 3-material. Upon two-dimensional electrophoresis of integral membrane components that had been solubilized with octyl glucoside the immunoreactive and the silver-stained 4.5-material focused in a broad range from pH 6 to pH 9. A possible explanation for this heterogeneity might be interaction between the glucose and nucleoside transport proteins and negatively charged lipids.

Vascular expression of endothelial antigen PAL-E indicates absence of blood-ocular barriers in the normal eye

The endothelium-specific antigen PAL-E is expressed in capillaries and veins throughout the body with the exception of the brain, where the antigen is absent from anatomical sites with a patent blood-brain barrier. In this study we determined vascular endothelial staining for PAL-E in the normal eye in relation to the ocular blood-tissue barriers. Immunohistochemical staining of frozen tissue sections of eyes from 22 cornea donors and a number of normal animal autopsy eyes was performed for the PAL-E antigen and the blood-brain barrier marker glucose transporter 1. In normal human and animal eyes, endothelial PAL-E staining was absent from the microvasculature in iris, ciliary muscle, optic nerve and retina. In a few normal human eyes, some weakly stained capillaries were observed in the retina and nerve fiber layer, mostly in the peripapillary area. Marked staining of capillaries and venules with PAL-E was observed in the conjunctiva, episclera, sclera, ciliary processes, choriocapillaris and optic nerve head. In general, the endothelial antigen PAL-E is absent from microvessels involved in the blood-ocular and the blood-retinal barriers. PAL-E may therefore be a useful marker to identify pathological breakdown of blood-ocular barriers.

Monomeric human red cell glucose transporter (Glut1) in non-ionic detergent solution and a semi-elliptical torus model for detergent binding to membrane proteins

The self-association state of the human red cell glucose transporter (Glut1) in octaethylene glycol n-dodecyl ether (C12E8) and n-octyl beta-D-glucopyranoside (OG) solution was analyzed in the presence of reductant by gel filtration with light-scattering, refractivity and absorbance detection, and by ultracentrifugation. The C12E8-Glut1 complex was essentially monomeric, whereas OG-Glut1 also formed dimers and larger oligomers. C12E8-Glut1 retained substantial glucose transport activity even after depletion of endogenous lipids by gel filtration, as shown by reconstitution and transport measurements. Removal of endogenous lipids from OG-Glut1 abolished the activity unless phosphatidylcholine was included in the eluent. The binding of C12E8 and OG to Glut1 was determined by gel filtration with refractivity and absorbance detection or with radioactive tracer to be 1.86 +/- 0.07 and 1.84 +/- 0.09 g/g polypeptide, respectively. A structural model was proposed in which non-ionic detergent forms a semi-elliptical torus (SET) surrounding the transmembrane protein. The torus thickness was assumed to be equal to the radius (short half-axis) of a spherical (oblate ellipsoidal) free detergent micelle and the polar head groups of the detergent molecules were predicted to be situated just outside the hydrophobic surface of the protein. The experimental detergent binding values and those obtained from the SET model together confirmed that Glut1 was monomeric in C12E8 solution and provided constraints on the shape and size of the hydrophobic transmembrane region of Glut1 in alpha-helical and beta-barrel topology models.

Active and monomeric human red cell glucose transporter after high performance molecular-sieve chromatography in the presence of octyl glucoside and phosphatidylserine or phosphatidylcholine

The human red cell glucose transporter (Glut 1) was purified by ion-exchange chromatography in the presence of octyl glucoside. The state of association of the protein was studied, and the transport activity was determined after exchange of copurified membrane lipids for phosphatidylserine (PS) or phosphatidylcholine (PC). The purpose was to analyze the Glut 1 preparation for homogeneity and activity prior to attempts at crystallization. Analyses by high performance molecular-sieve chromatography showed that the Glut 1 was monomeric immediately after the ion-exchange purification: the Mr of the Glut 1 polypeptide was estimated to be 49,000 +/- 6000 by TSKgel G3000SW chromatography monitored by low-angle laser light-scattering photometry, differential refractometry and UV photometry. This required determination of the absorption coefficient of the Glut 1, which was measured to be 1.13 +/- 0.03 ml mg-1 cm-1 at 280 nm, referring to the polypeptide concentration. The Mr value is consistent with the cDNA-deduced Mr 54,117 of the very similar HepG2 glucose transporter polypeptide. At 2 degrees C, pH 7 and an ionic strength of 0.06 M, the Glut 1 associated gradually during three days to form oligomers. These formed much more rapidly at room temperature or at high ionic strength. Freshly prepared Glut 1 retained high activity after separation from membrane lipids on a TSKgel G3000SW column in the presence of 40 mM octyl glucoside and 1 mM PS or PC. In contrast, most of the activity was lost when the membrane lipids were separated from the protein in the absence of eluent lipids. The presence of a phospholipid was thus essential for retention of high activity of the Glut 1 in octyl glucoside and PC was nearly as effective as PS.

Non-ortho- and mono-ortho-chlorine-substituted polychlorinated biphenyls — Embryotoxicity and inhibition of lymphoid development

Abstract The toxicities and 7-ethoxyresorufin O -deethylase-inducing potencies of non- ortho - and mono- ortho -chlorinated PCBs were studied in chick embryos. The non- ortho -chlorinated congeners were considerably more embryotoxic and more potent as inhibitors of lymphoid development in the embryonic bursa of Fabricius than the mono- ortho -chlorinated congeners. The EROD-inducing potencies of the PCBs correlated well with their toxicities. The mono- ortho -chlorinated congeners having a chlorine in the meta position adjacent to the ortho -chlorine were more toxic and stronger EROD-inducers than the congeners having a hydrogen in this position. Co-administration of 3,3′,4,4′,5-pentachlorobiphenyl and 2,3,3′,4,4′,5-hexachlorobiphenyl resulted in additive effects with respect to embryotoxicity and EROD activity.

2.2 Substrate surface damages by rf-sputtering

Abstract Electrical properties of (111) surfaces of n -type silicon exposed to sputtered metal atoms deposited in a rf-diode sputter system were studied. The metal-silicon junction formed by this process was investigated to evaluate surface properties of the junction. It was shown that the sputtering process introduced damage to the surface, causing charged centres to appear at the surface of the crystal. A theory is presented which explains most of the experimental results of the so damaged Schottky junction. Thermal activation energies are deduced from experimental data and compared to expected values predicted by the theory presented. The energies are found to vary between 0·3 and 0·7 eV depending on sputtering conditions.

18. Initial etching in an rf butane plasma

During deposition of carbon from a glow-discharge of C4H10 we have observed that the hydrocarbon fragments impinging on the substrate initially do not deposit, but rather etch the surface of the substrate. Gradually the etching process changes over to deposition after a few minutes. The addition of as much as 15% air into the butane plasma had no influence on the rate of etched gold. However, the choice of substrate material strongly affects the amount of etching taking place. A simple model is outlined in order to describe the observed effect in terms of incoming flux of hydrocarbon fragments and sputter yields of the substrate and the formed disordered carbon film.