Research article

Characterization and simulation of cDNA microarray spots using a novel mathematical model

Hye Young Kim^1* , Seo Eun Lee^1* , Min Jung Kim¹ , Jin Il Han¹ , Bo Kyung Kim¹ , Yong Sung Lee² , Young Seek Lee³ and Jin Hyuk Kim¹

¹  Department of Physiology, College of Medicine, Hanyang University, Seoul, 133-791, Korea

²  Department of Biochemistry and Molecular Biology, College of Medicine, Hanyang University, Seoul, 133-791, Korea

³  Division of Molecular & Life Science, College of Science and Technology, Hanyang University, Ansan, 426-791, Korea

author email corresponding author email* Contributed equally

BMC Bioinformatics 2007, 8:485doi:10.1186/1471-2105-8-485

Published:	20 December 2007

Abstract

Background

The quality of cDNA microarray data is crucial for expanding its application to other research areas, such as the study of gene regulatory networks. Despite the fact that a number of algorithms have been suggested to increase the accuracy of microarray gene expression data, it is necessary to obtain reliable microarray images by improving wet-lab experiments. As the first step of a cDNA microarray experiment, spotting cDNA probes is critical to determining the quality of spot images.

Results

We developed a governing equation of cDNA deposition during evaporation of a drop in the microarray spotting process. The governing equation included four parameters: the surface site density on the support, the extrapolated equilibrium constant for the binding of cDNA molecules with surface sites on glass slides, the macromolecular interaction factor, and the volume constant of a drop of cDNA solution. We simulated cDNA deposition from the single model equation by varying the value of the parameters. The morphology of the resulting cDNA deposit can be classified into three types: a doughnut shape, a peak shape, and a volcano shape. The spot morphology can be changed into a flat shape by varying the experimental conditions while considering the parameters of the governing equation of cDNA deposition. The four parameters were estimated by fitting the governing equation to the real microarray images. With the results of the simulation and the parameter estimation, the phenomenon of the formation of cDNA deposits in each type was investigated.

Conclusion

This study explains how various spot shapes can exist and suggests which parameters are to be adjusted for obtaining a good spot. This system is able to explore the cDNA microarray spotting process in a predictable, manageable and descriptive manner. We hope it can provide a way to predict the incidents that can occur during a real cDNA microarray experiment, and produce useful data for several research applications involving cDNA microarrays.