Effective screening of Coulomb repulsions in water accelerates reactions of like-charged compounds by orders of magnitude

Abstract

The reaction kinetics between like-charged compounds in water is extremely slow due to Coulomb repulsions. Here, we demonstrate that by screening these interactions and, in consequence, increasing the local concentration of reactants, we boost the reactions by many orders of magnitude. The reaction between negatively charged Coenzyme A molecules accelerates ~5 million-fold using cationic micelles. That is ~104 faster kinetics than in 0.5 M NaCl, although the salt is ~106 more concentrated. Rate enhancements are not limited to micelles, as evidenced by significant catalytic effects (104–105-fold) of other highly charged species such as oligomers and polymers. We generalize the observed phenomenon by analogously speeding up a non-covalent complex formation—DNA hybridization. A theoretical analysis shows that the acceleration is correlated to the catalysts’ surface charge density in both experimental systems and enables predicting and controlling reaction rates of like-charged compounds with counter-charged species.

Site-Specific Polymerization-Induced Electrostatic Self-Assembly: Synthesis of Highly Charged Salt-Tolerant Polyion Complex Nanoreactors

“…1 H NMR studies (Figure S25) unveil the ultrafast copolymerization in dilution (AEAM: 2.2%, AMPS: 3.0% w/ w), in which AEAM reacted faster than AMPS due to electrostatics enhanced proximity. 55,64 Figure 6B exhibits linear kinetics at k p app = 31.7 (AEAM) and 18.8 h −1 (AMPS), distinct from the as-reported alternating copolymerization feeding at [+]/[−] = 1.0. 30,42,43 These results suggest that reaction acceleration and sequence control are achieved in an ultrathin lamellar environment.…”

“…Finally, we explored the potential of H62M20/A100S90 ultrathin lamellae as a nanoreactor protocol to control the sequence of oppositely charged monomers in a seeded copolymerization, as shown in Figure A. 1 H NMR studies (Figure S25) unveil the ultrafast copolymerization in dilution (AEAM: 2.2%, AMPS: 3.0% w/w), in which AEAM reacted faster than AMPS due to electrostatics enhanced proximity. , Figure B exhibits linear kinetics at k p app = 31.7 (AEAM) and 18.8 h –1 (AMPS), distinct from the as-reported alternating copolymerization feeding at [+]/[−] = 1.0. ,, These results suggest that reaction acceleration and sequence control are achieved in an ultrathin lamellar environment. Ampholytic growing-chain sequence was assessed based on the kinetic results …”

“…In other words, PIC-driven assembly is mainly under entropy control. , Seeking strategies for kinetically arrested thermodynamically metastable PICs is needed for precision control over highly charged salt-tolerant PIC nanostructures. We envision that charged salt-tolerant PIC nanoparticles can be achieved via molecular recognition − through kinetically arresting complexation of charged growing chains to one specific block of an oppositely charged block copolyelectrolyte.…”

“…55,64 In this sense, the ultrathin lamellae played a nanoreactor role in the sequence-controllable ultrafast copolymerization, mainly via electrostatic control. 55 The reaction mixture remained transparent under visible light up to >99% conversions (Figure S27). DLS studies unveil a linear decrease in light scattering intensity on dilution of the final dispersion, and ⟨D h ⟩ = 289 nm, PDI = 0.32 are detected for the particles at 70 mg/mL in water (Figure S28).…”

“…Note that, the lamellae ζ-potential shifts from −42 to −34 mV upon adding into the aqueous solution of oppositely charged monomers, suggesting that cationic monomer molecules preferentially recruit into densely charged anionic lamellae. 55,64 In this sense, the ultrathin lamellae played a nanoreactor role in the sequence-controllable ultrafast copolymerization, mainly via electrostatic control. 55 The reaction mixture remained transparent under visible light up to >99% conversions (Figure S27).…”