TY  - JOUR
A1  - Schmitt, Clemens Nikolaus Zeno
A1  - Winter, Alette
A1  - Bertinetti, Luca
A1  - Masic, Admir
A1  - Strauch, Peter
A1  - Harrington, Matthew J.
T1  - Mechanical homeostasis of a DOPA-enriched biological coating from mussels in response to metal variation
JF  - Interface : journal of the Royal Society
N2  - Protein metal coordination interactions were recently found to function as crucial mechanical cross-links in certain biological materials. Mussels, for example, use Fe ions from the local environment coordinated to DOPA-rich proteins to stiffen the protective cuticle of their anchoring byssal attachment threads. Bioavailability of metal ions in ocean habitats varies significantly owing to natural and anthropogenic inputs on both short and geological spatio-temporal scales leading to large variations in byssal thread metal composition; however, it is not clear how or if this affects thread performance. Here, we demonstrate that in natural environments mussels can opportunistically replace Fe ions in the DOPA coordination complex with V and Al. In vitro removal of the native DOPA metal complexes with ethylenediaminetetraacetic acid and replacement with either Fe or V does not lead to statistically significant changes in cuticle performance, indicating that each metal ion is equally sufficient as a DOPA cross-linking agent, able to account for nearly 85% of the stiffness and hardness of the material. Notably, replacement with Al ions also leads to full recovery of stiffness, but only 82% recovery of hardness. These findings have important implications for the adaptability of this biological material in a dynamically changing and unpredictable habitat.
KW  - mussel byssus
KW  - DOPA
KW  - metal coordination
KW  - coating
Y1  - 2015
U6  - https://doi.org/10.1098/rsif.2015.0466
SN  - 1742-5689
SN  - 1742-5662
VL  - 12
IS  - 110
PB  - Royal Society
CY  - London
ER  - 
TY  - JOUR
A1  - Arhammar, C.
A1  - Pietzsch, Annette
A1  - Bock, Nicolas
A1  - Holmstroem, Erik
A1  - Araujo, C. Moyses
A1  - Grasjo, Johan
A1  - Zhao, Shuxi
A1  - Green, Sara
A1  - Peery, T.
A1  - Hennies, Franz
A1  - Amerioun, Shahrad
A1  - Föhlisch, Alexander
A1  - Schlappa, Justine
A1  - Schmitt, Thorsten
A1  - Strocov, Vladimir N.
A1  - Niklasson, Gunnar A.
A1  - Wallace, Duane C.
A1  - Rubensson, Jan-Erik
A1  - Johansson, Borje
A1  - Ahuja, Rajeev C.
T1  - Unveiling the complex electronic structure of amorphous metal oxides
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Amorphous materials represent a large and important emerging area of material's science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today's integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5-10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.
KW  - stochastic quench
KW  - X-ray absorption spectroscopy
KW  - ab initio
KW  - coating
Y1  - 2011
U6  - https://doi.org/10.1073/pnas.1019698108
SN  - 0027-8424
VL  - 108
IS  - 16
SP  - 6355
EP  - 6360
PB  - National Acad. of Sciences
CY  - Washington
ER  -