Protein Fluorescence

The intrinsic or natural fluorescence of proteins is perhaps the most complex area of biochemical fluorescence. Fortunately the fluorescent amino acids, phenylalanine, tyrosine and tryptophan are relatively rare in proteins. Tr- tophan is the dominant intrinsic fluorophore and is present at about one mole % in protein. As a result most proteins contain several tryptophan residues and even more tyrosine residues. The emission of each residue is affected by several excited state processes including spectral relaxation, proton loss for tyrosine, rotational motions and the presence of nearby quenching groups on the protein. Additionally, the tyrosine and tryptophan residues can interact with each other by resonance energy transfer (RET) decreasing the tyrosine emission. In this sense a protein is similar to a three-particle or mul- particle problem in quantum mechanics where the interaction between particles precludes an exact description of the system. In comparison, it has been easier to interpret the fluorescence data from labeled proteins because the fluorophore density and locations could be controlled so the probes did not interact with each other. From the origins of biochemical fluorescence in the 1950s with Prof- sor G. Weber until the mid-1980s, intrinsic protein fluorescence was more qualitative than quantitative. An early report in 1976 by A. Grindvald and I. Z. Steinberg described protein intensity decays to be multi-exponential. Attempts to resolve these decays into the contributions of individual tryp- phan residues were mostly unsuccessful due to the difficulties in resolving closely spaced lifetimes.

The intrinsic or natural fluorescence of proteins is perhaps the most complex area of biochemical fluorescence. Fortunately the fluorescent amino acids, phenylalanine, tyrosine and tryptophan are relatively rare in proteins. Tr- tophan is the dominant intrinsic fluorophore and is present at about one mole % in protein. As a result most proteins contain several tryptophan residues and even more tyrosine residues. The emission of each residue is affected by several excited state processes including spectral relaxation, proton loss for tyrosine, rotational motions and the presence of nearby quenching groups on the protein. Additionally, the tyrosine and tryptophan residues can interact with each other by resonance energy transfer (RET) decreasing the tyrosine emission. In this sense a protein is similar to a three-particle or mul- particle problem in quantum mechanics where the interaction between particles precludes an exact description of the system. In comparison, it has been easier to interpret the fluorescence data from labeled proteins because the fluorophore density and locations could be controlled so the probes did not interact with each other. From the origins of biochemical fluorescence in the 1950s with Prof- sor G. Weber until the mid-1980s, intrinsic protein fluorescence was more qualitative than quantitative. An early report in 1976 by A. Grindvald and I. Z. Steinberg described protein intensity decays to be multi-exponential. Attempts to resolve these decays into the contributions of individual tryp- phan residues were mostly unsuccessful due to the difficulties in resolving closely spaced lifetimes.

Fluorescence methods are being used increasingly in biochemical, medical, and chemical research. This is because of the inherent sensitivity of this technique. and the favorable time scale of the phenomenon of fluorescence. 8 Fluorescence emission occurs about 10- sec (10 nsec) after light absorp tion. During this period of time a wide range of molecular processes can occur, and these can effect the spectral characteristics of the fluorescent compound. This combination of sensitivity and a favorable time scale allows fluorescence methods to be generally useful for studies of proteins and membranes and their interactions with other macromolecules. This book describes the fundamental aspects of fluorescence. and the biochemical applications of this methodology. Each chapter starts with the -theoreticalbasis of each phenomenon of fluorescence, followed by examples which illustrate the use of the phenomenon in the study of biochemical problems. The book contains numerous figures. It is felt that such graphical presentations contribute to pleasurable reading and increased understand ing. Separate chapters are devoted to fluorescence polarization, lifetimes, quenching, energy transfer, solvent effects, and excited state reactions. To enhance the usefulness of this work as a textbook, problems are included which illustrate the concepts described in each chapter. Furthermore, a separate chapter is devoted to the instrumentation used in fluorescence spectroscopy. This chapter will be especially valuable for those perform ing or contemplating fluorescence measurements. Such measurements are easily compromised by failure to consider a number of simple principles.

In Fluorescent Protein-Based Biosensors: Methods and Protocols, experts in the field have assembled a series of protocols describing several methods in which fluorescent protein-based reporters can be used to gain unique insights into the regulation of cellular signal transduction. Genetically encodable fluorescent biosensors have allowed researchers to observe biochemical processes within the endogenous cellular environment with unprecedented spatiotemporal resolution. As the number and diversity of available biosensors grows, it is increasingly important to equip researchers with an understanding of the key concepts underlying the design and application of genetically encodable fluorescent biosensors to live cell imaging. Written in the successful Methods in Molecular Biology series format, chapters include introductions to their respective topics, lists of the necessary materials and reagents, step-by-step, readily reproducible protocols, and notes on troubleshooting and avoiding known pitfalls. Authoritative and easily accessible, Fluorescent Protein-Based Biosensors: Methods and Protocols promises to be a valuable resource for researchers interested in applying current biosensors to the study of biochemical processes in living cells as well as those interested in developing novel biosensors to visualize other cellular phenomena.

Fluorescence and phosphorescence are proving to be extremely sensitive probes for elucidating conformation of proteins and nucleic acids and for studying molecular interactions. Newer instrumentation and techniques hold forth great promise for the future of these luminescence methods in biopolymer research. It must be noted, however, that the discovery that certain amino acids, purines, and pyrimidines emit fluorescence or phosphorescence is relatively recent, occurring within the last decade. Professor Konev is one of the pioneers in the application of these procedures to biopolymers and is highly qualified to write about this subject. This book, though written largely as a monograph of the author's own contributions, is also an excellent review of the subject. Of particular interest are the references to many important Russian papers in this field which have not been recognized in the Western literature. It is apparent from this book that fluorescence and phosphorescence methods are being used about as widely in Russia as elsewhere in the world and that we must not overlook these im portant contributions. Konev's studies on protein fluorescence have been widely recognized. It is of interest to learn about these and other of his applications. The last part of the book, which deals with fluorescence as a means to probe into the structure and conforma tion of macromolecules in intact cells, is most interesting. Aside from published symposia this book is the first written specifically about luminescence of biopolymers. Sidney Udenfriend Bethesda. Maryland May, 1967 v CONTENTS Introduction . • • . . . . . . . . . • . . . . . . . . . .

This is a new edition (first, 1973) of an introduction to the principles and applications of all phases of luminescence spectroscopy. Contains (all rewritten) chapters on general aspects of luminescence, instrumentation, effects of molecular structure and environment, inorganic analysis and phosphorescence. The second edition also introduces new topics such as process, applications, bioprocess monitoring and biotechnology methods, soild surface luminescence and pesticide analysis, providing expanded coverage on chemiluminescence and environmental analysis and updates information on equipment, supplies newer references and more.

One of the major challenges of modern biology and medicine consists in finding means to visualize biomolecules in their natural environment with the greatest level of accuracy, so as to gain insight into their properties and behaviour in a physiological and pathological setting. This has been achieved thanks to the design of novel imaging agents, in particular to fluorescent biosensors. Fluorescence Biosensors comprise a large set of tools which are useful for fundamental purposes as well as for applications in biomedicine, drug discovery and biotechnology. These tools have been designed and engineered thanks to the combined efforts of chemists and biologists over the last decade, and developed hand in hand together with imaging technologies. This volume will convey the many exciting developments the field of fluorescent biosensors and reporters has witnessed over the recent years, from concepts to applications, including chapters on the chemistry of fluorescent probes, on technologies for monitoring protein/protein interactions and technologies for imaging biosensors in cultured cells and in vivo. Other chapters are devoted to specific examples of genetically-encoded reporters, or to protein and peptide biosensors, together with examples illustrating their application to cellular and in vivo imaging, biomedical applications, drug discovery and high throughput screening. Contributions from leading authorities Informs and updates on all the latest developments in the field

A Top 25 CHOICE 2016 Title, and recipient of the CHOICE Outstanding Academic Title (OAT) Award. How much energy is released in ATP hydrolysis? How many mRNAs are in a cell? How genetically similar are two random people? What is faster, transcription or translation?Cell Biology by the Numbers explores these questions and dozens of others provid