A new water-soluble polythiophene derivative as a probe for real-time monitoring adenosine 5'-triphosphatase activity in lysosome of living cells

Detection of the adenosine 5'-triphosphatase (ATPase) activity in lysosome of living cells is of great importance for clinical diagnosis of many related diseases, including cancer. In this work, a new water-soluble polythiophene derivative named ZnPT bearing both quaternary ammonium salt groups and dipicolylamine-Zn²⁺ (DPA-Zn²⁺) complexes in its side chain, was designed and synthesized for this propose. The probe mainly localized to lysosome with good biocompatibility and membrane penetration. The real-time, continuous, direct, and label-free assays were achieved through a fluorescence "turn-on" mode by taking advantages of the reaction specificity of ATPase with ATP and the high binding selectivity of ZnPT toward ATP substrate over its hydrolysis product (ADP). This well designed strategy should provide a facile and effective way for investigating ATPase-relevant biological processes.

Aggregation Prevention Assay for Chaperone Activity of Proteins Using Spectroflurometry

The ability to stabilize other proteins against thermal aggregation is one of the major characteristics of chaperone proteins. Molecular chaperones bind to nonnative conformations of proteins. Folding of the substrate is triggered by a dynamic association and dissociation cycles which keep the substrate protein on track of the folding pathway (Figure 1). Usually molecular chaperones exhibit differential affinities with different conformations of the substrate. With the exception of the sHsp family of molecular chaperones, the shift from a high-affinity binding state to the low-affinity release state is triggered by ATP binding and hydrolysis (Haselback and Buchner, 2015). Aggregation prevention assay is a simple, yet definitive assay to determine the chaperone activity of heat labile proteins such as Maltodextrin glucosidase (MalZ), Citrate Synthase (CS) and NdeI. This is based on the premise that proteins with chaperone like activity should prevent protein substrates (MalZ, CS and NdeI) from thermal aggregation. Here, we describe a detailed protocol for aggregation prevention assay using two different chaperone proteins, resistin and MoxR1, identified from our lab. Resistin, a human protein (hRes) and MoxR1 a Mycobacterium tuberculosis protein were analysed for their effect on prevention of MalZ/Citrate Synthase (CS)/NdeI aggregation. Figure 1.Mechanism of action of molecular chaperones. Citrate synthase folds via increasingly structured intermediates (I₁, I₂) from the unfolded state (U) to the folded state (N). Under heat shock conditions, this process is reversed.