Preface

In recent years, luminescence technology, as well as fluorescence technology, has been applied in the medical and life science research fields for the measurement of biomolecules and for imaging *in vivo* and at the cellular level using luminescent markers as probes. The major difference between luminescence and fluorescence is the source of energy that excites the photon emitter, whether it is produced from a chemical reaction or from light. Therefore, luminescence measurement eliminates the problems of increased background due to autofluorescence and phototoxicity to living organisms in fluorescence measurement. However, fluorescence is superior in terms of emission intensity and image resolution. Now, with the development of luminescent and fluorescent materials and measurement techniques, the two measurement methods are developing as complementary technologies.

Luminescence is a phenomenon that can be interpreted in both physical and chemical terms. *Bioluminescence* in living organisms also falls into the category of chemical luminescence, since it is a phenomenon caused by chemical reactions occurring within the organism. The title of this book is *Bioluminescence* because it deals with luminescence of organisms mainly from the biological aspect, but of course it also includes the physical, chemical, and technical areas of luminescence. Following the previous series *Bioluminescence*: *Analytical Application and Basic Biology*, this book contains reviews and original articles in the fields of technology and biology.

Section 1 is focused on *Bioluminescence Techniques* contains four chapters. Chapter 1 contains a review article on fluorescent reporter proteins for monitoring the redox state of *Drosophila* cells and the application of fluorescent nanocrystals in cell lines. Chapter 2 contains a review article on imidazopyrazinone-type luciferin analogs that are specifically luminescent in the presence of human serum albumin rather than luciferase derived from luminescent organisms. The properties of the substrate and luminescence system for measuring low levels of human serum albumin as a biomarker for several diseases were presented. Chapter 3 contains a review article on firefly luciferin analogs that emit red-shifted near-infrared light. The new luciferin analog was combined with a mutant luciferase optimized for the analog and applied to *in vivo* imaging of mouse and marmoset tissues. The result was 10- to 1,400-fold increase in luminescence intensity, enabling detection of single-cell signals from mouse lungs and real-time imaging of marmoset brains at video rates. Chapter 4 is an original article in which the promoter activity of the adenylyl cyclase A gene in the fruiting body formation of the cellular slime mold *Dictyostelium* was analyzed using dual-color *bioluminescence* imaging techniques. By using two brightly modified firefly luciferases (green and red), the two promoter activities (proximal and distal regions) during the formation process from cell to fruiting body were imaged without the influence of autofluorescence.

Section 2 *Bioluminescent Organisms* contains three chapters. Chapter 5 is both a review and an original article. First, the concepts and practices of animal conservation and insect translocation are reviewed, and an original case study of a firefly translocation program in Thailand based on flashing patterns, mating behavior, and genetic population structure analyses is presented. Chapter 6 contains a review article on the origin of luciferin in marine luminescent organisms. Although the biosynthetic pathway of luciferin is not well understood, only a few luciferins of copepod and cyprid are known to be synthesized intrinsically from amino acids. On the other hand, most marine organisms acquire luciferin by preying on copepods and cyprid that make luciferin intrinsically. Chapter 7 is a review article on the ecology and behavior of bioluminescent organisms distributed from sea to land and taxonomically arranged from bacteria to vertebrates (fish). Almost all phyla are covered, and recent topics on new bioluminescent responses in fungi are also presented.

We would like to express our appreciation to the chapter authors for their outstanding work and also to Ms. Dolores Kuzelj, the Author Service Manager at IntechOpen, for effective communication and assistance during the preparation of this book.

> **Hirobumi Suzuki** Kogakuin University, Tokyo, Japan

**Katsunori Ogoh** Olympus Corporation, Tokyo, Japan Section 1
