Chemical reactivity of the tryptophan/acetone/DMSO triad system and its potential applications in nanomaterial synthesis

Abstract

This study explores the surprising browning reaction of tryptophan in acetone/DMSO, revealing mild self-aldol condensation phenomena and potential applications in nanomaterial synthesis.

A nano-platform harnessing synergistic amino acid browning for biomedical applications

“…In this study, we chose the C – K system to investigate the feasibility of preparing nanomaterials from the browning products of binary amino acids, based on the following considerations. First, like the tryptophan system, 17 our HPLC analysis shows multiple peaks with significantly extended retention times on a reverse-phase chromatographic system (Fig. S3, ESI†), indicating the hydrophobic nature of the browning products.…”

“…While the reaction mechanism of the solvent-mediated browning of dual amino acids has yet to be fully characterized in separate studies, our previous investigation into the single tryptophan system provides some initial insights. 17 In contrast to the significant browning observed in the tryptophan-alone system, lysine alone exhibits minimal browning, and cysteine shows no browning at all. 16,17 However, the current study demonstrates that the combination of lysine and cysteine within the same solvent system produces a browning effect comparable to that of tryptophan alone.…”

“…17 In contrast to the significant browning observed in the tryptophan-alone system, lysine alone exhibits minimal browning, and cysteine shows no browning at all. 16,17 However, the current study demonstrates that the combination of lysine and cysteine within the same solvent system produces a browning effect comparable to that of tryptophan alone. In addition to the visual evidence provided by colour formation, our HPLC-DAD analysis allows us to illustrate the reactivity of the dual amino acid system, confirming the synergistic effect between lysine and cysteine in terms of the abundance of chemical species generated from the reaction (Fig.…”

“…16 Intrigued by this phenomenon, we embarked on a series of experiments and made the discovery that this browning reaction is a general occurrence, extending its reach to pure proteins and even amino acids. 16 In our subsequent study, 17 we delved into the potential mechanism behind this novel amino acid browning reaction, which occurs spontaneously at room temperature, requiring only three components: tryptophan, DMSO, and acetone. We demonstrated that the initial self-aldol condensation of acetone, catalysed by tryptophan acting as an organocatalyst in our solvent system, may trigger further molecular condensations, ultimately leading to the formation of extended molecules with sufficient conjugated systems capable of absorbing visible light.…”

“…Furthermore, the hydrophobic properties of the light-absorbing species enable them to form nanoparticles in water, with bovine serum albumin serving as a stabilizing agent. 17…”