Microwave-induced inactivation of DNA-based hybrid catalyst in asymmetric catalysis

Abstract

DNA-based hybrid catalysts have gained strong interests in asymmetric reactions. However, to maintain the high enantioselectivity, these reactions are usually conducted at relatively low temperatures (e.g. < 5 °C) for 2–3 days. Aiming to improve the reaction’s turnover rate, we evaluated microwave irradiation with simultaneous cooling as potential energy source since this method has been widely used to accelerate various chemical and enzymatic reactions. However, our data indicated that microwave irradiation induced an inactivation of DNA-based hybrid catalyst even at low temperatures (such as 5 °C). Circular dichroism (CD) spectra and gel electrophoresis of DNA suggest that microwave exposure degrades DNA molecules and disrupts DNA double-stranded structures, causing changes of DNA–metal ligand binding properties and thus poor DNA catalytic performance.

The non-thermal biological effects and mechanisms of microwave exposure

“…Garaj-Vrhovac et al (33) found that workers occupationally exposed to pulsed marine radar frequencies (3, 5.5 and 9.4 GHz) have statistically significant differences between the mean tail intensities (0.67 vs. 1.22) and moments (0.08 vs. 0.16) assessed via comet assays and micronucleus tests, showing the effects of microwaves on micronuclei, nucleoplasmic bridges and nuclear buds. Additionally, Zhao et al (34) have reported that microwave irradiation at a frequency of 2.45 GHz induced an inactivation of DNA-based hybrid catalyst even at low temperatures (such as 5 °C), and a substantial amount of DNA molecules degraded and lost their characteristic structures. Furthermore, Deshmukh et al (35) have also shown that low level subchronic microwave radiation at frequencies 900, 1800, and 2450 MHz for 2h a day, 5d a week for 90 days might lead to decline in cognitive function on rat brain as evidenced by DNA damage and increased heat shock protein 70 (HSP70) level in hippocampus tissues which could induce hazardous effects in rats.…”

A Thermodynamic Study on Hydration and Dehydration of DNA and RNA −Amphiphile Complexes

“…Hexagonal packing of DNA and RNA was observed for DNA and RNA complexes with Cetyltrimethyl Ammonium Bromide (CTBA) and for Dimethyldioctadecyl Ammonium Bromide (DDAB) complexes is observed lamellar structure. Variations in the internal spacing and degree of long-range ordering are dependent on both surfactant type and concentrations of added salt [19][20][21][22][23][24][25][26][27][28][29]. When we increased the amount of salt into our complexes, we observed that the d spacing (d=2Π/r) are increased.…”