Partitioning of bacteriorhodopsin. A purple layer can be seen at the interface between the upper decanol phase and the lower water phase. The water phase is turbid from the addition of DS and DDAB, to help solubilize the bacteriorhodopsin and slightly purple from the protein itself. These proteins have very different sources and functions which could explain the difference in partitioning for each.
Tpol is also water soluble, however it is known to be stabilized by a reduced entropic penalty to folding as opposed to non-covalent interactions, giving it thermostable behavior Interestingly the high hydrophobicity did not result in partitioning into the decanol. It was insoluble in both the water and decanol phases, appearing as crystals. The addition of PTAs allowed it to solubilize in perhaps an emulsion or vesicle phase.
This result is not surprising as this membrane protien is know to be amphiphilic, interacting with the membrane bilayer at both the surface and interior. Decanol was originally chosen as it has been used previously to make cell models in oil, however it is clear that each solvent will have its own partitioning coefficients. Hexane, which is perhaps the best model for the low temperature ethane and methane liquid found on Titan, was tested and was not successful at partitioning any of the amino acids, likely do to its highly non-polar nature.
Most biomolecules are designed to function in aqueous phases, and therefore did not easily enter a decanol phase, even in the presence of phase transfer agents. Even the membrane protein, bacteriorhodopsin, which is not soluble in water, was unable to partition into the decanol layer. Taq DNA polymerase did have some solubility in decanol, and other proteins may as well, but it is unlikely that they would remain folded.
The most successful biomolecule in this study was valinomycin, which did not need phase transfer agents. While valinomycin is a cyclic depsipeptide, not a traditional protein, this partitioning indicates that even polymers that look very similar to our own, could be used to generate life in a non-aqueous solvent. There has been a surge of research focused on biopolymer modification that allows molecules to cross a membrane for pharmaceutical purposes, and these modifications hint to what requirements oil-based life may need.
Modification of charged side chains with nonpolar moieties through esterification has been shown to increase cell permeability While N-acetylated polyproline has been shown to be somewhat soluble in octanol, modification of proline to an indole can also increase hydrophobicity of peptides by further burying the polar backbone and still allows helical conformation 22 , and that structural architectures like collagen can form in octanol with similar modification 23 demonstrating the ability of peptide derivatives to form both secondary and quaternary structures in nonpolar solvents.
These findings suggest that biopolymer derivatives would likely be more successful than their water-evolved counterparts. The amino acids tested relied on phase transfer agents to partition into the decanol phase, and even then, only a small portion transferred well into decanol. Phenylalanine was chosen as it has a very hydrophobic side chain, with limited water solubility.
We recognize that it is not generally thought that phenylalanine was part of the reduced amino acid alphabet on early Earth for the origin of life. However, in environments as are expected on Titan, molecules like phenyl groups are much more likely and could contribute to functional biopolymers. However, based on these findings, it is likely that a less charged monomeric form would be necessary as a precursor for nonpolar biopolymers.
Finally, we conclude that while extant biomolecules in the presence of phase transfer agents are not ideal for decanol-based life, the results shown here indicate that solubility in decanol even when water is present can be achieved, and future work should focus on the mechanisms that allow folding and function within non-aqueous phases to better understand changes in non-covalent interactions when water is not present.
Glycylglycine, decanol, and valinomycin were obtained from Acros Organics. Phenylalanine, glutamic acid, bovine serum albumin, and bacteriorhodopsin came from Sigma. These samples were prepared in triplicate. Both decanol and aqueous phase were analyzed for biomolecules. Phenylalanine and proteins were analyzed using UV-vis Hewlett-Packard Council, N. Why Water? Toward More Exotic Habitats. Lee, C. NaCl-saturated brines are thermodynamically moderate, rather than extreme, microbial habitats.
FEMS Microbiol. Cockell, C. Life on Venus. Brown, R. Nature , Ballesteros, F. Mclendon, C. Solubility of Polyethers in Hydrocarbons at Low Temperatures. Astrobiology 15 , — Hanczyc, M. Life 4 Langmuir 30 , — Article Google Scholar. The solubilities of l -cysteine and l -arginine are shown in Figure 7. Also, both l -cysteine and l -arginine have similar solubility ranges, but the solubility of l -arginine decreases faster than that of l -cysteine as the ethanol mole fraction increases.
The solubility of l -cysteine in water that was reported by El-Dossoki and El-Damarany is higher than the solubility measured for this work. El-Dossoki and El-Damarany do not report that their measurements were taken in a sealed, oxygen-poor environment. This could account for elevated experimentally measured solubilty due to the formation of the dimer cystine.
The measurements of Zhang et al. The influence of ethanol on the solubility of amino acids is not the same for all amino acids. Most amino acids have a lower solubility when their solvent is at a higher ethanol mole fraction.
All amino acids have a loss in solubility above a mole fraction of 0. The change in solubility is not the same for all amino acids in the range of 0—0. This difference between the amino acids is most pronounced at ethanol mole fractions around 0. The effect of ethanol on the solubility of amino acids can be characterized by the groups found in their side chains.
Five amino acids have a ring in the side chain. These amino acids are l -tryptophan, l -tyrosine, l -proline, l -phenylalanine, and l -histidine.
These rings include either phenyl, pyrrolidine, or imidazole. The amino acids with rings in the side chains had the least decrease in solubility as ethanol is added.
The average decrease in solubility of these amino acids at an ethanol fraction of 0. In the case of l -tryptophan, the solubility was even increased by We hypothesize that the rings of these amino acids are ethanolphilic, while the amino and carboxylic groups on these amino acids are ethanolphobic.
Moderate ethanol fractions between 0. The water and ethanol molecules arrange themselves at the respective groups of the molecule, creating a lattice around the amino acids. Higher ethanol mole fractions lower the solubility of these amino acids, because the ethanol molecules surround the amino acid molecule and disrupt the water molecules surrounding the amino and carboxylic groups on the amino acid molecule.
The aliphatic amino acids, l -phenylalanine, l -isoleucine, l -leucine, l -alanine, l -methionine, and l -valine, show initially a low to medium decrease in solubility at an ethanol mole fraction of approximately 0. This decrease could be possibly mitigated by the phenyl ring.
The hydroxyl containing amino acids, l -tyrosine, l -serine, and l -threonine, show a medium decrease in solubility. Here, as in the case of l -phenylalanine, the decrease in solubility is mitigated by the phenyl ring.
A high decrease in solubility is seen in the charged amino acids l -glutamic acid, l -aspartic acid, and l -lysine. The average decrease at an ethanol mole fraction of 0. It has the highest decrease in solubility at ethanol mole fraction of 0. Glycine, containing no side chain, had the largest decrease in solubility.
Therefore, all amino acids that have a possibility to convert to other amino acids in solution should be analyzed by a technique that takes this into account. The UPLC technique used in this work shows reliable results. At low concentrations e. However, the UPLC method used in this work was reliable at low concentrations.
The data produced by the UPLC were also within the variation of the data published by Ferreira, Ferreira used the ninhydrin method of analysis. Most data points of several amino acids by Nozaki et al.
A possible explanation for these results includes, but is not limited to, the samples being measured when the solutions were oversaturated or when dissolved from a crystal of another shape e.
Furthermore, this work gives the first data for the solubility of l -asparagine, l -glutamine, l -histidine and l -leucine in pure ethanol. Lastly, the side chain of an amino acid has an effect on the solubility of that amino acid when ethanol is added.
This is shown at ethanol mole fractions around 0. Side chains containing rings show the least decrease in solubility when water is replaced by a water—ethanol mixture due to the ethanolphilic properties of these rings. This is followed in descending order by the aliphatic amino acids, hydroxyl containing amino acids, amide containing amino acids, charged amino acids, sulfur containing amino acids, and the amino acid with no side chain.
Amino acids with side chains of two characteristics, such as l -tyrosine, which is both phenylic and containing a hydroxyl group, show a decrease in solubility in between both of their groups. Supporting Information. Author Information. Nathan A. Johan P. Marieke E. The authors declare no competing financial interest. Availability of protein-derived amino acids as feedstock for the production of bio-based chemicals.
Biomass Bioenergy , 44 , — , DOI: Elsevier Ltd. This review describes different potential sources for amino acids that could be used for the prodn. The investigated sources are maize and wheat DDGS, sugarcane vinasse and its leaves, sugar beet vinasse and its leaves, cassava leaves, press cakes of rapeseed, sunflower, soybean, palm oil and Jatropha, animal slaughter waste, microalgae, macroalgae, grass and alfalfa.
It can be concluded that there are enough sources available to produce bio-based chems. Bulk chems. However, it is still necessary to find cost-effective methods for the isolation of amino acids from the discussed sources. Google Scholar There is no corresponding record for this reference. Environmental comparison of biobased chemicals from glutamic acid with their petrochemical equivalents. American Chemical Society. Glutamic acid is an important biofuels prodn.
It is an interesting starting material for synthesis of bio-based chems. This work compared the environmental impact of 4 bio-based chems. A consequential life cycle anal. Removed glutamic acid was substituted with cane molasses and ureum. A comparison among the 4 bio-based and petrochem. For the latter 2, an optimized computed scenario showed the process for SCN can be improved to a level at which it can compete with the petrochem.
For bio-based ACN, large improvements are required to make it competitive with its petrochem. Results of this life cycle anal. Currently, most methods to produce bio-based products are bio-technol. Solubility of four amino acids in water and of four pairs of amino acids in their water solutions. Data , 37 , — , DOI: The soly.
The eutectic compns. Solubility of -amino acids in water under high pressure: glycine, -alanine, -valine, -leucine, and - isoleucine. Fluid Phase Equilib. Elsevier Science B. The std. A variety of soly. The l-valine and l-isoleucine have a soly. Pressure coeff. In this work thermodn. Osmotic coeffs. Amino-acid soly. Considered aq. The data show that the salt influence is more pronounced on osmotic coeffs.
The electrolyte Perturbed-Chain Statistical Assocn. Without fitting any addnl. Data , 60 , — , DOI: The molal solubilities, d.
From the values of the measured refractive indexes, molal solubilities, and the densities, the excess refractive indexes, the molar refractions, the polarizabilities, and the apparent molar volumes of the systems under study were calcd. The solvation of the amino acids under study was discussed in terms of their molal solubilities, apparent molar volume, and refractive index data.
The phase diagrams of the studied tricomponent systems water-salt-amino acid were also detd. The effect of the electrolytic solns. A salting-in effect of the electrolytic solns. Solution Chem. Data , 57 , — , DOI: Generally the soly.
The two forms were found to be enantiotropically related, and the transition temp. Data , 51 , — , DOI: The solubilities at At high and low pH, the solubilities increase remarkably. The solubilities generally decrease with an increase of the concns. As the NaCl concn. Solubility of alpha-form and beta-form of L-glutamic acid in different aqueous solvent mixtures. Elsevier B.
Based on the soly. Solubility of L-phenylalanine in water and different binary mixtures from The results obtained from these measurements were correlated with the temp.
Note: For complete accuracy, one of the 20 biologically important amino acids proline has a slightly different structure. The "R" group is bent into a circle which attaches itself to the nitrogen again in place of one of the hydrogens.
This complication doesn't actually make much difference to the chemistry of the compound - the nitrogen still behaves in the same way as it does in the other amino acids. This isn't something you need to worry about for chemistry purposes at this introductory level. The amino acids are crystalline solids with surprisingly high melting points. It is difficult to pin the melting points down exactly because the amino acids tend to decompose before they melt.
If you look again at the general structure of an amino acid, you will see that it has both a basic amine group and an acidic carboxylic acid group. There is an internal transfer of a hydrogen ion from the -COOH group to the -NH 2 group to leave an ion with both a negative charge and a positive charge.
A zwitterion is a compound with no overall electrical charge, but which contains separate parts which are positively and negatively charged. This is the form that amino acids exist in even in the solid state. Instead of the weaker hydrogen bonds and other intermolecular forces that you might have expected, you actually have much stronger ionic attractions between one ion and its neighbours. These ionic attractions take more energy to break and so the amino acids have high melting points for the size of the molecules.
Amino acids are generally soluble in water and insoluble in non-polar organic solvents such as hydrocarbons. This again reflects the presence of the zwitterions. In water, the ionic attractions between the ions in the solid amino acid are replaced by strong attractions between polar water molecules and the zwitterions.
This is much the same as any other ionic substance dissolving in water. Jump to main content. Jump to site search. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page. Issue 19, From the journal: Chemical Communications. You have access to this article. Please wait while we load your content Something went wrong. Try again? Cited by.
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