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As a typical transition metal oxide, α‐Fe2O3 has garnered significant attention due to its advantages in nonlinear optical applications, such as strong third‐order nonlinearity and fast carrier recovery time. To delve into the nonlinear optical properties of α‐Fe2O3, crystalline α‐Fe2O3 materials with different microstructures are prepared. The nonlinear optical features of α‐Fe2O3 calcined at the previously unexplored ultra‐high temperature of >1100°C are emphasized. It is found that α‐Fe2O3 exposed to ultra‐high temperatures undergoes the phase transition, leading to the formation of Fe3O4. Subsequently, the nonlinear absorption coefficient is measured as −0.6280 cm GW−1 at 1.5 µm. The modulation depth and saturation intensity for the Fe2O3‐based saturable absorber at 1.5 µm are 4.20% and 13.94 MW cm−2, respectively. Ultimately, the incorporation of the Fe2O3‐based saturable absorber into an Er‐doped fiber laser cavity resulted in the achievement of both conventional soliton mode‐locking operation with a central wavelength of 1560.3 nm and a pulse duration of 1.13 ps, as well as the dissipative soliton resonance mode‐locking operation with a central wavelength near 1564.0 nm. Overall, the phase transition and the nonlinear optical features in iron oxides under ultra‐high temperatures are revealed, indicating the great potential in advanced ultrafast photonic applications. This study focuses on exploring the nonlinear optical properties of α‐Fe2O3 material calcined at ultra‐high temperatures. It is discovered that the α‐Fe2O3 material underwent the phase transition at ultra‐high temperatures. Then, the α‐Fe2O3 material calcined at 1100 °C is successfully integrated as a saturable absorber into an erbium‐doped fiber laser, achieving conventional soliton mode‐locking operation and dissipative soliton resonance mode‐locking operation within the C‐band.

Bi Se, with its excellent air stability, high mobility, and tunable bandgap, shows great potential for photonic modulators. This study proposes vacancy engineering as an effective method to refine its optical properties and enhance the nonlinear response. The optical properties of Bi Se modified by oxygen vacancy defects were systematically investigated through theoretical simulations and experimental methods. Oxygen vacancies enhance photon–material interactions by introducing intermediate energy levels, altering the electronic structure, reducing the bandgap, inducing a redshift in the linear absorption spectrum, and forming a new absorption band near 1 μm. Argon annealing increased the concentration of oxygen vacancies, and the experimental absorption spectra showed excellent agreement with theoretical predictions. To evaluate the impact of oxygen vacancies on the nonlinear optical response, Bi Se before and after annealing was employed as a saturable absorber in Q-switched and mode-locked lasers. The annealed Bi Se exhibited a 4.42-fold increase in peak power, a 115.9 fs reduction in pulse width, and a 2.36 nm expansion in 3 dB spectral width. These findings indicate that vacancy engineering is a direct and effective strategy for optimizing the nonlinear optical properties of Bi Se, which can contribute to advanced photon applications.

Doping generally introduces performance trade‐offs in materials, yet overcoming this fundamental limitation remains crucial for advancing materials research. Bi 2 O 2 Se exhibits exceptional electronic properties as a promising semiconductor, yet its nonlinear optical response under low excitation intensities hinders its practical applications. Therefore, precise Sb 3 ⁺ doping in Bi 2 O 2 Se (Bi 1.9 Sb 0.1 O 2 Se) is achieved for the first time via solid‐state reaction and systematically studies its impact on the electronic structure and optical properties through first‐principles calculations and experimental. The results reveal that Sb 3 ⁺ substitution slightly reduces the bandgap without introducing defect states, and transient absorption spectroscopy further confirms prolonged carrier relaxation. At 1.5 µm, the modulation depth from 8.8% to 10.1% while dramatically reducing the saturation intensity from 47.2 to 0.53 kW cm − 2 . This improvement is attributed to the stable linear absorption characteristics after doping, the synergistic effect between prolonged relaxation time and free‐carrier‐induced optical loss. In a mode‐locking system, Bi 1.9 Sb 0.1 O 2 Se achieves a broader 3‐dB and shorter pulse duration at substantially reduced pump intensities. This work achieves defect‐free energy level optimization in Sb‐doped Bi 2 O 2 Se, where the material's high carrier mobility is not only preserved but further enhanced, while the saturation intensity is declined by about two orders of magnitude, enabling a low‐power, high‐performance nonlinear photonic devices.

Doping generally introduces performance trade-offs in materials, yet overcoming this fundamental limitation remains crucial for advancing materials research. Bi2O2Se exhibits exceptional electronic properties as a promising semiconductor, yet its nonlinear optical response under low excitation intensities hinders its practical applications. Therefore, precise Sb3⁺ doping in Bi2O2Se (Bi1.9Sb0.1O2Se) is achieved for the first time via solid-state reaction and systematically studies its impact on the electronic structure and optical properties through first-principles calculations and experimental. The results reveal that Sb3⁺ substitution slightly reduces the bandgap without introducing defect states, and transient absorption spectroscopy further confirms prolonged carrier relaxation. At 1.5 µm, the modulation depth from 8.8% to 10.1% while dramatically reducing the saturation intensity from 47.2 to 0.53 kW cm- 2. This improvement is attributed to the stable linear absorption characteristics after doping, the synergistic effect between prolonged relaxation time and free-carrier-induced optical loss. In a mode-locking system, Bi1.9Sb0.1O2Se achieves a broader 3-dB and shorter pulse duration at substantially reduced pump intensities. This work achieves defect-free energy level optimization in Sb-doped Bi2O2Se, where the material's high carrier mobility is not only preserved but further enhanced, while the saturation intensity is declined by about two orders of magnitude, enabling a low-power, high-performance nonlinear photonic devices.Doping generally introduces performance trade-offs in materials, yet overcoming this fundamental limitation remains crucial for advancing materials research. Bi2O2Se exhibits exceptional electronic properties as a promising semiconductor, yet its nonlinear optical response under low excitation intensities hinders its practical applications. Therefore, precise Sb3⁺ doping in Bi2O2Se (Bi1.9Sb0.1O2Se) is achieved for the first time via solid-state reaction and systematically studies its impact on the electronic structure and optical properties through first-principles calculations and experimental. The results reveal that Sb3⁺ substitution slightly reduces the bandgap without introducing defect states, and transient absorption spectroscopy further confirms prolonged carrier relaxation. At 1.5 µm, the modulation depth from 8.8% to 10.1% while dramatically reducing the saturation intensity from 47.2 to 0.53 kW cm- 2. This improvement is attributed to the stable linear absorption characteristics after doping, the synergistic effect between prolonged relaxation time and free-carrier-induced optical loss. In a mode-locking system, Bi1.9Sb0.1O2Se achieves a broader 3-dB and shorter pulse duration at substantially reduced pump intensities. This work achieves defect-free energy level optimization in Sb-doped Bi2O2Se, where the material's high carrier mobility is not only preserved but further enhanced, while the saturation intensity is declined by about two orders of magnitude, enabling a low-power, high-performance nonlinear photonic devices.

As a typical transition metal oxide, α‐Fe 2 O 3 has garnered significant attention due to its advantages in nonlinear optical applications, such as strong third‐order nonlinearity and fast carrier recovery time. To delve into the nonlinear optical properties of α‐Fe 2 O 3 , crystalline α‐Fe 2 O 3 materials with different microstructures are prepared. The nonlinear optical features of α‐Fe 2 O 3 calcined at the previously unexplored ultra‐high temperature of >1100°C are emphasized. It is found that α‐Fe 2 O 3 exposed to ultra‐high temperatures undergoes the phase transition, leading to the formation of Fe 3 O 4 . Subsequently, the nonlinear absorption coefficient is measured as −0.6280 cm GW −1 at 1.5 µm. The modulation depth and saturation intensity for the Fe 2 O 3 ‐based saturable absorber at 1.5 µm are 4.20% and 13.94 MW cm −2 , respectively. Ultimately, the incorporation of the Fe 2 O 3 ‐based saturable absorber into an Er‐doped fiber laser cavity resulted in the achievement of both conventional soliton mode‐locking operation with a central wavelength of 1560.3 nm and a pulse duration of 1.13 ps, as well as the dissipative soliton resonance mode‐locking operation with a central wavelength near 1564.0 nm. Overall, the phase transition and the nonlinear optical features in iron oxides under ultra‐high temperatures are revealed, indicating the great potential in advanced ultrafast photonic applications.

Bi 2 O 2 Se, with its excellent air stability, high mobility, and tunable bandgap, shows great potential for photonic modulators. This study proposes vacancy engineering as an effective method to refine its optical properties and enhance the nonlinear response. The optical properties of Bi 2 O 2 Se modified by oxygen vacancy defects were systematically investigated through theoretical simulations and experimental methods. Oxygen vacancies enhance photon–material interactions by introducing intermediate energy levels, altering the electronic structure, reducing the bandgap, inducing a redshift in the linear absorption spectrum, and forming a new absorption band near 1 μm. Argon annealing increased the concentration of oxygen vacancies, and the experimental absorption spectra showed excellent agreement with theoretical predictions. To evaluate the impact of oxygen vacancies on the nonlinear optical response, Bi 2 O 2 Se before and after annealing was employed as a saturable absorber in Q-switched and mode-locked lasers. The annealed Bi 2 O 2 Se exhibited a 4.42-fold increase in peak power, a 115.9 fs reduction in pulse width, and a 2.36 nm expansion in 3 dB spectral width. These findings indicate that vacancy engineering is a direct and effective strategy for optimizing the nonlinear optical properties of Bi 2 O 2 Se, which can contribute to advanced photon applications.

Development of drugs that allosterically regulate enzyme functions to treat disease is a costly venture. Amino acid susbstitutions that mimic allosteric effectors in vitro will identify therapeutic regulatory targets enhancing the likelihood of developing a disease treatment at a reasonable cost. We demonstrate the potential of this approach utilizing human liver pyruvate kinase (hLPYK) as a model. Inhibition of hLPYK was the first desired outcome of this study. We identified individual point mutations that: 1) mimicked allosteric inhibition by alanine, 2) mimicked inhibition by protein phosphorylation, and 3) prevented binding of fructose-1,6-bisphosphate (Fru-1,6-BP). Our second desired outcome was activation of hLPYK. We identified individual point mutations that: 1) prevented hLPYK from binding alanine, the allosteric inhibitor, 2) prevented inhibitory protein phosphorylation, or 3) mimicked allosteric activation by Fru-1,6-BP. Combining the three activating point mutations produced a constitutively activated enzyme that was unresponsive to regulators. Expression of a mutant hLPYK transgene containing these three mutations in a mouse model was not lethal. Thus, mutational mimics of allosteric effectors will be useful to confirm whether allosteric activation of hLPYK will control glycolytic flux in the diabetic liver to reduce hepatic glucose production and, in turn, reduce or prevent hyperglycemia.

Understanding how each residue position contributes to protein function has been a long-standing goal in protein science. Substitution studies have historically focused on conserved protein positions. However, substitutions of nonconserved positions can also modify function. Indeed, we recently identified nonconserved positions that have large substitution effects in human liver pyruvate kinase (hLPYK), including altered allosteric coupling. To facilitate a comparison of which characteristics determine when a nonconserved position does vs. does not contribute to function, the goal of the current work was to identify neutral positions in hLPYK. However, existing hLPYK data showed that three features commonly associated with neutral positions – high sequence entropy, high surface exposure, and alanine scanning – lacked the sensitivity needed to guide experimental studies. We used multiple evolutionary patterns identified in a sequence alignment of the PYK family to identify which positions were least patterned, reasoning that these were most likely to be neutral. Nine positions were tested with a total of 117 amino acid substitutions. Although exploring all potential functions is not feasible for any protein, five parameters associated with substrate/effector affinities and allosteric coupling were measured for hLPYK variants. For each position, the aggregate functional outcomes of all variants were used to quantify a “neutrality” score. Three positions showed perfect neutral scores for all five parameters. Furthermore, the nine positions showed larger neutral scores than 17 positions located near allosteric binding sites. Thus, our strategy successfully enriched the dataset for positions with neutral and modest substitutions.

We present a more accurate method for the quantification of superoxide anion （02-） and hydrogen peroxide （H202） simulta- neously in human HepG2 cell extracts. After the xanthine/xanthine oxidase system was added into cell extract which was devoid of O2＊- and H202, steady-state and in-situ produced O2＊- and H202 by xanthine/xanthine oxidase system was labeled by fluorescent probes and subsequently separated by microchip electrophoresis. Based on this method, two differential equations with the calibration coefficients were established for O2 and H202, respectively. Using the established dual-calibration coefficients, we obtained the calibrated concentrations of 02＊ and H202 that produced in human HepG2 cells, which were lower （0.66±0.03 and 0.82±0.04 lamol/L for 02＊-and H202, respectively） than that （0.85±0.03 and 0.96±0.03 gmol/L for O. and H202, respectively） obtained from statutory working curve. The proposed dual-calibration coefficient protocol takes into account both the complex matrix effect of the biological system and real time decaying of O2 ＊- and H202, providing a method with higher accuracy.

In the goal of interpreting human exomes, when predictive programs assign functional importance to some positions, they implicitly assume the existence of non-important positions: those that accommodate many side chain chemistries without altering function (neutral). However, very few (if any) experimental studies have demonstrated the existence of neutral positions. We sought experimental evidence for neutral positions using human liver pyruvate kinase (hLPYK) as a model system. To that end, we used multiple evolutionary criteria to identify 20 possibly neutral positions. Nine positions were further tested with a total of 117 amino acid substitutions. Although all potential hLPYK functions can never be explored, we measured effects on 5 parameters associated with substrate/ligand affinities and allosteric coupling. At each position, the aggregate outcomes of multiple variants were used to quantify neutrality scores. Three of the nine positions showed perfect neutral scores in all 5 parameters; a fourth position had high neutral scores. Although our strategy for predicting positions had low predictive power for the identification of neutral positions, all positions had neutral scores that were much higher than positions in functional sites. Given this evidence for the existence of neutral positions, similar studies should be carried out for other proteins to generate a database of well characterized neutral positions that can then be available to benchmark and validate predictions about amino acid substitutions.