Kinetic and Structural Features of a Dyestuff Coaggregation Studied by Time-Resolved Static Light Scattering

Abstract

A binary dyestuff aggregate with a distinct stoichiometry is formed in dilute aqueous solution upon addition of Mg(2+) ions. The aggregation process was investigated with time-resolved multiangle static light scattering resulting in a sequence of static scattering curves. The scattering curves were analyzed with respect to the aggregation kinetics as well as the structure of the growing aggregates. The aggregation kinetics was based on the time evolution of the weight-averaged molar mass values extracted from the intercepts of the static scattering curves. A kinetic model that considers solely a nucleation step and monomer addition in its most simple form was developed in order to describe the evolution of time-dependent mass data. In addition, a kinetic model introduced by Lomakin et al. (Proc. Natl. Acad. Sci. U.S.A. 1996, 93, 1125) for the description of β-amyloid aggregation was adapted to the same experimental data. Application of the two kinetic models offered significant information on the role of magnesium ions within the aggregation process and provided a deeper understanding of the aggregation mechanism. Correlation of the size parameters extracted from the initial slopes of the scattering curves with the respective mass data as well as direct fitting of the scattering curves with the wormlike chain model yield a consistent set of model parameters.

Self‐Assembly of Pseudo‐Isocyanine Chloride as a Sensor for Macromolecular Crowding In Vitro and In Vivo

“…In order to make one step forward in classification of crowders, a few representative proteins like human islet amyloid polypeptide (IAPP), MET16, and Ab may be selected to be exposed systematically to different crowding agents. It is at this point where we would like to stress an analogy between proteins and synthetic dyestuffs as this analogy serves as an alternative starting point . Dyestuffs like proteins are organic molecules with usually a marginal solubility in water.…”

Coaggregation of Two Anionic Azo Dyestuffs: A Combined Static Light Scattering and Small-Angle X-ray Scattering Study

“…Provided that [A] tot is known and excluding the existence of seeds, the Lomakin model allocates five independent fitting parameters k n , k e , [A]*, p n , and p M . The dependence of the first three moments of the particle mass distribution on these parameters has been derived in the preceding article . The k th moment is defined as false[ normalB false] false( k false) = prefix∑ i i k [ B i ] where [B i ] is the molar concentration of aggregates B i with degree of polymerization i .…”

“…In several preceding papers, − we have identified a binary system of two azo dyestuffs which form aggregates in dilute aqueous solution on a time scale of minutes if magnesium ions are added. This property makes the respective dyestuff system an exceptionally interesting candidate for time-resolved investigation of aggregate formation by multiangle light scattering.…”

“…The kinetics of self-assembly of RD and YD in the presence of magnesium ions could be described by a short period of nucleation followed by an extended growth period. During the growth period, nucleation comes to a standstill and the generated fibers grow by a stepwise addition of small building units . The period of nucleation itself could not yet be directly investigated since the self-assembly experiments were initiated by the time-consuming hand mixing of dyestuff solution with alkaline earth solutions.…”

Quantitative investigations of thermal and photoinduced J- and H-aggregation of hydrophobic spirooxazines in binary solvent through UV/vis spectroscopy

“…A promising approach to this kinetic analysis of assembly formation could be the consideration of a series of equations involving stepwise monomer addition. 28 M + A i / A i+1 However, although simple, this assumption rapidly gives rise to awkward mathematics. Even, numerical integrations are challenging due to a parameter identication problem.…”