Replacement of phosphate

Replacement of Phosphates with Citric Mcid in Nylon Carpet Dyeing, Information Sheet No. 2025, Pfizer Chemicals Division, New York, 1973. 

The second method also relies on site-specific chemical modification ofphosphoproteins (Oda et al., 2001). It involves the chemical replacement of phosphates on serine and threonine residues with a biotin affinity tag (Fig. 2.7B). The replacement reaction takes advantage of the fact that the phosphate moiety on phosphoserine and phosphothreonine undergoes -elimination under alkaline conditions to form a group that reacts with nucleophiles such as ethanedithiol. The resulting free sulfydryls can then be coupled to biotin to create the affinity tag (Oda et al., 2001). The biotin tag is used to purify the proteins subsequent to proteolytic digestion. The biotinylated peptides are isolated by an additional affinity purification step and are then analyzed by mass spectrometry (Oda et al., 2001). This method was also tested with phosphorylated (Teasein and shown to efficiently enrich phosphopeptides. In addition, the method was used on a crude protein lysate from yeast and phosphorylated ovalbumin was detected. Thus, as with the method of Zhou et al. (2001), additional fractionation steps will be required to detect low abundance phosphoproteins. 

GSH reductase (Styblo et ah, 1997) and thioredoxin reductase (Lin eta/., 1999). The inhibition may be due to the interaction of trivalent arsenic with critical thiol groups in these molecules. A mechanism of toxicity of pentavalent inorganic arsenic, such as arsenate, is its reduction to a trivalent form, such as arsenite. The reduction of arsenate to arsenite occurs in vivo. Another potential mechanism is the replacement of phosphate with arsenate. 

Nitrilo triacetic acid (NTA) also represents a partial replacement of phosphate. However, the US Surgeon General issued a report stating that NTA caused birth defects in rats. The use of NTA was immediately phased out in the United States [4]. 

Another approach being used to enhance the ionization process is the chemical modification of the nucleic acid molecule in order to improve ionic volatility. For example, the replacement of phosphate protons from native DNA backbones by alkyl groups,25 or the replacement of phosphate groups by phosphorothioate groups followed by alkylation26 have been reported. 

Possibly the greatest potential use for poly(maleic anhydride) exists in the detergent, scale prevention, etc., water treatment areas. In fact, the increasing demand for pollution control and replacement of phosphates for detergents could open up a sizable market for poly(maleic anhydride) or MA copolymers and their hydrolyzed products.Methods are available to prepare decolorized polymers for detergent formulations. 

It required about three billion years for all the oceans of Earth to become saturated with phosphates for the first time. Until then oceans acted as a giant sink for phosphorus, holding it in solution too dilute to be of much use as a nutrient to life forms. When Earth s oceans became saturated, any new dissolved phosphates entering the seas caused precipitation of exactly the same amount of phosphate someplace else. This action became faster and faster until today there is a complete replacement of phosphate in oceans every 4.9 x 10 years, a very short time on a geological time scale. This estimate is based upon the estimate of McKelvey et al. that 2x10 tons of phosphorus are delivered to the seas each year, and Horn and Adams estimate of the phosphorus in the seas. " ... 

---