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  • IS-

    Surface Plasmon Enhanced Interracial Electron Transfer and Resonance Raman, Surface-enhanced Resonance Raman Studies of Cytochrome C Mutants

    by

    Zheng, Junwe i

    PHD Thesis submitted to Iowa State University

    Ames Laboratory, U.S. DOE

    Iowa State University

    Ames, Iowa 50011

    Date Transmitted: November 8, 1999

    PREPARED FOR THE U.S. DEPARTMENT OF ENERGY

    UNDER CONTRACT NO. W-7405-Eng-82.

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  • rDISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

    This report has been reproduced directly from the best available copy.

    AVAllABILllY:

    To DOE and DOE contractors:

    To the public:

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    prices available from: (615) 576-8401 FTS: 626-8401

    National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA 22161

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  • DISCLAIMER

    Portions of this document may be illegibie in electronic image products. Images are produced from the best available original document.

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  • ... 111

    TABLE OF CONTENTS

    CHAPTER 1. GENEIL4L INTRODUCTION Dissertation Organization The Mechanisms for Sutiace-enhanced Raman Scattering

    Electromagnetic Enhancement Model Chemical Effect Model New Trends in Application of SERS

    Cytochrome c and its Raman Scattering Spectroscopy Cytochrome c Resonance Raman Surface-enhanced Resonance Raman Scattering

    References

    CHAPTER 2. PHOTOINDUCED ELECTROCHEMICAL REDUCTION OF NITRITE AT ELECTROCHEIVDCALLY ROUGHENED SILVER SURFACE

    Abstract Introduction Experimental Methods Results and Discussion

    Effect of Electrode Material and Surface Treatment Effect of Excitation Wavelength on Photoelectrochemical Response Effect of pH Reduction of Nitrate

    Conclusions Acknowledgement References

    CHAPTER 3. PHOTOELECTROCHEMICAL REDUCTION OF COZMEDIATED WITH METHYLVIOLOGEN AT ROUGHENED SILVER ELECTRODES

    Abstract Introduction Experimental

    Chemicals Apparatus and Methods

    Results Discussion Conclusion Acknowledgement References

    1 2 3 4 6 7 8 8

    17 23 23

    29 29 29 32 34

    34 34 49 51 51 53 53

    56 56 56 58 58 58 60 72 76 76 76

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  • iv

    CHAPTER 4. PHOTOINDUCED ELECTRON TRANSFER AT THE SURFACE OF NANOSIZE SILVER PARTICLES AS MONITORED BY EPR SPECTROSCOPY 79

    Abstract 79

    Introduction 79

    Experimental Methods 80

    Results and Discussion 81

    References 88

    CHAPTER 5. ELECTROCHEMISTRY AND SURFACE-ENHANCED RESONANCE RAMAN SCATTERING SPECTRA OF MICROPEROXIDASE-1 1

    Abstract Introduction Experimental Section

    Materials and Solutions Apparatus and Procedures

    Results and Discussion Electrochemistry of NIP-l 1 RR spectra of NW-l 1 SERRS SpectraofMP-11 Photo-induced Reduction ofMP-11

    Conclusion Acknowledgement References

    CHAPTER 6. RESONANCE RAMAN STUDY OF CYTOCHROME C WATER MUTANTS

    Abstract Introduction Experimental Results and Discussion

    Tyrosine-67 to phenylalanine Asparagine-52 to isoleucine Histidine-26 to valine

    Conclusions Acknowledgement References

    90 90 90 92 92 92 93 93 96 96

    102 105 106 106

    108 108 108 113 114 122 122 124 126 128 128

    CHAPTER 7. CIRCULAR DICHROISM AND RESONANCE RAMAN COMPARA- TIVE STUDIES OF WILD TYPE CYTOCHROME C W F82H MUTANT 131

    Abstract 131

    Introduction 132

    Experimental 133

    Materials and Methods 133

    Spectroscopic Measurements 133

  • v

    Results and Discussion 134

    W/Vis and CD Spectra 134

    RR spectra 142

    Conclusions 152

    Acknowledgement 152

    References 152

    CHAPTER 8. STUDY ON THE STABILITY AND ELECTROCHEMICAL BEHAVIOR OF YEAST ISO-1-CYTOCHROME C BY ELECTROCHEMICAL AND SURFACE- ENHANCED RESONANCE RAMAN SCATTERING TECHNIQUES 157

    Abstract 157

    Introduction 158

    Experimental 160

    Materials 160

    Apparatus and Methods 160

    Results 162

    Discussion 170

    Conclusions 177

    Acknowledgement 178

    References 178

    CHAPTER 9. GENEIL4L CONCLUSIONS 181

    ACKNOWLEDGEMENTS 184

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  • 1

    Surface plasmon enhanced interracial electron transfer and resonance Raman,

    surface-enhanced resonance Raman studies of cytochrome c mutants

    Junwei Zheng

    Major Professor: Edward S. Yeung

    Surface plasmon resonance was utilized to enhance the electron transfer at

    silver/solution interfaces. Photoelectrochemical reductions of nitrite, nitrate, and COZwere

    studied on electrochemically roughened silver electrode surfaces. The dependence of the

    photocument on photon energy, applied potential and concentration of nitrite demonstrates

    that the photoelectrochemical reduction proceeds via photoemission process followed by the

    capture of hydrated electrons. The excitation of plasmon resonances in nanosized metal

    structures resulted in the enhancement of the photoemission process. In the case of

    photoelectrocatalytic reduction of COZ,large photoelectrocatalytic effect for the reduction of

    COZwas observed in the presence of surface adsorbed methylviologe~ which fi.mctionsas a

    mediator for the photoexcited electron transfer from silver metal to C02 in solution.

    Photoinduced reduction of microperoxidase-1 1 adsorbed on roughened silver electrode was

    also observed and attributed to the direct photoejection of free electrons of silver metal.

    Surface plasmon assisted electron transfer at nanostmctured silver particle surfaces was fbrther

    determined by EPR method.

    Resonance Raman studies of cytochrome c and its mutants demonstrate the sensitivity of

    the spectra to mutations that affect the interactions of the heme peripheral substituents with the

    protein matrix. The most dramatic differences in the spectra of the mutant cytochromes, as

    compared with that of wild-type cytochrome c, occurred in the low-wavenumber region. The

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  • 2

    bands that are most strongly affected include bending modes of the thioether linkages and

    propionic acid side-chains. Oxidation state dependent axial ligand switching of heme iron in

    yeast iso-1-cytochrome c mutant F82H was determined by W-visible, circular dichroism and

    resonance Raman spectra. From the analysis of the spectr~ it was concluded that in the

    oxidized F82H axial Iigands to the heme iron are His-18 and Hk-82 whereas in the reduced

    form the sixth ligand switches from His-82 to Met-80. The mutant possesses less distorted

    porphyrin macrocycle and more opened conformation relative to that of wild type protein. The

    comparisons of the sutiace-enhanced resonance Raman scattering spectra and cyclic

    vokammetries of the proteins reveal that F82H mutant has more stable conformation and

    negative redox reaction potential.

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  • 1

    CHAPTER 1

    GENERAL INTRODUCTION

    Surface plasmon of nanostructured metal particles has received increasing attention

    and been extensively studied in recent years. A number of optical phenomen~ including

    Surface-enhanced Raman Scattering (SERS)l-8, surface-enhanced absorption and

    luminescence, second Harmonic generation (SHG)lO,can be strongly enhanced when

    molecules adsorbed on roughened metal surfaces or on surfaces of nanostructured metal

    particles. Those enhancements have been attributed to the excitation of the collective

    electron oscillations or surface plasmon oscillations that engender huge electromagnetic field

    both inside and out side of small metal particles. The fields inside result in strong absorption

    of radiant energy. The fields outside, on other hand, stimulate enhanced optical emissions,

    which are then fiuther enhanced by resonant interaction with particle at the shifted frequency.

    Beyond the surface enhanced optical phenomen~ the enhancement due to surface plasmon

    resonance has also recently been observed in photochemistry 1. One of the specific

    objectives of this dissertation was foutiold on utilization of surface plasmon resonance to

    enhance the electron transfer at silver/solution interfaces. The photoinduced electrochemical

    reductions of nitrite, C02, microperoxidase-11 as a mo

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