Molecular Motors in Aqueous Environment

Abstract

Molecular motors are Nature’s solution for (supra)molecular transport and muscle functioning and are involved in most forms of directional motion at the cellular level. Their synthetic counterparts have also found a myriad of applications, ranging from molecular machines and smart materials to catalysis and anion transport. Although light-driven rotary molecular motors are likely to be suitable for use in an artificial cell, as well as in bionanotechnology, thus far they are not readily applied under physiological conditions. This results mainly from their inherently aromatic core structure, which makes them insoluble in aqueous solution. Here, the study of the dynamic behavior of these motors in biologically relevant media is described. Two molecular motors were equipped with solubilizing substituents and studied in aqueous solutions. Additionally, the behavior of a previously reported molecular motor was studied in micelles, as a model system for the biologically relevant confined environment. Design principles were established for molecular motors in these media, and insights are given into pH-dependent behavior. The work presented herein may provide a basis for the application of the remarkable properties of molecular motors in more advanced biohybrid systems.

From Molecular Machines to Stimuli‐Responsive Materials

“…Interestingly, while the fast motor (half‐life time of 40 ns at 20 °C) did not produce any morphological change upon light irradiation, the slower one (270 h at 20 °C) gave rise to vesicles which could be reversibly transform into nanotubes upon heating (Figure a‐iii–viii). More recently, a hydrophobic second‐generation motor, which does not show any rotation in water, could be dissolved in SDS micelles . The motor remained stable for several days, and functions over a large pH range (2–10) to fully rotate up to 13 cycles within the self‐assembled nanostructures and showing a photo‐ and thermochemical behavior similar to the ones recorded in hexane (half‐life of 4.93 min within micelles vs 3.17 min in hexane).…”

“…Self‐assembled 3D materials built from unidirectional molecular motors have emerged only very recently . In 2016, the group of Feringa reported the synthesis of two asymmetric molecular motors having different rotation frequencies and bearing one hydrophilic ammonium side chain on the upper part and two hydrophobic alkyl chains on the lower part ( Figure a) .…”

Sulfonated Pyrene as a Photoregulator for Single‐Stranded DNA Looping

“…In spite of the many advances achieved in the past decades, high controllability, high efficiency, and eligibility for physiological application still remain significant problems. This has inspired various groups to explore novel photoregulating approaches in the hope of mimicking the natural molecular motors observed in living organisms . Because most photoswitching molecules are hydrophobic, a main challenge for photoregulating the conformation and function of biomolecules under physiological conditions is the design of water‐soluble photoregulators …”

Bionanomateriais para o cruzamento de barreira biológica e entrega controlada

“…[70][71][72][73] Most systems release the drugs upon the burst or destruction of the system, except for the ones based on photoisomerization. 74 Photoisomerization of light-driven molecular motors induces a shift to a nonequilibrium state, leading to a rotary motion with spatial-temporal precision, [75][76] In 20 Transcytosis is a transcellular vesicular transport pathway from blood to brain and vice versa, which allows for the transport of bigger molecules and particles. The process essentially involves endocytosis, followed by intracellular vesicular transport and, exocytosis at the opposite side of the BBB.…”

“…where / represents the rate of permeation of dextran (µg min -1 ), A is the surface area (cm 2 ), 0 is the initial concentration of FITC-dextran (µg The observed p(NIPMAM) nanogel thermoresponsive behavior reveals an inverse correlation between cross-linking density and swelling ratio, which is in accordance with literature, i.e., micro/nanogels with higher cross-linking density show a lower swelling ratio, which is indicative for an enhanced stiffness. 75,79…”