Standardized measurements and differential spectroscopy in microplates

Microplates (MPs) are excellent devices for the parallel processing of mult iple samples for the spectroscopic analysis of chromophores and turbidity, for luminometric measurements, for cell culture applications, or simply for sample storage, library organization, and other high-throughput (HTP) proc esses. Disadvantages include an ill-defined pathlength, meniscus formation, evaporation, and cross-contamination. Here, we have developed a novel MP a nd lid system which can serve to minimize these drawbacks. Cup-like lids ar e inserted into MP wells. Thereby, liquid is pushed aside. The flat bottoms of the cup-like lids guarantee a planar interface and a defined pathlength . In addition, the devised MF system allows for differential spectroscopic analysis of multiple samples comparable to measurements in tandem cuvettes. This was shown by the investigation of the binding of reduced nicotinamide adenine dinucleotide to dihydrolipoamide dehydrogenase. The MP lid system described offers a low-cost solution for standardized spectrophotometric qu antitations in any solvent compatible with the MP/lid material. In addition to the system's suitability for routine MP application, it should be advan tageous as a simple and noninvasive method, i.e., no labeling and immobiliz ation of analytes is required for detection of the interaction of molecules , for various HTP applications and drug screening purposes. (C) 2001 Academ ic Press.