Secondary linkages

Silica or porous glass is usually used as the solid phase in oligonucleotide synthesis. The support is functionalized through an amino group attached to the silica surface. There is a secondary linkage through a succinate ester to the terminal 3 -OH group. 

Secondary Linkages The non-ionisable linkages of the metal are called secondary linkages. They can be satisfied by negative ions or neutral groups. The secondary linkages are directed in space about the central metal ion and they provide a structure to the species. 

Studies on Dextrans and Dextranases. Part X, Types and Percentages of Secondary Linkages in the Dextrans Elaborated by Leuconostoc mesenteroides NRRL B-1299, ... 

Presumably, the (1—>6)-linkages are split preferentially because of the greater ease of approach to that site than to a secondary-secondary linkage (compare the cleavage of methylene acetals, on p. 12). 

In the case of compounds such as (3.124a) showing secondary bonding, although the normal valency requirements of the component atoms are satisfied, the monomeric units readily assemble themselves into linear or cyclic polymers (3.124b). It is usually assumed that the metal atoms (M) retain some acceptor properties and the S atoms some donor character, which then enables a secondary linkage to be formed (shown in broken lines). Secondary bonding of this kind is usually associated with self-assembly properties and supramolecular chemistry [43]. 

D. Mazia On this point, I should like to say, amplifying a remark by Dr. Hellerman, that most workers have followed the proposal by Goddard and Michaelis that the secondary linkages in keratins were salt linkages and that the alkaline conditions were required to split these. Therefore, the mechanism just proposed by Dr. Benesch is a new one, and, from my standpoint, a very important one. 

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