马槟榔甜味蛋白的圆二色谱和激光拉曼光谱

测定了自马槟榔(Capparis masaikai Levl.)种子分离的二种甜味蛋白MaⅠ和MaⅡ的远紫外区域圆二色谱,并按Yang和Chen的方法用最小二乘法计算了它们的构象单元含量,结果表明α螺旋含量最多:对MaⅠf_H=0.43、f_β=0.24、f_R=0.33;对MaⅡ,f_H=0.37、f_β=0.33、f_R=0.30;其相关系数均为0.9876;计算所得理论曲线与实验曲钱其本吻合。二种甜蛋白的激光拉曼光谱测定结果也表明其主要构象单元为α螺旋,此外,均无SH谱带:MaⅠ的Tyr残基暴露于分子表面;与MaⅡ相比,MaⅠ有明显的545cm~(-1)和1101cm~(-1)谱带,这可能从构象上说明MaⅠ与MaⅡ对热和变性剂处理表现不同的原因。

CIRCULAR DiCHROISM SPECTRA AND LASER RAMAN SPECTRA OF THE SWEET PROTEIN MABINLINSFROM Capparis masaikai Levl

CD spectra in far ultraviolet region of two sweet proteins (Mabinlin) MaⅠ and MaⅡ from the seeds of Capparis masaikai Levl were recorded and according to Yang and Chen's method,the content of different conformational units were estimated by least square method using Dual computer system.From the CD spectra of MaⅠ and MaⅡ,an obviously positive peak at about 190nm and two negative peaks near 210 and 220nm were easily found.These illustrated that the a-helices were the major conformational units of both proteins; the regression coefficients of calculation were fH=0.43,fβ=0.24,fR=0.33 for MaⅠ,and fH=0.37,fβ=0,33,fβ=0.30 for MaⅡ,the correlation values were both 0.9876.The theoretical curves obtained using these coefficients were well in accordance with the experimental data.From Raman spectra of MaⅠ and MaⅡ,the positions of Amide Ⅰ and Ⅲ bands also indicated that the main conformational units were a-helices.There was no SH peak; the Tyr residues of MaⅠ were shown to be on the surface of the protein molecule.The stronger intensity of peaks at 545 cm-1 and 1101 cm-1 of MaⅠ may be the the signs of differences between MaⅠ and MaⅡ in sweetness stability to heat and denaturants treatments.