Network forming properties of various proteins adsorbed at the air/water interface in relation to foam stability

A series of proteins was studied with respect to their ability to form a network at the air/water interface and their suitability as foaming agents and foam stabilizers. Proteins were chosen with a range of structures from flexible to rigid/globular: beta-casein, beta-lactoglobulin, ovalbumin, and (soy) glycinin. Experiments were performed at neutral pH except for glycinin, which was studied at both pH 3 and pH 6.7. The adsorption process was followed with an automated drop tensiometer (ADT). Network forming properties were assessed in terms of surface dilational modulus (determined with the ADT), the critical falling film length (L(still)) and flow rate (Q(still)) below which a stagnant film exists (as measured with the overflowing cylinder technique), and the fracture stress and fracture strain measured in surface shear. It was found that glycinin (pH 3) can form an interfacial gel in a very short time, whereas beta-casein has very poor network-forming properties. Hardly any foam could be produced at the chosen conditions with glycinin (pH 6.7) and with ovalbumin, whereas beta-casein, beta-lactoglobulin, and glycinin (pH 3) were good foaming agents. It seems that adsorption and unfolding rate are most important for foam formation. Once the foam is formed, a rigid network might favor stabilizing the foam.     

Planar nets of Ti atoms comprising squares and rhombs in the new binary antimonide Ti2Sb

The new binary antimonide Ti(2)Sb was found to crystallize in a distorted variant of the La(2)Sb type, which contains a square planar La net with short La-La bonds. In the Ti(2)Sb structure, the corresponding Ti net is deformed to squares and rhombs in order to enhance Ti-Ti bonding, as proven by single-crystal X-ray investigation in combination with the real-space pair distribution function technique utilizing both X-ray and neutron powder diffraction data. Electronic structure calculations revealed a lowering of the total energy caused by the disorder, the major driving force being strengthened Ti-Ti interactions along the diagonal of the Ti(4) rhombs.     

Darstellung von Pentahalogenopyridinosmaten(IV) in unpolaren Lösungsmitteln

Preparation of Pentahalopyridineosmates(IV) in Nonpolar Solvents The reaction of hexahaloosmates(IV) with pyridine in nonpolar solvents gives pentahalopyridineosmates(IV) in good yield. Using this method [OsI₅py]^? is prepared for the first time. It could not be obtained by substitution reactions or photolysis of [OsI₆]^2? in pyridine. The new complex is characterized by electronic and vibrational spectroscopy.     

Regioselective Arene Functionalization: Simple Substitution of Carboxylate by Alkyl Groups

Arenes with various alkyl side‐chains were synthesized in high yields and excellent regioselectivities. Starting from toluic and naphthoic acids, the carboxylate group was conveniently substituted by alkyl halides by Birch reduction and subsequent decarbonylation. The method is characterized by inexpensive starting materials and reagents, and methylation of arenes was realized. Besides simple alkyl substituents, the scope of arene functionalization was extended by benzyl, fluoro, amino, and ester groups. We were able to control the alkylation of 1‐naphthoic acid during Birch reduction by the addition of tert‐butanol. This allowed the regioselective synthesis of mono and bis‐substituted naphthalenes from the same starting material.