Development of surface plasmon resonance immunosensor for the novel protein immunostimulating factor

Fabrication of calix[4]arene derivative monolayers to control orientation of antibody immobilization

Three calix[4]arene (Cal-4) derivatives which separately contain ethylester (1), carboxylic acid (2), and crownether (3) at the lower rim with a common reactive thiol at the upper rim were synthesized and constructed to self-assembled monolayers (SAMs) on Au films. After spectroscopic characterization of the monolayers, surface coverage and orientation of antibody immobilized on the Cal-4 derivative SAMs were studied by surface plasmon resonance (SPR) technique. Experimental results revealed that the antibody could be immobilized on the Cal-4 derivatives spontaneously. The orientation of absorbed antibody on the Cal-4 derivative SAMs is related to the SAM’s dipole moment. The possible orientations of the antibody immobilized on the Cal-4 derivative 1 SAM are lying-on or side-on, while on the Cal-4 derivative 2 and Cal-4 derivative 3 head-on and end-on respectively. These experimental results demonstrate the surface dipole moment of Cal-4 derivative appears to be an important factor to antibody orientation. Cal-4 derivatives are useful in developing site direct protein chips.

Interaction of para-tert-butylcalix[6]arene molecules in Langmuir films with cadmium ions and their effects on molecular conformation and surface potential

The SFG data show the orientation of Calix6 molecules at the air/water interface, and their interaction with Cd ions.

SPR imaging biosensor for the 20S proteasome: sensor development and application to measurement of proteasomes in human blood plasma

The 20S proteasome is a multicatalytic enzyme complex responsible for intracellular protein degradation in mammalian cells. Its antigen level or enzymatic activity in blood plasma are potentially useful markers for various malignant and nonmalignant diseases. We have developed a method for highly selective determination of the 20S proteasome using a Surface Plasmon Resonance Imaging (SPRI) technique. It is based on the highly selective interaction between the proteasome's catalytic β5 subunit and immobilized inhibitors (the synthetic peptide PSI and epoxomicin). Inhibitor concentration and pH were optimized. Analytical responses, linear ranges, accuracy, precision and interferences were investigated. Biosensors based on either PSI and epoxomicin were found to be suitable for quantitative determination of the proteasome, with a precision of ±10% for each, and recoveries of 102% and 113%, respectively, and with little interference by albumin, trypsin, chymotrypsin, cathepsin B and papain. The proteasome also was determined in plasma of healthy subjects and of patients suffering from acute leukemia. Both biosensors gave comparable results (2860 ng·mL-1 on average for control, and 42300 ng·mL-1 on average for leukemia patients).FigureThe synthetic peptide aldehyde Z-Ile-Glu(OBut)-Ala-Leu-H (PSI) and a microbial α',β' epoxyketone peptide epoxomicin was used to develop SPRI biosensor for the highly selective determination of the 20S proteasome concentration, and to evaluate the sensor applicability for the determination of 20S proteasome in human blood plasma.