The native protein structures in buffer solution are maintained by the electrostatic force as well as the hydrophobic force, salt ions play an important role in maintaining the protein native structures, and their eff...The native protein structures in buffer solution are maintained by the electrostatic force as well as the hydrophobic force, salt ions play an important role in maintaining the protein native structures, and their effect on the protein stability has attracted tremendous interests. Infrared spectroscopy has been generally used in molecular structure analysis due to its fingerprint resolution for different species including macromolecules as proteins. However spectral intensities have received much less attention than the vibrational frequencies. Here we report that the spectral intensities of protein amide I band, the finger prints for the protein secondary structures, are very sensitive to the local electric field known as Onsager reaction field caused by salt ions. IR absorbance thermal titrations have been conducted for a series of samples including simple water soluble amino acids, water soluble monomeric protein cytochrome c and dimeric protein DsbC and its single-site mutant G49R. We found that at lower temperature range （10-20℃）, there exists a thermal activated salting-in process, where the IR intensity increases with a rise in the temperature, corresponding to the ions binding of the hydrophobic surface of protein. This process is absent for the amino acids. When further raising the temperature, the IR intensity decreases, this is interpreted as the thermal activated breaking of the ion-protein surface binding. Applying Van＇t Hoff plot to the thermal titration curves, the thermodynamic parameters such as AH and AS for salting-in and ion unbinding processes can be derived for various protein secondary structural components, revealing quantitatively the extent of hydrophobic interaction as well as the strength of the ion-protein binding.展开更多
A field experiment was conducted using a split plot randomized complete block design with three replications to study the effects of potassium (K) and phosphorus (P) application on sunflower (Helianthus annuus L.) gro...A field experiment was conducted using a split plot randomized complete block design with three replications to study the effects of potassium (K) and phosphorus (P) application on sunflower (Helianthus annuus L.) growth at the New Developmental Research Farm of Khyber Pakhtunkhwa Agricultural University in Peshawar,Pakistan.Six levels of K (0,25,50,75,100 and 125 kg K ha-1) were main plots while four levels of P (0,45,90 and 135 kg P ha-1) were subplots.Increase in both K and P levels enhanced grain oil concentration of sunflower.Increase in P level increased grain protein concentration,while increase in K level decreased grain protein concentration.Both oil and protein yields increased significantly with increase in K and P levels.The increase in oil and protein yields of sunflower was mainly attributed to the improvement in yield components (grains per head,grain weight and head size) and the significant increase in grain yield.The highest net returns of 297 and 368 US$ ha-1 based on grain and oil yields,respectively,were obtained from a combination of 100 kg K ha-1 + 45 kg P ha-1.展开更多
We report the fabrication of a highly sensitive field-effect transistor （FET） biosensor using thermally-reduced graphene oxide （TRGO） sheets functionalized with gold nanoparticle （NP）-antibody conjugates. Probe ...We report the fabrication of a highly sensitive field-effect transistor （FET） biosensor using thermally-reduced graphene oxide （TRGO） sheets functionalized with gold nanoparticle （NP）-antibody conjugates. Probe antibody was labeled on the surface of TRGO sheets through Au NPs and electrical detection of protein binding （Immunoglobulin G/IgG and anti-lmmunoglobulin G/anti-lgG） was accomplished by FET and direct current （dc） measurements. The protein binding events induced significant changes in the resistance of the TRGO sheet, which is referred to as the sensor response. The dependence of the sensor response on the TRGO base resistance in the sensor and the antibody areal density on the TRGO sheet was systematically studied, from which a correlation of the sensor response with sensor parameters was found： the sensor response was more significant with larger TRGO base resistance and higher antibody areal density. The detection limit of the novel biosensor was around the 0.2 ng/rnL level, which is among the best of,＇eported carbon nanomaterial-based protein sensors and can be further optimized by tuning the sensor structure.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.20373088）, the Program for Innovation Group （No.60321002）, the Innovative Project of Chinese Academy of Sciences （No.KJCX2-SW-w29）, and the National Key Project for Basic Research No.2006CB910302）. We thank Prof. Chih-chen Wang and Dr. Hui-min Ke in the Institute of Biophysics, Chinese Academy of Science, for the preparation of samples DsbC and G49R. We also thank Prof. Xiang-gang Qiu in the Institute of physics, Chinese Academy of Sciences, for help in FTIR measurement.
文摘The native protein structures in buffer solution are maintained by the electrostatic force as well as the hydrophobic force, salt ions play an important role in maintaining the protein native structures, and their effect on the protein stability has attracted tremendous interests. Infrared spectroscopy has been generally used in molecular structure analysis due to its fingerprint resolution for different species including macromolecules as proteins. However spectral intensities have received much less attention than the vibrational frequencies. Here we report that the spectral intensities of protein amide I band, the finger prints for the protein secondary structures, are very sensitive to the local electric field known as Onsager reaction field caused by salt ions. IR absorbance thermal titrations have been conducted for a series of samples including simple water soluble amino acids, water soluble monomeric protein cytochrome c and dimeric protein DsbC and its single-site mutant G49R. We found that at lower temperature range （10-20℃）, there exists a thermal activated salting-in process, where the IR intensity increases with a rise in the temperature, corresponding to the ions binding of the hydrophobic surface of protein. This process is absent for the amino acids. When further raising the temperature, the IR intensity decreases, this is interpreted as the thermal activated breaking of the ion-protein surface binding. Applying Van＇t Hoff plot to the thermal titration curves, the thermodynamic parameters such as AH and AS for salting-in and ion unbinding processes can be derived for various protein secondary structural components, revealing quantitatively the extent of hydrophobic interaction as well as the strength of the ion-protein binding.
文摘A field experiment was conducted using a split plot randomized complete block design with three replications to study the effects of potassium (K) and phosphorus (P) application on sunflower (Helianthus annuus L.) growth at the New Developmental Research Farm of Khyber Pakhtunkhwa Agricultural University in Peshawar,Pakistan.Six levels of K (0,25,50,75,100 and 125 kg K ha-1) were main plots while four levels of P (0,45,90 and 135 kg P ha-1) were subplots.Increase in both K and P levels enhanced grain oil concentration of sunflower.Increase in P level increased grain protein concentration,while increase in K level decreased grain protein concentration.Both oil and protein yields increased significantly with increase in K and P levels.The increase in oil and protein yields of sunflower was mainly attributed to the improvement in yield components (grains per head,grain weight and head size) and the significant increase in grain yield.The highest net returns of 297 and 368 US$ ha-1 based on grain and oil yields,respectively,were obtained from a combination of 100 kg K ha-1 + 45 kg P ha-1.
基金Financial support for this work was provided by the USA National Science Foundation （NSF） （Nos. CMMI- 0900509, CBET-0803142, and ECCS-0708998）. Graphene oxide samples were supplied by Prof. Rodney S. Ruoff. The authors thank Dr. Heather A. Owen for technical support with SEM, and Dr. Leonidas E. Ocola for assistance in the electrode fabrication. The e-beam lithography was performed at the Center for Nanoscale Materials of Argonne National Laboratory, which is supported by the USA Department of Energy （No. DE- AC02-06CH11357）. The SEM imaging was conducted at the Electron Microscope Laboratory of University of Wisconsin-Milwaukee.
文摘We report the fabrication of a highly sensitive field-effect transistor （FET） biosensor using thermally-reduced graphene oxide （TRGO） sheets functionalized with gold nanoparticle （NP）-antibody conjugates. Probe antibody was labeled on the surface of TRGO sheets through Au NPs and electrical detection of protein binding （Immunoglobulin G/IgG and anti-lmmunoglobulin G/anti-lgG） was accomplished by FET and direct current （dc） measurements. The protein binding events induced significant changes in the resistance of the TRGO sheet, which is referred to as the sensor response. The dependence of the sensor response on the TRGO base resistance in the sensor and the antibody areal density on the TRGO sheet was systematically studied, from which a correlation of the sensor response with sensor parameters was found： the sensor response was more significant with larger TRGO base resistance and higher antibody areal density. The detection limit of the novel biosensor was around the 0.2 ng/rnL level, which is among the best of,＇eported carbon nanomaterial-based protein sensors and can be further optimized by tuning the sensor structure.
