Simulating signatures of two-dimensional electronic spectra of the Fenna-Matthews-Olson complex: By using a numerical path integral.

A framework for simulating electronic spectra from photon-echo experiments is constructed by using a numerical path integral technique. This method is non-Markovian and nonperturbative and, more importantly, is not limited by a fixed form of the spectral density functions of the environment. Next, a two-dimensional (2D) third-order electronic spectrum of a dimer system is simulated. The spectrum is in agreement with the experimental and theoretical results previously reported [for example, M. Khalil, N. Demirdöven, and A. Tokmakoff, Phys. Rev. Lett. 90, 047401 (2003)]. Finally, a 2D third-order electronic spectrum of the Fenna-Matthews-Olson (FMO) complex is simulated by using the Debye, Ohmic, and Adolphs and Renger spectral density functions. It is shown that this method can clearly produce the spectral signatures of the FMO complex by using only the Adolphs and Renger spectral density function. Plots of the evolution of the diagonal and cross-peaks show that they are oscillating with the population time.

Transient Chiral Dynamics in the Fenna-Matthews-Olson Complex Revealed by Two-Dimensional Circular Dichroism Spectroscopy.

Chirality plays a pivotal role across scientific disciplines with profound implications spanning light-matter interactions, molecular recognition, and natural evolutionary processes. This study delves into the active influence of molecular chirality on exciton energy transfer within photosynthetic protein complexes, focusing on the Fenna-Matthews-Olson (FMO) complex. Employing two-dimensional circular dichroism (2DCD) spectroscopy, we investigate the transient chiral dynamics of excitons during energy transfer processes within the FMO complex. Our approach, incorporating pulse information into population dynamics based on the third-order response function, facilitates the calculation of 2DCD spectra and dynamics. This enables the extraction of chiral contributions to excitonic energy transfer and the examination of electronic wave functions. We demonstrate that 2DCD spectra offer excitation energies that are better resolved than those from conventional two-dimensional electronic spectroscopy. These findings deepen our understanding of exciton energy transfer mechanisms in natural photosynthesis, emphasizing the potential of 2DCD spectroscopy as a powerful tool for unraveling the chiral contribution to exciton dynamics.

Transient chiral dynamics revealed by two-dimensional circular dichroism spectroscopy.

Chirality has been considered as one of the key factors in the evolution of life in nature. It is important to uncover how chiral potentials of molecular systems play vital role in fundamental photochemical processes. Here, we investigate the role of chirality in photoinduced energy transfer in a model dimeric system, where the monomers are excitonically coupled. To observe transient chiral dynamics and energy transfer, we employ circularly polarized laser pulses in two-dimensional electronic spectroscopy to construct the two-dimensional circular dichroism (2DCD) spectral maps. Tracking time-resolved peak magnitudes in 2DCD spectra allows one to identify chirality induced population dynamics. The dynamics of energy transfer is revealed by the time-resolved kinetics of cross peaks. However, the differential signal of 2DCD spectra shows the magnitude of cross peaks is dramatically reduced at initial waiting time, which indicates the weak chiral interactions between two monomers. The downhill energy transfer is resolved by presenting a strong magnitude of cross peak in 2DCD spectra after long waiting time. The chiral contribution towards coherent and incoherent energy-transfer pathways in the model dimer system is further examined via control of excitonic couplings between two monomers. Applications are made to study the energy-transfer process in the Fenna-Matthews-Olson complex. Our work uncovers the potential of 2DCD spectroscopy to resolve the chiral-induced interactions and population transfers in excitonically coupled systems.

The Protective Effects of Water Extracts of Compound Turmeric Recipe on Acute Alcoholism: An Experimental Research Using a Mouse Model.

Acute alcoholism (AAI) is a common emergency. Currently, there is a lack of preventive and therapeutic drugs with superior safety and efficacy. Curcuma longa, Panax ginseng, Pueraria lobata, Pueraria flower, and Hovenia dulcis Thunb., which are the components of compound turmeric recipe (CTR), are, respectively, used in China as adjuvant therapeutic agents for AAI and alcoholic liver injury, respectively. The purpose of this research was to investigate the effect of traditional compound turmeric recipe in anti-inebriation treatment and to identify its underlying mechanisms. The mice were administered with CTR mixture, and ethanol was subsequently given to mice by gavage. The effects of CTR on the righting reflex, 24-hour survival, drunken behavior, blood ethanol concentration, and pathological changes of liver are depicted. The activities of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were detected. Besides, the activities of tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), cytochrome P450 (P450), superoxide dismutase (SOD), and malondialdehyde (MDA) in the liver and the levels of ß-endorphin (ß-EP) and leucine enkephalin (LENK) in the brain were also measured. Our results demonstrated that CTR can increase the activities of ADH, ALDH, P450, and SOD and decrease the contents of TNF-α, IL-8, and MDA in the liver. In addition, it can decrease the activities of ALT, AST, and ALP in serum and ß-EP and LENK activities in the brain. CTR showed effects on prevention of acute alcoholism, promoting wakefulness, and alleviating alcoholic liver injury, which were likely mediated by the above mechanisms.

Simulation of two-dimensional electronic spectra of phycoerythrin 545 at ambient temperature.

By using a hierarchical equations-of-motion approach, we reproduce the two-dimensional electronic spectra of phycoerythrin 545 from Rhodomonas CS24 at ambient temperature (294 K). The simulated spectra are in agreement with the experimental results reported in Wong et al. (Nat. Chem. 2012, 4, 396). The evolutions of cross peaks for rephasing spectra and diagonal peaks for nonrephasing spectra have also been plotted. The peaks oscillate with the population times, with frequencies, phases, and amplitudes of the oscillating curves also being qualitatively consistent with the experimental results.

Excitation energy transfer: study with non-Markovian dynamics.

In this paper, we investigate the non-markovian dynamics of a model to mimic the excitation energy transfer (EET) between chromophores in photosynthesis systems. The numerical path integral method is used. This method includes the non-Markovian effects of the environmental affects, and it does not need the perturbation approximation in solving the dynamics of systems of interest. It implies that the coherence helps the EET between chromophores through lasting the transfer time rather than enhancing the transfer rate of the EET. In particular, the non-markovian environment greatly increases the efficiency of the EET in the photosynthesis systems.

Decoherence dynamics of coherent electronic excited states in the photosynthetic purple bacterium Rhodobacter sphaeroides.

In this paper, we present a theoretical description to the quantum coherence and decoherence phenomena of energy transfer in photosynthesis observed in a recent experiment [Science 316, 1462 (2007)]. As a successive two-color laser pulses with selected frequencies cast on a sample of the photosynthetic purple bacterium Rb. sphaeroides two resonant excitations of electrons in chromophores can be generated. However, this effective two-level subsystem will interact with its protein environment and decoherence is inevitable. We describe this subsystem coupled with its environment as a dynamical spin-boson model. The non-Markovian decoherence dynamics is described using a quasiadiabatic propagator path integral (QUAPI) approach. With the photon-induced effective time-dependent level splitting energy and level flip coupling coefficient between the two excited states and the environment-induced non-Markovian decoherence dynamics, our theoretical result is in good agreement with the experimental data.