Three Reasons Why Aspartic Acid and Glutamic Acid Sequences Have a Surprisingly Different Influence on Mineralization

Abstract

Understanding the role of polymers rich in aspartic acid (Asp) and glutamic acid (Glu) is the key to gaining precise control over mineralization processes. Despite their chemical similarity, experiments revealed a surprisingly different influence of Asp and Glu sequences. We conducted molecular dynamics simulations of Asp and Glu peptides in the presence of calcium and chloride ions to elucidate the underlying phenomena. In line with experimental differences, in our simulations, we indeed find strong differences in the way the peptides interact with ions in solution. The investigated Asp pentapeptide tends to pull a lot of ions into its vicinity, and many structures with clusters of calcium and chloride ions on the surface of the peptide can be observed. Under the same conditions, comparatively fewer ions can be found in proximity of the investigated Glu pentapeptide, and the structures are characterized by single calcium ions bound to multiple carboxylate groups. Based on our simulation data, we identified three reasons contributing to these differences, leading to a new level of understanding additive−ion interactions.

Stable Binding Conformations of Polymaleic and Polyacrylic Acids at a Calcite Surface in the Presence of Countercations: A Metadynamics Study

“…The present results suggest that aqueous cations strongly affect the binding conformations of ionic polymer additives at the calcite surface, as reported for the solution conformations of ionic polymers in water. ,,,− It is difficult to estimate how many ions exist near additive molecules bound to the surface of calcite in real systems. The countercation density in the aqueous phase of the present simulation system was considerably higher than the equilibrium concentration of ions in real bulk water.…”

“…In summary, the countercations affected each stable binding conformation of PMA5 quite significantly. Analogously, the effect of interactions with aqueous ions on the conformation of ionic polymers has been discussed in previous studies. ,,,− …”

“…Thus, a total of six additive and countercation combinations were examined, which are denoted PMA5–1, PMA5–2, PAA5–1, PAA5–2, PAA10–1, and PAA10–2 (Table ). Terrestrial water contains both Ca 2+ and Na + ions, and calcite is often formed in the laboratory from aqueous CaCO 3 solutions containing Na + ions. ,, In MD simulations, Na + ions have frequently been used as the countercations of negatively charged additives dissolved in water near the calcite surface. , It is expected that the binding conformations of the additives may be affected by the countercations, as is the case for the conformations of polymers in water. ,,,− …”

The influence of l-aspartic acid on calcium carbonate nucleation and growth revealed by in situ liquid phase TEM

“…Previous papers already described the influence of poly- l -aspartic acid in higher concentrations by clusters and PILP formation. 1,18,62 Here we were able to demonstrate that this amino acid in its single form, without peptide bonds, and in concentration equal to the reagents is able to directly influence the crystallization of calcium carbonate.…”

Biodegradability as an Off-Ramp for the Circular Economy: Investigations into Biodegradable Polymers for Home and Personal Care

“…Classes of biodegradable polymers historically and currently evaluated as potential biodegradable dispersants include poly(amino acids) with free carboxylic groups such as sodium polyaspartate or polyglutamic acid 21 as well as low molecular weight modified polysaccharides such as carboxymethyl inulin 22 (Figure 2). Both polymer types support claims of biodegradability as well as functionality similar to poly(acrylic acid).…”