Electrochemical and Spectrochemical Studies of Biological Redox Components
A d v a n c e s in C h e m i s t r y S e r i e s No. 201 Karl M . K a d i s h , Editor University of Houston Based on a symposium sponsored by the ACS Division of Analytical Chemistry of the American Chemical Society This in-depth treatment of biological redox components brings together the research of renowned scientists from diverse backgrounds who work on closely related topics. Both techniqueand problem-oriented researchers contribute to the 29 chapters, which discuss such subjects as electron transfer in porphyrins, heme proteins, cyctochrome oxidase and copper proteins. The presentations include reviews as well as reports of original research not published before. This volume is useful to both students and active researchers in the field. CONTENTS Thin-Layer Electrochemical Techniques · Heterogeneous Electron Transfer Kinetic Parameters · Temperature Dependence of Reduction Potentials · Surface Enhanced Raman Spectroscopy · Redox Potentials in Mononuclear and Dinuclear Copper Cryptâtes · Binuclear Copper (I) Complexes as Mimics of Protein Active Sites · Heterogeneous Electron Transfer Properties of Cytochrome c · Rapid Electron Transfer Reactions of Metalloproteins · Cytochrome C3 of Desulfovibrio vulgaris * Electrode Reactions of Protein Prosthetic Groups · Energy Levels of Metallophthalocyanines · Iron and Cobalt Porphodimethenes · Redox Tuning of Iron Porphyrins · Protoporphyrin IX Compared to Synthetic Models · Iron (I) and Iron (IV) Porphyrins • Magnetic Resonance of Oxidized Metalloporphyrins · Models of Cytochromes b 6 · Aliphatic Thioethers as Models for Biological Electron Transfer · Reactions of Chlorpromazine Cation Radical with Physiological Nucleophiles · Reduced Pterin Cofactors · Spectral and Redox Characteristics of Chlorophyll Radicals · Photosynthesis and Electron Transfer in Bioenergetic Membranes · Enzymatic and Electrochemical Reduction of Dioxygen * Superoxide Ion in Aprotic Media · Electrocatalytic Reduction of Molecular Oxygen · Cytochrome Oxidase Study · Utility of Proton Hyperfine Shifts · 3.5-Di-ferr-butylcatecholato and o-Semiquinonato Complexes · Catalytically Active Molybdenum;— Catechol Complexes 752 pages (1982) Clothbound US & Canada $ 8 9 . 9 5 Export $ 1 0 7 . 9 5 LC 82-11487 ISBN 0-8412-0661 -9 Order from: Distribution Office — 23 American Chemical Society 1155 Sixteenth Street, N.W. Washington, D.C. 20036 or CALL TOLL FREE 8 0 0 - 4 2 4 - 6 7 4 7 and use your credit c a r d .
r a t i o n i n t o t h e p r e d i c t i o n (analytical) e q u a t i o n , 2) assigning empirical coefficients, a n d 3) t e s t i n g t h e applicability ( r o b u s t n e s s ) t o t h e r a n g e of s a m p l e s . Even though the absorption bands are b r o a d , for q u a n t i t a t i o n , w a v e l e n g t h r e p r o d u c t i o n is essential. Also, for ins t r u m e n t s using c o m p o s i t e d reflect a n c e t e r m calculations, t h e increm e n t s b e t w e e n close p a i r s or t r i o s of w a v e l e n g t h s a r e a p a r t of t h e calibrat i o n a n d m u s t n o t vary. In p r a c t i c e , if available, s p e c t r o scopic i n f o r m a t i o n on t h e a n a l y t e a n d o t h e r major c o n s t i t u e n t s of t h e s a m p l e is u s e d along with t h e m u l t i v a r i a t e statistical m e t h o d s t o choose t h e w a v e l e n g t h s t o be used. P r i o r work w i t h t h e s a m e a n a l y t e in similar m a trices can serve as a s t a r t i n g p o i n t in t h i s selection. However, t h e r e a r e also cases w h e r e t h e c h e m i c a l basis of a s a m p l e ' s i m p o r t a n t c h a r a c t e r i s t i c s is n o t defined b u t t h a t t h e n e a r - i n f r a r e d reflectance analyzer can still b e used. F o r such cases, we m u s t rely entirely u p o n correlation t r a n s f o r m a t i o n s t a tistics. O t h e r calculation m e t h o d s h a v e i n c l u d e d l e a s t - s q u a r e s curve fitting, p r i n c i p l e c o m p o n e n t , l a t e n t variables, a n d row r e d u c t i o n (9-13).
Role of analytical chemists in NIRA Since correlation t r a n s f o r m a t i o n m a y uncover a useful r e l a t i o n s h i p t h a t m a y n o t be obvious from k n o w n t h e o ry, it m a y be necessary t o p u t aside one's pride and try this approach. H e r e is w h e r e c o n t r i b u t i o n s can be m a d e . G o o d solid analytical sense a n d m e t h o d o l o g y a r e also n e e d e d t o o b t a i n highly reliable a n d a p p r o p r i a t e reference d a t a from which specific N I R A m e t h o d s e m e r g e for r a p i d a n d r o u t i n e a p p l i c a t i o n . T h e analytical reference m e t h o d d e v e l o p e d for t h i s p u r p o s e n e e d n o t be r a p i d a n d practical b u t j u s t a c c u r a t e . T h i s is a d e p a r t u r e from t h e u s u a l criteria a n d m o t i v a t i o n for analytical method development. One of t h e m o s t e x t r e m e e x a m p l e s of such a n a p p r o a c h is t h e use of solid s t a t e c a r b o n 13 N M R d a t a by B a r t o n a n d coworkers (14) t o o b t a i n s t r u c t u r a l information concerning natural produ c t s . N e a r - i n f r a r e d reflectance d a t a correlated to the quantitative expression of s t r u c t u r e allows s u b s e q u e n t r a p i d a n a l y s e s of large n u m b e r s of similar n a t u r a l p r o d u c t s a m p l e s , a p propriate quality assessment, and sorting for p a r t i c u l a r e n d use. As p r o b l e m solvers we n e e d every available tool a n d c a n n o t afford t o overlook a p o t e n t i a l l y v a l u a b l e one such as N I R A . G r e a t e r chemical i n p u t a n d ins i g h t will u n d o u b t e d l y aid in t h e recognition of its legitimacy.
References (1) Fuller, M. P.; Griffiths, P. R. Anal. Chem. 1978,50,1906.
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(2) Kaye, W. Spectrochim. Acta 1954,6, 257. (3) Kaye, W. Spectrochim. Acta 1955,7, 181. (4) Whetsel, K. B. Appl. Spectrosc. Rev. 1968,2(1), 1. (5) Ben-Gera, L; Norris, K. H. Israel J. Agr. Res. 1968,18,125. (6) Wetzel, D. L.; Mark, H. "Scanning NIR of Grains, Oilseeds, and Their Components"; ICC Symposium: Use of NearInfrared Techniques, 6th World Bread Congress, Winnipeg, 1978; Paper No. S2.1. (7) Wetzel, D. L. "Particle Size as a Variable in Near-Infrared Reflectance Analysis," American Association of Cereal Chemists, 62nd Annual Meeting, San Francisco, Calif., 1977; Paper No. 44. (8) Stark, E. W. "State of the Art of NIRA Instruments"; Research Conference on Diffuse Reflectance Spectroscopy, Chambersberg, Pa., August 1982. (9) Hamid, Α.; McClure, W. F.; Whitaker, T. B. Am. Lab. 1981,13 (3), 108. (10) Hruschka, W. R.; Norris, Κ. Η. Appl. Spectra. 1982 36 (3), 261. (11) Hruschka, W. R.; Martens, H. "Prin cipal Component Analysis Predicts Pro tein and Moisture Content from Near In frared Spectra of Ground Wheat," Pitts burgh Conference on Analytical Chemis try and Applied Spectroscopy, Atlantic City, N.J., 1982; Paper No. 375. (12) Martens, H.; Jensen, S. A. "Proceed ings of the 7th World Cereal and Bread Congress," Prague Czechoslovakia, 1982, Paper No. S.45; Elsevier: Amsterdam, in press. (13) Honigs, D. E.; Hieftje, G. M.; Hirschfeld, T. "Near Infrared Reflectance Analysis (NIRA) Correlation Methods and Performance," Pittsburgh Confer ence on Analytical Chemistry and Ap plied Spectroscopy, Atlantic City, N.J. 1982; Paper No. 380. (14) Barton, F. E., Ill; Akin, D. E., Himmelsbach, D. S.; Windham, W. R. "Ab stracts of Papers"; 186th National Meet ing of the American Chemical Society, Washington, D.C, Aug. 28-Sept. 2,1983; American Chemical Society: Washing ton, D.C, 1983; CELL 11.
David L. Wetzel, professor at Kansas State University, joined the grain science department there in 1973 to develop analytical methods for ce real-based foods and the grain pro cessing industry. His research inter ests include HPLC, laser diffractometry, and NIRA. His PhD graduate work was in analytical chemistry, and he held a number of teaching and re search positions prior to joining KSU. He currently writes a column on instrumentation for Cereal F o o d s World.
