The spectroscopic properties of melanin

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Transcript of The spectroscopic properties of melanin

  • The spectroscopic properties ofmelanin

    A thesis submitted for the degree of Doctor of Philosophyto the University of Queensland

    November 2007

    Jennifer RieszPhysical Sciences

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    c Jennifer Riesz, 2007.

    Typeset in LATEX2.

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    Statement of my contribution to jointly-published workand contributions by others

    Chapter 2: The broadband absorption spectrum of melanin

    The broad ideas presented in this chapter were also summarised in the publication P.Meredith, B. J. Powell, J. J. Riesz, S. Nighswander-Rempel, M. R. Pederson and E. Moore.Towards structure-property-function relationships for eumelanin, Soft Matter 2, 37 (2006).The discussion in that publication is largely by Paul Meredith (with contributions from BenPowell), but the discussion presented in this thesis is my own and figures are attributed asreferenced.

    Chapter 3: The structure of melanin

    The work presented in this chapter came out of many in-depth discussions with my super-visors Paul Meredith, Ross McKenzie and Ben Powell. I performed the majority of theliterature searching and research under their guidance and wrote the review presented here.I was not involved in the TEM work that is presented in this chapter, and include it merelyto show a complete representation of the advances in this area.

    Chapter 4: Quantitative scattering of eumelanin solutions

    This chapter is an almost complete representation of the publication J. Riesz, J. Gilmoreand P. Meredith. Quantitative scattering of melanin solutions. Biophysical Journal 90(11),1 (2006). The idea for this work was my own, and the theory was developed in closecollaboration with Joel Gilmore. I designed the experimental setup and performed all mea-surements, and did all of the data manipulation to produce the figures included. PaulMeredith was involved throughout with discussion of the data and review of written work.I wrote the published paper, and the discussion included in this thesis is very similar (withsome exceptions where material was repeated earlier in the introductory sections).

    Chapter 5: The dipole strength of eumelanin

    This chapter is an almost complete representation of the publication J. Riesz, J. Gilmore,R. H. McKenzie, B. J. Powell, M. R. Pederson and P. Meredith. The transition dipolestrength of melanin. Submitted to Physical Review E (2007). This work was inspired bydiscussion between myself, Ross McKenzie, Ben Powell and Paul Meredith. The theoryand modifications to NRLMOL to perform dipole strength calculations were developed inclose collaboration with Mark Pederson during my two week visit to his laboratory in 2005.I performed all data manipulations and analysis, with input of thoughts and ideas fromRoss McKenzie, Ben Powell, Paul Meredith and Joel Gilmore during our many meetingsto discuss this work. I wrote the final publication, and Paul Meredith made modificationsto the introductory section. Joel Gilmore contributed a paragraph on solvent effects. Thediscussion included in this thesis is very similar to the published paper (with some exceptionswhere material was repeated earlier in the introductory sections).

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    Chapter 6: The challenge of spectroscopy with melanin

    This chapter follows closely work that has been published as P. Meredith and J. Riesz.Radiative relaxation quantum yields for synthetic eumelanin. Photochemistry and Photobi-ology 79(2), 211 (2004). The idea for this work was Paul Merediths, and I performed allmeasurements and data manipulation. The correction procedure was developed in close col-laboration between myself and Joel Gilmore. The publication was written by Paul Meredithwith figures produced by myself; however the discussion presented in this thesis is my own.

    Chapter 7: The radiative quantum yield map

    This chapter follows closely work that has been published as S. Nightswander-Rempel,J. Riesz, J. Gilmore and P. Meredith A quantum yield map for synthetic eumelanin. TheJournal of Chemical Physics 123, 194901 (2005). This work was inspired by discussionsbetween myself and Joel Gilmore, in which we jointly developed the theory reported. I devel-oped the experimental method (with some assistance from Joel Gilmore for data retrieval)and took the initial measurements. The data was discussed at meetings attended by PaulMeredith, Joel Gilmore and Stephen Nighswander-Rempel, all of whom contributed theirideas and thoughts. Several later repetitions of these measurements were taken by StephenNighswander-Rempel, and he performed subsequent data processing according to the theorydeveloped by Joel and myself to produce figures 7.2, 7.3, 7.7 and 7.6. I wrote an early draftof the publication with a detailed description of the theory and some introductory materialand discussion of results; this draft was later refined and added to by Stephen Nighswander-Rempel. The discussion in the published paper is largely Stephens, although the discussionincluded in this thesis is entirely my own.

    Chapter 8: Radiative relaxation in synthetic pheomelanin

    This chapter is an almost complete representation of the publication J. Riesz, T. Sarna andP. Meredith. Radiative relaxation in synthetic pheomelanin. Journal of Physical ChemistryB. 110(28), 13985 (2005). This work was inspired by Tadeusz Sarnas offer of a sampleof pheomelanin for us to perform some measurements on. I performed all measurementsand data manipulation, and discussed the results with Paul Meredith. I wrote the finalpublication with assistance and review from Paul Meredith (and contributions from TadeuszSarna), and the discussion included in this thesis is very similar (with some exceptions wherematerial was repeated earlier in the introductory sections).

    Chapter 9: Quantitative spectroscopy of DHICA, a key eumelaninmonomer

    Indu Mahadevan synthesised and characterised the DHICA samples which were used forspectroscopic analysis, and wrote the paragraphs included here describing the process. Ithought of and designed the spectroscopic work as a summer project for an undergraduatestudent (Aaron Coutts). Coutts was supervised by Paul Meredith on a weekly basis, andI provided daily (constant) mentorship and training. The experimental measurements were

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    taken by Coutts. Coutts performed some of the data manipulation and analysis under myguidance, and I did the rest to create the figures included in this chapter. The analysis ofthese figures was discussed at meetings of myself with Paul Meredith, Ross McKenzie, BenPowell and Joel Gilmore. We later enlisted the assistance of Seth Olsen who performed aseries of sophisticated calculations to develop the theory summarised briefly in this chapter,and published as S. Olsen, J. Riesz, I. Mahadevan, A. Coutts, J. P. Bothma, B. J. Powell, R.H. McKenzie, S. C. Smith and P. Meredith. Convergent proton-transfer photocycles violatemirror-image symmetry in a key melanin monomer. Journal of the American ChemicalSociety (2007). This publication included several of the figures I created which are includedin this chapter.

    Chapter 10: Spectroscopic observation of eumelanin formation

    I thought of and designed this work as a summer project for an undergraduate student(Aaron Coutts). Coutts was supervised by Paul Meredith on a weekly basis, and I provideddaily (constant) mentorship and training. Approximately three quarters of the experimentalmeasurements were taken by Coutts (with the rest taken by myself after his vacation schol-arship ran out). Coutts performed some of the data manipulation and analysis, and I didthe rest to create the figures included in this chapter.

    Chapter 11: Inelastic neutron scattering spectroscopy

    Paul Meredith thought of this work and obtained funding for us both to travel to the ISISfacility to perform these measurements. I prepared all the samples and performed all theINS measurements under the close supervision and expert guidance of John Tomkinson. Iperformed the inital literature review and analysis of the INS results for indole, which werelater completed in a much more sophisiticated manner by John Tomkinson, published asJ. Tomkinson, S. Parker, J. Riesz and P. Meredith. The vibrational spectrum of indole: aninelastic neutron scattering study. J. Biomolecular Structure and Dynamics (2006). Thework included in this thesis is a summary of that publication in my own words. I analysedthe results for the other molecules listed, with a large amount of assistance and trainingfrom John Tomkinson via email. These results will soon be submitted for publication as J.Riesz, J. Tomkinson, I. Mahadevan, and P. Meredith. Inelastic neutron scattering of indole-2-carboxylic acid and DHICA (dihydroxyindole-2-carboxylic acid), a key melanin monomer(2007). This has been largely written by myself (with paragraphs contributed by JohnTomkinson and Ben Powell on the computational and experimental methods). The workincluded here follows this publication very closely.

    Statement of originality

    Except where acknowledged in the Statement of Contribution to Jointly-published Work andStatement of Contribution by Others, the material presented in this thesis is, to the bestof my knowledge, original and has not been submitted in whole or part for a degree in anyuniversity.

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    Jennifer RieszAuthor

    Assoc. Prof. Paul MeredithPrincipal Advisor

  • Acknowledgements

    Huge thanks must go to Joel Gilmore for all of his intellectual contributions to the workincluded here, and his constant willingness to help with any problem, no matter how bigor how small. I believe that collaboration with Joel produced the best work included inthis thesis. Also, I owe a massive thank-you to Paul Meredith for all his leadership andsupport over the years; he has been an excellent PhD advisor, and I would certainly recom-mend him to my friends