Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Specific Ion Effects of Trivalent Cations on the Structure and Charging
  State of $\beta$-Lactoglobulin Adsorption Layers   In this work, we addressed the effects of Y$^{3+}$ and Nd$^{3+}$ cations on
the adsorption of the whey protein $\beta$-lactoglobulin (BLG) at air-water
interfaces as a function of electrolyte concentration. Both cations caused very
similar but dramatic changes at the interface and in the bulk solution. Here,
measurements of the electropho-retic mobility and vibrational sum-frequency
generation spectroscopy (SFG) were applied and consistently showed a reversal
of the BLG net charge at remarkably low ion concentrations of 30 (bulk) and 40
(interface) $\mu$M of Y$^{3+}$ or Nd$^{3+}$ for a BLG concentration of 15
$\mu$M. SFG spectra of carboxylate stretching vibrations from Asp or Glu
residues of interfacial BLG showed significant changes in the carboxylate
stretching frequency, which we associate to specific and efficient bind-ing of
Y$^{3+}$ or Nd$^{3+}$ ions to the proteins carboxylate groups. Characteristic
reentrant condensation for BLG moieties with bound trivalent ions was found in
a broad concentration range around the point of zero net charge. The highest
colloidal stability of BLG was found for ion concentrations <20$\mu$M and
>50$\mu$M. Investigations on macroscopic foams from BLG solutions, revealed the
existence of structure-property relations between the interfacial charging
state and the foam stability. In fact, a minimum in foam stability at 20$\mu$M
ion concentration was found when the interfacial net charge was negligible. Our
results provide new information on the charge reversal at the liquid-gas
interface of protein/ion dispersions. Therefore, we see our findings as an
important step in the clarification of reentrant con-densation effects at
interfaces and their relevance to foam stability.

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The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
2
The categories of this paper are: math
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The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th