Structural and Functional Characteristics of Chimeric Avidins Physically Adsorbed onto Functionalized Polythiophene Thin Films

Stabilized bioreceptor layers are of great importance in the design of novel biosensors. In earlier work, chimeric avidins enabled immobilization of biotinylated antibodies onto gold surfaces with greater stability compared to more conventional avidins (wild-type avidin and streptavidin). In the present study, the applicability of chimeric avidins as a general binding scaffold for biotinylated antibodies on spin-coated functionalized polythiophene thin films has been studied by surface plasmon resonance and atomic force microscopy. Novel chimeric avidins showed remarkably increased binding characteristics compared with other avidins, such as wild-type avidin, streptavidin, and bacterial avidin when merely physically adsorbed onto the polythiophene surface. They gave the highest binding capacities, the highest affinity constant, and the highest stability for biotinylated probe immobilization. Introduction of carboxylic acid groups to polythiophene layer further enhanced the binding level of the avidins. Polythiophene layers functionalized with chimeric avidins thus offered a promising generic platform for biosensor applications

Protein–Protein Interactions: Inhibition of Mammalian Carbonic Anhydrases I–XV by the Murine Inhibitor of Carbonic Anhydrase and Other Members of the Transferrin Family

The murine inhibitor of carbonic anhydrase (mICA), a member of the transferrin (TF) superfamily of proteins, together with human holo- and apoTF and lactoferrin (LF) were assessed as inhibitors of all catalytically active mammalian (h = human, m = murine) CA isoforms, from CA I to CA XV. mICA was a low nanomolar to subnanomolar inhibitor of hCAs I, II, III, VA, VB, VII and mCAs XV (<i>K</i>_I of 0.7–44.0 nM) and inhibited the remaining isoforms with <i>K</i>_I of 185.5–469 nM. hTF, apoTF, and hLF were inhibitors of most of these CAs but with reduced efficiency compared to mICA (<i>K</i>_I of 18.9–453.8 nM). Biacore surface plasmon resonance and differential scanning calorimetry experiments were also used for obtaining more insights into the interaction between these proteins, which may be useful for drug design of protein-based CA inhibitors

Switchavidin: Reversible Biotin–Avidin–Biotin Bridges with High Affinity and Specificity

Switchavidin is a chicken avidin mutant displaying reversible binding to biotin, an improved binding affinity toward conjugated biotin, and low nonspecific binding due to reduced surface charge. These properties make switchavidin an optimal tool in biosensor applications for the reversible immobilization of biotinylated proteins on biotinylated sensor surfaces. Furthermore, switchavidin opens novel possibilities for patterning, purification, and labeling