Mesoscale Chemistry A Workshop Summary (2015) / Chapter Skim
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5 Biomineralization and Geochemical Processes
5 Biomineralization and Geochemical Processes
Pages 35-50
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From page 35... ...
A comprehensive model that quantitatively describes the diverse pathways of mineralization is lacking, and one essential challenge for developing that model is to describe the ensemble behavior of coupled solvent–solid systems. Models for crystal growth that work well for describing the growth of bulk soluble crystals at low supersaturation do not work as well when applied to crystals that grow via particle-based processes.
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From page 36... ...
These images reveal that freshly deposited material at the outer edge of Pupa Gilbert started her presentation by showing the growing spicule comprises a mixture of a micrograph of single crystals of calcite that form amorphous and hydrous amorphous calcium the spines of sea urchins. These crystals have carbonate, while the center is mostly crystalline rounded structures that defy the usual understanding calcite.
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From page 37... ...
Duri ing epitaxial growth, the crystals are e e a almost alway connected to one anot ys ther, and the e NUCCLEATION E EVENTS, MIN NERAL ASSSEMBLY, o ones that are not oriente correctly to the other e ed r AND CRYSTAL M D MODIFICATTIONS PERF FORMED crystals appea to stop growing and die out, while c ar d e BY D DISORDERE PROTEIN ED NS o oriented cryst tals grow fas ster and fill space faster.. " "This is a perfectly ab biotic mecha anism," saidd I biological systems, cells are the arc In chitects of G Gilbert.
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From page 38... ...
p ole . A far as wha these prote phases, as he called As at ein s E Each table commprises a pol lysaccharide layer of beta - the aaggregates, d in the nucleation proce Evans do ess, c chitin onto which is dep w posited a silk protein gel k l said that a nonc classic nuclea ation model p postulates m matrix.
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From page 39... ...
In on set of ne t that eventua ally produce branching mineralized d expeeriments, the paired A ey AP7 with PF FMG-1, a s structures (Figgure 5-4) , whhereas when AP7 is absent, A , prote found in J ein Japanese oyst pearl nacr and that ter re a amorphous calcium carbo onate forms rapidly in a by ittself forms clu usters of crys stals that resemmble pine c chaotic mann (Chang et al.
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From page 40... ...
M Measurements of amorp phous calcium carbonate m e poly ymer-induced liquid-phase precursor, s e something s solubility as a function of time showed that n t that was observ ved a decad ago with polymer de n nucleation events are sligh destabiliz when the htly zed e syste ems that for lipid phases with am rm morphous A AP7:PFMG-1 ratio was 10:1, a little more 1 s e precuursors. He noted th hat this i interesting destabilized at a 1:10 ratio, and strongly destabilized d a y d phennomenon need further stu ds udy.
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From page 41... ...
on ," nucl eation barrier is eliminate by the aggregates of r ed Nucleation, he said, occurs throu ugh unstable e these clusters, sa De Yoreo However, there are e aid o. d density fluctuuations that overcome a free energy y also data regard ding the di istribution of smaller f barrier, a theo put forth by Josiah Williard Gibbs b ory W s clustters of calc cium carbona that are seen in ate in two paper published in 1876 and 1878 as a rs d cryooelectron mic crographs tha he said a at argue for m means of exp plaining how water dropl w lets form butt
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From page 42... ...
which occurs on the surface of the particle, The challenge, then, is to create theoretic transforms amorphous calcium carbonate into frameworks and computational tools to describe crystalline aragonite. What these experiments ensemble phenomena with molecular fidelity and in showed was that all of the phases of the calcium situ experimental tools that can visualize molecular carbonate system are stable relative to the solution events.
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From page 43... ...
the mes ion electtrostatic force dominate in this case. es n It turns ou said De Yoreo, that ad ut, Y dding organicc H concluded his presentation with hi view of He d is p polymers to a supersatur rated solution of calcium n m some of the ke mesoscal science c e ey le challenges c carbonate can redirect nucleation pa n n athways.
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From page 44... ...
theoretical frameworks and computational tools that Another important paleo proxy, one used widely can describe the ensemble phenomenon in these to reconstruct sea surface temperatures, also uses systems while keeping molecular fidelity where it is foraminifera and it is based on the empirical needed, and experimental tools that can visualize observation that its skeleton is not pure calcium molecular-scale events in real time. carbonate but includes a number of impurities, particularly magnesium.
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From page 45... ...
His group is now collectin data for a H n ng comp positional vvariability thhat is structu ured and n number of different ions using nano-TOF-SIMS d s S becaause they lay down a ver clear orga y ry anic layer, t to construct detailed compositiona maps of c al f know as the p wn primary orga anic membra ane, upon f foraminifera grown under different co r onditions. He e whic they gro ch ow their ske eletons (Fig gure 5-8)
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From page 46... ...
impo ortant for the environment make observ t, vations of " "There is a co ompositional signature, and the location d n the nnatural world and see if the two set of data d, f ts c tell us ab can bout mechan nism," he saidd,adding thatt correelate with eac other. "But what we act ch t tually find t these data are consistent with the sign e nature of the e in th natural e he environment is that nan noparticles large sodium signature det tected with ot ther methods,, aren 't really isola ated," said MMadden, sugge esting that s such as ti ime-of-flight secondary ion mass s it m might be poss sible to use observations from the spectrometry (Figure 5-9)
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From page 47... ...
. soscale partic e experiments, manganese oxidation under abiotic u c Usin an instrum ng ment that can simulate th type of n he c conditions pr roduced disor rdered, poorl crystalline ly e proccesses occurr ring in fault zones, Mad t dden and m manganese oxide as the end produc but when o ct, n Univversity of Ok klahoma colle eague and coollaborator c conducted wi cell-free extracts prep ith pared from a Ze'eev Reches found th he same type of b bacterium tha oxidized manganese, th result was at m he s nanooparticulate m materials in the gouged rocks.
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From page 48... ...
S Session mod derator Patric Thiel st cia tarted the Madden, working with the principa investigator w h al r discuussion by a asking if th panelists saw any he f this project, Megan El for lwood Madde measured en, d connnections betwween their wwork and the work on t the dissolutio kinetics of jarosite under various on o u s catallysis that was discussed i the worksh s in hop's first c conditions an saw wha thousands of previous nd at s pane presentation Gilbert res el n. sponded first by noting geochemical experiments have seen -- s g e solute releasee that there is one b difference between cat big e talysis and into an aque eous solution rises quick and then n kly n biommineralization processes: catalysis is about n p plateaus.
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From page 49... ...
The unanimous answer from the of magnitude larger than the entire organism." In panelists was no, though Gagnon noted that it is short, she said, there is no water involved in starting to be possible to modify existing processes biomineralization. De Yoreo tempered Gilbert's to change morphology or composition, but he comments by saying that the biomineral world is characterized that as a baby step toward total control vast.
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From page 50... ...
It may be The aragonite crystals in nacre that Gilbert talked that magnesium is influencing the behavior of about are an exception because aragonite is not the proteins that are involved in regulating aragonite stable state of calcium carbonate at room production.
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