By the end of the 1980s only two microtubule-dependent motors, the plus end-directed kinesin and the minus end-directed cytoplasmic dynein, had been identified. At the time, these two motors seemed almost sufficient to explain directional motility events on polar microtubule tracks in the cell. No- theless, shortly after, the tip of the iceberg began to emerge with the identi- cation of proteins containing in their sequences a domain found in kinesin. This domain, called the “motor domain,” conferred on these proteins the essential property of moving on microtubules, using the energy derived from ATP hydro- sis. Since then, the identification of new proteins belonging to the kinesin superfamily of microtubule-dependent motors has gone at such a pace that nowadays more than 200 entries with motor domain sequences are deposited in the database. Kinesin family members are found in all eukaryotic org- isms tested. They present a wide range of domain organizations with a motor domain located at different positions in the molecule. Their motility prop- ties are also variable in directionality, velocity, and such other characteristics as bundling activity and processivity. Finally, and most important, they p- ticipate in a multitude of cellular functions. Our understanding of many cel- lar events, such as mitotic spindle assembly and neuronal transport, to cite only two, has progressed substantially in the last few years thanks to the id- tification of these motors.

Microtubules are essential components of the cytoskeleton, and play critical roles in a variety of cell processes, including cell shaping, intracellular tracking, cell division, and cell migration. Microtubule Protocols presents a comprehensive collection of essential and up-to-date methods for studying both the biology of microtubules and the mechanisms of action of microtubule-interacting drugs. The straightforward presentation of readily reproducible protocols is a hallmark of the Methods in Molecular MedicineTM series, and is evident in this volume. Methods presented range from the purification and characterization of microtubule proteins, analysis of post-translational modifications of tubulin, and determination of microtubule structure, to the visualization of microtubule and spindle behavior, measurement of microtubule dynamics, and examination of microtubule-mediated cellular processes. Both basic scientists and clinical researchers will benefit from this collection of state-of-the-art protocols for microtubule research.

Direct cell–cell communication is a common property of multicellular organisms that is achieved through membrane channels which are organized in gap junctions. The protein subunits of these intercellular channels, the connexins, form a multigene family that has been investigated in great detail in recent years. It has now become clear that, in different tissues, connexins speak several languages that control specific cellular functions. This progress has been made possible by the availability of new molecular tools and the improvement of basic techniques for the study of membrane channels, as well as by the use of genetic approaches to study protein function in vivo. More important, connexins have gained visibility because mutations in some connexin genes have been found to be linked to human genetic disorders. Connexin Methods and Protocols presents in detail a collection of te- niques currently used to study the cellular and molecular biology of connexins and their physiological properties. The field of gap junctions and connexin research has always been characterized by a multidisciplinary approach c- bining morphology, biochemistry, biophysics, and cellular and molecular biology. This book provides a series of cutting-edge protocols and includes a large spectrum of practical methods that are available to investigate the fu- tion of connexin channels. Connexin Methods and Protocols is divided into three main parts.

Over the past two decades experimental studies have solidified the int- pretation of the cytoskeleton as a highly dynamic network of microtubules, actin microfilaments, intermediate filaments, and myosin filaments. Rather than a network of disparate fibers, these polymers are often interconnected and display synergy, which is the combined action of two or more cytoskeletal polymers to achieve a specific cellular structure or function. Cross-commu- cation among cytoskeletal polymers is thought to be achieved through cytoskeletal polymer accessory proteins and molecular motors that bind two or more cytoskeletal polymers. Development of the modern concept of the cytoskeleton is a direct o- growth of advances in experimental tools and reagents that are available to cell and molecular biologists. Technological advances and refinements in cell imaging have made it possible to selectively image a single cytoskeletal po- mer and monitor its dynamics through the use of fluorescence probes in vitro and in vivo. Two decades ago, cytoskeletal research was limited to a few perturbation reagents that included colchicine and cytochalasin. Today, the perturbation arsenal has expanded to a highly selective group of reagents that includes Taxol, nocodazole, benomyl, latrunculin, jasplakinolide, and such endogenous proteins as gelsolin. These reagents enable the investigator to selectively perturb or destroy a cytoskeletal polymer while leaving other cytoskeletal polymers intact. Site-specific monoclonal antibodies that target a specific cytoskeletal polymer have proven to be highly selective affinity tools for cytoskeletal research.

Nucleases, enzymes that restructure or degrade nucleic acid polymers, are vital to the control of every area of metabolism. They range from “housekeeping” enzymes with broad substrate ranges to extremely specific tools (1). Many types of nucleases are used in lab protocols, and their commercial and clinical uses are expanding. The purpose of Nuclease Methods and Protocols is to introduce the reader to some we- characterized protein nucleases, and the methods used to determine their activity, structure, interaction with other molecules, and physiological role. Each chapter begins with a mini-review on a specific nuclease or a nuclease-related theme. Although many chapters cover several topics, they were arbitrarily divided into five parts: Part I, “Characterizing Nuclease Activity,” includes protocols and assays to determine general (processive, distributive) or specific mechanisms. Methods to assay nuclease products, identify cloned nucleases, and determine their physiological role are also included here. Part II, “Inhibitors and Activators of Nucleases,” summarizes assays for measuring the effects of other proteins and small molecules. Many of these inhibitors have clinical relevance. Part III, “Relating Nuclease Structure and Function,” provides an overview of methods to determine or model the 3-D structure of nucleases and their complexes with substrates and inhibitors. A 3-D structure can greatly aid the rational design of nucleases and inhibitors for specific purposes. Part IV, “Nucleases in the Clinic,” summarizes assays and protocols suitable for use with t- sues and for nuclease based therapeutics.

We must unashamedly admit that a large part of the motivation for editing Genomics Protocols was selfish. The possibility of assembling in a single volume a unique and comprehensive collection of complete protocols, relevant to our work and the work of our colleagues, was too good an opportunity to miss. We are pleased to report, however, that the outcome is something of use not only to those who are experienced practitioners in the genomics field, but is also valuable to the larger community of researchers who have recognized the potential of genomics research and may themselves be beginning to explore the technologies involved. Some of the techniques described in Genomics Protocols are clearly not restricted to the genomics field; indeed, a prerequisite for many procedures in this discipline is that they require an extremely high throughput, beyond the scope of the average investigator. However, what we have endeavored here to achieve is both to compile a collection of procedures concerned with geno- scale investigations and to incorporate the key components of “bottom-up” and “top-down” approaches to gene finding. The technologies described extend from those traditionally recognized as coming under the genomics umbrella, touch on proteomics (the study of the expressed protein complement of the genome), through to early therapeutic approaches utilizing the potential of genome programs via gene therapy (Chapters 27–30).

Immunotoxins represent a new class of human therapeutics that have widespread applications and a potential that has not yet been fully recognized since they were first conceived of by Paul Ehrlich in 1906. The majority of advances in the development and implementation of immunotoxins has occurred over the last 20 years. The reasons for this use of immunotoxins in basic science and clinical research are the powerful concurrent advances in genetic engineering and receptor physiology. Recombinant technology has allowed investigators to produce sufficient quantities of a homogeneous c- pound that allows clinical trials to be performed. The identification of specific receptors on malignant cell types has enabled scientists to generate immunotoxins that have had positive results in clinical trials. As more cellular targets are identified in coming years, additional trials will be conducted in different disease states affecting still larger patient populations. Modulation of the immune system to decrease the humoral response to immunotoxins may improve their overall efficacy. As increasingly more effective compounds are generated, it will be necessary to decrease the local and systemic toxicity - sociated with these agents, and methods for doing so are presently being - veloped. The work presented in Immunotoxin Methods and Protocols focuses on three specific areas of immunotoxin investigation that are being conducted by experts throughout the world. The first section describes the construction and development of a variety of immunotoxins.