Visible light-induced thymine dimerisation based on large localised field gradient by non-uniform optical near-field

Naoya Tate,Takashi Yatsui

doi:10.1038/s41598-019-54661-6

Naoya Tate, Takashi Yatsui

Open Access

https://doi.org/10.1038/s41598-019-54661-6

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Abstract

The localised excitations of several molecular reactions utilising optical irradiation have been studied in the field of molecular physics. In particular, deoxyribonucleic acid (DNA) strands organise the genetic information of all living matter. Therefore, artificial methods for freely controlling reactions using only light irradiation are highly desirable for reactions of these strands; this in regard with artificial protein synthesis, regional genetic curing, and stochastic analysis of several genetic expressions. Generally, DNA strands have strong absorption features in the deep ultra-violet (DUV) region, which are related to the degradation and reconstruction of the strand bonding structures. However, irradiation by DUV light unavoidably induces unintended molecular reactions which can damage and break the DNA strands. In this paper, we report a photo-induced molecular reaction initiated by the irradiation of DNA strands with visible light. We utilised photo-dissociation from the vibrational levels induced by non-uniform optical near-fields surrounding nanometric Au particles to which DNA strands were attached. The results were experimentally observed by a reduction in the DUV absorbance of the DNA strands during irradiation. There was a much higher yield of molecular reactions than expected due to the absorbance of visible light, and no defects were caused in the DNA strands.

Highlights

The localised excitations of several molecular reactions utilising optical irradiation have been studied in the field of molecular physics
We propose a photo-excitation method based on the characteristics of non-uniform optical near-fields (ONFs), which are induced through irradiation by visible light with a much lower optical energy than deep ultra-violet (DUV) light[9]
Because contributions from the excited vibrational levels originating from the non-uniform ONFs can compensate for the lack of activation energy for the degradation of deoxyribonucleic acid (DNA) strands, we expected the non-uniform ONFs to allow for photo-excitation at a much lower optical energy, thereby avoiding the initiation of any unintended molecular reactions

Summary

Introduction

The localised excitations of several molecular reactions utilising optical irradiation have been studied in the field of molecular physics. We utilised photo-dissociation from the vibrational levels induced by non-uniform optical near-fields surrounding nanometric Au particles to which DNA strands were attached. The development of artificial techniques for controlling the molecular reactions of DNA strands is a fundamental issue for experimental studies on artificial protein synthesis, regional genetic curing, and stochastic analysis of several genetic expressions[1,2]. The above-described photo-excitation methods have valuable advantages, excessive DUV irradiation will induce some unintended reactions which can damage and break DNA strands due to electronic dissociation[8]. We propose a photo-excitation method based on the characteristics of non-uniform optical near-fields (ONFs), which are induced through irradiation by visible light with a much lower optical energy than DUV light[9]. We quantitatively evaluate the applicability of our proposed approach

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Conclusion