光谱学与光谱分析
光譜學與光譜分析
광보학여광보분석
SPECTROSCOPY AND SPECTRAL ANALYSIS
2015年
2期
384-389
,共6页
任皓威%张婉舒%李相怡%刘宁
任皓威%張婉舒%李相怡%劉寧
임호위%장완서%리상이%류저
圆二色光谱%拉曼光谱%人乳β-酪蛋白%二级结构%pH 值
圓二色光譜%拉曼光譜%人乳β-酪蛋白%二級結構%pH 值
원이색광보%랍만광보%인유β-락단백%이급결구%pH 치
Circular dichroism%Raman spectroscopy%Human milkβ-casein%Secondary structure%pH
人乳中β-酪蛋白为婴儿的快速生长提供了最适宜的氨基酸、钙磷等。以往的研究均是对牛乳的β-酪蛋白二级结构进行分析,而牛乳β-酪蛋白对婴儿配方乳的指导意义不如人乳β-酪蛋白,且人乳β-酪蛋白难以获得合适的蛋白晶体,其三级结构不清楚。为了获得中国人乳β-酪蛋白二级结构的相关基础信息,采用圆二色光谱(CD)法和拉曼光谱(Raman)法分析在不同pH 条件下其二级结构的变化,结果表明:pH 值的改变能够诱导中国人乳β-酪蛋白二级结构的改变,CD分析表明β-酪蛋白各部分的二级结构分别是:0.5%~2%α-螺旋,16%~18%β-折叠,30%~34%β-转角,49%~51%无规则卷曲;随着pH 的增加,部分结构发生了变化,α-螺旋在pH 8处含量增加,而在pH 10处含量减小。拉曼光谱分析表明:β-酪蛋白在酰胺I的特征峰在1662 cm-1处,分析出β-酪蛋白的无规则卷曲含量较高。同时,根据I850/I830的比值计算出β-酪蛋白的酪氨酸残基趋向于“暴露式”。圆二色光谱和拉曼光谱都证明了人乳β-酪蛋白二级结构中无规则卷曲的含量最高,而β-折叠和β-转角含量保持相对的稳定。并且,在pH 8条件下,α-螺旋含量高于在其他pH 条件下的含量。
人乳中β-酪蛋白為嬰兒的快速生長提供瞭最適宜的氨基痠、鈣燐等。以往的研究均是對牛乳的β-酪蛋白二級結構進行分析,而牛乳β-酪蛋白對嬰兒配方乳的指導意義不如人乳β-酪蛋白,且人乳β-酪蛋白難以穫得閤適的蛋白晶體,其三級結構不清楚。為瞭穫得中國人乳β-酪蛋白二級結構的相關基礎信息,採用圓二色光譜(CD)法和拉曼光譜(Raman)法分析在不同pH 條件下其二級結構的變化,結果錶明:pH 值的改變能夠誘導中國人乳β-酪蛋白二級結構的改變,CD分析錶明β-酪蛋白各部分的二級結構分彆是:0.5%~2%α-螺鏇,16%~18%β-摺疊,30%~34%β-轉角,49%~51%無規則捲麯;隨著pH 的增加,部分結構髮生瞭變化,α-螺鏇在pH 8處含量增加,而在pH 10處含量減小。拉曼光譜分析錶明:β-酪蛋白在酰胺I的特徵峰在1662 cm-1處,分析齣β-酪蛋白的無規則捲麯含量較高。同時,根據I850/I830的比值計算齣β-酪蛋白的酪氨痠殘基趨嚮于“暴露式”。圓二色光譜和拉曼光譜都證明瞭人乳β-酪蛋白二級結構中無規則捲麯的含量最高,而β-摺疊和β-轉角含量保持相對的穩定。併且,在pH 8條件下,α-螺鏇含量高于在其他pH 條件下的含量。
인유중β-락단백위영인적쾌속생장제공료최괄의적안기산、개린등。이왕적연구균시대우유적β-락단백이급결구진행분석,이우유β-락단백대영인배방유적지도의의불여인유β-락단백,차인유β-락단백난이획득합괄적단백정체,기삼급결구불청초。위료획득중국인유β-락단백이급결구적상관기출신식,채용원이색광보(CD)법화랍만광보(Raman)법분석재불동pH 조건하기이급결구적변화,결과표명:pH 치적개변능구유도중국인유β-락단백이급결구적개변,CD분석표명β-락단백각부분적이급결구분별시:0.5%~2%α-라선,16%~18%β-절첩,30%~34%β-전각,49%~51%무규칙권곡;수착pH 적증가,부분결구발생료변화,α-라선재pH 8처함량증가,이재pH 10처함량감소。랍만광보분석표명:β-락단백재선알I적특정봉재1662 cm-1처,분석출β-락단백적무규칙권곡함량교고。동시,근거I850/I830적비치계산출β-락단백적락안산잔기추향우“폭로식”。원이색광보화랍만광보도증명료인유β-락단백이급결구중무규칙권곡적함량최고,이β-절첩화β-전각함량보지상대적은정。병차,재pH 8조건하,α-라선함량고우재기타pH 조건하적함량。
To obtain a structural basis for theβ-casein in Chinese human milk,structural transitions of theβ-casein in response to variation of pH were investigated using Raman and circular dichroism (CD)spectroscopy.Both methods indicated that the sec-ondary structures ofβ-casein in the solution were induced by the pH.Secondary structural analysis ofβ-casein by CD spectrosco-py yielded 0. 5%~2%α-helical,16%~18%β-sheet,30%~34%β-turn and 49%~51% random coil contents.Another result was that as pH increases,these structures change.Several distinct transitions were observed by circular dichroism inα-helix at pH 8 and pH 10.Raman spectrum also showed random coil as the major secondary structure in nativeβ-casein,for the charac-teristic band of theβ-casein amide I was at 1 662 cm-1 .Calculations from I850/I830 suggested that the tyrosine residues ofβ-case-in tended to “exposure”.CD and Raman spectra both showed that at neutral and alkaline pH theβ-casein existed predominantly in random coil conformation,and the proportion ofα-helix was higher at pH 8 than under other pH conditions.Over the range of pH studied,the sheet and turn areas remained relatively constant,and in the condition of pH 8,the content ofα-helical was higher than in the other pH conditions.