Chapter 1 Introduction
Helmut Beinert
University of Wisconsin‚ Institute for Enzyme Research‚ Madison‚ Wisconsin‚ USA
Figure 1. Helmut Beinert. Photograph taken during a visit to the Milwaukee EPR Center‚ a few months before his birthday. Photograph courtesy of Karen Hyde.
As the editors say in the preface‚ there has been no comprehensive volume on biological EPR for almost 30 years. Yet‚ since then this field has
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4 HELMUT BEINERT
expanded profusely. In my specialty alone‚ namely Fe-S proteins‚ where EPR is one of the principal tools‚ two whole volumes have appeared in
“Advances in Inorganic Chemistry” (Vol. 38 and 47)‚ and a third is underway; and these do not include other metal proteins such as those containing Cu‚ Ni‚ Mo or W. For other topics touching on the EPR field‚
such as nitric oxides for instance‚ a specific journal has been started‚ or an
“Oxygen Society” for oxygen and its reduction products. Moreover‚ many applications of EPR methods in the medical sciences have been explored and introduced. Thus‚ an even moderately comprehensive new treatise would have to fill many volumes. We have‚ therefore‚ urged our authors to include references to recent treatises on sub-fields - such as the ones I am citing above‚ to provide a background of literature in areas that cannot be exhaustively dealt with in the present volume. Understandably‚ after 30 years‚ the planed volume will have quite a different face. Problems discussed in the 1972 volume may have been solved‚ others may have vanished from the scene as irrelevant. On the other hand‚ our capabilities have grown enormously thanks to the ongoing research and development in instrumentation‚ methodology and the consequently advanced understanding of the phenomena observed.
Many clever minds have been involved in the development of EPR to what it is today‚ as it is obvious from the volume published to commemorate the 50th anniversary of Zavoiski’s demonstration of the phenomenon of EPR (Eaton et al.‚ 1998); however there is barely a single person who has had as much impact and influence on the practice of EPR by the general user physicist or biomedical scientist than Jim Hyde; thus‚ it seems fitting that the forthcoming volume be dedicated to Jim to his 70th birthday. In his 16 years at Varian Associates‚ where he had become product manager soon after acquiring his PhD from MIT‚ Jim and his collaborators have made EPR manageable and practical even for the non-specialist‚ have developed accessories such as special cavities‚ sample holders and flat cells for room temperature work‚ and have educated the users in their “EPR at Work”
bulletins‚ which are still useful today‚ and have given us numerous practical hints. No wonder that‚ in 1975‚ the community of users was stunned by the message that Varian was withdrawing from the EPR field altogether. Many asked the question whether this would mean that Jim’s expertise‚
inventiveness and enthusiasm for improving and extending EPR capabilities might be lost forever‚ as there was no other manufacturer in sight in the USA that could have taken over Jim and his task. Fortunately‚ at this point‚
another talent came into the picture‚ which‚ to the community’s delight‚ was able to turn the tide‚ namely Harold Swartz’s organizational and diplomatic talent and skills. He succeeded in winning Jim for the fledgling ESR Center at Milwaukee’s Medical College of Wisconsin‚ which has since flourished
INTRODUCTION 5
and developed into a unique‚ national EPR facility‚ generously supported by the NIH and known worldwide in EPR circles. Thus‚ with little interruption‚
Jim could continue to follow his ideas about extending the capabilities of EPR. A time-domain spectrometer was built to determine relaxation times;
multi-frequency stations were set up; the necessity for magnetic field modulation was eliminated by introduction of multiquantum EPR; bimodal cavities for X and Q band were built for ELDOR; as alternative to cavities‚
which pose many restrictions on sample size and shape‚ the loop-gap resonator (LGR) was developed for several frequencies; data output and recording was radically streamlined by introducing time-locked sub- sampling (TLSS)‚ which allows one to acquire‚ in a single sweep‚ all in- and out-of-phase harmonics; and viable alternatives to the rare and expensive klystrons were built.
As not every investigator can afford having all the accessories and modifications in his lab or the know-how to use them‚ the ESR Center is open for visitors‚ who have been coming in regularly from this country and all parts of the world. The development of commercial versions of spectrometers is a laborious‚ expensive and slow process. Thus‚
modifications in these instruments to accommodate progress in design and capabilities is not lightly undertaken. The innovations developed at the Center can‚ therefore‚ not be expected to instantly appear in instruments on the market. It may take years. However‚ this should not detract from the merit of having the principles of these improvements established‚ their feasibility proven and any complications resolved and having this documented in the literature.
With a salute to Jim Hyde‚ master of microwaves‚ inventor‚ innovator and optimizer‚ at his 70th birthday‚ the EPR community hopes that Jim will be able to contribute for many more years to the joint good of EPR spectroscopy and of those who benefit from its practice and applications.
REFERENCES
Eaton‚ G. R.‚ Eaton‚ S. S.‚ Salikhov‚ K. M. (1998). Foundations of Modern EPR‚ World Scientific‚ Singapore.
