PMID- 16284264
OWN - NLM
STAT- MEDLINE
DCOM- 20060517
LR  - 20240314
IS  - 0006-3495 (Print)
IS  - 1542-0086 (Electronic)
IS  - 0006-3495 (Linking)
VI  - 90
IP  - 3
DP  - 2006 Feb 1
TI  - Chemical and structural disorder in eumelanins: a possible explanation for 
      broadband absorbance.
PG  - 743-52
AB  - We report the results of an experimental and theoretical study of the electronic 
      and structural properties of a key eumelanin 
      precursor-5,6,-dihydroxyindole-2-carboxylic acid (DHICA)-and its dimeric forms. 
      We have used optical spectroscopy to follow the oxidative polymerization of DHICA 
      to eumelanin and observe red shifting and broadening of the absorption spectrum 
      as the reaction proceeds. First principles density functional theory calculations 
      indicate that DHICA oligomers (possible reaction products of oxidative 
      polymerization) have the gap between the highest occupied molecular orbital and 
      the lowest unoccupied molecular orbital red-shifted gaps with respect to the 
      monomer. Furthermore, different bonding configurations (leading to oligomers with 
      different structures) produce a range of gaps. These experimental and theoretical 
      results lend support to the chemical disorder model where the broadband monotonic 
      absorption characteristic of all melanins is a consequence of the superposition 
      of a large number of nonhomogeneously broadened Gaussian transitions associated 
      with each of the components of a melanin ensemble. These results suggest that the 
      traditional model of eumelanin as an amorphous organic semiconductor is not 
      required to explain its optical properties and should be thoroughly reexamined. 
      These results have significant implications for our understanding of the physics, 
      chemistry, and biological function of these important biological macromolecules. 
      Indeed, one may speculate that the robust functionality of melanins in vitro is a 
      direct consequence of its heterogeneity, i.e., chemical disorder is a "low cost" 
      natural resource in these systems.
FAU - Tran, M Linh
AU  - Tran ML
AD  - Soft Condensed Matter Physics Group, and Theoretical Condensed Matter Physics 
      Group, School of Physical Sciences, University of Queensland, Brisbane, QLD 4072, 
      Australia.
FAU - Powell, Ben J
AU  - Powell BJ
FAU - Meredith, Paul
AU  - Meredith P
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20051111
PL  - United States
TA  - Biophys J
JT  - Biophysical journal
JID - 0370626
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 0 (pheomelanin)
RN  - 12627-86-0 (eumelanin)
RN  - 4790-08-3 (5,6-dihydroxy-2-indolylcarboxylic acid)
RN  - 63-84-3 (Dihydroxyphenylalanine)
RN  - EC 1.14.18.1 (Monophenol Monooxygenase)
RN  - S88TT14065 (Oxygen)
SB  - IM
MH  - Biophysics/*methods
MH  - Dihydroxyphenylalanine/chemistry
MH  - Dimerization
MH  - Electrons
MH  - Indoles/chemical synthesis/*chemistry
MH  - Kinetics
MH  - Magnetic Resonance Spectroscopy
MH  - Melanins/chemistry
MH  - Models, Chemical
MH  - Models, Molecular
MH  - Monophenol Monooxygenase/chemistry
MH  - Normal Distribution
MH  - Oxidation-Reduction
MH  - Oxygen/chemistry/metabolism
MH  - Spectrometry, X-Ray Emission
MH  - Time Factors
MH  - Ultraviolet Rays
PMC - PMC1367100
EDAT- 2005/11/15 09:00
MHDA- 2006/05/18 09:00
PMCR- 2007/02/01
CRDT- 2005/11/15 09:00
PHST- 2005/11/15 09:00 [pubmed]
PHST- 2006/05/18 09:00 [medline]
PHST- 2005/11/15 09:00 [entrez]
PHST- 2007/02/01 00:00 [pmc-release]
AID - S0006-3495(06)72263-9 [pii]
AID - 69096 [pii]
AID - 10.1529/biophysj.105.069096 [doi]
PST - ppublish
SO  - Biophys J. 2006 Feb 1;90(3):743-52. doi: 10.1529/biophysj.105.069096. Epub 2005 
      Nov 11.