Protein immobilization and surface chemistry

The performance of protein or antibody microarrays is dependent on various factors. One of these is the use of an appropriate microarray surface for the immobilization of the protein or antibody samples. Most conventional microarray surfaces have been adapted from DNA chip technology. DNA can easily be immobilized by electrostatic interactions of the phosphate backbone onto a positively charged surface. In contrast to DNA, as already mentioned, proteins are chemically and structurally much more complex and show variable charges, which may influence the efficiency of protein attachment. Additionally, proteins lose their structure and biochemical activity easily. For example, globular proteins consist of a hydrophilic exterior and a hydrophobic interior. When immobilized on a hydrophobic surface, the inside of the protein turns out, which may destabilize the structure and, simultaneously, the activity of the protein. These considerations demonstrate the complex requirements for protein immobilization. 

Attachment Sutfaces Binding mechanism Advantages/disadvantages 

Covalent, random Epoxy, aldehyde, carbodiimide groups React with primary amines of lysine and arginine High densihes are available and strong protein attachment/ random orientahon and surface interference 

Covalent, orientated Amino groups, hydrazine Binds to carbohydrate residues of EC region of antibodies High densihes are available, strong protein attachment, oriented immobilization/ surface interference 

---