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Quantification and Elucidation of the Overall Interaction between Nanoparticles
Published in Victor M. Starov, Nanoscience, 2010
W. Richard Bowen, Paul M. Williams
Having determined the numbers of amino acid groups giving rise to the surface charge on a lactoferrin molecule, the isoionic point of the lactoferrin molecule may be estimated. The isoionic point is the pH at which there would be no surface charge on a molecule if no additional ion binding to the molecule occurs (this value is sometimes confused in the literature with the isoelectric point, which is the pH at which there is no net surface charge on a molecule including binding of additional ions to the molecule). The pH value thus calculated for the isoionic point of lactoferrin is 9.19. This value is much higher than the value that was found for the point of zero zeta potential of lactoferrin in a 0.03 M sodium chloride electrolyte solution from electrophoretic mobility experiments, which occurs at approximately pH 6.1 (see Figure 4.4).
Proteins in Solution and at Interfaces
Published in E. D. Goddard, K. P. Ananthapadmanabhan, Interactions of Surfactants with Polymers and Proteins, 2018
Proteins are amphoteric polyelectrolytes, being capable of holding both positive and negative charges. The ionizable groups have a wide range of pK values, and so the charge distribution is sensitive to pH. When the net charge in aqueous solution is zero, the system is said to be isoelectric (pH = pI). (The pH of zero charge in the absence of any ions except H30+ and OH- is called the isoionic point.) For many proteins the isoelectric point is close to pH 5, but some have much lower values (e.g., pepsin) and some much higher (e.g., lysozyme).
Gelatin-based electrospun and lyophilized scaffolds with nano scale feature for bone tissue engineering application: review
Published in Journal of Biomaterials Science, Polymer Edition, 2022
Yogendra Pratap Singh, Sudip Dasgupta
Tropocollagen is the basic structural unit of collagen that is three polypeptide chains [87]. These three chains are coiled to produce a super-helical structure. Similarly, gelatin also possesses a triple-helix structure, and its surfaces exhibit polyampholytic properties. Type A gelatin exhibits isoinoic points from pH 6–9 while that for type B gelatin is expressed at pH 5. Of course, at lower pH than the corresponding isoionic point, gelatin shows a positively charged surface and at higher pH than that a negatively charged surface is exposed. The charge distribution pattern of gelatin (type A and B) in an aqueous solution of different pH is shown in Figure 7.