Enantioselective Separation of Racemic Tryptophan with Sonochemically Prepared Egg Albumin Microspheres

Effects of sound energy on proteins and their complexes

Mechanical energy in the form of ultrasound and protein complexes intuitively have been considered as two distinct unrelated topics. However, in the past few years, increasingly more attention has been paid to the ability of ultrasound to induce chemical modifications on protein molecules that further change protein-protein interaction and protein self-assembling behavior. Despite efforts to decipher the exact structure and the behavior-modifying effects of ultrasound on proteins, our current understanding of these aspects remains limited. The limitation arises from the complexity of both phenomena. Ultrasound produces multiple chemical, mechanical, and thermal effects in aqueous media. Proteins are dynamic molecules with diverse complexation mechanisms. This review provides an exhaustive analysis of the progress made in better understanding the role of ultrasound in protein complexation. It describes in detail how ultrasound affects an aqueous environment and the impact of each effect separately and when combined with the protein structure and fold, the protein-protein interaction, and finally the protein self-assembly. It specifically focuses on modifying role of ultrasound in amyloid self-assembly, where the latter is associated with multiple neurodegenerative disorders.

Luminescent and morphological behavior of the aromatic dipeptide pair having singular structural variability

In the present manuscript, the luminescence and the self-assembly behavior of the two aromatic dipeptides having singular structure variable are investigated. The terminally protected dipeptides tryptophan-tyrosine (WY^p ) and tryptophan-phenylalanine (WF^p ) were synthesized using standard solution phase procedure. Significant solvatochromic effect was observed for both the dipeptidyl entities; while the influence was more pronounced in case of the WY^p entity when compared to WF^p . Interesting morphological variation was observed for WF^p and WY^p , wherein discrete and interconnected nanospheres were observed for the respective dipeptides. The results obtained signifies the influence of the singular structural variation on modulating the overall functional behavior of the short peptides motifs.

Unlocking the potential of Escherichia coli modified magnetic particles for chiral discrimination of racemic tryptophan

Enzymes possess a highly specific affinity toward their substrates. In this study, an enzyme-based biological method was established for chiral discrimination of D/L-tryptophan (Trp). The polydopamine modified magnetic particles (PDA@Fe₃O₄) were prepared for immobilization of the genetically engineered bacterium Escherichia coli (E. coli) DH5α. The bacteria-magnetic particles conjugates (bacteria@PDA@Fe₃O₄) demonstrate excellent chiral discrimination performance toward D/L-Trp at pH 7.0 and 45 °C. The investigation for the principle exhibits that the immobilized E. coli DH5α can produce tryptophanase, and the enzyme can selectively recognize and degrade L-Trp. The Michaelis constant of tryptophanase produced by bacteria@PDA@Fe₃O₄ was measured to be 25.7 µg mL^-1. This method avoids the purification of tryptophanase and unlocks the potential of bacteria modified magnetic particles for chiral discrimination of racemic tryptophan.

Sonochemically modified ovalbumin enhances enantioenrichment of some amino acids

As part of our efforts to develop a new method for chiral resolution of amino acids with sonochemically modified proteins, we present result that indicates how ovalbumin microspheres (OAMS) interact specifically with l-amino acids from a racemate in solution, leaving an excess of d-enantiomer in the permeate solution. Among different amino acids that interacted with the OAMS, tryptophan (Trp) was the most successfully resolved with 65% enantiomeric excess. A control experiment with native ovalbumin in solution did not show any chiral resolution of amino acids. Interestingly, when the OAMS were pretreated with racemic lysine (Lys) solution and then used for resolution of tryptophan the enantiomeric enrichment of d-tryptophan was raised to 98%. This unanticipated positive effect is discussed in terms of the structural correlation between Trp and Lys, which is less apparent in other amino acids such as phenylalanine.