β-Crystallins are the major structural proteins existing in the vertebrate lens, and their conformational stability is critical in maintaining the life-long transparency and refraction index of the lens. Seven subuni...β-Crystallins are the major structural proteins existing in the vertebrate lens, and their conformational stability is critical in maintaining the life-long transparency and refraction index of the lens. Seven subunits of β-crystallins naturally assemble into various heteroge- neous oligomers with different sizes. Here, we systematically investigated the thermal sta- bility of the different secondary structures present in β-Crystallins and then the dynamic process for the thermal-induced unfolding of β-crystallins by Fourier transform infrared spectroscopy-monitored thermal titration and temperature-jump nanosecond time-resolved IR difference absorbance spectra. Our results show that the N-terminal anti-parallel β-sheets in β-crystallin are the most unstable with a transition midpoint temperature at 36.0-2.1℃, leading to the formation of an intermediate consisting vastly of random coil structures. This intermediate structure is temporally assigned to that of the monomer generated by the thermal-induced disassembly of β-crystallin oligomers with a transition midpoint tempera- ture of 40.4-0.7℃. The global unfolding of β-crystallins that leads to denaturation and aggregation indicated by the formation of intermolecular anti-parallel β-sheets has a transi- tion midpoint temperature determined as 72.4-0.2 ℃. Temperature-jump time-resolved IR absorbance difference spectroscopy analysis further reveals that thermal-induced unfolding of β-crystallins occurs firstly in the anti-parallel β-sheets in the N-terminal domains with a time constant of 50 ns.展开更多
We proposed a novel relative humidity （RH） sensor based on the air guided photonic crystal fiber （AGPCF） using the direct absorption spectroscopic method in this paper. The wavelength scanning around the water vap...We proposed a novel relative humidity （RH） sensor based on the air guided photonic crystal fiber （AGPCF） using the direct absorption spectroscopic method in this paper. The wavelength scanning around the water vapor absorption peak around 1368.59nm was realized by injecting the saw-tooth modulated current to a distributed-feedback laser diode. A reference signal was used as a zero absorption baseline and to help reduce the interference from the distributed-feedback laser source and probed region. The humidity level was determined by the normalized voltage difference between the reference signal and sensor signal at the peak of water vapor absorption. We demonstrated that a length of 5-cm AGPCF with a fixed small air gap between the single mode fiber （SMF） and hollow core fiber as an opening achieved a humidity detection resolution of around 0.2%RH over the range 0 to 90%RH which did not require the use of any hygroscopic coating material.展开更多
Three bis-vinylpyridine compounds (4,4′-bis(2-vinylpyridine)biphenyl L1,4,4′-bis(3-vinylpyridine) biphenyl L2,and 4,4′-bis (4-vinylpyridine)biphenyl L3) were synthesized by one-step solid-state reactions at room te...Three bis-vinylpyridine compounds (4,4′-bis(2-vinylpyridine)biphenyl L1,4,4′-bis(3-vinylpyridine) biphenyl L2,and 4,4′-bis (4-vinylpyridine)biphenyl L3) were synthesized by one-step solid-state reactions at room temperature,giving nearly quantitative yields. The compounds obtained were fully characterized by IR,MS and NMR spectroscopies. The structures of L2 and L3 were determined by single crystal X-ray diffraction analysis. No noticeable solvatochromism was observed in either one-photon absorption or one-photon excited fluorescence spectra. All of the compounds have high fluorescence quantum yields and long fluorescence lifetime. The linear and nonlinear optical properties of the compounds were investigated both experimentally and theoretically. Interestingly,the position of the nitrogen atom from pyridine influences their two-photon absorption across-sections.展开更多
Tm^(3+) doped Na_5Lu_9F_(32) single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters ?_t(t=2, 4, 6) were calculated according to the measured absorption s...Tm^(3+) doped Na_5Lu_9F_(32) single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters ?_t(t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na_5Lu_9F_(32) single crystal. The stimulated emission cross-section of the ~3F_4→~3H_6 transition(～1.8 μm) is 0.35×10^(-20) cm^2 for Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The emission spectra under the excitation of 790 nm laser diode(LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The research results show that the Tm^(3+) doped Na_5Lu_9F_(32) single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm^(3+)doped Na_5Lu_9F_(32) crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.展开更多
文摘β-Crystallins are the major structural proteins existing in the vertebrate lens, and their conformational stability is critical in maintaining the life-long transparency and refraction index of the lens. Seven subunits of β-crystallins naturally assemble into various heteroge- neous oligomers with different sizes. Here, we systematically investigated the thermal sta- bility of the different secondary structures present in β-Crystallins and then the dynamic process for the thermal-induced unfolding of β-crystallins by Fourier transform infrared spectroscopy-monitored thermal titration and temperature-jump nanosecond time-resolved IR difference absorbance spectra. Our results show that the N-terminal anti-parallel β-sheets in β-crystallin are the most unstable with a transition midpoint temperature at 36.0-2.1℃, leading to the formation of an intermediate consisting vastly of random coil structures. This intermediate structure is temporally assigned to that of the monomer generated by the thermal-induced disassembly of β-crystallin oligomers with a transition midpoint tempera- ture of 40.4-0.7℃. The global unfolding of β-crystallins that leads to denaturation and aggregation indicated by the formation of intermolecular anti-parallel β-sheets has a transi- tion midpoint temperature determined as 72.4-0.2 ℃. Temperature-jump time-resolved IR absorbance difference spectroscopy analysis further reveals that thermal-induced unfolding of β-crystallins occurs firstly in the anti-parallel β-sheets in the N-terminal domains with a time constant of 50 ns.
文摘We proposed a novel relative humidity （RH） sensor based on the air guided photonic crystal fiber （AGPCF） using the direct absorption spectroscopic method in this paper. The wavelength scanning around the water vapor absorption peak around 1368.59nm was realized by injecting the saw-tooth modulated current to a distributed-feedback laser diode. A reference signal was used as a zero absorption baseline and to help reduce the interference from the distributed-feedback laser source and probed region. The humidity level was determined by the normalized voltage difference between the reference signal and sensor signal at the peak of water vapor absorption. We demonstrated that a length of 5-cm AGPCF with a fixed small air gap between the single mode fiber （SMF） and hollow core fiber as an opening achieved a humidity detection resolution of around 0.2%RH over the range 0 to 90%RH which did not require the use of any hygroscopic coating material.
基金supported by a grant for the National Natural Science Foundation of China (20771001, 50703001, 50873001)Department of Education of Anhui Province (KJ2010A030)+1 种基金Team for Scientific Innovation Foundation of Anhui Province (2006KJ007TD)Key Laboratory of Opto-Electronic Information Acquisition and Manipulation (Anhui University)
文摘Three bis-vinylpyridine compounds (4,4′-bis(2-vinylpyridine)biphenyl L1,4,4′-bis(3-vinylpyridine) biphenyl L2,and 4,4′-bis (4-vinylpyridine)biphenyl L3) were synthesized by one-step solid-state reactions at room temperature,giving nearly quantitative yields. The compounds obtained were fully characterized by IR,MS and NMR spectroscopies. The structures of L2 and L3 were determined by single crystal X-ray diffraction analysis. No noticeable solvatochromism was observed in either one-photon absorption or one-photon excited fluorescence spectra. All of the compounds have high fluorescence quantum yields and long fluorescence lifetime. The linear and nonlinear optical properties of the compounds were investigated both experimentally and theoretically. Interestingly,the position of the nitrogen atom from pyridine influences their two-photon absorption across-sections.
基金supported by the National Natural Science Foundation of China(Nos.51472125 and 51272109)the Natural Science Foundation of Zhejiang Province(No.LZ17E020001)K.C. Wong Magna Fund in Ningbo University
文摘Tm^(3+) doped Na_5Lu_9F_(32) single crystal with high optical quality was grown by an improved Bridgman method. The Judd-Ofelt intensity parameters ?_t(t=2, 4, 6) were calculated according to the measured absorption spectra and physical-chemical properties of the obtained Na_5Lu_9F_(32) single crystal. The stimulated emission cross-section of the ~3F_4→~3H_6 transition(～1.8 μm) is 0.35×10^(-20) cm^2 for Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The emission spectra under the excitation of 790 nm laser diode(LD) and fluorescence lifetime at 1.8 μm were measured to reveal the fluorescence properties of Tm^(3+) doped Na_5Lu_9F_(32) single crystal. The research results show that the Tm^(3+) doped Na_5Lu_9F_(32) single crystal has larger stimulated emission cross-section compared with other crystals. All these spectral properties suggest that this kind of Tm^(3+)doped Na_5Lu_9F_(32) crystal with high physical-chemical stability and high-efficiency emission at 1.8 μm may be used as potential laser materials for optical devices.
