Viruses as building blocks for materials and devices

From the viewpoint of a materials scientist, viruses can be regarded as organic nanoparticles. They are composed of a small number of different (bio)polymers: proteins and nucleic acids. Many viruses are enveloped in a lipid membrane and all viruses do not have a metabolism of their own, but rather use the metabolic machinery of a living cell for their replication. Their surface carries specific tools designed to cross the barriers of their host cells. The size and shape of viruses, and the number and nature of the functional groups on their surface, is precisely defined. As such, viruses are commonly used in materials science as scaffolds for covalently linked surface modifications. A particular quality of viruses is that they can be tailored by directed evolution by taking advantage of their inbuilt colocalization of geno- and phenotypes. The powerful techniques developed by life sciences are becoming the basis of engineering approaches towards nanomaterials, opening a wide range of applications far beyond biology and medicine.     

Interaction forces between cellulose microspheres and ultrathin cellulose films monitored by colloidal probe microscopy-effect of wet strength agents

Colloidal probe microscopy was employed to study forces between cellulose surfaces upon addition of a series of cationic copolymers in aqueous solution, as model compounds for wet strength agents. The content of quaternary ammonium groups and primary amines was systematically varied in the cationic polymers, to distinguish between the importance of electrostatical and H-bonding effects. Cellulose microspheres were glued at the apex of tipless microfabricated cantilevers and used as colloidal probes. Ultra thin cellulose films and cellulose fibres were employed as model surfaces. The cellulose films of a thickness of about 5 nm were spin-coated from cellulose solution onto silicon substrates. The root-mean-square-roughness (RMS) was 0.3-0.8 nm. The cationic model polymers were compared to Servamine, a polymer employed as standard wet strength resin in papermaking industries. Force versus separation measurements showed a detailed picture of adhesion and contact breaking. Relatively strong adhesion of the order of 0.3 mJ/m(2) was observed with Servamine within a range of approximately 10 nm. At larger distances weak bond breaking and elastic chain pulling were identified. When approaching the surface one to two small jump-in's possibly related to strong binding of Servamine and subsequent attraction could be found in the case of Servamine. In contrast, all the model copolymers showed only a weak adhesion of 8-30 micro/m(2), i.e., an order of magnitude less than that of Servamine and subsequent elastic rupture domains. The contour length, persistence length and characteristic rupture distances were calculated by means of applying the WLC model. Measurements against cellulose fibres obtained from the production process proved the relevance of the model systems.     

New Diaza- and Thiazadiphosphetidines from the Dithiophosphoric Acid Chloride Betaine and Primary Amines via Monometaphosphate Analogous Intermediates

Abstract

Under definite conditions the dithiophosphoric acid chloride pyrididium betaine reacts with primary amines, RNH₂, yielding four-membered rings. Depending on the electronic properties of R either diaza or thiazadiphosphetines are formed. An elimination-addition mechanism via imido dithiomonometaphosphate is discussed.     

Electric potential distributions around discrete charges in a dielectric membrane—electrolyte solution system

Within the framework of the linearized Debye-Hückel theory an exact solution of the problem of calculating the electric potential caused by discrete fixed charges located at arbitrary positions with respect to a dielectric membrane-solution interface is presented. It takes into account the existence of an electrolyte solution on both sides of the membrane. Asymmetric ionic conditions are allowed for. For some interesting typical cases of fixed charge locations and electrolyte ionic strengths electric potential distributions were calculated and discussed. It is shown that, if the fixed charges were at or in front of the membrane surface, the characteristic distance of the electric potential decay was comparable to the Debye-Hückel length. At the opposite membrane surface only very small electric potentials can be observed. If, however, the fixed charge was placed below the membrane surface the electric potential in lateral direction and towards the other membrane surface largely increased. This effect was very sensitive to the position of the fixed charge with respect to the membrane surface.     

Darstellung und Reaktionsverhalten von 2,2-Dithio-phosphol-und -phosphorinan-Derivaten

Synthesis and Reactions Behavior of 2,2-Dithiophospholes and 2,2-Dithiophosphorinanes Reaction of dithiophosphoric acid chloride betaine 1 with bifunctional compounds opens a new way for preparing five- or six-membered cyclic dithiophosphates ( 2a – i, 3, 5a – f ). Synthesis, spectroscopic properties, and some reactions of these compounds are reported. Reaction of the cyclic dithiophosphates with alkyl halides yields the corresponding S-alkylesters 6a – o .     

Opportunities for Particles and Particle Suspensions to Experience Enhanced Transport in Porous Media: A Review

Transport in Porous Media - The possibility of broaching, or the release of fluids at the seafloor due to a damaged or faulty well, is a hazard that must be assessed in the well permitting process....     

Formation of Some New Four-Memberd Phosphorus-Nitrogen and Phosphorus-Nitrogen-Sulfur Ring Systems

Abstract

Continuing the study on the course of reaction of Py·PS₂Cl with primary amines we have found a method to prepare the hitherto unknown tetrathio-substituted phosphetidine compounds 1 and 2. Primary amines react with Py·PS₂Cl in a molar ratio of 1:l in the presence of a base either to diazaphosphetidines 1 or to azathiaphosphetidines 2 according to equation (1):     

Eine Methode zur Trennung des Zinnoxyds von der Wolframs?ure

Ohne Zusammenfassung