2011/04/20 by Robert P. Rambo, John A. Tainer · 555 citations
Biochemistry, Genetics and Molecular Biology · Chemistry · Materials Science · Mathematics · #Biological system #Biology #Biopolymer #Chemical physics #Chemistry #Condensed matter physics #Debye #Debye length #Enzyme Structure and Function #Flexibility (engineering) #Macromolecule #Mathematics #Mesoscopic physics #Nuclear Structure and Function #Optics #Physics #Polymer #Protein Structure and Dynamics #Scattering #Small-angle X-ray scattering #Small-angle scattering #Statistical physics #Statistics
paper · doi:10.1002/bip.21638
published in Biopolymers 95(8), 559-571 (Wiley)
openalex publication_date 2011/04/20 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
Unstructured proteins, RNA or DNA components provide functionally important flexibility that is key to many macromolecular assemblies throughout cell biology. As objective, quantitative experimental measures of flexibility and disorder in solution are limited, small angle scattering (SAS), and in particular small angle X-ray scattering (SAXS), provides a critical technology to assess macromolecular flexibility as well as shape and assembly. Here, we consider the Porod-Debye law as a powerful tool for detecting biopolymer flexibility in SAS experiments. We show that the Porod-Debye region fundamentally describes the nature of the scattering intensity decay by capturing the information needed for distinguishing between folded and flexible particles. Particularly for comparative SAS experiments, application of the law, as described here, can distinguish between discrete conformational changes and localized flexibility relevant to molecular recognition and interaction networks. This approach aids insightful analyses of fully and partly flexible macromolecules that is more robust and conclusive than traditional Kratky analyses. Furthermore, we demonstrate for prototypic SAXS data that the ability to calculate particle density by the Porod-Debye criteria, as shown here, provides an objective quality assurance parameter that may prove of general use for SAXS modeling and validation.