A surface plasmon resonance (SPR) biosensor technology has recently been applied biochemically and clinically to the study of immunologic recognition and the evaluation of binding parameters for various interactions between antibodies (Abs) and antigens (Ags) at liquid-solid interface. The simple interaction between hapten and Ab fragment, e.g., variable single-chain fragment and antigenbinding fragment, can be described sufficiently by a 1:1 stoichiometry in SPR. However, the determination of the binding constant of an anti-protein Ab is usually complicated by the multivalence of the protein Ag. The SPR-based method enables direct determination of binding constants for a variety of specific Ab-Ag interactions in real-time. It also allows estimation of the binding stoichiometry and binding ratio for low-, intermediate-, and high-affinity Ab-Ag interaction systems. The present review is designed to indicate the theoretical background of SPR-based biosensor technology as well as to present the great variety of measurement modes of interaction kinetics that can be performed with these techniques. Quantitative aspects of the Ab-Ag interaction kinetics are reviewed, focusing especially on mono-and multi-valent Ab-Ag interaction modes using a SPR biosensor. Four model binding systems developed recently for use with SPR biosenser are described with principles and examples: (i) one to one interaction mode, (ii) nonequivalent two-site interaction mode, (iii) multiple equivalent-site interaction mode and (iv) multisite interaction mode. This article closes with two descriptions of the determinations of the binding stoichiometry and maximum binding ratio of Ab-Ag interactions.

We developed a liquid crystal (LC) sensor system for detecting mercuric ion (Hg(2+)) in aqueous solutions. In this system, 4-cyano-4'-pentyl biphenyl (5CB) was doped with a sulfur- and nitrogen-containing ligand 5-(pyridine-4-yl)-2-(5-(pyridin-4-yl)thiophen-2-yl)thiazole (ZT) as the Hg(2+) specific LCs. When the system was immersed in the solution containing Hg(2+), the complex of ZT and Hg(2+) formed, which disrupted the orientation of LC and lead to a dark-to-bright transition of the image of LCs. From mercuric binding titrations monitored by UV-vis spectroscopy, it was found that 1:1 Hg(2+)/ZT complexes were formed. The limit of detection (LOD) of the system to Hg(2+) is 10 μM, and it did not respond to Cd(2+), Zn(2+), Cu(2+), Pb(2+), Fe(+), Mg(2+), Ca(2+), Na(+), and K(+). Besides, we also demonstrated that this system is capable of detecting Hg(2+) in tap water and pond water. Because the signal of this system is colorful under ambient light, which is readily understood by normal users, it can be used as a portable device to monitor the water quality at any location.

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A series of beta-(trimethylsilyl)ethoxymethyl ethers were hydrolyzed to their corresponding alcohols in high yields by using a catalytic amount of CBr4 (15%) in MeOH under refluxing reaction conditions. The chemoselective deprotection between trialkylsilyl and beta-(trimethylsilyl)ethoxymethyl-protected alcohols can be achieved by using an alcohol with steric hindrance such as iPrOH. The selectivity also can be achieved in the CBr4/MeOH reaction mixture under ultrasonic reaction conditions.