TY  - JOUR
A1  - Konrad-Schmolke, Matthias
A1  - Babist, Jochen
A1  - Handy, Mark R.
A1  - O'brien, Patrick J.
T1  - The physico-chemical properties of a subducted slab from garnet zonation patterns (Sesia Zone, Western Alps)
JF  - Journal of petrology
N2  - Garnets in continentally derived high-pressure (HP) rocks of the Sesia Zone (Western Alps) exhibit three different chemical zonation patterns, depending on sample locality. Comparison of observed garnet zonation patterns with thermodynamically modelled patterns shows that the different patterns are caused by differences in the water content of the subducted protoliths during prograde metamorphism. Zonation patterns of garnets in water-saturated host rocks show typical prograde chemical zonations with steadily increasing pyrope content and increasing XMg, together with bell-shaped spessartine patterns. In contrast, garnets in water-undersaturated rocks have more complex zonation patterns with a characteristic decrease in pyrope and XMg between core and inner rim. In some cases, garnets show an abrupt compositional change in core-to-rim profiles, possibly due to water-undersaturation prior to HP metamorphism. Garnets from both water-saturated and water-undersaturated rocks show signs of intervening growth interruptions and core resorption. This growth interruption results from bulk-rock depletion caused by fractional garnet crystallization. The water content during burial influences significantly the physical properties of the subducted rocks. Due to enhanced garnet crystallization, water-undersaturated rocks, i.e. those lacking a free fluid phase, become denser than their water-saturated equivalents, facilitating the subduction of continental material. Although water-bearing phases such as phengite and epidote are stable up to eclogite-facies conditions in these rocks, dehydration reactions during subduction are lacking in water-undersaturated rocks up to the transition to the eclogite facies, due to the thermodynamic stability of such hydrous phases at high P-T conditions. Our calculations show that garnet zonation patterns strongly depend on the mineral parageneses stable during garnet growth and that certain co-genetic mineral assemblages cause distinct garnet zonation patterns. This observation enables interpretation of complex garnet growth zonation patterns in terms of garnet-forming reactions and water content during HP metamorphism, as well determination of detailed P-T paths.
KW  - dehydration
KW  - high-pressure metamorphism
KW  - Sesia Zone
KW  - subduction
KW  - thermodynamic modelling
Y1  - 2006
U6  - https://doi.org/10.1093/petrology/egl039
SN  - 0022-3530
VL  - 47
IS  - 11
SP  - 2123
EP  - 2148
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Knox-Brown, Patrick
A1  - Rindfleisch, Tobias
A1  - Günther, Anne
A1  - Balow, Kim
A1  - Bremer, Anne
A1  - Walther, Dirk
A1  - Miettinen, Markus S.
A1  - Hincha, Dirk K.
A1  - Thalhammer, Anja
T1  - Similar Yet Different
BT  - Structural and Functional Diversity among Arabidopsis thaliana LEA_4 Proteins
JF  - International Journal of Molecular Sciences
N2  - The importance of intrinsically disordered late embryogenesis abundant (LEA) proteins in the tolerance to abiotic stresses involving cellular dehydration is undisputed. While structural transitions of LEA proteins in response to changes in water availability are commonly observed and several molecular functions have been suggested, a systematic, comprehensive and comparative study of possible underlying sequence-structure-function relationships is still lacking. We performed molecular dynamics (MD) simulations as well as spectroscopic and light scattering experiments to characterize six members of two distinct, lowly homologous clades of LEA_4 family proteins from Arabidopsis thaliana. We compared structural and functional characteristics to elucidate to what degree structure and function are encoded in LEA protein sequences and complemented these findings with physicochemical properties identified in a systematic bioinformatics study of the entire Arabidopsis thaliana LEA_4 family. Our results demonstrate that although the six experimentally characterized LEA_4 proteins have similar structural and functional characteristics, differences concerning their folding propensity and membrane stabilization capacity during a freeze/thaw cycle are obvious. These differences cannot be easily attributed to sequence conservation, simple physicochemical characteristics or the abundance of sequence motifs. Moreover, the folding propensity does not appear to be correlated with membrane stabilization capacity. Therefore, the refinement of LEA_4 structural and functional properties is likely encoded in specific patterns of their physicochemical characteristics.
KW  - IDP
KW  - LEA protein
KW  - abiotic stress
KW  - dehydration
KW  - conformational rearrangement
KW  - membrane stabilization
KW  - sequence-structure-function relationship
Y1  - 2020
U6  - https://doi.org/10.3390/ijms21082794
SN  - 1422-0067
VL  - 21
IS  - 8
PB  - Molecular Diversity Preservation International
CY  - Basel
ER  -