Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 50
Filter
1.
BMC Cardiovasc Disord ; 24(1): 303, 2024 Jun 14.
Article in English | MEDLINE | ID: mdl-38877462

ABSTRACT

BACKGROUND: In patients who experience out-of-hospital cardiac arrest (OHCA), it is important to assess the association of sub-phenotypes identified by latent class analysis (LCA) using pre-hospital prognostic factors and factors measurable immediately after hospital arrival with neurological outcomes at 30 days, which would aid in making treatment decisions. METHODS: This study retrospectively analyzed data obtained from the Japanese OHCA registry between June 2014 and December 2019. The registry included a complete set of data on adult patients with OHCA, which was used in the LCA. The association between the sub-phenotypes and 30-day survival with favorable neurological outcomes was investigated. Furthermore, adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by multivariate logistic regression analysis using in-hospital data as covariates. RESULTS: A total of, 22,261 adult patients who experienced OHCA were classified into three sub-phenotypes. The factor with the highest discriminative power upon patient's arrival was Glasgow Coma Scale followed by partial pressure of oxygen. Thirty-day survival with favorable neurological outcome as the primary outcome was evident in 66.0% participants in Group 1, 5.2% in Group 2, and 0.5% in Group 3. The 30-day survival rates were 80.6%, 11.8%, and 1.3% in groups 1, 2, and 3, respectively. Logistic regression analysis revealed that the ORs (95% CI) for 30-day survival with favorable neurological outcomes were 137.1 (99.4-192.2) for Group 1 and 4.59 (3.46-6.23) for Group 2 in comparison to Group 3. For 30-day survival, the ORs (95%CI) were 161.7 (124.2-212.1) for Group 1 and 5.78 (4.78-7.04) for Group 2, compared to Group 3. CONCLUSIONS: This study identified three sub-phenotypes based on the prognostic factors available immediately after hospital arrival that could predict neurological outcomes and be useful in determining the treatment strategy of patients experiencing OHCA upon their arrival at the hospital.


Subject(s)
Latent Class Analysis , Out-of-Hospital Cardiac Arrest , Registries , Humans , Out-of-Hospital Cardiac Arrest/mortality , Out-of-Hospital Cardiac Arrest/diagnosis , Out-of-Hospital Cardiac Arrest/therapy , Out-of-Hospital Cardiac Arrest/physiopathology , Male , Female , Japan/epidemiology , Aged , Middle Aged , Retrospective Studies , Time Factors , Risk Factors , Cardiopulmonary Resuscitation , Aged, 80 and over , Treatment Outcome , Risk Assessment , Phenotype , Glasgow Coma Scale , Predictive Value of Tests , Prognosis
2.
J Back Musculoskelet Rehabil ; 37(1): 3-12, 2024.
Article in English | MEDLINE | ID: mdl-37599518

ABSTRACT

BACKGROUND: Knee pain is the main symptom of knee osteoarthritis. Walking is effective against knee pain, and some studies have shown that gait modification can also relieve this condition. However, the quality of evidence for the clinically significant effects of gait modification on knee pain has not been examined. OBJECTIVE: This systematic review and meta-analysis aimed to evaluate the level of evidence for the clinically significant effects of gait modification on knee pain and determine if the effects are greater than the minimal clinically important difference (MCID). METHODS: We comprehensively searched electronic databases such as MEDLINE, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, and Cumulative Index to Nursing and Allied Health Literature. Intervention studies with experimental groups who received gait modification and control groups who did not were evaluated. The Grading of Recommendations Assessment, Development and Evaluation system was used to assess the level of evidence. RESULTS: Nine studies met the inclusion criteria. All were included in the systematic review and two in the meta-analysis. Results showed that gait modification have significant effects (p= 0.02), and the quality of evidence was very low. However, several studies have revealed that the effects of gait modification, when used as a foot-focused intervention, were greater than the MCID. CONCLUSIONS: We concluded that there is a lack of high-quality evidence that supports the general efficacy of gait modification. Although based on low-quality evidence, when applied to the foot, it may have clinically significant effects.


Subject(s)
Osteoarthritis, Knee , Humans , Osteoarthritis, Knee/therapy , Osteoarthritis, Knee/diagnosis , Walking , Pain , Gait
3.
Am J Emerg Med ; 77: 233.e5-233.e7, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38155033

ABSTRACT

Naphazoline, a nonspecific alpha-adrenoceptor stimulant, is a potent vasoconstrictor used in nasal sprays, eye drops, and over-the-counter antiseptics. Naphazoline intoxication increases afterload by constricting the peripheral arteries, which can lead to complications including multiple organ failure. Although phentolamine, a nonselective alpha-adrenoceptor antagonist, and nicardipine, a calcium channel blocker, are used for the treatment of naphazoline intoxication, no established administration protocols currently exist. We present the case of a 32-year-old male with depression who ingested 150 mL of an antiseptic containing 0.1% naphazoline (equivalent to 150 mg of naphazoline). Five hours after ingestion, the patient was admitted to hospital exhibiting signs of naphazoline intoxication, such as bradycardia (46 beats/min), blood pressure of 166/122 mmHg, and peripheral cyanosis. We used the FloTrac™/EV1000™ system (Edwards Lifesciences, Irvine, CA, USA), a minimally invasive cardiac output monitoring system, to monitor systemic vascular resistance. The systemic vascular resistance index (SVRI) was elevated (4457 dyne.s/cm5/m2; nomal range: 1970-2390 dyne.s/cm5/m2) upon admission and initial treatment with continuous intravenous infusion of phentolamine led to SVRI normalization within 2 h. With the goal of maintaining SVRI normalization, continuous infusion with nicardipine was then started. At 10 h after treatment initiation, the nicardipine dose peaked at 9 mg/h (1.9 µg/kg/min). Treatment was discontinued 8 h later, and the patient was discharged on the fourth day without sequelae. In conclusion, the use of a minimally invasive cardiac output monitoring system to track vascular resistance can effectively guide the dosing of phentolamine or nicardipine in the treatment of naphazoline intoxication.


Subject(s)
Naphazoline , Nicardipine , Male , Humans , Adult , Phentolamine , Cardiac Output , Receptors, Adrenergic
4.
J Phys Chem B ; 127(48): 10351-10359, 2023 Dec 07.
Article in English | MEDLINE | ID: mdl-38014591

ABSTRACT

Blue light using flavin (BLUF) domain proteins are photoreceptors in various organisms. The PixD BLUF domain can adopt two conformations, W91out and W91in, with Trp91 either proximal or distal to flavin (FMN). Using a quantum mechanical/molecular mechanical/polarizable continuum model approach, the energetics of charge-separated and biradical states in the two conformations were investigated. In the W91out conformation, the charge-separated state (FMN•-) is more stable than the photoexcited state (FMN*), whereas it is less stable due to an electrostatic repulsive interaction with the Ser28 side chain in the W91in conformation. This leads to a lower activation energy for the charge separation in the W91out conformation, resulting in a faster charge separation compared to that in the W91in conformation. In the W91out conformation, the radical state (FMNH•) is more stable than FMN•- and forms from FMN•-, leading to reorientation of the Gln50 side chain adjacent to FMN and formation of a hydrogen bond between Gln50 and FMN. Subsequently, a signaling state forms through charge recombination. In contrast, in the W91in conformation, FMN•- cannot proceed further, returning to the dark-adapted state, as FMNH• is less stable. Thus, formation of the signaling state exclusively occurs in the W91out conformation.


Subject(s)
Photoreceptors, Microbial , Photoreceptors, Microbial/chemistry , Light , Protein Structure, Tertiary , Models, Molecular , Flavins/chemistry , Bacterial Proteins/chemistry
5.
PLoS One ; 18(8): e0289698, 2023.
Article in English | MEDLINE | ID: mdl-37611042

ABSTRACT

BACKGROUND AND AIMS: Emergency endoscopic hemostasis for colonic diverticular bleeding is effective in preventing serious consequences. However, the low identification rate of the bleeding source makes the procedure burdensome for both patients and providers. We aimed to establish an efficient and safe emergency endoscopy system. METHODS: We prospectively evaluated the usefulness of a scoring system (Jichi Medical University diverticular hemorrhage score: JD score) based on our experiences with past cases. The JD score was determined using four criteria: CT evidence of contrast agent extravasation, 3 points; oral anticoagulant (any type) use, 2 points; C-reactive protein ≥1 mg/dL, 1 point; and comorbidity index ≥3, 1 point. Based on the JD score, patients with acute diverticular bleeding who underwent emergency or elective endoscopy were grouped into JD ≥3 or JD <3 groups, respectively. The primary and secondary endpoints were the bleeding source identification rate and clinical outcomes. RESULTS: The JD ≥3 and JD <3 groups included 35 and 47 patients, respectively. The rate of bleeding source identification, followed by the hemostatic procedure, was significantly higher in the JD ≥3 group than in the JD <3 group (77% vs. 23%, p <0.001), with a higher JD score associated with a higher bleeding source identification rate. No significant difference was observed between the groups in terms of clinical outcomes, except for a higher incidence of rebleeding at one-month post-discharge and a higher number of patients requiring interventional radiology in the JD ≥3 group than in the JD <3 group. Subgroup analysis showed that successful identification of the bleeding source and hemostasis contributed to a shorter hospital stay. CONCLUSION: We established a safe and efficient endoscopic scoring system for treating colonic diverticular bleeding. The higher the JD score, the higher the bleeding source identification, leading to a successful hemostatic procedure. Elective endoscopy was possible in the JD <3 group when vital signs were stable.


Subject(s)
Diverticular Diseases , Diverticulum , Hemostatics , Humans , Pilot Projects , Aftercare , Universities , Patient Discharge , Endoscopy, Gastrointestinal , Diverticular Diseases/complications , Hemorrhage
6.
Biophys J ; 122(3): 470-483, 2023 02 07.
Article in English | MEDLINE | ID: mdl-36609140

ABSTRACT

We evaluated excitation energy transfer (EET) coupling (J) between all pairs of chlorophylls (Chls) and pheophytins (Pheos) in the protein environment of photosystem II based on the time-dependent density functional theory with a quantum mechanical/molecular mechanics approach. In the reaction center, the EET coupling between Chls PD1 and PD2 is weaker (|J(PD1/PD2)| = 79 cm-1), irrespective of a short edge-to-edge distance of 3.6 Å (Mg-to-Mg distance of 8.1 Å), than the couplings between PD1 and the accessory ChlD1 (|J(PD1/ChlD2)| = 104 cm-1) and between PD2 and ChlD2 (|J(PD2/ChlD1)| = 101 cm-1), suggesting that PD1 and PD2 are two monomeric Chls rather than a "special pair". There exist strongly coupled Chl pairs (|J| > âˆ¼100 cm-1) in the CP47 and CP43 core antennas, which may be candidates for the red-shifted Chls observed in spectroscopic studies. In CP47 and CP43, Chls ligated to CP47-His26 and CP43-His56, which are located in the middle layer of the thylakoid membrane, play a role in the "hub" that mediates the EET from the lumenal to stromal layers. In the stromal layer, Chls ligated to CP47-His466, CP43-His441, and CP43-His444 mediate the EET from CP47 to ChlD2/PheoD2 and from CP43 to ChlD1/PheoD1 in the reaction center. Thus, the excitation energy from both CP47 and CP43 can always be utilized for the charge-separation reaction in the reaction center.


Subject(s)
Chlorophyll , Photosystem II Protein Complex , Photosystem II Protein Complex/chemistry , Chlorophyll/chemistry , Energy Transfer
7.
Healthcare (Basel) ; 11(2)2023 Jan 10.
Article in English | MEDLINE | ID: mdl-36673582

ABSTRACT

In this study, we seek to clarify whether the present-day experience of psychological distress among adults whose parents suffered from mental illness is related to their childhood experiences of abuse and neglect and their provision of emotional care for their parents during their school-age years. To this end, a web-based cross-sectional study was conducted. A total of 120 participants over the age of 20 who attended a self-help group responded (50% response rate); of these, 94 had a parent diagnosed with a mental illness, and these participants were included for data analysis purposes. Of the 94 respondents, 65 (69.2%) were highly distressed, as measured by a Kessler (K) 6 measure of ≥5. A logistic regression analysis revealed that the experience of providing emotional care for parents during school-age childhood was significantly related to high levels of distress in adulthood (OR = 3.48; 95% CI 1.21-9.96). For children of parents with mental illnesses, the effects of providing emotional care for parents during childhood may include long-term psychological distress. For this reason, mentally ill parents raising children need visiting community nurses or other professionals to provide emotional care on behalf of their children.

8.
J Phys Chem B ; 127(1): 205-211, 2023 01 12.
Article in English | MEDLINE | ID: mdl-36542840

ABSTRACT

The electron transfer from the oxygen-evolving Mn4CaO5 cluster to the electron acceptor D1-Tyr161 (TyrZ) is a prerequisite for water oxidation and O2 evolution. Here, we analyzed the electronic coupling in the rate-limiting electron-transfer transitions using a combined quantum mechanical/molecular mechanical/polarizable continuum model approach. In the S0 to S1 transition, the electronic coupling between the electron-donor Mn3(III) and TyrZ is small (2 meV). In contrast, the electronic coupling between the dangling Mn4(III) and TyrZ is significantly large (172 meV), which suggests that the electron transfer proceeds from Mn3(III) to TyrZ via Mn4(III). In the S1 to S2 transition, the electronic coupling between Mn4(III) and TyrZ is also larger (124 meV) than that between Mn1(III) and TyrZ (1 meV), which favors the formation of the open-cubane S2 conformation with Mn4(IV) over the formation of the closed-cubane S2 conformation with Mn1(IV). In the S0 to S1 and S1 to S2 transitions, the Mn4 d-orbital and the TyrZ π-orbital are hybridized via D1-Asp170, which suggests that D1-Asp170 commonly provides a dominant electron-transfer route.


Subject(s)
Electrons , Photosystem II Protein Complex , Photosystem II Protein Complex/metabolism , Electron Transport , Oxidation-Reduction , Water , Oxygen
9.
J Aging Phys Act ; 31(2): 319-329, 2023 04 01.
Article in English | MEDLINE | ID: mdl-35961641

ABSTRACT

Increased physical activity is an effective treatment for knee osteoarthritis that causes knee pain. However, due to the coronavirus disease 2019, noncontact and non-face-to-face interventions have increased, but the quality of evidence supporting their effectiveness remains unclear. The purpose of the study was to assess the quality of evidence of the effects of non-face-to-face and noncontact interventions on knee pain and physical activity in older adults with knee osteoarthritis. A meta-analysis was conducted to determine the effects of different intervention methods (education and exercise). The Cochrane Central Register of Controlled Trials, PubMed, Cumulative Index to Nursing and Allied Health Literature, and Physiotherapy Evidence Database were systematically searched. Four randomized controlled trials were included in the analysis. The meta-analysis demonstrated that the educational intervention group was significantly effective, although supportive evidence was low quality. Educational intervention may be effective, but the effects need to be confirmed by higher quality clinical trials.


Subject(s)
COVID-19 , Osteoarthritis, Knee , Humans , Aged , Osteoarthritis, Knee/therapy , Exercise , Knee Joint , Pain , Exercise Therapy/methods
10.
J Phys Chem B ; 126(46): 9549-9558, 2022 11 24.
Article in English | MEDLINE | ID: mdl-36374126

ABSTRACT

In photosynthetic reaction centers from purple bacteria (PbRCs) and photosystem II (PSII), the photoinduced charge separation is terminated by an electron transfer between the primary (QA) and secondary (QB) quinones. Here, we investigate the electron transfer route, calculating the superexchange coupling (HQA-QB) for electron transfer from QA to QB in the protein environment. HQA-QB is significantly larger in PbRC than in PSII. In superexchange electron tunneling, the electron transfer via unoccupied molecular orbitals of the nonheme Fe complex (QA → Fe → QB) is pronounced in PbRC, whereas the electron transfer via occupied molecular orbitals (Fe → QB followed by QA → Fe) is pronounced in PSII. The significantly large HQA-QB is caused by a water molecule that donates the H-bond to the ligand Glu-M234 in PbRC. The corresponding water molecule is absent in PSII due to the existence of D1-Tyr246. HQA-QB increases in response to the Ser-L223···QB H-bond formation caused by an extension of the H-bond network, which facilitates charge delocalization over the QB site. This explains the observed discrepancy in the QA-to-QB electron transfer between PbRC and PSII, despite their structural similarity.


Subject(s)
Electrons , Quinones , Quinones/chemistry , Electron Transport , Photosystem II Protein Complex/metabolism , Water
11.
Phys Chem Chem Phys ; 24(35): 21367-21371, 2022 Sep 14.
Article in English | MEDLINE | ID: mdl-36043636

ABSTRACT

Self-assembled coordination cages composed of metal cations and ligands can enhance the hydrolysis of non-covalently trapped amides in mild conditions as demonstrated in recent experiments. Here, we reveal the mechanism that accelerates base-catalyzed amide hydrolysis inside the octahedral coordination cage, by means of a quantum mechanics/molecular mechanics/polarizable continuum model. The calculated activation barrier of the nucleophilic OH- addition to a planar diaryl amide drastically decreases in the cage because of mechanical bond-twisting due to host-guest π-stacking. By contrast, the OH- addition to an N-acylindole, which possesses a twisted amide bond in bulk water, is not enhanced in the cage. Even though the cage hinders OH- collisions with the confined amide, the cage can twist the dihedral angle of the planar amide so as to mimic the transition state of OH- addition.


Subject(s)
Amides , Water , Amides/chemistry , Hydrolysis , Ligands , Models, Molecular , Water/chemistry
12.
Musculoskelet Sci Pract ; 62: 102627, 2022 Dec.
Article in English | MEDLINE | ID: mdl-35926473

ABSTRACT

BACKGROUND: International guidelines recommend educational intervention to treat knee osteoarthritis. However, they do not specify the type of intervention and the effectiveness of group educational intervention for knee pain is unclear. OBJECTIVES: We aimed to examine the effectiveness of group educational interventions for people over 50 years old with knee pain compared with a control group. DESIGN: A systematic review and meta-analysis of randomized controlled trials (RCTs). METHOD: We searched Medline, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database, and Cumulative Index to Nursing and Allied Health Literature and screened for RCTs involving participants over 50 years old that reported the effects of group education on knee pain. We performed meta-analyses and evaluated the methodological quality and evidence quality using the Physiotherapy Evidence Database scale and the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system, respectively. RESULTS: The search retrieved 1,177 studies. Seven RCTs were ultimately included, four of which were subjected to meta-analysis, showing standardized mean differences of -0.22 (95% confidence interval [CI]: -0.42 to -0.02, n = 423; I2 = 0% GRADE: low). All studies included in the meta-analysis involved exercise without individualized instruction in addition to group educational intervention. CONCLUSIONS: Group education, when delivered in addition to exercises, significantly reduces knee pain in people over 50 years old.


Subject(s)
Exercise Therapy , Osteoarthritis, Knee , Humans , Middle Aged , Osteoarthritis, Knee/therapy , Exercise , Pain , Physical Therapy Modalities
13.
iScience ; 25(5): 104247, 2022 May 20.
Article in English | MEDLINE | ID: mdl-35521532

ABSTRACT

In low-barrier hydrogen bonds (H-bonds), the pK a values for the H-bond donor and acceptor moieties are nearly equal, whereas the redox potential values depend on the H+ position. Spectroscopic details of low-barrier H-bonds remain unclear. Here, we report the absorption wavelength along low-barrier H-bonds in protein environments, using a quantum mechanical/molecular mechanical approach. Low-barrier H-bonds form between Glu46 and p-coumaric acid (pCA) in the intermediate pRCW state of photoactive yellow protein and between Asp116 and the retinal Schiff base in the intermediate M-state of the sodium-pumping rhodopsin KR2. The H+ displacement of only ∼0.4 Å, which does not easily occur without low-barrier H-bonds, is responsible for the ∼50 nm-shift in the absorption wavelength. This may be a basis of how photoreceptor proteins have evolved to proceed photocycles using abundant protons.

15.
Acta Bioeng Biomech ; 24(4): 13-19, 2022.
Article in English | MEDLINE | ID: mdl-37341057

ABSTRACT

PURPOSE: Gait changes are more prominently observed in older adults than in young adults, especially in kinematics of lower extremities and trunk. These changes can result in incidental falls during gait, possibly leading to inability to perform activities of daily living independently. This study aimed to investigate the effect of gender and age on gait changes, such as spatiotemporal parameters and peak joint angles in lower extremities and trunk during gait. METHODS: A total of 387 participants (223 women) were included. The Microsoft Kinect V2 sensor was used to obtain the coordinate data of lower extremities and trunk during gait. The coordinate data obtained were processed using the software. Walking speed, stride length, stride time and cadence were calculated as spatiotemporal variables of walking. Forward trunk tilt angle (FTT), hip flexion and extension, and knee flexion and extension were measured as peak angles during one-gait cycle. Participants were categorized into five groups according to age by five years. Multivariate analysis of variance was performed to compare the spatiotemporal and kinematical data among groups. RESULTS: Significant differences among age groups were noted in terms of the walking speed and stride length. Significant differences were also observed in the FTT and hip extension angle. CONCLUSIONS: Increased gait changes, increased peak FTT and decreased peak hip extension angle were observed with an increase of age. These altered symptoms may contribute to the screening of older adults at risk of declined physical function at an early stage.


Subject(s)
Activities of Daily Living , Gait , Young Adult , Humans , Female , Aged , Child, Preschool , Biomechanical Phenomena , Walking , Lower Extremity
16.
J Phys Chem B ; 125(49): 13460-13466, 2021 12 16.
Article in English | MEDLINE | ID: mdl-34875835

ABSTRACT

The mechanisms governing the long-range electron tunneling from the primary (QA) to secondary (QB) quinones in photosystem II are clarified by analyzing superexchange pathways through a nonheme Fe complex, using a quantum mechanics/molecular mechanics/polarizable continuum model approach. The electron tunneling rate is evaluated using the Marcus-Levich-Jortner theory considering electronic coupling, energy difference, and Franck-Condon factor. The superexchange QA → QB electron tunneling is enhanced by hybridized σ/σ* orbitals of histidines (D2-His214 and D1-His215) via penetration of the wave function into hydrogen bonds with both QA and QB. Despite a large energy gap to the intermediate states, the contributions of the histidine σ/σ* orbitals to the superexchange coupling are larger than those of π/π* orbitals. Fe2+ is not an essential component for the QA → QB electron tunneling because hybridized histidine molecular orbitals can be coupled with both QA and QB simultaneously in the absence of Fe d orbitals.


Subject(s)
Photosystem II Protein Complex , Quinones , Electron Transport , Electrons , Hydrogen Bonding , Models, Molecular , Photosystem II Protein Complex/metabolism
17.
Chem Sci ; 12(23): 8131-8140, 2021 May 05.
Article in English | MEDLINE | ID: mdl-34194703

ABSTRACT

Exciton charge separation in photosynthetic reaction centers from purple bacteria (PbRC) and photosystem II (PSII) occurs exclusively along one of the two pseudo-symmetric branches (active branch) of pigment-protein complexes. The microscopic origin of unidirectional charge separation in photosynthesis remains controversial. Here we elucidate the essential factors leading to unidirectional charge separation in PbRC and PSII, using nonadiabatic quantum dynamics calculations in conjunction with time-dependent density functional theory (TDDFT) with the quantum mechanics/molecular mechanics/polarizable continuum model (QM/MM/PCM) method. This approach accounts for energetics, electronic coupling, and vibronic coupling of the pigment excited states under electrostatic interactions and polarization of whole protein environments. The calculated time constants of charge separation along the active branches of PbRC and PSII are similar to those observed in time-resolved spectroscopic experiments. In PbRC, Tyr-M210 near the accessary bacteriochlorophyll reduces the energy of the intermediate state and drastically accelerates charge separation overcoming the electron-hole interaction. Remarkably, even though both the active and inactive branches in PSII can accept excitons from light-harvesting complexes, charge separation in the inactive branch is prevented by a weak electronic coupling due to symmetry-breaking of the chlorophyll configurations. The exciton in the inactive branch in PSII can be transferred to the active branch via direct and indirect pathways. Subsequently, the ultrafast electron transfer to pheophytin in the active branch prevents exciton back transfer to the inactive branch, thereby achieving unidirectional charge separation.

18.
J Phys Chem B ; 125(11): 2879-2885, 2021 03 25.
Article in English | MEDLINE | ID: mdl-33689376

ABSTRACT

Photosystem I has two active electron-transfer pathways. However, electron transfer occurs primarily along one of the two branches (A-branch) irrespective of the similar protein environments. Here, we report the origin of the A-branch electron transfer, considering the electronic coupling of the pigments and the electrostatic interaction with the protein environments. In the chlorophyll pair [PAPB], the electronic coupling between PA and PB is large (85 meV) for the highest occupied molecular orbital, forming the electronically coupled dimer [PAPB] and serving as an initial electron donor. In contrast, the coupling for the lowest unoccupied molecular orbital is small (15 meV), leading to charge transfer from PB to PA upon the [PAPB] excitation. The electronic coupling between [PAPB] and the accessory chlorophyll in the A-branch is significantly larger than that in the B-branch. These results indicate that the asymmetry of the electron-transfer activity originates from PA as a chlorophyll epimer.


Subject(s)
Electrons , Photosystem I Protein Complex , Chlorophyll , Electron Transport , Oxidation-Reduction , Photosystem I Protein Complex/metabolism , Photosystem II Protein Complex/metabolism
19.
Nature ; 587(7835): 594-599, 2020 11.
Article in English | MEDLINE | ID: mdl-33239799

ABSTRACT

The generation, control and transfer of triplet excitons in molecular and hybrid systems is of great interest owing to their long lifetime and diffusion length in both solid-state and solution phase systems, and to their applications in light emission1, optoelectronics2,3, photon frequency conversion4,5 and photocatalysis6,7. Molecular triplet excitons (bound electron-hole pairs) are 'dark states' because of the forbidden nature of the direct optical transition between the spin-zero ground state and the spin-one triplet levels8. Hence, triplet dynamics are conventionally controlled through heavy-metal-based spin-orbit coupling9-11 or tuning of the singlet-triplet energy splitting12,13 via molecular design. Both these methods place constraints on the range of properties that can be modified and the molecular structures that can be used. Here we demonstrate that it is possible to control triplet dynamics by coupling organic molecules to lanthanide-doped inorganic insulating nanoparticles. This allows the classically forbidden transitions from the ground-state singlet to excited-state triplets to gain oscillator strength, enabling triplets to be directly generated on molecules via photon absorption. Photogenerated singlet excitons can be converted to triplet excitons on sub-10-picosecond timescales with unity efficiency by intersystem crossing. Triplet exciton states of the molecules can undergo energy transfer to the lanthanide ions with unity efficiency, which allows us to achieve luminescent harvesting of the dark triplet excitons. Furthermore, we demonstrate that the triplet excitons generated in the lanthanide nanoparticle-molecule hybrid systems by near-infrared photoexcitation can undergo efficient upconversion via a lanthanide-triplet excitation fusion process: this process enables endothermic upconversion and allows efficient upconversion from near-infrared to visible frequencies in the solid state. These results provide a new way to control triplet excitons, which is essential for many fields of optoelectronic and biomedical research.

20.
J Phys Chem A ; 124(39): 7943-7949, 2020 Oct 01.
Article in English | MEDLINE | ID: mdl-32902271

ABSTRACT

Triplet exciton transfer (TET) and triplet-triplet annihilations (TTAs) in anthracene derivatives, namely, one of the polymorphs of 9,10-bis(triisopropylsilylethynyl)anthracene (TIPS-ANTp) and 1,2,3,4-tetrafluoro-5,8-bis(trimethylsilylethynyl)anthracene (F4-TMS-ANT), are analyzed theoretically. The electronic couplings for TET and TTA are evaluated by means of the diabatization scheme in conjunction with the time-dependent density functional theory and the multireference second-order Møller-Plesset method. The TET rate is estimated on the basis of Fermi's golden rule considering the Franck-Condon factor of intramolecular modes. TTA is analyzed by means of quantum dynamics calculations with the multiconfiguration time-dependent Hartree method. TET in the cofacially stacked F4-TMS-ANT is faster than that of the slip-stacked TIPS-ANTp. In the anthracene derivatives, a singlet exciton is lower in energy than a pair of triplets. F4-TMS-ANT can exhibit an ultrafast TTA via the superexchange pathway mediated by higher lying charge transfer (CT) states, owing to strong electronic couplings. In contrast, TIPS-ANTp exhibits an inefficient TTA via the direct pathway with a small two-electron coupling. The cofacial stacking decreases the energy gap to the intermediate CT states, thereby facilitating TET and TTA via the superexchange pathway.

SELECTION OF CITATIONS
SEARCH DETAIL
...