Preface [Hot Topic: Microarray-Based Technologies and Beyond (Guest Editors: Shao Q. Yao / Sridar V. Chittur)]

The post-genomic era heralds a multitude of challenges for chemists and biologists alike, with the study of protein functions at the heart of much research. The elucidation of protein structure, localization, stability, post-translational modifications and protein interactions will steadily unveil the role of each protein and its associated biological function in the cell. The push to develop new technologies has necessitated the integration of various disciplines in science. This special issue of CCHTS will cover some of the emerging technologies developed in recent years in the areas of combinatorial chemistry and high-throughput screenings, with special focuses on microarray-based and other promising technologies. One of most promising methods used in current proteomics research is the microarray-based techniques, which enable tens of thousands of biological assays to be carried out simultaneously on a microscope-size glass slide (2.5 cm × 7.5 cm) in a highly parallel and extremely high-throughput fashion. DNA- and Protein-based microarrays have received a great deal of interests from scientists working in life sciences-related fields. Other types of microarrays, namely those based on synthetic chemical entities (i.e. small molecules, peptides, carbohydrates and lipids, etc), are equally important as useful tools for potential highthroughput screenings and drug discovery. Sridar Chittur discussed the currently available DNA microarrays that have various applications in gene expression and genotyping studies. Also discussed are the novel formats of microarrays being used that push the limits of this technology to achieve higher throughput. Predlki et al. from Protometrix highlighted some of the major challenges faced when using protein microarray technologies for potential high-throughput drug discovery and development. Protometrix, by the way, is the biotech company which successfully commercialized the “yeast proteome array”. While fabricating a functional protein microarray is difficult, the generation of a peptide-based microarray is considerably much more straightforward, mainly because peptides are a lot more stable than proteins - they don't get denatured and subsequently lose their biological properties easily. Consequently, peptide arrays have increasingly become an important tool for highthroughput screening of potential protein substrates, binders and even inhibitors. Some of the applications of peptide array are reviewed by Yao et al. Unlike proteins and peptides, which are typically considered poor drug candidates due to their limited bioavailability, small molecules are the focus of the pharmaceutical industry and drug discovery. No wonder small molecule micraorrays, as Chang et al. discussed in their timely review, hold a great potential for direct and high-throughput discovery of “drugable” drugs against a variety of protein target. Carbohydrate-protein interaction plays an important role for biological recognitions, in their review; Shin et al. convincingly illustrated how microarray technologies based on carbohydrates could be used to study carbohydrate-binding proteins and carbohydrate-processing enzymes, the diagnosis of diseases and even drug discovery. Hewitt et al. present a well-investigated and thorough summary of issues including Tissue Microarray (TMA) design, construction, sectioning, staining, scoring and statistical analysis, as well as mention of developing techniques including image analysis and their own novel immunodetection technique. John Cowell presents a detailed review of the use of BAC arrays in human genetics and chronicles the development of this technology over the last 50 years. The benefit of a physical map approach to the human genome rather than the expression map approach of many investigators using array CGH on expression cDNA platforms is also discussed in this review. Lastly, by looking beyond the microarray-based technologies, Yeo et al. discussed an emerging area in modern chemical biology - bioimaging, which sheds lights on how precisely proteins behave inside a living, cellular environment. Various chemical approaches for in vivo labeling of proteins such that they become “visible” were highlighted in the review.