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A Pyrene Excimer Fluorescence (PEF) Study of the Interior of Amylopectin in Dilute Solution
Macromolecules ( IF 5.1 ) Pub Date : 2020-08-12 , DOI: 10.1021/acs.macromol.0c01280 Lu Li 1 , Damin Kim 1 , Xiaofang Zhai 1 , Jean Duhamel 1
Macromolecules ( IF 5.1 ) Pub Date : 2020-08-12 , DOI: 10.1021/acs.macromol.0c01280 Lu Li 1 , Damin Kim 1 , Xiaofang Zhai 1 , Jean Duhamel 1
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The large size of amylopectin represents an experimental challenge for standard analytical techniques to characterize its structure at the molecular level in dilute solution. We introduce a methodology that combines pyrene excimer fluorescence (PEF), the fluorescence blob model (FBM), molecular mechanics optimizations (MMOs), and intrinsic viscosity ([η]) to probe the interior of complex macromolecules with a heterogeneous interior like amylopectin. The combination of PEF, FBM, and MMOs yields the density (ρfluo) of nanosized subvolumes of the macromolecule, called blobs within the framework of the FBM, while [η] yields the density (ρ) probed over the length scale of the entire macromolecule. Comparison of ρ and ρfluo indicates whether matter is either homogeneously (ρ = ρfluo) or heterogeneously (ρ < ρfluo) distributed inside the macromolecule. The main advantage of the methodology is to shift the focus of the study from the entire polydisperse macromolecule to that of monodisperse blobs where a blob represents the volume probed by a given pyrene derivative. This methodology is thus ideally suited to probe polydisperse heterogeneous macromolecules in solution. It is applied to amylopectin. The finding that ρ was much smaller than ρfluo for amylopectin in dilute solution led to the conclusion that the side chains of amylopectin are heterogeneously distributed inside the amylopectin interior. The ρfluo value agreed with the notion that the helical side chains of amylopectin form clusters where the side chains are ∼2.7 nm apart. When ρ and ρfluo were determined for nanosized amylopectin fragments (NAFs) produced through extrusion, ρfluo took the same value as for amylopectin while ρ increased with decreasing NAF size, approaching ρfluo for the smallest NAF. This observation led to the conclusion that the clusters of helical oligosaccharide side chains were loosely connected to each other via linear oligosaccharide segments. These features were captured by the solution-cluster (Sol-CL) model which seems to rationalize many of the experimental observations made about amylopectin.
中文翻译：
稀溶液中支链淀粉内部的P准分子荧光（PEF）研究
支链淀粉的大尺寸代表了标准分析技术在稀溶液中在分子水平表征其结构的实验挑战。我们介绍了一种结合pyr准分子荧光（PEF），荧光斑点模型（FBM），分子力学优化（MMO）和特性粘度（[η]）的方法，以探测复杂的高分子内部以及支链淀粉等异质内部。PEF，FBM和MMO的组合产生了大分子的纳米子体积的密度（ρfluo），称为FBM框架内的斑点，而[η]产生了在整个长度范围内探测到的密度（ρ）。高分子。ρ和ρfluo的比较表明物质是否均质（ρ=ρfluo）或非均质（ρ< ρfluo）分布在大分子内部。该方法的主要优点是将研究重点从整个多分散大分子转移到单分散小斑点，其中小斑点代表给定pyr衍生物探测的体积。因此，该方法非常适合于探测溶液中的多分散异质大分子。它适用于支链淀粉。支链淀粉在稀溶液中ρ比ρfluo小得多的发现导致得出如下结论：支链淀粉的侧链在支链淀粉内部内部异质分布。ρ氟值与支链淀粉的螺旋形侧链形成簇时，侧链相距约2.7 nm是一致的。当确定通过挤压产生的纳米支链淀粉片段（NAF）的ρ和ρfluo时，ρfluo与支链淀粉的值相同，而ρ随着NAF尺寸的减小而增加，对于最小的NAF接近ρfluo。该观察结果得出以下结论：螺旋状寡糖侧链簇通过线性寡糖链段彼此松散地连接。这些特征是由溶液-簇（Sol-CL）模型捕获的，该模型似乎使关于支链淀粉的许多实验观察合理化。
更新日期：2020-08-25
中文翻译：
稀溶液中支链淀粉内部的P准分子荧光（PEF）研究
支链淀粉的大尺寸代表了标准分析技术在稀溶液中在分子水平表征其结构的实验挑战。我们介绍了一种结合pyr准分子荧光（PEF），荧光斑点模型（FBM），分子力学优化（MMO）和特性粘度（[η]）的方法，以探测复杂的高分子内部以及支链淀粉等异质内部。PEF，FBM和MMO的组合产生了大分子的纳米子体积的密度（ρfluo），称为FBM框架内的斑点，而[η]产生了在整个长度范围内探测到的密度（ρ）。高分子。ρ和ρfluo的比较表明物质是否均质（ρ=ρfluo）或非均质（ρ< ρfluo）分布在大分子内部。该方法的主要优点是将研究重点从整个多分散大分子转移到单分散小斑点，其中小斑点代表给定pyr衍生物探测的体积。因此，该方法非常适合于探测溶液中的多分散异质大分子。它适用于支链淀粉。支链淀粉在稀溶液中ρ比ρfluo小得多的发现导致得出如下结论：支链淀粉的侧链在支链淀粉内部内部异质分布。ρ氟值与支链淀粉的螺旋形侧链形成簇时，侧链相距约2.7 nm是一致的。当确定通过挤压产生的纳米支链淀粉片段（NAF）的ρ和ρfluo时，ρfluo与支链淀粉的值相同，而ρ随着NAF尺寸的减小而增加，对于最小的NAF接近ρfluo。该观察结果得出以下结论：螺旋状寡糖侧链簇通过线性寡糖链段彼此松散地连接。这些特征是由溶液-簇（Sol-CL）模型捕获的，该模型似乎使关于支链淀粉的许多实验观察合理化。
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