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A simple and effective method, using calcium nitrate and triammonium phosphate as starting materials, for the preparation of water-dispersible hydroxyapatite nanorods (HAp) was reported. The process primarily involves the preparation of HAp with the addition of sodium citrate (NaC) and the exchange of absorbed ions (NaC) with sodium hexame taphosphate (NaP). The end products were investigated using various means in order to confirm the particles’ crystal phase and morphology and to understand how to improve their stability. The results demonstrate that the resulting HAp at 90 °C is rod-like with length of 300-400 nm and width of 40-60 nm. The zeta potential values of pure HAp, HAp-NaC, HAp-NaC/NaP are from −15.20, −30.89 to −44.84 mV. The settling time test shows the HAp-NaC/NaP could keep stable above 7 months without any creaming or visible sedimentation. The amount of NaC and the reaction temperature play significant roles in the whole process due to the formation of Ca containing precipitates.  相似文献
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This paper describes a novel process for preparing Gelatin coated hydroxyapatite (HAp) nanorods to improve the stability of its aqueous colloid. As Gelatin is a typical protein with abundant hydroxyls, carboxys and imines, it is a very effective functional group to attach onto the surfaces of the HAp particles. Our data show that the Gelatin layer firmly coated on the hydroxyapatite nanorods, and their structure and interfacial chemical bonding have been studied using various techniques, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HRTEM), differential thermal analysis (DTA) and thermal gravimetric analysis (TGA). The reaction temperature, pH, amount of Gelatin, and Ca/P molar ratio in the material determine the quality of Gelatin coating and the stability of the HAp in aqueous solution. Moreover, an interesting phenomenon was found that the Gelatin coated HAp sediment separated by centrifugal was easily dispersed in water and forms HAp aqueous suspension. The suspension was stable for more than 24 h.  相似文献
3.
Characterization of conformation kinetics of proteins at the interfaces is crucial for understanding the biomolecular functions and the mechanisms of interfacial biological action. But it requires to capture the dynamic structures of proteins at the interfaces with sufficient structural and temporal resolutions. Here, we demonstrate that a femtosecond sum frequency generation vibrational spectroscopy (SFG-VS) system developed by our group provides a powerful tool for monitoring the real-time peptide transport across the membranes with time resolution of less than one second. By probing the real-time SFG signals in the amide I and amide A bands as WALP23 interacts with DMPG lipid bilayer, it is found that WALP23 is initially absorbed at the gel-phase DMPG bilayer with a random coil structure. The absorption of WALP23 on the surface leads to the surface charge reversal and thus changes the orientation of membrane-bound water. As the DMPG bilayer changes from gel phase into fluid phase, WALP23 inserts into the fluid-phase bilayer with its N-terminal end moving across the membrane, which causes the membrane dehydration and the transition of WALP23 conformation from random coil to mixed helix/loop structure and then to pure α-helical structure. The established system is ready to be employed in characterizing other interfacial fast processes, which will be certainly helpful for providing a clear physical picture of the interfacial phenomena.  相似文献
4.
Characterization of real-time and ultrafast motions of the complex molecules at surface and interface is critical to understand how interfacial molecules function. It requires to develop surface-sensitive, fast-identification, and time-resolved techniques. In this study, we employ several key technical procedures and successfully develop a highly sensitive femtosecond time-resolved sum frequency generation vibrational spectroscopy (SFG-VS) system. This system is able to measure the spectra with two polarization combinations (ssp and ppp, or psp and ssp) simultaneously. It takes less than several seconds to collect one spectrum. To the best of our knowledge, it is the fastest speed of collecting SFG spectra reported by now. Using the time-resolved measurement, ultrafast vibrational dynamics of the N-H mode of α-helical peptide at water interface is determined. It is found that the membrane environment does not affect the N-H vibrational relaxation dynamics. It is expected that the time-resolved SFG system will play a vital role in the deep understanding of the dynamics and interaction of the complex molecules at surface and interface. Our method may also provide an important technical proposal for the people who plan to develop time-resolved SFG systems with simultaneous measurement of multiple polarization combinations.  相似文献
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