PMID- 35175060
OWN - NLM
STAT- MEDLINE
DCOM- 20220422
LR  - 20220422
IS  - 1520-5207 (Electronic)
IS  - 1520-5207 (Linking)
VI  - 126
IP  - 8
DP  - 2022 Mar 3
TI  - Free Energy and Stacking of Eumelanin Nanoaggregates.
PG  - 1805-1818
LID - 10.1021/acs.jpcb.1c07884 [doi]
AB  - Eumelanin, a member of the melanin family, is a black-brown insoluble pigment. It 
      possesses a broad range of properties such as antioxidation, free radical 
      scavenging, photoprotection, and charge carrier transportation. Surprisingly, the 
      exact molecular structure of eumelanin remains undefined. It is, however, 
      generally considered to consist of two main building blocks, 5,6-dihydroxyindole 
      (DHI) and 5,6- dihydroxyindole carboxylic acid (DHICA). We focus on DHI and 
      report, for the first time, a computational investigation of the structural 
      properties of DHI-eumelanin aggregates in aqueous solutions. First, 
      multimicrosecond molecular dynamics (MD) simulations at different concentrations 
      were performed to investigate the aggregation and ordering of tetrameric 
      DHI-eumelanin protomolecules. This was followed by umbrella sampling (US) and 
      density functional theory (DFT) calculations to study the physical mechanisms of 
      stacking. Aggregation occurs through formation of nanoscale stacks and was 
      observed in all systems. Further analyses showed that aggregation and coarsening 
      of the domains is due to a decrease in hydrogen bonds between the eumelanins and 
      water; while domains exist, there is no long-range order. The results show 
      noncovalent stacks with the interlayer distance between eumelanin protomolecules 
      being less than 3.5 A. This is in good agreement with transmission electron 
      microscopy data. Both free energy calculations and DFT revealed strong stacking 
      interactions. The electrostatic potential map provides an explanation and a 
      rationale for the slightly sheared relative orientations and, consequently, for 
      the curved shapes of the nanoscale domains.
FAU - Soltani, Sepideh
AU  - Soltani S
AD  - Department of Physics and Astronomy, The University of Western Ontario, 1151 
      Richmond Street, London, Ontario N6A 3K7, Canada.
AD  - The Centre of Advanced Materials and Biomaterials Research, The University of 
      Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada.
FAU - Sowlati-Hashjin, Shahin
AU  - Sowlati-Hashjin S
AUID- ORCID: 0000-0001-6968-1535
AD  - Institute of Biomedical Engineering, University of Toronto, Toronto, Ontario 
      M5S 3G9, Canada.
FAU - Tetsassi Feugmo, Conrard Giresse
AU  - Tetsassi Feugmo CG
AD  - National Research Council Canada, Energy Mining and Environment, Mississauga, 
      Ontario L5K 1B1, Canada.
AD  - Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, 
      London, Ontario N6A 5B7, Canada.
FAU - Karttunen, Mikko
AU  - Karttunen M
AUID- ORCID: 0000-0002-8626-3033
AD  - The Centre of Advanced Materials and Biomaterials Research, The University of 
      Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada.
AD  - Department of Physics and Astronomy, The University of Western Ontario, 1151 
      Richmond Street, London, Ontario N6A 3K7, Canada.
AD  - Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, 
      London, Ontario N6A 5B7, Canada.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20220217
PL  - United States
TA  - J Phys Chem B
JT  - The journal of physical chemistry. B
JID - 101157530
RN  - 0 (Indoles)
RN  - 0 (Melanins)
RN  - 12627-86-0 (eumelanin)
SB  - IM
MH  - *Indoles/chemistry
MH  - *Melanins/chemistry
MH  - Molecular Structure
MH  - Pigmentation
EDAT- 2022/02/18 06:00
MHDA- 2022/04/23 06:00
CRDT- 2022/02/17 12:18
PHST- 2022/02/18 06:00 [pubmed]
PHST- 2022/04/23 06:00 [medline]
PHST- 2022/02/17 12:18 [entrez]
AID - 10.1021/acs.jpcb.1c07884 [doi]
PST - ppublish
SO  - J Phys Chem B. 2022 Mar 3;126(8):1805-1818. doi: 10.1021/acs.jpcb.1c07884. Epub 
      2022 Feb 17.