Journal
POLYMERS
Volume 13, Issue 11, Pages -Publisher
MDPI
DOI: 10.3390/polym13111690
Keywords
poly(glutamic acid); pyrene excimer fluorescence; fluorescence blob model; denaturation
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Funding
- Natural Sciences and Engineering Research Council of Canada (NSERC)
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The denaturation process of alpha-helical poly(L-glutamic acid) (PLGA) in N,N-dimethyl-formamide with addition of guanidine hydrochloride (GdHCl) was characterized using fluorescence comparison. By taking advantage of pyrene excimer formation (PEF), changes in the conformation of alpha-helical Py-PLGA were probed. Analysis using Fluorescence Blob Model (FBM) revealed a decrease in the average number of glutamic acids located inside a blob as GdHCl concentration increased, indicating the unravelling of the alpha-helix in PLGA.
The denaturation undergone by alpha-helical poly(L-glutamic acid) (PLGA) in N,N-dimethyl-formamide upon addition of guanidine hydrochloride (GdHCl) was characterized by comparing the fluorescence of a series of PLGA constructs randomly labeled with the dye pyrene (Py-PLGA) to that of a series of Py-PDLGA samples prepared from a racemic mixture of D,L-glutamic acid. The process of pyrene excimer formation (PEF) was taken advantage of to probe changes in the conformation of alpha-helical Py-PLGA. Fluorescence Blob Model (FBM) analysis of the fluorescence decays of the Py-PLGA and Py-PDLGA constructs yielded the average number () of glutamic acids located inside a blob, which represented the volume probed by an excited pyrenyl label. remained constant for randomly coiled Py-PDLGA but decreased from similar to 20 to similar to 10 glutamic acids for the Py-PLGA samples as GdHCl was added to the solution. The decrease in reflected the decrease in the local density of PLGA as the alpha-helix unraveled in solution. The changes in with GdHCl concentration was used to determine the change in Gibbs energy required to denature the PLGA alpha-helix in DMF. The relationship between and the local density of macromolecules can now be applied to characterize the conformation of macromolecules in solution.
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