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United States Department of Agriculture

Agricultural Research Service

Title: Dilute Solution Behavior of Dendrimers and Polysaccharides: Sec, Esi-Ms, and Computer Modeling

Authors
item Striegel, Andre
item Plattner, Ronald
item WILLETT, JULIOUS

Submitted to: Analytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 12, 1998
Publication Date: N/A

Interpretive Summary: While much effort has been devoted to studying starch and its by-products, an appropriate understanding of these still does not exist. It is, therefore, advantageous to compare these substances to others, either natural or man-made, which are better understood. A method has been used in which starch derivatives have been compared to other sugars, as well as to synthetic polymers. The sizes for all of these were determined and were found to be much more diverse for the starch derivatives than for the other substances. The behavior of the starch by-products was found to be intermediate to that of the sugars and synthetic polymers. Our results highlighted differences between the derivatives in our study and those examined by others. Moreover, the sizes of the man-made substances, as determined by our work in the laboratory, agreed well with the sizes we predicted by using computers. Beneficiaries of this work include the starch industry, which has a direct interest in the improved characterization of starch derivatives; the food industry, which has a continuing interest in the study of carbohydrates; and the pharmaceutical industry, for which the study of both dendrimers and carbohydrates can aid in drug design and delivery.

Technical Abstract: Dendrimers, the most highly branched structures achievable, have found numerous uses in the chemical, biological, and pharmaceutical fields. We have employed size exclusion chromatography (SEC) with universal calibration to determine molecular weight averages, distributions, intrinsic viscosities, and structural parameters of Starburst dendrimers, dextrans, and the starch degradation polysaccharides known as maltodextrins. Comparisons have been made in the dilute solution behavior of dendrimers and polysaccharides with equivalent weight-average molecular weights. Intrinsic viscosities decreased in the order I.V. dextran > I.V. dextrin > I.V. dendrimer. While the difference between dendrimer and polysaccharides may be attributed to the higher branching of the former, which leads to a higher chain density in solution, the difference between dextran and dextrin is likely a result of the variation in solution nbehavior of alpha-(1-6) vs. alpha-(1-4) linked carbohydrates. The solutio behavior of the maltodextrins studied indicates that debranching in their manufacture appears to have been more thorough than in that of beta-limiting dextrins studied by other groups. Comparison of molecular radii obtained from SEC data to radii from molecular dynamics studies show Starburst dendrimers behave as theta-stars with functionality between 1 and 4. Additionally, electrospray ionization mass spectrometry was employed to determine Mw, Mn, PD of Astramol dendrimers.

Last Modified: 9/10/2014
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