G-A mismatches are non-canonical base pairs that widely occur in native nucleic acids. They have been found to be functionally important in adopting unusual structures. In this paper, G-A mispairing was studied by Ram...G-A mismatches are non-canonical base pairs that widely occur in native nucleic acids. They have been found to be functionally important in adopting unusual structures. In this paper, G-A mispairing was studied by Raman spectral characterization of Polyadenylic acid （PolyA）, Polyguanylic acid （PolyG） and their equimolar mixture in solution of 0.08 mol/L Na^＋, pH7.0. The experiment showed the following three results. （1） At the experimental conditions used in the present work, PolyA and G A complexes existed as single-stranded and double-stranded helix of A form, respectively. And PolyG mainly occurred to be anti-parallel quadruplex conformers. （2） The formation of G A complexes, on one hand strengthened parts of base stacking interactions especially for PolyG, leading to Raman hypochromism effect with some corresponding bands shifting, and on the other hand weakened other base stacking interactions especially for PolyA to a certain degree. During this process, the backbone of PolyG underwent a significant change, but PolyA still conserved its main chain conformation. （3） The formation of G A complexes was stabilized by two interbase hydrogen- bond interactions （i.e. N6H2（A）-N3 （G） and N7 （A）--N2H2（G）） and a third hydrogen bond between O2^＋ （G） and N6 （A）. The third hydrogen bond was responsible for the remarkable changes of PolyG backbone conformation.展开更多
Vis/NIR spectroscopy,in combination with partial least square(PLS)analysis and a back-propagation neural network,is investigated to identify endothelium corneum gigeriae galli(ECGG).The spectral features of ECGGs and ...Vis/NIR spectroscopy,in combination with partial least square(PLS)analysis and a back-propagation neural network,is investigated to identify endothelium corneum gigeriae galli(ECGG).The spectral features of ECGGs and their counterfeits are reasonably differentiated in vis/NIR region,which provides enough qualitative information to establish the relationship between the spectra and samples for identification.After pretreatment of the spectral data,cross validation is implemented for extracting the best number of principal components.Then the calibration and validation set are performed well.The PLS and back propagation neural network(BPNN)model gives the BPNN to be 0.9941 and the root mean square residual(RMSR)to be 0.0775 for the calibration set,and the multiple correlation coefficient(MCC)to 0.9874 and the RMSE to 0.1134 for the validation set.Thus the PLS and BPNN model is reliable and practicable.Through testing,a recognition accuracy of 100%is achieved.The present study could offer a new approach for fast and nondestructive discrimination of ECGG and its counterfeit.展开更多
基金Project supported by the Natural Science Foundation of Guangdong Province, China （Grant No 021093） and Key-stone Science and Technology Foundation of Guangdong Province, China （Grant No 2KM04502S）.
文摘G-A mismatches are non-canonical base pairs that widely occur in native nucleic acids. They have been found to be functionally important in adopting unusual structures. In this paper, G-A mispairing was studied by Raman spectral characterization of Polyadenylic acid （PolyA）, Polyguanylic acid （PolyG） and their equimolar mixture in solution of 0.08 mol/L Na^＋, pH7.0. The experiment showed the following three results. （1） At the experimental conditions used in the present work, PolyA and G A complexes existed as single-stranded and double-stranded helix of A form, respectively. And PolyG mainly occurred to be anti-parallel quadruplex conformers. （2） The formation of G A complexes, on one hand strengthened parts of base stacking interactions especially for PolyG, leading to Raman hypochromism effect with some corresponding bands shifting, and on the other hand weakened other base stacking interactions especially for PolyA to a certain degree. During this process, the backbone of PolyG underwent a significant change, but PolyA still conserved its main chain conformation. （3） The formation of G A complexes was stabilized by two interbase hydrogen- bond interactions （i.e. N6H2（A）-N3 （G） and N7 （A）--N2H2（G）） and a third hydrogen bond between O2^＋ （G） and N6 （A）. The third hydrogen bond was responsible for the remarkable changes of PolyG backbone conformation.
基金Supported by the National Natural Science Foundation of China under Grant No 60878063the Program from Traditional Chinese Medicine Bureau of Guangdong Province(2008233).
文摘Vis/NIR spectroscopy,in combination with partial least square(PLS)analysis and a back-propagation neural network,is investigated to identify endothelium corneum gigeriae galli(ECGG).The spectral features of ECGGs and their counterfeits are reasonably differentiated in vis/NIR region,which provides enough qualitative information to establish the relationship between the spectra and samples for identification.After pretreatment of the spectral data,cross validation is implemented for extracting the best number of principal components.Then the calibration and validation set are performed well.The PLS and back propagation neural network(BPNN)model gives the BPNN to be 0.9941 and the root mean square residual(RMSR)to be 0.0775 for the calibration set,and the multiple correlation coefficient(MCC)to 0.9874 and the RMSE to 0.1134 for the validation set.Thus the PLS and BPNN model is reliable and practicable.Through testing,a recognition accuracy of 100%is achieved.The present study could offer a new approach for fast and nondestructive discrimination of ECGG and its counterfeit.
