摘要
为表征琼胶多糖溶液在淬火后形成凝胶过程中分子构象的变化,提出脉冲梯度场核磁共振技术表征的新手段。通过测量溶液中琼胶多糖分子的质子信号强度和自扩散系数的变化,考察了淬火温度对琼胶多糖形成凝胶过程影响。研究发现,淬火发生30 min内,多糖质子信号强度及自扩散系数都急剧减小,而后在恒温测量(0.5~18 h)期间,多糖质子信号强度进一步减小。在恒温测量(0.5~18 h)期间,当淬火温度接近凝胶转变温度时,琼胶多糖分子的自扩散系数变大,而当淬火温度低于凝胶转变温度时,琼胶多糖的自扩散系数会减小。结果表明:淬火发生后凝胶分两步形成:首先,多糖分子形成聚合物网状结构;其次,随着时间的推移,越来越多的多糖分子进入到聚合物网状结构。如果淬火温度低于凝胶转变温度,体系的变化快而显著。
Changes in the molecular mobility of agar were measured by pulsed-field-gradient stimulated echo（PFGSTE） H NMR after quenching,in order to elucidate the effect of different quenching temperature on gelation in agar solutions.Both the echo signal intensity of agar I_（agar）（0） and the diffusion coefficient of agar D_（agar） showed a steep decrease during the initial cooling stage（in the first ca.30 minutes） and /ag？（0） decreased further with time going by,while D_（agar） increased a little after quenching occurred at around T_（s-g） and decreased a little when quenching temperature was below T.These results suggested that the gelation occurred in two stages：firstly the polysaccharide chains in agar aggregated into bundles to form a network when quenching happened.And then more and more agar chains were involved into the network.Changes became more rapidly and more obviously while the quenching temperatures was below T_（s-g）.
出处
《实验室研究与探索》
CAS
北大核心
2017年第1期42-45,共4页
Research and Exploration In Laboratory
基金
上海交通大学科技创新专项-青年教师科研起步(AF4040006)
关键词
琼胶
脉冲梯度场核磁共振
自扩散系数
凝胶
淬火温度
agar
pulse field gradient nuclear magnetic resonance（PFG NMR）
diffusion coefficient
gelation
quenching temperature
