Influence of Charge Block Length on Conformation and Cluster Formation of Atactic Peptide Polyampholytes

Winnie H. Shi; Amanda B. Marciel

doi:10.1021/acs.macromol.5c02873

Influence of Charge Block Length on Conformation and Cluster Formation of Atactic Peptide Polyampholytes

Winnie H. Shi
, Amanda B. Marciel

Research output: Contribution to journal › Article › peer-review

Abstract

We investigate the effect of the charge block length on the chain conformation and phase behavior of atactic peptide polyampholytes (PAs) with equal numbers of cationic and anionic ionizable monomers. Atactic peptide PAs were produced by using solid-phase peptide synthesis (SPPS), which enables precise control of the molecular weight, monomer sequence, and chain tacticity. Using circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopy, we observe that the atactic peptide PAs show no evidence of secondary structure formation, regardless of block length. Turbidity measurements show that the atactic peptide PAs remain in solution over a wide-range of salt concentrations. Small-angle X-ray scattering (SAXS) measurements reveal that the chain conformation of atactic peptide PAs is compressed compared to expectations for neutral systems. Interestingly, we find that the atactic peptide PAs form block length dependent multichain clusters in solution. These results are consistent with a recent theory predicting that PAs have a block length and concentration dependent threshold for phase separation.

Original language	English
Pages (from-to)	3307-3315
Number of pages	9
Journal	Macromolecules
Volume	59
Issue number	6
DOIs	https://doi.org/10.1021/acs.macromol.5c02873
State	Published - Mar 24 2026
Externally published	Yes

Funding

We thank the National Science Foundation (NSF) CAREER Award (2338550) in the Division of Materials Research (DMR) for financial support. We thank the Shared Equipment Authority (SEA) at Rice University for access to the Circular Dichroism Spectropolarimeter, Nicolet FTIR Infrared Microscope, TECAN Infinite M1000 Pro microplate reader, and Nikon A1-Rsi Confocal. We thank Dr. Guan-Rong Huang, Dr. Wei-Ren Chen, and Dr. Jong Keum for insights on SAXS data analysis. This research used beamline 16-ID (LiX) at the National Synchrotron Light Source II facility of the Center for Functional Nanomaterials (CFN), which is a U.S. Department of Energy Office of Science User Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. This material is also based upon work supported by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education for the DOE under contract number DESC0014664.

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title = "Influence of Charge Block Length on Conformation and Cluster Formation of Atactic Peptide Polyampholytes",

abstract = "We investigate the effect of the charge block length on the chain conformation and phase behavior of atactic peptide polyampholytes (PAs) with equal numbers of cationic and anionic ionizable monomers. Atactic peptide PAs were produced by using solid-phase peptide synthesis (SPPS), which enables precise control of the molecular weight, monomer sequence, and chain tacticity. Using circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopy, we observe that the atactic peptide PAs show no evidence of secondary structure formation, regardless of block length. Turbidity measurements show that the atactic peptide PAs remain in solution over a wide-range of salt concentrations. Small-angle X-ray scattering (SAXS) measurements reveal that the chain conformation of atactic peptide PAs is compressed compared to expectations for neutral systems. Interestingly, we find that the atactic peptide PAs form block length dependent multichain clusters in solution. These results are consistent with a recent theory predicting that PAs have a block length and concentration dependent threshold for phase separation.",

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N2 - We investigate the effect of the charge block length on the chain conformation and phase behavior of atactic peptide polyampholytes (PAs) with equal numbers of cationic and anionic ionizable monomers. Atactic peptide PAs were produced by using solid-phase peptide synthesis (SPPS), which enables precise control of the molecular weight, monomer sequence, and chain tacticity. Using circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopy, we observe that the atactic peptide PAs show no evidence of secondary structure formation, regardless of block length. Turbidity measurements show that the atactic peptide PAs remain in solution over a wide-range of salt concentrations. Small-angle X-ray scattering (SAXS) measurements reveal that the chain conformation of atactic peptide PAs is compressed compared to expectations for neutral systems. Interestingly, we find that the atactic peptide PAs form block length dependent multichain clusters in solution. These results are consistent with a recent theory predicting that PAs have a block length and concentration dependent threshold for phase separation.

AB - We investigate the effect of the charge block length on the chain conformation and phase behavior of atactic peptide polyampholytes (PAs) with equal numbers of cationic and anionic ionizable monomers. Atactic peptide PAs were produced by using solid-phase peptide synthesis (SPPS), which enables precise control of the molecular weight, monomer sequence, and chain tacticity. Using circular dichroism (CD) and Fourier-transform infrared (FTIR) spectroscopy, we observe that the atactic peptide PAs show no evidence of secondary structure formation, regardless of block length. Turbidity measurements show that the atactic peptide PAs remain in solution over a wide-range of salt concentrations. Small-angle X-ray scattering (SAXS) measurements reveal that the chain conformation of atactic peptide PAs is compressed compared to expectations for neutral systems. Interestingly, we find that the atactic peptide PAs form block length dependent multichain clusters in solution. These results are consistent with a recent theory predicting that PAs have a block length and concentration dependent threshold for phase separation.

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Influence of Charge Block Length on Conformation and Cluster Formation of Atactic Peptide Polyampholytes

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