Volume 218, Issue 7

In this short review an introduction to the phenomenon of protein adsorption will be given. Protein adsorption often plays the central role in a wide variety of processes occurring in medicine, biochemistry, biotechnology and daily life. The main types of interactions ruling protein adsorption are summarized in this review and the principles of a few powerful experimental techniques to characterize protein adsorbates are outlined. Taking the silica/water interface as an example, the driving forces for protein adsorption are discussed on the basis of recent experimental results. Finally, the interactions of proteins with polyelectrolyte brushes are described. These brushes combine favourable properties of other interfaces and permit a controlled immobilization of protein molecules.

Understanding the structural aspects of aquo + organic mixtures and finding out a suitable physico-chemical parameter as a structural probe is of great importance from a theoretical and experimental point of view. Attempts have been made to derive useful relations regarding the structure of aquo + organic mixtures [ethylene glycol + water, glycerol + water, dioxane + water, acetone + water and acetonitrile + water mixtures] of widely divergent characteristics based on different macroscopic molecular properties: (i) excess thermodynamic properties of mixing, (ii) excess dielectric constants, (iii) excess polarizability volumes, (iii) correlation factor ‘ g ’, (v) ultrasonic sound absorption, (vi) basicity or other suitable expressions. The properties give valuable details regarding the structure of aquo + organic mixtures. Macroscopic molecular properties provide a summary of all interaction energies over a long time, but finer structural details may be available from microscopic properties (using relaxation techniques etc. ). A comparison of the macroscopic and microscopic methods for the determination of structural aspects of solvent systems is presented.

The inclusion complexation of Methyl Orange (MO) with β-cyclodextrin (β-CD) was studied spectrophotometrically in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF 4 ) which is a typical room-temperature ionic liquid. It was found that MO forms a 1:2 inclusion complex with β-CD in [bmim]BF 4 . A large association constant was obtained, suggesting a high degree of stability of the inclusion complex between MO and β-CD in [bmim]BF 4 . Based on the results, the inclusion behavior of β-CD in the ionic liquid was discussed.

A modelistic approach of the early stages of film formation and surface growth on tin electrodes at bicarbonate medium under dynamic conditions is presented. The modelistic treatment was applied to both anodic and cathodic processes. In order to organise the paper, the potential interval of interest was divided into two potential windows, each one involving one of the anodic peaks and their corresponding cathodic counterparts. The Müller–Calandra model (also known as the layer-pore resistance model) was considered suitable to interpret the film growth processes occurring during the positive scan. A derivation of the former, developed by Devilliers et al. , which take into account the conductive electrical nature of the surface compound, was applied to explain the reduction of the film formed within the first potential window. On the other hand, it was verified that the use of a simple model to interpret the cathodic process occurring at the second potential window was not possible due to the complex nature of the process. In this case, a mixed control kinetics was proposed and the current was considered as the sum of two contributions. In order to complement the description and specially to determine the role of diffusion and mass transport in film formation, rotating disk measurements were also carried out.

Ultrasonic velocity ( u ) and density ( ρ ) of the binary mixtures of acetonitrile (AN) with nitromethane (NM) and dimethylsulfoxide (DMSO) as well as of the solutions of Bu 4 NBPh 4 , Bu 4 NClO 4 , [Cu(CH 3 CN) 4 ]ClO 4 , [Cu(Phen) 2 ]ClO 4 , [Cu(DMPhen) 2 ]ClO 4 and [Cu((NH 2 ) 2 CS) 4 ]ClO 4 have been measured over the entire composition range at 298.15 K. Using these data, isentropic compressibilities ( K s ) and apparent molal isentropic compressibilities ( K s, ϕ ) for various salts have been calculated and used for the evaluation of limiting apparent molal isentropic compressibilities ( K s, ϕ 0 ). The K s, ϕ 0 values of various salts have been split into the contribution of individual ions ( K s, ϕ 0 ) ± . The ( K s, ϕ 0 ) ± values for all copper (I) cations [Cu(CH 3 CN) 4 ] + , [Cu(Phen) 2 ] + , [Cu(DMPhen) 2 ] + and [Cu((NH 2 ) 2 CS) 4 ] + are negative and large, for Bu 4 N + and Ph 4 B − are positive and large at all compositions in both AN + NM and AN + DMSO mixtures but for ClO 4 − are negative in AN + DMSO mixtures and positive in AN + NM mixtures. The variation of ( K s, ϕ 0 ) ± values with solvent composition indicates that both DMSO and NM interact with complex copper (I) cations forming complex ions of the type [Cu(CH 3 CN) 4 − x (S) x ] + ( x = 1–4 and S = co-solvent) and [Cu(ligand) 2 ] + (CH 3 CN) y (S) z in which AN is systematically replaced by the co-solvents. DMSO interacts more strongly with complex copper (I) cations and ClO 4 − ion as compared to NM. Bu 4 N + and Ph 4 B − show some special interaction with AN which decreases with the increase of NM or DMSO composition in the mixture.

The object of the following is the change from Lagrange line integrals of single particles to Lagrange line integrals of systems of particles under the condition of the first law. The first problem is the historical variational principle as imagined by Bernoulli, whereas the second problem concerns the built up of thermodynamic systems from elementary integrals. Since thermodynamics disregards mechanisms governing the connection or the interaction of particles the built up of thermodynamic systems is possible if Lagrange integrals exhibiting addition theorems between the limits are taken into account. Hilbert’s Independence Theorem involving the transition from the Lagrange to the Hamilton potential proved to be a suitable method to turn over from the mathematical Lagrange potentials to the Hamilton representation as used in physics. Caratheodory, basing his “Complete Figures of Calculus of Variation” on Hilberts conception has given the variational principle that minimizes the connection of the elementary Lagrange integrals being connected between the limits. The extension of thermodynamics to integrals composed from components showing a connection between the limits yields important thermodynamic properties.

Complex-containing solutions such as H 2 O–NaCl–CdCl 2 always strongly deviate from ideality and the non-ideality often increases with the complex former concentrations. Here we report isopiestic measurements of the H 2 O–NaCl–CdCl 2 –mannitol–sorbitol quinary solution equilibrated with the 2NaCl · CdCl 2 · 3H 2 O solid complex at 25 °C, which show a linear relation between mannitol and sorbitol molalities, similar to that for the H 2 O–mannitol–sorbitol ternary solution. The reason for the ideal-like behavior of the quinary solution is that the saturated complex 2NaCl · CdCl 2 · 3H 2 O has the similar effects as the isopiestic water on the unsaturated solutes mannitol and sorbitol and that the interaction between the isomers mannitol and sorbitol is negligible.

From extraction experiments with 22 Na as a tracer, the extraction constant corresponding to the equilibrium Na + (aq) + A − (aq) + L(nb) ⇔ NaL + (nb) + A − (nb) taking place in the two-phase water–nitrobenzene system (A − = picrate, L = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K ex (NaL + ,A − ) = 1.9±0.1. Further, the stability constant of the dibenzo-21-crown-7-sodium complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C log β nb (NaL + ) = 7.1±0.1.