Sequence-Dependent Photocurrent Generation through Long-Distance Excess-Electron Transfer in DNA

Short-Range Charge Transfer in DNA Base Triplets: Real-Time Tracking of Coherent Fluctuation Electron Transfer

The short-range charge transfer of DNA base triplets has wide application prospects in bioelectronic devices for identifying DNA bases and clinical diagnostics, and the key to its development is to understand the mechanisms of short-range electron dynamics. However, tracing how electrons are transferred during the short-range charge transfer of DNA base triplets remains a great challenge. Here, by means of ab initio molecular dynamics and Ehrenfest dynamics, the nuclear-electron interaction in the thymine-adenine-thymine (TAT) charge transfer process is successfully simulated. The results show that the electron transfer of TAT has an oscillating phenomenon with a period of 10 fs. The charge density difference proves that the charge transfer proportion is as high as 59.817% at 50 fs. The peak position of the hydrogen bond fluctuates regularly between -0.040 and -0.056. The time-dependent Marcus-Levich-Jortner theory proves that the vibrational coupling between nucleus and electron induces coherent electron transfer in TAT. This work provides a real-time demonstration of the short-range coherent electron transfer of DNA base triplets and establishes a theoretical basis for the design and development of novel biological probe molecules.

Direct growth of two-dimensional phthalocyanine-based COF on Cu-MOF to construct a photoelectrochemical-electrochemical dual-mode biosensing platform for high-efficiency determination of Cr(III)

A photoelectrochemical (PEC)-electrochemical (EC) dual-mode biosensing strategy based on COF@MOF heterostructure was developed for efficiently analyzing Cr(III) ions. A two-dimensional phthalocyanine-based COF (CoPc-PT-COF) was in situ grown on a Cu-based MOF (Cu-MOF) substrate via covalent binding between carboxyl groups in Cu-MOF and amino groups in CoPc-PT-COF (denoted as CoPc-PT-COF@Cu-MOF). The coexistence of both phthalocyanine and bipyridine in CoPc-PT-COF@Cu-MOF affords the outperformed electro- and photo-activities, thus serving as a photoelectric beacon with favorable energy-band configuration and amplified electrochemical response. Due to the high porosity and rich functionality of the obtained heterostructure, the DNA strands can be tightly anchored over CoPc-PT-COF@Cu-MOF via diverse interactions. Thanks to the specific recognition between DNA strands and Cr³⁺ ions, the CoPc-PT-COF@Cu-MOF-based biosensor can be used to determine Cr³⁺ ions in an aqueous environment by PEC-EC mode. The gained biosensor shows an extremely low limit of detection (LOD) of 14.5 fM (for PEC) and 22.9 fM (for EC) within the Cr³⁺ concentration range from 0.1 pM to 100 nM, along with high selectivity, good reproducibility and stability. Moreover, this novel biosensor exhibits acceptable applicability for analyzing the trace Cr³⁺ from diverse samples (e.g., river and tap water). As a result, this work provides new insights into the construction of a high-efficiency PEC-EC dual-mode biosensor for detecting heavy metal ions from complex environments.

Reductive Charge Transfer through an RNA Aptamer

The transfer of charges through double helical DNA is a very well investigated bioelectric phenomenon. RNA, on the contrary, has been less studied in this regard. The few available data report on charge transfer through RNA duplex structures mainly composed of homonucleotide sequences. In the light of the RNA world scenarios, it is an interesting question, if charge transfer can be coupled with RNA function. Functional RNAs however, contain versatile structural motifs. Therefore, electron transport also through non‐Watson–Crick base‐paired regions might be required. We here demonstrate distance‐dependent reductive charge transfer through RNA duplexes and through the non‐Watson–Crick base‐paired region of an RNA aptamer.

How can infra-red excitation both accelerate and slow charge transfer in the same molecule?

A UV-IR-Vis 3-pulse study of infra-red induced changes to electron transfer (ET) rates in a donor-bridge-acceptor species finds that charge-separation rates are slowed, while charge-recombination rates are accelerated as a result of IR excitation during the reaction. We explore the underpinning mechanisms for this behavior, studying IR-induced changes to the donor-acceptor coupling, to the validity of the Condon approximation, and to the reaction coordinate distribution. We find that the dominant IR-induced rate effects in the species studied arise from changes to the density of states in the Marcus curve crossing region. That is, IR perturbation changes the probability of accessing the activated complex for the ET reactions. IR excitation diminishes the population of the activated complex for forward (activationless) ET, thus slowing the rate. However, IR excitation increases the population of the activated complex for (highly activated) charge recombination ET, thus accelerating the charge recombination rate.

Charge transfer dynamics in DNA revealed by time-resolved spectroscopy

In the past few decades, charge transfer in DNA has attracted considerable attention from researchers in a wide variety of fields, including bioscience, physical chemistry, and nanotechnology. Charge transfer in DNA has been investigated using various techniques. Among them, time-resolved spectroscopic methods have yielded valuable information on charge transfer dynamics in DNA, providing an important basis for numerical practical applications such as development of new therapy applications and nanomaterials. In DNA, holes and excess electrons act as positive and negative charge carriers, respectively. Although hole transfer dynamics have been investigated in detail, the dynamics of excess electron transfer have only become clearer relatively recently. In the present paper, we summarize studies on the dynamics of hole and excess electron transfer conducted by several groups including our own.