Period 5 element with most production coming from the Xikuangshan Mine in Hunan. Antimony compounds are prominent additives for chlorine and bromine containing fire retardants found in many commercial and domestic products. The largest application for metallic antimony is as alloying material for lead and tin. It improves the properties of the alloys which are used as in solders, bullets and ball bearings. An emerging application is the use of antimony in microelectronics. Tellurium is a chemical element that has the symbol Te and atomic number 52. A brittle, mildly toxic, rare, silver-white metalloid which looks similar to tin, tellurium is chemically related
Chemical ligation with an N-terminal Ser or Thr residue. The chemoselective reaction between the peptide SAL ester and 1,2-hydroxylamine group of Ser or Thr leads to the formation of an N,O-benzylidene acetal linked intermediate, which undergoes acidolysis to afford a natural peptidic Xaa-Ser/Thr linkage. This method does not involve the use of unnatural amino acids, and it is simple to operate. Ser/Thr ligation provides a complementary method for protein chemical synthesis and semisynthesis. Schnölzer M, Kent SB. 1992, "Constructing proteins by dovetailing unprotected synthetic peptides: backbone-engineered HIV protease." "Science". 256:221-5 Dawson PE, Muir TW, Clark-Lewis I, Kent SB. 1994, "Synthesis of proteins