Proteins osmium tetroxide

Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

The fluorescent labels reported for investigation of intracellular uptake and distribution by CLSM comprise Nile red [13], Texas Red, and 6-coumarin [14]. Not only for fluorescence microscopy but also for transmission electron microscopy (TEM), the loading of markers proved to be useful. Osmium tetroxid as an electron dense marker and bovine serum albumin (BSA) as a model protein were entrapped in PLGA-nanoparticles to elucidate their uptake and intracellular distribution in human vascular smooth muscle cells [15]. 

FIGURE 5.5 High magnification TEM of the fiber cuticle surface as it appears in transverse section after bulk fiber staining with osmium tetroxide. The fiber cuticle surface membrane (FCSM) comprising lipids (fatty acids) and proteins is approximately 6 nm thick and is apposed to the a-layer (a) of exocuticle (exo). Bar equals 0.1 p,m. 

Fig. 6.29A-C. Changes in the protein reserves and cell wall material within cotyledon mesophyll tissue of Lupinus angustifolius L. cv. New Zealand Bitter Blue. (A) Cotyledon material from dry seed imbibed in fixative (2 h, glutaraldehyde 4h, osmium tetroxide). (B) 5-day cotyledons. (C) 9-day cotyledons. Kindly provided by Dr. M. Parker...

Phospholipids occur in cells mostly as components of cellular membranes in which they are in close structural relation to proteins. This interaction is an important factor in relation to the problem of phospholipid preservation during dehydration and embedding of tissues. Data on total phospholipid retention, following labeling with fatty acids are given by Kom and Weisman (1966) in the amoeba and by Dermer (1968) in rat intestine. The former have noted better retention of phospholipids than of neutral lipids, while the latter reported that both were retained to the same extent Very little loss of phospholipids, determined chemically, from erythrocyte stroma fixed with glutaraldehyde and osmium tetroxide in the presence of Ca ions was reported by Mitchell (1969). The loss increased from 2 to 7% if the stroma was stored for 7-10 days prior to fixation. 

Studies by Lenard and Singer (1968) on erythrocyte membranes treated with glutaraldehyde, osmium tetroxide, and potassium permanganate have shown a considerable decrease in a-helix content of the membrane protein which implies the occurrence of other structural changes as a result of these treatments. 

Together with Finean s data on dehydration, these observations strongly suggest that artifactual effects should result from application of Sjostrand s procedure (Sjostrand, 1963) for the demonstration of globular protein units in cytoplasmic membranes. Cumulative effects from glutaraldehyde, osmium tetroxide, permanganate, and dehydration, which are all involved in the initial phase of this procedure, could be described by Fig. 8b and c subsequent steps could be described by Fig. 8d, e, and f. 

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