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1.
Adv Sci (Weinh) ; : e2310181, 2024 Mar 21.
Article in English | MEDLINE | ID: mdl-38514900

ABSTRACT

Electrochemical activation usually accompanies in situ atom rearrangement forming new catalytic sites with higher activity due to reconstructed atomic clusters or amorphous phases with abundant dangling bonds, vacancies, and defects. By harnessing the pre-catalytic process of reconstruction, a multilevel structure of CuNi alloy nanoparticles encapsulated in N-doped carbon (CuNi nanoalloy@N/C) transforms into a highly active compound of Ni-doped CuO nanocluster supported on (N/O-C) co-doped C. Both the exposure of accessible active sites and the activity of individual active sites are greatly improved after the pre-catalytic reconstruction. Manipulating the Cu/Ni ratios of CuNi nanoalloy@N/C can tailor the electronic property and d-band center of the high-active compound, which greatly optimizes the energetics of oxygen evolution reaction (OER) intermediates. This interplay among Cu, Ni, C, N, and O modifies the interface, triggers the active sites, and regulates the work functions, thereby realizing a synergistic boost in OER.

2.
Adv Sci (Weinh) ; : e2401611, 2024 Mar 21.
Article in English | MEDLINE | ID: mdl-38509850

ABSTRACT

Cell mechanotransduction signals are important targets for physical therapy. However, current physiotherapy heavily relies on ultrasound, which is generated by high-power equipment or amplified by auxiliary drugs, potentially causing undesired side effects. To address current limitations, a robotic actuation-mediated therapy is developed that utilizes gentle mechanical loads to activate mechanosensitive ion channels. The resulting calcium influx precisely regulated the expression of recombinant tumor suppressor protein and death-associated protein kinase, leading to programmed apoptosis of cancer cell line through caspase-dependent pathway. In stark contrast to traditional gene therapy, the complete elimination of early- and middle-stage tumors (volume ≤ 100 mm3) and significant growth inhibition of late-stage tumor (500 mm3) are realized in tumor-bearing mice by transfecting mechanogenetic circuits and treating daily with quantitative robotic actuation in a form of 5 min treatment over the course of 14 days. Thus, this massage-derived therapy represents a quantitative strategy for cancer treatment.

3.
Small ; 20(22): e2308851, 2024 May.
Article in English | MEDLINE | ID: mdl-38112252

ABSTRACT

Vanadium oxides have aroused attention as cathode materials in aqueous zinc-ion batteries (AZIBs) due to their low cost and high safety. However, low ion diffusion and vanadium dissolution often lead to capacity decay and deteriorating stability during cycling. Herein, vanadium dioxides (VO2) nanobelts are coated with a single-atom cobalt dispersed N-doped carbon (Co-N-C) layer via a facile calcination strategy to form Co-N-C layer coated VO2 nanobelts (VO2@Co-N-C NBs) for cathodes in AZIBs. Various in-/ex situ characterizations demonstrate the interfaces between VO2 layers and Co-N-C layers can protect the VO2 NBs from collapsing, increase ion diffusion, and enhance the Zn2+ storage performance. Additional density functional theory (DFT) simulations demonstrate that Co─O─V bonds between VO2 and Co-N-C layers can enhance interfacial Zn2+ storage. Moreover, the VO2@Co-N-C NBs provided an ultrahigh capacity (418.7 mAh g-1 at 1 A g-1), outstanding long-term stability (over 8000 cycles at 20 A g-1), and superior rate performance.

4.
Angew Chem Int Ed Engl ; 62(43): e202304483, 2023 Oct 23.
Article in English | MEDLINE | ID: mdl-37670725

ABSTRACT

Generating strong adhesion by engineered proteins has the potential for high technical applications. Current studies of adhesive proteins are primarily limited to marine organisms, e.g., mussel adhesive proteins. Here, we present a modular engineering strategy to generate a type of exotic protein adhesives with super strong adhesion behaviors. In the protein complexes, the lanmodulin (LanM) underwent α-helical conformational transition induced by lanthanides, thereby enhancing the stacking density and molecular interactions of adhesive protein. The resulting adhesives exhibited outstanding lap-shear strength of ≈31.7 MPa, surpassing many supramolecular and polymer adhesives. The extreme temperature (-196 to 200 °C) resistance capacity and underwater adhesion performance can significantly broaden their practical application scenarios. Ex vivo and in vivo experiments further demonstrated the persistent adhesion performance for surgical sealing and healing applications.

5.
Micromachines (Basel) ; 14(8)2023 Aug 18.
Article in English | MEDLINE | ID: mdl-37630169

ABSTRACT

In this work, we present an analytical model of dynamic power losses for enhancement-mode AlGaN/GaN high-electron-mobility transistor power devices (eGaN HEMTs). To build this new model, the dynamic on-resistance (Rdson) is first accurately extracted via our extraction circuit based on a double-diode isolation (DDI) method using a high operating frequency of up to 1 MHz and a large drain voltage of up to 600 V; thus, the unique problem of an increase in the dynamic Rdson is presented. Then, the impact of the current operation mode on the on/off transition time is evaluated via a dual-pulse-current-mode test (DPCT), including a discontinuous conduction mode (DCM) and a continuous conduction mode (CCM); thus, the transition time is revised for different current modes. Afterward, the discrepancy between the drain current and the real channel current is qualitative investigated using an external shunt capacitance (ESC) method; thus, the losses due to device parasitic capacitance are also taken into account. After these improvements, the dynamic model will be more compatible for eGaN HEMTs. Finally, the dynamic power losses calculated via this model are found to be in good agreement with the experimental results. Based on this model, we propose a superior solution with a quasi-resonant mode (QRM) to achieve lossless switching and accelerated switching speeds.

6.
Micron ; 166: 103402, 2023 Mar.
Article in English | MEDLINE | ID: mdl-36628857

ABSTRACT

Rapid analysis and processing of large quantities of data obtained from in-situ transmission electron microscope (TEM) experiments can save researchers from the burdensome manual analysis work. The method mentioned in this paper combines deep learning and computer vision technology to realize the rapid automatic processing of end-to-end crystal high-resolution transmission electron microscope (HRTEM) images, which has great potential in assisting TEM image analysis. For the fine-grained result, the HRTEM image is divided into multiple patches by sliding window, and 2D fast Fourier transform (FFT) is performed, and then all FFT images are inputted into the designed LCA-Unet to extract bright spots. LCA-Unet combines local contrast and attention mechanism on the basis of U-net. Even if the bright spots in FFT images are weak, the proposed neural network can extract bright spots effectively. Using computer vision and the information of bright spots above mentioned, the automatic FFT pattern recognition is completed by three steps. First step is to calculate the precise coordinates of the bright spots, the lattice spacings and the inter-plane angles in each patch. Second step is to match the lattice spacing and the angles with the powder diffraction file (PDF) to determine the material phase of each patch. Third step is to merge the patches with same phase. Taking the HRTEM image of zirconium and its oxide nanoparticles as an example, the results obtained by the proposed method are basically consistent with manual identification. Thus the approach could be used to automatically and effectively find the phase region of interest. It takes about 3 s to process a 4 K × 4 K HRTEM image on a modern desktop computer with NVIDIA GPU.

7.
Adv Sci (Weinh) ; 10(4): e2206084, 2023 Feb.
Article in English | MEDLINE | ID: mdl-36470654

ABSTRACT

Silicon suboxide (SiOx ) has attracted widespread interest as Li-ion battery (LIB) anodes. However, its undesirable electronic conductivity and apparent volume effect during cycling impede its practical applications. Herein, sustainable rice husks (RHs)-derived SiO2 are chosen as a feedstock to design SiOx /iron-nitrogen co-doped carbon (Fe-N-C) materials. Using a facile electrospray-carbonization strategy, SiOx nanoparticles (NPs) are encapsulated in the nitrogen-doped carbon (N-C) frameworks decorating atomically dispersed iron sites. Systematic characterizations including high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) verify the existence of Fe single atoms and typical coordination environment. Benefiting from its structural and compositional merits, the SiOx /Fe-N-C anode delivers significantly improved discharge capacity of 799.1 mAh g-1 , rate capability, and exceptional durability, compared with pure SiO2 and SiOx /N-C, which has been revealed by the density functional theory (DFT) calculations. Additionally, the electrochemical tests and in situ X-ray diffraction (XRD) analysis reveal the oxidation of Lix Si phase and the storage mechanism. The synthetic strategy is universal for the design and synthesis of metal single atoms/clusters dispersed N-C frameworks encapsulated SiOx NPs. Meanwhile, this work provides impressive insights into developing various LIB anode materials suffering from inferior conductivity and huge volume fluctuations.

8.
Front Pharmacol ; 13: 1023660, 2022.
Article in English | MEDLINE | ID: mdl-36408227

ABSTRACT

Objectives: Tumours remain a serious threat to human life. Following rapid progress in oncology research, tyrosine kinase inhibitors have been used to treat multiple tumour types. Given the great influence of kidneys on pharmacokinetics, renal toxicities associated with TKIs have attracted attention. However, the TKIs with the lowest risks of renal impairment are unclear. In this study, we conducted a Bayesian network meta-analysis to compare the incidence of renal impairment among different TKIs in patients with tumours. Methods and analysis: Six databases (PubMed, EMBASE, The Cochrane Library, Chinese National Knowledge Infrastructure, Wanfang Data, and China Biomedical Literature Database) were electronically searched from inception to 1 November 2021 to identify randomized controlled trials on the incidence of renal impairment for different TKIs in patients with tumours. Two reviewers independently screened the literature, extracted data, and assessed the risk of bias of the included studies. Then, a pairwise meta-analysis was conducted using Stata version 13, and network meta-analysis within the Bayesian framework was conducted using R software version 3.5.3 with the package "gemtc 0.8-2" recalling JAGS (version 4.3.0). Results: Overall, 34 randomized controlled trials were included in this study. Although renal toxicity was common among patients receiving TKIs, the incidence and severity greatly differed among the drugs and studies. Elevated creatinine and protein levels were the most common nephrotoxic events, whereas haematuria was relatively rare. Among TKIs, nintedanib and ripretinib carried the lowest risks of renal impairment. Conclusion: TKIs displayed different profiles of renal toxicity because of their different targets and underlying mechanisms. Clinicians should be aware of the risks of renal impairment to select the optimal treatment and improve patient adherence to treatment. Systematic Review Registration: [www.crd.york.ac.uk/prospero/], identifier [CRD42022295853].

9.
PLoS One ; 17(10): e0275577, 2022.
Article in English | MEDLINE | ID: mdl-36240234

ABSTRACT

This paper investigates the impact of financial Inclusion on household poverty and vulnerability by constructing a household financial inclusion index using the China Household Finance Survey 2015. It is found that financial Inclusion significantly reduces the probability of poverty and vulnerability of households and has a more significant impact on vulnerable groups such as rural and urban low-income people. Further, financial Inclusion has a more significant effect on poor families that do not receive government support for poverty alleviation and can complement co-insurance mechanisms to help families better cope with vulnerabilities caused by synergistic community shocks. Finally, promoting entrepreneurship and improving risk management capabilities are the main channels of financial Inclusion.


Subject(s)
Family Characteristics , Health Expenditures , China , Humans , Poverty , Rural Population
10.
Sci Adv ; 8(31): eabo7415, 2022 Aug 05.
Article in English | MEDLINE | ID: mdl-35930647

ABSTRACT

DNA has attracted increasing interest as an appealing medium for information storage. However, target-specific rewriting of the digital data stored in intracellular DNA remains a grand challenge because the highly repetitive nature and uneven guanine-cytosine content render the encoded DNA sequences poorly compatible with endogenous ones. In this study, a dual-plasmid system based on gene editing tools was introduced into Escherichia coli to process information accurately. Digital data containing large repeat units in binary codes, such as text, codebook, or image, were involved in the realization of target-specific rewriting in vivo, yielding up to 94% rewriting reliability. An optical reporter was introduced as an advanced tool for presenting data processing at the molecular level. Rewritten information was stored stably and amplified over hundreds of generations. Our work demonstrates a digital-to-biological information processing approach for highly efficient data storage, amplification, and rewriting, thus robustly promoting the application of DNA-based information technology.

11.
Chempluschem ; 87(9): e202200183, 2022 Jul 04.
Article in English | MEDLINE | ID: mdl-35856827

ABSTRACT

The exponential growth of the total amount of global data presents a huge challenge to mainstream storage media. The emergence of molecular digital storage inspires the development of the new-generation higher-density digital data storage. In particular, DNA with high storage density, reproducibility, and long recoverable lifetime behaves the ideal representative of molecular digital storage media. With the development of DNA synthesis and sequencing technologies and the reduction of cost, DNA digital storage has attracted more and more attention and achieved significant breakthroughs. Herein, this Review briefly describes the workflow of DNA storage, and highlights the storage step of DNA digital data storage. Then, according to different information storage forms, the current DNA information encryption methods are emphatically expounded. Finally, the brief perspectives on the current challenges and optimizing proposals in DNA information preservation and encryption are presented.

12.
Angew Chem Int Ed Engl ; 61(11): e202111630, 2022 03 07.
Article in English | MEDLINE | ID: mdl-35224847

ABSTRACT

Developing a novel tool capable of real-time monitoring and simultaneous quantitation of multiple molecules in mitochondria across the whole brain of freely moving animals is the key bottleneck for understanding the physiological and pathological roles that mitochondria play in the brain events. Here we built a Raman fiber photometry, and created a highly selective non-metallic Raman probe based on the triple-recognition strategies of chemical reaction, charge transfer, and characteristic fingerprint peaks, for tracking and simultaneous quantitation of mitochondrial O2.- , Ca2+ and pH at the same location in six brain regions of free-moving animal upon hypoxia. It was found that mitochondrial O2.- , Ca2+ and pH changed from superficial to deep brain regions upon hypoxia. It was discovered that hypoxia-induced mitochondrial O2.- burst was regulated by ASIC1a, leading to mitochondrial Ca2+ overload and acidification. Furthermore, we found the overload of mitochondrial Ca2+ was mostly attributed to the influx of extracellular Ca2+ .


Subject(s)
Behavior, Animal/physiology , Brain/metabolism , Calcium/metabolism , Mitochondria/metabolism , Superoxides/metabolism , Animals , Hypoxia , Ions/metabolism , Mice , Spectrum Analysis, Raman
13.
Phys Chem Chem Phys ; 23(45): 25455-25466, 2021 Nov 24.
Article in English | MEDLINE | ID: mdl-34818402

ABSTRACT

When organic electron donor (D) and acceptor (A) chromophores are linked together, an electron transfer (ET) state can take place. When a short bridge such as one Sigma bond is used to link the donor and the acceptor, complete charge separation is difficult to access and one usually observes an intramolecular charge transfer (CT) state instead. Due to the inevitable coupling between the donor and the acceptor in compact organic chromophores, the most common decay pathway for the CT state is charge recombination, which may lead to a distinct longer wavelength fluorescence emission or non-radiative dissipation of the excited state energy. However, recent studies have shown that unique excited state dynamics can be observed when the CT state is involved during both forward and backward intersystem crossing (ISC) from singlet excited states to triplet excited states in organic chromophores. Analysis of the mechanism for ISC involving the CT state has received much attention over the last decade. In this perspective, we present a collection of molecular design rationales, spectroscopy and theoretical investigations that provide insights into the mechanism of the ISC involving the CT state in compact organic chromophores. We hope that this perspective will prove beneficial for researchers to design novel compact organic chromophores with a predictable ISC property for future biochemical and optoelectronic applications.

14.
Nat Commun ; 12(1): 1532, 2021 03 09.
Article in English | MEDLINE | ID: mdl-33750766

ABSTRACT

Conventional wisdom posits that spin-triplet energy transfer (TET) is only operative over short distances because Dexter-type electronic coupling for TET rapidly decreases with increasing donor acceptor separation. While coherent mechanisms such as super-exchange can enhance the magnitude of electronic coupling, they are equally attenuated with distance. Here, we report endothermic charge-transfer-mediated TET as an alternative mechanism featuring shallow distance-dependence and experimentally demonstrated it using a linked nanocrystal-polyacene donor acceptor pair. Donor-acceptor electronic coupling is quantitatively controlled through wavefunction leakage out of the core/shell semiconductor nanocrystals, while the charge/energy transfer driving force is conserved. Attenuation of the TET rate as a function of shell thickness clearly follows the trend of hole probability density on nanocrystal surfaces rather than the product of electron and hole densities, consistent with endothermic hole-transfer-mediated TET. The shallow distance-dependence afforded by this mechanism enables efficient TET across distances well beyond the nominal range of Dexter or super-exchange paradigms.

15.
Phys Chem Chem Phys ; 22(35): 19903-19912, 2020 Sep 21.
Article in English | MEDLINE | ID: mdl-32853308

ABSTRACT

Biliverdin is a bile pigment that has a very low fluorescence quantum yield in solution, but serves as a chromophore in far-red fluorescent proteins being developed for bio-imaging. In this work, excited-state dynamics of biliverdin dimethyl ether (BVE) in solvents were investigated using femtosecond (fs) and picosecond (ps) time-resolved absorption and fluorescence spectroscopy. This study is the first fs timescale investigation of BVE in solvents, and therefore revealed numerous dynamics that were not resolved in previous, 200 ps time resolution measurements. Viscosity- and isotope-dependent experiments were performed to identify the contributions of isomerization and proton transfer to the excited-state dynamics. In aprotic solvents, a ∼2 ps non-radiative decay accounts for 95% of the excited-state population loss. In addition, a minor ∼30 ps emissive decay pathway is likely associated with an incomplete isomerization process around the C15[double bond, length as m-dash]C16 double bond that results in a flip of the D-ring. In protic solvents, the dynamics are more complex due to hydrogen bond interactions between solute and solvent. In this case, the ∼2 ps decay pathway is a minor channel (15%), whereas ∼70% of the excited-state population decays through an 800 fs emissive pathway. The ∼30 ps timescale associated with isomerization is also observed in protic solvents. The most significant difference in protic solvents is the presence of a >300 ps timescale in which BVE can decay through an emissive state, in parallel with excited-state proton transfer to the solvent. Interestingly, a small fraction of a luminous species, which we designate lumin-BVE (LBVE), is present in protic solvents.


Subject(s)
Biliverdine/analogs & derivatives , Esters/chemistry , Hydrogen Bonding , Isomerism , Molecular Structure , Protons , Solvents/chemistry , Spectrometry, Fluorescence
16.
J Phys Chem B ; 124(31): 6721-6727, 2020 08 06.
Article in English | MEDLINE | ID: mdl-32660250

ABSTRACT

The fluorescence of dinucleotide NADH has been exploited for decades to determine the redox state of cells and tissues in vivo and in vitro. Particularly, nanosecond (ns) fluorescence lifetime imaging microscopy (FLIM) of NADH (in free vs bound forms) has recently offered a label-free readout of mitochondrial function and allowed the different "pools" of NADH to be distinguished in living cells. In this study, the ultrafast fluorescence dynamics of NADH-dehydrogenase (MDH/LDH) complexes have been investigated by using both a femtosecond (fs) upconversion spectrophotofluorometer and a picosecond (ps) time-correlated single photon counting (TCSPC) apparatus. With these enhanced time-resolved tools, a few-picosecond decay process with a signatory spectrum was indeed found for bound NADH, and it can best be ascribed to the solvent relaxation originating in "bulk water". However, it is quite unlike our previously discovered ultrafast "dark" component (∼26 ps) that is prominent in free NADH (Chemical Physics Letters 2019, 726, 18-21). For these two critical protein-bound NADH exemplars, the decay transients lack the ultrafast quenching that creates the "dark" subpopulation of free NADH. Therefore, we infer that the apparent ratio of free to bound NADH recovered by ordinary (>50 ps) FLIM methods may be low, since the "dark" molecule subpopulation (lifetime too short for conventional FLIM), which effectively hides about a quarter of free molecules, is not present in the dehydrogenase-bound state.


Subject(s)
Dinucleoside Phosphates , NAD , Binding Sites , Microscopy, Fluorescence , Oxidoreductases
17.
Mol Genet Genomics ; 295(5): 1269-1279, 2020 Sep.
Article in English | MEDLINE | ID: mdl-32561986

ABSTRACT

Aspergillus nidulans nrtA encodes a nitrate transporter that plays an important role in the [Formula: see text] assimilatory process. Many studies have focused on protein functions rather than gene regulation. The knowledge of nrtA[Formula: see text] uptake process, particularly in the regulation mechanism of transcription factors AreA and NirA on nrtA transcription, is very limited. Herein, we investigated the transcriptional regulation of nrtA in response to various N-sources in detail and characterized the promoter activity of nrtA. We confirmed that nrtA was induced by [Formula: see text] and repressed by preferred N-sources. Additionally, for the first time, we found that the transcription of nrtA increased under N-starvation conditions. AreA mediates nrtA transcription under both [Formula: see text] and N-starvation conditions, while NirA is effective only under [Formula: see text] conditions. All of the proposed AreA and NirA binding sites in the promoter region were capable of binding to their corresponding transcription factors in vitro. In vivo, all of the NirA binding sites showed regulation activities, but to AreA, only several of the initiation-codon-proximal binding sites participated in nrtA transcription. Moreover, the active binding sites contributed in different degrees of regulation strength to nrtA transcription, which is unrelated to the distance between the binding sites and initiation codon. These results provided an extensive map of nrtA promoter, defining the functional regulatory elements of A. nidulans nrtA.


Subject(s)
Anion Transport Proteins/genetics , Anion Transport Proteins/metabolism , Aspergillus nidulans/metabolism , Fungal Proteins/genetics , Fungal Proteins/metabolism , Nitrates/metabolism , Anion Transport Proteins/chemistry , Aspergillus nidulans/genetics , Binding Sites , Fungal Proteins/chemistry , Gene Expression Regulation, Fungal , Promoter Regions, Genetic , Transcription Factors/metabolism
18.
J Hazard Mater ; 395: 122692, 2020 Aug 05.
Article in English | MEDLINE | ID: mdl-32330785

ABSTRACT

Capturing uranium (U(VI)) ions from wastewater and seawater is highly attractive for the environment and clean energy with the increasing deficiency of land sources. Howbeit, the massive volume of water and the ultralow concentration of U(VI) pose a substantial challenge to the industrial application. Accordingly, we have synthesized a novel organic-inorganic hybrid adsorbent through in-situ growing MOF particles on electrospun polyacrylonitrile fibers (PAN) followed by modifing with amidoxime groups to form amidoximed PAN/ZIF-67 (AOPAN/ZIF) hybrid fibers. In such fibers, the N atoms from imidazole and amidoxime can improve the adsorption performance synergistically in a wide pH range, which is favorable for capturing U(VI) under nuclear wastewater and seawater. As a result, the AOPAN/ZIF fibers exhibit high adsorption amount of 498.4 mg g-1 in U(VI) contaminated aqueous solution at pH 4. Furthermore, the adsorption amount of U(VI) reached 2.03 mg g-1 in natural seawater after 36 d, which implies that the AOPAN/ZIF fibers may promote the development of U(VI) recovery.

19.
IEEE J Biomed Health Inform ; 24(9): 2473-2480, 2020 09.
Article in English | MEDLINE | ID: mdl-32011271

ABSTRACT

The object detection, which has been widely applied in the biomedical field already, is of real significance but technically challenging. In practice, the object detection accuracy is vulnerable to labeling quality, which is usually not a big headache for simple algorithm or model verification since there are a bunch of ideal public available datasets whose classes and tags are all well-marked. However, in real scenarios, image data is often partially or even incorrectly labeled. Particularly, in cell detection, this becomes a thorny issue since the labelling of the dataset is incomplete and inaccurate. To address this issue, we propose a data-augmentation algorithm that can generate full labeled cell image data from incomplete labeled ones. First of all, we randomly extract the labeled objects from raw cell images, and meanwhile, keep their corresponding position information. Next, we employ the framework of cycle-consistent adversarial network, but significantly distinguished from the original one, to generate fully labeled data including both objects and backgrounds. We conduct extensive experiments on a blood cell classification dataset called BCCD to evaluate our model, and experimental results show that our proposed method can successfully address the weak annotation problem and improve the performance of object detection.


Subject(s)
Algorithms , Image Processing, Computer-Assisted
20.
J Phys Chem B ; 124(5): 771-776, 2020 02 06.
Article in English | MEDLINE | ID: mdl-31941277

ABSTRACT

The ultrafast solvation dynamics of reduced nicotinamide adenine dinucleotide (NADH) free in solution has been investigated, using both a femtosecond upconversion spectrophotofluorometer and a picosecond time-correlated single-photon counting (TCSPC) apparatus. The familiar time constant of solvent relaxation originating in "bulk water" was found to be ∼1.4 ps, revealing ultrafast solvent reorientation upon excitation. We also found a slower spectral relaxation process with an apparent time of 27 ps, suggesting there could either be dissociable "biological water" hydration sites on the surface of NADH or internal dielectric rearrangements of the flexible solvated molecule on that timescale. In contrast, the femtosecond fluorescence anisotropy measurement revealed that rotational diffusion happened on two different timescales (3.6 ps (local) and 141 ps (tumbling)); thus, any dielectric rearrangement scenario for the 27 ps relaxation must occur without significant chromophore oscillator rotation. The coexistence of quasi-static self quenching (QSSQ) with the slower relaxation is also discussed.


Subject(s)
NAD/chemistry , Water/chemistry , Solvents/chemistry , Spectrometry, Fluorescence
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