Nanometer-Scale Smectic Ordering of Genetically Engineered Rodlike Polymers: Synthesis and Characterization of Monodisperse Derivatives of Poly(γ-benzyl α,l-glutamate)
Nanometer-Scale Smectic Ordering of Genetically Engineered Rodlike Polymers: Synthesis and Characterization of Monodisperse Derivatives of Poly(γ-benzyl α,l-glutamate)
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DOI：
10.1021/ja000465p
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发表时间：
2000-07
影响因子：
15
通讯作者：
Seungju M. Yu;C. M. Soto;D. Tirrell
中科院分区：
文献类型：
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作者：
Seungju M. Yu;C. M. Soto;D. Tirrell
具有精确定义的纳米级结构的大分子是自组装材料和纳米级器件的理想构建块。利用重组DNA技术和细菌蛋白表达，我们制备了一组棒状人工蛋白质Glu（OBzl）Asp（OBzl）[Glu（OBzl）_（17）Asp（OBzl）]_X-Glu（OBzl）Glu（OBzl）（PBLG-X，X = 3 - 6，1），作为聚（γ-α，l-谷氨酸苄酯）（PBLG）的单分散类似物，杆长变化范围为8.7至17 nm。合成是通过（i）细菌生产前体多肽GluAsp（Glu_（17）Asp）_XGluGlu（PLGA-X，X = 3−6），作为与小鼠二氢叶酸还原酶（DHFR）的融合物，（ii）CNBr消化表达的蛋白质以释放PLGA-X，以及（iii）通过用苯基重氮甲烷处理PLGA-X的侧链苄基化。重组基因转化培养物的生长速度和表达蛋白的产量取决于连接在融合配偶体上的Glu_（17）Asp重复序列的数目，随着重复序列数目的增加而降低。PBLG-3，具有最低的纵横比（6.9），没有表现出液晶（LC）行为，而其他聚合物中的每一个形成溶致液晶相。PBLG-X的相变行为是明显不同于传统的多分散PBLG的;当聚合物溶液的浓度逐渐增加时，从各向同性到液晶态的转变均匀地发生在整个样品中，而没有形成明显的双折射液滴。PBLG-4和PBLG-5的溶液浇铸膜形成层间距（分别为11.4和14.0 nm）的近晶超分子结构，精确地由单分散棒的长度确定。近晶有序仅在从氯仿（97%）和三氟乙酸（3%）的混合物浇铸的膜中观察到。在由二氧六环制备的薄膜中，多分散和单分散PBLG均采用柱状排列，没有形成近晶层。
Macromolecules with precisely defined architectures on the nanometer scale are ideal building blocks for self-assembled materials and nanometer-scale devices. By utilizing recombinant DNA technology and bacterial protein expression, we have prepared a set of rodlike artificial proteins, Glu(OBzl)Asp(OBzl)[Glu(OBzl)_(17)Asp(OBzl)]_X-Glu(OBzl)Glu(OBzl) (PBLG-X, X = 3−6, 1), which serve as monodisperse analogues of poly(γ-benzyl α,l-glutamate) (PBLG), with variation of rod length from 8.7 to 17 nm. Synthesis was accomplished by (i) bacterial production of a precursor polypeptide GluAsp(Glu_(17)Asp)_XGluGlu (PLGA-X, X = 3−6), as a fusion to mouse dihydrofolate reductase (DHFR), (ii) CNBr digestion of the expressed protein to liberate PLGA-X, and (iii) side chain benzylation of PLGA-X via treatment with phenyldiazomethane. The growth rates of cultures transformed with the recombinant genes, and the yields of protein expressed therein, depended on the number of Glu_(17)Asp repeats appended to the fusion partner, decreasing as the number of repeats increased. PBLG-3, with the lowest aspect ratio (6.9), did not exhibit liquid crystalline (LC) behavior while each of the other polymers formed lyotropic LC phases. The phase transition behavior of PBLG-X was distinctly different from that of conventional polydisperse PBLG; when the concentration of the polymer solution was gradually increased, the transition from the isotropic to the liquid crystalline state occurred uniformly throughout the sample without formation of distinct birefringent droplets. Solution-cast films of PBLG-4 and PBLG-5 formed smectic supramolecular architectures with layer spacings (11.4 and 14.0 nm, respectively) precisely determined by the length of the monodisperse rods. Smectic ordering was observed only in films cast from mixtures of chloroform (97%) and trifluoroacetic acid (3%). In films prepared from dioxane, both polydisperse and monodisperse PBLGs adopted columnar order without formation of smectic layers.