surface of molecules. Variants can be recognized only when one or more preconditions are met: S t r u c t u r a l variations occur at the surface of the molecule, structural variations alter the external structure of the variant, or internal points of variation are re vealed by conformational changes during the chromatographic step. Detection in LC-IA A n u m b e r of cases have been de scribed above in which antigen is de tected directly, generally at concen trations > 1 ng/mL. At lower levels of antigen it is necessary to use some type of indirect detection method. Off-line methods based on enzyme amplification and competitive bind ing radioimmunological assays have already been described. Assays in which the ligand is tagged with an acridinium ester are another alterna tive (32). Detection in these systems is based on chemiluminescence. Sev eral methods based on enzyme am plification, fluorescence, and chemiluminescence have been de scribed in which immunodiscrimination, chromatography, and detection were combined. In the case of enzyme-amplified immunological a s s a y s , c h r o m a t o graphic systems have been used to e n h a n c e detection of t h e enzyme product by removing interfering sub stances. Two-dimensional chromato graphic resolution of NADH with flow-amperometric detection in a ho mogeneous EMIT assay is one exam ple (33). Linear calibration plots were obtained over the range of 0.55-7.5 ng/mL. A problem with this assay is that the ability of the antibody to in hibit enzyme activity of the enzymelabeled digoxin is poor, producing a substantial blank. ELISA may also be treated this way. Conversion of phenyl phosphate to phenol by alka line phosphatase conjugated to the second antibody in a conventional ELISA was monitored by LC with electrochemical detection (34, 35). The lower detection limit was - 1 ng/ mL. Sensitivity was increased by 3 orders of magnitude by carrying out the assay in a 7 0 - μ ι capillary and transferring the entire contents of the capillary to the chromatography column after product formation (36). The assay requires 25 min, has a lin ear range of 5 orders of magnitude, and has a detection limit of 4.6 χ 10" 2 1 mol or 2800 ± 150 molecules. Assays equivalent to the classical ELISA have also been achieved by carrying out the individual steps in a flow-through immunosorbent car tridge. The sandwich for a mouse
Cholinesterases
Trends in Chemical Consulting
R
estructuring in the chemical industry has created a wealth of opportunities for consultants. Companies are now more willing to seek outside help than in the past as they recognize the value of experienced specialists. But what constitutes the efficient use of a consultant? And is consulting for you? Trends in Chemical Consulting explores these issues through contributions from chemical consul tants, those who have used the services of a consultant, and participants in cooperative ar rangements. Presentations focus on those considerations specific to consulting relation ships between scientific professionals. Chemists, chemical engineers, and other sci entific professionals in support areas to the chemical industry will find this an indispensible resource of information on chemical consulting.
Contents • Consulting to the Chemical Industry • Industrial Expectations for Consultants and Con sulting Services • Understanding, Selecting, Managing, and Compen sating Consultants • An Academic Perspective on Consulting • University-Industrial Relationships • Accessing Federal Laboratories Know-How • What Consulting Practices Look Like • Defining and Marketing Your Consulting Specialty • Opportunities for Retired Chemists • Using Consultants to Interpret Regulatory Initiatives • Major Chemical Company Retirees as Consultants and Market Developers • Robotic Servicing on the Space Station Freedom • Consultation in Sensory Evaluation • Chemical information Consultants Charles S. Sodano and David M. Sturmer, Editors
174 pages (1991) Paperbound ISBN 0-8412-2106-5
$29.95
• • •American • Chemical « • Society • • • I
Structure, Function, Mechanism, Genetics, and Cell Biology
P
resenting the proceedings of the Third International Meeting on Cholinesterases, this inaugural volume in the Conference Proceedings Series offers a wealth of new in formation on current and future cholinesterase research, including important advances re sulting from new concepts and methodologies such as monoclonal antibodies and molecular genetics. The volume's 49 full papers and 140 poster papers are divided into six sections covering: • • • •
Polymorphism and Structure of Cholinesterases Cellular Biology of Cholinesterases Gene Structure and Expression of Cholinesterases Catalytic Mechanism of Cholinesterases: StructureFunction Relationships of Anticholinesterase Agents, Nerve Agents, and Pesticides • Pharmacological Utilization of Anticholinesterase Agents. Neuropathology of Cholinergic Systems • Noncholinergic Roles of Cholinesterases
This volume will be of great interest to a broad spectrum of readers, including those in terested in the evolution of cholinesterase ca talysis, researchers developing agricultural chemicals, scientists seeking up-to-date infor mation on the treatment of glaucoma and such neurological diseases as Alzheimer's dis ease and myasthenia gravis, those interested in the design of drugs to bind the enzyme it self or to cholinergic receptors, as well as those who follow the progress toward com plete structure elucidation of cholinesterases. Jean Massoulie, Centre National de la Recherche Scientifique, Editor Francis Bacou, Institut National de la Recherche Agronomique, Editor Eric Barnard, Medical Research Council, Editor Arnaud Chatonnet, Institut National del la Recherche Agronomique, Editor Bhupendra P. Doctor, Walter Reed Army Institute of Research, Editor Daniel M. Quinn, University of Iowa, Editor Conference Proceedings Series 414 pages (1991) Clothbound ISBN 0-8412-2008-5 $89.95 Ο · R · D · Ε · R
F · R · Ο · M
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ANALYTICAL CHEMISTRY ', VOL. 65, NO. 1, JANUARY 1, 1993 · 23 A
