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Nanometer-Scale Smectic Ordering of Genetically Engineered Rodlike Polymers:  Synthesis and Characterization of Monodisperse Derivatives of Poly(γ-benzyl α,L-glutamate)

Yu, Seungju M. and Soto, Carissa M. and Tirrell, David A. (2000) Nanometer-Scale Smectic Ordering of Genetically Engineered Rodlike Polymers:  Synthesis and Characterization of Monodisperse Derivatives of Poly(γ-benzyl α,L-glutamate). Journal of the American Chemical Society, 122 (28). pp. 6552-6559. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20150116-151446955

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Abstract

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.


Item Type:Article
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http://dx.doi.org/10.1021/ja000465pDOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja000465pPublisherArticle
ORCID:
AuthorORCID
Tirrell, David A.0000-0003-3175-4596
Additional Information:Copyright © 2000 American Chemical Society. Published In Issue July 19, 2000. Publication Date (Web): June 29, 2000. Received February 7, 2000. Acknowledgment. This work was supported by the National Science Foundation Materials Research Science and Engineering Center at the University of Massachusetts, and by grants from the Polymers and Genetics Programs of the NSF.
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Issue or Number:28
Record Number:CaltechAUTHORS:20150116-151446955
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150116-151446955
Official Citation:Nanometer-Scale Smectic Ordering of Genetically Engineered Rodlike Polymers:  Synthesis and Characterization of Monodisperse Derivatives of Poly(γ-benzyl α,L-glutamate) Seungju M. Yu, Carissa M. Soto, and David A. Tirrell. Journal of the American Chemical Society 2000 122 (28), 6552-6559
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53844
Collection:CaltechAUTHORS
Deposited By: Katherine Johnson
Deposited On:16 Jan 2015 23:25
Last Modified:03 Oct 2019 07:53

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