Multidimensional Nuclear Magnetic Resonance Studies of Materials

Peter L. Rinaldi
Professor of Chemistry and Director of the Molecular Spectroscopy Laboratory
 

Funding Sources
Description of the Project
Research
Projected Benefits of the Project
Collaborations
Experiences and Outcomes
 

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Description of the Project

There are two aspects to this part of the proposal: frontier research in the development of NMR methods for analysis of polymers and a research service operation based on the use of unique instrumental capabilities present in the Molecular Spectroscopy Laboratory (MSL).

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Research

Much of the research work in our laboratory involves the development and applications of new, multidimensional-triple resonance nuclear magnetic resonance (NMR) techniques for the characterization of synthetic polymers, dendrimers, and supramolecular structure.^1-5 We have developed a suite of experiments which provide complete atomic connectivity information in synthetic macromolecules. Methods for determining interatomic distances in molecules which have well-defined three-dimensional structures are being developed. These NMR methods are parallel to those developed by structural biologists, over the past 10 years, to obtain solution structures of proteins. The detailed molecular structures obtained from these new NMR methods provides information about the initiation and termination processes of polymerization reactions, molecular structure defects, polymer chain branching, polymer chain functionalization, reactivity and molecular configuration. Because these structural details are important in defining the stability and properties of materials, the information from the new NMR methods being developed are finding many applications in basic and applied  materials science research. While the primary objective of this work was to develop methods for studying polymers, researchers across the country have come to us for assistance in studying problems in many areas of chemistry and biochemistry because of the many unique capabilities present in the NMR instruments here at UA.

NMR is the most valuable and generally applicable of all the spectroscopic techniques in chemical sciences. Of all the spectroscopic techniques, it generally provides the most information about molecular structure, properties and motion. Unfortunately, it is also the least sensitive of all the techniques, which is its most significant limitation. In a second research area, we are working in collaboration with major companies to explore the applications of new, high-sensitivity, high temperature superconducting NMR probe technology at ultra high field (600 and now 750 MHz). In the winter of 1996-97 we received the first of these probes, for our 600 MHz instrument.  With this probe, we were able to obtain spectra from sample quantities as small as 1-10 ng.  By the time this proposal is reviewed, we will receive a similar probe for our 750 MHz instrument which will provide additional capabilities and further improvements in sensitivity. This new technology will have a significant impact on basic and applied research in materials science and metabolic studies required for approval of pharmaceuticals, insecticides and herbicides. In materials science specific applications include the ability to obtain solution NMR spectra for sparingly soluble polymers and to detect resonances from chain-end groups of very high molecular weight polymers.

The NMR center at The University of Akron  is uniquely equipped to perform this research; the center has over $5 million of NMR instrumentation and supporting equipment, including an array of workstations which are networked via Fast Ethernet switches. Among the instruments is a 750 MHz NMR, which is one of only 10-15 in the country. It is unique in that it is the only one of its kind in the world which is dedicated to materials science research (other 750-800 MHz instruments are used for protein structure determination and are equipped with accessories for that work). The 750 MHz  instrument at the UA has over $0.5 million worth of special probes and accessories, which have been specifically designed to study synthetic macromolecules, and which are not found on other similar  instruments. The facility was established in 1987 as a regional resource, and has been used by researchers at over 30 academic research groups and 40 industrial research laboratories.

The primary mode of operation involves collection of data from samples which have been sent to us. The data files are then transferred via ftp to remote users. Typical two dimensional (2D) data files are 10-100 Mbytes and three dimensional (3D) data files are 0.5-5 Gbytes.  File transfers are usually very bothersome and often require multiple attempts, which can each last up to several hours (limitations to transport of data are off campus, within our campus, file transfers proceed rapidly). The instruments in the laboratory are capable of producing several 3D files/day and several dozen 2D files/day. In this mode of operation, it is desirable to have the highest bandwidth possible, so that users can transfer files, can process data remotely, examine the data, and advise us to rerun experiments if the information they want is not present. If timely examination of the data isn't possible, additional instrument time must scheduled at a future date to rerun the spectra using different experimental conditions. This process can often take several iterations, necessitates repeated reconfiguration of the instrument, and requires months before the needed information is obtained.

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Projected Benefits of the Project

The preferred mode of operation would be to have the sample submitter involved with the setup of the experiment. This would lead to more useful datasets, more efficient instrument use, and faster solution of research problems. In this mode, the remote users would operate the instrument from their sites, examine the initial data as it comes from the instrument, and provide real-time feedback for optimizing instrument conditions. We have successfully used remote control of the instruments from within our building, which has a high-speed network. Any computer (PC, MAC or Unix workstation) can be adapted for this purpose by the addition of software which costs ca. $200. This mode of operation requires high bandwidth (many graphics files of several hundred kbytes each must be transferred and remotely displayed in real time), low latency and quality of service. Once the instrument conditions have been optimized and the experiment is run; the completed dataset could be transferred via ftp to the remote site where processing and analysis would be performed or processed at UA with remote visualization of the of the resulting 3D graphics file.

The proposed network will also enable us to explore a new class of 4D NMR experiments which are not possible with our existing hardware. The amount of extractable information, and therefore the complexity of the molecules which can be studied, increases with the dimensionality of the experiment. Furthermore, unique information is available from the simultaneous correlation of 4 frequencies in a 4D experiment, which is not available in any combination of 3D experiments.

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Collaborations

Researchers who have received data from our facility or with whom faculty affiliated with our facility plan collaborations in the near future include scientists at the following institutions which have connections to high speed a network: NASA-Lewis, Dupont Central Research, Case Western Reserve University, Kent State University, Ohio University, Miami University (Ohio), Georgia Institute of Technology, Syracuse University, and University of Illinois at Urbana-Champaign.

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Experiences and Outcomes

Joseph Massey, Dr Rinaldi's network manager, tested file transfer rate across the University's backbone.  He used a 1.77 GB data set containing many files and moved it to another location through the backbone in 30 minutes which approximates a network speed of 800 Mb/sec.  On this transfer the network handled up to 16384 packets a sec.  This is a very high transfer rate.

In a separate trial, the University of Kentucky FTPed to us 20 MB to 100 MB files in less than 2 minutes for the largest file this equates to a transfer rate of 100Mb/sec.  In a third test the University of Wisconsin under X Windows was able to run computations and view results in real time using a remote computational server as if it were locally present.

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