Borohydride treatment

FIGURE 10.10 The reaction of tridated sodium borohydride with the aspartyl phosphate at the active site of Na, K -ATPase. Acid hydrolysis of the enzyme following phosphorylation and sodium borohydride treatment yields a tripeptide containing serine, homoserine (derived from the aspartyl-phosphate), and lysine as shown. The site of phosphorylation is Asp" in the large cytoplasmic domain of the ATPase. 

However, treatment of cis-l,3-pentadiene with Fe(CO)5 leads to formation of the hydride intermediate as shown for the conversion of 1,4-pentadiene to the [Pg.34]

Fixation in glutaraldehyde prodnces better morphology, but induces a great deal of autofluorescence, and limits cytoplasmic and nnclear permeability. A protocol utilizing glutaraldehyde followed by borohydride treatment has been previously described that is applicable also for electron microscopy of cultnred cells (4). Some areas of the cell are relatively impermeable with this approach, bnt this is an excellent choice of fixative protocol for microtnbnle morphology. 

Scheme 1.—Formation from Neu,5Ac Glycoside (3) of the C7 Aldehyde (4) and theC8 Aldehyde (5), as well as the C7 Analog (6) (5-Acetamido-3,5-dideoxy-L-firri/>mr>-heptulo-sonie Acid) and the Ca Analog (7) (5-Acetamido-3,5-dideoxy-n-g / cfr>-octnlosonic Acid) by Periodate-Borohydride Treatment of Glycosidically Bound Neu5Ac.

Reduction with sodium borohydride Treatment of monosaccharide with sodium borohydride (NaBH4) reduces it to a polyalcohol called an... 

Carlson (6) had shown earlier that porcine submaxillary glycoproteins (PSM) produced five reduced oligosaccharides after alkaline borohydride treatment (conditions 0.05M KOH, M NaBH4 at 45°C for 15 hours) removal of more than 90% of the side chains was reported. The oligosaccharides were separated and varied in size from mono to pentasaccharides. Katzman and Eylar (50) found similar but not identical oligosaccharides to be present in PSM, prepared by a different method. 

Sodium Borohydride Treatment. The pulp (1% consistency) together with EDTA (0.15% consistency) was suspended in water and stirred for one hour at room temperature, after which it was washed and filtered. The pulp was then suspended in water (1% consistency) and sodium borohydride was added (50% on pulp basis). The pulp suspension was stirred at room temperature for two days, followed by filtration, washing with water and air-drying at room temperature. 

Reaction Pathway and Products. In the presence of a catalytic amount of a tetraphenylporphyrin (TPP) Mn(III) complex (34) and sodium borohydride, treatment of cyclohexene with excess oxygen (air) in benzene-ethanol leads effectively to cyclohexanol and cy-clohexenol. The reaction is quite different from the known autoxidation catalyzed by TPP Mn(III) in the absence of NaBH4 (Figure 7). The most significant characteristics of the present TPPMn-NaBH4-02 reaction compared with the autoxidation are ... 

The high 77-deficiency at C-7 is also apparent from the nucleophilic addition reaction with sodium borohydride selective formation of the 6,7-dihydro derivative (566) results with this reagent. The reaction may also proceed further by reductive loss of the 7-substitutent (76CPB235). In the pyrazine analogue (567) both LAH and sodium borohydride treatment lead to saturation of the pyrazine ring (78JOC341). 

Stabilization of Paper Through Sodium Borohydride Treatment... 

The treatment of bleached kraft pulp with sodium borohydride followed by incorporation of basic calcium salts increased the stability of paper made from this pulp by 1.5-2.6 times. When manufactured paper, rather than pulp, was subjected to sodium borohydride treatment followed by washing with an aqueous solution of calcium hydroxide, the stability of the paper increased by as much as 4 times for groundwood paper and 30 times for bleached kraft paper. 

Some Foldur kraft samples were preaged before borohydride treatment and further aging. Paper samples were subjected to accelerated aging at 100 °C in a dry oven for 14 h or at 90 °C and 50% rh for 7 h. 

The effect of a reducing sodium borohydride treatment followed by a mildly alkaline wash on the physical properties and stability of paper was studied. Test papers were characterized by measuring their initial pH value, brightness, and folding endurance. Then they were subjected to borohydride treatment and washed with dilute calcium hydroxide solution or deionized water. The concentrations of sodium borohydride... 

Table IV shows brightness retention of newsprint papers. Borohy-dride treatment increased initial brightness by as much as 10 brightness units. A decrease in brightness is generally observed when newsprint is subjected to a Ca(OH)2 wash. Treatment with either 0.1 or 1.0 NaBH4 followed by 0.002 calcium hydroxide washing also increased the brightness of newsprint. For the newsprint samples, the borohydride treatment did not produce a significantly greater improvement in brightness retention than the calcium hydroxide wash alone.

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